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Pharmacotherapy for Mechanical Ventilation 447

TABLE 13-19 Clinical Signs of Inadequate Pain Control

Tachycardia in the absence of hypoxemia

Blood pressure changes

Dilated pupils
Diaphoresis

Grimacing
Restlessness

Guarding
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Agents for Seizures and Elevated Intracranial

Pressure (Barbiturates)

Barbiturates, once widely used in critically ill patients for sedation and anxiolysis,
barbiturates: A group of drugs
that depresses the central nervous have limited applications in patients on mechanical ventilation because of respira-
system. Adverse effects are many, tory and cardiovascular depression. For sedative action, they have been replaced by
including alteration of the respira-
tion, heart rate, blood pressure, safer drugs such as benzodiazepines. Barbiturates may be preferred in certain situ-
and temperature. They are used ations, such as seizure disorders, control of elevated intracranial pressure (normal
in seizure disorders, control of
elevated intracranial pressure. ICP 8 to 12 mm Hg, ,20 mm Hg in clinical practice).
Table 13-20 lists the selected barbiturates that are used in different situations
because of the wide range of duration of action, ranging from ultrashort-acting
(0.2 hour) to long-lasting (4 to 12 hours).

TABLE 13-20 Selected Barbiturates

Names Duration of Action Duration of Hypnotic* Effect

Thiopental Ultrashort-acting 0.2 hour
Methohexital
Pentobarbital Short-acting 1 to 4 hours

Amobarbital Intermediate-acting 2 to 8 hours

Phenobarbital Long-acting 4 to 12 hours
*The anesthetic dose is about three times the hypnotic dose; the lethal dose is about six times the hypnotic dose
(Cottrell et al., 1995; Ziment, 1978).
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