Anaesth Intens Care (1990), 18, 175-179
The Haemodynamic Effects of Propofol and Thiopentone for Induction of Caesarean Section T. GIN*, M. A. GREGORyt AND T. E. OH*
Department oj Anaesthesia and Intensive Care, Prince oj Wales Hospital, The Chinese University oj Hong Kong, Shatin, N. T., Hong Kong SUMMARY Forty Chinese women jor elective caesarean section received either propojol 2 mgkg· 1 or thiopentone 4 mg.kgl jor induction ojgeneral anaesthesia. Systolic, mean and diastolic arterial pressures and heart rate were recorded non-invasively every minute jor ten minutes. Postinduction arterial pressures were similar to pre-induction values with no differences between thiopentone and propojol. Following intubation, the rise in systolic arterial pressure was greater in the thiopentone group, 32.1 mmHg (SD 23.7) compared with the propojol group, 17.4 mmHg (SD 23.8), (P < 0.05). In the thiopentone group, arterial pressures were slower in returning to baseline values. Heart rate was initially elevated in both groups to the same degree. At caesarean section, induction with propojol causes less variation in arterial pressure than thiopentone. Hypotension is probably prevented by the coincident stimulus oj rapid sequence induction. Neonatal Apgar scores were similar between the two groups. Key Words: ANAESTHESIA, ANESTHESIA; obstetrical; ANAESTHETICS, ANESTHETICS, INTRA VENOUS; propofol, thiopentone.
Recovery after induction of anaesthesia with propofol is more rapid than thiopentone 1 and this could be advantageous for caesarean section patients who are still at risk of aspiration in the postoperative period. However, following induction doses of propofol, a fall in systolic arterial pressure has been widely reported. 2- 6 This could be detrimental to placental perfusion and restrict the use ofpropofol in obstetrics. This study set out to compare the haemodynamic effects of propofol to those of thiopentone, as part of a rapid sequence induction of anaesthesia for elective caesarean section.
*8.Se .. F.F.A.R.C.S., F.F.A.R.A.C.S., Lecturer. tF.F.A.R.C.S .. Lecturer. tF.F.A.R.C.S .. F.F.A. R.A.C.S., F.F.A.R.A.C.S. (Int. Care). Professor. Address for Reprints: Dr. T. Gin, Department of Anaesthesia and Intensive Care. Prince of Wales Hospital. The Chinese University of Hong Kong, Shatin. N.T .. Hong Kong Accepted for publication January 12, 1990
Anaesthesia and Intensive Care, Vol. 18, No. 2, May, 1990
MATERIALS AND METHODS After approval by the Chinese University Ethics Committee, forty ASA grade 1 Chinese women undergoing elective caesarean section at term gave their written informed consent to be studied. There was no evidence of pregnancy-induced hypertension, preeclampsia or overt supine hypotension. All patients were given ranitidine 150 mg orally the night before and again two hours before surgery. Mothers were transported to theatre lying on their sides and a 15 degree left lateral tilt was maintained on the operating table. Sodium citrate 0.3M 30 ml was given orally, five minutes before induction of anaesthesia. The women were randomly allocated to receive thiopentone 4 mg.kg- I or propofol 2 mg.kg- I . Drugs and fluid were administered through a cannula in the left forearm while blood pressure was monitored on the right arm with an automatic oscillotonometer (Dinamap 1846SXP,
