The effects of malnutrition on the surgical patient are well characterized in the literature but are often overlooked in the clinical arena. Between 30% and 50% of hospitalized patients are malnourished. Protein-calorie malnutrition produces a reduction in lean muscle mass, alterations in respiratory mechanics, impaired immune function, and intestinal atrophy. These changes result in diminished wound healing, predisposition to infection, and increased postoperative morbidity. Although most healthy individuals can tolerate up to 7 days of starvation (with adequate glucose and fluid replacement), those subjected to major trauma, the physiologic stress of surgery, sepsis, or cancer-related cachexia require earlier nutritional intervention. Methods to identify those at greatest need for supplemental nutrition and to adequately address their needs are discussed in this chapter.
Nutrition screening is the process of identifying patients who are either malnourished or at risk for developing malnutrition. Major trauma and surgical stress alter the intake and absorption of nutrients, as well as their utilization and storage by the body. In select patients (eg, those with severe malnutrition as determined below), preoperative nutritional support has been shown to significantly reduce perioperative morbidity and mortality. Although most patients do not require this level of support, nutrition screening is imperative to identify the patient at high risk for malnutrition or its sequelae. A comprehensive nutritional assessment incorporates the initial history, physical examination, and laboratory testing to provide a snapshot of the patient’s recent nutritional health.
History & Physical Examination
The history and physical examination are the foundation of nutritional assessment. A complete medical history is essential to identify factors that predispose the patient to alterations in nutritional status (Table 10–1). Chronic illnesses such as alcoholism are commonly associated with protein-calorie malnutrition as well as vitamin and mineral deficiencies. Previous operative procedures such as gastrectomy or ileal resection may predispose to generalized malabsorption or isolated deficiency of iron, vitamin B12, or folate. In most cases, the possibility of malnutrition is suggested by the underlying disease or by a history of recent weight loss. Patients with renal failure who require hemodialysis lose amino acids, vitamins, trace elements, and carnitine in the dialysate. Cirrhotics often suffer from whole-body sodium overload despite being hyponatremic, and they are typically protein-deficient. Patients with inflammatory bowel disease, particularly those with ileal involvement, may develop protein deficiency due to a combination of poor intake, chronic diarrhea, and treatment with corticosteroids. Furthermore, alterations in the enterohepatic circulation of bile salts lead to fat, vitamin, calcium, magnesium, and trace element deficiencies. Approximately 30% of patients with cancer have protein, calorie, and vitamin deficiencies due either to the underlying disease or to antimetabolite chemotherapy (eg, methotrexate). Patients infected with HIV are frequently malnourished and have protein, trace metal (selenium and zinc), mineral, and vitamin deficiencies.
Table 10–1.Nutritional assessment.