Development of metabolic alkalosis after massive transfusion during orthotopic liver transplantation

Five patients undergoing orthotopic liver transplantation were investigated for changes in acid-base homeostasis secondary to large volume transfusions. All patients developed a transient acidemia during the operative period, followed by alkalemia which persisted into the early postoperative period. The patients received an estimated mean of 750 mEq of citrate, which appeared to cause metabolic alkalosis. The biochemical basis underlying the regulation of citrate metabolism that may have led to the timing, extent, and duration of the subsequent metabolic alkalosis is presented. Finally, the time course for the development of metabolic alkalosis may be a potentially sensitive indicator of early allograft function.     

The effect of dextrose and amino acids on respiratory function and energy expenditure in morbidly obese patients following gastric bypass surgery

Hypocaloric dextrose administration results in a diminished minute ventilation, metabolic rate, and ventilatory responsivity to hypercapnea and hypoxia which is rapidly reversed by provision of amino acids in individuals of normal weight. This study compared the effects of peripheral intravenous dextrose and amino acid infusion on respiratory parameters and energy expenditure in 25 morbidly obese patients undergoing gastric bypass surgery. On the first postoperative day, respiratory rate increased (P less than 0.01) and tidal volume decreased (P less than 0.001) maintaining minute ventilation at slightly less than preoperative levels but on subsequent days minute ventilation exceeded baseline values (P less than 0.005) primarily by a sustained increased respiratory rate. Oxygen consumption (P less than 0.005), carbon dioxide production (P less than 0.05), and resting energy expenditure (P less than 0.01) all declined 25% from baseline values on the first postoperative day and subsequently reverted to preoperative values. The type of intravenous fluid had no effect on any of these parameters. A significant difference in respiratory quotient (P less than 0.05) was noted between the two intravenous fluid regimens attributable to the oxidation of the dextrose calories. The failure to detect a difference in metabolic rate or to stimulate respiration despite elevation of serum branched chain amino acids (P less than 0.0001) and ketone bodies (P less than 0.0001) with protein infusion does not suggest a role for nutrient manipulation of respiration in the postoperative care of the morbidly obese patient.     

Reducing arrhythmias associated with central venous catheter insertion or exchange.

A recent study demonstrated that the incidence of new arrhythmias occurring during central venous catheter insertion or exchange was 41% atrial and 25% ventricular arrhythmias (12% couplets or greater). Over-insertion of the guidewire, causing direct stimulation to the right side of the heart, has been postulated to be the causative factor. A new technique that allows the operator to control the length of guidewire inserted was developed. With this technique on a population of hospitalized patients, similar to those in the previous study, the incidence of atrial arrhythmias decreased to 32% and the incidence of ventricular arrhythmias to 6% (single premature ventricular contractions only). Although this new technique has limitations, there was a dramatic improvement in the incidence of cardiac arrhythmias. These results indicate a need for modifications in the available equipment to avoid the infrequent but life-threatening complication of malignant arrhythmia.     

Role of biochemical mediators in clinical nutrition and surgical metabolism

Over the past several decades, research on the role of mediators in inflammation, immunity, repair processes, cell growth, and substrate metabolism have centered around the use of purified products of stimulated macrophages. With the current availability of recombinant mediators, the participation of individual monokines in cellular metabolism has been more clearly defined. Interactions among various mediators have been demonstrated, but their exact role in metabolism is currently under intense study. With the use of recombinant monokines, formal evidence for their participation in the acute phase response has been developed. Their use has also assisted in the reinterpretation of data gathered in older studies using purified preparations, which were almost certainly contaminated with several monokines. In this review we will try to give the reader insight into recent advances in the understanding of the role of cellular mediators in relation to nutrition and intermediary metabolism. With a clearer knowledge of the role of cellular mediators in the pathophysiology of disease, it may be possible to develop rationales for their therapeutic use as modulators of substrate metabolism during critical illness.