Investigations

Calculate the creatinine clearance ^d

Cl _Cr Creatinine clearance; Cr_s serum creatinine

If the patient is obese, use an estimate of the patient’s ideal body weight to calculate creatinine clearance.

• Ideal body weight (kg) for males: 52 kg + 0.72 kg for every cm above 154 cm in height

• Ideal body weight (kg) for females: 49 kg + 0.64 kg for every cm above 154 cm in height.

Note: ^d

• Normal creatinine clearance is around 100 mL/min
• This formula is derived for use in steady state (not the case in ARF), but can provide an idea of the severity of the problem (e.g. for drug dose adjustments).
• If the creatinine is rising, true clearance will be lower (often much lower) than that calculated.
• If oligo-anuric, best estimate of true creatinine clearance is less than 10 ml/min - adjust drugs accordingly.