Anaesthesia, 199 I , Volume 46, pages 20-23
Propofol for induction and maintenance of anaesthesia at Caesarean section A comparison with thiopentone/enflurane
G. YAU, T. GIN, M. C. EWART, C. F. KOTUR, R. K. W. LEUNG
AND
T. E. OH
Summary A propofol infusion regimen and a standard general anaesthetic were compared in 40 Chinese women undergoing elective Caesarean section. Twenty patients received propofol2 mglkg for induction of anaesthesia followed by propofol6 mglkglhour, while 20 patients received thiopentone 4 mglkg with enjurane I % for maintenance of anaesthesia. All patients were given atracurium and their lungs ventilated with nitrous oxide 50% in oxygen until delivery of the neonate. The hypertensive response after intubation was of' shorter duration in the propofol group compared with the thiopentone group. Induction to delivery times ranged from 5 to 14 minutes and neonates from both groups had similar and satisfactory Apgar scores, Neurologic and Adaptive Capacity Scores and umbilical cord blood gas analysis. However, a prolonged propofol infusion time before delivery may cause lower Neurologic and Adaptive Capacity Scores. There were no differences in maternal recovery times or psychomotor performance. Key words
,4naesthesio; obstetric. Anaesthetics, intravenous; propofol. Anaesthetic techniques; intravenous.
Recovery from propofol infusions is rapid'-4 and several groups have evaluated this technique for anaesthesia during elective Caesarean ~ e c t i o n .It~ .was ~ postulated that, as well as rapid maternal recovery, the neonate may also recover quickly after delivery. However, placental transfer of propofol is rapid' and infusion techniques deliver a large dose of drug to the fetus, especially if induction to delivery times are prolonged. A preliminary study with 10 patients per group found that a propofol infusion regimen with 100% oxygen was unsatisfactory, partly because analgesia was not provided before delivery and a propofol infusion with nitrous oxide was more promising.6 In this study, we compared a propofol infusion plus nitrous oxide with a thiopentone, enflurane and nitrous oxide general anaesthetic. Method The protocol was approved by the Research Ethics Committee of the Chinese University Faculty of Medicine and informed consent obtained from all patients. Forty ASA 1 Chinese women undergoing elective Caesarean
section for a normal, singleton pregnancy were randomly assigned to a thiopentone or propofol group. Oral rantidine 150 mg was given the night before, and again on the morning of surgery. The patients were transported to the operating theatre in the lateral position and a 15" left lateral tilt was maintained on the operating table. Oral sodium citrate 0.3 M 30 ml was given 15 minutes before induction of anaesthesia. Routine monitoring included pulse oximetry, end-tidal carbon dioxide concentration (Normocap, Datex), electrocardiogram and arterial blood pressure (Dinamap 1846SXP, Critikon Inc). The lungs of each patient were pre-oxygenated for 3 minutes. Anaesthesia was induced, after a baseline arterial blood pressure was recorded, with either thiopentone 4 mg/kg or propofol 2 mg/kg over 20 seconds followed by suxamethonium 1.5 mg/kg. Laryngoscopy followed the next Dinamap recording at one minute and tracheal intubation was accomplished before the second minute recordings. Cricoid pressure was applied from the beginning of the induction sequence until the trachea was intubated and the cuff tested for leaks. The lungs of both groups were ventilated with nitrous oxide 50% in oxygen. In the propofol group, an
G . Yau, MB, BS, FFARCS, T. Gin, MB, ChB, BSc, FFARCS, FFARACS, Lecturers, C.F. Kotur, MB, BS, DA, FFARCS, Honorary Clinical Lecturer, T.E. Oh, MB, BS, FFARCS, FFARACS, Professor, Department of Anaesthesia and Intensive Care, R.K.W. Leung, MB, BS, MRCP, Department of Paediatrics, Prince of Wales Hospital, Chinese University of Hong Kong, Shatin, Hong Kong, M.C. Ewart, MB, BS, FFARCS, Senior Registrar, Hammersmith Hospital, Du Cane Road, London W 12 ONN. Accepted 25 June 1990.
