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Intensive and Critical Care Nursing (2014) xxx, xxx—xxx
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Effects of fever on haemodynamic parameters in neurosurgical intensive care unit patients Hossein Asgar Pour a,∗, Meryem Yavuz b,1 a b
Department of Surgical Nursing, Aydin Health School, Adnan Menderes University, Aydin, Turkey Department of Surgical Nursing, School of Nursing, Ege University, Izmir, Turkey
Accepted 9 July 2014
KEYWORDS Fever; Haemodynamic parameters; Neurosurgical intensive care unit
∗ 1
Summary Objective: To investigate the effects of fever on the haemodynamic parameters (pulse rate, arterial oxygen saturation, systolic blood pressure, diastolic blood pressure and mean arterial blood pressure) of patients in a neurosurgical intensive care unit. Design: A prospective, repeated-measures study. Methods: This study was performed in the neurosurgical intensive care unit of a University Hospital in the West of Turkey. The research sample included all patients with at least two occurrences of fever in the postoperative period. Body temperature and haemodynamic parameters of patients were measured on admission, one hour before the onset of fever and during fever (peak temperature). Results: Increase of body temperature during fever episodes was followed by a significant increase in pulse rate (p = 0.001) with significant decreases in systolic blood pressure (p = 0.002) and arterial oxygen saturation (p = 0.001). Furthermore fever episodes were followed by a nonsignificant increase in diastolic blood pressure (p = 0.074) and a non-significant decrease in mean arterial blood pressure (p = 0.097). In this study, a degree celsius (1 ◦ C) increase in body temperature, was associated with a decline of 4.43 mmHg in systolic blood pressure, 0.166 mmHg mean arterial blood pressure and 0.64% arterial oxygen saturation, respectively. It was also associated with an increase of 1.61 mmHg in diastolic arterial blood pressure and 7.46 beats/per minute pulse rate, respectively. Conclusions: The findings from this research have demonstrated the effects that fever can have on haemodynamic parameters of patients in one neurosurgical intensive care unit. Hence the study highlights the importance for intensive care unit (ICU) nurses to appreciate the
Corresponding author. Tel.: +90 256 213 88 66; fax: +90 256 212 42 19. E-mail addresses: [email protected] (H. Asgar Pour), [email protected] (M. Yavuz). Tel.: +90 232 388 11 03; fax: +90 232 388 63 74.
http://dx.doi.org/10.1016/j.iccn.2014.07.001 0964-3397/© 2014 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Asgar Pour H, Yavuz M. Effects of fever on haemodynamic parameters in neurosurgical intensive care unit patients. Intensive Crit Care Nurs (2014), http://dx.doi.org/10.1016/j.iccn.2014.07.001
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H. Asgar Pour, M. Yavuz physiological effects of fever which have the potential to cause complications in febrile patients. Increasing knowledge about the effects of fever on haemodynamic parameters can therefore be of benefit to nurses in terms of quality and efficacy of patient care. © 2014 Elsevier Ltd. All rights reserved.
Implications for Clinical Practice • This study provides data concerning the effect of fever on haemodynamic parameters, relationships between them and, nursing actions related to these changes. Information about accurate and careful measurements of body temperature and haemodynamic parameters play an important role in the prevention of complications during fever among patients in neurosurgical ICU settings. • Neurosurgical intensive care unit staff, particularly during postoperative care, should be proactive in ensuring that they have a formal, evidence-based management plan for management of fever that conforms to the relevant clinical guidelines and integrates multidisciplinary care. • An increase in resources for professional development in the assessment and management of fever is essential for improving and maintaining the skills of staff during and after care.
Introduction Monitoring and evaluating haemodynamic parameters (systolic blood pressure, diastolic blood pressure, mean arterial blood pressure, pulse rate, and arterial oxygen saturation) are essential nursing assessment measures, particularly for patients in intensive care settings (Basoglu et al., 2000; Erdal, 2005; Karadakovan and Eti Aslan, 2012). In addition pulse, body temperature, arterial blood pressure, respiration and pain are basic vital signs and indicators of an individual’s health status. Changes in physiological functions are reflected in the values of an individual’s basic vital signs, consequently deviations from the normal values can indicate disruption of homeostasis (Akinci, 2003; Celik et al., 2011). Therefore assessing vital signs is an effective method for monitoring health status and is essential for accurate diagnosis and delivery of appropriate nursing interventions (Asgari and Soleymani, 2009; Giuffre et al., 1990; Schutz, 2001). The diagnostic value of standard monitoring parameters is high when these values are abnormal, as they are considered sensitive indices of the overall health of patients (Dicle and Istan, 2002; Heydari, 2000; Kanan, 2004; Kiekkas et al., 2007). Whilst measuring and monitoring vital signs are basic nursing skills, nurses also need to know how variations in vital signs affect haemodynamic parameters of patients, relationships between these parameters and, appropriate nursing and multi-disciplinary follow-up that might be required (Ahmadi and Mohammadi, 2003; Asgarpour and Yavuz, 2010; Heydari, 2000; Pahsa, 2009). Fever is an adaptive response to a variety of infectious, inflammatory foreign stimuli. The febrile response confers an immunological advantage to the host over invading microorganisms (Kothari and Karnad, 2005; Laws and Jallo, 2010). Fever results from a cytokine-mediated reaction that results in the generation of acute phase reactants and controlled elevation of body temperature. Fever is defined as an increase in core body temperature ≥38.3 ◦ C (≥101 ◦ F) attributed to the upregulation of the thermostatic setpoint,
which is controlled by the hypothalamus (Heydari, 2000; Jonathan et al., 2009; Kiekkas et al., 2007; Kothari and Karnad, 2005; Laws and Jallo, 2010; Naomi et al., 2008; Willke et al., 2002). Fever is present in 29—36% of all hospitalised patients (Celik et al., 2011; Ferguson, 2007), although the incidence of fever ranges between 28% and 75% in critically ill patients (Celik et al., 2011; Henker et al., 2001; Kiekkas et al., 2007). Fever can result from both infectious and non-infectious causes (Ballestas, 2007; Celik et al., 2011; Cunha, 2013; Kiekkas et al., 2007; Laupland, 2009; Ryan and Levy, 2003; Steven et al., 2008) and febrile episodes occur in roughly 50% of patients in the NICU with neurocritical patients having a slightly lower frequency of fever, approximately 23%, 6 than patients in the neurosurgical ICU, approximately 47% (Laws and Jallo, 2010). Fever is more often an indicator of infection, however in ICU patients, pulmonary embolism, gastrointestinal bleeding, drug reactions, cardiac problems, trauma, surgery, and intracranial bleeding are also associated with fever (Axelrod and Diringer, 2008; Celik et al., 2011; Henker et al., 2001; Jonathan et al., 2009). Fever symptoms among the neurocritical and neurosurgical patient populations predominate with vascular injuries, such as intracerebral haemorrhage and subarachnoid haemorrhage (Laws and Jallo, 2010; Polderman, 2008). According to Laws and Jallo (2010) the highest rates of febrile episodes occur in patients diagnosed with subarachnoid haemorrhage (65%), followed by traumatic brain injury (40%) and then intracranial haemorrhage (31%). Where no cause of fever was identified (in 28% of patients), the authors suggested a fever of central origin. As the body temperature rises, important physiological changes occur (Henker et al., 2001; Kiekkas et al., 2008). A body temperature increase from 37 ◦ C to 39 ◦ C has been found to be followed by a 25% increase of oxygen consumption and energy expenditure in ICU patients (Kiekkas et al., 2007; Kothari and Karnad, 2005). These increases in the metabolic rate and serum levels of stress hormones are suggested to subsequently increase heart rate
Please cite this article in press as: Asgar Pour H, Yavuz M. Effects of fever on haemodynamic parameters in neurosurgical intensive care unit patients. Intensive Crit Care Nurs (2014), http://dx.doi.org/10.1016/j.iccn.2014.07.001
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Effects of fever on haemodynamic parameters
Methods Objective The aim of study was to investigate the effects of fever on the haemodynamic parameters (systolic blood pressure, diastolic blood pressure, mean arterial blood pressure, pulse rate and arterial oxygen saturation) of patients in one neurosurgical intensive care unit of a university hospital in the west of Turkey.
