Saudi Journal of Anaesthesia

ORIGINAL ARTICLE
Year
: 2010  |  Volume : 4  |  Issue : 3  |  Page : 137--141

Study of the effect of oral gabapentin used as preemptive analgesia to attenuate post-operative pain in patients undergoing abdominal surgery under general anesthesia


Harshel G Parikh, Sananta Kumar Dash, Chitra B Upasani 
 Department of Anesthesia & Critical Care, Grant Medical College & Sir J.J. Group of Hospitals, Mumbai-08, India

Correspondence Address:
Harshel G Parikh
27/5, Prafull Society, Gokhale Road, Dahanukarwadi, Kandiwali (West), Mumbai - 400 067
India

Abstract

Aims: To study the effect of oral gabapentin used as preemptive analgesia to attenuate post operative pain in patients undergoing abdominal surgery under general anesthesia. Materials and Methods: In a randomized double blind study, 60 patients were divided into two groups. Group A received 600mg gabapentin and group B oral received placebo 1 h prior to surgery. Anesthesia was induced with Propofol 2 mg/kg and Vecuronium 0.1mg/kg and maintained with 60% N 2 O in O 2 and Vecuronium 0.02 mg/kg. All cases were given Fentanyl 2μg/kg as pre-medication and a repeat dose 1μg/kg at the end of the first hour. Assessment of post-operative pain was made with the visual analog score (VAS) at extubation (0 h), 2, 4, 6, 12, and 24 h post-operatively. Post-operative analgesia was provided with intravenous Tramadol. The first dose was given in the Post Anesthesia Care Unit as 2mg/kg, and repeated at 8 and 16 h. Rescue analgesia was given with Diclofenac 1.5mg/kg, slow intravenous. The number of doses of rescue analgesia in both the groups was noted. Results: The VAS scores at 0, 2, 4, 6, 12, and 24 h were 1.9 vs. 2.4 (P=0.002), 2.3 vs. 3.0 (P=0.000), 3.2 vs. 3.7 (P=0.006), 2.9 vs. 4.4 (P=0.000), 3.6 vs. 4.6 (P=0.000), and 3.7 vs.4.6 (P=0.000), respectively. Numbers of patients requiring rescue analgesia with Diclofenac were 3 vs. 14 (P=0.004). Conclusion: A single oral dose of gabapentin given pre-operatively enhanced the analgesic effect of Tramadol as it also reduced the requirement of rescue analgesia with Diclofenac.



How to cite this article:
Parikh HG, Dash SK, Upasani CB. Study of the effect of oral gabapentin used as preemptive analgesia to attenuate post-operative pain in patients undergoing abdominal surgery under general anesthesia.Saudi J Anaesth 2010;4:137-141


How to cite this URL:
Parikh HG, Dash SK, Upasani CB. Study of the effect of oral gabapentin used as preemptive analgesia to attenuate post-operative pain in patients undergoing abdominal surgery under general anesthesia. Saudi J Anaesth [serial online] 2010 [cited 2022 May 18 ];4:137-141
Available from: https://www.saudija.org/text.asp?2010/4/3/137/71409


Full Text

 Introduction



Post-operative pain is not purely nociceptive in nature and may consist of inflammatory, neurogenic, and visceral components. Therefore, multimodal analgesic techniques utilizing a number of drugs acting on different analgesic mechanisms are becoming increasingly popular. [1] Post-operative pain affects recovery from surgery and anesthesia. The use of opioids by patient-controlled analgesia is popular, but limited by side-effects and by the fact that certain types of pain respond poorly to opioids. [2] Because of the multiplicity of the mechanisms involved in post-operative pain, a multimodal analgesia regimen with a combination of opioid and non-opioid analgesic drugs is often used to enhance analgesic efficacy and reduce opioid requirements and side-effects. [3]

Gabapentin , a structural analog of gamma aminobutyric acid, is used as an anticonvulsant drug since 1993. In addition, it has been effective in neuropathic pain, [4] diabetic neuropathy, [5] post-herpatic neuralgia, [6] and reflex sympathetic dystrophy. [7] Pre-treatment with gabapentin can block the development of hyperalgesia. [8] Studies have demonstrated that mechanical hyperalgesia surrounding the wound in post-operative patients and experimentally, heat-induced, secondary hyperalgesia share a common mechanism and that central neuronal sensitization contributes to post-operative pain. [9] Gabapentin has a selective effect on the nociceptive process involving central sensitization. [8] Gabapentin and morphine have synergistic analgesic effects in animals and in humans. [10],[11],[12] The aim of this study is to know the effect of oral gabapentin given pre-operatively on post-operative pain in patients undergoing abdominal surgeries lasting for around 2 h.

