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Anaesth Intens Care (1989),17,440-443 Post-Cholecystectomy Pulmonary Function Following Interpleural Bupivacaine and Intramuscular Pethidine D. C. OXORN * AND G. S. WHATLEyt Department of Anaesthesia and Surgical Intensive Care, The Halifax Infirmary and Dalhousie University, Halifax, Nova Scotia SUMMARY Twenty-four patients who were to undergo cholecystectomy were randomised into two groups, one to receive postoperative analgesia with interpleural bupivacaine, 20 ml of a 0.5% solution with adrenaline 5 pg/ml, and the other to receive intramuscular pethidine, 1 mg/kg. Preoperative and postoperative pulmonary function, postoperative pain scores, and days from operation to hospital discharge were recorded and statistically compared. There was no significant difference in pain scores, nor in days to discharge; however, postoperative pulmonary mechanics were significantly poorer in the interpleural group. A hypothesis to explain the differences is offered. Key Words: ANAESTHETIC, ANESTHETIC TECHNIQUES: interpleural catheter; ANAESTHETICS, ANESTHETICS, LOCAL: bupivacaine; ANALGESICS: pethidine; LUNG: pulmonary function; PAIN: postoperati v e The postoperative period is associated with important abnormalities in pulmonary function, which persist for up to two weeks when surgery involves the abdominal or thoracic cavities. A pattern of restrictive lung disease is seen, and while the aetiology is multifactorial, pain is thought to be a major contributor. I A desirable goal would be to control postoperative pain, minimise the perturbations in pulmonary function, and prevent complications such as atelectasis and pneumonia. The traditional use of parenteral opiates for pain control is not ideal; side-effects such as 'M. D .• C.M., F.R.C.P.C. tM.D., F.R.C.P.C. Address for Reprints: Dr. Donald Oxorn, Department of Anaesthesia, Halifax Infirmary, 1335 Queen Street, Halifax, Nova Scotia, Canada B3J. Accepted for publication July 5, 1989 nausea and respiratory depression limit their usefulness. Other modalities such as epidural blockade with local anaesthetics, 2 and narcotics, 3 transcutaneous electrical nerve stimulation, I and multiple intercostal nerve blockade4-6 have been tried with varying degrees of success. The instillation of local anaesthetics into the interpleural space to control pain after cholecystectomy was enthusiastically described by Reiestad and Stmmskag7 in 1986. They hypothesised that diffusion of local anaesthetic from the pleural space back into the subpleural space and then through the thin muscles to reach a large number of intercostal nerves was responsible for its effect. The present study was undertaken to compare the efficacy of interpleural bupivacaine and intramuscular pethidine in restoring pulmonary function after cholecystectomy. Anaesthesia and Intensil'e Care, Vat. /7, No. 4. November, /989 INTERPLEURAL BUPIVACAINE AND INTRAMUSCULAR PETHIDINE METHODS Twenty-four patients for cholecystectomy (without common bile duct exploration) through a subcostal incision were chosen for the study. Informed consent was obtained, as was approval from the hospital's ethics committee. The patients ranged in age from 21 to 74 years, and were ASA classification I or H. No individual gave a history of cardiac or respiratory disease. Patients were randomised to receive postoperative analgesia with either interpleural bupivacaine (study group), or intramuscular pethidine (control group). Pre- and postoperative pulmonary function was assessed using a Breon model 2400 Spirometer@ (Breon Winthrop Laboratories Inc. Aurora, Ontario) to measure forced vital capacity (FVC) and forced expiratory volume in the first second (FEV-I). All pulmonary function tests were done with the patients sitting upright in a vertical position with nose clips applied. Diazepam 5-10 mg was given orally approximately two hours before anaesthesia as a premedicant. Surgery was performed under general anaesthesia with thiopentone, fentanyl, vecuronium, nitrous oxide/oxygen, and enflurane. In study patients, muscle relaxation was reversed at the end of the procedure and spontaneous respiration established. While still anaesthetised, they were turned to the left lateral decubitus position. A 16-gauge Tuohy needle with a lubricated glass syringe attached was introduced through the skin overlying the right ninth rib in the posterior axillary line. With the bevel pointing caudad, the needle was walked off the rib in a cephalad direction until descent of the plunger confirmed entry into the intercostal space. The needle was advanced only during the inspiratory phase of the patient's respiration. An epidural catheter (Portex 18-gauge, closed end with three lateral eyes) was introduced 5-6 cm into the pleural space through the Tuohy needle. The patients were placed supine, and after a negative aspiration 20 ml ofbupivacaine 0.5% with adrenaline 5 Ilglml was injected through the catheter. Anaesthesia was then terminated. Postoperative maintenance consisted of intermittent interpleural Anaesthesia and InlensilJc Care. Va/. 17, No. 4. November. 1989 441 injections of 20 ml of bupivacaine 0.5% with adrenaline 5 Ilg/ml when pain was experienced. A postoperative chest radiograph was performed in the recovery room to check for the presence of a pneumothorax. In control patients, anaesthesia was terminated following the completion of surgery. Postoperative analgesia was provided with intramuscular injections of pethidine 1.0 mg/kg, as dictated by patient discomfort. Eighteen to twenty hours after the completion of surgery, study patients were administered a standard interpleural injection ofbupivacaine and the catheter was removed. Control patients received a standard intramuscular injection of pethidine. One hour later, repeat pulmonary function tests were performed in both groups. Postoperative pain was evaluated using a horizontal linear analogue score (0 = severe pain, 10= no pain).8 The observer was blinded to the method of analgesia when evaluating pulmonary function and postoperative pain. Unpaired t-tests were used to show that preoperative values for both randomised groups were comparable. The changes