British Journal of Anaesthesia 1991; 67: 683-689
EFFECT OF ADRENALINE ON EXTRADURAL ANAESTHESIA, PLASMA LIGNOCAINE CONCENTRATIONS AND THE FETO-PLACENTAL UNIT DURING ELECTIVE CAESAREAN SECTION A. J. McLINTIC, F. H. DANSKIN, J. A. REID AND J. THORBURN
ing solution, a smaller dose of lignocaine was required to produce an adequate block and the lignocaine concentrations in both mother and neonate were significantly smaller compared with the plain solution. Arterial pressures were less in the adrenaline group, but there was no difference in umbilical flow velocity waveform, fetal heart rate or fetal outcome. Neither fetoplacental circulation nor fetal outcome were affected adversely by episodes of hypotension or the ephedrine used for treatment.
PATIENTS AND METHODS
We studied 20 healthy women undergoing elective Caesarean section. The study was approved by the Ethics Committee of The Queen Mother's Hospital and all patients gave informed consent. The indication for elective Caesarean section was either repeat Caesarean section or breech presentation. There was no evidence of preoperative fetal compromise or maternal disease. Patients were given ranitidine 150 mg by mouth KEY WORDS on the evening before and on the morning of Anaesthesia: obstetric. Anaesthetic techniques: extradural. surgery. Before extradural anaesthesia was inPlacenta, umbilical blood flow. duced, patients were pre-loaded with Hartmann's solution 1 litre. They were then allocated ranAlthough bupivacaine is the agent used most domly to receive either 2 % plain lignocaine (group commonly for Caesarean section under extradural A; n = 10) or 2% lignocaine with adrenaline anaesthesia in the U.K., lignocaine has been 1:200000 (group B; n = 10). Both patient and shown to be an effective alternative and confers investigator were blind to the identity of the certain advantages over bupivacaine in this con- solution used. With the patient in either the text [1]. With a lower p/C., lignocaine has a sitting or lateral position, a 20-gauge extradural shorter latency of effect which facilitates dose catheter was inserted via an 18-gauge Tuohy titration and reduces preoperative preparation needle at L3-4. The extradural space was identtime [1, 2]. In addition, intractable cardiovascular toxicity has not been associated with the use of lignocaine, but is an important toxic effect of This article is accompanied by Editorial I. J. MCLINTIC, M.R.C.P., F.C.ANAES.; JOYCE A . R E I D , bupivacaine [3]. It has been shown, in contexts ALAN F.C.ANAES.; JOHN THORBURN, F.C.ANAES.; Department of other than Caesarean section, that the efficacy of Anaesthesia, Western Infirmary, Dumbarton Road, Glasgow extradural lignocaine may be improved further if G i l 6NT. FIONA H. DANSKIN, D.R.C.O.C, Cruden Medical an adrenaline-containing solution is used [4-6]. Research Fellow in Obstetrics, Department of Midwifery, of Glasgow, The Queen Mother's Hospital, The aim of this study was to determine if a University Yorkhill, Glasgow. Accepted for Publication: June 14, 1991. lignocaine and adrenaline solution has advantages Correspondence to A.J.McL.
Downloaded from http://bja.oxfordjournals.org/ at Florida Atlantic University on July 9, 2015
over a plain lignocaine solution when used to provide extradural anaesthesia for Caesarean Extradural anaesthesia was induced with either section. The comparison between the techniques 2% lignocaine or 2% lignocaine with adrenaline was made in terms of anaesthetic characteristics, 1:200000 in 20 patients undergoing elective plasma concentrations of lignocaine, maternal and Caesarean section. With the adrenaline-contain- fetal haemodynamics and fetal outcome. SUMMARY
BRITISH JOURNAL OF ANAESTHESIA
684
Maximum systolic velocity Minimum diastolic velocity A-B 2. PI = Mean
1. A : B ratio -
A (maximum)
Time FIG. 1. Characteristic umbilical artery flow velocity waveform showing derivation of A:B ratio and pulsatility index (PI). The Dopplcr frequency shift (FD) is directly proportional to flow velocity.
