ARDS on day 2 after laparotomy — define by Berlin, set the ventilator, prone and dry

Model answer

(A) Moderate ARDS by Berlin — with overload, collapse, cardiac and embolism still to exclude (3 marks). A 2011 consensus panel built three mutually exclusive hypoxemia categories, and her P/F 138 sits in the moderate band (100-200) whose mortality is 32% against 27% mild and 45% severe.^[1] She meets timing (postoperative), bilateral opacities and non-cardiac pattern — but with +6.5 L and CVP 14, still exclude fluid-overload edema (echo, volume response), lobar atelectasis (the dominant postoperative pulmonary complication, of uncertain significance), cardiac failure and pulmonary embolism before labelling ARDS — postoperative ARDS is common (42% of intubated ARDS) yet mimics dominate the early film.^[20]

(B) 6 mL/kg predicted weight, plateau 30 ceiling, minimise driving pressure (4 marks). Reset volumes from 10 mL/kg actual to 6 mL/kg predicted body weight with plateau capped at 30 cm H2O: ARDSNet (861 patients, 12 vs 6 mL/kg with plateau 50 vs 30) cut death from 39.8% to 31.0% and added ventilator-free days (12 vs 10).^[3] Then minimise driving pressure (plateau minus PEEP): it stratified risk best of all ventilation variables, with a 7 cm H2O rise carrying relative risk 1.41 even under protective settings — VT or PEEP changes count only through driving-pressure reduction.^[15] Never offer HFOV as the alternative: OSCILLATE stopped at 548/1200 with 47% versus 35% death.^[17]

(C) Prone, dry, dexamethasone, rescue thresholds (3 marks). Prone now in sessions of at least 16 hours — PROSEVA entry matches her (P/F below 150 on FiO2 0.6+ with PEEP 5+), with 28-day death 16.0% versus 32.8% (HR 0.39) and no excess complications.^[4] Run conservative fluids now shock has resolved: FACTT added ventilator-free days (14.6 vs 12.1) without extra shock or dialysis, and the 244-patient surgical subgroup gained ventilator-free (15 vs 13) and ICU-free days with no renal cost.^[12][14] Start dexamethasone 20 mg IV daily for 5 days then 10 mg for 5 days in this established moderate disease — 60-day death 21% versus 36% with balanced harms.^[11] If she deteriorates to very-severe thresholds (P/F below 50 for 3+ hours, below 80 for 6+ hours, or acidemia with hypercapnia), refer to an ECMO centre by EOLIA criteria rather than improvising rescue.^[5]