EXTRADURAL MORPHINE AND PAIN RELIEF FOLLOWING EPISIOTOMY

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1 EXTRADURAL MORPHINE AND PAIN RELIEF FOLLOWING EPISIOTOMY R. MACDONALD AND P. J. BICKFORD SMITH One hundred and fifty obstetric patients, who had received intrapartum extradural analgesia with bupivacaine, and h«h required episiotomy, were given a final postpartum injection of preservative-free morphine in saline, or saline alone, on a double-blind basis. The degree of perinea] analgesia was assessed by linear analogue scale at intervals up to 6h, and oral analgesic requirements were recorded. A significant degree of analgesia was obtained for up to h with morphine mg, compared with saline. Increasing the dose to mg increased the occurrence of side-effects, and was associated with less marked analgesia Episiotomy is common. The true incidence depends on many variables, but may be as high as 9% in patients delivered in hospital (Buchanand Nicholls, 9). In our unit the incidence has doubled since 97. In their study, Buchan and Nicholls (9) noted that 5% of patients required analgesics regularly (by mouth) for up to 6 days, and demonstrated that those who had received extradural analgesia during labour experienced more pain than those patients managed conventionally, thus confirming Crawford's (97) earlier observation. Following our experience with extradural morphine for the relief of pain following Caesarean section (since 979 it has become our routine technique of providing analgesia for those patients with extradural catheters in situ), it seemed logical to extend the use of extradural morphine in an attempt to alleviate the pain associated with episiotomy in patients who had received extradural analgesia during labour. PATIENTS AND METHODS Following permission from the local medical ethics committee, a randomized double-blind study was undertaken. All patients had adequate extradural analgesia with bupivacaine for pain relief in labour. A full explanation of the nature and purpose of the study was given to the patients. They were propped up on pillows and "topped-up" from a numbered randomized ampoule, following suture of the episiotomy, before the effects of the last administration of bupivacaine had worn off, since extradural morphine has a variable, and sometimes, slow onset of ROSEMARY MACDONALD, PH.D., F.F.A.R.CS.; P. J. BICKFORD SMITH, MA, CH.B., F.F_A.RX.S.; Department of Anaesthesia, St James's University Hospital, Beckett Street, Leeds, LS9 7TF. action (Chambers, Sinclair and Scott, 9). The patients were assured that oral analgesics, tablets of either paracetamol mg or "Distalgesic" (dextropropoxyphine hydrochloride.5 mg and paracetamol 5 mg) would be freely available for treatment of perineal pain, if required. The code for the ampoules was held by the Pharmacy Department and not broken until the end of the study. One hundred and fifty patients entered the study; 6 were discarded because of incomplete data, leaving the following three groups: patients who received preservative-free morphine mg in isotonic saline ml (-mg group); 9 patients who received similarly morphine mg in isotonic saline ml (-mg group); patients who received physiological saline ml only (saline group). Patients in each group were of a similar age and had comparable modes of delivery (table I). Assessment of pain was by use of a -cm linear analogue scale (Bond and Pilowsky, 966) and by an assessment of the requirements for analgesics by mouth. Number Age range (yr) Primigravida Spontaneous vertex delivery Neville-Barnes forceps Kiellands forceps Breech Twins Ventouse TABLE I. Details of patina Extradural morphine mg The Macmillan Press Ltd 9