Setting This prospective, repeated-measures study was conducted between June 2009 and May 2010 at the Neurosurgical Intensive Care Unit of Ege University Hospital Izmir, Turkey.
Ethical approval This study was approved by Ege University Institutional Review Board. Written and verbal informed consent was obtained from all conscious patients or patients’ relatives (in semi-conscious or unconscious patients) after explaining the aims and protocol of the study. Written approvals were obtained from the Ege University Institute of Health Sciences (March, 2009), Ethics Board of the Ege University School of Nursing (May, 2009), the Ege University Hospital, and Neurosurgical Department Chief Physician (June, 2009) and Directorate of Nursing Services of Ege University Hospital (June, 2009).
Participants The inclusion criteria were as follows: 1- Voluntary participation in the study, 2- No incidence of fever in the preoperative period and during surgery, 3- At least two episodes of fever in the postoperative period,
N vs Power with Mean0=0,00000 Mean1=0,24143 S=0,20018 Alpha=0,05 WC (N) 30 25 20
N
and arterial blood pressure in febrile patients (Asgarpour and Yavuz, 2010; Kiekkas et al., 2007). Conversely, body temperature increases may result in hypotension due to myocardial depression and vasodilation, especially in the veins of the kidneys, liver, skin, upper and lower limbs (Asgari and Soleymani, 2009; Cooper, 1994; Heydari, 2000; Kiekkas et al., 2007). It is important for neurosurgical ICU nurses to appreciate the physiological effects of fever, which can cause complications in febrile patients in these settings (Celik et al., 2011). Furthermore accurate and careful monitoring of haemodynamic parameters during neurosurgical ICU patients’ febrile episodes can be helpful to determine the process of fever treatment. There are not enough studies related on fever and changes in haemodynamic parameters, i.e., arterial blood pressure, pulse rate, and arterial oxygen saturation (Asgarpour and Yavuz, 2010; Kiekkas et al., 2007). In this study, the effects of fever on the haemodynamic parameters of patients in one neurosurgical intensive care unit in Turkey will be investigated.
3
15 10 5 0 0.70
0.75
0.80
0.85
0.90
0.95
1.00
Power
Figure 1
Numeric results for Wilcoxon test.
4- Surgery occurred at least four hours’ prior to enrollment. The results of a power analysis, with power set at 0.99, suggested that a selection of 20 patients were sufficient for the sample (Fig. 1). The total research sample comprised of 35 patients who met the inclusion criteria. In the present study, for all patients (n = 364) who were admitted to the neurosurgical ICU in the post-operative period, 49 of the patients were eligible for enrollment in the first stage of sampling. In the second stage of sampling, 14 of 49 patients who were selected in the first stage did not enter into the second stage of the study. Patients who died/did not exhibit body temperature increase more than once and patients with body temperature over ≥40 ◦ C/requiring antipyretic agents treatment were excluded. Therefore, 35 of 49 patients were selected (Fig. 2).
Data collection In the present study, body temperature was measured by the axilla mercury-glass thermometer; by the tympanic membrane commercial infrared tympanic thermometer (Felix, Thermo-Scan Thermometer 952) and, by the haemodynamic parameters non-invasive monitoring system (Bruker TMSN — 910CD/Ni12v 1.9 Ah). For measurement of body temperature on admission to the neurosurgical ICU, the axilla method was used (in admission to the NICU the axilla method was used for measurement of BT because of the risk for trauma in external ear or the presence of earwax which could incur incorrect results). For measurement of body temperature one hour before the onset of fever (when body temperature was 36.7, BT and haemodynamic parameters were measured per 15 minutes until fever was appeared) and during fever, the tympanic membrane method was used (in the post-operative period for correction results the body temperature was measured by the tympanic membrane method). The following derived regression equation was used for the adjustment of axillary temperature values to tympanic membrane temperature ones: Tympanic membrane temperature (◦ C) = 0.889 + 0.982 × axillary temperature (◦ C) (Kiekkas et al., 2007). The tympanic membrane temperature reflects the temperature of the hypothalamus and thus, the core body temperature (Naomi et al., 2008). In a study conducted by
Please cite this article in press as: Asgar Pour H, Yavuz M. Effects of fever on haemodynamic parameters in neurosurgical intensive care unit patients. Intensive Crit Care Nurs (2014), http://dx.doi.org/10.1016/j.iccn.2014.07.001
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H. Asgar Pour, M. Yavuz The number of operaons in the neurosurgery operaon room during the study (n = 1527).
The number of paents in the neurosurgery intensive care unit in the postoperave period (n=364)
Paents who did not enter the second stage of the study (n = 14): Paents with appropriate criteria in the first stage of the study (n = 49).
- Paents who died/did not exhibit body temperature increase more than once (n = 6). - Paents with body temperature over ≥ 40°C /requiring anpyrec agents treatment (n = 3). Lacking the iniaves at the appropriate me by researchers (n=5).
The number of samples taken for analysis (n = 35).
Figure 2
The stages of sample selection.
Mariak et al. (2003) during neurosurgical operations, brain temperature fluctuations of patients with an open cranium were followed closely by changes in tympanic membrane temperature, but not by oesophageal temperature. The results of a further study by Rampen et al. (2005) support the use of tympanic membrane temperature as an extracranial estimate of intracranial temperatures. Furthermore, tympanic membrane temperature measurement is easier, faster and less invasive than other measurements (Kiekkas et al., 2007). In the study conducted by Klein et al. (1993) tympanic membrane temperature was shown to be strongly correlated with pulmonary artery temperature, thus it was considered to properly represent core body temperature (Klein et al., 1993). In the present study fever was defined as an increase of body temperature ≥38.3 ◦ C (Asgarpour and Yavuz, 2010; Kiekkas et al., 2007). Body temperature and haemodynamic parameters were measured and recorded at admission and at one hour intervals on the neurosurgical ICU daily chart. During the postoperative period body temperature and haemodynamic parameters were measured every 15 minutes when the body temperature reached >37.6 ◦ C. Body temperature and haemodynamic parameters were measured again when fever (BT ≥ 38.3 ◦ C) manifested. During fever, the highest temperature (peak temperature) was the value measured just prior to peripheral cold application. The authors determined three time points (at admission, one hour before the onset of fever and during fever) for comparison changes of haemodynamic parameters during febrile episodes.
Validity and reliability To standardise the mercury-glass thermometers, thermometers were placed in 38 ◦ C water for two minutes, and those showing the appropriate temperature at the end of this
period were used. Furthermore, to measure body temperature via the tympanic membrane, external ears of patients in the sample were evaluated for signs of wounds and trauma. A tympanic thermometer was then inserted in the external ear and measurements were performed using both ears (Ilce and Karabay, 2009). Haemodynamic Standard Monitoring systems calibrated three times (once before and twice during the research) by an external company, and measurements were performed after control measurements by the responsible company.