of measurement [7, 8]. As the end-diastolic velocity varies with fetal heart rate (FHR), changes in the A: B ratio may reflect changes in FHR and changes in placental resistance [9]. Therefore, A: B ratios were corrected for FHR using a modal heart rate of 140 beat min"1 and the method described by Mires and colleagues [9]. As the importance of this correction is contentious when the FHR is within normal limits, results are given in both corrected and uncorrected forms [10]. Studies were performed using a Doptek 4-MHz continuous wave Doppler system with on-line spectral analysis. Measurements were made with the patient in the modified supine position. The umbilical artery was located using twodimensional ultrasonography. The Doppler transducer was orientated so that the umbilical arterial signal had maximum amplitude and minimum artefact and could be displayed together with the venous trace. Five consecutive waveforms were recorded at the following times: before insertion of the extradural catheter, immediately before Caesarean section, during episodes of hypotension and after administration of ephedrine. Calculation of the mean A:B ratios, PI and FHR were carried out using on-board custom-written software. Maternal venous blood samples were taken from the non-infusion arm before the test dose, at 10-min intervals from the time at which an adequate block was achieved and immediately after delivery. Umbilical arterial and venous blood samples were taken immediately after delivery for blood-gas and plasma lignocaine analysis. Samples for lignocaine assay were stored at 4 °C after centrifugation and plasma separation. Lignocaine assay was carried out by a solvent extraction method using high pressure liquid chromatography [11]. Neonatal Apgar scores were recorded at 1 min and 5 min. Statistics Statistical evaluation of the data was carried out using the Minitabs Release 7.1 statistical package. Data were analysed by Student's t test, chi-square and Mann—Whitney U test where appropriate. P < 0.05 was considered significant. Values are expressed as mean (SD). RESULTS
One patient in group B required spinal anaesthesia after failure to achieve a level of block above T10. Her results were not included in the analysis.
Downloaded from http://bja.oxfordjournals.org/ at Florida Atlantic University on July 9, 2015
ified using loss of resistance with local analgesia comprising 0.5 % prilocaine 2 ml. Extradural block was then induced with the patient in the left lateral position. An initial test dose of 3 ml of the allocated solution was followed by a 10-ml dose after 5 min. At 5-min intervals thereafter the level of anaesthesia to pinprick was assessed and further increments given according to the extent of spread. This was continued until an adequate block was achieved (loss of pinprick sensation from S5 to T6 bilaterally). The time taken to achieve an adequate block (measured from the time of test dose), the total dose of lignocaine used to produce the block, and the time at which further analgesia was required were recorded. Arterial pressure and heart rate were measured using a 2200 I Datascope at 1-min intervals from the time of catheter insertion. The incidence of significant hypotension (systolic arterial pressure ^ 90 mm Hg) was noted. Hypotension was treated by increasing the rate of infusion and, if necessary, by a bolus dose of ephedrine 6 mg. The feto-placental circulation was assessed using Doppler velocimetry. When placental vascular resistance increases, the umbilical artery flow decreases [7]. This is reflected in a reduction in diastolic flow velocity and Doppler frequency. The resulting changes in the umbilical arterial flow velocity waveform may be assessed quantitatively by measuring the peak systolic: minimum diastolic velocity ratio (A:B ratio) and the pulsatility index (PI) (fig. 1). An increase in one of these values reflects an increase in flow resistance within the vascular bed distal to the site
LIGNOCAINE AND ADRENALINE IN CAESAREAN SECTION
685
TABLE I. Patient characteristics (mean (.range or SD)). No significant differences between groups
2% Lignocaine 2% Lignocaine + adrenaline
n
Age (yr)
Gestation (weeks)
10 9
29.0(19-37) 29.3 (17-37)
38.4 (0.88) 38.8(1.32)
Weight (kg) 55.3 (8.44) 62.1(13.95)
Height (m)
1.59(0.05) 1.62(0.09)
TABLE II. Characteristics of extradural anaesthesia. Mean (SD or, median and range)
Dose required (mg) Onset time (min) Time to further analgesia (min)
493 (64.2) 35.8(17.00) 92.9(86; 11-220)
2% Lignocaine + adrenaline (« = 9)
P
400(108) 29.9(9.14) 237(100; 12-694)
EFFECT OF ADRENALINE ON EXTRADURAL ANAESTHESIA, PLASMA LIGNOCAINE CONCENTRATIONS AND THE FETO-PLACENTAL UNIT DURING ELECTIVE CAESAREAN SECTION A. J. McLINTIC, F. H. DANSKIN, J. A. REID AND J. THORBURN
ing solution, a smaller dose of lignocaine was required to produce an adequate block and the lignocaine concentrations in both mother and neonate were significantly smaller compared with the plain solution. Arterial pressures were less in the adrenaline group, but there was no difference in umbilical flow velocity waveform, fetal heart rate or fetal outcome. Neither fetoplacental circulation nor fetal outcome were affected adversely by episodes of hypotension or the ephedrine used for treatment.
