Editorial II: Gabapentin: a new drug for postoperative pain?

Preoperative Gabapentin for Pain Control: A Randomized, Placebo-controlled Clinical Trial in Patients Undergoing Inguinal Hernioplasty

PURPOSE

The perioperative use of gabapentin has been suggested to reduce postoperative pain and opioid consumption. However, there is a variation in clinical practice, the type of surgery and the administration time seem to be distinct between the available studies. We assess whether gabapentin administered before surgery reduces postoperative pain in patients who have undergone inguinal hernioplasty.

DESIGN

This is a double-blind, randomized, and placebo-controlled trial.

METHODS

Seventy-seven patients scheduled for inguinal hernioplasty were randomized in two groups to receive gabapentin (900 mg) or placebo in the perioperative period. The primary outcome was analgesia measured by visual analog scale up to 30 days after surgery. The secondary outcomes such as morphine consumption, nausea, headache, and sedation have been also described.

FINDINGS

Patients who received gabapentin had lower postoperative pain scores compared to the control group, P < .001. The postoperative morphine use was significantly lower in the gabapentin (5.3%) versus placebo group (74.4%), P < .001. No significant difference between groups was observed for the occurrence of adverse events.

CONCLUSIONS

The perioperative administration of gabapentin was effective in reducing postoperative pain and had an important effect in decreasing morphine use. Together, our data reveal a long-lasting opioid-sparing effect of gabapentin in patients who underwent inguinal hernioplasty.

Premedication with pregabalin 150mg versus 300mg for postoperative pain relief after laparoscopic cholecystectomy

Background and Aims

Pregabalin has been used in various studies for postoperative pain relief in varying doses. However, there is no conclusive evidence to support a safe and effective dose of pregabalin. The present study was designed to compare the efficacy of two different preoperative doses of pregabalin (150 mg and 300mg) in patients undergoing laparoscopic cholecystectomy for postoperative pain relief.

Material and Methods

Ninety adult patients of either sex with American Society of Anesthesiologist physical status I and II scheduled for elective laparoscopic cholecystectomy under general anesthesia were randomized to receive pregabalin 150mg (group A), pregabalin 300mg (group B), or placebo (group C) orally 1 h before surgery. The pain was assessed using a visual analog scale (VAS) and a verbal rating scale (VRS) for the initial 24 h postoperatively. The primary outcome of our study was the comparative assessment of the severity of pain in the postoperative period in three groups. Postoperative analgesic consumption and incidence of side effects were assessed as secondary outcome measures.

Results

VAS score was significantly more in group C than group A and B (P-value <0.05). The total amount of fentanyl required in 24 h was least in group B (228.33 ± 42.41μg) followed by group A (292.50 ± 46.49μg) and group C (322.50 ± 39.58μg) (P-value 0.0001). The incidence of sedation, dizziness, and visual disturbances was more in group B as compared to group A and was least in group C.

Conclusions

Pregabalin 150 mg is effective in decreasing postoperative pain after laparoscopic cholecystectomy with fewer incidences of adverse effects such as sedation and visual disturbances as compared to pregabalin 300 mg.

The effect of a single 75 mg preoperative dose of pregabalin on postoperative pain in rhinoplasty: A double-blinded, placebo-controlled randomized clinical trial

The goal of this study was to evaluate the effect of a single preoperative dose of 75 mg of pregabalin on postoperative pain in rhinoplasty. Volunteers with a physical status of ASA I were included in our study after informed written consent. This was a randomized, double-blinded, placebo-controlled clinical trial. All pregabalin and placebo capsules were given to patients orally 1 h prior to surgery. A standard open rhinoplasty procedure was performed on all patients. All patients underwent the same general anesthesia and postoperative analgesic protocol, with the only difference between the two studied groups being the use of a single dose of pregabalin prior to surgery. Finally, pain intensity was measured at 2, 4, 6, 12, and 24 h after surgery, using a horizontal visual analogue scale (VAS), and was analyzed statistically. 128 volunteers - 33 men (25.8%) and 95 women (74.2%) - with a mean age of 26.23 ± 7.16 were included in this study. Pain intensity scores were consistently lower in patients who received pregabalin preoperatively (p = 0.002); however, the incidence of nausea, drowsiness, difficulty in concentrating, dry mouth, and constipation showed no differences between the two study groups (p > 0.05). In conclusion, the administration of pregabalin should be added to the perioperative protocol whenever appropriate.

