Hemodynamic Study With PRAM of the Cardiovascular Response to the Positioning of the Extraglottic Device

Introduction Laryngoscopy and tracheal intubation may cause significant hemodynamic changes in the patient and induce cardiovascular complications.

Numerous studies have sought methods to reduce this risk (1-5). The extraglottic not involving either laryngoscopy or their passage through the vocal cords, have proven protective of the possible cardiovascular complications resulting from the placement of respiratory prosthesis (6,7).

Measurements of hemodynamic changes resulting from the procedures for airway management with extraglottic have not previously been carried out.

The MostCare (Vytech, Vygon Italia srl, Padova, Italy) is a monitor provided for more than 10 years at the obstetric gynecological anesthesia unit able to evaluate the hemodynamic changes in a patient based on the Pressure Recording Analytical Method (PRAM).

This is a measurement method of the cardio-circulatory performance of a patient that does not require calibration and / or insertion of a pre-estimated data because the method of analysis of the wave form of the arterial pressure is developed completely a priori (8). The measurement derives from the simultaneous analysis of the components of a pulsatile flow and the continuous flow as a ratio between the area under the curve of the pulsatile portion of the systolic pressure and the characteristic impedance Z (t). The PRAM method has proven effective in many clinical settings (9).

The Medical Device (DM) will be used in accordance with the indications of use for which it has acquired the CE mark. A morphology detection system linked to high blood pressure curve detected through non-invasive Masimo oximetry system supplied to the Hospital will be used Purpose of the study The purpose of the research will be to record the hemodynamic response measured by traditional methods (non-invasive blood pressure and ECG) and PRAM method in patients undergoing placement laryngeal mask compared with the hemodynamic response measured in patients undergoing laryngoscopy and tracheal intubation for performing surgery in gynecological area and assess the differences with the two methods

Methods This will be a prospective observational study. Data will be collected from all consecutive patients undergoing general anesthesia for gynecologic surgery for a period of 3 months or until the minimum number of 94 patients (see section statistical analysis).

In the operating room the patient will undergo to active pre-warming with hot air, peripheral venous cannulation and premedication with midazolam 0,04 mg/kg, and fentanyl 1.5 mcg/kg body weight. After the positioning of the standard monitoring systems (ECG, Non-Invasive Blood Pressure, Pulseoximetry, Neuromuscular Transmission), the signal from the Pulseoximetry will also be analyzed by the MostCare monitoring system that allows to apply the measuring method PRAM noninvasively.

After 3 minutes of high flows O2, propofol 2 mg/kg body weight and rocuronium 0.9 mg/kg body weight will be administered sequentially to the patient. Anesthesia will be maintained with propofol continuous infusion (9-12 mg/kg body weight /hour) and remifentanil continuous infusion (0.2 mcg/kg body weight /minute ). At the disappearance of the adductor muscle response to electrical stimulation of the thumb "Train of four" (TOF) applied to the ulnar nerve the positioning maneuver of the respiratory device will be performed:

• with direct laryngoscopy in the case of endotracheal intubation
• with direct insertion in the case of laryngeal mask placement. Proper placement will be evaluated by chest auscultation, spirometry and analysis of the concentration and the carbon dioxide curve in exhaled gases.

The data obtained from the PRAM and the usual monitoring will be recorded on a special sheet by an outside observer.

In the case of failed positioning of the respiratory device, the procedure will be repeated and in case of further failure will proceed as indicated by national and hospital guidelines (10), but the patient will still be excluded from the study ..

The choice of the respiratory device will depend on the type of intervention scheduled in the operating program.

The hemodynamic and monitoring data will be recorded every minute for 5 minutes for each patient.

The study duration will be 3 months (or in any case until reaching the minimum number of 94 cases).

The patients will be divided, retrospectively, in two groups according to the type of device used for airway management.

The two groups will be compared on the basis of age and anthropometric parameters. An analysis of the hemodynamic response of the two groups of patients to the positioning of the respiratory device will then conduct.

Statistical analysis A recent study (11), that analyzed the cardiac index changes in response to tracheal intubation with laryngoscope Mcintosh in comparison to the video laryngoscope laryngoscopy, showed a difference of 1 L/min/m2 (from 3.1±0.6 to 4.3±1.4 with laryngoscope McIntosh vs 3.0±0.3 to 3.2 ± 1.1 with videolaryngoscope).

Therefore, to test the hypothesis that the cardiac index difference using the airway management with traditional intubation compared to the use of the laryngeal mask is greater than or equal to 1 L/min/m2, having fixed the first type error to the 5% and the study power to 80%, it is possible to calculate that the sample size needed for a one-tailed test is represented by 47 patients per group.

The average of the data collected in each group of patients will be compared with Student's t test.

Expected results To verify, in two of homogeneous population groups for anthropometric and clinical data, the least impact on the cardiovascular system produced by the placement of laryngeal mask compared to that induced by endotracheal intubation with conventional laryngoscopy taking advantage of non-invasive hemodynamic monitoring system of the pulse oximetry MostCare (methodology PRAM) ever tested in this field.

Also to check the hemodynamic impact of any repeated attempts to both of the above maneuvers for airway management.

Ownership of the results will be accredited by the principal investigator on behalf of the AOU Careggi and the University of Florence as headings of him which has neither received nor will receive any fee for the conduct of the study.