Anaesthesia, 1991, Volume 46, pages 404-407

Forum Wound infiltration of local anaesthetic after lower segment Caesarean section T. N. Trotter, FCAnaes, Lecturer, P. Hayes-Gregson, FFA(SA), Senior Registrar, S. Robinson, BA, Research Sister, L. Cole, FFARCS, Lecturer, S. Coley, F F A R C S , Senior Registrar, D. Fell, FFARCS, Senior Lecturer, University Department of Anaesthesia, Leicester Royal Infirmary, Leicester LE1 5WW

Summary The analgesic eficacy .f subcutaneous wound injiltration with 20 ml of0.5% bupivacaine after elective lower segment section Cuesarean section was studied in 28 patients in a double-blind randomised controlled manner using a patient-controlled analgesia system. The mean 24-hour morphine consumption of the placebo group and the bupivacaine group was similar (76 mg and 68 mg respectively). Analysis of the cumulative hourly morphine consumption failed to show any statistically signijicant diflerences between the groups. However, on a weight-adjusted basis statistically significant differences in morphine consumption were demonstrated, although these may not be clinically important. Subjective experiences of pain, nausea and drowsiness assessed by linear analogue scoring were similar in both groups.

Key words Pain, postoperative; patient controlled analgesia. Anaesthetics, local; bupivacaine. Anaesthetic techniques, regional; wound infiltration.

The beneficial analgesic effect of subcutaneous wound edge infiltration using bupivacaine has been demonstrated following herniotomy in children and after excision of benign breast lumps.'.* However, the beneficial effects are less clear after upper abdominal surgery; reduction in opioid requirement after cholecystectomy has been demonstrated after infiltration of the peritoneum, muscle and subcutaneous tissues, but not after subcutaneous infiltration a l ~ n e . The ~ . ~ opioid-sparing effect of subcutaneous wound infiltration with local anaesthetic agents has not been assessed previously after lower abdominal operations in adults, with the exception of herniorrhaphy. Patients undergoing Caesarean section mobilise early and would benefit from a technique which reduces opioid requirements and the incidence of related side-effects, and improves analgesia. Lower segment Caesarean section is performed routinely through a Pfannenstiel incision and is suitable, therefore, for the investigation of supplementary local anaesthetic techniques. The purpose of this study was to assess the value of subcutaneous wound edge infiltration with bupivacaine after elective Caesarean section under general anaesthesia. Analgesia was assessed by reference to the use of intravenous boluses of morphine delivered by a patientcontrolled analgesia system.

Method Twenty-eight patients scheduled for elective Caesarean section under general anaesthesia were investigated in a double-blind, randomised trial. Each patient was visited pre-operatively and familiarised with the use of the PCAS. Patients gave informed consent and the study was approved by the District Ethics Committee. Patients were

not studied if they were unable to comprehend the nature of the assessments or the purpose of the PCAS, gave a history of sensitivity to opioids or local anaesthetics or had severe pre-eclampsia or severe hypertension of pregnancy. Premedication comprised ranitidine 150 mg orally administered on the evening before and on the morning of surgery and 30 ml sodium citrate 0.3 molar given orally immediately before induction of anaesthesia. Intravenous access was established and anaesthesia induced with a sleep dose of methohexitone followed by suxamethonium 1-1.5 mg/kg to facilitate tracheal intubation. Anaesthesia was maintained with 50% N,O in 0, and supplemented with enflurane 1 %. Muscle relaxation was accomplished with atracurium 0.5 mg/kg. The Fro, at delivery was reduced to 0.3, and morphine 5-10 mg and syntocinon 10 IU were given. Atropine 1.2 mg and neostigmine 2.5 mg were administered at the conclusion of surgery to antagonise residual neuromuscular blockade. Patients were randomly allocated between two groups to receive either 20 ml of bupivacaine 0.5% (group B) or a control group receiving 20 ml of normal saline (group C). The solutions were supplied by the hospital pharmacy in numbered vials in order to maintain blinding. After closure of the peritoneum the subcutaneous tissues were infiltrated with the trial solution by the surgeon, subject to a maximum of 0.4 ml/kg (2 mg/kg). Postoperative analgesia was provided by a PCAS (Graseby Medical) connected by a Cardiff one-way valve to the intravenous infusion and provided morphine in 2-mg increments with a lockout time of 10 minutes. The number and timing of requests was recorded by an on-line printer (Hewlett-Packard 82 162A Thermal Printer). Prochlorperazine 12.5 mg intramuscularly was given on request for nausea, and escape analgesia in the form of

