Safety concern regarding the risk of air embolism secondary to pressure bag infused fluids

Abstract

I appreciate the opportunity to bring this matter to the attention of the readers. Venous air embolus (VAE) is infrequently reported in the human and veterinary literature. [1][2][3][4][5] Air embolus occurs when a pressure gradient favoring air entry into the circulation exists, and air is inadvertently introduced into the vasculature. 1,2 Clinical manifestations of VAE include coughing, breathlessness, hypotension, bronchospasm, hypoxemia, and cardiac arrhythmias. 3,4 In people, it has been reported that 3-5 mL/kg of air can be fatal. 2 In dogs, 0.3 mL/kg has been reported to cause an insufficient pulmonary clearance capacity, and 7.5-15 mL/kg has been reported to be fatal. 3 The rate of delivery of fluids via a pressure bag depends upon a number of factors; however, a small volume of air delivered under high pressure can be catastrophic. The delivery of as little 20 mL/s can cause symptoms, and 70-150 mL/s can be fatal. 1 Standard commercial 1-L fluid bags contain anywhere from 50-70 mL of air instilled by the manufacturer for the purpose of transport, and accidental delivery of this air could have severe consequences in small animal patients. 4Most reports in human medicine describe VAE as a complication of surgical procedures performed above the heart. 2 Inadvertent VAE caused by glass bottles containing fluids is also described. 2,5 Selfcollapsible fluid bags are preferred in human medicine for their reportedly added margin of safety against inadvertent air embolus. 1 However, VAE occurring with use of pressure bags has been infrequently reported. 1,2,4,5 In 2 case reports it was suspected that additional air had been introduced into the fluid bag when fluid lines were changed during the infusion. 1,5 It is possible that the true incidence of VAE is under-recognized, due to the varying sensitivities of detection methods, as well as the possibility of unrecognized subclinical VAE. 2,4 VAE has been described in the veterinary literature secondary to improper flushing of fluid lines and in one case report secondary to the malfunction of a volumetric infusion pump. 3 Pressure bags are commonly used in veterinary medicine to deliver a large volume of IV fluid rapidly to a patient in a hypovolemic crisis. To the authors' knowledge a case of VAE secondary to the use of a pressure bag has not been reported in the veterinary literature; however, it remains a risk. There are numerous anecdotal reports among colleagues who recommend removal of