Journal Watch—December 2015

| December 1, 2015

A quick look at the noteworthy articles in bariatric and metabolic research

Postsurgical Pain Management in the Bariatric Patient Population

Does preincisional infiltration with bupivacaine reduce postoperative pain in laparoscopic bariatric surgery?
Moncada R, Martinaitis L, Landecho M, et al. Obes Surg. 2015 Jun 18. [Epub ahead of print]
Synopsis: The authors conducted a retrospective randomized study to examine the influence of trocar site infiltration with bupivacaine on the management of postoperative pain in laparoscopic bariatric surgery. The study included 47 patients undergoing primary obesity surgery between January and September 2014. Laparoscopic gastric bypass was performed in 39 cases and sleeve gastrectomy in 8 cases. Patients were stratified into two groups depending on whether preincisional infiltration with bupivacaine and epinephrine was performed (study group, 27 patients) or not (control group, 20 patients). Visual analogue scale (VAS), International Pain Outcomes questionnaire, and rescue medication records were reviewed to assess postoperative pain. The study did not conclusively prove the efficacy of bupivacaine infiltration by any of the three evaluation methods analyzed. Nevertheless, the authors concluded that preincisional infiltration provides good level of comfort in the immediate postoperative period when analgesia is most urgent.
PMID: 26084250

Prospective randomized double-blind controlled trial of continuous local anesthetic infusion to reduce narcotic use in laparoscopic sleeve gastrectomy.
Cleveland EM, Peirce GS, Freemyer JD, et al. Surg Obes Relat Dis. 2015 Jan 6. [Epub ahead of print]
Synopsis: The researchers conducted a single institution prospective randomized double-blind controlled study to evaluate the efficacy of continuous infusion catheters (CIC) in laparoscopic sleeve gastrectomy. Eighty-two patients undergoing laparoscopic sleeve gastrectomy (LSG) received either .2% ropivacaine or .9% normal saline (placebo) via CIC. After discharge, total narcotic usage, total antiemetic usage, pain scores, and hospital length of stay were evaluated. A one-way ANOVA was used to assess statistical significance. Power was 80 percent to detect 52mg morphine equivalent difference.

Out of the 82 patients enrolled, 39 received ropivacaine, and 43 received placebo. There was no statistically significant difference in narcotic usage between the ropivacaine group and placebo group, 51.9mg versus 55.2mg, respectively (P= 0.63). Ondansetron usage was 10.7 mg and 10.6 mg for ropivacaine and placebo groups. (P= 0.98). Average pain score was 3.0 for each group (P= 0.632). Total hospital length of stay was 37.5 hours for ropivacaine group and 38.1 hours for placebo group (P= 0.768). The researchers found no difference in narcotic usage, antiemetic usage, pain scores, or hospital length of stay between ropivacaine and placebo groups. and concluded there is no utility of CIC in LSG.
PMID: 25892348

Bariatric surgery patients’ response to a chronic pain rehabilitation program.
Tabibian A, Grothe KB, Mundi MS, et al. Obes Surg. 2015;25(10):1917–1922.
Synopsis: The authors conducted a retrospective case-control study to compare treatment outcomes of a chronic pain rehabilitation program (psychological and pain variables, medication use, treatment completion rates) for post-bariatric surgery patients to those of a non-bariatric surgery control group. The setting observed was a three-week outpatient multidisciplinary chronic pain program in an academic medical center. The authors reviewed medical records of patients admitted to the Pain Rehabilitation Center at Mayo Clinic from 2008 to 2012. One hundred six patients with a history of bariatric surgery (cases) were identified and matched to 106 patients without a history of bariatric surgery (controls) on age, gender, and smoking status (n=202). Matched t tests and McNemar’s tests were used for analyses. Mean age was 46 years; 91percent were female and 58 percent were non-smokers. The majority of cases (71%) had undergone Roux-en-Y gastric bypass.

The authors found that bariatric patients had higher rates of benzodiazepine use at discharge (33 vs. 19%, p=0.0433) and were less likely to complete treatment (87 vs. 97%, p=0.007) compared to controls. Morphine equivalent use for cases was 127.3mg±135.4 (n=62) compared to 88.3 mg±95.3 (n=62), p=0.12, for controls at admission. The authors concluded that these results suggest that bariatric patients may be at risk for treatment nonadherence and have difficulty reducing medication use in the treatment of chronic pain.
PMID: 25720517

Intravenous acetaminophen in bariatric surgery: effects on opioid requirements.
Gonzalez AM, Romero RJ, Ojeda-Vaz MM, Rabaza JR. J Surg Res. 2015;195(1):99-104. Epub 2015 Jan 14.
Synopsis: The researchers conducted a retrospective study was performed in patients who underwent bariatric surgery to evaluate the effect on opioid consumption when intravenous acetaminophen (IVA) is administered in bariatric surgery patients.

Group A included those patients who received IVA perioperatively and group B those who did not. The amount of opioids administered was calculated and compared for each group. Group A included 38 cases (44.7%) and group B included 47 cases (55.3%). A comparison was performed in terms of age (P= 0.349), body mass index (P= 0.311), gender (P= 0.890), American Society of Anesthesiologist score (P= 0.438), total surgical time (P= 0.497), perioperative complications (P= 0.786), number of procedures per surgeon (P= 0.08), and type of surgical procedure (P≤ 0.01). Group A had a mean 24-h total opioid dose of 99.5mg, whereas group B of 164.6mg (P= 0.018). Group A received 39.5 percent less opioids than group B. A post-hoc analysis determined a statistical power of 0.74.