+
0003-2409/91 /Ol0020 04 $03.00/0
@ 1991 The Association of Anaesthetists of Gt Britain and Ireland
20
21
Propofol for Cuesurean section infusion of propofol6 mg/kg/hour was started immediately after the induction dose while the thiopentone group received enflurane 1 % when controlled ventilation was started. Neuromuscular block was continued with atracurium 0.5 mg/kg and ventilation was controlled to maintain end-tidal carbon dioxide concentrations of 4.0-4.5%. A 500-ml infusion of compound sodium lactate solution was given over the first 10 minutes. Systolic, mean and diastolic arterial pressures and heart rate were recorded every minute for the first 20 minutes. The nitrous oxide concentration was increased to 70% in oxygen for all patients after delivery of the infant and, in the thiopentone group, the enflurane concentration was reduced to 0.5%. An infusion of oxytocin (20 units in 500 ml 5% glucose) was started and morphine 0.2 mg/kg was given intravenously. The propofol infusion o r the enflurane was discontinued at the start of skin suture and nitrous oxide stopped 2 minutes later. Residual neuromuscular block was antagonised with neostigmine 2.5 mg and atropine 1.2 mg. Maternal recovery was timed from cessation of the propofol or enflurane and assessed by one investigator who was blind to the anaesthetic technique. The time that each patient took to open her eyes to command and the time to give her correct date of birth were recorded. Psychomotor recovery was assessed by the patient’s ability to perform a modified ‘postbox’ test* in the left lateral position before operation and at 30 and 60 minutes after operation. The number of shapes that the patient could complete in one minute was recorded and the best of three attempts was accepted. All women were interviewed the next day about awareness. Umbilical venous and arterial blood gas analysis were performed at delivery. All neonates were assessed by one paediatrician who was unaware of the anaesthetic technique. Apgar scores at one and five minutes, and Neurologic and Adaptive Capacity Scores (NACS)y at 15 minutes, 2 and 24 hours were recorded. Student’s t-test was used to compare demographic data and umbilical blood gas analysis while haeniodynamic data were analysed by repeated measures analysis of variance. Maternal recovery, Apgar scores and NACS scores were compared using the Mann-Whitney test. Kendall Rank correlation was used to compare maternal recovery with anaesthetic duration and neonatal scores with induction to delivery times. Statistical significance was accepted when p < 0.05.
I20r
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Time after induction (minutes)
Mean arterial pressure (SEM) after induction of and propofol ...n... anaesthesia in the thiopentone -0groups.* p < 0.05 between groups. Fig. 1.
group but not in the thiopentone group. No patients complained of pain on injection and intubation conditions were satisfactory in all cases. The normal size adult blood pressure cuff was appropriate for all patients, and there were no significant changes in systolic and mean arterial pressures immediately arter induction of anaesthesia compared with awake values. These increased after intubation in both groups (p < 0.01) and returned to baseline levels by 4 minutes in the propofol group and 5 minutes in the thiopentone group (Fig. I). Maternal heart rate increased in both groups after induction of anaesthesia (p < 0.01) and returned to baseline values by 7 minutes in the propofol group and 8 minutes in the thiopentone group (Fig. 2 ) . Total anaesthetic time was similar between groups, and ranged from 28 to 65 minutes. There were no differences between groups in the time to eye opening, time to correct date of birth or postbox scores. Recovery times were not correlated to total anaesthetic time (Table 2), and no patients complained of nausea or vomited.
Results
There were no demographic differences between the groups (Table 1). The quality of induction was difficult to assess because of the nature of rapid sequence induction. Lacrimation was noted in four patients in the propofol Table 1. Demographic and anaesthetic data, mean (SD).
Thiopentone Age; years
Height; cm Weight; kg
Gestation; weeks I-D time; minutes Birth weight; kg
Anaesthetic time; minutes
30.6 149 65.4 38.9 12.2
Propofol
29.4 (4.3) I52 (6.9) (9.4) 65.8 (9.3) (1.3) 39.1 (1.5) (2.6) 10.8 (2.1) 3.28 (0.43) 3.22 (0.62) 42.0 (9.2) 48.2 (9.4) (5.1)
(12.1)
701 0
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Fig. 2. Mean (SEM) maternal heart rate after induction of anaesthesia in the thopentone -0and propofol -.Dgroups
22
G . Yau et al.
Table 2. Maternal recovery times and postbox scores, mean (SD).
Table 4. Apgar scores and neurologic and adaptive capacity scores
(NACS), median (range). Eye opening; minutes Date of birth; minutes Postbox scores after 30 minutes compared with before operation Postbox scores after 60 minutes compared with before operation
Thiopentone
Propofol
7.56 (3.0) 9.69 (3.2)
7.03 (2.5) 9.12 (2.51
0.53 (0.27)
0.63 (0.15)
0.83 (0.24)
0.89 0.19)
There were no differences in gestation or birth weight between the groups. Induction to delivery times were similar and uterine incision to delivery times were all less than 90 seconds. Umbilical blood gas analysis, neonatal Apgar scores and NACS were satisfactory and similar between groups (Tables 3 and 4). Apgar scores and NACS were not related to induction-to-delivery times in the thiopentone group but NACS at 2 hours were slightly lower in the propofol group with increasing induction-to-delivery time (p < 0.05) (Fig. 3). Measured blood loss ranged from 200 to 1000 ml with n o difference between groups. There were no anaesthetic o r obstetric complications and no patients complained of awareness during anaesthesia.
