Wound infiltration with plain bupivacaine as compared with bupivacaine fentanyl mixture for postoperative pain relief after abdominal surgery.

AIM: To compare the efficacy of wound infiltration with Bupivacaine or Bupivacaine with fentanyl for post operative analgesia.
BACKGROUND: The role of Bupivacaine and fentanyl mixture as wound infiltration for post operative analgesia is less explored in human subjects.
MATERIALS AND METHODS: This prospective, randomized included 60 ASA grade I, II, and III patients in the age group of 20-75 years of age. The patients were randomized into two groups of 30 patients each: Group A received wound infiltration with a solution containing 0.5% bupivacaine (2 mg/kg), while, Group B received infiltration with a solution containing fentanyl 25 μg added to 0.5% bupivacaine (2 mg/kg).
RESULTS: None of the patients in both groups had unbearable incisional pain but addition of fentanyl to 0.5% bupivacaine reduced analgesic consumption in the postoperative period (P<0.05).
CONCLUSION: Addition of opioids to local anesthetics results in better postoperative analgesia and reduced opioid requirement post operatively.

RCT Entities:   Population Interventions Outcomes

INTRODUCTION

Postoperative pain remains prevalent and is the greatest concern for a patient. Effective pain relief is not only human but also has a positive impact on recovery as postoperative pain is associated with increased morbidity and mortality. Pain after abdominal surgeries leads to restricted breathing effort and inability to adequately cough out secretion[1] which leads to a decrease in functional residual capacity, early airway closure, segmental or lobar collapse, retention of secretions leading to bronchopneumonia.[2]

Wound infiltration provides good postoperative analgesia, facilitating a rapid and smooth recovery. Local anesthetics are potent long lasting and act through several mechanisms including inhibition of the effects of prostaglandins, inhibition of the migration of leucocytes, and reduction of vascular permeability. It has proven effective in various surgical procedures especially in herniorrhaphies,[3] gynecological surgeries,[4] thoracotomies, etc.

It was found that combination of local anesthetic with opioid for wound infiltration in a patient undergoing cholecystectomy was associated with better postoperative analgesia, reduced analgesic consumption, and better lung function.[5]

MATERIALS AND METHODS

After obtaining approval from the institutional ethical committee and informed written consent from the patients, 60 patients, aged 20-75 years ASA I-III undergoing abdominal surgical procedures, were randomly allocated into two equal groups.

Patients with severe cardiovascular or liver disease, those who received opioids as premedication, and those with known allergic response to local anesthetics were excluded from the study.

The study was conducted as a randomized double-blind study using two solutions:

Solution containing 0.5% bupivacaine (2 mg/kg).

Solution containing added fentanyl 25μg to 0.5% bupivacaine (2 mg/kg).

Coding of the solutions was done by a senior anesthetist and the person administering the drug was unaware of its constituents.

All patients received Tab Diazepam 10 mg 1h prior to induction as preanesthetic medication. After precurarization with 1 mg of vecuronium to prevent fasciculations, the patients were induced with thiopentone (4 mg/kg) and tracheal intubation was done with succinyl choline (1-2 mg/kg). Anesthesia was maintained using O2, N2O, and halothane (0.5%) or isoflurane (1-2%). Intermittent vecuronuim (0.1 mg/kg) was given when required. No opioids were used during the surgery. Prior to skin suturing wound was infiltrated using one of the solutions. At the end of the surgery muscle relaxation was reversed using neostigmine (0.05 mg/kg) and glycopyrrolate (0.01 mg/kg).

The assessment of pain was done in each patient at 0, 1, 2, 4, 6, 8, 12, and 24 h after surgery and three types of pain were analyzed:

Constant incisional pain.

Movement-associated pain.

Pain upon pressure on the surgical wound.

Rescue analgesia

The patient was given Inj. Tramadol 50 mg iv on complaint of pain. The time of first request of analgesia was recorded. The total narcotic requirement in mg in the first 24 h was calculated and used for statistical purpose.

RESULTS

We compared the analgesic effects of Bupivacaine and Bupivacaine Fentanyl admixture when used for wound infiltration in post operative patients. The patients in both groups were comparable in terms of age, sex, weight and duration of surgery [Table 1]. The hemodynamic parameters i.e. heart rate, systolic and diastolic blood pressure and respiratory rate were compared in patients of both groups at regular intervals [Figures 1, 2, 3, 4]. Group B was found to have significant tachycardia,higher systolic and diastolic blood pressure compared to patients in Group A. There was no stastical difference in both groups in terms of respiratory rates [Figure 2]. Our study had statistically significant difference in terms of constant incisional pain when comparing both groups with more patients in Group A complaining of moderate pain [Figure 5].

