What is the normal drain amylase range for laparoscopic sleeve gastrectomy?

Viet Phuong, MD, Timothy S Kuwada, MD, Ian Villanueva, MD, Keith Gersin, MD, Dimitrios Stefanidis, MD, PhD. Carolinas Healthcare System.

Staple line and anastomotic leaks from the foregut extravasate salivary amylase. Elevated drain amylase (DA) levels have been associated with leaks in bariatric surgery. The ability to detect elevations in DA may improve early detection of leaks. However, interpretation of DA drain amylase (DA) levels is complicated by an ill defined normal range. This study describes our experience with routine drain placement in laparoscopic sleeve gastrectomy (LSG) with an emphasis on defining the distribution of DA levels.

Study Design: Retrospective review of prospectively collected database of a single surgeon’s consecutive series of LSG from 2008 to 2013. Patients routinely had a 10mm flat JP placed along the vertical staple line. Staple line reinforcement was used and a “leak test” was performed with intra-operative gastroscopy. DA was measured on the morning of POD #2. Drains were typically removed just prior to discharge. If the DA was >100 IU/L, it was repeated 6 hours later to insure stability. Primary outcome was the distribution of DA levels. Age, BMI, LOS, gender, ASA, staple line complications (leak and bleeding), and drain complications were also recorded. Postoperative bleeding was defined as acute anemia requiring transfusion. The “normal” DA range was defined as one standard deviation from the mean.
 
Results: The study group consisted of 248 patients. Results are summarized in table 1. There were no leaks or drain complications. The mean drain amylase was 85 IU/L; 77% were <100 IU/L and only 6.8% were beyond 1 standard deviation (greater than 182 IU/L) , 77% were <100 IU/L. Six patients (2.4%) had a postoperative bleeding event, none were intraluminal. There was no correlation between drain amylase level and LOS. There were no perioperative re-operations.

The vast majority of drain amylase levels in our LSG series were less than 100IU/L. Although we did not have any leaks in this study, DA levels above 182 IU/L were statistical outliers (above one standard deviation). Morbidity from the drain was nil. Drain placement in LSG enables monitoring of amylase levels adjacent to the staple line. Further studies are required to determine the role and cost effectiveness of DA in the bariatric population.

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