What is the role of reversal in general anesthesia?

Role of Reversal in General Anesthesia

Pharmacological reversal of neuromuscular blockade is strongly recommended following the use of muscle relaxants during general anesthesia to prevent residual neuromuscular blockade and associated complications. 1

Importance of Neuromuscular Blockade Reversal

• Residual neuromuscular blockade is associated with higher morbidity and mortality within the first 24 hours postoperatively, increased risk of critical respiratory events, postoperative pneumonia, pharyngeal muscle dysfunction, and delayed discharge from recovery 1
• Neuromuscular blockade during general anesthesia is dose-dependently associated with a higher risk of postoperative delirium in older patients, which can be mitigated by proper reversal 2
• Quantitative monitoring of neuromuscular function is essential whenever a non-depolarizing neuromuscular blocking drug (NDNMBD) is used to ensure full recovery 3

Monitoring Requirements for Effective Reversal

• Quantitative adductor pollicis monitoring is recommended for diagnosing residual neuromuscular blockade 1
• A train-of-four ratio (T4/T1) of at least 0.9 at the adductor pollicis is required to eliminate the possibility of residual neuromuscular blockade 1
• No clinical test is sensitive enough to detect residual neuromuscular blockade; only quantitative instrumental monitoring can reliably assess recovery 1
• Intraoperative monitoring of neuromuscular blockade is strongly recommended throughout the procedure 1

Reversal with Anticholinesterases (Neostigmine)

• After administering a non-depolarizing muscle relaxant, it is recommended to await spontaneous reversal with four detectable muscle responses at the adductor pollicis following TOF stimulation before administering neostigmine 1
• Administering neostigmine before adequate spontaneous recovery (four TOF responses) results in longer time to achieve full reversal 1
• Neostigmine can cause significant cardiovascular effects including bradycardia or tachycardia, which is why it's typically co-administered with glycopyrrolate 4
• While neostigmine and glycopyrrolate can cause intraoperative bradycardia or tachycardia, they don't appear to increase 30-day postoperative cardiovascular complications in the general population 4

Reversal with Selective Agents (Sugammadex)

• Sugammadex provides rapid reversal of profound neuromuscular block from aminosteroidal agents 3
• In thoracic surgery, sugammadex appears more effective than neostigmine in reducing postoperative pulmonary complications 5
• Both neuromuscular monitoring and reversal drugs significantly reduce the risk of postoperative pulmonary complications in thoracic surgery 5

Special Considerations

• In patients with high risk of cardiovascular complications (elderly, high-risk surgery, history of atrial fibrillation), anticholinesterase reversal may have greater clinical relevance for cardiovascular outcomes 4
• The administration of reversal agents mitigates the risk of postoperative delirium in older patients receiving neuromuscular blockade 2
• For optimal enhanced recovery after surgery, appropriate reversal of residual paralysis is essential as part of an opioid-sparing, minimal-drug approach 6

Common Pitfalls and Caveats

• Failure to monitor neuromuscular function quantitatively can lead to undetected residual blockade 1, 3
• Administering neostigmine too early (before four TOF responses are visible) results in ineffective reversal 1
• Relying on clinical tests alone to assess recovery from neuromuscular blockade is inadequate 1
• Not using reversal agents when indicated increases the risk of postoperative pulmonary complications and delirium 2, 5
• The traditional threshold of TOF ratio >0.7 is insufficient; a ratio ≥0.9 is now considered necessary to protect the airway from aspiration before tracheal extubation 3