Estimation of Protein Requirements According to Nitrogen Balance for Older Hospitalized Adults with Pressure Ulcers According to Wound Severity in Japan


Address correspondence to Shinji Iizaka, Department of Gerontological Nursing/Wound Care Management, Graduate School of Medicine, The University of Tokyo, Faculty of Medicine, Bldg. No.5–308, 7–3-1 Hongo, Bunkyo-ku, Tokyo 113–0033, Japan. E-mail:



To estimate protein requirements in older hospitalized adults with pressure ulcers (PrU) according to systemic conditions and wound severity.


Secondary nitrogen balance study over 3 days.


Long-term care facility.


Twenty-eight older adults with PrU using a urinary catheter.


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.


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 (= .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 = .04). Larger wound area (correlation coefficient (r) = 0.55, = .003) and heavier exudate volume (r = 0.53, = .004) were associated with muscle protein hypercatabolism measured according to 3-methylhistidine/creatinine ratio.


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.