176
T. GIN ET AL.
Critikon) with the appropriate size cuff. The machine was programmed to cycle every minute and the output was recorded on the attached printer. An electrocardiogram was continuously monitored and the patient preoxygenated for at least three minutes. The initial intravenous fluid was lactated Ringer's solution with approximately 200 ml infused before induction and 300 ml in the first five minutes. Immediately after the Dinamap had completed a measurement (time t = 0), thiopentone or propofol was given over twenty seconds through the fast-running intravenous line while cricoid pressure was applied. This was followed by suxamethonium 1.5 mg.kg· l . Laryngoscopy and tracheal intubation were attempted after the next blood pressure measurement (time t = I) and completed before the subsequent Dinamap recording (time t = 2). Anaesthesia was maintained with 50% nitrous oxide in oxygen and 1.0% enflurane. Neuromuscular blockade was maintained with atracurium 0.3 mg.kg· 1 and ventilation controlled to maintain end-tidal carbon dioxide levels of 4.0-4.5% using a carbon dioxide analyser (Normocap, Datex Ltd). Arterial pressure and heart rate were recorded for ten minutes. Obstetricians were allowed to proceed to skin incision at their own pace after the three minute recordings were completed. Induction to delivery (I-D) and uterine incision to delivery (V-D) times were recorded. After delivery of the neonate, an oxytocin infusion (20 units in 500 ml 5% glucose) was commenced and morphine 0.2 mg.kg- I administered. The nitrous oxide concentration was increased to 70% and enflurane decreased to 0.6%. Apgar scores were recorded by a paediatrician who was unaware of the study. The day following surgery, each woman was questioned concerning awareness or the occurrence of dreams during the operation. Statistical comparison between groups employed Student's t-test or Fisher's Exact test as appropriate except for the haemodynamic data. The two sets of printed Dinamap recordings were coded to allow blind analysis. Within each group, changes in blood pressure and pulse were analysed by
repeated measures analysis of variance and the projected least significant difference test. Comparisons of haemodynamic changes between groups were made using two-way repeated measures analysis of variance and Student's t-test. Significant differences were accepted at a P < 0.05. RESULTS
Demographic data are shown in Table 1. There was no difference between the groups with regard to age, weight, height or parity. Gestational age and neonatal birth weight were also similar. TABLE I
Maternal and neonatal demographic data. Mean, with SD in parenthesis. (N = 20)
Thiopentone (N =20)
30.0 (5.4) 62.4 (8.3) 152.9 (8.6)
28.7 (4.5) 62.7 (8.3) 152.9 (6.0)
Propofol Age (yr) Weight (kg) Height (cm) Parity = 0/ > 0 Gestation (weeks) Birth weight (kg)
6114
6114
39.2 (1.0) 3.18 (0.44)
38.6 (1.0) 3.06 (0.32)
Blood Pressure (Table 2, Figure 1). In the propofol group, there were no differences in systolic (SAP), mean (MAP) or diastolic (DAP) pressures after induction (t = 1) compared with baseline (t = 0). There 150
-;,
140
X
-I:i~
130
~
.".."
l: 120
t:
..: y
;:::
.s
~
llO
~
t:
l"t-,
80
:t
c 0
~ 2 .s
70 0
+,. . ,+'. -+ ......
4
6
9
to
Minutes after start of induction
FIGURE 2.-Heart rate changes (mean ± S.E.) after induction with propofol ····0···· or thiopentone - • -. Anaesthesia and Intensive Care. Vol. 18. No. 2. May. 1990
rise in SAP post-intubation (t = 2 v t = 1), 32.1 mmHg (SD 23.7) compared with the propofol group, 17.4 mmHg (SD 23.8), P < 0.05. No other differences were detected between the groups up to ten minutes after induction.
Heart rate (Figure 2). After induction, heart rate rose in both groups (P < 0.01). The propofol group was back to baseline levels by six minutes and the thiopentone group by eight minutes. There was no difference between the groups initially but from six to ten minutes the propofol group had a lower heart rate than the thiopentone group (P < 0.05). Neonatal Apgar scores were similar in the two groups (Table 3). There were no differences in the I-D times which ranged from 4.7 to 15.0 minutes, or the U-D times which were all less than 90 seconds. No patient in either group complained of awareness, either spontaneously or on direct questioning. DISCUSSION Induction of anaesthesia with propofol did not cause more hypotension than thiopentone. Haemodynamic changes in this study differ from those reported in nonobstetric studies. Variations in methodology