Data analysis Data analysis was performed by the University Biostatistics and Medical Informatics Main Field of Study by using SPSS version 16.0 (Statistics for Social Sciences) for the Windows statistics programme. Data analyses were performed for all participants who completed the study (N = 35). Friedman and Wilcoxon Signed Ranks Tests were used to check the normality of distribution of continuous variables. Data are presented as means and standard deviations. Age of patients, operation time and temperature of NICU were analysed by percentages, means and standard deviation. To compare standard monitoring parameters between admission, one hour before the onset of fever episodes and during fever episodes (peak temperature), paired samples t-tests were used. Statistical significance was set at p < 0.05.
Results Normally distributed continuous variables are presented as mean ± standard deviation. Thirty-five patients with at least two episodes of increased body temperature were included in this study. The mean age of patients was 49.71 ± 17.65 years, and 62.9% patients were men. In relation to disease diagnosis, 68.6% patients had suffered a brain haemorrhage,
Please cite this article in press as: Asgar Pour H, Yavuz M. Effects of fever on haemodynamic parameters in neurosurgical intensive care unit patients. Intensive Crit Care Nurs (2014), http://dx.doi.org/10.1016/j.iccn.2014.07.001
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Effects of fever on haemodynamic parameters
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Table 1 Mean pulse rate, O2 Sat, systolic blood pressure, diastolic blood pressure and MAP of patients at admission and 1 h before the onset of fever episode.
Pulse ratea O2 Satb Systolic blood pressurec Diastolic blood pressurec MAPc a b c
At admission
1 h before the onset of fever
p value
89.8 ± 17.8 96.4 ± 2.3 135.2 ± 27.5
93.4 ± 17.6 96.01 ± 2.11 132.9 ± 14.5
p = 0.383 p = 0.433 p = 0.678
79.1 ± 19.3
77.2 ± 11.6
p = 0.610
97.8 ± 21.2
95.7 ± 12.02
p = 0.624
B/PM = beats/per minute. %. mmHg.
28.6% brain tumour, 2.8 brain abscess, and the mean operation time was 3.85 ± 0.68 hours. In addition 31.4% patients had hypertension and 5.7% had diabetes mellitus. Fever appeared in 51.4% patients after the third day of operation and the mean magnitude of fever was 38.51 ◦ C. During fever, 62.9% patients were semi-conscious and 54.2% exhibited no signs of infections. Furthermore 34.2% of patients had central venous lines, 100.0% had Foley catheters inserted and 22.9% had brain catheters inserted for monitoring intracerebral pressure. In addition 77.2% of patients received supportive oxygen by different methods (37.03% by tracheostomy, 33.3% intubation, 29.6% by mask/nasal prongs) with FiO2 between 24 and 40% during fever episodes. No patients received antipyretic agents during fever episodes, though 33.3% of patients were sedated and 2.8% of patients received inotropic agents. The mean body temperature at admission, one hour before the onset of fever and during fever was 37.30, 37.37, and 38.51 ◦ C, respectively. Furthermore, the average temperature of the intensive care unit was 24.3 ± 1.32 ◦ C. Between admission and one hour before the onset of fever episodes, pulse rates of patients demonstrated a nonsignificant increase (p > 0.05), whilst O2 Sat, systolic blood pressure, diastolic blood pressure and MAP (mean arterial blood pressure) demonstrated a non-significant decrease, respectively (p > 0.05) (Table 1). Between one hour before the onset of fever and during fever episodes, pulse rates of patients demonstrated a significant increase (p < 0.05), whereas diastolic blood pressure demonstrated a non-significant increase (p > 0.05). At the same time O2 Sat and systolic blood pressure demonstrated a significant decrease (p < 0.05) and MAP, a non-significant decrease, respectively (p > 0.05) (Table 2). In this study, during fever, the pulse rate 8.528 ± 4.42 beats/per minute and diastolic blood pressure 1.842 ± 6.9 mmHg increased respectively. Furthermore, systolic blood pressure 5.07 ± 7.89 mmHg, mean arterial blood pressure 0.191 ± 6.00 mmHg and arterial oxygen saturation 0.742 ± 0.97% decreased respectively. According to the results of this study, a one degree celsius (1 ◦ C) increase in body temperature, was associated with a decline of
Table 2 Mean pulse rate, O2 Sat, systolic blood pressure, diastolic blood pressure and MAP of patients at 1 h before the onset of fever and during fever episode.
Pulse rate O2 Sat Systolic blood pressure Diastolic blood pressure MAP
1 h before the onset of fever
During fever
p value
93.4 ± 17.6 96.01 ± 2.11 132.9 ± 14.5
102.0 ± 20.8 95.2 ± 2.7 127.8 ± 15.7
p = 0.001 p = 0.001 p = 0.002
77.2 ± 11.6
79.1 ± 12.5
p = 0.074
95.7 ± 12.02
95.1 ± 12.7
p = 0.973
4.43 mmHg in systolic blood pressure, 0.166 mmHg mean arterial blood pressure and 0.64% arterial oxygen saturation and, an increase of 1.61 mmHg in diastolic arterial blood pressure and 7.46 beats/per minute pulse rate.