Aims

To study the effect of oral gabapentin 600 mg given 1 h prior to surgery as preemptive analgesia to attenuate post-operative pain in patients undergoing abdominal surgery under GA.

 Materials And Methods



After obtaining the approval of the Institutional Ethics Committee (Grant Medical College and Sir J J Groups of Hospitals) and written informed consent from the patients, 60 patients were included.

Inclusion criteria



Patients belonging to American Society of Anesthesiologists physical status I and IIPatients undergoing elective surgery under general anesthesiaAnticipated duration of surgery less than 4 hAge group between 18 and 65 yearsWeight range up to 20% of the ideal body weight for either sexHemodynamic ally stable

Exclusion criteria



Patients with a history of hypertension, diabetes, and liver diseasePatients with acute or chronic renal diseasePatients with known neurological diseaseNeurosurgical and cardiovascular surgical casesPregnant patientsPatients with known psychiatric disordersPatients with anticipated difficult airwayPatients on antihypertensive drugs, sedatives, hypnotics, antidepressants, and drugs with effects on the nervous systemPatients already taking oral gabapentinPatients allergic to opioids and Tramadol

Patients were randomly divided into two groups, with 30 patients in each group. They were randomly allocated according to computer-generated randomization. Patients in the control group received oral placebo capsules and those in the gabapentin group received 600 mg gabapentin (Neurontin 300 mg capsule; Pfizer, Mumbai, India) 1 h before surgery. The study drugs were prepared by the pharmacy and an appropriate code number was assigned.

In the operating room, a crystalloid infusion was started through an IV cannula. Blood pressure (MAP), heart rate (HR), and peripheral oxygen saturation (SpO 2 ) were monitored. For pre-medication, midazolam 0.07 mg/kg, glycopyrolate 0.004 mg/kg, and fentanyl 2μg/kg were administered intravenously on the table. After adequate pre-oxygenation for 3 min, anesthesia was induced with propofol 2 mg/kg and vecuronium 0.1 mg/kg and maintained with 60% N 2 O in O 2 on Bain's circuit and vecuronium 0.02 mg/kg. At the end of surgery, neuromuscular block was antagonized with neostigmine 0.05 mg/kg and glycopyrolate 0.008 mg/kg. Surgeries lasting for more than 1 h were given a repeat dose of fentanyl 1΅g/kg at the end of the first hour of induction. Any increase in the HR and MAP when not settling down by deepening the plain of anesthesia was given fentanyl 0.05 ΅g/kg subsequently. Total duration of the surgery in both the groups and the intra-operative fentanyl in both the groups were studied.

After tracheal extubation, patients were observed in the PACU for 1 h and then transferred to the surgical ward. Assessment of post-operative pain was made on the basis of the visual analog score (VAS), where 0 cm - "no pain" and 10 cm - "worst pain imaginable." The VAS scores are taken immediately on extubation (0 h) and at 2, 4 6, 12, and 24 hours post-operatively.

Post-operative analgesia was provided with Tramadol intravenously. The first dose was given in the PACU as 2 mg/kg and repeated at 8 and 16 h. If the patient still complained of pain, then rescue analgesia was given with diclofenac 75 mg slow intravenous over 10 min. The number of doses of rescue analgesia in both the groups were studied and compared. The occurrence of any side-effects, such as nausea and vomiting, respiratory depression, dizziness, somnolence, headache, and pruritus was recorded. Tramadol dose was omitted if the patient had a respiratory rate <12 breaths/min, an SpO 2 measured by pulse oximetry <95%, or a serious adverse event related to opioid administration.