in postoperative FVC and FEV-I were measured by subtracting the value for each patient from his/her own preoperative value. Unpaired t-tests were used to compare the postoperative mean changes in the interpleural bupivacaine and intramuscular pethidine groups. Paired t-tests were used to compare postoperative to preoperative mean values for FVC and FEV-I within groups. P < 0.05 was taken to indicate significant differences. RESULTS The interpleural bupivacaine group included ten women and two men with an average age of 43.7 years and an average weight of 79.9 kg. The intramuscular group had nine women and three men with an average age of 47.6 years and an average weight of 75.6 kg. Patients in the interpleural group received an average of four injections in the first 24 hours, whereas patients in the intramuscular group received an average of five injections during the same time. There was no significant difference between linear analogue pain scores (Table 1), nor days from 442 D. C. OXORN AND G. S. WHATLEY TABLE TABLE 2 Days from operation to discharge. I Linear analogue pain score. Interpleural Intramuscular (X±SD) 7.8 ± 1.3 (X ± SD) 7.0 ± 1.3 NS Interpleural Intramuscular (X ± SD) (X±SD) 4.5 ± 1.4 4.1 ±0.6 NS X ± SD = mean ± SD; NS = nonsignificant difference between groups. X ± SD = mean ± SD; NS = nonsignificant difference between groups. operation to hospital discharge (Table 2) between the two groups. A small pneumothorax occurred in four of the interpleural patients, all of which were asymptomatic. No specific treatment was required, and all had cleared by the end of the day of surgery. There were no other significant pulmonary complications in either group. Examination of the pulmonary function studies (Table 3), reveals that the postoperative decreases in FVC and FEV-l were significantly greater in the interpleural group. mechanics were improved after the block was administered; however no statistical comparison was made with any other form of analgesia. Toledo-Pereyra and DeMeester5 compared post-thoracotomy pulmonary function in two groups of patients, one having received multiple intercostal nerve blocks performed at the time of surgery, and a control group receiving parenteral opioids. They found that the FVC and FEV-l were higher in the group receiving intercostal blocks. Ford et al. to demonstrated a shift from diaphragmatic to rib cage predominance in breathing patterns following upper abdominal surgery. Simonneau et al. 11 studied diaphragmatic function before and after upper abdominal surgery in five patients. Postoperative diaphragmatic function was severely decreased, and this decrement was not mitigated by injections of epidural fentanyl. The authors hypothesised that mechanical factors alone were responsible for the restrictive pulmonary defect following upper abdominal surgery. FEV-l and FVC, however, were not measured. Therefore, while analgesia may not reverse the diaphragmatic DISCUSSION The mechanism by which intra-abdominal surgery produces a restrictive pulmonary defect is incompletely understood, although pain is thought to be an important factor. That it is not the only factor is attested to be the numerous studies which have shown incomplete restoration of preoperative pulmonary function with various pain relieving techniques. Murphy9 and Engberg4 used intercostal blocks to treat postcholecystectomy pain. The quality of analgesia was excellent, and pulmonary TABLE 3 Pulmonary junction tests. Interpleural (X± SD) Intramuscular (X ±SD) Interpleural (~± SD) Intramuscular FVC(I) Preoperative Postoperative 3.8 ±0.7 2.1 ±0.7* 4.1±1.0 3.0 ± 0.9* 1.8 ± 0.6 1.1 ± 0.5 P<O.OI FEV-I(I) Preoperative Postoperative 3.2 ±0.8 1.7 ± 0.8* 3.2 ±0.9 2.3 ± 0.8* 1.5 ± 0.7 0.9 ± 0.4 P<O.OI (~±SD) NS NS X ± SD = mean ± SD; ~ ± SD = difference between preoperative and postoperative means± SD; NS = non significant between groups; P = significant differences between groups. * Significantly different from preoperative value within groups (P< 0.01). Anaesthesia and Intensive Care, Vol. 17, No. 4, November, 1989 INTERPLEURAL BUPIVACAINE AND INTRAMUSCULAR PETHIDINE dysfunction, it may still ameliorate the decrease in forced expiratory manoeuvres following upper abdominal surgery. In our study, FVC and FEV-l were lower in post-cholecystectomy patients receiving interpleural analgesia compared with those receiving intramuscular pethidine, despite seemingly adequate pain control in both groups. A possible explanation for this unexpected result suggested in a recent editorial,12 is block of the phrenic nerve as it courses through the thorax. Eisele l3 et at. used the cervical approach to block the phrenic nerve in healthy volunteers and this resulted in significant reductions in vital capacity. Unfortunately, we did not evaluate diaphragmatic excursion in our subjects. We chose the dose of interpleural bupivacaine based on the recent work of Stmmskag et al. 14 and the dosage of pethidine based on our clinical experience. The possibility exists that the use of different dosing regimens may have yielded disparate results. Our incidence of pneumothorax was higher than has been generally reported. We believe this to be secondary to a small amount of air entering the interpleural space through the Tuohy needle and to be of no consequence. In summary, we have shown interpleural bupivacaine to be an effective form of analgesia after cholecystectomy, although no better than parenteral pethidine in the doses used. It is speculated that the decrease in pulmonary mechanics seen with the former technique may in part be secondary to phrenic nerve blockade. ACKNOWLEDGEMENTS We wish to thank Drs. Wayne Gornall and Johnson Ngan for their help with the study, the Department of Respiratory Therapy for the performance of the pulmonary function tests, and Or. Emerson Moffitt for reviewing the manuscript. Anaesthesia and Intensive Care. Vol. /7, No. 4, November, /989 443 REFERENCES I. Craig DB. Postoperative recovery of pulmonary function, Anesth Analg 1981; 60:46-52. 2. Spence AA, Smith G. Postoperative analgesia and lung function: A comparison of morphine with extradural block. 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