Hematocrit and Perioperative Mortality
Wu WC, Schifftner TL, Henderson WG, et al. Preoperative hematocrit levels and postoperative outcomes in older patients undergoing noncardiac surgery. JAMA. 2007 Jun 13;297(22):2481-2488.
Several studies have outlined the risk of preoperative anemia prior to noncardiac surgery in elderly patients. These studies have not linked anemia to risk of death unless cardiac disease is present.
Anemia management remains a challenge for many hospitals and is the most important predictor of the need for blood transfusion. Transfusion increases morbidity and mortality in the perioperative setting. At the same time, little is known about the risks of polycythemia in this setting.
This retrospective cohort study used the Veterans’ Affairs National Surgical Quality Improvement Program database of 310,311 veterans 65 or older from 132 VA hospitals. It explores the relationship between abnormal levels of hematocrit and adverse events among elderly surgical patients.
The data suggest an incremental relationship between positive and negative deviation of hematocrit levels with 30-day postoperative mortality in patients 65 and older. Specifically, the study found a 1.6% increase (95% confidence interval, 1.1%-2.2%) in 30-day mortality for every percentage point of increase or decrease in hematocrit from the normal range.
Because this is an observational study of anemia and adverse events, no causal relationship can be established from this data. Hospitalists involved in perioperative care should be careful about drawing conclusions from this study alone and should not necessarily plan interventions to treat abnormal levels of hematocrit without carefully considering the risks and benefits of intervention.
Prognostic Utility of Pre-operative BNP
Feringa HH, Schouten O, Dunkelgrun M, et al. Plasma N-terminal pro-B-type natriuretic peptide as long term prognostic marker after major vascular surgery. Heart. 2007 Feb;93(2):226-231.
Traditional stratification of patients at high risk for cardiac complications and undergoing noncardiac surgery has included clinical risk index scoring and pre-operative stress testing. It is unclear if cardiac biomarkers can be used in conjunction with these measures to improve the identification of patients at risk.
Feringa and colleagues addressed this question by looking prospectively at 335 patients undergoing major vascular surgery over a two-year period. The mean age of patients was 62.2 years; 46% of patients underwent abdominal aortic aneurysm repair, and the remaining 54% received lower-extremity revascularization.
Patients had cardiac risk scores calculated based on the Revised Cardiac Risk Index (RCRI), and all patients had dobutamine stress echocardiogram (DSE) to assess for stress-induced ischemia. N-terminal pro-B-type natriuretic peptide (BNP) was measured at a mean of 12 days before surgery. Patients were followed for all-cause mortality and post-op death for a mean follow-up time of 14 months.
The authors found that NT-pro BNP performed better than the RCRI and DSE for predicting six-month mortality and cardiac events. An NT-pro BNP cut-off level of 319 ng/l was identified as optimal for predicting six-month mortality and cardiac events with 69% sensitivity and 70% specificity for mortality. Patients with levels 319 mg/l had a lower survival during the follow up period (p<0.0001).
Based on this prospective study, it appears that a preoperative elevated NT-Pro BNP is associated with long-term mortality and morbidity and could be used as an additional risk-stratification tool along with clinical risk scoring and stress testing.
Utility of Combination Medications in COPD
Aaron SD, Vandemheen KL, Fergusson D, et al. Tiotropium in combination with placebo, salmeterol, or fluticasone-salmeterol for treatment of chronic obstructive pulmonary disease. Ann Intern Med. 2007 Feb 19;146:545-555