Discussion The two anaesthetic techniques gave clinically satisfactory and similar results. There was no hypotension after induction of anaesthesia. The peak decrease in arterial blood pressure after propofol usually occurs at 2 to 3 minutes and patients in this study were subjected to the coincident stimuli of cricoid pressure and intubation. Arterial pressures, after tracheal intubation, returned to baseline levels more rapidly in the propofol group. Propofol attenuates the cardiovascular response to laryngoscopy and intubation more than thiopentone.l.Lo.L1 Variations in arterial pressure and heart rate during Caesarean section are influenced more by the rapid circulatory volume changes during surgery and delivery than the anaesthetic technique. However, during other surgical procedures, the cardiovascular changes during maintenance of anaesthesia by propofol infusion have been comparable with the use of volatile agent^.',^,^ Maternal recovery was similar between groups although our previous study showed that a similar propofol group had slightly faster recovery times6 The anaesthetic technique differed slightly in this study since nitrous oxide was
Apgar 1 minute Apgar 5 minutes NACS 15 minutes NACS 2 hours NACS 24 hours
Thiopentone
Propofol
9 (5-10) 10 (8-10) 32 (25-34) 33 (23-35) 33 (30-37)
9 (5-10) 10 (8-10) 32 (21-36) 33.5 (25-36) 34.5 (30-37)
discontinued 2 minutes after the propofol or enflurane, while the earlier study stopped all anaesthetic agents simultaneously. Propofol, after major operations, has not always shown faster recovery when compared with a volatile agent.' No patients complained of awareness in this study, but with our sample size of 20 there is still a 5% probability that the incidence of awareness is as high as 14%. However, a previous study using the same propofol infusion rate measured propofol concentrations during anaesthesia and recovery, and in every patient propofol concentrations were higher during anaesthesia than at the time of eye opening.6 Inhalation anaesthetic requirements are decreased in pregnancy but this has not been investigated during intravenous anaesthesia. Minimum alveolar concentrations for inhalational agents are reduced in animal studies with pregnant ewest2 and rats,13 which may be related to increased levels of circulating e n d 0 r ~ h i n s . IThere ~ is, in pregnancy, decreased plasma binding of many drugs with increased free levels1sbut there are no data for propofol. Comparative studies with thiopentone and propofol during induction of anaesthesia for Caesarean section have shown variable neonatal outcome. Apgar scores were ~ i r n i l a r ' l o~rl lower ~ ~ ~ ~after p r o p ~ f o l . l * .Neurobehavioural '~ assessment was satisfactory after p r ~ p o f o l ,but ~ other workers reported lower scores after propofol (2.8 mg/kg) compared with thiopentone (5 mg/kg).19 In this study, NACS in the propofol group were slightly lower with longer I-D times. A longer infusion time before delivery is likely to cause higher neonatal levels at delivery, and lower NACS have been correlated with higher neonatal levels of propofoLZ0However, small differences in NACS have not been shown to have any clinical significance. A propofol infusion coupled with nitrous oxide gave satisfactory induction and maintenance of anaesthesia. Haemodynamic changes at induction were less variable in the propofol group, compared with a thiopentone, nitrous oxide, enflurane technique, and neonatal effects were similar when infusion time before delivery ranged from 7 to
Table 3. Umbilical venous and arterial blood gas analysis, mean (SD).
Thiopentone Umbilical venous pH Umbilical venous Pco, (kPa) Umbilical venous Po, (kPa) Umbilical venous BE Umbilical arterial pH Umbilical arterial Pco, (kPa) Umbilical arterial Po, (kPa) Umbilical arterial BE
7.327 5.63 4.35 -3.0 7.271 6.86 2.44 -3.0
(0.028) (0.65) (1.0) (1.9) (0.038) (1.0) (0.81) (2.6)
Propofol 7.331 (0.056) 5.89 (0.77) 3.80 (0.94) -2.8 (1.7) 7.262 (0.034) 7.10 (0.91) 2.19 (0.71) -2.8 (2.2)
Propofol for Caesarean section
401
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1 1 I 1 1 1 1 10 12 14 16 Induction t o delivery t i m e (minutes) I
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Fig. 3. Induction to delivery time (minutes) against neurologic and adaptive capacity scores 2 hours after delivery, 0 , thiopentone group; 0, propofol group.
14 minutes. However, a prolonged infusion time before delivery may cause slightly lower NACS scores. Maternal recovery was rapid and similar in both groups. We believe that maintenance of anaesthesia with inhalation agents remains the standard for obstetric general anaesthesia.
