Adverse outcome analyses of observational data: assessing cardiovascular risk in HIV disease.

Clinical decisions are ideally based on randomized trials but must often rely on observational data analyses, which are less straightforward and more influenced by methodology. The authors, from a series of expert roundtables convened by the Forum for Collaborative HIV Research on the use of observational studies to assess cardiovascular disease risk in human immunodeficiency virus infection, recommend that clinicians who review or interpret epidemiological publications consider 7 key statistical issues: (1) clear explanation of confounding and adjustment; (2) handling and impact of missing data; (3) consistency and clinical relevance of outcome measurements and covariate risk factors; (4) multivariate modeling techniques including time-dependent variables; (5) how multiple testing is addressed; (6) distinction between statistical and clinical significance; and (7) need for confirmation from independent databases. Recommendations to permit better understanding of potential methodological limitations include both responsible public access to de-identified source data, where permitted, and exploration of novel statistical methods.

Neurologic prognosis and withdrawal of life support after resuscitation from cardiac arrest.

OBJECTIVE: To study the impact of neurologic prognostication on the decision to withdraw life-sustaining therapies (LST) in comatose patients resuscitated after cardiac arrest. METHODS: The authors prospectively studied a consecutive series of post-resuscitation comatose patients referred for neurologic prognostication at a single center for 4 years. For most patients, neurologic prognostication was not sought due to early death or rapid return to consciousness. Prognostication was based on Glasgow Coma Score (GCS) and Brainstem Reflex Score (BRS), with EEG and cortical evoked potentials (CEP), which were graded as benign, uncertain, and malignant. The outcomes were as follows: survivors (Group S), brain or cardiac death (Group D), and death from withdrawal of life sustaining therapy (Group W). In Group W, the time interval to withdrawal of LST was analyzed by EEG and CEP grades. RESULTS: Of 58 patients studied, 10 were in Group S, 8 in Group D, and 40 in Group W. Initial median GCS and BRS was similar for all groups with significant improvement noted in Group S, but not in Group D or Group W. In Group W, CEP grade correlated with the median duration of continued therapy before a decision to withdraw LST: 7 days for benign CEP, 2 days for uncertain CEP, and 1 day for malignant CEP, p = 0.0004. CONCLUSION: In patients with poor neurologic recovery early after resuscitation from cardiac arrest, physicians appear to use the cortical evoked potential grade to estimate prognosis. Cortical evoked potential grade correlated with the waiting time until life sustaining therapies were withdrawn after no improvement in neurologic examination was seen.

Magnesium use in the treatment of acute myocardial infarction in the United States (observations from the Second National Registry of Myocardial Infarction).

The use of magnesium in patients with acute myocardial infarction (AMI) is debated, largely as a result of conflicting data from randomized controlled trials. This study evaluated the use and impact on mortality of intravenous magnesium in the treatment of patients with AMI in the United States based on data from the Second National Registry of Myocardial Infarction. Only 5.1% of 173,728 patients from 1,326 hospitals received intravenous magnesium within the first 24 hours after an AMI, and this was more common in the 59,798 patients who received thrombolytic therapy or who underwent primary percutaneous transluminal coronary angioplasty (PTCA) or coronary bypass grafting (CABG) than in the 113,930 patients who did not receive any reperfusion therapy (8.5% vs 3.4%, p <0.01). Magnesium use was associated with younger age, Q-wave AMI, congestive heart failure on admission, thrombolytic therapy, primary PTCA or CABG, ventricular tachycardia or ventricular fibrillation, and beta blocker or lidocaine use in the first 24 hours (all odds ratio > 1.2, p <0.001). Magnesium use was associated with increased mortality (odds ratio 1.25, 95% confidence interval 1.12 to 1.34) and with a higher mortality in patients without initial reperfusion therapy (20.2% vs 13.2%, p <0.0001) or who underwent primary PTCA or CABG (10.2% vs 7.3%, p = 0.002), but not in patients who received thrombolytic therapy (6.2% vs 5.9%, p = NS). Thus, magnesium is used infrequently in the treatment of AMI and may be associated with worse outcome.