Protein-sparing therapy during pneumococcal infection in rhesus monkeys

Prehepatic total parenteral nutrition in the chair-adapted primate

The relative efficacy of prehepatic and central venous infusion of total parenteral nutrition (TPN) was evaluated in a chair-adapted primate model. Four adult male monkeys (Macaca fascicularis) underwent surgical placement of a silastic catheter in both the portal vein (PV) and superior vena cava (SVC). Following recovery (10 days), each animal received two courses of TPN (100 kcal and 4 g of protein/kg/day) for 10 days each via the PV and SVC in an alternating crossover manner. The prehepatic (PV) infusion of TPN in the well nourished, chair-adapted primate results in maintenance of weight (PV: delta - 0.07 kg; SVC:delta - 0.07 kg), nitrogen equilibrium (PV:+ 0.8 g N/day; SVC: + 0.7 g N/day), and trends in serum albumin (PV:delta - 0.35 g %; SVC: delta - 0.38 g %), and total iron binding capacity (PV:delta + 44 mg %; SVC:delta + 8.67 mg %) comparable to the SVC route. No significant abnormalities in liver enzyme production were observed with either route of infusion. Whole body protein synthesis rates using 15N-glycine tracer were likewise comparable (PV = 2.05 g N/kg/day; SVC = 2.18 g N/kg/day). Prehepatic delivery and primary hepatic modulation of substrates does not substantially improve the efficacy of parenteral nutrient administration. Intestinal modification of substrates may be the most important contributing factor in the supposed superiority of enteral alimentation.

A primate model for enteral nutrition by tube

To establish an animal model for the controlled study of enteral nutrition by tube, five adult chair-adapted primates (Macaca fasicularis) had gastrostomy and jejunostomy tubes placed for the delivery of a modified protein isolate diet. Following 7 days of postoperative depletion with a hypocaloric infusion of dextrose (20 kcal, 0 g N/kg/day), the animals were repleted for 10 days with tube feedings (124 kcal, 0.73 g N/kg/day). There was no operative mortality or morbidity and each animal demonstrated conversion to anabolism by significant weight gain, positive nitrogen balance, and net protein synthesis as determined by [15N]glycine protein turnover rates. Significant correlation was found between caloric intake and nitrogen balance at the level of nitrogen provided in this diet (r = 0.88, p less than 0.05). This model was found to be well suited for the surgical and nutritional techniques required for the long-term study of enteral nutrition by tube.

Hyperalimentation in primates. A nutritional model

To establish the subhuman primate as an effective laboratory animal in parenteral nutrition research, 18 male macaque monkeys were adapted to chronic chair restraint and maintained on intravenous nutrition for 1- and 2-week periods. The animals remained in the restraint chairs for 11.6 +/- (2.3) weeks and the inferior vena cava catheters remained for 53 +/- (7.8) days. Catheter and metabolic complications during intravenous nutrition infusion were few and morbidity was low. The animals maintained weight, serum albumin, and serum transferrin levels as well as a positive nitrogen balance during the study period. The macaque is a highly suitable model for nutritional studies requiring a controlled environment during long-term studies.

A review of hypersomolar hyperglycemic nonketotic dehydration (HHND): etiology, pathophysiology and prevention during intravenous hyperalimentation

The records of 200 patients, nutritionally supported by synthetic means, were reviewed for evidence of clinical hyperosmolar hyperglycemic nonketotic dehydration (HHND). There was a 3% incidence of morbidity, with a single mortality. Laboratory values demonstrated a positive correlation between persistent glucosuria and HHND. The pathophysiology of HHND demonstrated a relative insulin lack with sufficient insulin to prevent lipolysis, but insufficient to prevent hyperglycemia, glucosuria and osmotic diuresis. The mechanism and management of the pseudodiabetes of stress is reviewed. It is concluded that HHND is an avoidable iatrogenic morbidity. Prevention of osmotic diuresis secondary to glucosuria and, therefore, prevention of HHND is achieved by providing exogenous insulin sufficient to prevent glucosuria.