Discussion The variables investigated in this study, body temperature and haemodynamic parameters, were measured every 15 minutes to determine peak temperature when a patient’s body temperature reached >37.6 ◦ C in the postoperative period. Therefore the authors concluded that peak temperature measurements of fever episodes which were used were close to true peak temperatures. Standard monitoring of neurosurgical ICU patients includes the observation of electrocardiogram, heart rate, arterial blood pressure, and arterial oxygen saturation (Asgarpour and Yavuz, 2010; Heydari, 2000). The diagnostic value of monitoring standard parameters is very important, as these are considered sensitive indicators of the overall health of patients (Asgarpour and Yavuz, 2010; Heydari, 2000; Kiekkas et al., 2007). Neurosurgical ICU patients have life threatening conditions or injuries for which they have had surgery, invasive monitoring and other procedures, all of which can compromise their host defences (Laws and Jallo, 2010). It has been noted that febrile episodes occur from both infectious and non-infectious causes in neurosurgical ICU patients (Kothari and Karnad, 2005; Laws and Jallo, 2010). About 50% of fevers in the ICU are due to infectious causes (Kothari and Karnad, 2005). Staphylococcus aureus causes 25% of health care-related infection and the source of many of these infections is thought to originate from the patients’ endogenous flora (Perl, 2003). In the present study 13.4% of all patients in the postoperative period presented with a fever. Of these patients 20.2% had bacteriological confirmation of infection, 8.6% of which were from methicillin-resistant Staphylococcus aureus (MRSA) and S. aureus. This suggests that these were health care- related infections. In O’Shea et al.’s (N = 73) to determine infections in neurosurgical ICU patients, 28.8% of patients developed infection and the responsible organisms included pseudomonas, acinetobacter, E. coli, enterobacter, klebsiella, S. aureus and MRSA (O’Shea et al., 2004). In Erman et al.’s
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(2005) study to determine risk factors for surgical site infections in neurosurgery patients (N = 503), 6.2% of patients developed infection. The predominantly isolated microorganisms in patients were S. aureus (71.0%), acinetobacter baumanii (16.1%), and Staphylococcus epidermidis (12.9%) (Erman et al., 2005). The results of Sturm’s with neurosurgical patients’ related to surgical site infection showed that the majority (65%) of micro-organisms in craniotomy wounds were gram-positive. A study by Celik et al. on surgical ICU patients (neurosurgery 54.7%, anaesthesia 26.4%, general 17% and sub-specialty surgery 1.9%) with fever (N = 53), showed that the majority of patients had an infectious cause for their fever, with acinetobacter and pseudomonas infections isolated in the majority of these febrile patients. Celik et al. described acinetobacter and pseudomonas as the most common causes of nosocomial pneumonia, urinary tract and catheter-related infections in ICU patients (Celik et al., 2011). In the present study fever episodes were followed by a significant increase in heart rate, a significant decrease of systolic arterial blood pressure, a non-significant increase of diastolic arterial blood pressure and a non-significant decrease of mean arterial blood pressure. These findings suggest the adverse effects of fever on cardiac performance, decreased mean arterial blood pressure and increased heart rate during febrile episodes. Although increases in heart rate during the febrile state is associated with decreased of mean arterial blood pressure, the tachycardia response indicated failure to maintain effective cardiac output. During fever episodes, increases in the metabolic rate and serum levels of cortisol and norepinephrine hormones are thought to subsequently increase the pulse rate and arterial blood pressure (Kiekkas et al., 2007, 2008). Increases of oxygen consumption and energy expenditure also occur during fever, thus increases in the metabolic rate and serum levels of stress hormones are suggested to subsequently increase heart rate (Cooper, 1994; Kiekkas et al., 2007). Body temperature increases may result in hypotension due to myocardial depression and vasodilation (Dalal and Zhukovsky, 2006; Kiekkas et al., 2007; Pahsa, 2009). A possible explanation is that arterial blood pressure tends to increase due to metabolic rate increase and catecholamine secretion and to decrease due to vasodilation and myocardial depression (Ferguson, 2007; Marik, 2000). In the present study fever was followed by a significant decrease of arterial oxygen saturation, which is defined by the oxyhaemoglobin dissociation curve: when the body temperature increases, this curve is shifted rightward. This means that, for a given value of partial pressure of oxygen in arterial blood, the arterial oxygen saturation value decreases (Bacher, 2005). An increase in metabolic rate is followed by an oxygen consumption increase, which may result in a decrease of oxygen partial pressure in arterial blood. This is especially so for patients with a disrupted compensatory ability against increased metabolic demand (neurosurgical and neurological patients), such as patients with sepsis (Laws and Jallo, 2010). Subsequent increases in oxygen consumption, respiratory rate and cardiac output add a considerable burden to these patients, who may be unable to compensate for the increased metabolic demand (Bacher, 2005; Asgarpour and Yavuz, 2010; Steven et al., 2008).
In our study, a degree celsius (1 ◦ C) increase in body temperature, was associated with a decline of 4.43 mmHg in systolic blood pressure, 0.166 mmHg mean arterial blood pressure and 0.64% arterial oxygen saturation, respectively. It was also associated with an increase of 1.61 mmHg in diastolic arterial blood pressure and 7.46 beats/per minute pulse rate, respectively. In Celik et al.’s (2011) study to determine the effects of fever and nursing interventions to lower fever based on haemodynamic values and oxygenation in febrile surgical ICU patients, the patients had tachycardia before, during and after fever. There was a non-statistically significant trend towards increased heart rate with fever. Diastolic blood pressure, mean arterial blood pressure and SpO2 had a statistically non-significant decrease. Systolic blood pressure had a small but statistically significant decrease during and after fever onset. Therefore fever was associated with an increase in heart rate, decreased systolic arterial pressure, mean arterial pressure, oxygen saturation and hourly urine output (Celik et al., 2011). In Kiekkas et al.’s (2007) study to determine the relationship between fever and haemodynamic parameters among ICU patients, a one degree celsius increase in body temperature, 4.7 beats/per minute increase in heart rate, 2.7 mmHg decrease in systolic blood pressure and, 0.4% decrease in arterial oxygen saturation were observed (Kiekkas et al., 2007). According to the results of our study, changes of haemodynamic parameters could be related to body temperature changes, but body temperature elevation even above 38.5 ◦ C was not found to be accompanied by severe haemodynamic instability, according to the values of standard monitoring parameters. One explanation that is proposed to support this, is that the metabolic burden of fever (body temperature ≤38.5 ◦ C) can be well tolerated without leading to severe haemodynamic instability. Nonetheless, intensive care unit nurses must continuously monitor patients’ haemodynamic parameters during febrile episodes.
Study limitations An important limitation of this study was the use of the axilla method for the measurement of patients’ temperatures on admission to the NICU. However, replacing the routinely used axillary thermometer with the tympanic membrane method during admission was not possible, due in the main to administrative objections and, previously noted errors in tympanic membrane measurements, where haemorrhage into the external ear related to the presence of ear wax had occurred. Conversely the accuracy and reliability of tympanic membrane temperature measurement has been questioned in recent years (Kiekkas et al., 2007). According to the results of Farnell et al.’s study, tympanic and chemical thermometers, in comparison with pulmonary artery catheters, were associated with erroneous readings (Farnell et al., 2005). However, it should be considered that none of the alternative approaches, such as bladder and oesophageal temperature measurements, have been shown to be superior for measuring core body temperature (Kiekkas et al., 2007). Under these circumstances, in order to combine satisfactory levels of accuracy of body temperature
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Effects of fever on haemodynamic parameters measurement, the use of both methods was considered necessary for this study. Another limitation of the present study was that it was conducted with neurosurgical ICU patients in one neurosurgical setting only and is not, therefore, representative of neurosurgical ICU patients in other settings within Turkey or in neurosurgical ICU units in other countries. Furthermore, standard monitoring parameters are also affected by numerous physiological reflexes which in turn may be affected by other factors, such as a patient’s clinical status, the presence of pain, pre-existing illnesses and, types of drugs administered (Heydari, 2000; Kiekkas et al., 2007).
Conclusion This study has investigated the effects of fever on the haemodynamic parameters of patients in one neurosurgical ICU setting in Turkey. Results have demonstrated that fever was followed by a significant decrease of systolic blood pressure and arterial oxygen saturation and an increase of heart rate. It is important for neurosurgical ICU nurses to appreciate the physiological effects of fever, which can cause complications in these patients. Consequently, knowledge about the effects of fever on haemodynamic parameters will be of benefit to nurses in terms of quality and efficacy of care.
Authors contributions HA and MY were responsible for the study conception and design and drafting of the manuscript.
Acknowledgements The authors thank the staff of the neurosurgery intensive care unit and the patients. Funding: No specific grant for this research was received from any funding agency in the public, commercial, or notfor-profit sectors. Conflict of interest: The authors have no conflict of interest to declare.
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and the Infectious Diseases Society of America. Crit Care Med 2008;36(4):1330—49. O’Shea M, Crandon I, Harding H, Donaldson G, Bruce C, Ehikhametalor K, Erman T, Demirhindi H, Göc ¸er AI, Tuna M, Ildan F, Boyar B. Infections in neurosurgical patients admitted to the intensive care unit at the University Hospital of the West Indies. West Indian Med J 2004;53(3):159—63. Pahsa A. Approach febrile patient; 2009. p. 648—56, http://www. gata.edu.tr/dahilibilimler/ichastalik-lari/files/kitaplar [accessed 18.05.09]. Perl TM. Prevention of Staphylococcus aureus infections among surgical patients: beyond traditional perioperative prophylaxis. Surgery 2003;134(5):10—7. Polderman KH. Induced hypothermia and fever control for prevention and treatment of neurological injuries. Lancet 2008;7:1955—69.
