Estimation of protein requirements according to nitrogen balance for older hospitalized adults with pressure ulcers according to wound severity in Japan

Objectives To estimate protein requirements in older hospitalized adults with pressure ulcers (PrU) according to systemic conditions and wound severity. Design Secondary nitrogen balance study over 3 days. Setting Long-term care facility. Participants Twenty-eight older adults with PrU using a urinary catheter. Measurements Nitrogen balance over 3 days was evaluated from habitual nitrogen intake measured using a food weighing record and nitrogen excretion from urine, feces and wound exudate. Nitrogen intake required to maintain nitrogen equilibrium was estimated as an average protein requirement using a linear mixed model. Results Nitrogen intake at nitrogen equilibrium was 0.151 gN/kg per day (95% confidence interval = 0.127-0.175 gN/kg per day) for all participants. The amount of protein loss from wound exudate contributed little to total nitrogen excretion. A Charlson comorbidity index of 4 or greater (the median value) was related to lower nitrogen intake at nitrogen equilibrium (P =.005). Severe PrU with heavy exudate amounts and measured wound areas of 7.9 cm² or greater (the median value) were related to higher nitrogen intake at nitrogen equilibrium in individuals with a Charlson comorbidity index of 3 or less (both P =.04). Larger wound area (correlation coefficient (r) = 0.55, P =.003) and heavier exudate volume (r = 0.53, P =.004) were associated with muscle protein hypercatabolism measured according to 3-methylhistidine/ creatinine ratio. Conclusion The average protein requirement is 0.95 g/kg per day for older hospitalized Japanese adults with PrU, but protein requirements depend on an individual's condition and wound severity and range from 0.75 to 1.30 g/kg per day. Severe PrU can require higher protein intakes because of muscle protein hypercatabolism rather than direct loss of protein from wound exudate.