Air embolism—a complication of percutaneous nephrolithotripsy

N. Usha1 and L. Droghetti2

1 Chandigarh, India 2 Ferrara, Italy

Editor—Droghetti and colleagues1 reported a case of air embolism in a patient undergoing percutaneous nephrolithotripsy (PCNL). I would like to compliment the authors for successfully managing their patient.

Similarly, I encountered a case of suspected air embolism following air pyelogram during PCNL. A 43-year-old healthy female presented with a solitary calyceal stone in the left kidney. PCNL was planned under general anaesthesia with IPPV using nitrous oxide 66% in oxygen. The intraoperative monitoring included electrocardiogram (ECG), pulse oximetry (SpO2), end-tidal CO2 (PE'CO2) and non-invasive arterial pressure recorded at 3 min intervals. After induction of anaesthesia, the patient was placed in the lithotomy position. A ureteric catheter was passed into the left kidney. The patient was then turned prone. After confirming the position of the ureteric catheter under fluoroscopy, the pyelogram was performed by injecting 15 ml of air into the left pelvicalyceal system through the ureteric catheter. This was repeated twice to obtain proper visualization (50 ml of air), and this was followed by injection of saline through the ureteric catheter to distend the kidney.

Within 2–3 min of the saline injection, while the left flank was being prepared, there was an abrupt fall in PE'CO2 from 38 to 23 mm Hg. The radial pulse was palpable and all other variables were within normal limits. Immediately, the nitrous oxide was discontinued and manual ventilation with oxygen 100% was started. The tracheal tube position was found to be correct and air entry was equal bilaterally. In less than 1 min, multiple ventricular ectopics appeared on the ECG monitor, followed by ventricular tachycardia. The arterial pressure dropped from 143/87 to 58/37 mm Hg, PE'CO2 dropped further to 16 mm Hg, and the SpO2 was 93% on oxygen 100%. The patient was turned supine immediately. The ECG showed asystole. The pupils were dilated but reacting to light. One millilitre of 1:1000 epinephrine was administered i.v. and external cardiac massage started. The ECG at this stage started showing supraventricular beats with a heart rate of 150 beats min–1. There were multiple ventricular ectopics and the peripheral pulse was feeble. The patient started improving gradually, and 30 min later the heart rate had settled to around 100 beats min–1 with occasional ectopics. The arterial pressure was 108/64 mm Hg without inotropic support, PE'CO2 was 34 mm Hg and the SaO2 was 100% on a Fi O2 of 1. Later, when the patient started making spontaneous respiratory effort, vecuronium was given again and nitrous oxide 50% was re-introduced. This was followed by an abrupt drop in PE'CO2 and multiple ventricular ectopics reappeared. On discontinuation of nitrous oxide, the ectopics reverted to sinus rhythm and the PE'CO2 improved. The patient was further observed for 2 h, and given oxygen 100% and i.v. sedation with propofol. When it was found that all the variables were stable, surgery was completed without further problems. Postoperatively, the patient was mildly hypoxic for 6 h but subsequently recovered and was maintaining an SpO2 of 98% on room air. The patient was observed for 48 h and found to have no sequelae.

Air pyelogram has the potential risk of air embolism.2 3 In our case, the clinical features are strongly suggestive of air embolism. The volume of air injected far exceeded the recommended dose (10–15 ml).3 4 The safety of injection of even 15 ml of air in the presence of nitrous oxide and the prone position is doubtful. Saline injected after air will compound the problem as it increases the pressure in the renal pelvis, predisposing to pyelovenous back flow. A standard textbook of urology does not mention the risk of air embolism during air injection in PCNL.4 Hence, urologists are not aware that this is a risky technique which is potentially fatal. Urologists who prefer to use air during PCNL under general anaesthesia must be strongly advised to use CO2 for the pyelogram.

N. Usha

Chandigarh, India

Editor—We thank Dr Usha for her interest in our case report. In her patient undergoing PCNL the air injected in the renal pelvis presumably entered into the circulation, inducing ventricular arrhythmias and then cardiac arrest. The patient quickly recovered after resuscitation and ventilation with oxygen 100%, but persistence of air in the venous system by Doppler was not ruled out. We think that re-introducing nitrous oxide was hazardous as it may have induced an increase in the size of the accumulated bubbles. The second episode of a fall in end-tidal CO2 with appearance of ventricular ectopics confirms this hypothesis.

The use of nitrous oxide in patients at risk of venous air embolism (VAE) is controversial.5 Losasso and colleagues6 reported a lack of increase in the incidence or severity of embolism during sitting craniotomy in patients receiving nitrous oxide, but it was discontinued immediately if VAE was detected using Doppler.

Standard textbooks of urology do not mention the risk of VAE, and therefore surgeons may underestimate it. Nevertheless, its occurrence has been documented during surgery in the prone position,7 in urological procedures,8 and in PCNL.9 We agree with Dr Usha that urologists should consider the risk of VAE during surgery and therefore use CO2 instead of air for the pyelogram.

L. Droghetti

Ferrara, Italy

References

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