The Effect of Plethysmographic Variability Index Monitoring on Fluid Replacement in Bariatric Surgery

Obesity is defined as an increase in body weight beyond requirements as a result of excessive fat accumulation in the body and is common Obesity leads to an increase in health problems and morbidity and mortality, as well as individual and social problems and a decrease in the workforce. Despite sports, diet, lifestyle changes and medical treatments, the rate of obesity continues to increase in the population. The most effective and durable treatment option for morbid obesity is bariatric surgery. Video laparoscopic bariatric surgery (VLBS) is recognized as the best surgical technique for morbidly obese individuals with health complications associated with excess body fat. Despite the proven benefits of VLBS, it can model a systemic inflammatory response. VLBS also poses an inherent risk of pneumoperitoneum for the kidneys due to high intra-abdominal pressure, which reduces cortical capillary blood flow by increasing renal vascular resistance. As a result, the glomerular filtration rate (GFR) decreases and transient oliguria occurs. Acute renal failure manifested as a large increase in creatinine levels with oliguria.

It is a preventable complication with intraoperative anesthesia management.Glomerular filtration rate (GFR) and increased renal plasma flow cause hyperfiltration syndrome in obesity. Adinopectin, proinflammatory cytokines, oxidative stress and pharmacological nephrotoxicity are the mechanisms affecting acute kidney injury in obesity. Chronic renal failure occurs as a result of a decrease in albiminuria and GFR. They are the causes of postoperative renal failure in patients with diabetes, a history of kidney disease, using antihypertensive drugs containing diuretics, and obese patients with a BMI greater than 50 kg / m2, prolonged operation time, and intraoperative hypotension.

The frequency of acute tubular necrosis (ATN) and renal failure due to postoperative rhabdomyolysis is also increased in obese patients. Fluid management is important to prevent this. The fluid requirement should be higher than planned. In order to prevent the development of postoperative ATN and renal failure, 4-5 liters of crystalloid fluid should be given in 2-3 hours or urine output above 1.5 ml / kg / h should be provided.

According to TVA, there are studies performing crystalloid fluid replacement in a wide range of 15-40 ml / kg.

In obese patients, changes in distribution volume such as decreased hepatic blood flow, increase in renal blood flow and glomerular filtration rate and increase in the amount of free-flowing drug are the most important factors affecting the pharmacokinetics of drugs. Drug doses used in these patients are recommended to be calculated according to total body weight (TVA), ideal body weight (IVA), and lean body weight (HVA = IVA + 20%), taking into account the lipophilic nature of the drug. For example in induction; when using high lipophilic drugs according to YVA or IVA; moderately lipophilic For drugs, the dosage can be increased by 20-40% and used according to the YVA.Propofol's high lipophilic properties cause its effect to start very quickly and to be short-lived. It has been shown in many studies that there is no usable accumulation or prolongation of propofol compared to TVA in obese patients.