G. Yau

Propofol for induction and maintenance of anaesthesia at Caesarean section A comparison with thiopentone/enflurane

A propofol infusion regimen and a standard general anaesthetic were compared in 40 Chinese women undergoing elective Caesarean section. Twenty patients received propofol 2 mg/kg for induction of anaesthesia followed by propofol 6 mg/kg/hour, while 20 patients received thiopentone 4 mg/kg with enflurane 1% 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.

Propofol infusion anaesthesia for caesarean section

Two propofol infusion regimens and a standard general anaesthetic were compared in thirty Chinese women undergoing elective Caesarean section. After induction of anaesthesia with propofol 2 mg · kg−1, ten patients received propofol 6 mg · kg−1 · hr−1 and nitrous oxide 50 per cent in oxygen while ten were given propofol 9 mg · kg−1 · hr−1 with 100 per cent oxygen. The other ten patients received thiopentone 4 mg · kg−1 and nitrous oxide 50 per cent in oxygen with enflurane one per cent. Maternal recovery times and psychomotor performance were recorded. Neonates were assessed by Apgar scores, neurologic and adaptive capacity scores (NACS) and umbilical cord blood gas analysis. Haemodynamic changes were similar immediately following induction but the low propofol infusion group had the best haemodynamic stability subsequently. Recovery times were fastest in the low-infusion group but there were no differences in later postbox testing. Neonatal Apgar scores and umbilical blood gas analysis were similar but NACS at two hours were poorer in the high infusion group. A propofol infusion coupled with nitrous oxide appears to be a satisfactory technique for Caesarean section.RésuméLors de leur césarienne élective, trente chinoises nous ont permis de comparer deux modes de perfusion de propofol et un autre mode d’anesthésie générate. Après une induction anesthesique avec 2 mg · kg−1 de propofol, nous avons donne à dix d’entre elles 6 mg · kg−1 · h−1 de propofol et 50 pour cent de N2O avec O2 tandis que dix autres recevaient 9 mg · kg−1 · h−1 de propofol et 100 pour cent d’O2. Enfin, nous donnions aux dix dernieres, 4 mg · kg−1 depentothal, 50 pour cent de N2O avec O2 et un pour cent d’enflurane. Nous avons evalue le réveil des meres, leurs performances psychomotrices, les scores d’Apgar, les “Neurologic and Adaptive Capacity Scores” (NACS) des nouveaux-nes et les gaz sanguins du cordon ombilical. Après l’induction, les valeurs hemodynamiques variaient de la même façon mais par la suite, la perfusion de propofol à faible dose assurait une meilleure stabilité. Elle permettait aussi un éveil plus rapide quoique à moyen terme, la recuperation était la meme pour toutes. Quant aux nouveaux-nés, les gaz sanguins et les scores d’Apgar étaient comparables mais le NACS était moins bon, deux heures après la naissance, dans le groupe à haute dose de propofol. line perfusion de propofol couplee à du protoxyde d’azote constitue une technique appropriee à une césarienne.

A comparison of the effects of omeprazole and ranitidine on gastric secretion in women undergoing elective caesarean section.

This study compares the efficacy of omeprazole and ranitidine at reducing gastric secretion in obstetric patients. Sixty‐five women scheduled to undergo elective Caesarean section under general anaesthesia were randomly allocated to receive either omeprazole 40 mg or ranitidine 150 mg orally at 2200 hours the night before and at 0600 hours on the morning of surgery. Intragastric pH and volume were measured immediately after induction of anaesthesia and on completion of surgery. All patients had gastric aspirates less than 25 ml. None of the omeprazole group had an aspirate of pH less than 3.5. Six patients (19%) in the ranitidine group had aspirates of pH less than 3.5, a significant difference from the omeprazole group (p < 0.05). Of these six, two (6%) had aspirates of pH less than 2.5. Hence this study showed that omeprazole was more effective and consistent than ranitidine at maintaining gastric pH greater than 3.5.

