The use of extradural analgesia in operative obstetrics has been investigated and retined in recent years so that it has become an established, safe and generally reliable method to provide anaesthesia for lower segment Caesarean section. Thc use of a two-stage top-up technique' has been particularly effettive in achieving adequate analgesia without blockade that extends to cervical segments. Subarachnoid anaesthesia is less well established in this area and the use of an isobaric agent, such as 0.5% bupivacaine plain solution, has been shown to be unreliable and to produce occasional high blocks.*-' The aim of this study was to identify a technique of subarachnoid anaesthesia that would produce adequate analgesia for a sufficient duration of time but without dangerously high blockade. The volumes chosen of the respective agents were based on our previous clinical experience. MethodsMothers admitted to the study were those who had requested regional analgesia for their elective Caesarean section arid had given conscnt for spinal anaesthesia. They were randomly allocatcd to two groups: 20 received 2.0 ml O.S"/i, cinchocaine in 64'0 dextrose, and 20 received 2.5 ml 0.5'.;, hupivacainc in 8"% dextrose. Tc.chniqueIn all mothers the circulation was prcloaded with 1 .S litres Hartmann's solution given over 20.-30 minutes before injection of local anaesthetic. Lumbar puncture was performed at the level of the Lz , interspace. using a %-gauge spinal needle with the niothcr o n the operating table in thc left lateral position. L,,2 or L, were used only if lumbar puncture was not possible at Lz 3. The predetermined volume of local anaesthetic was then injected over [20][21][22][23][24][25][26][27][28][29][30] seconds without barhotage. and the mother immediately returned to the supine position with left lateral tilt to avoid aortocaval compression. The mother's head was rested on two pillows, primarily lor comfort but also to limit the ascent of blockade. Oxygen was given at a rate of 4-5 litres; minute until delivcry of the infants. lntravcnous ephedrine was given in 3-6-mg increments if hypotension less than 90 rnmHg systolic occurred. Ub s~~r v u i i o n sObservations were made on a double-blind basis in that the assessor had no knowledge of the agent or volume used. Arterial blood prcssure and heart rate were recorded at one-minute intervals for 5 ininutcs and thereafter every 5
No abstract
We read with interest the report by A.R. Michie e f nl. (ilnnesrhesia 1988; 43: 9 6 9 ) . Subarachnoid anaesthesia has been used recently in our hospital for Caesarean sections with very satisfactory results. Our practice differs from that of the authors in several respects. We preload our patients with 500 ml compound sodium lactate solution and 500 ml modified gelatin (Gelofusine) before the subarachnoid block is established. Intramuscular ephedrine 30 mg is given prophylactically 15-30 minutes before the spinal block. The patient is placed in the left lateral position and 1.5-2.0 ml 0.5% hcavy bupivacaine are injected at L, or L3-, interspace through a 26-G spinal needle, using minimal barbotage.The patient is placed supine immediately with right lateral tilt and the extent of the block assessed with ethyl chloride spray. The table is then tilted to obtain a block to T, and thc table returned to a left lateral tilt when surgery starts.This technique has been used on 40 patients with satisfactory analgesia in all cases. Hypotension (systolic 100 mmHg or symptomatic) in 23% of patients was rapidly corrected with intravenous increments of ephedrine; in two patients the hypotension was serious. Postoperative headache was minimised by taking great care to ensure that thcre was only a single puncture of the dura and keeping the patients flat for 12 hours after the Caesarean section.We considcr subarachnoid anaesthesia to have significant advantages over epidural anaesthesia for Caesarean section. in particular because of the rapid onset of action and the more profound analgesia produced. Thesc qualities arc of particular value for emergency Caesarean sections. We agree with the authors. however, that its main disadvantage is in thc variable and short duration of action of 0.5% heavy bupivacaine. It is not used if' operative difficulties are envisaged.
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