Page 74 - Clinical Application of Mechanical Ventilation

40 Chapter 2

GASTROINTESTINAL CONSIDERATIONS

Positive pressure ventilation is associated with many organ-system complications,
gastrointestinal (GI): Organ
system including the stomach and one of which involves the gastrointestinal (GI) tract. GI complications in patients
intestines. who are being mechanically ventilated include erosive esophagitis, stress-related
mucosal damage (SRMD), diarrhea, decreased bowel sounds, high gastric residu-
als, and constipation (Mutlu et al., 2000). These conditions are likely caused by
GI complications may a decrease of perfusion to the GI tract and medications commonly used during
be caused by a decrease of
perfusion to the GI tract and mechanical ventilation. Morphine sulfate is a medication commonly used for pain
medications that are com- control. Some of the GI side effects of morphine include constipation and vomiting.
monly used in mechanically
ventilated patients. Table 2-8 summarizes the factors that may adversely affect the normal GI functions
(Mutlu et al., 2001).

NUTRITIONAL CONSIDERATIONS

Malnutrition in critically ill patients can create muscle fatigue, ventilatory insuf-
ficiency, and ventilatory failure. This sequence of events can lead to a need for
mechanical ventilation. It can also make weaning from mechanical ventilation
difficult or unsuccessful. Adequate nutritional support is therefore essential in
the management of critically ill patients. However, excessive nutritional support
is undesirable since it may cause excessive carbon dioxide production, as well as
increased work of breathing in order to eliminate excessive CO (van den Berg &
2
Stam, 1988).

TABLE 2-8 Major Factors Adversely Affecting Normal GI Functions

Factors Notes

Mechanical ventilation Increased intrathoracic pressure
(especially with high levels Increased right atrial pressure
of PEEP) Reduced pressure gradient between mean systemic
venous and right atrial pressures
Reduced cardiac output and GI perfusion

Splanchnic hypoperfusion Due to decreased mean arterial pressure and/or in-
creased resistance in the GI vascular bed
May lead to stress-related mucosal damage (SRMD)

Medications (e.g., opiates, sedatives, Decreased GI motility
vasopressors, antibiotics) Impaired venous return via venodilation and/or
diminution of response to vasopressors
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