What are the Effects of N-acetylcysteine, Theophylline, Other Agents on Preventing Contrast-induced Nephropathy
Background: Contrast-induced nephropathy is the third-most common cause of new acute renal failure in hospitalized patients, occurring in up to 25% of patients with renal impairment, diabetes, heart failure, advanced age, or concurrent use of nephrotoxic drugs. Clinicians use different agents to reduce the risk, including intravenous hydration, N-acetylcysteine, theophylline, fenoldopam, dopamine, furosemide, mannitol, and bicarbonate.
Study design: Meta-analysis of randomized controlled trials.
Setting: 41 studies involving 6,379 patients, published internationally between 1994 and 2006.
Synopsis: All but one study evaluated patients undergoing cardiac catheterization, and 34 trials evaluated patients with impaired renal function. N-acetylcysteine significantly reduced the risk of contrast-induced nephropathy more than saline hydration alone (risk ratio [RR]=0.62, 95% CI 0.44 to 0.88). Theophylline may have renoprotective effects but the findings were not statistically significant (RR=0.49, 95% CI 0.23 to 1.06). Ascorbic acid and bicarbonate significantly reduced nephropathy, though only one study was found for each. The other agents evaluated did not significantly reduce risk. Furosemide increased the risk (RR=3.27, 95% CI 1.48 to 7.26).
Bottom line: N-acetylcycteine is an effective agent for prevention of contrast-induced nephropathy, and it has the added benefits of low cost, few side effects, and rare drug interactions.
Citation: Kelly AM, Dwamena B, Cronin P, Bernstein SJ, Carlos RC. Meta-analysis: effectiveness of drugs for preventing contrast-induced nephropathy. Ann Intern Med. 2008;148(4):284-294.
Compared With Norepinephrine, Does Vasopressin Infusion Improve Mortality in Septic Shock Patients?
Background: Vasopressin is commonly used to support blood pressure in patients with septic shock. It has been shown to restore vascular tone, maintain blood pressure, and decrease catecholamine requirements, but its effect on mortality is uncertain.
Study design: Randomized, double-blind trial.
Setting: 27 centers in Canada, Australia, and the United States.
Synopsis: Patients with septic shock who required at least 5 mcg/min of norepinephrine were randomized to receive either low-dose vasopressin infusion (0.01 to 0.03 U/min) or norepinephrine (5 to 15 mcg/min). There was no significant difference in mortality at 28 days (35.4% for vasopressin vs. 39.3% for norepinephrine, p=0.26) or at 90 days (43.9% vs. 49.6%, p=0.11). The vasopressin group had lower heart rate and norepinephrine requirements. There were no significant differences in the frequency of adverse events.
However, since mean blood pressure at baseline was 72-73 mmHg, study patients did not necessarily have catecholamine unresponsive shock. Also, the mean time from meeting criteria for study entry to infusion of the drug was 12 hours, longer than the six-hour time period identified as important in studies of early goal-directed therapy. This may have limited the effectiveness of vasopressin infusion.
Bottom line: Low-dose vasopressin as compared with norepinephrine did not improve mortality in patients with septic shock.
Citation: Russell JA, Walley KR, Singer J, et al. Vasopressin versus norepinephrine infusion in patients with septic shock. N Engl J Med. 2008;358(9):877-887.
How Much do Hospitalized Patients Want to Participate in Decisions on Therapies of Varying Risk, Benefit?
Background: Obtaining informed consent is required for invasive procedures, but most non-invasive medical treatments are performed without discussing the risks, benefits, and alternatives with patients.
Study design: Questionnaire with four scenarios.
Setting: Medical wards in a Connecticut hospital.
Synopsis: Among the 210 patients studied, about one-fourth wanted physicians to obtain their permission “no matter what” even for mundane therapies like potassium supplementation (24%) or diuretic administration (28%). When presented with a higher risk scenario, such as thrombolysis with a greater than 20% chance of hemorrhage, 40.8% of patients definitely wanted to participate in decision-making.