Acknowledgments
We thank Professor A. Chang, Chairman, Department of Obstetrics and Gynaecology for permitting this study on patients in his department, Mrs V. K o t u r for her assistance and ICI Pharmaceuticals for their support. References 1. DOZEVA, SHAFERA, WHITE PF. Propofol-nitrous oxide
oxide for general versus thiopental-isoflurane-nitrous anesthesia. Anesthesiology 1988; 6 9 63-71. JBM, VAN EGMOND J, CRULJF. 2. DE GROODPMRM, HARBERS Anaesthesia for laparoscopy. A comparison of five techniques including propofol, etomidate, thiopentone and isoflurane. Anaeslhesia 1987; 42: 815-23. 3. ZUURMONVWWA, VAN LEEUWENL, HELMERSJHJH. Recovery from propofol infusion as the main agent for outpatient arthroscopy. A comparison with isoflurane. Anaesthesia 1987; 4 2 356-9.
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4. SEARJW, SHAWI, WOLFA, KAYNH. Infusions of propofol to supplement nitrous oxide-oxygen for the maintenance of anaesthesia. A comparison with halothane. Anuesihesia 1988; 43 (SUPPI.):18-22. 5. DAILLAND P, COCKSHOTT ID, LIRZINJD, JACQUINOT P, JORROT JC, DEVERYJ, HARMEYJ-L, CONSEILLERC. Intravenous propofol during caesarean section: placental transfer, concentrations in breast milk, and neonatal effects. A preliminary study. Anesthesiology 1989; 71: 827-34. 6. GREGORY MA, GIN T, YAU G, LEUNGRKW, CHANK , OH TE. Propofol infusion anaesthesia for Caesarean section. Canadian Journal of Anaesthesia 1990; 37: 5 14-20. MA, CHANK, OH TE. Maternal and fetal 7. GIN T, GREGORY levels of propofol at Caesarean section. Anaesthesia and Intensive Care 1990; 18: 1804. 8. CRAIGJ, COOPERGM, SEARJW. Recovery from day-case anaesthesia. Comparison between methohexitone, Althesin and etomidate. British Journal ofAnaesthesia 1982; 5 4 447-51. 9. AMIEL-TISON C, BARRIERG, SHNIDERSM, LEVINSONG, HUGHESSC, STEFANISJ. A new neurologic and adaptive capacity scoring system for evaluating obstetric medications in full-term newborns. Anesthesiology 1982; 56: 340-50. 10. HARRISCE, MURRAYAM, ANDERSON JM, GROUNDSRM, MORGAN M. Effects of thiopentone, etomidate and propofol on the haemodynamic response to tracheal intubation. Anaesthesia 1988; 4 3 (Suppl.): 32-6. 11. GINT, GREGORY MA, OH TE. The haemodynamic effects of propofol and thiopentone for induction of Caesarean section. Anaesthesia and Intensive Care 1990; 18: 175-9. 12. PALAHNIUK RJ, SHNIDERSM, EGER, 11, EI. Pregnancy decreases the requirement for inhaled anesthetic agents. Anesthesiology 1974; 41: 82-3. 13. STROUTCD, NAHRWOLD ML. Halothane requirement during pregnancy and lactation in rats. Anesthesiology 1981; 5 5 322-3. 14. GINTZLER AR. Endorphin-mediated increases in pain threshold during pregnancy. Science 1980; 210 193-5. E, CREMAA. Plasma protein binding of drugs in 15. PERUCCA pregnancy. Clinical Pharrnacokinetics 1982; 7: 336-52. P. Comparison of 16. VALTONEN M, KANTO J, ROSENBERG propofol and thiopentone for induction of anaesthesia for elective Caesarean section Anaesthesia 1989; 44: 758-62. KT, HOWARD 17. MOOREJ, BILLKM, FLY” RJ, MCKEATING PJ. A comparison between propofol and thiopentone as induction agents in obstetric anaesthesia. Anaesthesia 1989; 4 4 753-7. 18. COUPERJL, LOMBARD TP. Comparison of propofol (Diprivan) with thiopentone as induction agent for elective Caesarean section. Canadian Journal of Anaesthesia 1988; 35: S132. 19. CELLENO D, CAPOGNA, G, TOMASSETTI M, COSTANTINO P, D1 FEOG, NISINIR. Neurobehavioural effects of propofol on the neonate following elective Caesarean section. British Journal of Anaesihesiu 1989; 6 2 649-54. MA, KOTURCF. Recovery 20. GINT, YAUG, CHANK, GREGORY from propofol infusion anaesthesia for Caesarean section. Neiiroscience Letters (Suppl.) 1990; 37: S44.