2 BRITISH JOURNAL OF ANAESTHESIA Patients were assessed formally at,,,,, and 6 h following the injection from the coded ampoule. Patients were found to be asleep only when the assessment times occurred between midnight and 6. h. Therefore, it was assumed that they had no pain at those times and a zero score was allocated. At each assessment, enquiry was made regarding the occurrence of untoward symptoms such as pruritus, nausea, vomiting and difficulty with micturition. Statistical analyses included the x test, and the Mann-Whitney test of non-parametric data (Swinscow, 9). TABLE n. Mean pain scores standard dtviation at each assessment time Time(h) 6 Extractural morphine mg ±.97.7± O± RESULTS Pain scores On viewing the linear analogue scales it was apparent that a large number of patients marked the scale at the zero end, that is they felt they had no pain. Chi-squared analyses showed that a significant number of patients were pain free for up to h ( h X = 6.5;. > P<.5). When the groups were analysed separately using + contingency tables (Swinscow, 9), a significant number of patients in the -mg group had no pain at h (x =.7; P<O.OOl)andh(x = 5.;O.5>.P<.O),but in the -mg group this number was significant only at h(x =.7;.5 >P<.). A histogram was then constructed showing the percentage of patients in each group at each assessment time, who indicated the presence of pain (fig. ). As expected, for up to h a higher percentage of the saline group had pain, but by and 6 h pain was commoner in both morphine groups. Other than at and h, there appeared to be very little difference between the -mg and -mg groups. A pain score for each assessment time, for each patient, was obtained by measuring to the nearest.5 cm, the distance of each mark from the zero end of the scale. Table II shows the mean pain scores ± standard deviation. When the morphine groups were compared with the saline group it was found that both mg and mg of extradural morphine conferred significant pain relief for up to h (for P values see tables). Thereafter, there was no significant difference; neither was there any difference between the -mg and -mg groups (table III). 9 ~ 7 6 I M to I * Time following top-up (h) FIG.. Percentage of patients in pain at each assessment time.

3 EXTRADURAL MORPHINE AND EPISIOTOMY PAIN TABLE HI. Significance of difference between pain scores for each group (Mam Whitney test) Time(h) mg/salinc mg/saline P>.<. P<.5 Analgesic requirements Table IV shows the number of patients in each group who required oral analgesics. These patients were not excluded from the trial. In the saline group a significant number of patients required analgesics for up to h. In general, the analgesic requirements paralleled the pain scores. Side effects Pruritus. Thirty-one patients in the -mg group and in the -mg group complained of itch. The distribution of the pruritus tended to be over the thighs and the trunk. Three patients were itchy all over and a few complained of facial heat about h following top-up. Five patients requested treatment for the pruritus. Nausea and vomiting. Twelve patients in the -mg group and nine in the -mg group vomited. Many more patients were nauseated, especially at h. The patients found the nausea very distressing. In the saline group two patients vomited and a further three were nauseated all before the administration of the extradural saline. No patient in this group recorded nausea or vomiting at any assessment time. Retention of urine. This occurred in patients in the -mg group (one twin forceps delivery, six forceps and three spontaneous deliveries), one in the -mg group (a forceps delivery) and five in the saline group (three forceps and two spontaneous deliveries). TABLE IV. Analgetic requirements of tach group at each assessment time Time(h) 6 Extradural morphine mg P. >P<.. >P<. n.s. n.s. DISCUSSION It is now well established that the extradural administration of morphine produces postoperative analgesia (Behar et al., 979; Bromage, Camporesi and Chestnut, 9; Rawal, Sjostrand and Dahlstrom, 9; Weddel and Riller, 9; Lanz et al., 9). This is the first reported study of its use to relieve the pain associated with episiotomy. Although it may be suggested that episiotomy pain is no different from any other postoperative pain, its site restricts mobility and causes much distress in a group of patients who would otherwise be mobile (Buchan and Nicholls, 9; Reading et al., 9). In our unit episiotomy is commoner in patients receiving extradural analgesia ( spontaneous vaginal deliveries with extradural analgesia: 6 episiotomies; spontaneous vaginal deliveries with systemic and inhalation analgesia: 5 episiotomies) and these patients have more pain after episiotomy than those having conventional analgesia (Crawford, 97; Buchan and Nicholls, 9). Therefore, it seemed reasonable to assess the efficacy of extradural morphine in the relief of episiotomy pain, especially since the patients had an extradural catheter in situ. The study has shown that, following episiotomy, the administration of morphine to the extradural space will maintain a significant number of patients pain free for up to h, whereas mg will do so for only h. Both and mjr will provide significant analgesia for h when compared with the extradural injection of physiological saline. This is further verified by the observation that the patients in both morphine groups required significantly less analgesia by mouth during the first h than those in the saline group. It is not clear why mg of extradural morphine should render patients painfree for h and mg for only h, although the duration of significant analgesia with both doses was the same. It may be that the higher dose inhibits secretion of endogenous opiates and adversely affects the quality of subsequent pain relief. The price for this pain relief is the incidence of side effects. Pruritus occurred in 7% of the -mg group and 59% of the -mg group, an incidence higher than that reported by Lanz and colleagues (9) or Rawal, Sjostrand and Dahlstrom, (9). Only five patients requested treatment. Antihistamines, for example chlorpheniramine i.m., proved helpful. Nausea and vomiting were more troublesome (Lanz et al., 9) and were frequently worse at about - h, which was when patients

4 BRITISH JOURNAL OF ANAESTHESIA who had a vaginal delivery were mobilized. This was not a problem in patients following Caesarean section, who were mobilized later. In addition, they had syntocinon as an oxytocic agent, whereas the other patients received routinely "Syntometrine" i.m. which contains ergometrine 5 fig. Although it is unlikely that the emetic side-effects of ergometrine alone would persist for h, it may be that the combination of ergometrine, extradural morphine and mobilization contributes towards the nausea and vomiting It has been suggested that these side effects are not caused by histamine release, but are indicative of rostral spread (Bromage et al., 9) and certainly a few of our patients did complain of facial heat about h following the injection. However, we found anti-histamine drugs (chlorpheniraminei.m. for the pruritus and prochlorperazine i.m. for nausea and vomiting) to be more useful and effective than naloxone i.v. Retention of urine following extradural morphine has been well documented (Weddel and Riller, 9; Lanz et al., 9). Since morphine increases the tone of the detrusor and vesical sphincter, thus impeding micturition (Lanz et al., 9), the incidence of retention of urine would be expected to be high in obstetric patients, especially since many required forceps deliveries. While patients in the -mg group and only one in the -mg group required catheterization, it must be noted that five patients in the saline group also had retention of urine. We did not feel that, in this study, it was particularly related to mode of delivery. Respiratory depression following the administration of extradural morphine has been reported (Bromage, Camporesi and Chestnut, 9; Bromage et al., 9; Rawal, Sjostrand and Dahlstrom, 9; Weddel and Riller, 9). Nielson and coworkers (9) compared the effects of i.v. and extradural morphine on carbon dioxide sensitivity and demonstrated a delayed effect of extradural morphine coincidental with cephalad spread. However, they had used extradural morphine mg and in many of the other reports, as summarized by Barron and Strong (9), patients had coincidental administration of systemic narcotics or were elderly and systemically ill. We have now given extradural morphine to approximately patients (unpublished results). One developed clinical evidence of respiratory depression which responded to naloxone i.v. However, since she was receiving chlormethiazole i.v. she should not have had extradural morphine in addition. It may be suggested that it is not worthwhile giving extradural morphine if analgesia is adequate for h only. Obstetric patients will volunteer that the discomfort as the local anaesthetic is wearing off is considerable and