PATIENTS AND METHODS
We studied 20 healthy women undergoing elective Caesarean section. The study was approved by the Ethics Committee of The Queen Mother's Hospital and all patients gave informed consent. The indication for elective Caesarean section was either repeat Caesarean section or breech presentation. There was no evidence of preoperative fetal compromise or maternal disease. Patients were given ranitidine 150 mg by mouth KEY WORDS on the evening before and on the morning of Anaesthesia: obstetric. Anaesthetic techniques: extradural. surgery. Before extradural anaesthesia was inPlacenta, umbilical blood flow. duced, patients were pre-loaded with Hartmann's solution 1 litre. They were then allocated ranAlthough bupivacaine is the agent used most domly to receive either 2 % plain lignocaine (group commonly for Caesarean section under extradural A; n = 10) or 2% lignocaine with adrenaline anaesthesia in the U.K., lignocaine has been 1:200000 (group B; n = 10). Both patient and shown to be an effective alternative and confers investigator were blind to the identity of the certain advantages over bupivacaine in this con- solution used. With the patient in either the text [1]. With a lower p/C., lignocaine has a sitting or lateral position, a 20-gauge extradural shorter latency of effect which facilitates dose catheter was inserted via an 18-gauge Tuohy titration and reduces preoperative preparation needle at L3-4. The extradural space was identtime [1, 2]. In addition, intractable cardiovascular toxicity has not been associated with the use of lignocaine, but is an important toxic effect of This article is accompanied by Editorial I. J. MCLINTIC, M.R.C.P., F.C.ANAES.; JOYCE A . R E I D , bupivacaine [3]. It has been shown, in contexts ALAN F.C.ANAES.; JOHN THORBURN, F.C.ANAES.; Department of other than Caesarean section, that the efficacy of Anaesthesia, Western Infirmary, Dumbarton Road, Glasgow extradural lignocaine may be improved further if G i l 6NT. FIONA H. DANSKIN, D.R.C.O.C, Cruden Medical an adrenaline-containing solution is used [4-6]. Research Fellow in Obstetrics, Department of Midwifery, of Glasgow, The Queen Mother's Hospital, The aim of this study was to determine if a University Yorkhill, Glasgow. Accepted for Publication: June 14, 1991. lignocaine and adrenaline solution has advantages Correspondence to A.J.McL.
Downloaded from http://bja.oxfordjournals.org/ at Florida Atlantic University on July 9, 2015
over a plain lignocaine solution when used to provide extradural anaesthesia for Caesarean Extradural anaesthesia was induced with either section. The comparison between the techniques 2% lignocaine or 2% lignocaine with adrenaline was made in terms of anaesthetic characteristics, 1:200000 in 20 patients undergoing elective plasma concentrations of lignocaine, maternal and Caesarean section. With the adrenaline-contain- fetal haemodynamics and fetal outcome. SUMMARY
BRITISH JOURNAL OF ANAESTHESIA
684
Maximum systolic velocity Minimum diastolic velocity A-B 2. PI = Mean
1. A : B ratio -
A (maximum)
Time FIG. 1. Characteristic umbilical artery flow velocity waveform showing derivation of A:B ratio and pulsatility index (PI). The Dopplcr frequency shift (FD) is directly proportional to flow velocity.