Accepted 17 July 1990 0003-2409/9 I /050404 + 13 $03.00/0

@ 1991 The Association of Anaesthetists of Gt Britain and Ireland 404

Forum intramuscular morphine was available to each patient. Patients returned to the ward after a short stay in the recovery area where they were reminded of the correct usage of the PCAS. Pain was assessed by the patient at 2-hourly intervals for the first 24 hours, utilising 10-cm linear analogue scales (LAS) for pain, in addition to ones for nausea and sedation. The assessement was omitted if the patient was asleep. Overall efficacy of analgesia was rated at the end of the 24-hour period using a four-point verbal rating score (VRS) comprising very good, good, moderate, or bad. Systemic arterial pressure, heart rate and ventilatory rate was recorded by the ward nursing staff at regular intervals. The study was terminated at 24 hours, or earlier if mobilisation occurred spontaneously. Parametric data were analysed by Student’s t-test; the Wilcoxon rank sum test was used for the data derived from LAS, and the Chi-squared test for the VRS. A p value of less than 0.05 was interpreted as an indication of statistical significance. Results

Fourteen patients received wound infiltration with bupivacaine (group B) and 14 (group C) received normal saline. There were no significant differences between the two groups with respect to age and height, but a significant difference emerged between the groups with respect to weight (Table 1). The patient weight was that recorded at the booking clinic at between 12 and 16 weeks’ gestation. This was considered to be an adequate estimate of immediate postdelivery weight. There were no patients with multiple pregnancies or pathological causes of excessive weight gain in either group. No problems were encountered with the PCAS in relation to programming or function, but data were lost from two patients in group C when the printer failed to record patient demands and only the 24-hour morphine consumption could be ascertained. Two further patients, one from each group, terminated the study at 20 and 21 hours respectively because of early mobilisation and discontinuation of the intravenous analgesia. In these patients, only data from the first five intervals are included. Morphine consumption was compared over each 4hourly interval, over the first 12 hours and over the 24-hour study period. There were no significant differences between the groups over these intervals; the mean (SD) 24-hour consumption for group B being 68.6 (23.2) mg and for group C 76 (25.2) mg. Total morphine consumption varied widely over 24 hours (group B 30-1 14 mg, group C 44120 mg). Mean morphine consumption/kg body weight over the same intervals was calculated because of the disparity in patient weight. Patients in group B consumed significantly less over the first 4 and 12 hours and over the whole 24hour period. Comparison of the remaining intervals showed no significant differences, with the exception of the period between 12 and 16 hours (Fig. 1 and Table 2). Linear regression calculations were performed to assess correlation between weight and morphine consumption over 24 hours. For group B the correlation was 0.45 and for group C 0.39. Linear analogue scores for pain, nausea and sedation revealed no significant differences between the groups (Wilcoxon Rank Sum test). There was no clinical Table 1. Patient data (mean, SD). group B.

Age; years Height; cm Weight; kg

* p < 0.05 compared with

Group B

Group C

31.6 (5.1) 157.6 (7.1) 70.1 (13.7)

28.7 (4.3) 158.7 (6.7) 58.5 (14.9)*

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5 0.300 2 0.200 C

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Fig. 1. Four-hourly morphine consumption in the saline W ( n = 14) and the bupivacaine 0 ( n = 14) groups. Bars represent SD. * p < 0.05 compared to saline.

evidence of excessive sedation or respiratory depression in any patient in the study. Both groups expressed a high degree of satisfaction with the quality of analgesia provided; the verbal rating assessment of quality of analgesia showed no difference between groups (Table 3). The linear analogue scores for pain, nausea and sedation are shown in Table 4. There were no significant differences at any time. Power analysis was carried out on weight-related and nonweight-related data from a nomogram described by Altman.’ A 33% difference in opioid uptake was set as the minimum clinically important difference between the groups one would wish to detect, and is a similar difference to that demonstrated by other^.^ The number of patients was adequate to detect a difference of this magnitude with a power of 0.8 and p < 0.05 for the 12- and 24-hour periods, but for individual 4-hour intervals a larger study size would have been required. Discussion

This study demonstrates that subcutaneous wound infiltration with bupivacaine 0.5% did not decrease morphine requirements on the first postoperative day. However, if patient weight is taken into account, differences between the groups emerge over 12 hours, 24 hours and in two of the 4-hour periods. Examination of the remaining 4-hour periods demonstrated that there was a high probability of a type 2 error, due to the wide variation in opioid uptake; to achieve an adequate power, large numbers of patients Table 2. Morphine consumption (mg/kg) expressed as mean (SD) during the first 12 and 24 hours of PCAS administration. Both these figures include the 5-10 mg loading dose administered in theatre. *p < 0.05 compared with group B. C , control group; B, bupivacaine group.