Acid aspiration prophylaxis for emergency Caesarean section

Over a 3.5 year period, 384 patients requiring emergency Caesarean section under general anaesthesia received at random one of six acid aspiration prophylaxis regimens as soon as the decision was made for surgery. In the first phase of the study, sodium citrate administered orally 0.3 M, 30 ml (group C, n = 120) was compared with metoclopramide 10 mg administered intravenously and sodium citrate (group MC, n = 65). In the second phase, all patients received sodium citrate, and either intravenous administration of ranitidine 50 mg (group RC, n = 50), omeprazole 40 mg (group OC, n = 50), ranitidine 50 mg with metoclopramide 10 mg (group RMC, n = 50) or omeprazole 40 mg with metoclopramide 10 mg (group OMC, n = 49). Gastric contents were aspirated using a 16 FG Salem sump tube and acidity measured with a pH meter. Non‐parametric tests were used for comparisons. There was no difference in gastric volume or pH between groups C and MC, or among OC, RC, OMC and RMC. After pooling the data, median (range) gastric volume in groups C and MC (55(0–360) ml) was greater than in groups OMC and RMC (40(3–270) ml, p < 0.05). Median (range) pH was lower in groups C and MC (4.97(0.76–6.99)) than in groups OC, RC, OMC and RMC (5.76(1.11–7.5), p < 0.001). The proportion of patients with pH < 3.5 and volume > 25 ml in the C and MC groups (43/185) was greater than that in the OC, RC, OMC and RMC groups (18/199, p < 0.001). Ranitidine and omeprazole administered intravenously were equally effective adjuncts to sodium citrate in reducing gastric acidity for emergency Caesarean section. Compared with sodium citrate alone, the addition of either ranitidine, omeprazole or metoclopramide alone did not reduce gastric volume while small reductions in gastric volume were seen with the addition of metoclopramide and either ranitidine or omeprazole.

A comparison of omeprazole and ranitidine for prophylaxis against aspiration pneumonitis in emergency Caesarean section

One hundred and sixty‐two Chinese women undergoing emergency Caesarean section were allocated at random on admission to the labour ward to receive one of three regimens for orally administered chemoprophylaxis against acid aspiration: ranitidine 150 mg 6 hourly with sodium citrate at induction of anaesthesia, omeprazole 40 mg 12 hourly with sodium citrate, or omeprazole 40 mg 12 hourly alone. Intragastric pH and volume were measured immediately after induction of anaesthesia. Ten patients (17%) in the omeprazole‐only group, three (6%) in the omeprazole and citrate group and one (2%) in the ranitidine group had an intragastric pH < 2.5 and volume > 25 ml (p < 0.05). The use of sodium citrate resulted in higher intragastric pH but larger intragastric volumes (p < 0.05). The sodium citrate and ranitidine regimen was the most cost‐effective among the three.

Disposition of Propofol Infusions for Caesarean Section

The disposition of propofol was studied in women undergoing elective Caesarean section. Indices of maternal recovery and neonatal assessment were correlated with venous concentrations of propofol. After induction of anaesthesia with propofol 2.0 mg · kg−1, ten patients received propofol 6 mg · kg−1 · hr−1 with nitrous oxide 50 per cent in oxygen (low group) and nine were given propofol 9 mg · kg−1 · hr−1 with oxygen 100 per cent (high group). Pharmacokinetic variables were similar between the groups. The mean ± SD Vss = 2.38 ± 1.16 L · kg−1, Cl = 39.2 ± 9.75 ml · min−1kg−1 and t1/2β= 126 ± 68.7 min. At the time of delivery (8–16 min), the concentration of propofol ranged from 1.91–3.82 μg · ml−1 in the maternal vein (MV), 1.00–2.00 μg · ml−1 in the umbilical vein (UV) and 0.53–1.66 μg · ml−1 in the umbilical artery (UA). Neonates with high UV concentrations of propofol at delivery had lower neurologic and adaptive capacity scores 15 minutes later. The concentrations of propofol were similar between groups during the infusion but they declined at a faster rate in the low group postoperatively. Maternal recovery times did not depend on the total dose of propofol but the concentration of propofol at the time of eye opening was greater in the high group than the low group (1.74 ± 0.51 vs 1.24 ± 0.32 μg · m−1, P < 0.01). The rapid placental transfer of propofol during Caesarean section requires propofol infusions to be given cautiously, especially when induction to delivery times are long.RésuméNous avons mesuré l’élimination du propofol lors de césariennes électives et avons mis en relation le réveil maternel et la performance du nouveauné avec la concentration veineuse de propofol. Après une dose d’induction de 2,0 mg · kg−1 de propofol, nous en perfusions 6 mg · kg−1 · h−1 de plus chez dix patientes qui respiraient 50 pour cent de protoxyde d’azote avec de l’oxygène (groupe 1) et 9 mg · kg−1 · h−1 chez neuf respirant de l’oxygène pur (groupe 2). Les variables pharmacocinétiques étaient semblables dans les deux groupes avec un Vss de 2,38 ±1,16 L · kg−1, une Cl de 39,2 ± 9,75 ml · mn−1 kg−1 et une t1/2β de 126 ± 68,7 mn. Au moment de la naissance (8–16 min post-induction), les concentrations de propofol allaient de 1,91 à 3,82 μg · ml−1 dans le sang veineux maternel, de 1,00 à 2,00 μg · ml−1 dans la veine ombilicale et de 0,53 à 1,66 μg · ml−1 dans l’artère ombilicale. Les nouveauxnés au sang veineux ombilical plus riche en propofol, avaient, 15 minutes après la naissance,un «neurologic and adaptative capacity score» plus bas. Semblables pendant la période de perfusion. les concentrations de propofol diminuèrent plus vite chez le groupe 1 après l’opération. La dose totale de propofol n’influençait pas le réveil des patientes mais, à l’ouverture des yeux, celles du groupe 2 en avaient des concentrations plus élevées: 1,74 ±0,51 vs 1,24 ± 0,32 μg · ml−1, P < 0,01. A cause d’un transfert placentaire rapide, on doit perfuser le propofol avec prudence lors d’une césarienne surtout si l’intervalle entre l’induction et la naissance se prolonge.