Propofol for induction and maintenance of anaesthesia at Caesarean section A comparison with thiopentone/enflurane
G. YAU, T. GIN, M. C. EWART, C. F. KOTUR, R. K. W. LEUNG
AND
T. E. OH
Summary A propofol infusion regimen and a standard general anaesthetic were compared in 40 Chinese women undergoing elective Caesarean section. Twenty patients received propofol2 mglkg for induction of anaesthesia followed by propofol6 mglkglhour, while 20 patients received thiopentone 4 mglkg with enjurane I % for maintenance of anaesthesia. All patients were given atracurium and their lungs ventilated with nitrous oxide 50% in oxygen until delivery of the neonate. The hypertensive response after intubation was of' shorter duration in the propofol group compared with the thiopentone group. Induction to delivery times ranged from 5 to 14 minutes and neonates from both groups had similar and satisfactory Apgar scores, Neurologic and Adaptive Capacity Scores and umbilical cord blood gas analysis. However, a prolonged propofol infusion time before delivery may cause lower Neurologic and Adaptive Capacity Scores. There were no differences in maternal recovery times or psychomotor performance. Key words
,4naesthesio; obstetric. Anaesthetics, intravenous; propofol. Anaesthetic techniques; intravenous.
Recovery from propofol infusions is rapid'-4 and several groups have evaluated this technique for anaesthesia during elective Caesarean ~ e c t i o n .It~ .was ~ postulated that, as well as rapid maternal recovery, the neonate may also recover quickly after delivery. However, placental transfer of propofol is rapid' and infusion techniques deliver a large dose of drug to the fetus, especially if induction to delivery times are prolonged. A preliminary study with 10 patients per group found that a propofol infusion regimen with 100% oxygen was unsatisfactory, partly because analgesia was not provided before delivery and a propofol infusion with nitrous oxide was more promising.6 In this study, we compared a propofol infusion plus nitrous oxide with a thiopentone, enflurane and nitrous oxide general anaesthetic. Method The protocol was approved by the Research Ethics Committee of the Chinese University Faculty of Medicine and informed consent obtained from all patients. Forty ASA 1 Chinese women undergoing elective Caesarean
section for a normal, singleton pregnancy were randomly assigned to a thiopentone or propofol group. Oral rantidine 150 mg was given the night before, and again on the morning of surgery. The patients were transported to the operating theatre in the lateral position and a 15" left lateral tilt was maintained on the operating table. Oral sodium citrate 0.3 M 30 ml was given 15 minutes before induction of anaesthesia. Routine monitoring included pulse oximetry, end-tidal carbon dioxide concentration (Normocap, Datex), electrocardiogram and arterial blood pressure (Dinamap 1846SXP, Critikon Inc). The lungs of each patient were pre-oxygenated for 3 minutes. Anaesthesia was induced, after a baseline arterial blood pressure was recorded, with either thiopentone 4 mg/kg or propofol 2 mg/kg over 20 seconds followed by suxamethonium 1.5 mg/kg. Laryngoscopy followed the next Dinamap recording at one minute and tracheal intubation was accomplished before the second minute recordings. Cricoid pressure was applied from the beginning of the induction sequence until the trachea was intubated and the cuff tested for leaks. The lungs of both groups were ventilated with nitrous oxide 50% in oxygen. In the propofol group, an
G . Yau, MB, BS, FFARCS, T. Gin, MB, ChB, BSc, FFARCS, FFARACS, Lecturers, C.F. Kotur, MB, BS, DA, FFARCS, Honorary Clinical Lecturer, T.E. Oh, MB, BS, FFARCS, FFARACS, Professor, Department of Anaesthesia and Intensive Care, R.K.W. Leung, MB, BS, MRCP, Department of Paediatrics, Prince of Wales Hospital, Chinese University of Hong Kong, Shatin, Hong Kong, M.C. Ewart, MB, BS, FFARCS, Senior Registrar, Hammersmith Hospital, Du Cane Road, London W 12 ONN. Accepted 25 June 1990.
