In This Edition
Literature At A Glance
A guide to this month’s studies
- Atelectasis and fever
- Heparin dosing frequency for VTE prophylaxis
- Perioperative cardiac risk calculator
- Diagnosing subarachnoid hemorrhage without an LP
- Model to predict risk of bleeding on warfarin
- Risk of death with tiotropium use in COPD
- BNP to predict perioperative mortality
- Beta-blockers and COPD
No Association Found between Atelectasis and Early Postopera-tive Fever
Clinical question: Is atelectasis really a major cause of early (up to 48 hours) postoperative fever (EPF)?
Background: Both fever and atelectasis are common findings in the postoperative period. EPF is believed to be noninfectious, and many textbooks consider atelectasis to be the most common cause. However, this association is controversial with no clear evidence.
Study design: Systematic review of prospective studies evaluating atelectasis and postoperative fever using PubMed and Scopus databases.
Setting: Postoperative patients (predominantly cardiac, maxillofacial, and abdominal surgeries). Lung surgery patients were excluded.
Synopsis: Eight prospective studies (four interventional and four observational) with 998 patients were included for review. All studies diagnosed atelectasis based on chest imaging but only three studies used the conventional definition of ≥38°C for fever. Seven studies individually reported no association between atelectasis and EPF.
Only five studies had eligible data for pooling and analysis. EPF was found to be a very weak indicator (diagnostic OR 1.4; 95% CI 0.92-2.12) of atelectasis. EPF also fared poorly for ruling out (sensitivity 13% to 47%) or ruling in (specificity 41% to 87%) the diagnosis of atelectasis with similarly poor positive and negative predictive values.
The results of this study, however, should be interpreted with caution. It was not a formal meta-analysis, due to the heterogeneity of the studies included with regard to the definition of fever, time points of imaging, and the variation of end points.
Bottom line: Since there is no clinical evidence to prove an association between atelectasis and fever, it is presumed that atelectasis may not be a cause of EPF.
Citation: Mavros MN, Velmahos GC, Falagas ME. Atelectasis as a cause of postoperative fever: where is the clinical evidence? Chest. 2011;140:418-424.
Unfractionated Heparin Can be Given Either BID or TID for Throm-boprophylaxis
Clinical question: Which is the best dosing frequency of unfractionated heparin (UFH) in preventing venous thromboembolism?
Background: Low-dose UFH is commonly used in hospitals for pharmacologic prophylaxis against venous thromboembolism. However, the risks and benefits of BID vs. TID dosing are not clear.
Study design: Mixed-treatment comparison (MTC) meta-analysis of RCTs.
Setting: RCTs on thromboprophylaxis regimens, selected from two previous systematic reviews and an updated literature search.
Synopsis: Included in the analysis were 27,667 patients from 16 RCTs comparing three prophylactic regimens (UFH BID, UFH TID, or low-molecular-weight heparin) with each other or with controls. Stroke and some myocardial infarction patients were excluded. The outcomes measured were DVT, pulmonary embolism (PE), major bleeding, and death. As compared with controls, all three regimens significantly reduced DVT (ranging from 58% to 72%), showed a nonsignificant trend toward reduction in PE (by 46% to 67%), and had no difference in risk of major bleeding or death.
UFH BID vs. TID were compared indirectly by using data from their trials against control patients or low-molecular-weight heparin. There was no significant difference between UFH TID and BID in reducing DVT (RR 1.56, CI 0.64-4.33), PE (RR 1.67, CI 0.49-208.9), mortality (RR 1.17, CI 0.72-1.95), or causing major bleeding (RR 0.89, CI 0.08-7.05). Additionally, both UFH dosing frequencies were similar to low-molecular-weight heparin in all four measured outcomes. This evidence is of moderate quality due to the lack of a direct comparison between UFH BID vs. TID.