Page 1053 - Basic _ Clinical Pharmacology ( PDFDrive )

CHAPTER 58 Management of the Poisoned Patient 1039

A For example, determination of the acetaminophen level is useful
in assessing the need for antidotal therapy with acetylcysteine.
Serum levels of salicylate (aspirin), ethylene glycol, methanol, the-
ophylline, carbamazepine, lithium, valproic acid, and other drugs
and poisons may indicate the need for hemodialysis (Table 58–2).
B
Decontamination
Decontamination procedures should be undertaken simultane-
C ously with initial stabilization, diagnostic assessment, and labora-
tory evaluation. Decontamination involves removing toxins from
the skin or gastrointestinal tract.

A. Skin
FIGURE 58–1 Changes in the electrocardiogram in tricyclic Contaminated clothing should be completely removed and
antidepressant overdosage. A: Slowed intraventricular conduction
results in prolonged QRS interval (0.18 seconds; normal, 0.08 seconds). double-bagged to prevent illness in health care providers and for
B and C: Supraventricular tachycardia with progressive widening possible laboratory analysis. Wash contaminated skin with soap
of QRS complexes mimics ventricular tachycardia. (Reproduced, with and water.
permission, from Benowitz NL, Goldschlager N: Cardiac disturbances. In: Haddad LM,
Shannon MW, Winchester JF [editors]. Clinical Management of Poisoning and Drug B. Gastrointestinal Tract
Overdose, 3rd ed. WB Saunders, 1998. © Elsevier.) Controversy remains regarding the efficacy of gastrointestinal
decontamination, especially when treatment is initiated more than
1 hour after ingestion. For most ingestions, clinical toxicologists
lithium, and arsenic (see also https://www.crediblemeds.org/ recommend simple administration of activated charcoal to bind
everyone/composite-list-all-qtdrugs/). Variable atrioventricular ingested poisons in the gut before they can be absorbed (as in
(AV) block and a variety of atrial and ventricular arrhythmias are the case study). In unusual circumstances, gastric lavage or whole
common with poisoning by digoxin and other cardiac glycosides. bowel irrigation may also be used.
Hypoxemia due to carbon monoxide poisoning may result in
ischemic changes on the electrocardiogram.

F. Imaging Findings TABLE 58–2 Hemodialysis in drug overdose and
A plain film of the abdomen may be useful because some tab- poisoning. 1
lets, particularly iron and potassium, may be radiopaque. Chest Hemodialysis may be indicated depending on the severity of
radiographs may reveal aspiration pneumonia, hydrocarbon pneu- poisoning or the blood concentration:
monia, or pulmonary edema. When head trauma is suspected, a Carbamazepine
computed tomography (CT) scan is recommended.
Ethylene glycol
Toxicology Screening Tests Lithium
Methanol
It is a common misconception that a toxicology “screen” is the best
way to diagnose and manage an acute poisoning. Unfortunately, Metformin
rapid urine “drugs of abuse” screens are limited to a few classes Phenobarbital
of drugs and are subject to many false-positive and false-negative Salicylate
results, and more reliable comprehensive toxicology screening is Theophylline
time-consuming and expensive and results of tests may not be avail- Valproic acid
able for days. Moreover, many highly toxic drugs such as calcium Hemodialysis is ineffective or is not useful:
channel blockers, β blockers, and isoniazid are not included in
the screening process. The clinical examination of the patient and Amphetamines
selected routine laboratory tests are usually sufficient to generate a Antidepressants
tentative diagnosis and an appropriate treatment plan. Although Antipsychotic drugs
screening tests (so-called “drugs of abuse” panels) may be helpful in Benzodiazepines
confirming a suspected intoxication, they should not delay needed Calcium channel blockers
treatment. More formal, comprehensive screening may be necessary
in cases of suspected brain death (to rule out drugs as a cause of Digoxin
coma), child abuse, or as part of a postmortem examination. Metoprolol and propranolol
When a specific antidote or other treatment is under Opioids
consideration, quantitative laboratory testing may be indicated. 1 This listing is not comprehensive.