Diuretic Resistance  in ICU

What do I do if I encounter what appears to be diuretic resistance in ICU?

1. Make sure that the patient’s intravascular volume and renal perfusion pressure are adequate.

2. Administer higher doses of diuretic. The quantity of diuretic agent reaching the mTAL is decreased in CHF and renal insufficiency. When GFR is very low, only 20% of a dose of furosemide and 10% of bumetanide reaches the urine.; Doses should be increased accordingly (i.e., furosemide from 20 to 100 mg; bumetanide from 0.5 to 5 mg).

3. Consider continuous diuretic infusion. Continuous furosemide infusion achieves effective diuresis in patients with CHF at blood concentrations considerably below those of bolus doses. After a small loading dose (10-20 mg), an infusion of between 2.5 and 10 mg/hr is administered.

The pharmacodynamic explanation is that the duration of delivery of diuretic into the urine is the critical determinant of diuretic response. In comparison with bolus doses, continuous infusion provides a more consistent and sustained diuresis, avoids high peak doses, which induce toxic side effects, decreases the potential for rebound sodium retention, and facilitates titration to effect however there is also the risk of excessive diuresis with its attendant consequences of hypovolemia, hypokalemia, hypomagnesemia, and supraventricular arrhythmias.

4. Segmental nephron blockade. The combination of low doses of a loop diuretic and a thiazide is more effective than high doses of either agent used alone. As described earlier, inhibition of sodium absorption at both the mTAL and at the distal tubule effectively blocks two segments of the nephron and induces a synergistic diuretic response. Metolazone (2.5-5.0 mg po), a thiazide-like diuretic, together with intravenous furosemide (40-80 mg) or bumetanide (2.5-5 mg), is a good choice.

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