Anesthesia Student Survival Guide.pdf - Index of

300 ● AnesthesiA student survivAl Guide
though in practice, brain water and blood volume are the most amenable
to intervention. Ventriculostomy tubes are sometimes placed by neurosurgeons
preoperatively to drain CSF. Blood volume can be reduced by elevating
the head of the bed about 30 degrees. Hyperventilation to PaCO 2 =30 mm
Hg can reduce cerebral blood flow but this maneuver is controversial in the
setting of head trauma and elevated ICP, because it may worsen ischemia in
vulnerable areas. Similarly, lowering the blood pressure, though reducing
the tendency to bleed and expand the hematoma, may compromise cerebral
perfusion pressure in vulnerable brain regions. Reducing brain water by
administration of mannitol is sometimes used as well, although more frequently
after induction. However, in cases of vascular disruption, extravasation
of mannitol may actually worsen ICP.
What other considerations are there in deciding how you will induce
anesthesia?
The patient had eaten just before his injury and thus has a “full stomach”
as well as a “tight head.” This usually indicates a rapid sequence induction
of anesthesia and use of succinylcholine. Because one does not ventilate the
patient prior to intubation, PaCO 2 may rise and CBF may increase, particularly
if laryngoscopy is difficult. An airway examination, if possible in
this obtunded patient, is important. Also, succinylcholine may transiently
increase ICP; some have suggested avoiding it for this reason, though no
data supports omitting it.
Given all of the above considerations, what drugs will you choose for induction
of anesthesia?
There is likely no ideal induction sequence. A reasonable approach is careful
preoxygenation and rapid sequence induction with thiopental and succinylcholine,
followed by normocapnic ventilation and maintenance of blood
pressure close to preoperative levels. Only if there are clinical indications
that ICP is worsening would you consider hyperventilation, changing the
blood pressure, or other maneuvers.
What will you do if you are unsuccessful in intubating him?
Your choices are to continue with apneic attempts at intubation with
alternative airway devices or ventilation to preserve normocapnia.