Response

Abstract

Drs Wilson and Caifa do raise some interesting points with regard to the article “Fatal venous air embolism in a cat undergoing dental extractions” (Gunew and others 2008). With regard to the finding of pneumothorax in this cat, Drs Wilson and Caifa suggest that this may have occurred secondary to pharyngeal or tracheal trauma and that venous air embolism (VAE) may have occurred as a sequel to this. The cat in question was intubated with a Cook Veterinary Products non-cuffed silicon endotracheal tube. There was also no evidence of pharyngeal trauma at post-mortem examination. While this does not completely rule out this scenario, we feel it is highly unlikely. According to practice protocol, while under anaesthesia this cat was monitored by a member of the nursing staff, and pulse oximetry, end tidal carbon dioxide levels, and systolic blood pressure were all monitored while under anaesthesia. Intravenous fluids were maintained however all within this practice are well trained to flush lines carefully before connecting patients to intravenous fluids. An infusion pump was also utilised in this case (Heska, Vet/VI 2.2). This system contains an alarm to signal if there is air within the line. While it does not completely eliminate the possibility of air entering through the intravenous line these factors do greatly reduce the risk. The cat had also been on intravenous fluids for a period of time prior to cardiopulmonary arrest. The post-mortem examination was performed in-house and not sent externally to a pathologist. The post-mortem examination was performed within 15 minutes of death. We believe that the air present in the caudal vena cava, hepatic and renal veins is not a reflection of systemic circulation of air but rather retrograde flow of air from the right side of the heart, either passively after death or as a result of resuscitation efforts. It is worthy of note that the cat underwent several changes of position prior to post-mortem examination. With regard to the idea that another possible cause of the VAE was the 3-way syringe to deliver air under pressure the authors do concede that this is possible however this piece of equipment had not recently been in use in this case prior to cardiopulmonary arrest. While Doctors Caifa and Wilson rightly point out that high-speed drills have been utilised in thousands of extractions and bone sectioning without issue, there is a considerable amount of literature supporting the association between VAE and high-speed hand pieces. No procedure is without risk. After all, vaccination is performed hundreds of thousands of times daily, yet no one would argue against the idea that adverse reaction to vaccination occasionally results in death. We agree that it is essential that such equipment is used correctly to avoid iatrogenic damage. While the practice of “atomising” fractured tooth roots is contentious and should be avoided it is unfortunately still practiced in veterinary medicine currently. We believe that this case report is very useful in highlighting the dangers of this practice. The authors are certainly not advocating that practitioners should abstain from the use of high speed air driven dental equipment. We continue to use them routinely within this practice. However, as clinicians we all need to be aware of the potential consequences of the procedures that we perform. While VAE may be a rare event, it is one that the clinician should be mindful of particularly when performing dental procedures.