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Fatal gas embolism during transurethral enucleation of the prostate with bipolar electrodes

In this report, we describe a case of gas embolism occurring during TUEB, which might have been induced by gas generated from the electrode.


Authors: Inokuchi, Go; Yajima, Daisuke; Hayakawa, Mutsumi; Sakuma, Ayaka; Makino, Yohsuke; Iwase, Hirotaro
Corresponding Author: Go Inokuchi, Department of Legal Medicine, Graduate School of Medicine, Chiba University, Chiba, Japan.   Email: [email protected]


Transurethral resection of the prostate (TURP) is the most common surgical treatment for benign prostatic hypertrophy. In recent years, however, new transurethral resection techniques, including transurethral resection of the prostate in saline (TURis) and transurethral enucleation with bipolar (TUEB) electrodes, have been developed to minimise surgical complications such as TURP syndrome, obturator nerve reflex and haemorrhage. Application of the TUEB procedure to clinical cases has only recently started (1).
During prostate surgery, gas embolism can occur as a complication of medical intervention and may lead to death (2). Consequently, it is vital to understand whether the specific cause of the gas embolism can be elucidated and meaningful feedback given to the medical community. In this report, we describe a case of gas embolism occurring during TUEB, which might have been induced by gas generated from the electrode.


Case report


Clinical course
A 72 year old man (72kg, 165cm) was scheduled to undergo TUEB for the treatment of benign prostate enlargement. Preoperative tests were unremarkable. The procedure was performed with the patient in the reverse Trendelenburg lithotomy position under spinal anaesthesia, and no problems with the induction of anaesthesia were noted. The patient was not wearing anti-embolic stockings. Thirteen minutes into the operation, the patient complained of epigastric discomfort and blood pressure gradually dropped to 73/48mmHg from 131/97 mmHg, but heart rate remained unchanged at 60-70 bpm.
After administration of a plasma substitute was started, blood pressure returned to between 80 and 100mmHg, and the operation proceeded without major bleeding from the bladder or prostate. There were no gas bubbles other than the gas generated from the electrodes seen in the surgical field on the surgical monitor during the procedure. Around 90 min later, enucleation of the prostate was completed. The surgeon then used a tissue morcellator to cut the resected prostate into small pieces. A few minutes after inserting the morcellator into the bladder, the patient lost consciousness and the electrocardiogram was flat.
Cardiopulmonary resuscitation was performed and the patient was taken to the medical care center, but subsequently died. Immediate postmortem computed tomography (CT) showed a large volume of gas in the heart (both left and right ventricles and left and right atria), pulmonary artery, cerebral vessels, vessels around bladder and bladder. (Figs.1, 2)


Figure 1.


Figure 2.

Autopsy findings
On external examination, there were no remarkable findings. On internal examination, left and right atrial puncture clearly revealed the presence of gas which had been confirmed by CT prior to autopsy. The foramen ovale was closed and the heart showed no organic problem. In the bladder, the urethral orifice was enlarged and the residual prostate gland remained (weight 40g). Furthermore, there was no major blood vessel injury into which gas might have entered. Histological examination showed congestion of the heart, liver and kidney, but there were no specific findings. We concluded that the cause of death was air embolism.


Verification experiment
On autopsy, we resected part of the prostate taken from the cadaver using the resection apparatus used clinically in 10 L saline at room temperature. Resection  took2 min and the gas generated was collected with a syringe in order to measure the amount. In our measurements, gas was generated at approximately 15 mL/min in resection mode (Fig. 3). No gas was generated in coagulation mode.


Figure 3. 

It is well known that gas embolism can occur during invasive diagnostic or therapeutic intervention (2).  Gas embolism during TURP, however, is exceedingly rare and there are only a few case reports in the anesthesia and urology literature (3–8).
The mechanisms of gas generation discussed in previous reports are as follows.
・ Incorrect assembly of the bladder irrigation-resectoscope-drainage system: gas flows into the bladder due to reverse connection of the inflow and the outflow lines (6, 8)
・ Infusion of gas into the irrigation fluid used to rinse the bladder at the end of the procedure (Ellik’s evacuator or three-way Foley catheter) (3, 4)
・ Infusion of gas into the irrigation bag (5)
・ Inclusion of gas when the internal cylinder is inserted and removed (5)
・ Gas generation by an electrosurgical knife (5)
In the present case, neither the drain system nor Ellik’s evacuator had been employed during the procedure. In addition, it had been strictly confirmed that no gas was present in the irrigation bag. Tsou et al. considered the possibility that air embolism can be induced by infusion of gas generated from irrigation fluid that is vaporized by the electrical discharge of an electrode and by the infusion of gas into the bladder when the internal cylinder is inserted and removed (5). They did conclude, however, that the probability of a lethal volume of gas generated by such procedures is very low.
An electrosurgical knife resects tissue by arc discharge which is produced though the high-voltage potential formed at the part with the highest resistance value in the electrical circuit. While monopolar electrodes produce this arc discharge at the site of contact in the human body, bipolar electrodes (loop electrodes) generate a high voltage potential with gas bubble produced all around the electrodes, because normal saline has lower resistance than human tissue. For this reason, bipolar electrodes can generate more gas than when monopolar electrodes are used for conventional TURP (9).
In the present case, the ventral mucosa of the prostate adenoma was resected at an early stage. Therefore, it was thought that a vascular stump may have been exposed to gas over a clinically significant time period, so that avolume of gas could have entered and accumulated in the veins. However, Tsou et al. considered it doubtful that a lethal volume of gas could have been generated from an electrode. To address this question we conducted an experiment to elucidate the volume of gas that can be produced when resecting in saline with bipolar electrodes, observing that gas was generated at a rate of approximately 15mL/min. It has been reported that the lethal volume of air is approximately 200mL(10). This volume would be generated in 14 min in our observations; if a large proportion  of the generated gas is taken up by the vascular system, sufficient volume may be accumulated intravascularly to cause death.
The patient’s complaint and the reduction of blood pressure shortly before cardiopulmonary arrest might have indicated that gas embolism had already developed at this point. Although gas embolism caused by the loop electrode may have been the decisive event, it might have been overlooked because the patient exhibited only minor symptoms and fatal cases are rare. Taken together, urologists should be aware of the possibility of gas embolism when a patient complains of discomfort or when there is a reduction in blood pressure during surgery.


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Date added to 06/06/2011 

DOI: 10.1002/BJUIw-2011-012-web


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