Increased intracranial pressure.

Increased intracranial pressure. In this update, head
trauma has been removed as a relative contraindication to
ketamine while retaining the previous concerns relating to
central nervous system masses, abnormalities, or
hydrocephalus.
Repeated reports that ketamine can increase intracranial
pressure4,12,16,47-50 have prompted traditional caution against
use of this drug in any setting of real or potential neurological
compromise,1,4,12,16 and there are case reports of deterioration
in patients with hydrocephalus.51,52 However, newer suggestive
evidence indicates that in most patients the resulting pressure
increases are minimal, assuming normal ventilation,51,53-55 and
that ketamine’s corresponding cerebral vasodilatory effect may
actually improve overall cerebral perfusion.54,56 Given the
absence of any supportive or suggestive evidence that ketamine
presents a danger to the acutely traumatized brain, the historical
contraindication seems overreaching.54,56 However, alternative
agents would still appear preferable in patients with known
structural barriers to normal cerebrospinal fluid flow.
Seizure disorder. Ketamine demonstrates anticonvulsant
properties,4,12,16 and the literature is silent about any enhanced
risk with underlying seizure disorder.
Increased intraocular pressure. Dissociative sedation may
represent risk in patients with acute globe injury or glaucoma,
given inconclusive and conflicting evidence of increased
intraocular pressure with ketamine.57-61
Porphyria and thyroid disease. There are anecdotal reports
of enhanced sympathomimetic responses in patients with
porphyria,62,63 thyroid disorder,64 or thyroid medication,64 and
according to this inconclusive evidence, ketamine should be
used with caution in these settings.
Fasting state. There is insufficient evidence to recommend a
specific fasting duration before dissociative sedation. Despite 40
years of continual worldwide use, there are no documented
reports of clinically significant ketamine-associated aspiration,
except in ill neonates.4,12,16,65,66 A systematic review found no
apparent association of fasting state with emesis, laryngospasm,
or any other complication,4 and large, prospective ED series
have also failed to shown any association between fasting and
adverse effects.67-69
A case-by-case risk-benefit assessment is more consistent with the
current literature than setting an arbitrary fasting period.66 Indeed,
given its unique protection of airway reflexes, ketamine would appear
preferable to alternative sedatives when fasting is incomplete.65,66
Comorbidity. Regardless of age, patients with underlying
illness are widely regarded as having a greater risk of adverse events
with benzodiazepines, opioids, propofol, and inhalational
anesthetics.8-11 Such an association has not been similarly observed
with dissociative sedation in children.2,3,20,70 Indeed, the
cardiopulmonary support characteristics of ketamine would
appear to make this agent preferable to other procedural
sedation and analgesia agents in children with substantial