Fatal venous air embolism during lumbar surgery: the tip of an iceberg?

EDITOR: Venous air embolism (VAE), the entrainment of air into the venous system during surgery, is a well-known complication of surgery in the sitting position. VAE can also occur in the prone position but is under suspected and under reported. There is only one report of VAE occurring in three separate patients in the prone position. There are no reports published in the European literature. Though rare, VAE can be a devastating event. We present a case of fatal VAE that occurred during an elective lumbar laminectomy. By reporting this case, we hope to raise awareness that this complication can occur in the prone position and to encourage increased monitoring for VAE in high-risk patients. A 43-yr old female presented for a repeat lumbar L4/5 laminectomy. Anaesthetic history was unremarkable. A past history of breast malignancy and subsequent resection was noted. On arrival in the anaesthetic room, full monitoring was commenced, including non-invasive blood pressure (NIBP), pulse oximetry, electrocardiogram (ECG) and end-tidal carbon dioxide (ETCO2) measurement. Following induction of anaesthesia and muscle paralysis, the trachea was intubated and lungs ventilated with oxygen-enriched air. Anaesthesia was maintained using a target controlled infusion of propofol 3.1–4.0mg mL and a remifentanil infusion 0.05–0.1mg kg min, titrated according to depth of anaesthesia. The patient was transferred into the operating theatre and placed on support cushions in the prone position. Careful adjustment was made to allow for free abdominal movement during ventilation. Forty-five minutes after the commencement of surgery, an increase in the pulse rate from 75 to 90 beats min was noted. The propofol infusion was increased. Shortly thereafter, the ETCO2 level fell from 4.4 to 2.9 kPa, and this was followed by an unrecordable NIBP. A venous air embolism was suspected. The surgeon was informed and the wound was flooded with saline; the FiO2 was increased to 1, and ephedrine and a fluid bolus were given. ST depression was seen on the monitor and although a carotid pulse could not be detected, the oxygen saturation remained at 99%. Within 1 min, the situation improved with the NIBP rising to 82/60 mmHg, a heart rate of 90 bpm, a return to baseline of the ST segments and a rise in the ETCO2 to 4.0 kPa. The surgical wound was kept flooded with saline, and the surgical procedure was rapidly completed. The patient was returned to the supine position, whereupon she began to breathe spontaneously and opened her eyes to command. Without warning, she suddenly became pale and unresponsive, accompanied by a fall in the NIBP to 40/20 mmHg. A precordial Doppler was placed on the chest and a further air embolus confirmed. Resuscitative measures were instituted and the patient was turned into the left lateral position in preparation for right central venous access. Before this could be achieved, the patient suffered a cardiac arrest and was turned back into the supine position for cardiopulmonary resuscitation (CPR). The abdomen was noted to be distended, leading to a presumptive diagnosis of significant intra-abdominal haemorrhage. An exploratory laparotomy was performed, but no source of bleeding could be found. The abdominal aorta was non-pulsatile and after a period of time, when both pupils were fixed and dilated, the attempts at resuscitation were abandoned. At post-mortem, the heart and great vessels were removed en-bloc and moderate-sized air bubbles were found in the right atrium. There was no obvious damage to any of the great vessels close to the operative site. However, a small amount of blood was found in the retroperitoneal space. A patent foramen ovale was not sought. Correspondence to: Dr Sara Frances McDouall, Department of Anaesthetics, Royal Berkshire Hospital NHS Foundation Trust, London Road, Reading RG1 5AN. E-mail: [email protected]; Tel: 0118 322 5111