178
T. GIN ET AL. TABLE 3 Apgar scores and incision-ta-delivery limes.
I-D time in minutes (SD)
Propofoi Thiopentone
1 min Apgar
5 min Apgar
5-6
7-8
9-10
10.7 (2.6)
o
11.7 (2.0)
2
6 4
14 14
7-8
9-10 19 19
The rise in SAP following intubation (t = 2 may account for some differences but these would generally apply equally to both the v t = 1) was less with propofol than thiopentone, but both were higher than thiopentone and propofol groups. It has been estimated that propofol was 1.6 baseline values (t = 0). A few comparative times more potent than thiopentone. 7 This studies with thiopentone 8,11 have shown less would equate propofol 2.5 mg.kg'l with rise in arterial pressure post-intubation with thiopentone 4 mg.kg,1 and our study may be propofol, but this was partly due to a greater criticised for not using equipotent doses. decrease in arterial pressure post-induction. However, propofol 2 mg.kg- I and thiopentone In the present study, post-induction blood 4 mg.kg' I were equipotent for success of pressures were unchanged in both groups yet induction in unpremedicated patients 5 and the hypertensive response in the propofol propofol 2 mg.kg- I caused more hypotension group was still diminished. Propofol is not than thiopentone 5 mg.kg'l. Other antanalgesic compared with thiopentone l2 comparative studies using a 1:2 ratio have still and this may contribute to the modified found greater hypotension in the propofol response after intubation. group. 1,4,8 Other workers have usually demonstrated Our patients were not premedicated but it that propofol causes very little change in heart has been shown that, compared with rate on induction of anaesthesia. 2-4,6,lo In this thiopentone, hypotension after propofol was study, both groups showed a rise following still greater in unpremedicated patients. 1,4,5 induction which peaked after intubation. This Speed of induction with propofol had little is probably due to the added stimulus of rapid effect on blood pressure changes. 2 Most sequence induction. Heart rate was lower in studies involve a delay after induction to the propofol group from six to ten minutes document haemodynamic changes. despite similar SAP. There are several nonHypotension is usually maximal from two to standardised factors during this period, three minutes after induction. In this study, especially blood volume changes and fluid this effect may have been masked by the administration, so no conclusions can be coinicident administration of drawn. suxamethonium, cricoid pressure and This study used a standard anaesthetic intubation. This agrees with an incidental sequence instead of prolonging induction to finding in another study when document haemodynamic changes. The suxamethonium was administered results may thus be more applicable to clinical immediately after induction for rapid practice. Although we studied obstetric intubation. No difference was noted between patients, the haemodynamic findings may be awake MAP and a post-intubation MAP two relevant to other situations requiring rapid sequence induction. minutes later. 9 Hypotension after propofol may be due Two recent studies comparing thiopentone more to a decreased systemic vascular with propofol for caesarean section have resistance than with thiopentone. 3,lo These shown conflicting haemodynamic results. patients had received 500 ml of Hartmann's One noted similar findings to this study but solution before delivery in anticipation of did not elaborate on this result in the blood loss. This may offset the vasodilatation discussion. 13 Another concluded that in the propofol group and prevent the hypotension was worse in the propofol groupl4 but the fluid administration and intubation development of hypotension. Anaesthesia and Intensive Care. Vol. 18. No. 2. May. 1990
PROPOFOL V THIOPENTONE IN CAESAREAN SECTION
time did not appear to be controlled and the statistical analysis of the results has been criticised. 15 Both groups in this study had satisfactory neonatal Apgar scores at one and five minutes though the Apgar score is an insensitive means of neonatal assessment. Some studies using higher induction doses of propofol and thiopentone have had similar results,13.14 but other studies show lower Apgar scores after propofol. l6 . 17 Neurobehavioural assessment has been judged satisfactory after propofol (2.5 mg.kg- 1) yet other workers have found lower scores after propofol (2.8 mg.kg- 1) compared with thiopentone (5 mg.kg- 1).17 No differences have been detected with umbilical blood gas analysis. 13. 14 The published studies to date show that propofol and thiopentone provide clinically similar, satisfactory maternal anaesthetic conditions but further studies on neonatal assessment appear warranted. During rapid sequence induction of anaesthesia for elective caesarean section, propofol 2 mg.kg- 1 causes less variation in systolic arterial pressure than thiopentone 4 mg.kg- 1. Hypotension is not apparent after propofol and this is probably prevented by the coincident stimulus of rapid sequence induction. The hypertensive response to laryngoscopy and intubation is reduced compared with that using thiopentone.
