Comparison of propofol and thiopentone for induction of anaesthesia for elective Caesarean section

Propofol 2.5 mg/kg was compared with thiopentone 5 mg/kg as an induction agent for elective Caesarean section. Thirty-two healthy women with cephalopelvic disproportion were included in an open randomised study. The placental transfer of propofol was also studied in 10 other mothers given a single dose of 2.5 mg/kg. The induction characteristics and haemodynamic response to propofol and thiopentone were similar. Side effects were rare with both agents, but propofol caused more discomfort on injection compared to thiopentone. Recovery times were shorter after propofol as evaluated by time to orientation, recovery scoring after anaesthesia and measurements with the Maddox wing. Rapid placental transfer and significant fetal uptake were detected for propofol. There was no significant neonatal depression as assessed by Apgar scores and blood gas analyses. Propofol appears to be a suitable alternative to thiopentone as an induction agent for anaesthesia in elective Caesarean section.     

Propofol combined with nitrous oxide-oxygen for induction and maintenance of anaesthesia

After a bolus of 2 mg/kg, propofol was given by continuous infusion (150 micrograms/kg/minute for 30 minutes and then 100 micrograms/kg/minute) supplemented with nitrous oxide for anaesthesia during ear surgery in 12 patients. Cardiovascular changes were not significant except for a decrease in heart rate after 60 minutes. Acid-base balance was unaffected by the amount of fatty emulsion. Cortisol levels showed a nonsignificant decrease during the prolonged administration of propofol but had recovered completely by one hour following anaesthesia. Mean blood concentrations of propofol were 10.5 micrograms/ml (SEM 1.2) at the onset of unconsciousness, between 3.4 and 4.5 micrograms/ml during continuous infusion and 2.9 micrograms/ml (SEM 0.3) on awakening. Patients opened their eyes 6 minutes (SEM 1) after discontinuation of the infusion, and were responsive at 7.5 minutes (SEM 0.5), which suggests that propofol infusion can be used safely for surgery of 2 hours' duration.     

Subarachnoid anaesthesia for elective Caesarean section

Forty patients who underwent elective lower segment Caesarean section under subarachnoid anaesthesia received either 2.0 ml 0.5% cinchocaine in 6% dextrose or 2.5 ml 0.5% bupivacaine in 8% dextrose via a 26-gauge needle with the patient in the left lateral position. Onset time was rapid in both groups and the distribution of maximum ascent of sensory analgesia was T1-T6. Efficacy of analgesia was greater in the bupivacaine group, although the duration of both sensory and motor blockade was shorter than following cinchocaine. There were no significant differences between the two groups either in the incidence and severity of complications or in the condition of the neonates. The high incidence (50-65%) and often profound extent of hypotension seen throughout the trial, confirm the ineffectiveness of crystalloid preload of 1500 ml as a single prophylaxis against hypotension.     

Plasma bupivacaine levels associated with extradural anaesthesia for Caesarean section

Plasma bupivacaine levels were measured in 47 women undergoing extradural Caesarean delivery. They were divided into four groups according to the following dose regimens using 0.5% bupivacaine. Group A were given a bolus of 20 ml with increment after 20 minutes. Groups B and C were given 10 ml initially with further increments if required at 10 minutes (group B) and 20 minutes (group C); Group D consisted of patients who had an extradural block extended for emergency Caesarean delivery. In the elective groups the highest and most rapidly achieved values were associated with group A and the lowest levels found in group C. The highest levels of all were found in the emergency group. The investigation indicates that slow controlled induction of extradural anaesthesia for Caesarean section greatly reduces the risk of local anaesthetic toxicity.     

Respiratory effects of spinal anaesthesia for Caesarean section

We report the changes observed in a number of pulmonary function tests performed on 36 patients undergoing Caesarean section under spinal anaesthesia. The tests comprised peak expiratory flow, forced expiratory volume in one second, forced vital capacity, forced expiratory volume in one second to forced vital capacity ratio and the maximal mid-expiratory flow. Significant changes occurred that are consistent with a restrictive ventilatory defect. These changes persisted for four hours after the induction of spinal anaesthesia. Administration of 35% oxygen by facemask failed to change significantly fetal umbilical vein pH or partial pressure of oxygen.     

Spinal anaesthesia with hyperbaric lignocaine for elective Caesarean section

This study was carried out in 30 patients undergoing elective Caesarean section to assess the predictability and reliability of spinal anaesthesia with 5% hyperbaric lignocaine, with a view to incorporating the technique in our failed intubation drill. The spinal was performed with a 25-gauge needle in either the sitting (15 patients) or left lateral position (15 patients). The speed of onset of anaesthesia to T6 was significantly faster (p less than 0.01) in the lateral group, but the duration of action was similar in both groups. Twelve patients had hypotension and four developed severe postspinal headaches. The block progressed to the C2 dermatome in four patients and was associated with dysphagia. This was totally unpredictable and may be due to altered cerebrospinal fluid dynamics in late pregnancy. Therefore, the use of spinal anaesthesia with heavy lignocaine may be inadvisable in obstetric patients, especially following failed intubation.     

