Intramucosal pH Measurements for Extremely Obese Patients During Laparoscopic Bariatric Surgery

Abstract

To the Editor: Excessive obesity is defined as a body weight ≥225 % over the ideal weight or body mass index 50 kg · m2(1). As surgical treatment of obesity has developed, interest is renewed in the anesthetic management of these patients (2). Laparoscopic surgical techniques seem beneficial in obese patients (3). The gastric tonometry is a minimally invasive device by which the adequacy of splanchnic blood flow is assessed indirectly (4). We aimed to investigate intramucosal pH (pHi) measurements for excessively obese patients during laparoscopic bariatric surgery. Twelve obese patients with (ASA) class II-III who undergoing laparoscopic gastric banding were included in this study (Table 1). Table 1: The Patients’ Main Characteristics (Number or Mean ± sd)All patients received a low molecular weight heparin and ranitidine 12 h prior to the operation. All anesthetics and other medications were administered according to the corrected weight. Corrected weight was calculated using the following equation. Corrected weight =[0.4 × excess weight] + ideal weight (5). Anesthesia was induced with fentanyl 2 μg · kg−1 and propofol 1 mg · kg−1, a propofol infusion was administered at a rate of 6 mg · kg−1/h−1 until the end of the operation. Atracurium 0.6 mg · kg−1 was given to facilitate orotracheal intubation with a cuffed tube. Throughout the operation, fentanyl 2 μg · kg−1 and atracurium 0.1 mg · kg−1 were given as needed. Controlled ventilation was performed in all patients and ventilator was set to deliver 10 mL · kg−1 tidal volume, 10 min−1 frequency, I:E 1:2, inspiratory pause 20 % of inspiration and a constant inspiratory flow rate. Inspired oxygen content was 50% oxygen-air mixture and fresh gas flow rate was 8 L · min−1. Intra-abdominal pressure was held at 12 mm Hg during laparoscopy and a constant CO2 flow of 2 L · min−1 administered through a laparoscopic insufflator device. After anesthesia induction, arterial catheter was placed into radial artery. Direct arterial pressure measurements and blood gas sampling were performed via arterial catheter. The gastric tonometer (Trip TM, Tonometrics, Helsinki, Finland) was placed into stomach before the surgical incision and its position was verified with fluoroscopy. Mean arterial pressure, heart rate, and pHi values were measured in four periods: after 15 min of anesthesia induction (induction), after 20 min of pneumoperitoneum (pneumoperitoneum), after 10 min of desufflation (desufflation), and after 20 min of extubation (extubation). Atropine 0.01 mg/kg and neostigmine 0.02 mg/kg were administered to antagonize the neuromuscular blockade. At the end of the operation and following emergence from anesthesia, all patients were tracheally extubated and sent to postanesthetic care unit. There is no single anesthetic regimen shown to be superior in obese patients (Table 2). Obesity predisposes to cardiovascular morbidity. Hemodynamic variables could be affected from morbidly obese patients due to many factors (5). In our study, we determined slight changes in mean arterial pressure and heart rate that have no significant statistical result. Table 2: Intramucosal pH and Hemodynamic Values (Mean ± sd)Although there had been many studies evaluating different aspects of physiology during surgery and anesthesia in the obese patients (6–9), our study is the only one that utilized gastric tonometry. There is no clinical evidence or data that report that bariatric surgery operations or gastric band has an effect on stomach or splanchnic circulation. In long-term studies, the gastric band is well tolerated by these patients. Chronic erosion is a common complication due to the gastric band’s local effect, not from stomach nor splanchnic circulation disorder (10). pHi measurements can be used to assess perfusion, and we observed slight decreases in pHi in our patients. There may be many factors responsible for the decrease of splanchnic perfusion from cardiac depression caused by anesthesia to increased intra-abdominal pressure due to pneumoperitoneum. Our study was not designed to evaluate these factors. In conclusion, we found no statistical changes on pHi on the laparoscopic bariatric surgery for excessively obese patients. Ziya Salihoglu, MD Sener Demiroluk, MD Yalim Dikmen, MD Mustafa Taskin, MD