Epidural anesthesia for obstetrics after spinal surgery.

The experience of 18 patients with previous spinal surgery who requested epidural anesthesia for obstetric pain was reviewed. Three received epidural anesthetics in two separate pregnancies, producing a total of 21 attempts at epidural anesthesia. All were initiated during labor and three were later extended for Cesarean delivery. Continuous lumbar epidural anesthesia was successfully established in 20 of 21 attempts. Ten were performed easily on the first attempt. There were excessive local anesthetic requirements and/or a patchy block for the remaining 11 attempts. The only complication that could be attributed to the attempts at epidural anesthesia was temporary low back pain in two patients with multiple attempts. No complications were noted on long-term follow-up. Our data, therefore, suggest that epidural anesthesia is safe and generally effective in obstetric patients with previous spinal surgery.

The epidural test dose in obstetrics: is it necessary?

One must distinguish between what is medically safe and what is legally safe. The authors have the impression that in order to be "legally safe" one must perform a test dose. This is despite the fact that it has not been conclusively shown that the use of test doses improve the safety margin of epidural anaesthesia, when administered by a competent person, with the proper resuscitative equipment immediately available. Until a controlled study is performed, test doses should be done for continuous epidural anaesthesia with the understanding that they are neither 100 per cent sensitive nor specific in preventing complications. It is however one more manoeuvre that may be useful in recognizing some of the patients with accidental subarachnoid placement of epidural catheters. The literature suggests that lidocaine 1.5 per cent in dextrose 7.5 per cent should be the test dose of choice in obstetric epidural anaesthesia in an amount known to produce spinal anaesthesia (30-50 mg). The use of epinephrine in test doses in unpremedicated healthy women in active labour is neither sensitive nor specific in signalling intravascular injection, and it may also be detrimental to fetal wellbeing. Epinephrine 15 micrograms as a test dose for intravenous injection appears to create more problems than it solves.

Nalbuphine: a supplement to isoflurane and enflurane anaesthesia.

A retrospective study was carried out to review the intra-operative use of nalbuphine at the average dose of 1.5 mg/kg as a supplement to isoflurane and enflurane in balanced anaesthesia in 108 surgical patients. Intra-operative cardiovascular stability and the quality of emergence were examined. The amount of halogenated anaesthetic used was compared to the theoretical amount that would have been needed in the absence of nalbuphine. In 90% to 95% of patients, blood pressures remained within 20% of baseline for the duration of anaesthesia. At emergence, 80% of patients had no pain. Nalbuphine appeared to reduce halogenated anaesthetic requirements by approximately 50%. These promising results for the intraoperative use of nalbuphine need to be confirmed by controlled prospective studies.

Epidural morphine for analgesia after caesarean section.

A randomized double blind placebo controlled study of the efficacy, duration and safety of epidural morphine for the management of pain after Cesarean section is reported. Three similar groups of patients received either 0, 4 mg or 8 mg of morphine sulphate in 10 ml of normal saline through an epidural catheter at the completion of the operation. Compared to the saline controls, both the 4 mg and 8 mg epidural morphine groups had significant pain relief as judged by an analogue pain scale (p less than 0.001), the time to the first administration of narcotic analgesics (p less than 0.001) and the amount of supplemental analgesic required in the first 36 hours after operation (p less than 0.001). The side effects occurred in a dose-dependent fashion. Two patients who received epidural morphine 8 mg plus additional narcotic or antihistamine had reduced respiratory rates but were easily rousable. Our experience suggests that the epidural administration of morphine 4 mg may be a safe and reliable method of obtaining prolonged analgesia following Caesarean section.

Prophylactic intramuscular ephedrine before epidural anaesthesia for caesarean section: efficacy and actions on the fetus and newborn.

The authors studied the effectiveness of ephedrine given intramuscularly before epidural anaesthesia with bupivacaine 0.5 per cent in three groups of patients undergoing elective caesarean section. The patients received intramuscular saline as a placebo, ephedrine 25 mg or ephedrine 50 mg, 15 to 30 minutes before anaesthesia. The incidence of hypotension was 8 to 12 per cent in all three groups. Prophylactic intramuscular ephedrine did not lower the incidence of hypotension significantly. Intramuscular ephedrine 50 mg caused a persistent hypertension in eight out of 12 patients and was associated with an increase in umbilical artery [H+] (decrease in pH). No differences were observed in other indices of neonatal well-being. The prophylactic use of intramuscular ephedrine before epidural anaesthesia for caesarean section is not recommended.

Effect of lateral position and volume on the spread of epidural anaesthesia in the parturient.

The effect of lateral positioning and the volume of drug injected on the spread of epidural anaesthesia was assessed in 131 healthy parturients. Epidural injection for anaesthesia was done at the L3-4 interspace and a catheter was inserted into the epidural space after injection of the drug. The patients were randomly assigned to four groups. The doses used were 12 ml of bupivacaine 0.25 per cent and 6 ml of bupivacaine 0.5 per cent. Patients were kept in the lateral position in which the block was done (Groups I and III) or turned to the opposite side after completion of the epidural injection (Groups II and IV). Sensory levels and maternal assessment of pain relief were determined fifteen to twenty minutes after injection. All assessments were done by a trained observer who did not know to what group the patient had been allocated. Maintenance of the lateral position after induction of epidural anaesthesia is compatible with satisfactory analgesia for labour. Twelve ml bupivacaine 0.25 per cent provides better analgesia than 6 ml bupivacaine 0.5 per cent although the same mass is injected. The quality of analgesia is improved by turning the patients to the contralateral side after injection of 12 ml bupivacaine 0.25 per cent.

Obstetrical anaesthesia practice in the University of Toronto affiliated hospitals and some randomly selected community hospitals.

A questionnaire was designed to determine the type of personnel that provide obstetrical anaesthesia care and the techniques used in the provision of this care. All seven hospitals with an obstetrical unit affiliated with the University of Toronto and seven community hospitals responded. All anaesthetics were given by physicians. Ninety-two per cent of those in University affiliated hospitals and 63 per cent of those in the community hospitals had obtained their specialty qualification. Standards for preoperative assessment and communication with the patients should be similar to those applied to patients receiving anaesthesia for other reasons. It was clear from our survey that pre-anaesthetic assessment of obstetrical patients differs from that advocated for other surgical patients. For vaginal deliveries, epidural analgesia was clearly the preferred choice, Subarachnoid block was rarely used. The majority of anaesthetists did not use a test dose. Eleven per cent in University-affiliated hospitals and 50 per cent in community hospitals sometimes conducted surgical anaesthesia without tracheal intubation for vaginal delivery. More than 60 per cent routinely encouraged their patients to accept general anaesthesia for Caesarean section. The doctors providing neonatal resuscitation may require further training. Surveys such as this are important if standards of anaesthetic practice are to be established.

Physiologic significance of hemodynamic measurements and their derived indices.

The fundamental value of hemodynamic monitoring is that it provides direct physiological measurements. The appropriate use of these requires an understanding of normal cardiac physiology and its alterations in certain disease states. An appreciation of the determinants of cardiac output, coronary blood flow and myocardial oxygen consumption will improve the interpretation and subsequent manipulation of these values when one is confronted with them clinically.