Effectiveness of pregabalin as a secondary treatment for neuropathic pain from postherpetic neuralgia

Herpes zoster or shingles causes a severe painful rash that spreads along dermatomes in the face or chest wall, which leads to a condition known as postherpetic neuralgia (PHN). There is no cure for PHN, but there are many treatments to reduce pain duration and severity. In this case report, we describe a patient treated for PHN using pregabalin (Lyrica) after failure with gabapentin. Despite being listed as a controlled substance by the Food and Drug Administration, pregabalin may be an effective first-line therapy for PHN and other forms of neuropathic and chronic pain.

Optimizing the dose of local infiltration analgesia and gabapentin for total knee arthroplasty, a randomized single blind trial in 128 patients

BACKGROUND AND PURPOSE

Effective analgesia is essential for postoperative recovery and rehabilitation in TKA. The challenge of analgesic regimes is to obtain adequate pain relief and maximum muscle control to mobilize and rehabilitate patients early. However, the optimal dose and best composition are not known. We hypothesized that there would be no differences in reported postoperative pain on the day of the TKA surgery as well as the first day after surgery when different combinations of ropivacain for LIA and gabapentin are given.

METHODS

This prospective randomized trial examined 128 TKA patients treated with LIA and gabapentin in four groups. Group A: 300-mg ropivacain/600-300-300-mg gabapentin. Group B: 150-mg ropivacain/600-300-300-mg gabapentin. Group C: 300-mg ropivacain/300-100-100-mg gabapentin. Group D: 150-mg ropivacain/300-100-100-mg gabapentin. Primary endpoint was pain (NRS) at multiple moments. Secondary endpoints were number of adverse effects, length of hospital stay (LOS), the amount of consumption of pain medication, and wound leakage. Generalized estimating equation (GEE) was used to detect differences between the four groups regarding the course of pain.

RESULTS

No differences regarding adverse effects, LOS, and wound leakage were found. GEE revealed a significant difference in course of pain between group A and B, with group B experiencing higher NRS scores postoperatively than group A (p=0.021). No differences between the other groups were found.

INTERPRETATION

The results of the current study suggest that LIA with 300-mg (150ml) ropivacain might be more effective than 150-mg (75ml) ropivacain. Alteration in dose of gabapentin appears not to have influence on the course of pain.

Postoperative persistent chronic pain: what do we know about prevention, risk factors, and treatment

BACKGROUND AND OBJECTIVES

Postoperative persistent chronic pain (POCP) is a serious health problem, disabling, undermining the quality of life of affected patients. Although more studies and research have addressed the possible mechanisms of the evolution from acute pain to chronic postoperatively, there are still no consistent data about the risk factors and prevention. This article aims to bring what is in the panorama of the current literature available.

CONTENT

This review describes the definition, risk factors, and mechanisms of POCD, its prevention and treatment. The main drugs and techniques are exposed comprehensively.

CONCLUSION

Postoperative persistent chronic pain is a complex and still unclear etiology entity, which interferes heavily in the life of the subject. Neuropathic pain resulting from surgical trauma is still the most common expression of this entity. Techniques to prevent nerve injury are recommended and should be used whenever possible. Despite efforts to understand and select risk patients, the management and prevention of this syndrome remain challenging and inappropriate.

The Acute to Chronic Pain Transition: Can Chronic Pain Be Prevented?