12 hours 24 hours

Group B

Group C

0.61 (0.15) 0.97 (0.35)

0.85 (0.28)* 1.36 (0.43)*

Table 3. Patient assessment of quality of analgesia, (number of patients per category and percent). C , control group; B, bupivacaine group.

Bad Moderate Good Very good

Group B

Group C

0 (OY”) 1(7.1%) 5 (35.7%) 8 (57.1 %)

0 (0%) 1 (7.1%) 5 (35.7%) 8 (57.1%)

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would have been required. It was believed that this was unnecessary since a significant difference had emerged over the first 12- and 24-hour period. A large variation in opioid uptake from a PCAS has been shown.('S7Although the relation between weight and opioid uptake was of sufficient magnitude to produce statistically significant differences in this study, others have not found weight to correlate with opioid uptake from a PCAS in a nonpregnant Weight gain in pregnancy arises partially as a result of an increase in extracellular fluid volume which can persist after delivery, so the volume of distribution of intravenous drugs may be altered! This may account for the observed difference in this study between weight-normalised data. However, further evidence of morphine disposition in the puerperium is lacking and these results should be interpreted with caution. The results of this study reaffirm the value of patientcontrolled analgesia after Caesarean section, demonstrated elsewhere.',10In these studies PCAS provided better analgesia and patient satisfaction when compared with intramuscular as required narcotics. In this study PCAS also provided a very high degree of patient satisfaction, with over 90% of patients describing their pain relief as either good or very good. This may have therapeutic implications. Previous studiesI4 have usually relied for assessment upon differences in intramuscular opioid given on request and differences in pain scores. However, numerous factors influence this regimen including inappropriate dosage, delays in drug administration and fear amongst staff of drug addiction.'] Thus it is not possible accurately to assess the opioid-sparing potential of an analgesic technique, and comparison between studies is difficult. PCAS overcomes such problems and provides a more ideal way of assessing the need for postoperative analgesia6 since patients titrate themselves to an acceptable level of comfort, unless side effects or inappropriate programming limit opioid uptake. PCAS has been used to investigate pain relief after techniques including epidural opioids12 and nonsteroidal antiinflammatory d r u g ~ ; it' ~provides a more rigorous test of analgesic regimens than intramuscular administration. Thus, there are no similar studies on wound infiltration after lower abdominal surgery using PCAS with which to compare our results. Comparisons with results after cholecystectomy are invalid, because this is an upper abdominal incision and because of differences in methodology. For example, infiltration of all cut surfaces after cholecystectomy with 40-50 ml of 0.5% bupivacaine, in addition to oesophagogastric decompression and immediate duodenal feeding, resulted in a significant reduction in postoperative opioid requirements! Again, following cholecystectomy, 50 ml of 0.25% bupivacaine reduced opioid requirement given on request by approximately one third over the first 24 hours; however, no assessment of quality of analgesia or side effects was made in this study.' Wound infiltration has been shown to provide equivalent postoperative analgesia to ilioinguinal nerve block in children after herni~tomy.'~Bilateral ilioinguinal nerve blockade" using 20 ml of 0.5% bupivacaine has been shown to reduce opioid requirements (intramuscular on request) and pain scores after lower segment Caesarean section. Bilateral ilioinguinal nerve block may be a more appropriate technique in this situation since wound infiltration with a similar dose of bupivacaine was ineffective in reducing opioid requirements. Acknowledgments We thank our anaesthetic, obstetric and midwifery colleagues at Leicester Royal Infirmary for their cooperation.

Forum References I . FELL D, DERRINGTON MC, TAYLORE, WANDLESS JG. Paediatric postoperative analgesia. A comparison between caudal block and wound infiltration of local anaesthetic. Anaesthesia 1988; 4 3 107-10. 2. OWENH, GALLOWAY DJ, MITCHELL KG. Analgesia by wound infiltration after surgical excision of benign breast lumps. Annals of the Royal College of Surgeons of England 1985; 67: 114-5. 3. PATELJM, LANZAFAME RJ, WILLIAMS JS, MULLENBV, HINSHAWJR. The effect of incisional infiltration of bupivacaine hydrochloride upon pulmonary functions, atelectasis and narcotic need following elective cholecystectomy. Surgery, Gynaecology and Obstetrics 1983; 157: 33840. 4. Moss G, REGAL ME, LICHTIG L. Reducing postoperative pain, narcotics, and length of hospitalization. Surgery 1986; 99: 206-10. 5. ALTMANDG. Statistics and ethics in medical research. 3 How large a sample? British Medical Journal 1980; 281: 13368. 6. TAMSEN A, HARTVIG B, DAHLSTROM B, LINDSTROM B, SON HOLMDAHL MH. Patient-controlled analgesic therapy in the early postoperative period. Acta Anaesthesiologica Scandinavica 1979; 2 3 462-70. 7. DAHLSTROM B, TAMSENB, PAALZOW L, HARTVIGP. Patient-controlled analgesic therapy, Part IV:

