Gabapentin in procedure-specific postoperative pain management - preplanned subgroup analyses from a systematic review with meta-analyses and trial sequential analyses

Background

It has been argued that postoperative pain treatment should be “procedure-specific”, since different analgesics may have specific effects dependent on the surgical procedure. The aim of the present subgroup analysis was to compare the beneficial and harmful effects of perioperative gabapentin treatment in different surgical procedures.

Methods

Relevant databases were searched for randomized clinical trials (RCTs) comparing gabapentin versus placebo. Two authors independently screened titles and abstracts, extracted data and assessed risk of bias. The primary outcomes were differences in 24-h morphine consumption, and serious adverse events (SAE) between surgical procedures. These subgroup analyses were predefined in a PRISMA compliant systematic review registered at PROSPERO (ID: CRD42013006538). It was predefined that conclusions should primarily be based on trials classified as overall low risk of bias.

Results

Seventy-four RCTs with 5645 patients were included, assessing benefit and harm in cholecystectomy, hysterectomy, mastectomy, and arthroplasty surgery, spinal surgery, and thoracic surgery.

Only eight of 74 trials were classified as overall low risk of bias limiting our ability to conclude on the estimates in most meta-analyses. The differences between surgical procedures in these trials were not statistically significant when tested for subgroup differences. Fifteen trials with 1377 patients reported a total of 59 SAEs, most of which were observed in the thoracic surgery group.

Conclusion

Both beneficial and harmful effects in these subgroup analyses were influenced by bias and insufficient data, limiting conclusions. With these limitations, we could not adequately test for differences in beneficial or harmful outcomes between six surgical subgroups undergoing perioperative gabapentin treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/s12871-017-0373-8) contains supplementary material, which is available to authorized users.

The beneficial effect of transversus abdominis plane block after laparoscopic cholecystectomy in day-case surgery: a randomized clinical trial

BACKGROUND

Laparoscopic cholecystectomy is associated with postoperative pain of moderate intensity in the early postoperative period. Recent randomized trials have demonstrated the efficacy of transversus abdominis plane (TAP) block in providing postoperative analgesia after abdominal surgery. We hypothesized that a TAP block may reduce pain while coughing and at rest for the first 24 postoperative hours, opioid consumption, and opioid side effects in patients undergoing laparoscopic cholecystectomy in day-case surgery.

METHODS

In this randomized, double-blind study, 80 patients undergoing laparoscopic cholecystectomy in our day-case surgery unit were allocated to receive either bilateral ultrasound-guided posterior TAP blocks (20 mL 0.5% ropivacaine) or placebo blocks. Postoperative pain treatment consisted of oral acetaminophen 1000 mg × 4, oral ibuprofen 400 mg × 3, IV morphine (0-2 hours postoperatively), and oral ketobemidone (2-24 hours postoperatively). The primary outcome was postoperative pain scores while coughing calculated as area under the curve for the first 24 postoperative hours (AUC/24 h). Secondary outcomes were pain scores at rest (AUC/24 h), opioid consumption, and side effects. Patients were assessed 0, 2, 4, 6, 8, and 24 hours postoperatively. Group-wise comparisons of visual analog scale (VAS) pain (AUC/24 h) were performed with the 2-sample t test. Morphine and ketobemidone consumption were compared with the Mann-Whitney test for unpaired data. Categorical data were analyzed using the χ(2) test.

RESULTS

The primary outcome variable, VAS pain scores while coughing (AUC/24 h), was significantly reduced in the TAP versus the placebo group (P = 0.04); group TAP: 26 mm (SD 13) (weighted average level) versus group placebo: 34 (18) (95% confidence interval): 0.5-15 mm). VAS pain scores at rest (AUC/24 h) showed no significant difference between groups. Median morphine consumption (0-2 hours postoperatively) was 7.5 mg (interquartile range: 5-10 mg) in the placebo group compared with 5 mg (interquartile range: 0-5 mg) in the TAP group (P < 0.001). The odds ratio of a random patient in group TAP having less morphine consumption than a random patient in group placebo was P (group TAP < group placebo) = 0.26 (confidence interval: 0.15, 0.37) where 0.5 represents no difference between groups. There were no between-group differences in total ketobemidone consumption, levels of nausea and sedation, number of patients vomiting, or consumption of ondansetron.

