Long chain versus medium chain lipids in patients with ARDS: effects on pulmonary haemodynamics and gas exchange.

Objective: To compare pulmonary haemodynamic and gas exchange alterations in septic patients with ARDS receiving long-chain triglycerides (LCT) versus medium-chain triglycerides (MCT).

Design: Prospective, randomised, clinical study.

Setting: Surgical ICU patients in a University Hospital.

Patients: Twenty-one septic patients with ARDS were randomly assigned to receive 50 % of their non-protein caloric requirements as either 20 % LCT (group 1, n = 10) or 20% 1:1 mixture of LCT/MCT (group 2, n = 11).

Intervention: Intravenous infusion of LCT and LCT/MCT combinations at a rate of 12 g x h(-1).

Measurements And Results: The LCT infusion was associated with an increase of pulmonary venous admixture (Qva/Qt) from 24 % +/- 5 % to 37 % +/- 6 %, an increase of mean pulmonary artery pressure (MPAP) from 25 +/- 5 to 33 +/- 4 mmHg and decrease of PaO2/FIO2 from 240 +/- 30 to 180 +/- 35. LCT/MCT administration was only associated with an elevation of oxygen consumption (VO2) from 329 +/- 14 to 396 +/- 12 ml/ min. During lipid infusion group 1 patients presented higher Qva/Qt (37% +/- 6% vs 25% +/- 4%), MPAP (33 +/- 4 vs 27 +/- 3 mmHg) and VO2 (359 +/- 11 vs 396 +/- 12 ml/min) and lower PaO2/FIO2 (180 +/- 35 vs 235 +/- 30) values compared to group 2.

Conclusion: In conclusion, we have shown that, in septic patients with respiratory failure, LCT administration was associated with more significant changes of Qva/Qt, MPAP and PaO2/FIO2 compared to infusion of an LCT/MCT 1:1 emulsion. Clinically, these transient alterations might cause serious problems in patients with marginal arterial oxygenation and cardio-respiratory impairment.