Body composition and source of weight loss after bariatric surgery.

BACKGROUND: Little is known about the composition and source of weight loss after bariatric surgery for morbid obesity. PURPOSE: This study was undertaken to determine changes in weight, body mass index (BMI), lean body weight (LBW), fat weight (FW) and left ventricular cardiac mass (LVM) following vertical banded gastroplasty (VBG). METHODS: After VBG for morbid obesity, 26 women and four men (mean age = 39.1 years) were weighed and had body composition analysis undertaken at intervals. Thirteen patients underwent echocardiography preoperatively and 1 year postoperatively to determine change in LVM and LVM index. RESULTS: Over 12 months there was significant weight loss for all weight parameters examined (p < 0.05). Fat weight loss was most significant; total weight loss and reduction of BMI were significant but less so than fat loss (Wilcoxon's signed ranks test). LBW loss had the smallest contribution to weight loss (p < 0.0001). There was a significant loss of LVM and posterior cardiac wall thickness (p < 0.05). CONCLUSIONS: VBG can lead to loss of lean body weight and left ventricular mass, and more dramatically, fat weight, body weight, and BMI. Cardiac mass and lean body mass are preferentially conserved relative to body fat with weight loss after VBG.

Postprandial augmentation of portal hepatic inflow after prosthetic H-graft portacaval shunt.

Encephalopathy after portasystemic shunting generally occurs after eating. After partial portal decompression, encephalopathy is uncommon, presumably because of associated portal hemodynamics. However, after partial shunting, the changes in portal venous hemodynamics that occur with eating are unknown. With this in mind, 11 nonencephalopathic adults were studied more than 1 year after 8-mm H-graft portacaval shunt (PCS). The studies utilized color flow duplex ultrasound to determine the changes in portal vein (PV) and inferior vena cava blood flow that occur with eating a standardized meal. Following H-graft PCS, there is increased blood flow in the inferior vena cava after eating, particularly cephalad to the H-graft PCS, implying increased flow through the prosthetic shunt. Eating also increases hepatopedal blood flow in the PV distal to the H-graft PCS. Postprandial increases in hepatopedal portal blood flow may play an important role in avoiding encephalopathy after H-graft PCS.

Bioimpedance measurement of body water correlates with measured volume balance in injured patients.

Bioimpedance technology is being used increasingly to determine drug volume of distribution, body water status, and nutrition repletion. Its accuracy in patients experiencing large volume flux is not established. To address this, we undertook this prospective study in 54 consecutive seriously injured adults who had emergency celiotomy soon after arrival in the emergency department. Bioimpedance measurements were obtained in the emergency department before the patient was transported to the operating room, on completion of celiotomy, and 24 hours and 48 hours after celiotomy. Bioimpedance measurements of body water were compared with measured fluid balance. If insensible losses are subtracted from measured fluid balance, the percentage of body weight, which is body water determined by bioimpedance, closely follows fluid flux. This study supports the use of bioimpedance measurements in determining total body water even during periods of surgery, blood loss, and vigorous resuscitation.