adequate pain relief without the systemic effects of i.m. opiates is welcome at this time. One unexpected finding was the low pain scores in the saline group, for example the highest mean pain score was only.6 at h. Perhaps pain following episiotomy is not as great a problem as w.e anticipated. This, plus the incidence of side effeclis would lead us to recommend that extradural morphine, in a dose of mg, be reserved for patients expected to experience more severe episiotomy pain breech and twin deliveries, extended episiotomy, and so on. Since the larger dose ( mg) appeared to have no advantage as far as the relief of pain was concerned, and was associated with a higher incidence of side effects, we would not recommend its use in this context. Nevertheless, despite all the side effects, our midwives, obstetric physiotherapists and obstetricians have become enthusiastic about the degree of analgesia and subsequent mobility which extradural morphine affords the patient. REFERENCES Barron, D. W., and Strong, J. E. (9). Post operative analgesia in major orthopaedic surgery. Anaesthtsia, 6,97. Behar, M., Majora, F., Olshwang, D., and Davidson, J. T. (979). Epidural morphine in treatment of pain. Lanctt,, S7. Bond, M. R., and Pilowsky, I. (966). Subjective assessment of pain and its relationship to the administration of analgesia in patients with advanced cancer. /. Psychosom. Res.,,. Bromage, P. R., Camporesi, E., and Chestnut, D. (9). Epidural narcotics for postoperative nnnlgr«ia Anath. Anaig., 59,7. Durant, P. A. C, and Nielson, C. H. (9). Rostral spread of epidural morphine. Antsthtsiology, 55,9. Buchan, P. C, and Nicholls.J. A. (9). Pain after episiotomy a comparison of two methods of repair. /. R. Coll. Gen. Praa.,,97. Chambers, W. A., Sinclair, C. J., and Scott, D. B. (9). Extradural morphine for pain after surgery. Br. J. Anattth.,,9. Crawford, J. S. (97). The second thousand epidural blocks in an obstetric hospital practice. Br. J. Anatsth.,,77. Lanz, E., Theiss, D., Riess, W., and Somner, U. (9). Epidural morphine for post operative analgesia: a double blind study. Anath. Analg., 6,6. Nielson, C. H., Camporesi, E. M., Bromage, P. R., Bukowski, E. M., and Durrant, D. A. C. (9). CO sensitivity after epidural and intravenous morphine. Antsthtsiology, 55, 7. Rawal, N., Sjostrand, U-, and Dahlstrom, B. (9). Post opera-

5 EXTRADURAL MORPHINE AND EPISIOTOMY PAIN 5 tive pain relief by cpidural morphine. Anaask. Analg., 6,76. Reading, A. E., Sledmere, CM., Cox, D. N., and Campbell, S. (9). How women view episiotomy pain. Br. Med. ].,,. Swinscow, T. O. V. (9). Statistics at Square On*, pp. 5, 57. Br. Med. J. London: Dawson and Goodall Ltd. Weddel, S. J., and Riller, R. (9). Serum levels following epiduial administration of morphine and correlation with relief of post-surgical pain. Aiusthtsiology, 5,. EXTRADURALE MORPHIUMGABE UND SCHMERZSTUXUNG NACH EPISIOTOMIE ZUSAMMENFASSUNG An 5Frauen,diew&hrertdderGeburteineExtraduralanalgesie mit Bupivacain und cine Episiotomk erhalten hatten, wurde postpartal doppelblind freies Morphium in Elektrolytlosung oder Elektrolytlosung alleine eztradural injizkrt. Der Grad der perinealen Analgesie wurdc mit einer linearen Analogskala uber bis zu 6 Stunden bestimmt, der Bedarf an oralen Analgetika erfafit. Mit mg Morphium wurde ein im Vcrgleich zur Elektrorytldsung signifikanter Analgesiegrad uber bis zu Stunden erzielt. Eine Dosiserhahung auf mg hlhrte zu einer Haufung von Nebenwirkungen und weniger deutlicher Analgesic. MORFNA EXTRADURAL Y ALIVIO DEL DOLOR DESPUES DE EPISIOTOMIA SUMAJUO Se administro a SO pacientes de obstetricia que habian rcobido una analgesia extradural intraparto con bupivscaina y necesitaron una episiotomia, una inyeccion final post-parto de morfina libre de preservativos en sohicion salina o una tolucion salina sola en una base doble-cdega. Se evalu6 el grado dc analgnia perinea mfhiant** una escala nnilnga linear a intervalos de hasta 6 h y se registraron lo» requerimientos de analgesia oral. Se obtuvo un grado significante de analgesia hasta h con mg de morfina en comparacion con la sohicion salina. Al incrementar la dosis hasta mg, se aumento la ocurrencia de efectos secundarios y la analgesia fue menos marcada.