Rampen A, Breda E, Dippel D. Tympanic measurement of body temperature in stroke patients turned on its ear. J Neurol Neurosurg Psychiatry 2005;76:1041—2. Ryan M, Levy MM. Clinical review: fever in intensive care unit patients. Crit Care 2003;7:221—5. Schutz LS. Oxygen saturation monitoring by pulse oximetry. In: AACN procedure manual for critical care; 2001. p. 77—82. Steven HJ, Shelsky R, Hindman B, Simmons ST, Todd M. A prospective, observational clinical trial of fever reduction to reduce systemic oxygen consumption in the setting of acute brain injury. Neurocrit Care 2008;9:37—44. Willke TA, Soyletir G, Doganay M. Infectious diseases and microbiology: fever and unknown origin fever. 1st ed. Izmir: Nobel Publisher; 2002.
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Effects of fever on haemodynamic parameters in neurosurgical intensive care unit patients Hossein Asgar Pour a,∗, Meryem Yavuz b,1 a b
Department of Surgical Nursing, Aydin Health School, Adnan Menderes University, Aydin, Turkey Department of Surgical Nursing, School of Nursing, Ege University, Izmir, Turkey
Accepted 9 July 2014
KEYWORDS Fever; Haemodynamic parameters; Neurosurgical intensive care unit
∗ 1
Summary Objective: To investigate the effects of fever on the haemodynamic parameters (pulse rate, arterial oxygen saturation, systolic blood pressure, diastolic blood pressure and mean arterial blood pressure) of patients in a neurosurgical intensive care unit. Design: A prospective, repeated-measures study. Methods: This study was performed in the neurosurgical intensive care unit of a University Hospital in the West of Turkey. The research sample included all patients with at least two occurrences of fever in the postoperative period. Body temperature and haemodynamic parameters of patients were measured on admission, one hour before the onset of fever and during fever (peak temperature). Results: Increase of body temperature during fever episodes was followed by a significant increase in pulse rate (p = 0.001) with significant decreases in systolic blood pressure (p = 0.002) and arterial oxygen saturation (p = 0.001). Furthermore fever episodes were followed by a nonsignificant increase in diastolic blood pressure (p = 0.074) and a non-significant decrease in mean arterial blood pressure (p = 0.097). In this study, a degree celsius (1 ◦ C) increase in body temperature, was associated with a decline of 4.43 mmHg in systolic blood pressure, 0.166 mmHg mean arterial blood pressure and 0.64% arterial oxygen saturation, respectively. It was also associated with an increase of 1.61 mmHg in diastolic arterial blood pressure and 7.46 beats/per minute pulse rate, respectively. Conclusions: The findings from this research have demonstrated the effects that fever can have on haemodynamic parameters of patients in one neurosurgical intensive care unit. Hence the study highlights the importance for intensive care unit (ICU) nurses to appreciate the
Corresponding author. Tel.: +90 256 213 88 66; fax: +90 256 212 42 19. E-mail addresses: [email protected] (H. Asgar Pour), [email protected] (M. Yavuz). Tel.: +90 232 388 11 03; fax: +90 232 388 63 74.
http://dx.doi.org/10.1016/j.iccn.2014.07.001 0964-3397/© 2014 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Asgar Pour H, Yavuz M. Effects of fever on haemodynamic parameters in neurosurgical intensive care unit patients. Intensive Crit Care Nurs (2014), http://dx.doi.org/10.1016/j.iccn.2014.07.001
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H. Asgar Pour, M. Yavuz physiological effects of fever which have the potential to cause complications in febrile patients. Increasing knowledge about the effects of fever on haemodynamic parameters can therefore be of benefit to nurses in terms of quality and efficacy of patient care. © 2014 Elsevier Ltd. All rights reserved.
Implications for Clinical Practice • This study provides data concerning the effect of fever on haemodynamic parameters, relationships between them and, nursing actions related to these changes. Information about accurate and careful measurements of body temperature and haemodynamic parameters play an important role in the prevention of complications during fever among patients in neurosurgical ICU settings. • Neurosurgical intensive care unit staff, particularly during postoperative care, should be proactive in ensuring that they have a formal, evidence-based management plan for management of fever that conforms to the relevant clinical guidelines and integrates multidisciplinary care. • An increase in resources for professional development in the assessment and management of fever is essential for improving and maintaining the skills of staff during and after care.
Introduction Monitoring and evaluating haemodynamic parameters (systolic blood pressure, diastolic blood pressure, mean arterial blood pressure, pulse rate, and arterial oxygen saturation) are essential nursing assessment measures, particularly for patients in intensive care settings (Basoglu et al., 2000; Erdal, 2005; Karadakovan and Eti Aslan, 2012). In addition pulse, body temperature, arterial blood pressure, respiration and pain are basic vital signs and indicators of an individual’s health status. Changes in physiological functions are reflected in the values of an individual’s basic vital signs, consequently deviations from the normal values can indicate disruption of homeostasis (Akinci, 2003; Celik et al., 2011). Therefore assessing vital signs is an effective method for monitoring health status and is essential for accurate diagnosis and delivery of appropriate nursing interventions (Asgari and Soleymani, 2009; Giuffre et al., 1990; Schutz, 2001). The diagnostic value of standard monitoring parameters is high when these values are abnormal, as they are considered sensitive indices of the overall health of patients (Dicle and Istan, 2002; Heydari, 2000; Kanan, 2004; Kiekkas et al., 2007). Whilst measuring and monitoring vital signs are basic nursing skills, nurses also need to know how variations in vital signs affect haemodynamic parameters of patients, relationships between these parameters and, appropriate nursing and multi-disciplinary follow-up that might be required (Ahmadi and Mohammadi, 2003; Asgarpour and Yavuz, 2010; Heydari, 2000; Pahsa, 2009). Fever is an adaptive response to a variety of infectious, inflammatory foreign stimuli. The febrile response confers an immunological advantage to the host over invading microorganisms (Kothari and Karnad, 2005; Laws and Jallo, 2010). Fever results from a cytokine-mediated reaction that results in the generation of acute phase reactants and controlled elevation of body temperature. Fever is defined as an increase in core body temperature ≥38.3 ◦ C (≥101 ◦ F) attributed to the upregulation of the thermostatic setpoint,
which is controlled by the hypothalamus (Heydari, 2000; Jonathan et al., 2009; Kiekkas et al., 2007; Kothari and Karnad, 2005; Laws and Jallo, 2010; Naomi et al., 2008; Willke et al., 2002). Fever is present in 29—36% of all hospitalised patients (Celik et al., 2011; Ferguson, 2007), although the incidence of fever ranges between 28% and 75% in critically ill patients (Celik et al., 2011; Henker et al., 2001; Kiekkas et al., 2007). Fever can result from both infectious and non-infectious causes (Ballestas, 2007; Celik et al., 2011; Cunha, 2013; Kiekkas et al., 2007; Laupland, 2009; Ryan and Levy, 2003; Steven et al., 2008) and febrile episodes occur in roughly 50% of patients in the NICU with neurocritical patients having a slightly lower frequency of fever, approximately 23%, 6 than patients in the neurosurgical ICU, approximately 47% (Laws and Jallo, 2010). Fever is more often an indicator of infection, however in ICU patients, pulmonary embolism, gastrointestinal bleeding, drug reactions, cardiac problems, trauma, surgery, and intracranial bleeding are also associated with fever (Axelrod and Diringer, 2008; Celik et al., 2011; Henker et al., 2001; Jonathan et al., 2009). Fever symptoms among the neurocritical and neurosurgical patient populations predominate with vascular injuries, such as intracerebral haemorrhage and subarachnoid haemorrhage (Laws and Jallo, 2010; Polderman, 2008). According to Laws and Jallo (2010) the highest rates of febrile episodes occur in patients diagnosed with subarachnoid haemorrhage (65%), followed by traumatic brain injury (40%) and then intracranial haemorrhage (31%). Where no cause of fever was identified (in 28% of patients), the authors suggested a fever of central origin. As the body temperature rises, important physiological changes occur (Henker et al., 2001; Kiekkas et al., 2008). A body temperature increase from 37 ◦ C to 39 ◦ C has been found to be followed by a 25% increase of oxygen consumption and energy expenditure in ICU patients (Kiekkas et al., 2007; Kothari and Karnad, 2005). These increases in the metabolic rate and serum levels of stress hormones are suggested to subsequently increase heart rate
Please cite this article in press as: Asgar Pour H, Yavuz M. Effects of fever on haemodynamic parameters in neurosurgical intensive care unit patients. Intensive Crit Care Nurs (2014), http://dx.doi.org/10.1016/j.iccn.2014.07.001
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Effects of fever on haemodynamic parameters
Methods Objective The aim of study was to investigate the effects of fever on the haemodynamic parameters (systolic blood pressure, diastolic blood pressure, mean arterial blood pressure, pulse rate and arterial oxygen saturation) of patients in one neurosurgical intensive care unit of a university hospital in the west of Turkey.