REFERENCES Mackenzie N, Grant IS. Comparison of the new emulsion formulation of propofol with methohexitone and thiopentone for induction of anaesthesia in day cases. Br J Anaesth 1985; 57:725-731. 2. Rolly G, Versichelen L, Huyghe L, Mungroop H. Effect of speed of injection on induction of anaesthesia using propofoL Br J Anaesth 1985; 57:743-746. 3. Grounds RM, Twigley AJ, Carli F, Whitwam JG, Morgan M. The haemodynamic effects of intravenous induction. Comparison of the effects of thiopentone and propofol. Anaesthesia 1985; 40:735-740. l.
Anaesthesia and Intensive Care. Vol. 18. No. 2. May. 1990
179
4. Fahy LT, van Mourik GA, Utting JE. A comparison of the induction characteristics of thiopentone and propofol (2,6-diisopropyl phenol). Anaesthesia 1985; 40:939-944. 5. McCollum JSC and Dundee JW. Comparison of induction characteristics of four intravenous anaesthetic agents. Anaesthesia 1986; 41 :995-1000. 6. Van Aken H, Meinshausen E, Prien T, BrUssel T, Heinecke A, Lawin P. The influence of fentanyl and tracheal intubation on the hemodynamic effects of anesthesia induction with propofollN 2 0 in humans. Anesthesiology 1988; 68:157-163. 7. Grounds RM, Moore M, Morgan M. The relative potencies of thiopentone and propofol. Eur J Anaesthesiol1986; 3:11-17. 8. Doze VA, Shafer A, White PF. Propofol-nitrous oxide versus thiopental-isoflurane-nitrous oxide for general anesthesia. Anesthesiology 1988; 69:63-71. 9. de Grood PMRM, Harbers JBM, van Egmond J, Crul JF. Anaesthesia for laparoscopy. A comparison of five techniques including propofol, etomidate, thiopentone and isoflurane. Anaesthesia 1987; 42:815-823. 10. Fahmy NR, Alkhouli HM, Sunder N, Smith D, Kelley MM. Diprivan: A new intravenous induction agent. A comparison with thiopental. Anesthesiology 1988; 63:A363. 11. Harris CE, Murray AM, Anderson JM, Grounds RM, Morgan M. Effects of thiopentone, etomidate and propofol on the haemodynamic response to tracheal intubation. Anaesthesia 1988; 43S:32-36. 12. Briggs LP, Dundee JW, Bahar M, Clarke RSJ. Comparison of the effect of diisopropylphenol (ICI 35868) and thiopentone on response to somatic pain. Br J Anaesth 1982; 54:307-311. 13. Valtonen M, Kanto J, Rosenberg P. Comparison of propofol and thiopentone for induction of anaesthesia for elective caesarean section. Anaesthesia 1989; 44:758-762. 14. Moore J, Bill KM, Flynn RJ, McKeating KT, Howard PJ. A comparison between propofol and thiopentone as induction agents in obstetric anaesthesia. Anaesthesia 1989; 44:753-757. 15. Gin T, Gregory MA. Propofol for caesarean section. Anaesthesia 1990; 45: 165. 16. Couper JL, Lombard TP. Comparison of propofol (Diprivan) with thiopentone as induction agent for elective caesarean section. Can J Anaesth 1988; 35:S132. 17. Celleno D, Capogna G, Tomassetti M, Costantino P, Di Feo G, Nisini R. Neurobehavioural effects of propofol on the neon ate following elective caesarean section. Br J Anaesth 1989; 62:649-654. 18. Dailland P, Lirzin JD, Cockshott ID, Jorrot JC, Con se iller C. Placental transfer and neonatal effects of propofol administered during cesarean section. Anesthesiology 1987; 67:A454.
