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Resting metabolic rate in chronic renal failure
U Kuhlmann1, M Schwickardi, R Trebst
1Center for Internal Medicine, Clinic of Nephrology, Philipps-University of Marburg, Germany.
Objective:
A decrease in resting metabolic rate (RMR) in patients with chronic renal failure was assumed to occur because of the decreasing oxygen consumption of the kidneys, which in healthy subjects, accounts for 7.2% of RMR. Contrary to this assumption, RMR per body weight in end-stage renal disease was increased.
Design And Methods:
To test the impact of chronic renal failure on the RMR, direct bedside calorimetry was performed on 51 outpatients (age, 53.2 +/- 13.9 y; creatinine clearance, 6.9 to 52 mL/min). Twenty two of 51 patients were examined repeatedly (at the start of the study, after 3 months, and after 6 months) during declining kidney function.
Results:
In the total group, RMR per body weight (RMR/BW) was 100.0 +/- 4.96 kJ/kg/day and RMR per body surface area (RMR/BSA) was 4.582 +/- 0.181 kJ/min/1.73m(2). RMR/BW and RMR/BSA correlated significantly with creatinine clearance (n = 51, r = -.763, P <.001; n = 51, r = -.557, P <.001). In the follow-up group, creatinine clearance decreased from 27.5 +/- 9.5 mL/min initially, to 19.4 +/- 6.25 mL/min at 3 months, to 13.0 +/- 3.8 mL/min at 6 months (P <.001), while RMR/BW and RMR/BSA increased from 98.28 +/- 6.3, to 101.64 +/- 5.46, to 105.42 +/- 6.3 kJ/kg BW/d (P <.005), respectively, and 4.41 +/- 0.126, to 4.578 +/- 0.168, to 4.704 +/- 0.168 kJ/min/1.73 m(2) (P <.05), respectively.
Conclusion:
Taking into account the reduced oxygen consumption of the shrinking kidneys, the normal RMR suggests an increased energy expenditure per body cell mass. The raising RMR in deteriorating excretory kidney function reflects the increasing energy expenditure in progressive chronic renal failure.