The conventional TUR system, which involves patient’s body being in the energizing circuit with a non-electrolyte irrigation solution, occasionally causes hyponatremia, also known as TUR syndrome, due to the absorption of non-electrolyte irrigating solutions. In contrast, the TURis system is an alternative system that uses bipolar resection where the human body is electrically insulated from the energizing circuit and uses normal saline as the irrigating fluid. These properties contribute to the prevention of hyponatremia [1, 2].
However, some case reports show symptomatic absorption of irrigated normal saline during surgery. An abrupt large amount of normal saline has been reported to induce high chloride metabolic acidosis leading to various symptoms [3]. In another case report, the patient’s pH changed from 7.41 to 7.28 in 120 min due to rapid absorption of 6 L of irrigated normal saline [4]. The assumed amount of normal saline absorbed in our case was approximately 8.4 L, which was calculated based on a formula using serum chloride concentration in a previous report [5].
Metabolic acidosis can affect consciousness and hemodynamics. Although the acceptable pH level remains to be disputable, a pH around 7.1 or 7.2 seemed to be the borderline for unresponsiveness to catecholamines [6]. Rapid blood pressure recovery after the improvement of acidosis was due to the following reasons: Acidosis produces a substantial, reversible decrease in the number of cell surface α-adrenergic receptors and reduces the contractile force of the cardiac muscle. Arterial vasodilation caused by acidosis has been reported in the setting of in vitro experiments [7]. No deterioration of cardiac function and valvular regurgitation was found in TTE at the end of the surgery in our case; thus, the primary reason for hypotension might be vasodilation due to metabolic acidosis.
As a new method for TUR-P, holmium laser enucleation of the prostate (HoLEP) has been developed, which also uses normal saline as an irrigating fluid. The TURis system resects the tissue gradually; in contrast, the HoLEP system uses a laser to vaporize the tissue along with hemostasis. Therefore, the risk of bleeding and absorption of irrigating fluid is expected to be lower than that of the TURis system. However, normal saline absorption leading to hyperchloremic metabolic acidosis and volume overload in the HoLEP has also been reported [3, 8,9,10].
Gas emboli, which are products of electrosurgical vaporization, could also cause hemodynamic deterioration. Gas embolism may lead to symptoms similar to those associated with TUR syndrome. A randomized controlled trial of air embolism during hysteroscopic surgery under general anesthesia using bipolar or monopolar has been reported. Air was found in almost all cases with transesophageal echocardiography (TEE), and some patients showed ST-segment changes, blood pressure drop, and decreased Et.CO2. A large amount of air was observed, especially in patients with absorption exceeding 1 L. [11] Although gas embolism could not be ruled out because Et.CO2 decrease was not monitored, it would not be the pathological mechanism in the present case. For gas embolism being the primary cause, administration of bicarbonate solution would have worsened acidosis and its symptoms.
In conclusion, we report a case of hyperchloremic metabolic acidosis with decreased level of consciousness and hypotension during TURis. There are various treatments for benign prostatic hyperplasia. Regardless of the surgical procedure, abnormality caused by irrigation fluid absorption should be considered. In general, spinal anesthesia seems to be optimal in TUR, because patients’ consciousness can be assessed in cases of hyponatremia. Even though in the TURis system electrolyte disturbance can develop, spinal anesthesia may be a reasonable choice to enable the assessment of patients’ consciousness.