Does ketamine alter respiratory drive?

From the Guidelines

Ketamine generally preserves respiratory drive, which is one of its key advantages over other anesthetic and sedative medications, as it typically maintains spontaneous breathing and protective airway reflexes at standard clinical doses. This is supported by the most recent and highest quality study, which states that dissociative sedation with ketamine is characterized by retention of protective airway reflexes, spontaneous respirations, and cardiopulmonary stability 1.

Key Points

• Ketamine works through NMDA receptor antagonism, which does not significantly depress respiratory function, unlike opioids, benzodiazepines, and propofol that enhance GABA activity or affect opioid receptors.
• The use of ketamine is particularly valuable in emergency settings, battlefield medicine, and when managing patients with asthma or other respiratory conditions where maintaining spontaneous ventilation is crucial.
• However, caution is still warranted as very high doses of ketamine, rapid IV administration, or combination with other sedatives can potentially compromise respiratory function, and ketamine increases secretions in the airways, which may complicate airway management in some patients.
• Having airway equipment available remains important, particularly when combining ketamine with other sedatives, and IV ketamine should typically be administered over at least 30 seconds to avoid transient respiratory depression and apnea 1.

Clinical Considerations

• The preservation of respiratory drive with ketamine makes it a preferred option for procedural sedation in patients with respiratory concerns.
• Ketamine's ability to maintain spontaneous breathing and protective airway reflexes reduces the risk of respiratory complications compared to other sedative medications.
• Clinicians should be aware of the potential risks and take necessary precautions when using ketamine, especially in high-risk patients or when combining it with other sedatives.

From the FDA Drug Label

Respiratory disorders: Respiratory depression and apnea following rapid intravenous administration of high doses of ketamine hydrochloride; laryngospasm, and airway obstruction.

Ketamine can alter respiratory drive, potentially causing respiratory depression and apnea, especially when administered rapidly in high doses. Key points to consider:

• Respiratory depression is a possible adverse reaction associated with ketamine use.
• Apnea can occur, particularly with rapid intravenous administration of high doses.
• Laryngospasm and airway obstruction are also potential respiratory complications. 2, 2, and 2 all support the idea that ketamine can have significant effects on respiratory function, particularly in certain contexts such as high doses or rapid administration.

From the Research

Effects of Ketamine on Respiratory Drive

• Ketamine has been shown to provide analgesia and amnesia without causing hypotension or respiratory depression, unlike other sedatives 3.
• A study in rats found that ketamine anesthesia was associated with markedly increased genioglossus activity and a respiratory stimulating effect, with higher values of flow rate, respiratory rate, and duty-cycle 4.
• Ketamine is a respiratory stimulant that abolishes the coupling between loss-of-consciousness and upper airway dilator muscle dysfunction in a wide dose-range 4.
• Research has demonstrated that ketamine produces an anesthetic state characterized by profound analgesia, preserved pharyngeal-laryngeal reflexes, normal or slightly enhanced skeletal muscle tone, cardiovascular and respiratory stimulation, and occasionally a transient and minimal respiratory depression 5.
• Ketamine has been shown to have analgesic and sedating properties without having a detrimental impact on hemodynamics, making it an attractive sedative for patients with acute respiratory distress syndrome 6.
• Ketamine produces hemodynamically stable anesthesia via central sympathetic stimulation without affecting respiratory function 7.

Clinical Implications

• The use of ketamine as a sedative may reduce the necessity for other sedatives and vasopressors in patients requiring deep sedation for acute respiratory distress syndrome 6.
• Ketamine may have a role in reducing opioid consumption and chronic postsurgical pain after specific surgical procedures 7.
• The safety and efficacy of ketamine in various clinical settings, including intensive care unit and emergency department settings, have been demonstrated 3, 5.