The researchers concluded that IVA used perioperatively can decrease opioid consumption in patients after bariatric surgery. Randomized trials are needed to corroborate these results.
PMID: 25680474

Dexmedetomidine versus morphine infusion following laparoscopic bariatric surgery: effect on supplemental narcotic requirement during the first 24 h.
Abu-Halaweh S, Obeidat F, Absalom AR, et al. Surg Endosc. 2015 Nov 5. [Epub ahead of print]
Synopsis: The primary aim of this pilot study was to determine whether the dexmedetomidine infusion initiated immediately after laparoscopic bariatric surgery, offers an advantage over a morphine infusion with respect to rescue morphine and paracetamol requirements over the first 24 post-operative hours.

Sixty adult patients with morbid obesity scheduled for laparoscopic bariatric surgery were randomly assigned to receive an infusion of either 0.3mcg/kg/h dexmedetomidine (Group D) or 3mg/h Morphine (Group M) for 24 h immediately post-operatively. All patients received standardized general anesthesia and were evaluated and treated for pain in the intensive care unit by providers who were blinded to their treatment group. The primary outcome was the need for supplemental, “rescue” paracetamol (Dolargan. Hikma, Jordan) and morphine titrated to achieve visual analog scales (VAS) of <40 and <70, respectively.

A total of 60 patients (77 % female, mean age 33.5 years ± 9.5 and body mass index (BMI) 43.0 ± 4.5) were randomized to Group M and 30 to Group D. There were no significant differences in mean rescue paracetamol and morphine requirements. Mean total morphine requirements in Group D were 6.1 ± 3.1mg, whereas 72.9 ± 2.2mg in Group M (p <0.0001).

The authors concluded that an intravenous infusion of dexmedetomidine, initiated and continued for 24 h following laparoscopic bariatric surgery, can decrease the overall morphine requirements during this period. This pilot study demonstrated that the postoperative initiation of dexmedetomidine can be morphine sparing following laparoscopic bariatric surgery.
PMID: 26541738

Effect of a Roux-en-Y gastric bypass on the pharmacokinetics of oral morphine using a population approach.
Lloret-Linares C, Hirt D, Bardin C, et al. Clin Pharmacokinet. 2014;53(10):919–930.
Synopsis: In this article, the authors study the pharmacokinetics of oral morphine in patients with morbid obesity before and after Roux-en-y gastric bypass (RYGB) surgery, to identify the effects of RYGB and the subsequent reversal of morbid obesity on the pharmacokinetic parameters of morphine.

The pharmacokinetics of oral morphine (30mg) were studied in 30 patients with obesity before (Visit 1) and then 7 to 15 days (Visit 2) and 6 months (Visit 3) after RYGB. A population pharmacokinetic model was used to describe the time course of the plasma morphine concentration, to study the effect of RYGB on morphine pharmacokinetics and to estimate inter-patient variability.

The oral morphine time to maximum plasma concentration (t max) was twofold lower and maximum plasma concentration (C max) was 1.7 times higher at Visit 2, and t max was 7.5 times lower and C max 3.3 times higher at Visit 3 than at Visit 1. The mean oral morphine area under the plasma concentration-time curve (AUC) increased significantly (1.55-fold) between Visits 1 and 3. Changes in body mass index (BMI) after RYGB were clearly associated with decreased apparent oral morphine clearance and apparent central and peripheral morphine volumes of distribution. None of the other anthropometric parameters explained the inter-subject variability in morphine exposure better than BMI.

The authors concluded that RYGB and the BMI reduction that followed it dramatically increased the rate of morphine absorption and slightly increased morphine exposure. The dose of immediate-release forms of morphine may be divided in patients with obesity after RYGB to prevent adverse events due to early and high morphine plasma peaks.
PMID: 25141973

Sugammadex reduces postoperative pain after laparoscopic bariatric surgery: a randomized trial.
Castro DS Jr1, Leão P, Borges S, et al. Surg Laparosc Endosc Percutan Tech. 2014;24(5):420–423.
Synopsis: The researchers conducted a controlled trial enrolling 88 participants with morbid obesity submitted to laparoscopic bariatric surgery under general anesthesia using muscle relaxation. Participants were randomly assigned into two groups: one received sugammadex (SUG group; n=44) at the end of surgery and the other neostigmine (NEO group;n=44). In the postanesthetic care unit (PACU), the researchers evaluated pain using the visual analogue scale in four different moments: 1) arrival in the PACU, 2) 30 minutes after arrival, 3) 60 minutes after arrival, and 4) immediately before leaving the PACU. They also recorded the presence of postoperative nausea and vomits (PONV) and the duration of the PACU stay before discharge to the ward. The researchers found the following among the SUG group: lower visual analogue scale pain scores at 30 and 60 minutes after arriving to the PACU (P<0.05), less PONV, and earlier discharge compared to the NEO group.

Reserchers concluded that Sugammadex is associated with less pain felt in the PACU and that this “opioid-sparing” effect.
PMID: 24752165

Category: Journal Watch, Past Articles

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