Ketamine Falsely Lowers BIS in Children
Ketamine paradoxically increases or fails to appropriately decrease BIS values despite producing adequate sedation or general anesthesia in pediatric patients, making BIS monitoring unreliable for assessing depth of sedation when this medication is used. 1
The Ketamine-BIS Paradox
- Ketamine causes central excitation that interferes with BIS algorithms, resulting in BIS numbers that paradoxically go up rather than down despite a state of deep sedation or general anesthesia 1
- The BIS readings do not correspond with clinical sedation depth when ketamine is administered, unlike propofol where BIS correlates well with sedation levels 1
- In a pediatric emergency department study, the association between clinical sedation scores (OAA/S) and BIS values was not statistically significant for ketamine-sedated patients (beta = 0.809, P = 0.09), while remaining highly significant for non-ketamine medications (beta = 8.6, P < 0.0001) 2
Other Medications That Affect BIS Reliability
Sevoflurane also causes paradoxical BIS increases due to central excitation despite adequate anesthesia depth 1, 3
Neuromuscular blocking agents artificially lower BIS values even in awake, unsedated patients, making BIS unreliable as a sole indicator of sedation depth 4, 5:
- In awake volunteers receiving rocuronium or suxamethonium, BIS decreased to values as low as 44-47, suggesting deep sedation when patients were fully conscious 5
- BIS requires muscle activity in addition to awake EEG patterns to generate appropriate values indicating wakefulness 5
Clinical Implications for Pediatric Sedation
- Do not rely on BIS monitoring to guide ketamine sedation depth in children - use clinical sedation scales instead 1, 2
- BIS algorithms were developed and validated in adults, not children of varying ages and brain development stages 1
- For non-ketamine sedation regimens (propofol, midazolam, opioids), BIS shows good correlation with clinical sedation scales in pediatric patients 2, 6, 7
Common Pitfall to Avoid
The most critical error is assuming a high BIS value during ketamine administration indicates inadequate sedation and inappropriately increasing the dose, potentially leading to oversedation and adverse effects 1, 2. Always assess ketamine sedation depth using validated clinical sedation scales rather than BIS values 2, 7.