Creatinine index in acute renal failure: an outcome and nutritional indicator

Normalized creatinine production (creatinine index [CI]) has been shown to reflect protein nutritional status and outcome in chronically hemodialysis patients, but such has not yet been established in acute renal failure (ARF). We therefore investigated CI as an indicative parameter of protein denutrition and outcome in ARF requiring extrarenal replacement therapy (ERRT).

Methods

Twenty-four patients (APACHE II score 29.6 ± 5.7) with ARF treated by intermittent hemodialysis or continuous venove-nous hemofiltration (CVVHF) have been studied along 7 days from the first ERRT session (D₁–D₇). Weight, diuresis, BUN, creatinemia, urinary urea nitrogen and creatinine were collected daily, before and after each ERRT. During CVVHF, fractional ultrafiltrant urea nitrogen and creatinine collections were also collected. Normalized protein catabolism rate (nPCR) and nitrogen supply were estimated daily and an average of 7 days (D₁–D₇) was calculated. CI was calculated at D₁ and D₇ according to the formula CI (mg/kg per 24 hours) = {[(Cb_T2 - Cb_T1) × weight × 0.6] / T + (Cu × Vu) / T + (Cuf × Vuf) / T} × 0.113 × 1440 / weight + [(Cb_T1 + Cb_T2) / 2] × 0.0429, where C = creatinine in blood (b), in urine (u) and in ultrafiltrant (uf), V = volume of urine (u) and ultrafiltrant (uf), and T = time in minutes from T1 to T2. The CI changing rate from D₁ to D₇ was calculated according to cCI = (D₇CI - D₁CI) × 100 / D₁CI. From ICU survival, two groups were individualized and compared.

Results

The mean CI was 28.3 ± 9.6 at D₁ and 22.2 ± 9.4 mg/kg per day at D₇ (P < 0.05); the mean cCI was -21.5 ± 26.6%. The average nPCR was 1.87 ± 0.77 g/kg per day, whereas the average nitrogen supply was 0.14 ± 0.06 g/kg per day. ICU survival rate was 50%.

No correlation was found between nPCR and CI, nor between nPCR and nitrogen supply.

Conclusion

We conclude that CI before and 7 days after initiation of ERRT is a predictive factor of outcome in ARF, and that a dramatic decrease of CI after the first week of ERRT worsens significantly the outcome. These results would also suggest that, in ARF patients, CI and CI changes are better indicative of protein denutri-tion than nPCR.

Table 1

Correction (10 March 2003)

The original published version of this abstract (as shown above) included incorrect data in the 5th sentence of the Methods section. The sentence should read as follows:

CI was calculated at D₁ and D₇ according to the formula CI (mg/kg per 24 hours) = {[(Cb_T2 - Cb_T1) × weight × 0.6] / T + (Cu × Vu) / T + (Cuf × Vuf) / T} × 0.113 × 1440 / weight + [(Cb_T1 + Cb_T2) / 2] × 0.00429, where C = creatinine in blood (b), in urine (u) and in ultrafiltrant (uf), V = volume of urine (u) and ultrafiltrant (uf), and T = time in minutes from T1 to T2.