Combined spinal epidural (CSE) analgesia: technique, management, and outcome of 300 mothers.

Epidural analgesia in labour is commonly associated with some degree of lower limb weakness often severe enough to be described as paralysis by the mother. We aimed to produce rapid reliable analgesia with no motor block throughout labour. We report a pilot survey of 300 consecutive women requesting regional analgesia in labour who received a combined spinal epidural blockade (CSE). The initial dose was given into the subarachnoid space and analgesia maintained via an epidural catheter. A subarachnoid injection of 2.5 mg bupivacaine and 25 mug fentanyl was successfully given in 268 women (89.3%). Completely pain-free contractions within 3 min of this injection occurred in 195 women (65%) and in all 300 within 20 min and there was no associated motor block in 291 (97%). 141 women chose to stand, walk or sit in a rocking chair at some time during labour. Only 38 women (12.6%) were immobile during the first stage of labour. Analgesia was maintained via the epidural catheter with bolus doses of 10-15 ml of 0.1% bupivacaine and 0.0002% fentanyl. The mean bupivacaine requirement was 9.5 mg/h throughout the entire duration of analgesia. The incidence of post lumbar puncture headache was 2.3%. Transient hypotension occurred in 24 women (8%) and was treated with 6 mg intravenous boluses of ephedrine. Complete satisfaction with analgesia and mobility was reported 12-24 h post partum by 95% of mothers. The use of this analgesic technique caused no alteration in obstetric management or post partum care of the women.

Single space combined spinal-extradural technique for analgesia in labour.

We have used the single space combined spinal-extradural technique for mothers requesting analgesia in labour. Intrathecal plain bupivacaine 5 mg produced a median time to analgesia of 3 min. There was inadequate abdominal analgesia after 10 min in 16% of recipients, although all had good perineal analgesia. The median height of block was T8 (range T4-L2) and mean duration of analgesia 72 (SD 21) min. Hypotension occurred in two of 30 mothers, but responded to fluids and ephedrine. There were no post-spinal headaches. This technique is suitable for those parturients requesting analgesia in active labour who may not have time to achieve extradural analgesia before delivery. The extradural catheter is used to improve analgesia if the subarachnoid block is inadequate, or if labour continues beyond the duration of the subarachnoid block.

Clinical use of a small soda lime canister in a low-flow to-and-fro system.

It may be possible to overcome the classical disadvantages of a to-and-fro system by the use of a small soda lime canister. We report our experience of such a system in a series of 13 adult patients requiring mechanical ventilation of the lungs during surgery. The system was found to be convenient to use and the charge of soda lime had sufficient absorptive capacity to last throughout the great majority of surgical cases. Using a fresh gas flow of 1 l.min-1, the ratio of inspired isoflurane concentration to isoflurane vaporizer setting was found to be approximately one half after 10 min of anaesthesia. This ratio was maintained throughout the procedure, except for a few minutes following each change in vaporizer setting. A to-and-fro system using a small soda lime canister is a convenient alternative to the circle system for low-flow anaesthesia.

A low-flow to-and-fro system. Laboratory study of mixing of anaesthetic and driving gases during mechanical ventilation.

The insertion of a long deadspace tube between an anaesthetic breathing system and a ventilator produces only imperfect separation of the breathing system gas from the driving gas. This laboratory study has investigated different connecting tubes to establish the maximum tidal volume possible before ventilator gas contaminates the gas in a low-flow to-and-fro system (fresh gas flow 1 litre/minute). A larger volume tube enables the use of larger tidal volumes, and plastic corrugated tubes are slightly better than black rubber corrugated tubes in this respect. The maximum tidal volume possible without contamination decreases as ventilatory rate increases, but the maximum minute volume is increased. A 22 mm plastic corrugated tube of internal volume 1.5 litres should be adequate for clinical use with the to-and-fro system described in this study at a fresh gas flow of 1 litre/minute.

Evaluation of a small soda lime canister in a to-and-fro system.

The main disadvantages of the to-and-fro system (the bulky canister and the progressive increase in apparatus deadspace) may be overcome by the use of a smaller canister. In this laboratory study, we have evaluated a 160 g canister in a low-flow to-and-fro system (fresh gas flow 1 litre/minute). Two carbon dioxide productions of 150 and 200 ml/minute were simulated. The mean times to exhaustion, defined here as a 0.5 kPa rise in end-tidal PCO2, were 112 and 79 minutes in the 150 and 200 ml/minute carbon dioxide groups respectively. Ventilation to normacapnia or hypocapnia did not affect the times to exhaustion. The soda lime absorbed 16 litres of carbon dioxide before exhaustion, and this was not affected by minute volume or carbon dioxide production. A small soda lime canister is suitable for carbon dioxide absorption in a low-flow to-and-fro system for ventilated adults.