 Results



As seen in [Table 1], [Table 2], [Table 2]a and [Table 3], patients in both the groups are comparable in terms of demographic parameters like age, sex ratio, and weight. {Table 1}{Table 2}{Table 3}

As seen from [Table 4] and [Table 5], there is no significant difference between the groups in terms of total duration of surgery and intraoperative fentanyl usage.{Table 4}{Table 5}

As seen from [Table 6] and [Table 7] and [Figure 1], the VAS scores are significantly lower in the gabapentin 600 mg group as compared to placebo at 0, 2, 4, 6, 12, and 24 h of surgery.{Table 6}{Table 7}{Figure 1}

As seen from [Table 8], [Table 8]a and [Figure 2], three patients in the gabapentin group required rescue analgesia in terms of diclofenac intravenously as compared to 13 patients in the placebo group. The three patients in the gabapentin group requiring rescue analgesia were at around 4, 7, and 12 h after surgery, respectively. Of the 13 patients requiring rescue analgesia, only one patient required it twice, at 4 and 16 h post-surgery, respectively. But, as seen, the rescue analgesia requirement in the gabapentin group was significantly lower as compared to the placebo group.{Table 8}{Figure 2}

 Discussion



The results of our pre-operative oral single-dose study investigating the acute post-operative analgesic effects of gabapentin in patients undergoing abdominal surgeries requiring general anesthesia show that gabapentin decreased post-operative pain scores at 0, 2, 4, 6, 12, and 24 h of surgery and decreased requirement of rescue analgesia when compared with placebo.

Post-operative pain is not purely nociceptive in nature and may consist of inflammatory, neurogenic, and visceral components. Therefore, multimodal analgesic techniques utilizing a number of drugs acting on different analgesic mechanisms are becoming increasingly popular. [1] The main aim in combining different analgesic drugs is to obtain synergistic or additive analgesia, allowing a smaller dose of each drug with an improved safety profile. This can be achieved by combining analgesics acting at different locations (e.g., centrally and peripherally acting analgesics). We used Tramadol as a fixed-dose regimen for post-operative pain control and Diclofenac as rescue analgesia to be given only when the patient demanded for it. Tramadol is widely used for moderate-to-severe post-operative pain. Its efficacy is a result of two complementary mechanisms of action: stimulation of μ-opioid receptors and inhibition of norepinephrine and 5-hydroxytryptamine reuptake in pain pathways.[13]

Non-steroidal anti-inflammatory drugs are commonly used analgesics for minor surgery and are useful adjunctive analgesics in patients undergoing major surgery, decreasing pain and opioid requirements. They are well established, effective, and inexpensive. However, their use may be limited by adverse renal, gastrointestinal, and hemostatic effects.

Antihyperalgesic drugs such as gabapentin may have a role in post-operative pain, and the combination with other antinociceptive drugs may produce synergistic analgesia effects. [9],[10]

Significantly low VAS scores immediately after extubation, i.e. 0 h (1.9 vs. 2.4, P=0.002) in the gabapentin group may suggest the synergistic effect of gabapentin with fentanyl. Decreased rescue analgesic requirement in the gabapentin group also suggests the synergistic effect of gabapentin with Tramadol.

Turan et al, in 2004, also found that 1,200 mg gabapentin given 1 h prior to surgery significantly reduced the post-operative pain scores and Tramadol requirements in Total abdominal hysterectomy patients.

In animal models of nociception, gabapentin reduces the hypersensitivity associated with nerve injury, inflammation, and pain after surgery. [8],[9] Mechanical hyperalgesia surrounding the wound in post-operative patients and experimental, heat-induced secondary hyperalgesia share a common mechanism -central neuronal sensitization, which may contribute to some aspects of post-operative pain. Antihyperalgesic drugs such as gabapentin may have a role in post-operative pain, and the combination with other antinociceptive drugs may produce synergistic analgesia effects. [9],[10] Gabapentin enhanced the analgesic effect of morphine in healthy volunteers, [11] and the combination produced better analgesia in comparison with morphine alone in patients suffering neuropathic cancer pain. [12]

Gabapentin significantly decreased morphine consumption and pain in patients after mastectomy [13] although the patients were evaluated for only 4 h after surgery.

Gabapentin is well tolerated. It has few side-effects and minor interactions with other drugs when used for the treatment of chronic pain. [7] We did not observe any significant side-effects associated with a single oral dose of gabapentin. Our results are similar to other published reports. [14],[15],[16],[17]

 Conclusion



Preemptive use of gabapentin significantly decreases the post-operative pain and rescue analgesic requirement in patients undergoing abdominal surgery under general anesthesia.

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