Letters to the Editor: Letter to the Editor
To the Editor
The article “Pediatric Perioperative Life Support”1 effectively covered cardiac arrest in the operating room; however, the section on Venous Air Embolism (VAE) requires an update. Management suggested that “…Immediate treatment includes lowering the operative site to below heart level if possible and flooding the operative field to prevent further air entry. Positioning the patient to prevent entry of air into the pulmonary artery helps prevent obstruction of flow to the left heart (left side down and Trendelenburg)…”
This recommendation refers to the work of Durant et al.2 The pathophysiology and management of VAE have been refuted by more recent studies. Mehlhorn et al.3 anesthestized 22 dogs and monitored cardiac output along with arterial, central, and pulmonary artery pressures. Each dog received a 2.5 mL/kg IV air embolus and then positioned left lateral, right lateral, or supine. Position changes after air embolism resulted in minimal hemodynamic changes despite expected air relocation in the cardiac chambers. Recovery of pressures and cardiac output was similar for all groups.
Geissler et al.4 repeated the study and included transesophageal echocardiography. Transesophageal echocardiography examination after air embolism revealed relocation of the air in the heart with position changes. However, this repositioning did not result in improved hemodynamic performance. Hemodynamc improvement occurred with increased coronary perfusion pressure. In other words, the deterioration in cardiac function was due to right ventricle ischemia (coupled with right ventricle chamber dilation with air) as opposed to an airlock in the right ventricular outflow tract.
It is interesting that in both studies only the supine position did not involve the death of at least 1 animal. This point is of more than academic interest. At best, left lateral positioning of a hemodynamically unstable patient with VAE would be of no benefit. However, the lateral position would interrupt or delay cardiac massage and vasopressor therapy that are evidence-based interventions.
Gary Simon, MD, FRCPC
Anesthesia & Perioperative Medicine
London Health Sciences Centre
1. Shaffner DH, Heitmiller ES, Deshpande JK. Pediatric perioperative life support. Anesth Analg. 2013;117:960–79
2. Durant TM, Long J, Oppenheimer MJ. Pulmonary (venous) air embolism. Am Heart J. 1947;33:269–81
3. Mehlhorn U, Burke EJ, Butler BD, Davis KL, Katz J, Melamed E, Morris WP, Allen SJ. Body position does not affect the hemodynamic response to venous air embolism in dogs. Anesth Analg. 1994;79:734–9
4. Geissler HJ, Allen SJ, Mehlhorn U, Davis KL, Morris WP, Butler BD. Effect of body repositioning after venous air embolism. An echocardiographic study. Anesthesiology. 1997;86:710–7