Correspondence technique. Crawford [2] reported 302 such cases: following catheter resiting, test doses identified two subarachnoid blocks, but no total spinal or unexpectedly high blocks occurred. On the other hand, Hodgkinson [3] reported three total spinal anaesthetics in his series of 31 patients whose catheters had been resited at an adjacent interspace following ADP. Similarly. Collier [4] described three cases of subdural block occurring after catheter replacement in 59 patients. Even apparently normal epidural analgesia after resiting may be falsely reassuring. Park [5] described a case of high block with marked hypotension following a 4 ml epidural top-up 3.5 h after ADP and catheter resiting. Investigating a similar case, Leach and Smith [6] obtained radiological confirmation that local anaesthetic had spread into the subarachnoid space from a catheter resited epidurally. Attempts to resite the catheter may of course lead to further ADP and one eminent author [7] has stated that when this occurs epidural analgesia should be abandoned and other methods used. Where does this leave the patient who has requested epidural analgesia because other methods have proved inadequate? An alternative is deliberately to insert the catheter into the subarachnoid space and we have managed two ADPs in this way, providing analgesia for labour by a continuous subarachnoid technique. Possible advantages of doing this are that the anaesthetist is sure of the catheter's position, analgesia should be achieved with a very small dose of local anaesthetic, the block could easily be extended to provide anaesthesia for Caesarean section or forceps delivery. Unfortunately, insertion of the catheter does not reduce the incidence of headache in parturients [8]. Continuous subarachnoid analgesia for labour has been described previously [9, lo]. This is not a new technique and has been reported before [8, 1 I ] but we are surprised that it has not been

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debated in print in the light of the available literature. We would be interested to hear of others' experience with this method of managing ADP in labour. Royal Infirmary. Edinburgh E H 3 9YW

C.P.J. MORTON D.G. SWANN

Rejerenceh [I] OKELLRW, SPRIGGE JS. Unintentional dural puncture; a survey of recognition and management. Anaesthesiu 1987; 42: I 1 10-3. [2] CRAWFORD JS. Collapse after epidural injection following inadvertent durdl perforation. Anesthesiology 1983; 59: 78-9. [3] HODGKINSON R. Total spinal blockade after epidural injection into an interspace adjacent to an inadvertent dural puncture. Anesthrsiologv 1981; 55: 593-5. [4] COLLIER c. Collapse after epidural injection following inadvertent durdl perforation. Anesthesiology 1982; 57: 427-8. [5] PARKR. A migrating epidural catheter. Anaesthesia 1984; 39 289. GB. Subarachnoid spread of epidural local [6] LEACHA, SMITH anaesthetic following dural puncture. Anaesthesia 1988; 43 6714. [7] CRAWFORV JS. Principles and practice of obstetric anaesthesia. 5th edn. Blackwell Scientific Publications, 1984: 215. [8] NORRISML, LEIGHTON BL. Continuous spinal anesthesia after accidental dural puncture in parturients. Regional Aneslhesia 1990; 1 5 285-7. SL, CERAVOLO AJ, FOLDSAF. Continuous drop [9] CARPENTER subarachnoid block with procaine solution for labour and delivery. American Journal of Obsrelrics and Gynecology I95 I ; 61: 1277-84. [ 101 BENEDETTI c, TIENGO M. Continuous subarachnoid analgesia in labour. Lancer 1990; 335: 225. [ I I] COHEN S. DAITCH JS, GOLVINER PL. An alternative method for management of accidental durdl puncture for labour and delivery. Anesthesiolngy 1989: 7 0 164-5.

A technique to avoid dural puncture by the epidural catheter Drs Hughes and Oldroyd recommend a technique to avoid a 'potential' problem associated with the double needle technique of combined subarachnoid and epidural block (Anaesthesia 199I ; 4 6 802). Unfortunately the technique described of rotating the Tuohy needle through 180" is associated with a documented incidence of dural puncture. Meiklejohn [I] described a study which showed that rotation of the epidural needle significantly decreases the force required to produce a dural puncture. Hollway and Telford's study [2] on intentional dural puncture with a Tuohy needle showed that 10% of their patients had successful dural punctures when the needle was rotated within the epidural space without being advanced further. I disagree with the authors and would suggest that the

theoretical advantages of Rawal's technique d o not outweigh the published hazards of rotating a Tuohy needle within the epidural space. Department of Anaesthesia, Hull Royal InJrrnary, Hull H U 3 2JZ

P.J. TOOMEY

References [ I ] MEIKLEJOHN BH. The effect of rotation of an epidural needle: an in vitro study. Anaesthesia 1987; 4 2 1180-2. [2] HOLLWAY TE. TELFORD RJ. Observations on deliberate dural puncture with a Tuohy needle: depth measurements. Anaesthesia 1991; 46: 722-4.

Focal seizure following enflurane We wish to report the following incident. A-50-year-old man presented for arthroscopy and meniscectomy. He gave an 8-day history of low back pain, for which he had taken methocarbamol (Robaxin, Wyeth) 5 days before his admission. He was otherwise fit and was taking no other medication. N o premedication was ordered. Anaesthesia was induced with thiopentone 350 mg and alfentanil 750 pg intravenously and maintained with 1.5 - 2% enflurane in nitrous oxide and oxygen (30%) breathed spontaneously. Surgery proceeded uneventfully, lasted 40 min, and the

patient awoke in recovery 5 min after the end of the operation. A few minutes later his left arm, shoulder, and cheek were noticed to be twitching. Although distressed, his level of consciousness was not impaired, and throughout he was able to answer simple questions. Increments of diazepam totalling 20 mg were given intravenously and resulted in a diminution of the twitching. However, a further 10mg were needed some 30min later before the movements were totally abolished. On further questioning the patient stated he had taken a single dose of methocarbamol 5 days before the