Assessments of Dynamic Variables of Fluid Responsiveness to Predict Desufflation-induced Hypotension in Urologic Patients Undergoing Laparoscopic Surgery

Laparoscopic surgery can induce hemodynamic pertubations. Pneumoperitoneum, inevitable in laparoscopic surgery, induces increase in intra-abdominal pressure, which can decrease cardiac output. Simultaneously, pneumoperitoneum can stimulate sympathetic system and increase vascular resistance/arterial blood pressure. Patients undergoing laparoscopic surgery may show a normal range of blood pressure during pneumoperitoneum even when the patients are in hypovolemia, and desufflation at the end of main surgical procedure can cause an abrupt hypotension revealing hypovolemia. Therefore, appropriate fluid management is essential for preventing desufflation-induced hypotension in laparoscopic surgery. Recently, dynamic variables are used to predict and guide fluid therapy during controlled ventilation. these variables arise from heart-lung interactions during positive ventilation, which influence left ventricular stroke volume. Several dynamic variables are derived from variations in left ventricular stroke volume (stroke volume variation, SVV), for example pulse pressure variation (PPV), and variations in pulse oximetry plethysmography waveform amplitude (PWV), which have all been shown to predict fluid responsiveness in different clinical and experimental settings. However, there are few evidences regarding which type of dynamic variables can predict desufflation-induced hypotension in laparoscopic surgery. Therefore, this study was designed to assess the predictive abilities of three different type of dynamic variables including PPV, SVV, and PWV for desufflation-induced hypotension in patients undergoing laparoscopic surgery.

The study is a prospective, single-arm, and observational one. Eighty Patients who age more than 19 years and are undergoing laparoscopic surgery for urologic procedures are being enrolled in this study. All anesthetic and surgical managements are being performed according to the institutional standards. An attending anesthesiologist who is independent from this study performs anesthetic managements for the participants including fluid administration.

Investigators assess and record the following parameters at the following time points.

The parameters assessed: mean arterial pressure, heart rate, pulse oxygen saturation, SVV, PPV, PWV, peak inspiratory pressure, plateau pressure, positive end-expiratory pressure, respiratory rate (all dynamic variables are assessed at two levels of tidal volume- 6 ml/kg and 12 ml/kg).

The time points: T0, before anesthetic induction; T1, immediately after anesthetic induction; T2, immediately after pneumoperitoneum; T3, 10 min before desufflation; T4, immediately after desufflation.

The desufflation-induced hypotension is defined as more than 20 % decrease in MAP at T4 from MAP at T3.

Eligibility Criteria:
Inclusion Criteria:

* 1. laparoscopic nephrectomy
* 2. laparoscopic nephro-ureterectomy
* 3. laparoscopic adrenalectomy

Exclusion Criteria:

* 1. ASA physical status 3 and greater
* 2. preoperative arrhythmia
* 3. moderate to severe valvular disease
* 4. ventricular ejection fraction \< 40%
* 5. inotrope use
* 6. moderate to severe chronic obstructive pulmonary disease
* 7. moderate to severe renal or hepatic disease