Setting This prospective, repeated-measures study was conducted between June 2009 and May 2010 at the Neurosurgical Intensive Care Unit of Ege University Hospital Izmir, Turkey.
Ethical approval This study was approved by Ege University Institutional Review Board. Written and verbal informed consent was obtained from all conscious patients or patients’ relatives (in semi-conscious or unconscious patients) after explaining the aims and protocol of the study. Written approvals were obtained from the Ege University Institute of Health Sciences (March, 2009), Ethics Board of the Ege University School of Nursing (May, 2009), the Ege University Hospital, and Neurosurgical Department Chief Physician (June, 2009) and Directorate of Nursing Services of Ege University Hospital (June, 2009).
Participants The inclusion criteria were as follows: 1- Voluntary participation in the study, 2- No incidence of fever in the preoperative period and during surgery, 3- At least two episodes of fever in the postoperative period,
N vs Power with Mean0=0,00000 Mean1=0,24143 S=0,20018 Alpha=0,05 WC (N) 30 25 20
N
and arterial blood pressure in febrile patients (Asgarpour and Yavuz, 2010; Kiekkas et al., 2007). Conversely, body temperature increases may result in hypotension due to myocardial depression and vasodilation, especially in the veins of the kidneys, liver, skin, upper and lower limbs (Asgari and Soleymani, 2009; Cooper, 1994; Heydari, 2000; Kiekkas et al., 2007). It is important for neurosurgical ICU nurses to appreciate the physiological effects of fever, which can cause complications in febrile patients in these settings (Celik et al., 2011). Furthermore accurate and careful monitoring of haemodynamic parameters during neurosurgical ICU patients’ febrile episodes can be helpful to determine the process of fever treatment. There are not enough studies related on fever and changes in haemodynamic parameters, i.e., arterial blood pressure, pulse rate, and arterial oxygen saturation (Asgarpour and Yavuz, 2010; Kiekkas et al., 2007). In this study, the effects of fever on the haemodynamic parameters of patients in one neurosurgical intensive care unit in Turkey will be investigated.
3
15 10 5 0 0.70
0.75
0.80
0.85
0.90
0.95
1.00
Power
Figure 1
Numeric results for Wilcoxon test.
4- Surgery occurred at least four hours’ prior to enrollment. The results of a power analysis, with power set at 0.99, suggested that a selection of 20 patients were sufficient for the sample (Fig. 1). The total research sample comprised of 35 patients who met the inclusion criteria. In the present study, for all patients (n = 364) who were admitted to the neurosurgical ICU in the post-operative period, 49 of the patients were eligible for enrollment in the first stage of sampling. In the second stage of sampling, 14 of 49 patients who were selected in the first stage did not enter into the second stage of the study. Patients who died/did not exhibit body temperature increase more than once and patients with body temperature over ≥40 ◦ C/requiring antipyretic agents treatment were excluded. Therefore, 35 of 49 patients were selected (Fig. 2).
Data collection In the present study, body temperature was measured by the axilla mercury-glass thermometer; by the tympanic membrane commercial infrared tympanic thermometer (Felix, Thermo-Scan Thermometer 952) and, by the haemodynamic parameters non-invasive monitoring system (Bruker TMSN — 910CD/Ni12v 1.9 Ah). For measurement of body temperature on admission to the neurosurgical ICU, the axilla method was used (in admission to the NICU the axilla method was used for measurement of BT because of the risk for trauma in external ear or the presence of earwax which could incur incorrect results). For measurement of body temperature one hour before the onset of fever (when body temperature was 36.7, BT and haemodynamic parameters were measured per 15 minutes until fever was appeared) and during fever, the tympanic membrane method was used (in the post-operative period for correction results the body temperature was measured by the tympanic membrane method). The following derived regression equation was used for the adjustment of axillary temperature values to tympanic membrane temperature ones: Tympanic membrane temperature (◦ C) = 0.889 + 0.982 × axillary temperature (◦ C) (Kiekkas et al., 2007). The tympanic membrane temperature reflects the temperature of the hypothalamus and thus, the core body temperature (Naomi et al., 2008). In a study conducted by
Please cite this article in press as: Asgar Pour H, Yavuz M. Effects of fever on haemodynamic parameters in neurosurgical intensive care unit patients. Intensive Crit Care Nurs (2014), http://dx.doi.org/10.1016/j.iccn.2014.07.001
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H. Asgar Pour, M. Yavuz The number of operaons in the neurosurgery operaon room during the study (n = 1527).
The number of paents in the neurosurgery intensive care unit in the postoperave period (n=364)
Paents who did not enter the second stage of the study (n = 14): Paents with appropriate criteria in the first stage of the study (n = 49).
- Paents who died/did not exhibit body temperature increase more than once (n = 6). - Paents with body temperature over ≥ 40°C /requiring anpyrec agents treatment (n = 3). Lacking the iniaves at the appropriate me by researchers (n=5).
The number of samples taken for analysis (n = 35).
Figure 2
The stages of sample selection.
Mariak et al. (2003) during neurosurgical operations, brain temperature fluctuations of patients with an open cranium were followed closely by changes in tympanic membrane temperature, but not by oesophageal temperature. The results of a further study by Rampen et al. (2005) support the use of tympanic membrane temperature as an extracranial estimate of intracranial temperatures. Furthermore, tympanic membrane temperature measurement is easier, faster and less invasive than other measurements (Kiekkas et al., 2007). In the study conducted by Klein et al. (1993) tympanic membrane temperature was shown to be strongly correlated with pulmonary artery temperature, thus it was considered to properly represent core body temperature (Klein et al., 1993). In the present study fever was defined as an increase of body temperature ≥38.3 ◦ C (Asgarpour and Yavuz, 2010; Kiekkas et al., 2007). Body temperature and haemodynamic parameters were measured and recorded at admission and at one hour intervals on the neurosurgical ICU daily chart. During the postoperative period body temperature and haemodynamic parameters were measured every 15 minutes when the body temperature reached >37.6 ◦ C. Body temperature and haemodynamic parameters were measured again when fever (BT ≥ 38.3 ◦ C) manifested. During fever, the highest temperature (peak temperature) was the value measured just prior to peripheral cold application. The authors determined three time points (at admission, one hour before the onset of fever and during fever) for comparison changes of haemodynamic parameters during febrile episodes.
