Neuro muscular blocking agents and reversal

Neuromuscular Blockade

• Despite 7 decades of research, significant differences in opinion exist regarding the management of neuromuscular blockade at the conclusion of surgery.
• Emphasis in anesthesia should be on "properly anesthetizing rather than paralyzing" a patient.

Reversal of Neuromuscular Blockade

• Appropriate reversal of nondepolarizing neuromuscular blockade is essential to avoid adverse patient outcomes.
• Complete recovery of muscle strength should be present, and residual effects of neuromuscular blocking drugs (NMBDs) should be fully pharmacologically reversed or spontaneously recovered.

Assessment of Residual Neuromuscular Blockade

• Tracheal extubation should not occur until complete recovery of muscle strength is present and residual effects are fully reversed.
• Sufficient recovery from neuromuscular blockade for tracheal extubation can be confirmed by an adductor pollicis train-of-four (TOF) ratio of at least 0.90 (or 1.0 if acceleromyography [AMG] is used).
• Quantitative neuromuscular monitoring is the only method of assessing whether a safe level of recovery of muscular function has occurred.

Residual Neuromuscular Blockade

• Residual neuromuscular blockade is not a rare event in the postanesthesia care unit (PACU).
• Approximately 30% to 50% of patients can have TOF ratios less than 0.90 following surgery.
• Patients with TOF ratios less than 0.90 in the PACU are at increased risk for hypoxemic events, impaired control of breathing during hypoxia, airway obstruction, postoperative pulmonary complications, symptoms of muscle weakness, and prolonged PACU admission times.

Incomplete Neuromuscular Recovery and Its Consequences

• Incomplete neuromuscular recovery can lead to adverse patient outcomes, emphasizing the importance of detecting and treating residual muscle weakness.
• Methods to detect residual neuromuscular blockade include clinical evaluations, qualitative neuromuscular monitors (peripheral nerve stimulators), and quantitative neuromuscular monitors.

Clinical Evaluation for Signs of Muscle Weakness

• In the past, clinicians evaluated residual paralysis and the need for neostigmine based on observations of "shallow, jerky movements of the diaphragm" at the end of surgery.
• In the absence of clinically observable respiratory impairment, neuromuscular function was assumed to be adequate, and no reversal drugs were administered.

Use of Anticholinesterase Drugs

• A survey in the late 1950s found that 44% of respondents used neostigmine "always" or "almost always" when d-tubocurarine or gallamine was used.
• Two-thirds of respondents administered 1.25 to 2.5 mg of neostigmine when antagonizing these NMBDs.

Neuromuscular Monitoring

• Peripheral nerve stimulators are used to assess neuromuscular function.
• Quantitative neuromuscular monitoring is the only method of assessing whether a safe level of recovery of muscular function has occurred.

Key Points

• Appropriate reversal of a nondepolarizing neuromuscular blockade is essential to avoid adverse patient outcomes.
• Sufficient recovery from neuromuscular blockade for tracheal extubation can be confirmed by an adductor pollicis train-of-four (TOF) ratio of at least 0.90 (or 1.0 if acceleromyography is used).
• Residual neuromuscular blockade is not a rare event in the postanesthesia care unit (PACU), affecting approximately 30% to 50% of patients.
• Patients with TOF ratios less than 0.90 in the PACU are at increased risk for hypoxemic events, impaired control of breathing during hypoxia, airway obstruction, postoperative pulmonary complications, symptoms of muscle weakness, and prolonged PACU admission times.