Table 1

Patient characteristics

Figure 1

Comparison of heart rate in patients of both groups

Figure 2

Comparison of respiratory rate in patients of both groups

Figure 3

Comparison of systolic blood pressure in patients of both groups

Figure 4

Comparison of diastolic blood pressure in patients of both groups

Figure 5

Comparison of constant incision pain post op in patients of both groups

While comparing pain upon movement we found statistically significant difference from 1 hour post-op to 6 hours post-op with patients in Group A having more pain compared to Group B [Figure 6]. The difference between both groups in terms of pain upon pressure on the wound was statistically significant with patients in the plain bupivacaine group having more pain compared to the buivacaine fentanyl group at all times except at 24h [Figure 7]. There was also a difference in the number of patients in both groups who required analgesia as early as 2h postoperatively. The difference was as marked as 40% in Group A compared to 3% in Group B [Figure 8]. At 24h the opioid requirement (number of dose) was found to be less in Group B (mean 105 ± 24.03) compared to Group B (mean 218 ± 62.26) [Figure 9].

Figure 6

Comparison of movement associated pain post-op in patients of both groups

Figure 7

Comparison of pain upon pressure post-op in patients of both groups

Figure 8

Comparison of time for first request for analgesia in patients of both groups

Figure 9

Comparison of total no of doses of rescue analgesia in initial 24 hours post operatively in patients of both groups

DISCUSSION

Several studies have been done for finding efficacious drugs to combat pain. Narcotics have been the main stay of postoperative pain management and morphine as the standard drug despite its various side effects. NSAIDS are also associated with gastric ulceration and bleeding complications and a concern in renal dysfunction. TENS, ALTENS, conventional acupuncture[6] relaxation technique, and cryoanalgesics have also shown inconsistent results.[7] However, there has been renewed interest in local anesthetic wound instillation for postoperative pain control. Eriksson studied the in vivo effects of lidocaine on leucocyte function in the surgical wound. He found significantly lower leucocyte counts in the wounds treated with lidocaine.[8]

Various studies have been done to assess the pain and comparing effect of plain anesthetic as compared to anesthetic opioid mixture for wound infiltration.[9] By using plain lignocaine and lignocaine fentanyl mixture in wound infiltration, three types of pain were assessed spontaneous pain, movement-associated pain, and pain upon pressure—and they found that they were significantly higher in the plain lignocaine group compared to the lignocaine fentanyl at all times of observation. We did a similar study; our patients in both groups were comparable in terms of age, sex, weight, and duration of surgery. Our study had comparable results as we also had a statistically significant difference in terms of constant incisional pain when comparing both groups. Also pain upon movement was statistically significant at 4 h in the bupivacaine fentanyl group. The difference between both groups in terms of pain upon pressure on the wound was statistically significant with patients in the plain bupivacaine group having more pain compared to the buivacaine fentanyl group at all times except at 24 h.

There was also a difference in the number of patients in both groups who required analgesia as early as 2 h postoperatively. The difference was as marked as 40% in Group A compared to 3% in Group B and this correlated well with the studies done before by Likar et al.[10] and Tverosky et al.[11] who also showed a better analgesic effect with added opioids to local analgesics.

At 24 h the opioid requirement (number of dose) was found to be less in Group B (mean 105 ± 24.03) compared to Group A (mean 218 ± 62.26) which was similar to studies done by Kumar et al. and Tverosky et al.

Opioids over the years were thought to have a central action only but recent researches have shown that opioid agonists have peripheral action as well.[1213] The peripheral opiate antinociception is mediated through λ as well as κ receptors located on primary afferent veins.[14]

Fentanyl with its less histamine releasing property may be a better drug than morphine or meperidine for peripheral analgesia. Being an opioid of the phenol peperidine group it could have a local anesthetic effect on the nerves. But the dose required for this effect would be much larger and a dose of 25 μg used by us cannot account for this effect. The primary clinical effect of fentanyl may be related to the central opiate receptors and thus can occur at a very small dose.

The mean duration of analgesia was higher in the fentanyl bupivacaine group compared to the bupivacaine group. Further the mean rescue analgesic doses were significantly less in Group B as compared to Group A. This supports the peripheral analgesic effect of opioids. The presence of inflammation has been found to enhance the efficacy of peripherally applied opioids.[15] This is because inflammation disrupts the perineuriun as well as increases the number of peripheral sensory nerve terminals. The favorable results in our study may be because of infiltration being performed after completion of surgery when inflammatory response may have begun. The negative results by some authors may be related to the infiltration of opioid prior to surgery when inflammation has not yet started.

In conclusion, combination of bupivacaine and fentanyl for wound infiltration in abdominal surgeries was associated with better postoperative analgesia and reduced analgesic consumption.