Local anesthetic infiltration is not effective in decreasing post- Cesarean section skin pain severity. Iman Fayez Anees

Transcription

1 Rawal Medical Journal An official publication of Pakistan Medical Association Rawalpindi Islamabad branch Established 1975 Volume 36 Number 2 March- June 2011 Original Article Local anesthetic infiltration is not effective in decreasing post- Cesarean section skin pain severity Iman Fayez Anees Department of Gynecology and Obstetrics, King Hussein Medical Center, Amman, Jordan. ABSTRACT Objective To evaluate the impact of skin local infiltration using Bupivacaine on post-cesarean section somatic pain intensity. Subjects and Methods Our prospective and double-blind study included 81 female patients, aged years, American society of anesthesiologists (ASA) physical status I-II and scheduled for cesarean section under balanced general anesthesia at Queen Alia military hospital during the period Subjects were divided randomly into two groups. Group I (n=43) received skin local infiltration with placebo solution and group II (n=38) received skin local infiltration using Bupivacaine 0.5%. Intramuscular pethidine was administered intra- and post-operatively. Post-operative somatic pain scores using visual analog scale at rest (VASR) and pethidine consumption were recorded during the first 24 hours. Results There were no significant difference in VASR for pain at 1 hour post-operatively, (G I, 2.4 and G II, 2.6, P>0.05) and pethidine consumption (G I, 25mg and GII, 25mg, P>0.05). Conclusion Local skin infiltration using Bupivacaine 0.5% was not successful in controlling postcesarean section somatic pain. (Rawal Med J 2011;36: ). Key words Bupivacaine, cesarean section, post operative pain.

2 INTRODUCTION Postoperative pain management using local skin anesthetic infiltration is cheap, simple and safe. This technique has been used effectively for postoperative pain control in, some but not all, types of operations such as inguinal hernia repair 1 where the dominant component of pain is somatic, decreasing postoperative analgesic consumption. Efficient postoperative pain relief should decrease the somatic pain. There is a greater appreciation of the need to improve postoperative pain control using techniques that not only reduce pain but have the ability to abolish it and potentially improve outcome. 2 Local anesthetics are usually injected in an acid solution as the Hcl salt (PH 5). After injection, the PH increases as result of buffering in the tissues and free base is able to pass through the lipid cell membrane to the interior of the axon, where re-ionized portion enters and blocks the sodium channels and prevents influx of sodium ions. As a result, no action potential is generated or transmitted and conduction blockade occurs. 3 The aim of our study was to assess the effect of skin infiltration with Bupivacaine 0.5% on post-cesarean section somatic pain intensity. SUBJECTS AND METHODS This prospective and double-blind study enrolled 81 female subjects, ASA class I-II, aged years and assigned for elective cesarean section after obtaining written informed consent. Any patient with history of chronic pain was excluded. Induction of general anesthesia was achieved using scoline 1 mg/kg, sodium thiopentone 6 mg/kg and atracurium 0.5 mg/kg. A mixture of O2: 30% and N2O: 70% with halothane (0-1%) were delivered according to depth of anesthesia and blood pressure recordings. Anesthesia was maintained with intermittent intravenous atracurium 0.1 mg/kg and varying concentration of halothane (0-1%). Fentanyl 2 mcg/kg was given after baby was delivered. Subjects were randomly divided into two groups using sealed envelopes. Group I (n=43) received pre-incision skin infiltration with 30 ml of placebo solution and group II (n=38) received pre-incision skin infiltration with 15 ml Bupivacaine mixed with 15 ml of saline 0.9%.The solution of either placebo or Bupivacaine was prepared by an anesthesia technician, unaware of the study. The patient, physicians and ward nursing team were not aware of the study also. Subcutaneous skin infiltration was performed until a swelling is achieved over the entire scheduled incision which was done within 5 minutes after the infiltration. All subjects received 50 mg pethidine intramuscularly and intraoperatively 10 minutes before the end of surgery. Postoperatively, subjects were monitored for one hour in the post anesthesia unit, then at 2 and 4 hours intervals in the ward. The time when subjects arrived at the post anesthesia care unit was recorded as zero. Analgesic effect was monitored using VASR to record somatic pain scores intensity where 0=no pain and 10=worst pain. 4 In the post anesthesia unit, if analgesia was not achieved, intramuscular pethidine 50 mg was administered until pain score was equal to 3 or less on VASR and then every 4 hours in the ward. Pethidine was discontinued 24 h postoperatively, after which sodium diclofenac intramuscular 75 mg was given every 8 h for the next 24 h. All measurements were recorded every 2h during the first 8h and then every 4h during the next 16h postoperatively. Proportion of patients with somatic pain was followed up for the next 48 h postoperatively. Somatic pain was taken as sharp, mild, well defined and felt at the abdominal wall. 5 The duration of surgery, volume of infiltrated solution, length of the skin incision, 24h pethidine consumption and pain scores were noted. The pethidine

