Monitors in Nutrition Support

Abstract

Monitoring the effects of nutrition support is essential for patient safety and responsible clinical practice. The nutrition support practitioner must be knowledgeable about numerous types of monitors, including those of energy metabolism, fluid, electrolyte and mineral balance, disease modulation, physiologic complications, symptom tolerance, psychological health, and overall well-being. Nutrition support monitoring is complex and requires specialized knowledge and supervised experiential training. The role of the nutrition support specialist is substantiated by the need to (1) understand the purpose and implications of the many clinical monitors involved in administering this important therapy; and (2) formulate specific recommendations according to these indices that often need daily adjustment for patients in a wide range of settings from home care to intensive care. In this issue of Nutrition in Clinical Practice ,w e examine various monitors used in nutrition support. It is evident from these manuscripts that there is a range in the strength of evidence supporting clinical monitors. Furthermore, some indices, as described by Marik, 1 are quantitative and obtained by serum testing. Weckworth 2 reminds us that other monitors rely on the expert analysis of subjective symptoms by the nutrition support clinician. Evaluating monitors in nutrition support involves the following advanced processes: interpretation of technological data, assessment of multiple sources of patient information, sound judgment, and integration of scientific principles. Parekh and Steiger’s review 3 of the pivotal paper by Studley 4 shows the longstanding emphasis on using clinical evidence in nutrition support practice. Studley made the seminal determination that preoperative weight loss is associated with postoperative outcome. Beyond historical interest, the clinical monitor of weight loss set forth in this 1936 article continues to be relevant today, even with the advent of more complicated predictive indices. Given this context, the interest in a more sophisticated analysis of body composition, such as via bioelectrical impedance, becomes clear and is examined by Buchholz et al. 5 Bioelectrical impedance instruments enable estimates of total body water, fat free mass, and percent fat mass; they offer numerous advantages in terms of safety, cost, and operation. The management of various patient groups, such as renal failure patients and critically ill elderly, would potentially benefit from better estimates of body composition. The review by Buchholz et al 5 illustrates the challenge and complexity of integrating “high-tech” monitors into routine practice. The enthusiastic development of the instruments and modeling techniques involved in bioelectrical impedance measurements seems to have outpaced their clinical validity for patient use. We wait with optimism to see whether application of bioelectrical impedance will be part of standard practice. Nutrition assessment, whether to identify candidates for nutrition support or for ongoing evaluation of the effectiveness of therapy, is fundamental to nutrition support practice. Standards requiring timely nutrition assessment and planning support