There has been enormous worldwide interest in a simple surgical alternative to abdominal or vaginal hysterectomy. Endometrial resection (TCRE) with the use of the resectoscope has been considered as an alternative to hysterectomy for the treatment of intractable uterine bleeding (1). The procedure is similar to transurethral resection of the prostate (TURP) in terms of technique and the use of a liquid medium such as 1.5% glycine for distension and irrigation of the uterus. Absorption of a large volume of fluid can cause excessive intravascular volume, hyponatremia (2), cerebral edema (3–5), hyperammonia (6), hyperglycinemia (7), and hemolysis. Air embolism, although rare, is a possible complication during TCRE. With the use of loop diathermy for endometrial ablation, air embolism can occur during surgery whenever the vein is open or when air pressure exceeds the venous system (8). We report a case of air embolism during TCRE.
A 50-yr-old woman, weighing 70 kg, presented with the complaint of menorrhagia for 3 yr. She was scheduled for a TCRE in the premenstrual phase of her cycle. She had been hypertensive for the last 10 yr and was treated with atenolol 50 mg and amlodepin 5 mg, both twice daily. Airway examination during the preanesthetic checkup revealed a modified Mallampatti Class II: short neck and protruding teeth. Her other preoperative evaluation was within normal limits. She received her morning dose of antihypertensive drugs and premedicated IM with meperidine 50 mg and promethazine 25 mg 1 h before surgery. Anesthesia was induced with thiopental 250 mg, oxygen (O2) and nitrous oxide (N2O) (50%), and 0.5% halothane. Succinylcholine, 100 mg, was given IV to facilitate endotracheal intubation. Anesthesia was maintained by using O2, N2O, and halothane, and vecuronium was given IV for muscle paralysis. The usual monitoring and input and output of IV fluids were used, and the pressure, rate, and volume of glycine infused through the intrauterine route were determined. Endometrial ablation was performed with the use of “loop diathermy.” Glycine 1.5% under 140-mm Hg pressure was used as an irrigation fluid at the rate of 150 mL/min. Irrigation fluid pressure was maintained by using a roller pressure pump, and surgery was performed in lithotomy with 30° head-low position. During the procedure, the patient’s heart rate was 69–90 bpm, arterial blood pressure was 120/60 to 130/80 mm Hg, SaO2 was 99%–100%, and PETCO2 was 32–34 mm Hg.
After 40 min, SaO2 began decreasing gradually, with a decrease to 76% along with a sudden decrease in PETCO2 to 17 mm Hg. Heart rate increased to 102 bpm. An electrocardiogram tracing was normal. No significant change in arterial blood pressure was noticed. Auscultation of the chest revealed equal air entry. No rhonchi or crepitations were heard, and heart sounds were normal and without any murmur. At this point, the surgeons were asked to discontinue the procedure. Based on the above findings, a presumptive diagnosis of air embolism was made. The patient’s lungs were ventilated with 100% O2. During that time, the total volume of irrigating fluid infused was 3000 mL, and the output was approximately 2400 mL. Acute changes in oximetry and PETCO2 were verified on the trend mode of a monitor. Inspection of the glycine bag and infusion tubing showed no evidence of air. PETCO2 and SaO2 gradually returned to normal over a period of 7 min with 100% O2, and no further resection was done. Muscle relaxation was reversed with IV neostigmine and atropine. Recovery from anesthesia was uneventful. Postoperative hemoglobin, electrolytes, and electrocardiogram were normal. The patient was discharged from hospital the following day.
Endometrial ablation with the use of loop diathermy or roller ball is a relatively new gynecological procedure and a less invasive alternative to hysterectomy for patients with intractable uterine bleeding. To perform endometrial resection, a rigid hysteroscope is used with a Hopkins rod lens system and a fiberoptic or liquid cable to transmit light from an external power source. Electrodiathermy is performed by using either a loop diathermy or roller ball. For distension of the uterus, glycine (1.5%) is the usual choice of infusion fluid. It can be instilled by several methods, such as pressurizing the fluid infusion bags, or peristaltic roller pumps applied externally on the drip tubing or gravity feed system. If a peristaltic pump is used, settings vary to some extent from patient to patient with a fluid pressure of 100–125 mm Hg, a suction pressure of −50 mm Hg, and flow rates of up to 300 mL/min (9). Systemic absorption of small quantities of glycine is generally well tolerated; however, there is increasing evidence that glycine absorption and products of its metabolism can lead to hyperglycinemia (7) and hyperammonia (6), causing specific symptoms that resemble those of a TURP syndrome (10,11). Severe dilutional hyponatremia has been reported during laser ablation using this medium (2).
Air embolism during TCRE is a rare but possible complication (8,12). It can occur in the presence of an exposed open vein when air pressure is greater than venous pressure (8). This can be the result of an increase in air pressure similar to that occurring during insertion of cemented femoral prosthesis (13) or a decrease in venous pressure caused by elevating the operative site above the level of the heart, which is of particular risk when a patient is breathing spontaneously. Fatal air embolism can occur during TURP (14). Fatalities have been reported to be caused by air embolism during laser ablation when gas-cooled sapphire tips were used to deliver the laser energy into the uterine cavity (15). Cardiac arrest, a complication possibly caused by air embolism, has also been described during TCRE (16). The equipment used during endometrial ablation may result in air embolism. Hence, irrigation pumps, tubing, and delivery systems for uterine irrigation fluid should always have an air-trapping system. Air can also come from the bubbles produced by the diathermy in irrigation fluid. Although the bubbles generated by diathermy are very small, they are under pressure and can expand in the venous system with a much lower pressure, especially in the head-down position when uterine vessels are at a higher level than the heart. The surface area for absorption from uterine vessels is larger, especially during the premenstrual phase.
The physiological consequences of venous air embolism depend on the volume as well as the rate of air entry and whether the patient has a probe-patent foramen ovale (10%–25% incidence). The latter is important because it can facilitate passage of air into the arterial circulation (paradoxical embolism). The amount of air required for different clinical signs and symptoms is shown in Table 1 (17).
Our patient was ablated in a head-low position and in her premenstrual phase. The endometrium was thus very vascular. All these factors would have predisposed the patient for the entry of air bubbles into the venous system. During the surgery, a sudden decrease in PETCO2 was noticed. Becasue the arterial blood pressure was maintained, a sudden decrease in cardiac output was excluded as the cause of the event, and a presumptive diagnosis of pulmonary air embolism was made. Because it was detected very early, remedial measures could be taken immediately, and full recovery was achieved without any sequelae. A small microtissue embolism during an ablation procedure is also a possibility. To conclude, TCRE is minimally invasive but may be associated with potential fatal complications.
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