B. Tachyphylaxis [13]: rapid loss of drug effects caused by compensatory
neurophysiologic mechanisms due to exhaustion of synaptic neurotransmitters^
C. Dependence^ [13]: physiologic and biochemical adaptation of neurons, such
that removing a drug precipitates withdrawal, which generally occurs after 2- 3
weeks of continuous use.^
D. Withdrawal [13] clinical syndrome that develops after stopping or reversing
a drug after prolonged exposure to that drug.
Symptoms are evident within 24 hours of drug cessation and peak
within 72 hours.
Symptoms of opioid withdrawal include cramping, vomiting,
diarrhea, tachycardia, hypertension, diaphoresis, restlessness,
insomnia, movement disorders, reversible neurologic
abnormalities, and seizures
Opioid withdrawal occurs over 50% of PICU patients and in 60%
of all PICUs. Risk of withdrawal is over 50% after 5 days of
continuous infusion or around the clock administration of an
analgesic or sedative. Withdrawal can complicate medical
treatment, increase morbidity, as well as prolong hospitalization.
There is no gold standard tool to measure withdrawal symptoms,
however one tool that has been validated in children is
Withdrawal assessment tool (WAT-1) (Table 5).