Combined epidural/spinal anaesthesia for Caesarean section

An evaluation of a 30 gauge spinal needle in a combined epidural/spinal anaesthetic technique for Caesarean section revealed a 25% failure rate of the spinal element. In this unit, no more than 4% of spinal anaesthetics might be expected to fail. One of the reasons for the higher failure rate was that, when using the Tuohy needle as an introducer, the dura was not identified. This prompted us to compare the 'through-the-Tuohy' or needle within needle approach for combined epidural/spinal anaesthesia, with a technique that involved siting the epidural and spinal sequentially in separate spaces. One hundred women requiring elective Caesarean section under spinal anaesthesia were randomised into single or double space groups. The technique failed in 16% of through-the-needle cases, and in 4% of sequential sitings. Combined spinal/epidural anaesthesia for Caesarean section is more successful if each procedure is performed using separate spaces.     

An evaluation of a 30-gauge needle for spinal anaesthesia for Caesarean section

A 30-gauge spinal needle was evaluated for Caesarean section, using a combined epidural/spinal technique, in 50 mothers. Spinal anaesthesia failed in six mothers and was inadequate in another six. General anaesthesia was required on one occasion. A 25% overall failure rate suggests that a 30-gauge needle is not a practical proposition for routine clinical practice.     

Extending low-dose epidural analgesia for emergency Caesarean section. A comparison of three solutions

We conducted a prospective double-blind randomised trial to compare bupivacaine 0.5%; a 50 : 50 mixture of bupivacaine 0.5%/lignocaine 2% with 1 : 200 000 adrenaline (final concentration); and lignocaine 2% with 1 : 200 000 adrenaline for converting a low-dose labour epidural into a block adequate for emergency Caesarean section. Ninety patients were studied, 30 in each group. There was no difference between the groups in the time taken for bilateral loss of cold sensation to reach T4. Onset time was unaffected by the existing sensory level pre-Caesarean section top-up; the number of low-dose top-ups in labour; the total dose of bupivacaine in labour; or maternal weight or height. Three patients in the lignocaine with adrenaline group had blocks that reached the cervical dermatomes and three in the same group required general anaesthesia for inadequate anaesthesia, compared with none in the other groups (both p = 0.04).     

A comparison of propofol and methohexitone as induction agents for day case isoflurane anaesthesia

The induction and recovery characteristics of equivalent doses of propofol and methohexitone were compared in 50 patients undergoing day case isoflurane anaesthesia. Propofol induction was smoother but was associated with greater cardiorespiratory depression. Both the speed and quality of recovery were superior with propofol compared with methohexitone.     

Comparison of propofol and thiopentone for induction of anaesthesia in premedicated patients

Thirty premedicated ASA I or II patients scheduled for minor gynaecological surgery, were randomly allocated to receive either 1.5 mg/kg or 2 mg/kg propofol of the new emulsion formulation, or 4 mg/kg thiopentone, given over 20 seconds. Anaesthesia was successfully induced in all 30 patients. The mean (SEM) induction times were for propofol 1.5 mg/kg 33.3(3.2) seconds, for 2 mg/kg 30.5(2.7) seconds and for thiopentone 34.6(2.7) seconds. The incidence of apnoea greater than 10 seconds, was respectively 60, 80 and 80%, and the mean duration of apnoea 30.8(5.3), 37.1(5.0) and 23.7(5.0) seconds. The mean systolic blood pressure decreased after propofol 1.5 mg/kg by 16.0 mmHg, after 2 mg/kg by 18.6 mmHg, and increased after thiopentone by 1 mmHg, 2 minutes after injection. Heart rate increased significantly 2 minutes after thiopentone by an average of 15.1 beats/minute, but not after propofol. Pain was not reported during or after the injection. No major adverse reactions occurred at induction or during maintenance of anaesthesia with an inhalation agent. One patient who received 2 mg/kg propofol and isoflurane vomited for 24 hours. The recovery of anaesthesia after propofol induction, was quicker than after thiopentone.     

Propofol for induction of anaesthesia in children

The induction characteristics, dosage requirements, cardiovascular and respiratory effects of propofol with added lignocaine were compared with those of thiopentone and halothane inhalational induction in two groups of children aged 1-5 years and 5-10 years. Propofol induction produced significantly greater decreases in blood pressure, particularly in the 1-5 year age group. Heart rate was maintained well with all three induction techniques. Pain on injection into a vein on the dorsum of the hand was significantly more common with propofol despite the addition of lignocaine. However, this was mild in the majority of children and did not interfere with the induction of anaesthesia. The incidence of respiratory depression and other adverse effects was low with all three induction methods. The mean induction doses of both intravenous agents were greater in the 1-5-year age group. The ratio of thiopentone to propofol dose was approximately 2.5:1 in both age groups. The high incidence of pain on injection with propofol may prove to be a significant drawback to its otherwise satisfactory use in children.     

Propofol for intravenous sedation

This study investigated the properties of propofol when given by subanaesthetic infusion to provide sedation as an adjunct to spinal anaesthesia for lower limb surgery in 40 patients. Sedation, defined as sleep with preservation of eyelash reflex and purposeful reaction to verbal or mild physical stimulation, was satisfactorily achieved and maintained with minimal complications. The mean duration of infusion was 98 minutes and a mean infusion rate of 3.0 mg/kg/hour was required in patients over 65. This was significantly less (p less than 0.005) than the 4.1 mg/kg/hour required in younger patients. Recovery was impressively rapid; patients regained full consciousness approximately 4 minutes after the end of infusion, and were free from minor postoperative sequelae. Conversion to general anaesthesia was achieved in three patients where surgery encroached outside the analgesic field of the regional block, simply by increasing the infusion rate to approximately 10 mg/kg/hour.