Unilateral epidural analgesia

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22

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ANESTHESIA

JANUARY

1967

CASE REPORT

Unilateral epidural analgesia AJEET SLNGH, MB, BS,

DA(Bombay)

Assistant Professor of Anssthesiology B.Y.L Nair Hospital Bombay, India

Unilateral epidural analgesia is not a common occurrence. It is, therefore, thought to be worthwhile to record an experience of a recent case. HISTORY

A male patient aged 40, who had had a right sided herniorrhaphy two and a half years previously under spinal analgesia, was admitted for repair of bilateral inguinal herniae. Physical examination did not reveal any abnormality. Blood pressure was 130/80mm/Hg, haemoglobin 80 % and chest radiograph, ECG and urine were normal. PROCEDURE

Herniorrhaphy on the left side and hernioplasty on the right side with a fascia lata graft from the right thigh was planned and continuous epidural analgesia was chosen in view of the probable duration of the proposed procedure. The puncture was made between L3-4 with a No. 16 Tuohy’s needle with Huber point. After location of the epidural space by the ‘hanging drop method’ an epidural catheter was passed through the Tuohy’s needle up to lOcm mark in a cephalad direction. A test dose of 5ml of 2% lignocaine was given and, after waiting for 5 minutes, an additional 20ml of lignocaine was injected at 9.20 a.m. At the same time 50mg of pethidine was given intravenously. The operation on the right side started at 9.30 a.m. The analgesia and muscle relaxation were very good and hernioplasty (Gallies repair) was undertaken; the fascia lata graft was obtained from the right thigh. At 10.50 a.m. a further 7ml of lignocaine were administered because the effect of the initial dose was wearing off. Hernioplasty on the right side was completed at 11.50 a.m. An attempt was made to make the incision for the left herniorrhaphy but the patient felt severe pain; an additional 7ml of lignocaine was injected through the catheter. This dose was ineffective and a further 147

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7ml was given at 12.00 noon. Even after this second dose the patient stili felt pain on pinching the skin with toothed dissecting forceps. No further epidural injection was made; the herniorrhaphy on the left side was completed under a field block. At the end of the operation a radiograph of the lumbar spine was taken after 3ml of 'Myodil' had been injected into the epidural space. The antero-posterior view of the spine showed a unilateral distribution of the dye, which was confined mostly to the right side of the space (figure 1). The patient was then placed in the left lateral

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position for 5 minutes, but a film taken after this showed no change, with the exception of a small area which is indicated by the arrow in figure 1. The dye did not fill the left side of the epidural space. The patient was discharged on the ninth post-operative day without complication. DISCUSSION

Three causes of unilateral epidural analgesia have previously been suggested. Thornton1 reports that, in the continuous technique the tip of the catheter may pass into the paravertebral space and result in incomplete unilateral analgesia or that the spread of the drug may be prevented by the presence of fibrous septa or strands in the epidural space. Vandam2 believes that a congenital midline tissue membrane barrier may be present. In this case the radiograph showed that the catheter had not gone into the paravertebral space (figure 1). The possibility of a congenital midline tissue membrane can also be excluded because some of the dye has actually gone into the left side of the epidural space (indicated by the arrow), which indicates that the adhesions are irregular. In view of the history of previous herniorrhaphy under spinal analgesia, it is probable that a post-spinal adhesion had formed in the epidural space which prevented the spread of the lignocaine to the left side. Before the surgical incision was made abdominal muscle relaxation was checked by asking the patient to cough. In retrospect, we feel that there was bulging of the right side of the lower abdomen only which should have suggested the unilateral effect, but, as we had not previously encountered a case of unilateral analgesia, the importance of this sign was not appreciated. SUMMARY

A case of unilateral epidural analgesia is reported and the reasons for its occurrence discussed. Acknowledgement I am thankful to the Dean of the B.Y.L Nair Charitable Hospital and Topiwala National Medical College for his kind permission to publish this paper. References

and KNIGHT, P.F. (1965). Emergency Anesthesia, 1st edition, p. 153, London, Arnold A VAN DAM, L.D. (1966). Personal communication ITHORNTON, H.L.