Ketamine Use in Patients on BiPAP: Exercise Extreme Caution
Ketamine can be used for sedation in patients on BiPAP, but this represents a high-risk scenario requiring immediate airway management readiness, as ketamine can cause apnea even at low doses in critically ill patients with respiratory failure. 1
Critical Safety Considerations
Respiratory Depression Risk in BiPAP Patients
Apnea has been documented after low-dose ketamine (0.31 mg/kg IV) in a patient with acute hypoxic respiratory failure who was being prepared for noninvasive positive-pressure ventilation, with complete loss of respiratory effort occurring within one minute of administration. 1
While ketamine traditionally preserves respiratory drive and airway reflexes better than other sedatives, this protective effect may not apply to critically ill patients with respiratory failure. 2
In trauma analgesia settings, assisted ventilation was required in 0.05% of ketamine-treated patients, though this rate was comparable to other analgesics. 3
Hemodynamic Concerns in Critical Illness
In critically ill patients with depleted catecholamine stores (which often accompanies respiratory failure requiring BiPAP), ketamine's expected sympathomimetic effects may be blunted or reversed, leading to paradoxical hypotension and potential cardiac arrest. 4, 3
The European Society of Cardiology recommends avoiding ketamine in patients with ischemic heart disease, cerebrovascular disease, or hypertension due to cardiovascular stimulant effects. 4
Clinical Algorithm for Safe Use
Pre-Administration Assessment
Ensure immediate intubation capability with paralytic agents, induction medications, and airway equipment at bedside before administering ketamine. 1
Assess for depleted catecholamine stores (sepsis, chronic critical illness, prolonged respiratory failure) which predict hemodynamic instability. 4
Consider co-administration of anticholinergics (glycopyrrolate or atropine) if the patient has reactive airway disease, as ketamine increases bronchial secretions that can worsen airway obstruction. 3
Dosing Strategy
Use the lowest effective dose - the case report of apnea occurred at just 0.31 mg/kg IV, well below typical procedural sedation doses of 1-2 mg/kg. 1
For procedural sedation in pediatric populations, ketamine doses of 1-2 mg/kg IV (with midazolam 0.05 mg/kg) have demonstrated safety, but these studies excluded critically ill patients. 2
Monitoring Requirements
Pulse oximetry is mandatory in patients at increased risk of hypoxemia, particularly when using sedatives in patients with significant comorbidity. 2
Consider capnometry for early identification of hypoventilation, though this may be challenging with BiPAP in place. 2
Have bag-valve-mask ventilation immediately available, as this was required within one minute in the reported case. 1
Alternative Considerations
When Ketamine May Be Advantageous
Ketamine's bronchodilator properties theoretically benefit asthma patients, though secretions must be managed with anticholinergics. 3
Ketamine maintains hemodynamic stability better than propofol or benzodiazepines in hemodynamically stable patients. 4
When to Avoid Ketamine
Active psychosis - emergence reactions occur in 10-30% of adults, though co-administration of midazolam reduces this risk. 4
Severe cardiovascular disease with depleted reserves - the sympathomimetic effects may cause cardiac decompensation rather than support. 4
Pregnancy - ketamine is contraindicated in women who are or may become pregnant. 4
Key Clinical Pitfall
The most critical error is assuming ketamine's traditional respiratory safety profile applies to critically ill patients requiring BiPAP. The case report demonstrates that even sub-sedation doses can cause complete apnea in patients with acute respiratory failure. 1 If ketamine is used, the clinician must be prepared to immediately secure the airway through rapid sequence intubation, effectively treating this as a "delayed sequence intubation" scenario where apnea is anticipated rather than unexpected. 1