3 consumption and the somatic pain scores on VASR basis were compared using the student s t test. A P value <0.05 was taken as significant. RESULTS Ninety subjects were enrolled in the study but nine were excluded, who were ASA III. There were no significant differences regarding patient demographics, kind and length of skin incision, volume of infiltrated solution and time of surgery (Table 1). Table 1. Patient demographics. G I (n=43) G II(n=38) ASA I II Age (years) Weight (kg) Length of incision (cm) Surgery duration (min) Vol. sol. infiltrated (ml) The groups had no significant differences in VASR for somatic pain at various time intervals (Table 2). Table 2. Mean VASR. Time (h) G II G I In all patients, the proportion of postoperative somatic pain was significantly more at 2 days than that at12 hours. (P<0.05) (Table 3). Table 3. Percentage of patients with somatic pain (no.) Time (h) G II G I (4) (5) (6) (8) (8) (9) (11) (13) (10) (13)

4 In both groups, the severity and percentage of patients with postoperative somatic pain gradually increased with time. No pain was noticed in 71.05% and 73.68% in group II and 69.77% and 69.77% in group I at 24 and 48 h postoperatively, respectively. Table 4. Mean pethidine and sodium diclofenac consumption (mg). Time (h) G I G II Pethidine Sodium diclofenac All subjects could distinguish between somatic and visceral pain. There was a difference of 5 mg in pethidine consumption over 24 h (Table 4). There was no significant differences in terms of pethidine consumption between the two groups at all time intervals (P>0.05). DISCUSSION The goal of effective postoperative pain relief is to decrease the somatic and visceral components of pain. There are studies which had conflicting results regarding the impact of subcutaneous local anesthetic infiltration on postoperative somatic pain. Sinclair et al showed good postoperative analgesia quality 6,7 but Cobby et al demonstrated no such good quality 8-10 and recommended that all layers of the abdominal incision must be infiltrated to attain good results. 8 Klein infiltrated separately the deep and superficial layers of the Pfannenstiel incision. 10 In all these studies, the length of incision was not taken in consideration. All had small sample size as ours, variable investigation protocol and variable local anesthetic methods. As the kind of skin incision is an important variable on postoperative somatic pain, we chose only one type of incision to avoid bias. Postoperative pain has somatic and visceral components. Somatic component originates from lower thoracic and upper lumbar somatic nerves of the skin, fascia, muscle and other subcutaneous soft tissue. 5 With time, the less severe masked somatic pain becomes more evident. The slow improvement in somatic pain after 3 days is due to slower healing of skin and subcutaneous tissue. Postoperative subjective pain rating demonstrated that all subjects were free of pain after 96 hours. 9 Any method that is not successful in managing postoperative somatic pain is likely of low efficiency. Pain originating from viscera is more important than somatic pain. 11 Postoperative pain had various causes, including back pain, urinary catheter and sore throat but mainly from the abdomen. Theoretically, local anesthetic infiltration may be potent in controlling the somatic pain only. 12 Preincision infiltration presumably can allow agent to diffuse into deeper

5 layers of tissues. As the duration of action of Bupivacaine can last up to 12 hours, it is unlikely that the local anesthetic effect had disappeared at the end of operation. Pethidine consumption in control is 100 mg at 4h postoperatively. 8 CONCLUSION Preincision subcutaneous local anesthetic infiltration is not effective in decreasing somatic pain post cesarean section. Correspondence: Iman.fayez@yahoo.com. Received: December 29, 2010 Accepted: February 7, 2011 REFERENCES 1. Behnia R, Hashemi F, Stryker SJ, Ugiki GT, Poticha SM.Acomparison of general versus local anesthesia during inguinal herniorrhaphy.surg Gynecol Obstet. 1992;174: Allman KG, Wilson IH. Editors. Regional anesthesia. In: Oxford handbook of anesthesia. 1st ed-oxford University Press, p Wildsmith JAW. Local anesthetic agents. In: Aitkenhead AR, Smith G, Rowbotham DJ. Textbook of anesthesia. 4th ed. Oxford:Oxford University Press, 2001,p Berthier F, Potel G, Leconte P, Tonge MD, Baren D. Comparative study of methods of measuring acute pain intensity in an ED. Am J Em Med 1998;16: Cousins M. Acute and postoperative pain. In:Wall PD, Melzack R. editors. Textbook of pain. 3rd ed. Edinburgh: Churchill livingstone, P Sinclair R, Westlander G, Cassuto J, Hadner T. Postoperative pain relief by topical lidocaine in the surgical wound of hysterctomized patients. Acta Anesthesiol Scand 1996;40: Hannibal K, Galatius K, Hansen A, Obel E, Eglersen E. Preoperative wound infiltration with bupivacaine reduces early and late opioid requirement after hysterectomy. Anesth Analg 1996;83: Cobby TF, Reid MF. Wound infiltration with local anesthetic after abdominal hysterectomy. Br J Anesth 1997;78: Victory RA, Gajraj NM, Van Elstraete A, Pace NA, Johnsen ER, White PF. Effect of preincision versus postincision infiltration with bupivacaine on postoperative pain. J Clin Anesth 1995;7: Klein JR, Heaton JP, Thompson JP, Cotton BR, Davidson AC, Smith G. Infiltration of the abdominal wall with local anesthetic after total abdominal hysterectomy has no opioid sparing effect. Br J Anesth 2000;84:248-9.

6 11. Moiniche S, Mikkelsen S, Wetterslev J, Dahl JB. Aqualitative systematic review of incisional local anesthesia for postoperative pain relief after abdominal operations. Br J Anesth 1998;81: Leung CC, Chan YM, Ngai SW, Ng KF, Tsui SL. Effect of preincision skin infiltration on post-hysterectomy pain.a double blind randomized controlled trial. Anesth Intensive Care 2000;28:510-6.