Obstetric epidural analgesia with mixtures of bupivacaine, adrenaline and fentanyl

We performed a double‐blind comparison of six solutions for epidural analgesia in 90 healthy Chinese women with uncomplicated pregnancies. Patients were randomly allocated to receive 10 ml bupivacaine 0.125% or 0.25% plain, bupivacaine 0.125% with adrenaline 1.25 μg/ml, bupivacaine 0.25% with adrenaline 2.5 μg/ml or the latter two solutions with added fentanyl 50 μg. Analgesia was unsatisfactory in 30% of the bupivacaine 0.125% groups without fentanyl. The addition of adrenaline, compared with bupivacaine 0.25% plain, gave faster onset and longer duration of analgesia (p < 0.05) which was similar to that found in both fentanyl groups. There were no differences in method of delivery or neonatal Apgar scores among groups. The least concentrated mixture that gave the best analgesia was the combination of bupivacaine 0.125% with adrenaline 1.25 μg/ml and fentanyl 50 μg.

Duplicate markings on an epidural catheter

in oxygen was started by hand via a Bain circuit. Five minutes into the operation, without informing the anaesthetists of their intention to do so, 0.5 ml cocaine paste (25% with adrenaline 0.18%) was applied to the left nostril and the nose was immediately instrumented. The ECG showed multifocal ventricular ectopic beats which deteriorated into coarse ventricular fibrillation within 10 seconds. The halothane was switched off and the patient’s lungs ventilated with 100% 0,. Two precordial ‘thumps’ were administered which had no effect on cardiac rhythm. External cardiac massage was started. Within 2 minutes the child had reverted spontaneously to sinus rhythm without defibrillation or drugs. However, lignocaine 1 mg/kg was administered to prevent recurrence of the arrhythmia. The operation was abandoned when on initial inspection the nose seemed clear. The child was woken up and made an uneventful recovery. A12 lead ECG in recovery revealed a sinus tachycardia, but no other abnormality. ECG was monitored overnight with no further arrhythmias. The patient was re-investigated by the paediatric team and it was confirmed that there was no detectable cardiovascular anomaly. There are a number of reasons why this child could have developed an arrhythmia. Although an association between hypertelorism and cardiac anomalies has been described in the literature,‘ this usually occurs as part of a larger symptom complex, the other elements of which were not exhibited by this child. Furthermore, there was no clinical evidence of underlying cardiac anomaly. A nasocardiac reflex has been described.’~~ Physical, chemical and thermal stimuli to the nose may cause widespread cardiovascular and respiratory responses.’ This reflex is thought to occur via sensory nerves and the neuropeptide substance P is the suggested transmitter. Cocaine is used during surgery on the nose principally for its vasoconstrictor a ~ t i o n . ~ The drug inhibits reuptake of noradrenaline at sympathetic nerve terminals and this accounts for its effects on the cardiovacular ~ y s t e m . ~ Uptake of cocaine into the circulation is slowed by addition of adrenaline,“ however, this further increases circulating catecholamines and increases the potential for tachyarrhythmias, especially in the presence of halothane anaesthesia.6 In one study, intranasally applied cocaine 1.5 mg/kg was absorbed rapidly but no important cardiovascular effects occurred in the presence of halothane anae~thesia.~ It seems likely therefore that ventricular fibrillation in this case was caused by sympathomimetic substances in the presence of halothane anaesthesia during a stimulating procedure.