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Summary This study compared the posterior and popliteal fossa approaches for sciatic nerve block. Patients scheduled to undergo foot surgery were allocated randomly into one of two groups: group A (n = 20) received sciatic nerve block via the posterior approach and group B (n = 20) received a block using the popliteal fossa approach. All blocks were performed with the aid of a peripheral nerve stimulator and alkalinised 0.5% bupivacaine with 1 in 200 000 adrenaline was injected in a dose of 2 mg.kg Nineteen of 20 blocks in group A were successful compared with nine of 20 in group B (p < 0.01). There was no significant difference between the groups in respect of time to onset or duration of block. Patients in group B reported less discomfort during performance of the sciatic nerve block but required supplementary nerve blocks more frequently. We recommend the use of the posterior approach for sciatic nerve block.

Pelvic brachytherapy presents the anaesthetist with numerous challenges. Patients vary from highly distressed young adults, to the elderly with coincidental disease severe enough to preclude surgery. The painful radioactive implants remain in place for a number of days. Treatment in isolated rooms reduces radiation exposure to staff, but makes close postoperative monitoring difficult, so the analgesic technique should involve minimum risk to the patient. Although there is very little published evidence of specific analgesic techniques in this area, knowledge of these problems allows the anaesthetist to select appropriate systemic analgesics and regional blocks to provide safe and effective pain relief.

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SummaryThis Key wordsAnaesthetic techniques, regional; sciatic nerve block. Anaesthetics, local; bupivacaine.Sciatic nerve blockade is a useful technique for providing intra-operative and postoperative analgesia for many operative procedures on the foot and lower limb. It is our practice to use bupivacaine for this purpose since it has a long duration of action in comparison to other agents currently available. The main disadvantage is its prolonged latency before satisfactory blockade is achieved.Local anaesthetic agents are weak bases prepared commercially as acidic salts to aid solubility and stability in solution. It has been demonstrated that the charged cationic molecule is required for conduction blockade while the uncharged base is necessary for adequate tissue p e n e t r a t i~n .~-~ The proportion of each will depend on the pKa of the agent and the ultimate pH of the solution. By raising the pH of the local anaesthetic solution nearer to the physiological range, the fraction of uncharged base available for tissue penetration will be increased. Recent studies have shown that latency and duration of action of both lignocaine and bupivacaine can be favourably altered by this m e t h~d .~-~ The purpose of this present study was to assess whether alkalinisation of bupivacaine produced any effect on the latency or duration of action of sciatic nerve blockade and to examine whether the systemic absorption of local anaesthetic is altered with the modified solution.

Fentanyl by continuous i.v. infusion (1.5 microgram kg-1 min-1 or 0.5 microgram kg-1 min-1) was compared with placebo infusion as an analgesic regimen for 24 h after hysterectomy. The drugs were infused using a new disposable device which required no external power source. All patients were allowed morphine i.m. if they experienced pain. Patients in the higher dose fentanyl group demanded less i.m. morphine and had better pain relief after operation, without important respiratory depression.

The Finapres was compared with direct intraarterial pressure monitoring in 10 patients undergoing local resection of choroidal melanoma, an operation that requires a period of profound hypotension. Good agreement was recorded for systolic arterial pressure and heart rate over a range of pressures. However, agreement of mean and diastolic pressures was poor, with the Finapres tending to overestimate these values. In cases requiring profound hypotension, direct arterial pressure monitoring remains the method of choice.