Chronic postsurgical pain (CPSP) is a distressing disease process that can lead to long-term disability, reduced quality of life, and increased health care spending. Although the exact mechanism of development of CPSP is unknown, nerve injury and inflammation may lead to peripheral and central sensitization. Given the complexity of the disease process, no novel treatment has been identified. The preoperative use of multimodal analgesia has been shown to decrease acute postoperative pain, but it has no proven efficacy in preventing development of CPSP.

Anesthetic premedication: new horizons of an old practice

The practice of anesthetic premedication embarked upon soon after ether and chloroform were introduced as general anesthetics in the middle of the 19(th) century. By applying opioids and anticholinergics before surgery, the surgical patients could achieve a less anxious state, and more importantly, they would acquire a smoother course during the tedious and dangerous induction stage. Premedication with opioids and anticholinergics was not a routine practice in the 20(th) century when intravenous anesthetics were primarily used as induction agents that significantly shorten the induction time. The current practice of anesthetic premedication has evolved into a generalized scheme that incorporates several aspects of patient care: decreasing preoperative anxiety, dampening intraoperative noxious stimulus and its associated neuroendocrinological changes, and minimizing postoperative adverse effects of anesthesia and surgery. Rational use of premedication in modern anesthesia practice should be justified by individual needs, the types of surgery, and the anesthetic agents and techniques used. In this article, we will provide our readers with updated information about premedication of surgical patients with a focus on the recent application of second generation serotonin type 3 antagonist, antidepressants, and anticonvulsants.

Preventive analgesia for postoperative pain control: a broader concept

Pain from surgical procedures occurs as a consequence of tissue trauma and may result in physical, cognitive, and emotional discomfort. Almost a century ago, researchers first described a possible relationship between intraoperative tissue damage and an intensification of acute pain and long-term postoperative pain, now referred to as central sensitization. Nociceptor activation is mediated by chemicals that are released in response to cellular or tissue damage. Pre-emptive analgesia is an important concept in understanding treatment strategies for postoperative analgesia. Pre-emptive analgesia focuses on postoperative pain control and the prevention of central sensitization and chronic neuropathic pain by providing analgesia administered preoperatively but not after surgical incision. Additional research in pre-emptive analgesia is warranted to better determine good outcome measurements and a better appreciation with regard to treatment optimization. Preventive analgesia reduces postoperative pain and consumption of analgesics, and this appears to be the most effective means of decreasing postoperative pain. Preventive analgesia, which includes multimodal preoperative and postoperative analgesic therapies, results in decreased postoperative pain and less postoperative consumption of analgesics.

Effects of Preoperative Gabapentin on Postoperative Pain after Radical Retropubic Prostatectomy

Objective:

The impact of preoperative gabapentin on tramadol consumption using patient-controlled analgesia (PCA) and postoperative pain was assessed in patients undergoing radical retropubic prostatectomy (RRP).

Methods:

In this prospective, randomized trial, 51 patients undergoing RRP were randomized into two groups: the gabapentin group received 900 mg gabapentin orally 2 h before surgery; the control group did not receive gabapentin. Postoperative analgesia was provided by tramadol PCA. Pain was assessed using a visual analogue scale for 24 h, postoperatively.

Results:

Mean cumulative tramadol consumption at 24 h was comparable in the two groups. Pain scores at 45 min, 60 min and 2 h postoperatively, and the number of patients who required rescue analgesia, were significantly lower in the gabapentin group than in the control group. Side-effects were similar in the two groups.

Conclusions:

Preoperative administration of 900 mg gabapentin did not decrease tramadol consumption, but was associated with lower pain scores in the early postoperative phase and a reduced need for rescue analgesia, compared with controls, in patients undergoing RRP.

