What is the role of ketamine as a primary induction agent?

From the Guidelines

Ketamine is a suitable primary induction agent, particularly in critically ill adults undergoing rapid sequence intubation, as it has a favorable hemodynamic profile and does not increase mortality or the incidence of hypotension or vasopressor use compared to other induction agents, as supported by the most recent guidelines from the Society of Critical Care Medicine 1.

Key Considerations

• The selection of a sedative-hypnotic agent that attenuates hypotension during rapid sequence intubation is desirable, and ketamine may be a reasonable option due to its quick onset and short duration of action, as well as its preservation of respiratory drive and sympathomimetic properties.
• A study published in 2023 found that there is no difference between etomidate and other induction agents, including ketamine, with respect to mortality or the incidence of hypotension or vasopressor use in the peri-intubation period and through hospital discharge 1.
• Ketamine's use in critically ill patients with depleted catecholamine stores may be a concern for hypotension and cardiac arrest, but its benefits in maintaining blood pressure and cardiac output make it a valuable option in certain situations.

Dosage and Administration

• The recommended induction dose of ketamine is 1-2 mg/kg IV given slowly over 60 seconds, with maintenance doses of 0.5-1 mg/kg as needed.
• For pediatric patients, doses of 1-2 mg/kg IV or 4-5 mg/kg IM are appropriate.

Potential Side Effects and Contraindications

• Ketamine can cause emergence phenomena, including hallucinations and dysphoria, which can be mitigated by pre-treatment with benzodiazepines (midazolam 0.03-0.05 mg/kg IV) 1.
• It should be used cautiously in patients with coronary artery disease, hypertension, increased intracranial pressure, or psychiatric disorders.
• Ketamine also increases salivation, so consider administering an antisialagogue like glycopyrrolate (0.2-0.4 mg IV) before induction.

From the FDA Drug Label

Ketamine hydrochloride is a general anesthetic indicated: as the sole anesthetic agent for diagnostic and surgical procedures that do not require skeletal muscle relaxation (1) for the induction of anesthesia prior to the administration of other general anesthetic agents (1) Ketamine hydrochloride has been studied in over 12,000 operative and diagnostic procedures, involving over 10,000 patients in 105 separate studies. During the course of these studies, ketamine hydrochloride was administered as the sole general anesthetic, as an induction agent prior to administration of other general anesthetics, or to supplement other anesthetic agents

The role of ketamine as a primary induction agent is to induce anesthesia prior to the administration of other general anesthetic agents. Key points about its use include:

• Induction of anesthesia: Ketamine can be used as the primary agent for inducing anesthesia.
• Surgical procedures: It is indicated for diagnostic and surgical procedures that do not require skeletal muscle relaxation.
• Administration: Ketamine can be administered as the sole general anesthetic or as an induction agent before other general anesthetics are given 2, 2.

From the Research

Role of Ketamine as a Primary Induction Agent

• Ketamine has been used as an induction agent for intubation without a paralytic and for the rapid, safe control of dangerously agitated patients 3.
• It is frequently used for general anesthesia in emergency medicine and is generally regarded as haemodynamically stable, although it can cause hypertension and tachycardia and may cause or worsen shock 4.
• The use of ketamine as an induction agent has been compared to other agents such as etomidate, with studies showing no significant difference in hemodynamic effects 5 or mortality 6.

Hemodynamic Effects

• Ketamine has been shown to produce hemodynamically stable anesthesia via central sympathetic stimulation without affecting respiratory function 7.
• A study comparing ketamine to etomidate for prehospital rapid sequence intubation found no difference in the incidence of hypotension or hemodynamic changes between the two groups 5.

Clinical Use

• Ketamine is commonly used in the hemodynamically unstable trauma patient, although it has been associated with side effects 6.
• The choice of ketamine as a rapid sequence induction agent in trauma patients may have an impact on survival, although studies have found no significant difference in mortality compared to other induction agents 6.
• Ketamine has also been used for the treatment of status epilepticus, alcohol withdrawal syndrome, and depression, with emerging evidence supporting its use in these conditions 3.