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Awakening Preparation for Awakening refers to the passive process in which the patient's consciousness gradually recovers after the administration of anesthetics and adjuvant drugs is stopped at the end of the surgical operation
.
Most patients can smoothly transition from a state of surgical anesthesia (stage III) to an awake state with complete protective reflexes (stage I), so before the patient wakes up, what preparations need to be done as an anesthesiologist, let's take a look
.
Withdrawal of Anesthetics 1 ● The optimal timing for discontinuing inhaled and/or intravenous anesthetics depends on the type of drug, dose, and duration of administration
.
To avoid premature or delayed awakening, the anesthesiologist must individually plan the stoppage time for each inhaled and/or intravenous drug near the completion of the surgical procedure
.
● Inhalational anesthetics: The clearance of inhaled anesthetics with termination of anesthesia and the patient awake relies on a concentration gradient from the brain to the blood, and from the blood to the alveoli, where the drug is excreted
.
Expiratory clearance depends on the partition coefficient of the inhalation anesthetic, minute ventilation, cardiac output, and technical factors (duration of administration, inhaled anesthetic concentration, fresh air flow in the breathing circuit),
etc.
● Intravenous drugs: When intravenous anesthetics are used, recovery time depends on the rate at which the drug is reduced from the central ventricle (brain) by redistribution or elimination
.
The metabolism of each drug depends on the patient's adequacy of hepatic and/or renal function, the potency of the drug, the multicompartmental pharmacokinetics following single and/or continuous infusion doses, and the active metabolism of the drug used product
.
Assess and reverse neuromuscular block 2 Assess the degree of muscle relaxation: If a non-depolarizing neuromuscular blocking agent is given, the degree of residual neuromuscular block should be determined using a peripheral nerve stimulator
.
Residual neuromuscular blockade causes upper airway muscle weakness and increases the risk of hypoventilation, hypoxemia, aspiration, and postoperative pulmonary complications
.
Before tracheal extubation, it must be ensured that neuromuscular function has fully recovered, that is, the train-of-four (TOF) ratio is ≥0.
9
.
We avoided the use of peripheral nerve stimulators to induce tonic stimulation before TOF stimulation would be performed, as this may enhance TOF assessment and lead to an underestimation of the degree of residual neuromuscular blockade in patients at subsequent extubation
.
● Administration of reversal drugs: The dose of the reversal drug (neostigmine or sugammadex) depends on the level of neuromuscular blockade at the time of administration
.
Neuromuscular blockade is spontaneously reversible in some patients
.
Observation of EEG Evidence of Recovery of Consciousness 3 ● Evaluation of raw EEG waves usually reveals that as the patient regains consciousness, slow -delta and alpha oscillations gradually disappear and high frequency beta and gamma oscillations reappear
.
However, there are individual differences in raw EEG waveforms before full recovery, depending on the anesthetic
.
The processed EEG can also be used to analyze the raw EEG signal and monitor the depth of anesthesia
.
Assessing Physiological Signals of Restoration of Consciousness 4 ● During awakening, the patient's state of consciousness can be tracked by observing changes in physiological signals
.
After muscle relaxation and reversal of circulating carbon dioxide accumulation in the brain, patients usually return to spontaneous breathing quickly
.
The breathing pattern is usually irregular and the initial tidal volume is low, but spontaneous breathing usually resumes within a few minutes
.
● Swallowing and gag reflexes, salivation, lacrimation, and facial muscle activity usually occur concurrently with or somewhat later in the restoration of spontaneous breathing, indicating recovery of specific brainstem centers
.
Restoration of muscle tone after reversal of NMBA indicated restoration of motor circuit function
.
Restoration of corneal reflexes indicates restoration of sensory function
.
Autonomic control of eye movements suggests functional recovery of the midbrain, pons, and certain cerebellar cortical and basal ganglia circuits
.
Finally, autonomously making intentional movements and responding to verbal commands indicates conscious awareness
.
● It should be noted that spontaneous eye opening is usually one of the last signs during recovery from general anesthesia and may be much later than a clear response to verbal commands
.
Antiemetic drugs 5 ● If the patient has more than one risk factor for postoperative nausea and vomiting, antiemetic drugs such as ondansetron and dexamethasone are generally required
.
Assessing the adequacy of analgesia 6 ● During recovery of consciousness, increases in heart rate, blood pressure, and respiratory rate indicate that analgesia may be inadequate
.
