Pediatric emergency medicine trisk 3055 3055
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to 6 hours. By using a nearly continuous stream of fresh charcoal that descends
through the intestinal tract, a constant concentration gradient is maintained that
favors the back diffusion of free drug from periluminal capillary blood into the
intestinal lumen, where it may be bound immediately to the newer charcoal, so
the free drug concentration in the intestinal lumen remains low. In addition,
enterohepatic recirculation of some drugs may be interrupted as reabsorption
from bile is prevented. To be safe and effective, this technique requires active
peristalsis and an intact gag reflex or a protected airway. Common pediatric
poisonings for which repetitive charcoal dosing may be considered include
phenobarbital, carbamazepine, phenytoin, digoxin, salicylates, and theophylline.
Cathartics, such as sorbitol, should be administered no more frequently than
every third dose.
Renal Replacement Therapy
Renal replacement therapy is indicated for selected cases of severe poisoning to
enhance toxin clearance and correct severe acid–base or electrolyte disturbances.
High-flux hemodialysis is the modality of choice for expeditious toxin removal.
Other methods such as exchange transfusion, plasmapheresis and peritoneal
dialysis are much less effective in rapidly reversing the course of poisoning.
Hemoperfusion, the process of passing blood through a dialysis circuit containing
an adsorbent column, was historically used to remove higher–molecular-weight
substances that could not be extracted through standard dialysis but has become
obsolete since the arrival of newer high-flux dialysis membranes. Continuous
renal replacement therapy, such as continuous venovenous hemodiafiltration
(CVVHDF), also has much slower rates of toxin removal and should be reserved
for the hemodynamically unstable patient who cannot tolerate conventional HD.
Acute extracorporeal removal should be considered in light of patient- and
drug-related criteria. Patient-related criteria include (i) anticipated prolonged
coma with the high likelihood of attendant complications, (ii) development of
renal failure or impairment of normal excretory pathways, and (iii) progressive
clinical deterioration despite other medical therapy. Drug-related criteria are (i)
serum concentrations in the potentially fatal range of a dialyzable substance, (ii) a
correlation between serum drug concentration and toxicity, and (iii) anticipated
clinical benefit from faster toxin removal than what would be expected from
endogenous clearance. Dialysis is most useful for drugs with low volumes of
distribution (less than 1 L/kg), low–molecular-weight (less than 500 Da), and low
protein binding, including salicylic acid, methanol, ethylene glycol, lithium, and
theophylline. Other conditions which may be amenable to extracorporeal removal
