Correspondence the dural puncture, although it was thought unsafe to use it for postoperative analgesia on the ward. We believe that the leak from the E521 Everett 16 G Touhy needle contributed to the dural puncture by decreasing the change in loss of resistance with normal saline. The defect was not visible on inspection nor was it obvious unless injection through the needle was against resistance. We concluded that as with all anaesthetic equipment the Touhy needle should be tested for leaks prior to its use and that a visual inspection is not sufficient. Royal Hallamshire Hospital, Shefield

A.T. WILSON L. HAWTHORNE

A reply

Thank you for the opportunity to respond to the letter from Drs Wilson and Hawthorne. The authors describe an inadvertent incident where an E521 Everett 16 G Tuohy Needle may have contributed to dural puncture. The problem appears to be that this particular needle

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had a leak a t the hub/needle blade junction which was not apparent to the initial operator as a loss of 'feel'. Some 2 years ago, our supplier improved the method of 'crimping' the hub to the needle blade in response to an earlier report of inadequate security, which was not associated with inadvertent dural tap [I]. Although batch indentification was not possible in the case reported by Drs Wilson and Hawthorne, we believe that the needle predates this improvement. Certainly, there have been no similar reports concerning needles made with this enhancement. The product complies fully with the relevant British Standard, BS6196: 1990. Quality Assurance Manager, Avon Medicals Ltd, Redditch. Worcestershire B98 9HA

J. ANDREWS

Reference [ I ] HEARNM . Breakage of disposable needles. Anaesthesia 1990; 4 5 698.

Transdermal hyoscine and confusion in the elderly We read with interest the conclusions of Dr P. Semple et al. (Anaesthesia 1992; 47: 399-401) in their paper regarding the use of transdermal hyoscine patch for antiemesis in patients using postoperative patient-controlled analgesia. We have had equally disappointing results using transdermal hyoscine in conjunction with postoperative fentanyl/bupivacaine epidural infusions. In addition, we noted the predictable but significant side effect of postoperative agitation and confusion, which drastically reduces the applicability of this method of antiemesis in the elderly. We chose to study 30 patients (age range 54 to 80 years) presenting for either total hip or total knee replacement. They were randomly allocated into one of two groups of 15 each. Patients in group 1 had the hyoscine patch (Scopoderm TTS, CIBA) applied one hour pre-operatively, while those in group 2 received placebo. Premedication consisted of temazepam 10-20 mg administered orally 1-2 h pre-operatively. A standardised combined spinal/ epidural technique was used and intra-operative sedation provided with propofol (2 mg.kg-'.h-'). Postoperative analgesia was maintained by epidural infusion, with a mixture of 0.25% bupivacaine with fentanyl 25 pg.ml-l

(1-3 m1.h-I). The fasting regimen was standardised and all patients were offered breakfast o n the first postoperative morning. They were assessed for 48 h postoperatively for nausea and vomiting and also on a simple 10 point orientation scale (name, date, place, etc). Patients with persistent nausea and/or vomiting were given prochlorperazine 12.5 mg by deep intramuscular injection. In the hyoscine patch group, three patients experienced some degree of nausea and /or vomiting, compared to six in the control group. This was not statistically significant.Urinary retention occurred in four patients in each group, and these patients required catheterisation. Disorientation occurred in six out of 15 patients of the hyoscine group, while this was not seen in the controls This was both clinically and statistically significant (p < 0.01). This was not an entirely unexpected finding in this group, and despite the theoretical advantages of using this simple and noninvasive delivery system, we feel that transdermal hyoscine is both ineffective and unsuitable for use in this situation. Crosshouse Hospital, Kilmarnock

M .R . CHECKETTS D.M. COVENTRY

Propofol in hyperkalaemic periodic paralysis A recent article (Anaesthesia 1992; 47: 579-84) described the safe use of thiopentone to induce anaesthesia in four patients who had the rarer of the two forms of potassiumassociated familial paralysis. We report a patient with this condition in whom propofol was used uneventfully in this condition. A 22-year-old female student was admitted for excision of a small fibroadenoma of the breast. She was known to suffer from familial hyperkalaemic periodic paralysis for which she took hydrochlorthiazide 25 mg daily. Pre-operatively her serum potassium was 3.1 mmol.l-'. She was premedicated with diclofenac 100 mg and metoclopramide 10 mg orally. Following intravenous administration of fentanyl 75 pg and droperidol 0.75 mg, anaesthesia was induced with propofol 120 mg and maintained with a propofol infusion, supplemented by nitrous oxide in oxygen via a face mask. She received

230 mg of propofol in total. There were no intra-operative problems and immediately postoperatively her potassium was 4.1 mmol.l-'. Recovery was uneventful and she was discharged from hospital the following day. The use of propofol in familial periodic paralysis has been described only in the more common hypokalaemic form [l]. We believe this to be the first report of the safe administration of propofol in the more rare hyperkalaemic variant. Southampton General Hospital, Southampton SO9 4XY

A.M. CONE A.J. SANWME

Reference [I] WALSHJF, SIDDIQM. Propofol and atracurium in familial periodic paralysis. Anaesthesia 1989; 44: 1012.

Propofol in hyperkalaemic periodic paralysis.

Correspondence the dural puncture, although it was thought unsafe to use it for postoperative analgesia on the ward. We believe that the leak from the...
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