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pharmdcokinetics and analgesic plasma concentrations of morphine. Clinical Pharmacokinetics 1982; 7: 26679. 8. MOIRDD, THORBURN J. Obstetric anaesthesia and analgesia. London: Balliere Tindall, 1986. 9. EISENACH JC, GRICESC, DEWANDM. Patient-controlled analgesia following Cesarean section: a comparison with epidural and intramuscular narcotics. Anesthesiology 1988; 68: 444-8. 10. RAYBURN WF, GERANIS BJ, RAMADEI CA, WOODS RE, PATIL KD. Patient-controlled analgesia for post-Cesarean section pain. Obstetrics and Gynecology 1988: 72: 136-9. 11. SRIWATANAKUL K, WEIS OF, ALLOZAJL, KELVIEW, WEINTRAUB M, LASAGNA L. Analysis of narcotic analgesic usage in the treatment of postoperative pain. Journal of the American Medical Association 1983; 250 926-9. 12. MCQUAYHJ, BULLINGHAM RES, EVANS PJD, LLOYDJW, MOOREPA. Demand analgesia to assess pain relief from epidural opiates. Lancet 1980; 1: 768-9. 13. COLQUHOUN AD, FELLD. Failure of rectal diclofenac to augment opioid analgesia after cholecystectomy. Anaesthesia 1989; 44: 57-60. 14. REIDMF, HARRIS R, PHILLIPS PO, BARKERI, PEREIRA NH, BENNETTNR. Day-case herniotomy in children. A comparison of ilio-inguinal nerve and wound infiltration for postoperative analgesia. Anaesthesia 1987; 42: 658-61. 15. BUNTINGP, MCCONACHIE I. Ilioinguinal nerve blockade for analgesia after Caesarean section. British Journal qf Anaesthesia 1988; 61: 773-5.

Anaesthesia, 1991, Volume 46, pages 407-409

Midazolam4roperidol premedication for cardiac surgery A comparison with papaveretum and hyoscine

J. H. L. Antrobus, BSc, MB, BS, FCAnaes, P. Abbott, MB, ChB, FFARCS, C. M. E. Carr, MB, BS, FFARCS, Senior House Officers, R. R. Chatrath, MB, BS, FFARCS, Consultant, Department of Anaesthesia, Killingbeck Hospital, York Road, Leeds 14.

Summary A combination of midazolam and droperidol given intramuscularly was compared with papaveretum and hyoscine for premedication of patients about to undergo cardiac surgery. Midazolam and droperidol proved to be a very satisfactory combination, producing superior sedation and anxiolysis with good cardiovascular stability.

Key words

Premedication; papaveretum, hyoscine, midazolam, droperidol One of the principal functions of premedication is the relief of anxiety in the pre-operative period.’ Anxiety is detrimental to morale and causes a tachycardia and elevation of arterial blood pressure which is undesirable in cardiac patients.* The combination of papaveretum and hyoscine continues t o be used for premedication, although with the introduction of opioids in high dosage for induction of anaesthesia in cardiac surgery the analgesic effect of the premedication is not required, and the dry mouth caused by hyoscine is unpleasant for the patient. Despite their reputation for reliability, narcotic premedications still leave some patients relatively unsedated and a n x i o u ~whilst ,~ the

maximum dose is limited by the central respiratory depressant effects. Midazolam is a relatively new benzodiazepine which is anxiolytic, sedative, hypnotic, and causes anterograde a m n e ~ i a .Used ~ intramuscularly it is reported to have a reliable effect as a premedicant.s8 Droperidol is a substituted butyrophenone which produces a state of calm and indifference with little hypnotic effect.’ This study was undertaken to compare the combination of midazolam and droperidol with papaveretum and hyoscine given intramuscularly for the premedication of cardiac surgical patients.

Correspondence should be addressed to D r P. Abbott, Department of Anaesthesia, Royal Marsden Hospital, Fulham Road, London SW3 655. Accepted 12 September 1990.