Page 1725 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

1194 PART 11: Special Problems in Critical Care

patients has been identified as a “special situation” by the American
• Treatment is supportive and includes benzodiazepines for symp- Heart Association. Their recommendations in the 2010 Guidelines for
tomatic control. Cyproheptadine has been used without convincing Cardiopulmonary Resuscitation and Emergency Cardiovascular Care
experimental evidence supporting its use. are included in this chapter. 2
With cervical spine precautions in place (unless trauma has been
Envenomations reasonably excluded), airway patency must be established. In obtunded
• The majority of poisonous snake bites in the United States involve patients with spontaneous respirations and without signs of facial
the Crotalidae or pit viper family of snakes (eg, rattlesnakes, trauma, a nasal trumpet is acceptable to assist in oxygen delivery. An
copperheads, and water moccasins). oral airway may be used to facilitate bag-mask ventilation prior to endo-
• Treatment of rattlesnake bite consists of immobilizing the bitten tracheal intubation in patients without a gag reflex. The choice of airway
extremity below the level of the heart. Surgical consultation may depends on the level of obtundation, the vigor of protective reflexes, the
be required for local wound management. degree of respiratory depression, and initial response to pharmacologic
• Unstable patients with pit viper envenomation should be treated therapy (Table 124-1).
Patients with an adequate airway and intact protective reflexes may
with equine Crotalidae antivenin. Any patient with confirmed not require intubation (even if they are lethargic), particularly if treat-
Elapidae bite should be treated with antivenin, as symptoms may
be delayed and life threatening. ment improves mental status. Intubation is indicated when a patient is
unable to protect the airway, clear secretions, maintain gas exchange, or
• In North America, only the widow spiders (Latrodectus species) sustain an adequate blood pressure. Intubation decreases but does not
and the recluse spiders (Loxosceles species) are medically important. eliminate the risk of aspiration, which occurs in approximately 10% of
• Features of black widow spider bite include local pain and erythema comatose patients with drug overdose. Intubation further allows for
3,4
followed by muscle cramps and fasciculations that may generalize administration of high concentrations of oxygen and, in some patients,
to the abdomen, back, and chest. Hypertension, tachycardia, tremor, provides access for drug delivery.
fever, agitation, diaphoresis, and nausea are common. Selected causes of hypoxemia in drug overdose and toxic ingestion
• Treatment of black widow spider bite consists of supportive measures, are listed in Table 124-2. Hypoxemia must be corrected quickly to avoid
analgesia, and sedation, and in severe cases, equine-derived antivenin. anoxic brain injury, myocardial ischemia, and arrhythmias. In some
• Recluse spider bite (loxoscelism) is characterized by localized poisonings (eg, carbon monoxide, cyanide, and methemoglobinemia), a
) of 1.0 is therapeutic, whereas in para-
swelling, erythema, and formation of bullae, often forming a fraction of inspired oxygen (Fi O 2
quat poisoning and bleomycin toxicity, oxygen potentiates lung injury.
“bull’s eye” lesion with central necrosis. Some patients develop The clinician should choose a ventilator mode with which she or
fever, myalgias, headache, and nausea. Rare patients develop he is familiar and which achieves the greatest degree of synchrony
intravascular hemolysis, disseminated intravascular coagulopathy, between patient and machine. The initial ventilator mode should pro-
acute renal failure, and the acute respiratory distress syndrome. vide adequate back-up minute ventilation (which can be achieved with
Treatment is supportive, but antivenin is selectively available. either assist control or synchronized intermittent mandatory ventilation
with pressure support). If intubation is performed solely to protect the
airway or to provide supplemental oxygen, the endotracheal tube may
In their 2008 annual report, the American Association of Poison Control be connected to a T-piece. Alternatively low levels of pressure support
Centers reported 2,491,049 human toxic exposure cases. Four percent ventilation (5 to 8 cm H O) can be applied to overcome endotracheal
2
of these cases, or more than 93,000 patients, required critical care. tube resistance and decrease inspiratory work of breathing. Positive
There were 1315 fatalities, associated most commonly with prescription end-expiratory pressure (PEEP) recruits atelectatic and fluid-filled
pharmaceuticals. 1 alveoli, but should be used cautiously in hypotensive patients to avoid
Intentional overdose or accidental exposure may be the chief com- decreasing cardiac preload. Special attention must be paid to the
plaint at the time of initial evaluation, but not all patients provide this acid-base status in the poisoned patient on mechanical ventilation (as
information, particularly when toxin or trauma clouds mental status. In discussed separately in the section “Salicylates”).
these cases, signs and symptoms may be attributed to another disorder Circulatory manifestations of drug overdose are common and varied.
and poisoning remains obscure. In the hospital, inappropriate drug Bradycardia and/or atrioventricular (AV) block can result from
dosing or unforeseen drug interactions may lead to toxic side effects.
Classic features of overdose, referred to as a toxidrome, help establish
a diagnosis, but signs and symptoms may be nonspecific or lacking alto- TABLE 124-1 Initial Pharmacologic Treatment of Patients With Altered Mental Status
gether, as in the early stages of acetaminophen overdose. The protean
manifestations of intoxication mandate a high index of suspicion in Drug Dose Comment
critically ill patients. Oxygen 1.0 for carbon Oxygen may increase risk of
Treatment of the poisoned patient often occurs before a diagnosis has Titrate to Sp O 2 >92%; Fi O 2 pulmonary toxicity in paraquat
monoxide and cyanide toxicity
been established. Most important in this regard are standard supportive intoxication
measures. The ABCDs (airway, breathing, circulation, and differential
diagnosis/decontamination) come first while efforts ensue to confirm Dextrose 50 g IV Antidote for oral hypoglycemic
intoxication and initiate targeted therapy. or insulin overdose
In this chapter, we will review (1) initial supportive efforts, (2) diagnosis Thiamine 100 mg IV Used to prevent Wernicke
of poisoning and drug overdose, (3) techniques to limit drug absorption encephalopathy; rare anaphylac-
and enhance drug elimination, and (4) specific treatments of the most toid reactions have been reported
commonly encountered drugs, toxins, and envenomations seen in the Naloxone 0.2-0.4 mg IV initial dose; if no clinical response Short duration of action
intensive care unit. after 2-3 minutes, an additional 1-2 mg IV (approximately 20-60 minutes)
may be administered to a total dose of 10 mg; requires repeat dosing or
INITIAL SUPPORTIVE MEASURES higher doses may be required in meperidine continuous infusion
Primary physician responsibilities are to identify and treat life-threatening or propoxyphene overdose; in opioid-addicted
problems. The general guidelines of life support should be followed as patients, lower doses (0.1-0.2 mg) may help
in any medically unstable patient, but the care of critically ill poisoned without causing drug withdrawal

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