+
0003-2409/91 /Ol0020 04 $03.00/0
@ 1991 The Association of Anaesthetists of Gt Britain and Ireland
20
21
Propofol for Cuesurean section infusion of propofol6 mg/kg/hour was started immediately after the induction dose while the thiopentone group received enflurane 1 % when controlled ventilation was started. Neuromuscular block was continued with atracurium 0.5 mg/kg and ventilation was controlled to maintain end-tidal carbon dioxide concentrations of 4.0-4.5%. A 500-ml infusion of compound sodium lactate solution was given over the first 10 minutes. Systolic, mean and diastolic arterial pressures and heart rate were recorded every minute for the first 20 minutes. The nitrous oxide concentration was increased to 70% in oxygen for all patients after delivery of the infant and, in the thiopentone group, the enflurane concentration was reduced to 0.5%. An infusion of oxytocin (20 units in 500 ml 5% glucose) was started and morphine 0.2 mg/kg was given intravenously. The propofol infusion o r the enflurane was discontinued at the start of skin suture and nitrous oxide stopped 2 minutes later. Residual neuromuscular block was antagonised with neostigmine 2.5 mg and atropine 1.2 mg. Maternal recovery was timed from cessation of the propofol or enflurane and assessed by one investigator who was blind to the anaesthetic technique. The time that each patient took to open her eyes to command and the time to give her correct date of birth were recorded. Psychomotor recovery was assessed by the patient’s ability to perform a modified ‘postbox’ test* in the left lateral position before operation and at 30 and 60 minutes after operation. The number of shapes that the patient could complete in one minute was recorded and the best of three attempts was accepted. All women were interviewed the next day about awareness. Umbilical venous and arterial blood gas analysis were performed at delivery. All neonates were assessed by one paediatrician who was unaware of the anaesthetic technique. Apgar scores at one and five minutes, and Neurologic and Adaptive Capacity Scores (NACS)y at 15 minutes, 2 and 24 hours were recorded. Student’s t-test was used to compare demographic data and umbilical blood gas analysis while haeniodynamic data were analysed by repeated measures analysis of variance. Maternal recovery, Apgar scores and NACS scores were compared using the Mann-Whitney test. Kendall Rank correlation was used to compare maternal recovery with anaesthetic duration and neonatal scores with induction to delivery times. Statistical significance was accepted when p < 0.05.
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Time after induction (minutes)
Mean arterial pressure (SEM) after induction of and propofol ...n... anaesthesia in the thiopentone -0groups.* p < 0.05 between groups. Fig. 1.
group but not in the thiopentone group. No patients complained of pain on injection and intubation conditions were satisfactory in all cases. The normal size adult blood pressure cuff was appropriate for all patients, and there were no significant changes in systolic and mean arterial pressures immediately arter induction of anaesthesia compared with awake values. These increased after intubation in both groups (p < 0.01) and returned to baseline levels by 4 minutes in the propofol group and 5 minutes in the thiopentone group (Fig. I). Maternal heart rate increased in both groups after induction of anaesthesia (p < 0.01) and returned to baseline values by 7 minutes in the propofol group and 8 minutes in the thiopentone group (Fig. 2 ) . Total anaesthetic time was similar between groups, and ranged from 28 to 65 minutes. There were no differences between groups in the time to eye opening, time to correct date of birth or postbox scores. Recovery times were not correlated to total anaesthetic time (Table 2), and no patients complained of nausea or vomited.
Results
There were no demographic differences between the groups (Table 1). The quality of induction was difficult to assess because of the nature of rapid sequence induction. Lacrimation was noted in four patients in the propofol Table 1. Demographic and anaesthetic data, mean (SD).
Thiopentone Age; years
Height; cm Weight; kg
Gestation; weeks I-D time; minutes Birth weight; kg
Anaesthetic time; minutes
30.6 149 65.4 38.9 12.2
Propofol
29.4 (4.3) I52 (6.9) (9.4) 65.8 (9.3) (1.3) 39.1 (1.5) (2.6) 10.8 (2.1) 3.28 (0.43) 3.22 (0.62) 42.0 (9.2) 48.2 (9.4) (5.1)
(12.1)
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Fig. 2. Mean (SEM) maternal heart rate after induction of anaesthesia in the thopentone -0and propofol -.Dgroups
22
G . Yau et al.
Table 2. Maternal recovery times and postbox scores, mean (SD).
Table 4. Apgar scores and neurologic and adaptive capacity scores
(NACS), median (range). Eye opening; minutes Date of birth; minutes Postbox scores after 30 minutes compared with before operation Postbox scores after 60 minutes compared with before operation
Thiopentone
Propofol
7.56 (3.0) 9.69 (3.2)
7.03 (2.5) 9.12 (2.51
0.53 (0.27)
0.63 (0.15)
0.83 (0.24)
0.89 0.19)
There were no differences in gestation or birth weight between the groups. Induction to delivery times were similar and uterine incision to delivery times were all less than 90 seconds. Umbilical blood gas analysis, neonatal Apgar scores and NACS were satisfactory and similar between groups (Tables 3 and 4). Apgar scores and NACS were not related to induction-to-delivery times in the thiopentone group but NACS at 2 hours were slightly lower in the propofol group with increasing induction-to-delivery time (p < 0.05) (Fig. 3). Measured blood loss ranged from 200 to 1000 ml with n o difference between groups. There were no anaesthetic o r obstetric complications and no patients complained of awareness during anaesthesia.