Validity and reliability To standardise the mercury-glass thermometers, thermometers were placed in 38 ◦ C water for two minutes, and those showing the appropriate temperature at the end of this
period were used. Furthermore, to measure body temperature via the tympanic membrane, external ears of patients in the sample were evaluated for signs of wounds and trauma. A tympanic thermometer was then inserted in the external ear and measurements were performed using both ears (Ilce and Karabay, 2009). Haemodynamic Standard Monitoring systems calibrated three times (once before and twice during the research) by an external company, and measurements were performed after control measurements by the responsible company.
Data analysis Data analysis was performed by the University Biostatistics and Medical Informatics Main Field of Study by using SPSS version 16.0 (Statistics for Social Sciences) for the Windows statistics programme. Data analyses were performed for all participants who completed the study (N = 35). Friedman and Wilcoxon Signed Ranks Tests were used to check the normality of distribution of continuous variables. Data are presented as means and standard deviations. Age of patients, operation time and temperature of NICU were analysed by percentages, means and standard deviation. To compare standard monitoring parameters between admission, one hour before the onset of fever episodes and during fever episodes (peak temperature), paired samples t-tests were used. Statistical significance was set at p < 0.05.
Results Normally distributed continuous variables are presented as mean ± standard deviation. Thirty-five patients with at least two episodes of increased body temperature were included in this study. The mean age of patients was 49.71 ± 17.65 years, and 62.9% patients were men. In relation to disease diagnosis, 68.6% patients had suffered a brain haemorrhage,
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Table 1 Mean pulse rate, O2 Sat, systolic blood pressure, diastolic blood pressure and MAP of patients at admission and 1 h before the onset of fever episode.
Pulse ratea O2 Satb Systolic blood pressurec Diastolic blood pressurec MAPc a b c
At admission
1 h before the onset of fever
p value
89.8 ± 17.8 96.4 ± 2.3 135.2 ± 27.5
93.4 ± 17.6 96.01 ± 2.11 132.9 ± 14.5
p = 0.383 p = 0.433 p = 0.678
79.1 ± 19.3
77.2 ± 11.6
p = 0.610
97.8 ± 21.2
95.7 ± 12.02
p = 0.624
B/PM = beats/per minute. %. mmHg.
28.6% brain tumour, 2.8 brain abscess, and the mean operation time was 3.85 ± 0.68 hours. In addition 31.4% patients had hypertension and 5.7% had diabetes mellitus. Fever appeared in 51.4% patients after the third day of operation and the mean magnitude of fever was 38.51 ◦ C. During fever, 62.9% patients were semi-conscious and 54.2% exhibited no signs of infections. Furthermore 34.2% of patients had central venous lines, 100.0% had Foley catheters inserted and 22.9% had brain catheters inserted for monitoring intracerebral pressure. In addition 77.2% of patients received supportive oxygen by different methods (37.03% by tracheostomy, 33.3% intubation, 29.6% by mask/nasal prongs) with FiO2 between 24 and 40% during fever episodes. No patients received antipyretic agents during fever episodes, though 33.3% of patients were sedated and 2.8% of patients received inotropic agents. The mean body temperature at admission, one hour before the onset of fever and during fever was 37.30, 37.37, and 38.51 ◦ C, respectively. Furthermore, the average temperature of the intensive care unit was 24.3 ± 1.32 ◦ C. Between admission and one hour before the onset of fever episodes, pulse rates of patients demonstrated a nonsignificant increase (p > 0.05), whilst O2 Sat, systolic blood pressure, diastolic blood pressure and MAP (mean arterial blood pressure) demonstrated a non-significant decrease, respectively (p > 0.05) (Table 1). Between one hour before the onset of fever and during fever episodes, pulse rates of patients demonstrated a significant increase (p < 0.05), whereas diastolic blood pressure demonstrated a non-significant increase (p > 0.05). At the same time O2 Sat and systolic blood pressure demonstrated a significant decrease (p < 0.05) and MAP, a non-significant decrease, respectively (p > 0.05) (Table 2). In this study, during fever, the pulse rate 8.528 ± 4.42 beats/per minute and diastolic blood pressure 1.842 ± 6.9 mmHg increased respectively. Furthermore, systolic blood pressure 5.07 ± 7.89 mmHg, mean arterial blood pressure 0.191 ± 6.00 mmHg and arterial oxygen saturation 0.742 ± 0.97% decreased respectively. According to the results of this study, a one degree celsius (1 ◦ C) increase in body temperature, was associated with a decline of
Table 2 Mean pulse rate, O2 Sat, systolic blood pressure, diastolic blood pressure and MAP of patients at 1 h before the onset of fever and during fever episode.
Pulse rate O2 Sat Systolic blood pressure Diastolic blood pressure MAP
1 h before the onset of fever
During fever
p value
93.4 ± 17.6 96.01 ± 2.11 132.9 ± 14.5
102.0 ± 20.8 95.2 ± 2.7 127.8 ± 15.7
p = 0.001 p = 0.001 p = 0.002
77.2 ± 11.6
79.1 ± 12.5
p = 0.074
95.7 ± 12.02
95.1 ± 12.7
p = 0.973
4.43 mmHg in systolic blood pressure, 0.166 mmHg mean arterial blood pressure and 0.64% arterial oxygen saturation and, an increase of 1.61 mmHg in diastolic arterial blood pressure and 7.46 beats/per minute pulse rate.