The Haemodynamic Effects of Propofol and Thiopentone for Induction of Caesarean Section T. GIN*, M. A. GREGORyt AND T. E. OH*
Department oj Anaesthesia and Intensive Care, Prince oj Wales Hospital, The Chinese University oj Hong Kong, Shatin, N. T., Hong Kong SUMMARY Forty Chinese women jor elective caesarean section received either propojol 2 mgkg· 1 or thiopentone 4 mg.kgl jor induction ojgeneral anaesthesia. Systolic, mean and diastolic arterial pressures and heart rate were recorded non-invasively every minute jor ten minutes. Postinduction arterial pressures were similar to pre-induction values with no differences between thiopentone and propojol. Following intubation, the rise in systolic arterial pressure was greater in the thiopentone group, 32.1 mmHg (SD 23.7) compared with the propojol group, 17.4 mmHg (SD 23.8), (P < 0.05). In the thiopentone group, arterial pressures were slower in returning to baseline values. Heart rate was initially elevated in both groups to the same degree. At caesarean section, induction with propojol causes less variation in arterial pressure than thiopentone. Hypotension is probably prevented by the coincident stimulus oj rapid sequence induction. Neonatal Apgar scores were similar between the two groups. Key Words: ANAESTHESIA, ANESTHESIA; obstetrical; ANAESTHETICS, ANESTHETICS, INTRA VENOUS; propofol, thiopentone.
Recovery after induction of anaesthesia with propofol is more rapid than thiopentone 1 and this could be advantageous for caesarean section patients who are still at risk of aspiration in the postoperative period. However, following induction doses of propofol, a fall in systolic arterial pressure has been widely reported. 2- 6 This could be detrimental to placental perfusion and restrict the use ofpropofol in obstetrics. This study set out to compare the haemodynamic effects of propofol to those of thiopentone, as part of a rapid sequence induction of anaesthesia for elective caesarean section.
*8.Se .. F.F.A.R.C.S., F.F.A.R.A.C.S., Lecturer. tF.F.A.R.C.S .. Lecturer. tF.F.A.R.C.S .. F.F.A. R.A.C.S., F.F.A.R.A.C.S. (Int. Care). Professor. Address for Reprints: Dr. T. Gin, Department of Anaesthesia and Intensive Care. Prince of Wales Hospital. The Chinese University of Hong Kong, Shatin. N.T .. Hong Kong Accepted for publication January 12, 1990
Anaesthesia and Intensive Care, Vol. 18, No. 2, May, 1990
MATERIALS AND METHODS After approval by the Chinese University Ethics Committee, forty ASA grade 1 Chinese women undergoing elective caesarean section at term gave their written informed consent to be studied. There was no evidence of pregnancy-induced hypertension, preeclampsia or overt supine hypotension. All patients were given ranitidine 150 mg orally the night before and again two hours before surgery. Mothers were transported to theatre lying on their sides and a 15 degree left lateral tilt was maintained on the operating table. Sodium citrate 0.3M 30 ml was given orally, five minutes before induction of anaesthesia. The women were randomly allocated to receive thiopentone 4 mg.kg- I or propofol 2 mg.kg- I . Drugs and fluid were administered through a cannula in the left forearm while blood pressure was monitored on the right arm with an automatic oscillotonometer (Dinamap 1846SXP,
176
T. GIN ET AL.
Critikon) with the appropriate size cuff. The machine was programmed to cycle every minute and the output was recorded on the attached printer. An electrocardiogram was continuously monitored and the patient preoxygenated for at least three minutes. The initial intravenous fluid was lactated Ringer's solution with approximately 200 ml infused before induction and 300 ml in the first five minutes. Immediately after the Dinamap had completed a measurement (time t = 0), thiopentone or propofol was given over twenty seconds through the fast-running intravenous line while cricoid pressure was