Page 441 - Clinical Application of Mechanical Ventilation

Management of Mechanical Ventilation 407

energy in fat emulsion is preferred for fluid-restricted patients. A fat-based diet
also reduces carbon dioxide production and ventilatory requirements (Mlynarek
et al., 1987).
For this reason, an increase in fat kilocalories with a concurrent decrease in carbo-
hydrate (dextrose) intake has been done to maximize energy intake and to minimize
oxygen utilization and carbon dioxide production. The fat-based diet should con-
tain at least 40% total fat kilocalories and it should be based on the patient’s clini-
cal status, because a metabolically stressed patient may become immunosuppressed
because of insufficient fat in the diet (Ideno et al., 1995).
In one study, a high-calorie diet consisting of 28% carbohydrate, 55% fat, and
A low-carbohydrate balanced protein resulted in significantly lower CO production and arterial PCO
high-fat diet may maximize 2 2
energy intake and minimize in COPD patients with hypercapnia. Furthermore, two important lung function
oxygen utilization and carbon
dioxide production. measurements (forced vital capacity and forced expiratory volume in 1 sec) improved
by 22% over baseline values with this low-carbohydrate, high-fat diet (Angelillo
et al., 1985).

Total Caloric Requirements

Energy requirements for the critically ill patient are commonly done by using the
Harris-Benedict equation (Roza et al., 1984). This equation can be used to estimate
a patient’s resting energy expenditure (REE) and total energy expenditure (TEE).
For an accurate measurement of a patient’s energy requirement (REE and TEE),
metabolic testing should be done.
REE is the minimum energy requirement for basic metabolic needs. TEE is the
energy requirement based on a patient’s disease state in which the metabolic rate is
higher than normal. TEE is the product of REE and the activity/stress factors (TEE 5
REE 3 Activity 3 Stress Factors). These factors are used to make allowances for hyper-
metabolic or hypercatabolic conditions such as activity, trauma, infection, and burns.
For ventilator-dependent patients, the TEE is calculated by multiplying the REE by
factors ranging from 1.2 to 2.1 as shown in Table 12-19 (Askanazi et al., 1982; Roza
et al., 1984).

Phosphate Supplement

The incidence of phosphate deficiency or hypophosphatemia is high in certain
subgroups of patients. It occurs in about 30% of patients admitted to the ICU,
65% to 80% of patients with sepsis, 75% of patients with major trauma, and
21.5% of patients with COPD (Brunelli et al., 2007). In addition to the total
caloric requirement, a patient’s nutritional program should maintain a balanced

Hypophosphatemia (se- serum phosphate level. Insufficient phosphate in a patient’s diet may cause
rum phosphate level ,1 mg/ hypophosphatemia, a condition where the serum phosphate level is less than
dL) in severe form may cause
the patient to experience 1 mg/dL. Hypophosphatemia decreases tissue adenosine triphosphate (ATP)
confusion, muscle weakness, level, and in severe form it may cause the patient to experience confusion,
congestive heart failure, and
respiratory failure. muscle weakness, congestive heart failure, and respiratory failure (Mlynarek
et al., 1987).

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