Acid–base status of critically ill patients with acute renal failure: analysis based on Stewart–Figge methodology

Table 2 Acid–base variables in acute renal failure patients and two control groups

Variable	Acute renal failure group	Matched controls	Intensive care unit controls	P value (analysis of variance)
pH,*	7.30 ± 0.13	7.38 ± 0.12	7.43 ± 0.08	< 0.0001
pCO₂ (mmHg)	37.9 ± 8.5	40.5 ± 11.3	42.3 ± 8.5	0.073
Bicarbonate (mmol/l),*	18.9 ± 5.5	23.5 ± 6.1	27.5 ± 5.2	< 0.0001
Base excess (mmol/l),*	-7.5 ± 7.2	-1.5 ± 7.2	2.9 ± 5.3	< 0.0001
Sodium (mmol/l)*	139.6 ± 6.2	133.5 ± 5.4	140.8 ± 4.5	< 0.0001
Potassium (mmol/l)**	4.7 ± 0.8	4.3 ± 0.9	4.1 ± 0.4	0.0003
Chloride (mmol/l)*	102.5 ± 7.8	95.5 ± 5.5	102.0 ± 4.6	< 0.0001
Magnesium (mmol/l)^a	1.05 ± 0.40	0.88 ± 0.34	0.94 ± 0.28	0.065
Calcium (mmol/l)^b,**	1.10 ± 0.12	1.12 ± 0.09	1.17 ± 0.09	0.0009
Phosphate (mmol/l),*	2.08 ± 0.92	1.30 ± 0.64	1.13 ± 0.50	< 0.0001
Albumin (g/l)	22.6 ± 6.3	25.2 ± 5.9	23.9 ± 5.8	< 0.0001
Lactate (mmol/l)**	3.72 ± 3.45	3.50 ± 3.77	1.92 ± 1.52	0.004
Anion gap (mEq/l),*	22.9 ± 7.6	18.8 ± 6.5	15.4 ± 3.7	< 0.0001
Apparent strong ion difference (mEq/l)**	42.4 ± 4.4	42.8 ± 4.4	45.2 ± 3.7	< 0.0001
Effective strong ion difference (mEq/l),*	29.0 ± 5.1	33.4 ± 6.3	36.9 ± 5.5	< 0.0001
Strong ion gap (mEq/l),*	13.4 ± 5.5	9.5 ± 4.4	8.3 ± 3.6	< 0.0001

All data presented as mean ± standard deviation. ^aMeasured as total magnesium. ^bMeasured as ionized calcium. *Significant difference between the acute renal failure group and matched controls. **Significant difference between the acute renal failure group and intensive care unit controls.

ISSN: 1364-8535