Discussion The two anaesthetic techniques gave clinically satisfactory and similar results. There was no hypotension after induction of anaesthesia. The peak decrease in arterial blood pressure after propofol usually occurs at 2 to 3 minutes and patients in this study were subjected to the coincident stimuli of cricoid pressure and intubation. Arterial pressures, after tracheal intubation, returned to baseline levels more rapidly in the propofol group. Propofol attenuates the cardiovascular response to laryngoscopy and intubation more than thiopentone.l.Lo.L1 Variations in arterial pressure and heart rate during Caesarean section are influenced more by the rapid circulatory volume changes during surgery and delivery than the anaesthetic technique. However, during other surgical procedures, the cardiovascular changes during maintenance of anaesthesia by propofol infusion have been comparable with the use of volatile agent^.',^,^ Maternal recovery was similar between groups although our previous study showed that a similar propofol group had slightly faster recovery times6 The anaesthetic technique differed slightly in this study since nitrous oxide was
Apgar 1 minute Apgar 5 minutes NACS 15 minutes NACS 2 hours NACS 24 hours
Thiopentone
Propofol
9 (5-10) 10 (8-10) 32 (25-34) 33 (23-35) 33 (30-37)
9 (5-10) 10 (8-10) 32 (21-36) 33.5 (25-36) 34.5 (30-37)
discontinued 2 minutes after the propofol or enflurane, while the earlier study stopped all anaesthetic agents simultaneously. Propofol, after major operations, has not always shown faster recovery when compared with a volatile agent.' No patients complained of awareness in this study, but with our sample size of 20 there is still a 5% probability that the incidence of awareness is as high as 14%. However, a previous study using the same propofol infusion rate measured propofol concentrations during anaesthesia and recovery, and in every patient propofol concentrations were higher during anaesthesia than at the time of eye opening.6 Inhalation anaesthetic requirements are decreased in pregnancy but this has not been investigated during intravenous anaesthesia. Minimum alveolar concentrations for inhalational agents are reduced in animal studies with pregnant ewest2 and rats,13 which may be related to increased levels of circulating e n d 0 r ~ h i n s . IThere ~ is, in pregnancy, decreased plasma binding of many drugs with increased free levels1sbut there are no data for propofol. Comparative studies with thiopentone and propofol during induction of anaesthesia for Caesarean section have shown variable neonatal outcome. Apgar scores were ~ i r n i l a r ' l o~rl lower ~ ~ ~ ~after p r o p ~ f o l . l * .Neurobehavioural '~ assessment was satisfactory after p r ~ p o f o l ,but ~ other workers reported lower scores after propofol (2.8 mg/kg) compared with thiopentone (5 mg/kg).19 In this study, NACS in the propofol group were slightly lower with longer I-D times. A longer infusion time before delivery is likely to cause higher neonatal levels at delivery, and lower NACS have been correlated with higher neonatal levels of propofoLZ0However, small differences in NACS have not been shown to have any clinical significance. A propofol infusion coupled with nitrous oxide gave satisfactory induction and maintenance of anaesthesia. Haemodynamic changes at induction were less variable in the propofol group, compared with a thiopentone, nitrous oxide, enflurane technique, and neonatal effects were similar when infusion time before delivery ranged from 7 to
Table 3. Umbilical venous and arterial blood gas analysis, mean (SD).
Thiopentone Umbilical venous pH Umbilical venous Pco, (kPa) Umbilical venous Po, (kPa) Umbilical venous BE Umbilical arterial pH Umbilical arterial Pco, (kPa) Umbilical arterial Po, (kPa) Umbilical arterial BE
7.327 5.63 4.35 -3.0 7.271 6.86 2.44 -3.0
(0.028) (0.65) (1.0) (1.9) (0.038) (1.0) (0.81) (2.6)
Propofol 7.331 (0.056) 5.89 (0.77) 3.80 (0.94) -2.8 (1.7) 7.262 (0.034) 7.10 (0.91) 2.19 (0.71) -2.8 (2.2)
Propofol for Caesarean section
401
0
. .
00 0
0 f
0
N
30
I
a n
.. . 0
0
.
. O m .
m
a
.
25t 201 6
0
.ao
0
I
8
1 1 I 1 1 1 1 10 12 14 16 Induction t o delivery t i m e (minutes) I
’
I
18
Fig. 3. Induction to delivery time (minutes) against neurologic and adaptive capacity scores 2 hours after delivery, 0 , thiopentone group; 0, propofol group.
14 minutes. However, a prolonged infusion time before delivery may cause slightly lower NACS scores. Maternal recovery was rapid and similar in both groups. We believe that maintenance of anaesthesia with inhalation agents remains the standard for obstetric general anaesthesia.