Analgesia can be enhanced with regional analgesic techniques or intravenous analgesics as appropriate
.
As at the immediate end of surgery, the timing, dose, and type of intensive recovery analgesia or technique should be based on: the patient's condition, the likelihood of immediate pain after the procedure, and the patient's history of opioid dependence or abuse.
Individualized determination
.
● The main method of pain relief during recovery is to use an appropriate amount of long-acting opioids, such as morphine or hydromorphone
.
When possible, use techniques to reduce the amount of intravenous opioids and other analgesics at the time of awakening, such as topical surgical site infiltration, epidural analgesia, or transversus abdominis plane block after abdominal surgery
.
Notes/Reviewed by Wu Xiaobin/Wandering Cloud Typesetting/Wu Xiaobin Swipe Up to Read References (Part) [1]Khan KS, Hayes I, Buggy DJ.
Pharmacology of anaesthetic agents II: inhalation anaesthetic agents.
Continuing Education in Anaesthesia Critical Care & Pain 2014; 14:106.
[2]Eger EI 2nd, Shafer SL.
Tutorial: context-sensitive decrement times for inhaled anesthetics.
Anesth Analg 2005; 101:688.
[3]Arain SR, Yu S, Dugan S, et al.
Titration of sevoflurane anesthesia to optimize the time to regain airway reflexes in patients undergoing elective surgery: A randomized clinical trial comparing desflurane and sevoflurane anesthesia.
Acta Anaesthesiol Scand 2020; 64:729.
[4]Peyton PJ, Chao I, Weinberg L, et al.
Nitrous oxide diffusion and the second gas effect on emergence from anesthesia.
Anesthesiology 2011; 114:596.
[5] Korman B, Dash RK, Peyton PJ.
Can Mathematical Modeling Explain the Measured Magnitude of the Second Gas Effect? Anesthesiology 2018;128:1075.
[6]van den Berg JP, Vereecke HE, Proost JH, et al.
Pharmacokinetic and pharmacodynamic interactions in anaesthesia.
A review of current knowledge and how it can be used to optimize anaesthetic drug administration.
Br J Anaesth 2017;118:44.
[7]Hendrickx JF, Eger EI 2nd, Sonner JM, Shafer SL.
Is synergy the rule? A review of anesthetic interactions producing hypnosis and immobility .
Anesth Analg 2008; 107:494.
[8]Torri G.
Inhalation anesthetics: a review.
Minerva Anestesiol 2010;76:215.
[9]Piao G, Wu J.
Systematic assessment of dexmedetomidine as anesthetic: a meta- analysis of randomized controlled trials.
Arch Med Sci 2014; 10:19.
[10] Gallego-Ligorit L, Vives M, Vallés-Torres J, et al.
Use of Dexmedetomidine in Cardiothoracic and Vascular Anesthesia.
J Cardiothorac Vasc Anesth 2018;32:1426.
.
Most patients can smoothly transition from a state of surgical anesthesia (stage III) to an awake state with complete protective reflexes (stage I), so before the patient wakes up, what preparations need to be done as an anesthesiologist, let's take a look
.
Withdrawal of Anesthetics 1 ● The optimal timing for discontinuing inhaled and/or intravenous anesthetics depends on the type of drug, dose, and duration of administration
.
To avoid premature or delayed awakening, the anesthesiologist must individually plan the stoppage time for each inhaled and/or intravenous drug near the completion of the surgical procedure
.
● Inhalational anesthetics: The clearance of inhaled anesthetics with termination of anesthesia and the patient awake relies on a concentration gradient from the brain to the blood, and from the blood to the alveoli, where the drug is excreted
.
Expiratory clearance depends on the partition coefficient of the inhalation anesthetic, minute ventilation, cardiac output, and technical factors (duration of administration, inhaled anesthetic concentration, fresh air flow in the breathing circuit),
etc.
● Intravenous drugs: When intravenous anesthetics are used, recovery time depends on the rate at which the drug is reduced from the central ventricle (brain) by redistribution or elimination
.
The metabolism of each drug depends on the patient's adequacy of hepatic and/or renal function, the potency of the drug, the multicompartmental pharmacokinetics following single and/or continuous infusion doses, and the active metabolism of the drug used product
.
Assess and reverse neuromuscular block 2 Assess the degree of muscle relaxation: If a non-depolarizing neuromuscular blocking agent is given, the degree of residual neuromuscular block should be determined using a peripheral nerve stimulator
.
