Effects of Alveolar Recruitment Strategies on Arterial Oxygenation and Postoperative Inflammatory Response During Laparoscopic Bariatric Surgery: A Randomised Control Trial.

• Atelectasis arises shortly following onset of anaesthesia even among a healthy volunteer, and is closely correlated to escalation of intrapulmonary hypoxemia and inevitable gas exchange derangement .
• sixty adult obese patients (body mass index more than 35 kg/m2), of both sexes, aged from 18-65 years old, with American Society of Anaesthesiologists physical Status classification scores of 1-2, scheduled for laparoscopic bariatric procedures. Exclusion criteria were patients refusal, history of significant pulmonary disease (obstructive or restrictive), previous pneumothorax, significant cardiac dysfunction (arrhythmias ± unstable haemodynamics, left ventricular ejection fraction < 40%), difficult intubation as well as those suffering from significant hepatic or renal impairment. Furthermore, patients developed episodes of hemodynamic instability (like desaturation (Sp02< 90 %) or mean blood pressure (MAP) < 60 mmHg) during recruitment manoeuvre were omitted from the study.
• Subjects were randomly assigned -via closed envelopes technique opened immediately before induction- into 2 equal groups (n=30 each) to receive 1 of the following ventilatory regimens:

• Group S: patients received protective lung strategy with recruitment manoeuvre (RM) every 30 minutes and steady PEEP (10) cm H2o in between RM till end of surgery.
• Group D: patients received protective lung strategy with recruitment manoeuvre (RM) every 30 minutes and decreasing PEEP (15, 10, and 5) cm H20 (10 minutes for each level) in between RM till end of surgery.
• Anaesthesia was induced with lidocaine (1mg/kg) followed by (1.5 - 2 mg/kg) propofol (ideal body weight) and (1-1.5 μg/kg) fentanyl. Endotracheal intubation was accomplished with rocuronium (1mg/kg) and a suitable sized tube (8.0 ID). Anaesthesia was maintained with sevoflurane (1-2 %) with (50 %) oxygen in air. Neuromuscular block was continued with rocuronium boluses monitored by train-of four along with additional doses of opioids given as required to achieve a suitable clinical depth of anaesthesia. Precise fluid replacement was administrated consistent with the standard administration guidelines during anaesthesia.
• Patients were ventilated using Datex-Ohmeda Aestiva/5 (Madison, WI) anaesthesia machine, (volume controlled mode) with lung protective strategy using a tidal volume of 6- 8 ml/kg ideal body weight, (5-10 cm H20) PEEP and 50 % O2 in air adjusted to reach Spo2 ≥ 95 %. The respiratory rate was adjusted to keep end - tidal Co2 level between (35 -45 mmHg), and inspiratory to expiratory times at a ratio 1:2.
• Measurements

• Hemodynamic parameters: HR and MAP.
• Respiratory mechanics: Peak airway pressure (Paw-peak) and Plateau pressure (Paw-plat).
• Oxygenation parameters: Partial arterial tension of oxygen (PaO2), PaO2/FiO2 ratio and oxygen saturation (SpO2).

All the previous measurements were recorded at the following time points: T0 (baseline value on room air), T5 (5 minutes after pneumoperitoneum), T30 (30 minutes after first RM), T6o (60 minutes after first RM), T90 (90 minutes after first RM), TE (20 minutes after the end of surgery on nasal cannula 3 L /min). Additional arterial blood gases analysis was performed in the PACU after 30 mins and 1 hr postoperatively.

• Serum interleukins (IL)-6 and (IL)-8, using enzyme-linked immunosorbent assay (ELISA) (Biosource, Biosite, Germany) in (pg/ml) were measured as baseline preoperative value and after 24 hr postoperatively. Validation of methods and degrees of concentrations was done following to the accompanied instructions.
• Postoperative pulmonary and non-pulmonary complication - (if any) - were assessed and reported in the PACU.
• Other variables like: duration of anaesthesia, duration of surgery, pneumoperitoneum time, number of patients needed vasopressors, length of ICU stay and hospital stay.

Inclusion criteria

• American Society of Anaesthesiologists physical Status classification scores of 1-2, scheduled for laparoscopic bariatric procedures

Exclusion criteria

• patients refusal,
• history of significant pulmonary disease (obstructive or restrictive),
• previous pneumothorax,
• significant cardiac dysfunction (arrhythmias ± unstable haemodynamics
• left ventricular ejection fraction < 40%)
• difficult intubation
• significant hepatic or renal impairment.