Pregabalin in acute and chronic pain

Pregabalin is a gamma-amino-butyric acid analog shown to be effective in several models of neuropathic pain, incisional injury, and inflammatory injury. In this review, the role of pregabalin in acute postoperative pain and in chronic pain syndromes has been discussed. Multimodal perioperative analgesia with the use of gabapentinoids has become common. Based on available evidence from randomized controlled trials and meta-analysis, the perioperative administration of pregabalin reduces opioid consumption and opioid-related adverse effects in the first 24 h following surgery. Postoperative pain intensity is however not consistently reduced by pregabalin. Adverse effects like visual disturbance, sedation, dizziness, and headache are associated with higher doses. The advantage of the perioperative use of pregabalin is so far limited to laparoscopic, gynecological, and daycare surgeries which are not very painful. The role of the perioperative administration of pregabalin in preventing chronic pain following surgery, its efficacy in more painful surgeries and surgeries done under regional anesthesia, and the optimal dosage and duration of perioperative pregabalin need to be studied. The efficacy of pregabalin in chronic pain conditions like painful diabetic neuropathy, postherpetic neuralgia, central neuropathic pain, and fibromyalgia has been demonstrated.

Effect of preoperative gabapentin on postoperative pain and tramadol consumption after minilap open cholecystectomy: a randomized double-blind, placebo-controlled trial

PURPOSE OF REVIEW

To evaluate the efficacy of a single preoperative dose of 600 mg of gabapentin for reducing postoperative pain and tramadol consumption after minilap open cholecystectomy.

METHOD

A total of 120 adult patients of either sex were randomly assigned to receive 600 mg of gabapentin or a matched placebo orally 2 h before operation in a double-blind manner. All the patients received gabapentin using the same technique. Postoperative analgesia was provided with intravenous patient-controlled analgesia with tramadol using a 50-mg initial bolus dose, 20-mg incremental dose, 15-min lockout interval and 4-h limit of 240 mg. Patients were assessed at 0, 2, 4, 8, 12, 24 and 48 h after operation for verbal analogue pain scores at rest and at movement. Consumption of tramadol on first and second postoperative days and any adverse effects were also recorded.

RESULTS

Verbal analogue pain scores were significantly lower on first postoperative day at all times of observation both at rest and at movement in gabapentin group than in placebo group (P<0.01). Tramadol consumption was also reduced by 33% in gabapentin group. But pain scores and tramadol consumption were similar in two groups on second postoperative day. Sedation was common but the incidence of postoperative nausea and vomiting was significantly lower in gabapentin group.

CONCLUSION

Preoperative administration of 600 mg of gabapentin resulted in significant reduction in postoperative verbal analogue pain scores at rest and at movement as well as tramadol consumption compared with placebo on first postoperative day. Lower incidence of nausea and vomiting was an additional advantage. Sedation was the commonest side effect.

The effects of gabapentin on acute and chronic pain after inguinal herniorrhaphy

BACKGROUND AND OBJECTIVE

To find out whether preoperative gabapentin use had a favourable effect on long-term postoperative pain in patients undergoing inguinal herniorrhaphy.

METHODS

Sixty male patients--aged 20-40 years--who were scheduled for unilateral inguinal herniorrhaphy under spinal anaesthesia were included in this prospective, randomized, double-blind study. The patients were randomly allocated to two groups: the gabapentin group (n=30) received single-dose 1.2 g oral gabapentin 1 h before surgery, and the placebo group received a placebo capsule instead. Spinal anaesthesia was performed with heavy bupivacaine, and all operations were performed by the same surgeon with the same technique. Postoperative analgesia was evaluated during sitting and lying with a visual analogue scale. Assessment of postoperative pain at 1, 3 and 6 months was carried out with an 11-point numerical rating scale; 0 indicating 'no pain' and 10 indicating 'worst pain imaginable'. Patients who had numerical rating scale scores of more than 0 were further evaluated with regard to the impact of pain on their daily activities.

RESULTS

When compared with the placebo group, the gabapentin group displayed significantly lower visual analogue scale scores (lying and sitting) and total tramadol consumption at 8, 12, 16, 20 and 24 h after surgery (P<0.05) and higher postoperative patient satisfaction scores (P<0.05). Numerical rating scale scores at 1, 3 and 6 months after surgery were lower in the gabapentin group than in the placebo group (P<0.05). The number of patients whose daily activities were adversely affected by pain was smaller in the gabapentin group at the first month; however, the two groups were found to be similar at 3 and 6 months.

