Numerous studies suggest that malnutrition in the perioperative period is associated with poor postoperative outcomes, including increased rates of infection, poor wound healing and anastomotic integrity, increased intensive care unit and hospital length of stay, increased need for mechanical ventilation, and increased mortality after transplant and major intra-abdominal or cardiothoracic surgery.
A lack of standardized definitions and indices has hampered attempts to study the epidemiology and pathophysiology of malnutrition. Nevertheless, the problem appears to be widespread in patients presenting for surgery. In addition, many patients will acquire protein-energy malnutrition (PEM) during hospitalization.
Malnutrition is a complex metabolic disorder, involving inflammatory and neurohumoral mediators, that affects virtually every organ system.
The metabolic and physiologic changes accompanying malnutrition can significantly alter response to anesthetics.
Decreased total circulating albumin has wide implications for drug administration and volume of distribution.
As a result of decreased microsomal enzyme activity and altered cytochrome P450/nicotinamide adenine dinucleotide phosphate—dependent transport mechanisms, protein deficiency may reduce drug metabolism. Decreased transformation of compounds that are hepatically detoxified may lead to pathologic responses that require dosage alteration.
Uncertainty surrounds the optimal dose, route, and timing of perioperative nutritional support, but there is increasing evidence that reversal of perioperative malnutrition, especially when severe, can reduce complications and improve outcomes.
Recent interest has focused on the use of immunonutrient supplementation, preoperative oral carbohydrate loading, and selective elimination of preoperative fasting in an effort to ameliorate postoperative catabolism and insulin resistance.
Accurate estimation of the presence and severity of PEM remains problematic for the anesthesiologist, whose evaluation of the patient is often brief. The most useful tool for assessing a patient's nutritional status is a well-performed history and physical examination.
Anesthesiologists have an important role to play in perioperative nutrition and should ensure that patients presenting for surgery are in the best possible condition to tolerate the surgical stress and postoperative recovery period. In hospitalized patients, efforts should be made to continue enteral or parenteral nutrition when appropriate. Finally, anesthesiologists should be at the forefront of clinical and basic science research on perioperative nutrition.
In recent years, anesthesiologists, surgeons, and intensivists have gained experience caring for older, more debilitated patients. Surgical intervention is now routinely offered to patients who would once have been considered "too sick for the operating room." Many of these patients suffer from, or will develop, malnutrition during the course of their illness. In order to provide optimal perioperative care, today's anesthesiologist must understand the effects of malnutrition and disease-altered metabolism on organ function, drug metabolism, and patient outcome. This chapter reviews (1) definitions of malnutrition and its prevalence in surgical patients, (2) clinical assessment and diagnosis of malnutrition, (3) effects of malnutrition on organ system function and drug metabolism, (4) the consequences of therapeutic nutrition, and (5) the association between malnutrition (or its reversal) and patient outcomes.
Inadequate intake of macronutrients (carbohydrate, protein, fat) leading to a reduction in lean body cell mass is referred to as protein-energy malnutrition (PEM). ...