applied. This was followed by suxamethonium 1.5 mg.kg· l . Laryngoscopy and tracheal intubation were attempted after the next blood pressure measurement (time t = I) and completed before the subsequent Dinamap recording (time t = 2). Anaesthesia was maintained with 50% nitrous oxide in oxygen and 1.0% enflurane. Neuromuscular blockade was maintained with atracurium 0.3 mg.kg· 1 and ventilation controlled to maintain end-tidal carbon dioxide levels of 4.0-4.5% using a carbon dioxide analyser (Normocap, Datex Ltd). Arterial pressure and heart rate were recorded for ten minutes. Obstetricians were allowed to proceed to skin incision at their own pace after the three minute recordings were completed. Induction to delivery (I-D) and uterine incision to delivery (V-D) times were recorded. After delivery of the neonate, an oxytocin infusion (20 units in 500 ml 5% glucose) was commenced and morphine 0.2 mg.kg- I administered. The nitrous oxide concentration was increased to 70% and enflurane decreased to 0.6%. Apgar scores were recorded by a paediatrician who was unaware of the study. The day following surgery, each woman was questioned concerning awareness or the occurrence of dreams during the operation. Statistical comparison between groups employed Student's t-test or Fisher's Exact test as appropriate except for the haemodynamic data. The two sets of printed Dinamap recordings were coded to allow blind analysis. Within each group, changes in blood pressure and pulse were analysed by
repeated measures analysis of variance and the projected least significant difference test. Comparisons of haemodynamic changes between groups were made using two-way repeated measures analysis of variance and Student's t-test. Significant differences were accepted at a P < 0.05. RESULTS
Demographic data are shown in Table 1. There was no difference between the groups with regard to age, weight, height or parity. Gestational age and neonatal birth weight were also similar. TABLE I
Maternal and neonatal demographic data. Mean, with SD in parenthesis. (N = 20)
Thiopentone (N =20)
30.0 (5.4) 62.4 (8.3) 152.9 (8.6)
28.7 (4.5) 62.7 (8.3) 152.9 (6.0)
Propofol Age (yr) Weight (kg) Height (cm) Parity = 0/ > 0 Gestation (weeks) Birth weight (kg)
6114
6114
39.2 (1.0) 3.18 (0.44)
38.6 (1.0) 3.06 (0.32)
Blood Pressure (Table 2, Figure 1). In the propofol group, there were no differences in systolic (SAP), mean (MAP) or diastolic (DAP) pressures after induction (t = 1) compared with baseline (t = 0). There 150
-;,
140
X
-I:i~
130
~
.".."
l: 120
t:
..: y
;:::
.s
~
llO
~
t:
l"t-,
80
:t
c 0
~ 2 .s
70 0
+,. . ,+'. -+ ......
4
6
9
to
Minutes after start of induction
FIGURE 2.-Heart rate changes (mean ± S.E.) after induction with propofol ····0···· or thiopentone - • -. Anaesthesia and Intensive Care. Vol. 18. No. 2. May. 1990
rise in SAP post-intubation (t = 2 v t = 1), 32.1 mmHg (SD 23.7) compared with the propofol group, 17.4 mmHg (SD 23.8), P < 0.05. No other differences were detected between the groups up to ten minutes after induction.
Heart rate (Figure 2). After induction, heart rate rose in both groups (P < 0.01). The propofol group was back to baseline levels by six minutes and the thiopentone group by eight minutes. There was no difference between the groups initially but from six to ten minutes the propofol group had a lower heart rate than the thiopentone group (P < 0.05). Neonatal Apgar scores were similar in the two groups (Table 3). There were no differences in the I-D times which ranged from 4.7 to 15.0 minutes, or the U-D times which were all less than 90 seconds. No patient in either group complained of awareness, either spontaneously or on direct questioning. DISCUSSION Induction of anaesthesia with propofol did not cause more hypotension than thiopentone. Haemodynamic changes in this study differ from those reported in nonobstetric studies. Variations in methodology
