“…Case‐specific confounders included: surgical specialty; emergency surgery; duration of surgery; work relative value units; and high‐risk surgery, that is, neurosurgery, general, transplant, thoracic, vascular or burns [20]. The following intra‐operative factors were also included in the adjusted analysis [17]: administration of long‐ and short‐acting intravenous opioids (dose expressed as total oral morphine equivalents); use of adjunct analgesic or sedative medications (ketamine, dexmedetomidine, regional anaesthesia); age‐adjusted MAC of nitrous oxide; use of neuromuscular blocking (non‐depolarising and succinylcholine) and reversal agents (neostigmine and sugammadex); total volume of intravenous fluids administered; red blood cell transfusion and vasopressor requirements; duration of intra‐operative hypotension, that is, mean arterial pressure < 55 mmHg; airway device, that is, tracheal tube and/or supraglottic airway; and ventilation parameters, that is, median F I O2, median positive end‐expiratory pressure (PEEP), median peak inspiratory pressure (PIP), weight‐adjusted tidal volume, S p O 2 /F I O 2 ratio and use of a non‐protective ventilation strategy. Non‐protective ventilation strategy was defined as either median PEEP = 0 cmH 2 O or median PEEP > 15 cmH 2 O, median PIP > 35 cmH 2 O; or median tidal volume > 10 ml.kg −1 ) [21].…”