Intrahospital Transport
Intrahospital transport of critically injured patients in need
of surgical intervention or diagnostic workup is a frequent part of anesthesiology
practice. The ASA,[245]
the American College of
Surgeons Committee on Trauma,[8]
and the Society
of Critical Care Medicine[246]
all have guidelines
for the transport of critically ill patients. All three guidelines state that the
level of care during transport should be equal to
or exceed the level of care that the patient is receiving before
transport.
Patients being transported may experience significant changes
in heart rate, BP, oxygenation, CO2
exchange, and dysrhythmias.[247]
Cardiovascular instability during transport may actually be the result of respiratory
changes. Braman and Branson suggested that potentially lethal hemodynamic changes
during transport occur as a result of blood gas abnormalities.[248]
Their study investigated 36 patient transports, approximately half with manual ventilation
and the other half with portable volume ventilation. They found a significant incidence
of hypercapnia and acidemia that led to the hemodynamic complications of hypotension
and cardiac dysrhythmias. Most of these changes were seen in the manual ventilation
group, which prompted their recommendation for transport with a portable ventilator.
A study by Weg and Haas examined 20 ICU patients who were transported with manual
ventilation. These authors demonstrated that if the transport personnel can approximate
during transport the inspired FIO2
and
minute ventilation that the patient was receiving from the ICU ventilator before
transport, no hemodynamic changes and no significant changes in blood gas measurements
occurred.[249]
Changes in respiratory compliance may develop during transport
and place the patient at risk for barotrauma or volutrauma. Patients ventilated
with pressure modes of ventilation should have a continuous reading of expiratory
tidal volume displayed; a significant decrease in tidal volume should alert the clinician
to a possible pneumothorax or expanding hemothorax. Similarly, in volume modes of
ventilation, a display of peak inspiratory pressure may signal these pathologies
if a sudden increase in this value occurs. A patient with severe respiratory failure
and elevated ICP is uniquely challenging. Maneuvers to minimize ventilator-associated
lung injury (decreased tidal volume, high MAP with limited peak inspiratory pressure)
lead to concerns of a resultant elevation in ICP. If a patient is transported during
the period of maximal postinjury edema (generally days 3 to 5), minor perturbations
or mere environmental stimulation may increase ICP.[250]
Because both hypoxemia and hypotension have been shown to correlate with poor outcome
in head-injured patients, these conditions should be actively avoided during transport.
Normocapnia should be maintained. In addition, drugs to treat transient elevations
in ICP (narcotics, sedatives, benzodiazepines, barbiturates, hypertonic saline, mannitol)
should be available during transport.
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