What is the target Bispectral Index (BIS) range for a paralyzed and sedated patient?

Target BIS Range for Paralyzed and Sedated Patients

For paralyzed and sedated patients, target a BIS range of 40-60, recognizing that neuromuscular blocking agents artificially lower BIS values and make this monitoring unreliable as a sole indicator of adequate sedation depth. 1

Critical Understanding: NMBAs Confound BIS Readings

• Neuromuscular blocking agents directly reduce BIS scores even in awake, unsedated patients, making BIS values unreliable indicators of true sedation depth 1
• Studies demonstrate that completely paralyzed but awake patients showed significant BIS reductions, and the monitor failed to detect awareness in these subjects 1
• All paralyzed patients must receive adequate analgesia and sedation targeting deep sedation levels before and throughout neuromuscular blockade, regardless of BIS values 1

Recommended BIS Targets During Paralysis

• Maintain BIS values between 40-60 during general anesthesia and therapeutic paralysis 2, 3
• BIS values below 40 denote deep hypnosis and should be avoided as they increase risk of hemodynamic instability 2
• For cardiac arrest patients undergoing targeted temperature management with paralysis, deep sedation is required during the induction phase, with moderate sedation during maintenance 4

Why BIS Alone Is Insufficient in Paralyzed Patients

• BIS monitoring demonstrated only moderate correlation (r=0.68) with clinical sedation scales in non-paralyzed ICU patients 5
• In one study, 9.6% of paralyzed patients were inadequately sedated (restless or agitated) upon emergence despite BIS monitoring 6
• The sensitivity of BIS <60 in predicting deep sedation was 100%, but the positive predictive value was only 35.7%, meaning many deeply sedated patients had BIS values >60 6
• BIS cannot distinguish between deep sedation and general anesthesia, limiting its utility for titrating total anesthetic depth 7

Multimodal Monitoring Strategy

Do not rely on BIS alone—incorporate the following:

• Vital signs monitoring: heart rate, blood pressure, though these lack specificity 1
• Physical signs: diaphoresis and lacrimation, though also non-specific 1
• Scheduled interruptions: implement periodic cessation of NMBA infusions or use bolus dosing to permit assessment of actual sedation adequacy 1
• Train-of-four monitoring: incorporate peripheral nerve stimulation to assess degree of paralysis, but not as sole monitoring method 1

Critical Safety Principles

• Never discontinue analgesics or sedatives while NMBAs are running—this is a critical safety error 1
• NMBAs have zero analgesic or sedating properties, making inadequate sedation during paralysis a high-risk scenario for awareness and recall 1
• The Society of Critical Care Medicine suggests using objective measures like BIS as adjuncts (not primary monitors) when subjective sedation assessments are impossible due to paralysis 1

Special Considerations for Specific Populations

Cardiac arrest patients undergoing TTM:

• Deep sedation required during induction phase (0-2 hours) 4
• Moderate sedation during maintenance phase with NMB often needed 4
• Reduce to light sedation during rewarming and avoid NMB 4
• Neuroprognostication should be delayed ≥72 hours after rewarming and discontinuation of sedation 4

Procedural sedation context:

• For non-paralyzed patients undergoing procedural sedation, optimal BIS range is 70-85, balancing adequate sedation with lower respiratory depression rates 4
• BIS values >85 associated with higher rates of pain and recall 4
• BIS values <70 associated with higher rates of respiratory depression 4

Common Pitfalls to Avoid

• Avoid using BIS as the sole determinant of sedation adequacy in paralyzed patients, as studies show extensive overlap and poor discrimination between sedation levels 1
• Do not assume BIS <60 guarantees adequate sedation—clinical correlation is essential 6
• Recognize that certain anesthetics (ketamine, sevoflurane) may paradoxically increase BIS values despite adequate anesthesia depth 2, 7
• Temperature changes affect BIS values—hypothermia reduces anesthetic requirements by approximately 1.2 BIS units per 1°C reduction 2