CONCLUSION

We conclude that preoperative single-dose gabapentin decreases the intensity of acute postoperative pain, tramadol consumption and the incidence and intensity of pain in the first 6 months after inguinal herniorrhaphy.

A randomized controlled trial of perioperative administration of pregabalin for pain after laparoscopic hysterectomy

Pregabalin has anticonvulsant, antihyperalgesic, and anxiolytic properties. In this study we evaluated the control of pain after perioperative administration of pregabalin 300 or 600 mg, compared with diazepam 10mg. Altogether 91 women scheduled for laparoscopic hysterectomy were randomized to receive diazepam 10mg (D10), pregabalin 150 mg (P300) or 300 mg (P600) for premedication, and the dose was repeated after 12h, except for the D10 group, in which the patients received placebo. Up until the 1st postoperative morning, analgesia was provided by oxycodone using patient controlled analgesia. The visual analogue scale scores for pain and side effects, and the amounts of the analgesics were recorded for three days after surgery. The doses of oxycodone during hours 0-12 after surgery were similar in the three groups, whereas the dose of oxycodone during hours 12-24 after surgery was smaller in the P600 group than in the P300 group (0.09 vs. 0.16 mg kg(-1); P=0.025). The total dose of oxycodone (0-24h after surgery) was smaller in the P600 group than in the D10 group (0.34 vs. 0.45 mg kg(-1); P=0.046). The incidence of dizziness (70% vs. 35%; P=0.012), blurred vision (63% vs. 14%; P=0.002) and headache (31% vs. 7%; P=0.041) were higher in the P600 group than in the D10 group. In conclusion, perioperative administration of pregabalin 600 mg decreases oxycodone consumption compared with diazepam 10mg, but is associated with an increased incidence of adverse effects.

Pre-incisional epidural ropivacaine, sufentanil, clonidine, and (S)+-ketamine does not provide pre-emptive analgesia in patients undergoing major pancreatic surgery

BACKGROUND

The concept of pre-emptive analgesia remains controversial. This prospective, randomized, and double-blind study compared epidural administration of ropivacaine 2 mg ml(-1), sufentanil 0.5 microg ml(-1), clonidine 3 microg ml(-1), and S(+)-ketamine 0.25 mg ml(-1) (study solution) given before incision with the same combination started at the end of the operation.

METHODS

After testing the stability of the solution using high performance liquid chromatography (HPLC) and examining 12 patients for possible side-effects in comparison with the epidural infusion of ropivacaine 2 mg ml(-1) and sufentanil 0.5 microg ml(-1), 30 patients undergoing major pancreatic surgery were recruited into the study. Before induction of anaesthesia, an epidural catheter was inserted (TH6-8). Patients in Group 1 received a bolus of 8 ml followed by a continuous infusion (8 ml h(-1)) of the study solution before induction of anaesthesia. In Group 2, patients received the same volume of saline before operation, the study solution was started at the end of surgery. After operation, the infusion was maintained for at least 96 h using a patient-controlled epidural analgesia (PCEA) pump in both groups. Patients were evaluated up to the seventh postoperative day for pain and side-effects.

RESULTS

Visual analogue scale (VAS) values at rest were as follows: G1 vs G2: 24 h, 19 (sd 23) vs 6 (13); 48 h, 4 (10) vs 11 (21); and 72 h, 12 (22) vs 13 (21). VAS values during coughing and mobilization were also comparable. Total volume of epidural infusion was 904 (114) ml in G1 vs 892 (154) ml in G2. The incidence of side-effects (nausea, vomiting, and motor block) was low and not different between the groups.

CONCLUSIONS

Pre-incisional epidural analgesic infusion did not provide pre-emptive analgesia compared with administration started at the end of surgery, but both groups had low pain scores.