Discussion The variables investigated in this study, body temperature and haemodynamic parameters, were measured every 15 minutes to determine peak temperature when a patient’s body temperature reached >37.6 ◦ C in the postoperative period. Therefore the authors concluded that peak temperature measurements of fever episodes which were used were close to true peak temperatures. Standard monitoring of neurosurgical ICU patients includes the observation of electrocardiogram, heart rate, arterial blood pressure, and arterial oxygen saturation (Asgarpour and Yavuz, 2010; Heydari, 2000). The diagnostic value of monitoring standard parameters is very important, as these are considered sensitive indicators of the overall health of patients (Asgarpour and Yavuz, 2010; Heydari, 2000; Kiekkas et al., 2007). Neurosurgical ICU patients have life threatening conditions or injuries for which they have had surgery, invasive monitoring and other procedures, all of which can compromise their host defences (Laws and Jallo, 2010). It has been noted that febrile episodes occur from both infectious and non-infectious causes in neurosurgical ICU patients (Kothari and Karnad, 2005; Laws and Jallo, 2010). About 50% of fevers in the ICU are due to infectious causes (Kothari and Karnad, 2005). Staphylococcus aureus causes 25% of health care-related infection and the source of many of these infections is thought to originate from the patients’ endogenous flora (Perl, 2003). In the present study 13.4% of all patients in the postoperative period presented with a fever. Of these patients 20.2% had bacteriological confirmation of infection, 8.6% of which were from methicillin-resistant Staphylococcus aureus (MRSA) and S. aureus. This suggests that these were health care- related infections. In O’Shea et al.’s (N = 73) to determine infections in neurosurgical ICU patients, 28.8% of patients developed infection and the responsible organisms included pseudomonas, acinetobacter, E. coli, enterobacter, klebsiella, S. aureus and MRSA (O’Shea et al., 2004). In Erman et al.’s
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(2005) study to determine risk factors for surgical site infections in neurosurgery patients (N = 503), 6.2% of patients developed infection. The predominantly isolated microorganisms in patients were S. aureus (71.0%), acinetobacter baumanii (16.1%), and Staphylococcus epidermidis (12.9%) (Erman et al., 2005). The results of Sturm’s with neurosurgical patients’ related to surgical site infection showed that the majority (65%) of micro-organisms in craniotomy wounds were gram-positive. A study by Celik et al. on surgical ICU patients (neurosurgery 54.7%, anaesthesia 26.4%, general 17% and sub-specialty surgery 1.9%) with fever (N = 53), showed that the majority of patients had an infectious cause for their fever, with acinetobacter and pseudomonas infections isolated in the majority of these febrile patients. Celik et al. described acinetobacter and pseudomonas as the most common causes of nosocomial pneumonia, urinary tract and catheter-related infections in ICU patients (Celik et al., 2011). In the present study fever episodes were followed by a significant increase in heart rate, a significant decrease of systolic arterial blood pressure, a non-significant increase of diastolic arterial blood pressure and a non-significant decrease of mean arterial blood pressure. These findings suggest the adverse effects of fever on cardiac performance, decreased mean arterial blood pressure and increased heart rate during febrile episodes. Although increases in heart rate during the febrile state is associated with decreased of mean arterial blood pressure, the tachycardia response indicated failure to maintain effective cardiac output. During fever episodes, increases in the metabolic rate and serum levels of cortisol and norepinephrine hormones are thought to subsequently increase the pulse rate and arterial blood pressure (Kiekkas et al., 2007, 2008). Increases of oxygen consumption and energy expenditure also occur during fever, thus increases in the metabolic rate and serum levels of stress hormones are suggested to subsequently increase heart rate (Cooper, 1994; Kiekkas et al., 2007). Body temperature increases may result in hypotension due to myocardial depression and vasodilation (Dalal and Zhukovsky, 2006; Kiekkas et al., 2007; Pahsa, 2009). A possible explanation is that arterial blood pressure tends to increase due to metabolic rate increase and catecholamine secretion and to decrease due to vasodilation and myocardial depression (Ferguson, 2007; Marik, 2000). In the present study fever was followed by a significant decrease of arterial oxygen saturation, which is defined by the oxyhaemoglobin dissociation curve: when the body temperature increases, this curve is shifted rightward. This means that, for a given value of partial pressure of oxygen in arterial blood, the arterial oxygen saturation value decreases (Bacher, 2005). An increase in metabolic rate is followed by an oxygen consumption increase, which may result in a decrease of oxygen partial pressure in arterial blood. This is especially so for patients with a disrupted compensatory ability against increased metabolic demand (neurosurgical and neurological patients), such as patients with sepsis (Laws and Jallo, 2010). Subsequent increases in oxygen consumption, respiratory rate and cardiac output add a considerable burden to these patients, who may be unable to compensate for the increased metabolic demand (Bacher, 2005; Asgarpour and Yavuz, 2010; Steven et al., 2008).
In our study, a degree celsius (1 ◦ C) increase in body temperature, was associated with a decline of 4.43 mmHg in systolic blood pressure, 0.166 mmHg mean arterial blood pressure and 0.64% arterial oxygen saturation, respectively. It was also associated with an increase of 1.61 mmHg in diastolic arterial blood pressure and 7.46 beats/per minute pulse rate, respectively. In Celik et al.’s (2011) study to determine the effects of fever and nursing interventions to lower fever based on haemodynamic values and oxygenation in febrile surgical ICU patients, the patients had tachycardia before, during and after fever. There was a non-statistically significant trend towards increased heart rate with fever. Diastolic blood pressure, mean arterial blood pressure and SpO2 had a statistically non-significant decrease. Systolic blood pressure had a small but statistically significant decrease during and after fever onset. Therefore fever was associated with an increase in heart rate, decreased systolic arterial pressure, mean arterial pressure, oxygen saturation and hourly urine output (Celik et al., 2011). In Kiekkas et al.’s (2007) study to determine the relationship between fever and haemodynamic parameters among ICU patients, a one degree celsius increase in body temperature, 4.7 beats/per minute increase in heart rate, 2.7 mmHg decrease in systolic blood pressure and, 0.4% decrease in arterial oxygen saturation were observed (Kiekkas et al., 2007). According to the results of our study, changes of haemodynamic parameters could be related to body temperature changes, but body temperature elevation even above 38.5 ◦ C was not found to be accompanied by severe haemodynamic instability, according to the values of standard monitoring parameters. One explanation that is proposed to support this, is that the metabolic burden of fever (body temperature ≤38.5 ◦ C) can be well tolerated without leading to severe haemodynamic instability. Nonetheless, intensive care unit nurses must continuously monitor patients’ haemodynamic parameters during febrile episodes.
Study limitations An important limitation of this study was the use of the axilla method for the measurement of patients’ temperatures on admission to the NICU. However, replacing the routinely used axillary thermometer with the tympanic membrane method during admission was not possible, due in the main to administrative objections and, previously noted errors in tympanic membrane measurements, where haemorrhage into the external ear related to the presence of ear wax had occurred. Conversely the accuracy and reliability of tympanic membrane temperature measurement has been questioned in recent years (Kiekkas et al., 2007). According to the results of Farnell et al.’s study, tympanic and chemical thermometers, in comparison with pulmonary artery catheters, were associated with erroneous readings (Farnell et al., 2005). However, it should be considered that none of the alternative approaches, such as bladder and oesophageal temperature measurements, have been shown to be superior for measuring core body temperature (Kiekkas et al., 2007). Under these circumstances, in order to combine satisfactory levels of accuracy of body temperature
Please cite this article in press as: Asgar Pour H, Yavuz M. Effects of fever on haemodynamic parameters in neurosurgical intensive care unit patients. Intensive Crit Care Nurs (2014), http://dx.doi.org/10.1016/j.iccn.2014.07.001
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Effects of fever on haemodynamic parameters measurement, the use of both methods was considered necessary for this study. Another limitation of the present study was that it was conducted with neurosurgical ICU patients in one neurosurgical setting only and is not, therefore, representative of neurosurgical ICU patients in other settings within Turkey or in neurosurgical ICU units in other countries. Furthermore, standard monitoring parameters are also affected by numerous physiological reflexes which in turn may be affected by other factors, such as a patient’s clinical status, the presence of pain, pre-existing illnesses and, types of drugs administered (Heydari, 2000; Kiekkas et al., 2007).
Conclusion This study has investigated the effects of fever on the haemodynamic parameters of patients in one neurosurgical ICU setting in Turkey. Results have demonstrated that fever was followed by a significant decrease of systolic blood pressure and arterial oxygen saturation and an increase of heart rate. It is important for neurosurgical ICU nurses to appreciate the physiological effects of fever, which can cause complications in these patients. Consequently, knowledge about the effects of fever on haemodynamic parameters will be of benefit to nurses in terms of quality and efficacy of care.
Authors contributions HA and MY were responsible for the study conception and design and drafting of the manuscript.
Acknowledgements The authors thank the staff of the neurosurgery intensive care unit and the patients. Funding: No specific grant for this research was received from any funding agency in the public, commercial, or notfor-profit sectors. Conflict of interest: The authors have no conflict of interest to declare.
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