Acknowledgments
We thank Professor A. Chang, Chairman, Department of Obstetrics and Gynaecology for permitting this study on patients in his department, Mrs V. K o t u r for her assistance and ICI Pharmaceuticals for their support. References 1. DOZEVA, SHAFERA, WHITE PF. Propofol-nitrous oxide
oxide for general versus thiopental-isoflurane-nitrous anesthesia. Anesthesiology 1988; 6 9 63-71. JBM, VAN EGMOND J, CRULJF. 2. DE GROODPMRM, HARBERS Anaesthesia for laparoscopy. A comparison of five techniques including propofol, etomidate, thiopentone and isoflurane. Anaeslhesia 1987; 42: 815-23. 3. ZUURMONVWWA, VAN LEEUWENL, HELMERSJHJH. Recovery from propofol infusion as the main agent for outpatient arthroscopy. A comparison with isoflurane. Anaesthesia 1987; 4 2 356-9.
23
4. SEARJW, SHAWI, WOLFA, KAYNH. Infusions of propofol to supplement nitrous oxide-oxygen for the maintenance of anaesthesia. A comparison with halothane. Anuesihesia 1988; 43 (SUPPI.):18-22. 5. DAILLAND P, COCKSHOTT ID, LIRZINJD, JACQUINOT P, JORROT JC, DEVERYJ, HARMEYJ-L, CONSEILLERC. Intravenous propofol during caesarean section: placental transfer, concentrations in breast milk, and neonatal effects. A preliminary study. Anesthesiology 1989; 71: 827-34. 6. GREGORY MA, GIN T, YAU G, LEUNGRKW, CHANK , OH TE. Propofol infusion anaesthesia for Caesarean section. Canadian Journal of Anaesthesia 1990; 37: 5 14-20. MA, CHANK, OH TE. Maternal and fetal 7. GIN T, GREGORY levels of propofol at Caesarean section. Anaesthesia and Intensive Care 1990; 18: 1804. 8. CRAIGJ, COOPERGM, SEARJW. Recovery from day-case anaesthesia. Comparison between methohexitone, Althesin and etomidate. British Journal ofAnaesthesia 1982; 5 4 447-51. 9. AMIEL-TISON C, BARRIERG, SHNIDERSM, LEVINSONG, HUGHESSC, STEFANISJ. A new neurologic and adaptive capacity scoring system for evaluating obstetric medications in full-term newborns. Anesthesiology 1982; 56: 340-50. 10. HARRISCE, MURRAYAM, ANDERSON JM, GROUNDSRM, MORGAN M. Effects of thiopentone, etomidate and propofol on the haemodynamic response to tracheal intubation. Anaesthesia 1988; 4 3 (Suppl.): 32-6. 11. GINT, GREGORY MA, OH TE. The haemodynamic effects of propofol and thiopentone for induction of Caesarean section. Anaesthesia and Intensive Care 1990; 18: 175-9. 12. PALAHNIUK RJ, SHNIDERSM, EGER, 11, EI. Pregnancy decreases the requirement for inhaled anesthetic agents. Anesthesiology 1974; 41: 82-3. 13. STROUTCD, NAHRWOLD ML. Halothane requirement during pregnancy and lactation in rats. Anesthesiology 1981; 5 5 322-3. 14. GINTZLER AR. Endorphin-mediated increases in pain threshold during pregnancy. Science 1980; 210 193-5. E, CREMAA. Plasma protein binding of drugs in 15. PERUCCA pregnancy. Clinical Pharrnacokinetics 1982; 7: 336-52. P. Comparison of 16. VALTONEN M, KANTO J, ROSENBERG propofol and thiopentone for induction of anaesthesia for elective Caesarean section Anaesthesia 1989; 44: 758-62. KT, HOWARD 17. MOOREJ, BILLKM, FLY” RJ, MCKEATING PJ. A comparison between propofol and thiopentone as induction agents in obstetric anaesthesia. Anaesthesia 1989; 4 4 753-7. 18. COUPERJL, LOMBARD TP. Comparison of propofol (Diprivan) with thiopentone as induction agent for elective Caesarean section. Canadian Journal of Anaesthesia 1988; 35: S132. 19. CELLENO D, CAPOGNA, G, TOMASSETTI M, COSTANTINO P, D1 FEOG, NISINIR. Neurobehavioural effects of propofol on the neonate following elective Caesarean section. British Journal of Anaesihesiu 1989; 6 2 649-54. MA, KOTURCF. Recovery 20. GINT, YAUG, CHANK, GREGORY from propofol infusion anaesthesia for Caesarean section. Neiiroscience Letters (Suppl.) 1990; 37: S44.
