Comparison of Body Weights Via Visual Estimation, Anthropometric Calculation, and Actual Measured in Critically Ill Patients

Overview

Rapid and accurate determination of body weight in adult intensive care patients is very important for both calculating target tidal volume during invasive mechanical ventilation support and dose dependent drug administration. In this patient group, measuring actual body weight with a calibrated scale by standing the patient up is often impossible due to acute illness. Instead, estimated body weight determined by health care personnel or estimated body weights calculated according to anthropometric measurements are used. These calculations have some limitations in showing actual body weight, and there is some controversial information in current literature regarding their validity in critically ill patients. There is newly developed patient transfer scale called Marsden M-999® manufactured by Marsden Weighing Machine Group Ltd, which has the advantage of being used in patients who are unable to stand up, in rapidly and accurately measuring the current body weight in critically ill patients. This study aimed to evaluate the validity of these methods by comparing the body weights calculated by visual estimation and various anthropometric methods in critically ill Turkish patients with the actual weight measured by the mentioned scale.

In adult medicine, determining the patient's body weight by visual estimation performed by healthcare providers (nurses and doctors) is common for critically ill patients who cannot speak or stand due to acute illnesses such as loss of consciousness, circulatory shock, or acute respiratory failure. This practice often leads to the administration of the same dose of medication to many patients whose body weight may vary between 50 to 100 kilograms (kg). In cases where rapid diagnosis and treatment are crucial due to acute illness, the accurate and effective administration of dose-dependent drugs such as antibiotics, anticoagulants, vasopressors, sedatives, and analgesics is essential for treatment success. Although the average error percentage of 10-20% in estimated body weight by visual estimation may seem negligible in emergencies, it can lead to increased toxicity and costs in recombinant factor replacements, anticoagulants with a narrow therapeutic range, and various imported antibiotics. Additionally, the high error rate in estimating height by visual estimation poses a risk of causing ventilator-induced lung injury (VILI) during invasive mechanical ventilation support by inducing alveolar overdistension. Various calculation methods have been reported for estimating body weight based on anthropometric measurements. One such method is weight calculation based on the upper mid-arm circumference (UMAC), which has been reported as the most correlated calculation for actual body weight in the adult age group in studies using National Health and Nutrition Examination Survey (NHANES) data in the United States (U.S.). Another commonly used method is formulas that calculate ideal body weight based on the patient's height. This is especially crucial in critically ill patients during invasive mechanical ventilation support for acute respiratory failure. The calculation of ideal body weight using charts based on half-span or knee height can be applied in cases where patients cannot stand due to critical illness. Many anthropometric measurements mentioned here have been conducted in different societies. They may vary according to ethnic communities, emphasizing the potential differences in body composition, such as fat and muscle mass distribution, among different ethnic groups. Considering the critical illness in the Turkish population, there is currently no detailed publication in the literature regarding the usability of estimated body weights calculated based on anthropometric measurements. Moreover, the fact that many anthropometric measurements are derived from population screening data in healthy individuals causes their application in clinical practice challenging. Validity of anthropometric measurements that apply to critically ill patients, where patients cannot stand, appropriate positions for anthropometric measurements cannot be provided, and body distributions in limbs where anthropometric measurements are derived may differ due to peripheral edema, is, therefore, crucial. In many studies using anthropometric measurements for weight calculation, the actual body weights of patients were measured using a calibrated scale. Given that critically ill patients often cannot be lifted due to acute illness, special devices or equipments are needed to reliably determine actual body weights in the supine position in this patient group. Currently, used bed scales, wall-mounted levers, or special devices that allow the patient and bed to be weighed together are not widely used due to high costs and difficulties associated with patient transfer from bed to bed, such as the need for the patient to be hemodynamically stable, the need for multiple personnel during patient transfer, adherence to infection prevention rules, and the time-consuming nature of measurements depending on the device used. The recently developed patient transfer scale, Marsden M-999®, which has advantages for patients who cannot stand, suggests that it could be used to calculate actual weight rapidly and accurately in critically ill patients. There is no publication currently in the literature about the routine use of the mentioned patient transfer scale in critically ill settings. However, its ease of use in measuring patient body weight in the supine position while transitioning from a stretcher to an intensive care bed is a significant advantage. Considering that the patient transfer scale cannot be provided to every intensive care unit due to its cost; it was aimed to determine the most valid estimated body weight calculation method in the critically ill Turkish patients according to anthropometric measurements in this study.