Factors which need to be taken into account when measuring resting energy expenditure in a mechanically ventilated patient:
(1) hemodynamic instability (with need for fluid resuscitation and inotropic support)
(2) respiratory instability (with hypoxemia or change in respiratory mechanics)
(3) variation in the carbon dioxide pool (from infusion of bicarbonate, urinary or GI loss, dialysis, etc)
(4) thermogenesis from administered carbohydrates and other nutrients
(5) air leaks in the ventilatory system
(6) accumulation of ketones and other intermediate metabolites
(7) very high FIO2 (> 80%)
The
total
energy expenditure needs to take into account factors resulting in increased energy expenditures (febrile illness or inflammation, surgery, malignancy, trauma, etc) above the resting energy expenditure.
