Ketamine

When used for procedural sedation for major procedures involving the posterior pharynx (eg, endoscopy) or when used for patients with an active pulmonary infection or disease (including upper respiratory disease or asthma), the use of ketamine increases the risk of laryngospasm. Patients with a history of airway instability, tracheal surgery, or tracheal stenosis may be at a higher risk of airway complications. The American College of Emergency Physicians considers these situations relative contraindications for the use of ketamine (ACEP [Green 2011]). The manufacturer recommends against the use of ketamine alone in surgery or diagnostic procedures of the pharynx, larynx, or bronchial tree; mechanical stimulation of the pharynx should be avoided, whenever possible, if ketamine is used alone.

May cause CNS depression, which may impair physical or mental abilities; patients must be cautioned about performing tasks that require mental alertness (eg, operating machinery, driving). When used for outpatient surgery, the patient should be accompanied by a responsible adult. Driving, operating hazardous machinery, or engaging in hazardous activities should not be undertaken for ≥24 hours after anesthesia, according to the manufacturer.

May cause dependence (withdrawal symptoms on discontinuation) and tolerance with prolonged use. A withdrawal syndrome with psychotic features has been described following discontinuation of long-term use.

Postanesthetic emergence reactions, which can manifest as vivid dreams, hallucinations, and/or frank delirium, occur; these reactions are less common in patients 65 years and when given IM (White 1982). Emergence reactions, confusion, or irrational behavior may occur up to 24 hours postoperatively and may be reduced by pretreatment with a benzodiazepine, use of ketamine at the lower end of the dosing range, and minimizing verbal and tactile stimulation of the patient during the recovery period. Avoid use in patients with schizophrenia; may exacerbate psychotic symptoms (Lahti 1995; Malhotra 1997). The American College of Emergency Physicians considers the use of ketamine in patients with known or suspected schizophrenia (even if currently stable or controlled with medications) an absolute contraindication (ACEP [Green 2011]).

Some consider the use of ketamine in patients with CNS masses, CNS abnormalities, or hydrocephalus a relative contraindication due to multiple reports that ketamine may increase intracranial pressure in these patients (ACEP [Green 2011]). However, assuming adequate ventilation, some evidence suggests that ketamine has minimal effects on intracranial pressure and may even improve cerebral perfusion and reduce intracranial pressure (Albanese 1997; Bowles 2012; Zeiler 2014).

Use with caution in patients with increased intraocular pressure (IOP). Some recommend avoiding use in patients with an open eye injury or other ophthalmologic disorder where an increase in IOP would prove to be detrimental; however, the effects of ketamine on IOP is mixed with some evidence demonstrating no clinically significant effect on IOP (ACEP [Green 2011]; Cunningham 1986; Drayna 2012; Miller 2010; Nagdeve 2006).

The American College of Emergency Physicians considers the use of ketamine in patients with porphyria a relative contraindication due to enhanced sympathomimetic effect produced by ketamine (ACEP [Green 2011]).

Rapid IV administration or overdose may cause respiratory depression or apnea. Resuscitative equipment should be available during use.

The American College of Emergency Physicians considers the use of ketamine in patients with a thyroid disorder or receiving a thyroid medication a relative contraindication due to enhanced sympathomimetic effect produced by ketamine (ACEP [Green 2011]). Disease-related concerns:

Use with caution in patients with coronary artery disease, catecholamine depletion, hypertension, and tachycardia. Cardiac function should be continuously monitored in patients with increased blood pressure or cardiac decompensation. Ketamine increases blood pressure, heart rate, and cardiac output thereby increasing myocardial oxygen demand. The mechanism by which ketamine causes a sympathetic surge to stimulate the cardiovascular system has yet to be elucidated. The use of concurrent benzodiazepine, inhaled anesthetics, and propofol or administration of ketamine as a continuous infusion may reduce these cardiovascular effects (Miller 2010). The American College of Emergency Physicians recommends avoidance in patients who are already hypertensive and in older adults with risk factors for coronary artery disease (ACEP [Green 2011]). In a scientific statement from the American Heart Association, ketamine has been determined to be an agent that may exacerbate underlying myocardial dysfunction (magnitude: major) (AHA [Page 2016]).

Use with caution in patients with CSF pressure elevation; an increase in CSF pressure may be associated with use.

Use with caution in the chronic alcoholic or acutely alcohol-intoxicated. Concurrent drug therapy issues:

Potentially significant interactions may exist, requiring dose or frequency adjustment, additional monitoring, and/or selection of alternative therapy. Consult drug interactions database for more detailed information. Special populations:

In pediatric and neonatal patients Other warnings/precautions:

Use requires careful patient monitoring, should only be used by experienced personnel who are not actively engaged in the procedure or surgery. If used in a nonintubated and/or nonmechanically ventilated patient, qualified personnel and appropriate equipment for rapid institution of respiratory and/or cardiovascular support must be immediately available. Use to induce moderate (conscious) sedation in patients warrants monitoring equivalent to that seen with deep anesthesia. Consult local regulations and individual institutional policies and procedures.