178
T. GIN ET AL. TABLE 3 Apgar scores and incision-ta-delivery limes.
I-D time in minutes (SD)
Propofoi Thiopentone
1 min Apgar
5 min Apgar
5-6
7-8
9-10
10.7 (2.6)
o
11.7 (2.0)
2
6 4
14 14
7-8
9-10 19 19
The rise in SAP following intubation (t = 2 may account for some differences but these would generally apply equally to both the v t = 1) was less with propofol than thiopentone, but both were higher than thiopentone and propofol groups. It has been estimated that propofol was 1.6 baseline values (t = 0). A few comparative times more potent than thiopentone. 7 This studies with thiopentone 8,11 have shown less would equate propofol 2.5 mg.kg'l with rise in arterial pressure post-intubation with thiopentone 4 mg.kg,1 and our study may be propofol, but this was partly due to a greater criticised for not using equipotent doses. decrease in arterial pressure post-induction. However, propofol 2 mg.kg- I and thiopentone In the present study, post-induction blood 4 mg.kg' I were equipotent for success of pressures were unchanged in both groups yet induction in unpremedicated patients 5 and the hypertensive response in the propofol propofol 2 mg.kg- I caused more hypotension group was still diminished. Propofol is not than thiopentone 5 mg.kg'l. Other antanalgesic compared with thiopentone l2 comparative studies using a 1:2 ratio have still and this may contribute to the modified found greater hypotension in the propofol response after intubation. group. 1,4,8 Other workers have usually demonstrated Our patients were not premedicated but it that propofol causes very little change in heart has been shown that, compared with rate on induction of anaesthesia. 2-4,6,lo In this thiopentone, hypotension after propofol was study, both groups showed a rise following still greater in unpremedicated patients. 1,4,5 induction which peaked after intubation. This Speed of induction with propofol had little is probably due to the added stimulus of rapid effect on blood pressure changes. 2 Most sequence induction. Heart rate was lower in studies involve a delay after induction to the propofol group from six to ten minutes document haemodynamic changes. despite similar SAP. There are several nonHypotension is usually maximal from two to standardised factors during this period, three minutes after induction. In this study, especially blood volume changes and fluid this effect may have been masked by the administration, so no conclusions can be coinicident administration of drawn. suxamethonium, cricoid pressure and This study used a standard anaesthetic intubation. This agrees with an incidental sequence instead of prolonging induction to finding in another study when document haemodynamic changes. The suxamethonium was administered results may thus be more applicable to clinical immediately after induction for rapid practice. Although we studied obstetric intubation. No difference was noted between patients, the haemodynamic findings may be awake MAP and a post-intubation MAP two relevant to other situations requiring rapid sequence induction. minutes later. 9 Hypotension after propofol may be due Two recent studies comparing thiopentone more to a decreased systemic vascular with propofol for caesarean section have resistance than with thiopentone. 3,lo These shown conflicting haemodynamic results. patients had received 500 ml of Hartmann's One noted similar findings to this study but solution before delivery in anticipation of did not elaborate on this result in the blood loss. This may offset the vasodilatation discussion. 13 Another concluded that in the propofol group and prevent the hypotension was worse in the propofol groupl4 but the fluid administration and intubation development of hypotension. Anaesthesia and Intensive Care. Vol. 18. No. 2. May. 1990
PROPOFOL V THIOPENTONE IN CAESAREAN SECTION
time did not appear to be controlled and the statistical analysis of the results has been criticised. 15 Both groups in this study had satisfactory neonatal Apgar scores at one and five minutes though the Apgar score is an insensitive means of neonatal assessment. Some studies using higher induction doses of propofol and thiopentone have had similar results,13.14 but other studies show lower Apgar scores after propofol. l6 . 17 Neurobehavioural assessment has been judged satisfactory after propofol (2.5 mg.kg- 1) yet other workers have found lower scores after propofol (2.8 mg.kg- 1) compared with thiopentone (5 mg.kg- 1).17 No differences have been detected with umbilical blood gas analysis. 13. 14 The published studies to date show that propofol and thiopentone provide clinically similar, satisfactory maternal anaesthetic conditions but further studies on neonatal assessment appear warranted. During rapid sequence induction of anaesthesia for elective caesarean section, propofol 2 mg.kg- 1 causes less variation in systolic arterial pressure than thiopentone 4 mg.kg- 1. Hypotension is not apparent after propofol and this is probably prevented by the coincident stimulus of rapid sequence induction. The hypertensive response to laryngoscopy and intubation is reduced compared with that using thiopentone.
REFERENCES Mackenzie N, Grant IS. Comparison of the new emulsion formulation of propofol with methohexitone and thiopentone for induction of anaesthesia in day cases. Br J Anaesth 1985; 57:725-731. 2. Rolly G, Versichelen L, Huyghe L, Mungroop H. Effect of speed of injection on induction of anaesthesia using propofoL Br J Anaesth 1985; 57:743-746. 3. Grounds RM, Twigley AJ, Carli F, Whitwam JG, Morgan M. The haemodynamic effects of intravenous induction. Comparison of the effects of thiopentone and propofol. Anaesthesia 1985; 40:735-740. l.
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