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Pulmonary embolism

VERY difficult to diagnose, the key is to remain suspicious and vigilant. Can lead to hemodynamic collapse. Intraoperatively, a sudden drop in ETCO2 is suggestive of increased deadspace which has many potential causes, including pulmonary embolism.

Symptoms (in awake patients) include dyspnea, tachypnea, chest pain, palpitations. Signs include hemoptysis, rales, wheezing, split heart sounds. The classic S1Q3T3 (S Wave in Lead I, Q Wave in Lead III, T Wave Inversion in Lead III) is seen in less than 20% of cases

Orthopedic patients are at high risk and these patients should receive thromboprophylaxis unless contraindictated. A spinal anesthetic may be helpful in this regard (i.e. lowering the risk of a thrombotic event), with an odds ratio of pulmonary embolism reported to be 0.26 as compared to GA.

Pulmonary Embolism

  • ABG: essentially useless (“classic” finding is respiratory alkalosis + hypoxia)
  • EKG: S1Q3T3 in < 20% of cases
  • ETCO2: look for sudden drop intraoperatively (deadspace)


  1. William J Mauermann, Ashley M Shilling, Zhiyi Zuo A comparison of neuraxial block versus general anesthesia for elective total hip replacement: a meta-analysis. Anesth. Analg.: 2006, 103(4);1018-25 PubMed Link