Perioperative pain

PURPOSE OF REVIEW

Incisional pain remains underevaluated and undermanaged while evidence is growing that perioperative treatments strongly influence patients' outcome. The present review examines the recent developments in mechanisms underlying perioperative pain and questions current understanding of incisional pain features observed in patients.

RECENT FINDINGS

Experimental models of incisional pain have highlighted specific mechanisms underlying perioperative pain plasticity, i.e. sensitization of sensory processing, clinically expressed by the development of hyperalgesia. In patients, however, the long-term impact of sensory system sensitization, e.g. development of residual pain, as well as the effects of perioperative pain management on sensitization, are still poorly understood, partly because most of the trials assess only the subjective experience of pain (by evaluation of either pain intensity or analgesic needs) instead of directly measuring objective changes (i.e. hyperalgesia) with quantitative sensory testing.

SUMMARY

Experimental studies and recent clinical trials using objective measures of sensory processing sensitization induced by surgical incision have shown the importance of hyperalgesia in perioperative pain. Effective perioperative block of nociceptive inputs from the wound as well as use of antihyperalgesic and analgesic drugs in combination seem the best way to control postoperative pain and specifically to prevent central sensitization.

A combination of gabapentin and local anaesthetics attenuates acute and late pain after abdominal hysterectomy

BACKGROUND AND OBJECTIVE

Gabapentin and local anaesthetics may decrease postoperative pain and analgesic needs. The aim of the study was to investigate the effect of the combination of these drugs on the analgesic needs as well as on acute and late pain after abdominal hysterectomy.

METHODS

Sixty patients undergoing abdominal hysterectomy were randomly assigned to receive postoperatively oral gabapentin 400 mg 6 hourly for 7 days plus continuous wound infusion of ropivacaine 0.75% for 30 h or placebo capsules identical to those of gabapentin for 7 days and continuous wound infusion of normal saline for 30 h. Morphine consumption (PCA) for 48 h, paracetamol 500 mg plus codeine 30 mg (Lonalgal tablets) intake on days 3-7, visual analogue pain scores at rest and after cough during the first 7 postoperative days, the need for analgesics at home and the presence and incidence of pain after 1 month were recorded.

RESULTS

The treatment group consumed less cumulative morphine over the first 48 h (31 +/- 13.2 mg vs. 50 +/- 20.5 mg in controls, P < 0.001) and less Lonalgal tablets on days 3-7 (z = 2.54, P = 0.011). The visual analogue score values at rest and after cough did not differ between the groups during the first 7 postoperative days. One month postoperatively, fewer patients in the treatment group experienced pain due to surgery than in the control group (17/27 vs. 21/24, P = 0.045).

CONCLUSION

Gabapentin and continuous wound infusion with ropivacaine 0.75% decreased analgesic needs and late pain in patients undergoing abdominal hysterectomy.

From preemptive to preventive analgesia

PURPOSE OF REVIEW

Much effort has been taken to prove that a treatment initiated before surgery is more effective in reducing postoperative pain compared with the same intervention started after surgery. Clinical studies failed to demonstrate major clinical benefits of preemptive analgesia, however, and the results of recent systemic reviews are equivocal. The present review will discuss recent clinical as well as experimental evidence of preemptive analgesia and examine the implications of a preventive postoperative pain treatment.

RECENT FINDINGS

Recent preclinical and clinical studies give strong evidence that neuronal hypersensitivity and nociception after incision is mainly maintained by the afferent barrage of sensitized nociceptors across the perioperative period. This is in contrast to pain states of other origin in which prolonged hypersensitivity is initiated during the injury. Therefore, not timing but duration and efficacy of an analgesic and antihyperalgesic intervention are most important for treating pain and hyperalgesia after surgery.

SUMMARY

Extending a multimodal analgesic treatment into the postoperative period to prevent postoperative pain may be superior compared with preemptive analgesia. In the future, appropriate drug combinations, drug concentrations and duration of preventive strategies need to be determined to be most beneficial for the management of acute and chronic pain after surgery.