CONCLUSIONS

TAP block after laparoscopic cholecystectomy may have some beneficial effect in reducing pain while coughing and on opioid requirements, but this effect is probably rather small.

Effective dermatomal blockade after subcostal transversus abdominis plane block

INTRODUCTION

The ultrasound-guided transversus abdominis plane (TAP) block is used to treat postoperative pain after abdominal surgery. Abdominal wall sensory nerves are anaesthetised by injecting local anaesthetics into the neurofascial plane between the internal oblique and the transversus abdominis muscles. Sensory assessment of a TAP block may guide the decision on the extent of the block. The purpose of this study was to investigate if the dermatomal extent of sensory blockade after injection of 20 ml 0.5% ropivacaine bilaterally into the TAP can be assessed using cold and pinprick sensation.

MATERIAL AND METHODS

Subcostal TAP block was performed bilaterally in 20 awake patients scheduled for elective abdominal surgery. Sensory change in dermatomes T4-L4 was tested with pinprick using a blunt needle and cold disinfectant swabs after 10, 20 and 30 minutes.

RESULTS

Data from 20 patients (40 blocks) were analysed. Eighteen patients registered sensory change after subcostal TAP block, and dermatomes T10-T12 were blocked after 30 minutes in all of these patients. Spread of sensory change to dermatomes T5-L3 was variable.

CONCLUSION

This study confirmed that the dermatomal extent of a sensory blockade after a single-shot subcostal TAP block can be assessed using cold and pinprick sensation.

FUNDING

not relevant.

TRIAL REGISTRATION

The study was registered at clinicaltrials.gov with the registration number NCT01024868.

The transversus abdominis plane block: a valuable option for postoperative analgesia? A topical review

The transversus abdominis plane (TAP) block is a newly described peripheral block involving the nerves of the anterior abdominal wall. The block has been developed for post-operative pain control after gynaecologic and abdominal surgery. The initial technique described the lumbar triangle of Petit as the landmark used to access the TAP in order to facilitate the deposition of local anaesthetic solution in the neurovascular plane. Other techniques include ultrasound-guided access to the neurovascular plane via the mid-axillary line between the iliac crest and the costal margin, and a subcostal access termed the 'oblique subcostal' access. A systematic search of the literature identified a total of seven randomized clinical trials investigating the effect of TAP block on post-operative pain, including a total of 364 patients, of whom 180 received TAP blockade. The surgical procedures included large bowel resection with a midline abdominal incision, caesarean delivery via the Pfannenstiel incision, abdominal hysterectomy via a transverse lower abdominal wall incision, open appendectomy and laparoscopic cholecystectomy. Overall, the results are encouraging and most studies have demonstrated clinically significant reductions of post-operative opioid requirements and pain, as well as some effects on opioid-related side effects (sedation and post-operative nausea and vomiting). Further studies are warranted to support the findings of the primary published trials and to establish general recommendations for the use of a TAP block.

Effect of perioperative beta blockade in patients with diabetes undergoing major non-cardiac surgery: randomised placebo controlled, blinded multicentre trial

OBJECTIVES

To evaluate the long term effects of perioperative beta blockade on mortality and cardiac morbidity in patients with diabetes undergoing major non-cardiac surgery.

DESIGN

Randomised placebo controlled and blinded multicentre trial. Analyses were by intention to treat.

SETTING

University anaesthesia and surgical centres and one coordinating centre.

PARTICIPANTS

921 patients aged > 39 scheduled for major non-cardiac surgery.

INTERVENTIONS

100 mg metoprolol controlled and extended release or placebo administered from the day before surgery to a maximum of eight perioperative days.

MAIN OUTCOME MEASURES

The composite primary outcome measure was time to all cause mortality, acute myocardial infarction, unstable angina, or congestive heart failure. Secondary outcome measures were time to all cause mortality, cardiac mortality, and non-fatal cardiac morbidity.