of measurement [7, 8]. As the end-diastolic velocity varies with fetal heart rate (FHR), changes in the A: B ratio may reflect changes in FHR and changes in placental resistance [9]. Therefore, A: B ratios were corrected for FHR using a modal heart rate of 140 beat min"1 and the method described by Mires and colleagues [9]. As the importance of this correction is contentious when the FHR is within normal limits, results are given in both corrected and uncorrected forms [10]. Studies were performed using a Doptek 4-MHz continuous wave Doppler system with on-line spectral analysis. Measurements were made with the patient in the modified supine position. The umbilical artery was located using twodimensional ultrasonography. The Doppler transducer was orientated so that the umbilical arterial signal had maximum amplitude and minimum artefact and could be displayed together with the venous trace. Five consecutive waveforms were recorded at the following times: before insertion of the extradural catheter, immediately before Caesarean section, during episodes of hypotension and after administration of ephedrine. Calculation of the mean A:B ratios, PI and FHR were carried out using on-board custom-written software. Maternal venous blood samples were taken from the non-infusion arm before the test dose, at 10-min intervals from the time at which an adequate block was achieved and immediately after delivery. Umbilical arterial and venous blood samples were taken immediately after delivery for blood-gas and plasma lignocaine analysis. Samples for lignocaine assay were stored at 4 °C after centrifugation and plasma separation. Lignocaine assay was carried out by a solvent extraction method using high pressure liquid chromatography [11]. Neonatal Apgar scores were recorded at 1 min and 5 min. Statistics Statistical evaluation of the data was carried out using the Minitabs Release 7.1 statistical package. Data were analysed by Student's t test, chi-square and Mann—Whitney U test where appropriate. P < 0.05 was considered significant. Values are expressed as mean (SD). RESULTS
One patient in group B required spinal anaesthesia after failure to achieve a level of block above T10. Her results were not included in the analysis.
Downloaded from http://bja.oxfordjournals.org/ at Florida Atlantic University on July 9, 2015
ified using loss of resistance with local analgesia comprising 0.5 % prilocaine 2 ml. Extradural block was then induced with the patient in the left lateral position. An initial test dose of 3 ml of the allocated solution was followed by a 10-ml dose after 5 min. At 5-min intervals thereafter the level of anaesthesia to pinprick was assessed and further increments given according to the extent of spread. This was continued until an adequate block was achieved (loss of pinprick sensation from S5 to T6 bilaterally). The time taken to achieve an adequate block (measured from the time of test dose), the total dose of lignocaine used to produce the block, and the time at which further analgesia was required were recorded. Arterial pressure and heart rate were measured using a 2200 I Datascope at 1-min intervals from the time of catheter insertion. The incidence of significant hypotension (systolic arterial pressure ^ 90 mm Hg) was noted. Hypotension was treated by increasing the rate of infusion and, if necessary, by a bolus dose of ephedrine 6 mg. The feto-placental circulation was assessed using Doppler velocimetry. When placental vascular resistance increases, the umbilical artery flow decreases [7]. This is reflected in a reduction in diastolic flow velocity and Doppler frequency. The resulting changes in the umbilical arterial flow velocity waveform may be assessed quantitatively by measuring the peak systolic: minimum diastolic velocity ratio (A:B ratio) and the pulsatility index (PI) (fig. 1). An increase in one of these values reflects an increase in flow resistance within the vascular bed distal to the site
LIGNOCAINE AND ADRENALINE IN CAESAREAN SECTION
685
TABLE I. Patient characteristics (mean (.range or SD)). No significant differences between groups
2% Lignocaine 2% Lignocaine + adrenaline
n
Age (yr)
Gestation (weeks)
10 9
29.0(19-37) 29.3 (17-37)
38.4 (0.88) 38.8(1.32)
Weight (kg) 55.3 (8.44) 62.1(13.95)
Height (m)
1.59(0.05) 1.62(0.09)
TABLE II. Characteristics of extradural anaesthesia. Mean (SD or, median and range)
Dose required (mg) Onset time (min) Time to further analgesia (min)
493 (64.2) 35.8(17.00) 92.9(86; 11-220)
2% Lignocaine + adrenaline (« = 9)
P
400(108) 29.9(9.14) 237(100; 12-694)
