To study the Proportion of Ultrasonically assessed Diaphragmatic weakness with the need for Postoperative Mechanical Ventilation in Geriatric Patients undergoing Abdominal Surgery under General anaesthesia:An Observational Study

The study protocol will be explained to the patients who will be found eligible for our study, based on inclusion criteria. A written consent will be obtained from those willing to participate in our study. In the preoperative room routine monitors [i.e., pulse oximeter, ECG and non-invasive blood pressure(NIBP)] will be attached and baseline vitals will be obtained. Mini Nutritional Assessment (MNA) score will be calculated in the preoperative period. Diaphragm function will be assessed using ultrasound.

Patients will be taken inside the operation theatre. All the routine monitors i.e., pulse-oximeter, ECG, and NIBP will be attached. An epidural catheter may be inserted based on anaesthetist’s discretion. Patient will be preoxygenated or denitrogenated to increase apnoea time followed by administration of injection (inj.) fentanyl 1-2μcg/kg i.v. Thereafter induction agents i.e., inj. propofol (1-2.5mg/kg) or etomidate (0.2-0.3mg/kg) i.v. will be given. For muscle relaxant inj. vecuronium 0.1 mg/kg i.v. will be used. Patient will be intubated and mechanically ventilated on volume control mode. Ventilatory settings will be as follows: - tidal volume (VT) 6-8ml/kg, respiratory frequency 12-14/min, PEEP 5 cm of H2O so as to maintain an EtCO2 of 30-35. Throughout the surgery the anaesthesia will be maintained using sevoflurane with 40% oxygen and intermittent injection of vecuronium. The Train of four (TOF)-ratio will be measured and dosage of vecuronium will be decided on its basis. The total requirement of muscle relaxant will be noted. Other than routine monitors we will attach bi-spectral index monitor on the forehead of the patient. We will maintain bi-spectral index between the ranges of 40-60.

After the surgery is over, diaphragm assessment (TFdi) will be repeated on both sides.  Lung ultrasound score and ABG will be done for all patients to know the lung condition and need for mechanical ventilation. Patients will be extubated if they are meeting clinical criteria for extubation (i.e., regular respiration, stable vitals, follows commands, hand grip and head lift). Any patient not meeting the criteria for extubation within 1 hour of stopping muscle relaxant will be considered for elective mechanical ventilation as per the discretion of treating anaesthesiologist and surgeon.

All patients will be shifted to either post anaesthesia care unit (PACU) or intensive care unit or high dependency unit (depending upon availability of ventilator). 1 hour post operatively an ultrasonographic assessment of diaphragm, lungs and ABG will be performed to rule out pulmonary complications. Patient outcomes will also be assessed including delayed extubation, recovery, length of hospital stay, prolonged hospital stay, length of ICU stay and mortality for upto a period of 7 days.