RESULTS

Mean duration of intervention was 4.6 days in the metoprolol group and 4.9 days in the placebo group. Metoprolol significantly reduced the mean heart rate by 11% (95% confidence interval 9% to 13%) and mean blood pressure by 3% (1% to 5%). The primary outcome occurred in 99 of 462 patients in the metoprolol group (21%) and 93 of 459 patients in the placebo group (20%) (hazard ratio 1.06, 0.80 to 1.41) during a median follow-up of 18 months (range 6-30). All cause mortality was 16% (74/462) in the metoprolol group and 16% (72/459) in the placebo group (1.03, 0.74 to 1.42). The difference in risk for the proportion of patients with serious adverse events was 2.4% (- 0.8% to 5.6%).

CONCLUSIONS

Perioperative metoprolol did not significantly affect mortality and cardiac morbidity in these patients with diabetes. Confidence intervals, however, were wide, and the issue needs reassessment.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN58485613.

[Maternal serum screening for congenital abnormalities and Down syndrome in Sønderjylland County. Eight years of experience]

From January 1991 to December 1998 second-trimester maternal serum screening (Doubletest and Tripletest) for malformations and Down syndrome has been offered to pregnant women younger than 35 years of age living in Sønderjyllands county, Denmark. Follow-up of all cases of chromosome abnormalities and severe foetal malformations identified pre- or postnatally has been carried out. A total of 17,023 women were screened. Sixty-eight percent (17/25) of Down Syndrome pregnancies were detected. Three percent of the screened women were offered an amniocentesis due to a calculated risk of DS greater than 1:400 at birth. The positive predictive value was 1:30. For the three-year period 1996-1998 (Tripletest) the results were more promising: 91% (10/11) were detected, 3.9% were offered an amniocentesis, the positive predictive value was 1:21. In the eight-year period 80% (8/10) of the spina bifida cases were detected, all the cases (6/6) of anencephaly and 75% (6/8) of abdominal wall defects. One point six percent of the screened women were offered an amniocentesis due to high risk of a neural tube defect. The results confirm that second trimester maternal serum screening is a reliable method for determining the risk of severe foetal malformations and Down syndrome.

Reduced albumin binding of MADDS--a measure of bilirubin binding--during pregnancy and delivery

It was the purpose of the present study to investigate whether the decrease in the ability of plasma albumin to bind bilirubin, noted in pregnancy and during delivery, takes place in one step, during pregnancy alone, or in two steps, during both pregnancy and delivery. Furthermore, it was investigated whether a possible decrease during labor was related to the method of delivery itself. The material comprised (a) 17 pregnant women who delivered vaginally; (b) 25 women who were delivered by Cesarean Section; and (c) a group of 25 non-pregnant women. The reserve albumin concentration for binding of MADDS (a measure of the binding of unconjugated bilirubin), the total albumin concentration and the ratio between them were constant in the 6-week period up to birth and were significantly lower than the corresponding values in the non-pregnant group. During labor a significant decrease in reserve albumin and ratio of reserve albumin to total albumin was observed, while no change in the total albumin concentration was noted. No significant difference in reserve albumin concentration, total albumin concentration and ratio between them was found when the group of mothers who delivered vaginally was compared to the Cesarean Section group. It is concluded that the decrease in the ability of plasma albumin to bind unconjugated bilirubin takes place stepwise. The first step is a significant reduction during pregnancy followed by a further decrease during labor. The method of delivery is of no significance.

Neurogenic pulmonary edema: treatment with dobutamine

In the case of a patient with complicating subarachnoid hemorrhage, an infusion of dobutamine was followed by a massive diuresis and regression of severe neurogenic pulmonary edema. It is suggested that the reduction in total peripheral vascular resistance and the increase in cardiac contractility accounts for the observed beneficial effect and indicate that dobutamine is a suitable drug for the treatment of neurogenic pulmonary edema.

Xanthine and hypoxanthine in amniotic fluid during pregnancy

Xanthine and hypoxanthine are indicators of cellular hypoxia. The purpose of our study was to establish a reference range for the concentrations of xanthine and hypoxanthine in amniotic fluid. Of a total of 38 included in the investigation, 27 pregnant women were found to have low values for xanthine (less than 1.2 mumol/l) and hypoxanthine (less than 0.4 mumol/l). To our knowledge, this is the first attempt to define a reference range for xanthine and hypoxanthine concentration in amniotic fluid during pregnancy.