Residual neuromuscular blockade causes upper airway muscle weakness and increases the risk of hypoventilation, hypoxemia, aspiration, and postoperative pulmonary complications
.
Before tracheal extubation, it must be ensured that neuromuscular function has fully recovered, that is, the train-of-four (TOF) ratio is ≥0.
9
.
We avoided the use of peripheral nerve stimulators to induce tonic stimulation before TOF stimulation would be performed, as this may enhance TOF assessment and lead to an underestimation of the degree of residual neuromuscular blockade in patients at subsequent extubation
.
● Administration of reversal drugs: The dose of the reversal drug (neostigmine or sugammadex) depends on the level of neuromuscular blockade at the time of administration
.
Neuromuscular blockade is spontaneously reversible in some patients
.
Observation of EEG Evidence of Recovery of Consciousness 3 ● Evaluation of raw EEG waves usually reveals that as the patient regains consciousness, slow -delta and alpha oscillations gradually disappear and high frequency beta and gamma oscillations reappear
.
However, there are individual differences in raw EEG waveforms before full recovery, depending on the anesthetic
.
The processed EEG can also be used to analyze the raw EEG signal and monitor the depth of anesthesia
.
Assessing Physiological Signals of Restoration of Consciousness 4 ● During awakening, the patient's state of consciousness can be tracked by observing changes in physiological signals
.
After muscle relaxation and reversal of circulating carbon dioxide accumulation in the brain, patients usually return to spontaneous breathing quickly
.
The breathing pattern is usually irregular and the initial tidal volume is low, but spontaneous breathing usually resumes within a few minutes
.
● Swallowing and gag reflexes, salivation, lacrimation, and facial muscle activity usually occur concurrently with or somewhat later in the restoration of spontaneous breathing, indicating recovery of specific brainstem centers
.
Restoration of muscle tone after reversal of NMBA indicated restoration of motor circuit function
.
Restoration of corneal reflexes indicates restoration of sensory function
.
Autonomic control of eye movements suggests functional recovery of the midbrain, pons, and certain cerebellar cortical and basal ganglia circuits
.
Finally, autonomously making intentional movements and responding to verbal commands indicates conscious awareness
.
● It should be noted that spontaneous eye opening is usually one of the last signs during recovery from general anesthesia and may be much later than a clear response to verbal commands
.
Antiemetic drugs 5 ● If the patient has more than one risk factor for postoperative nausea and vomiting, antiemetic drugs such as ondansetron and dexamethasone are generally required
.
Assessing the adequacy of analgesia 6 ● During recovery of consciousness, increases in heart rate, blood pressure, and respiratory rate indicate that analgesia may be inadequate
.
Analgesia can be enhanced with regional analgesic techniques or intravenous analgesics as appropriate
.
As at the immediate end of surgery, the timing, dose, and type of intensive recovery analgesia or technique should be based on: the patient's condition, the likelihood of immediate pain after the procedure, and the patient's history of opioid dependence or abuse.
Individualized determination
.
● The main method of pain relief during recovery is to use an appropriate amount of long-acting opioids, such as morphine or hydromorphone
.
When possible, use techniques to reduce the amount of intravenous opioids and other analgesics at the time of awakening, such as topical surgical site infiltration, epidural analgesia, or transversus abdominis plane block after abdominal surgery
.
Notes/Reviewed by Wu Xiaobin/Wandering Cloud Typesetting/Wu Xiaobin Swipe Up to Read References (Part) [1]Khan KS, Hayes I, Buggy DJ.
Pharmacology of anaesthetic agents II: inhalation anaesthetic agents.
Continuing Education in Anaesthesia Critical Care & Pain 2014; 14:106.
[2]Eger EI 2nd, Shafer SL.
Tutorial: context-sensitive decrement times for inhaled anesthetics.
Anesth Analg 2005; 101:688.
[3]Arain SR, Yu S, Dugan S, et al.
Titration of sevoflurane anesthesia to optimize the time to regain airway reflexes in patients undergoing elective surgery: A randomized clinical trial comparing desflurane and sevoflurane anesthesia.
Acta Anaesthesiol Scand 2020; 64:729.
[4]Peyton PJ, Chao I, Weinberg L, et al.
Nitrous oxide diffusion and the second gas effect on emergence from anesthesia.
Anesthesiology 2011; 114:596.
[5] Korman B, Dash RK, Peyton PJ.
Can Mathematical Modeling Explain the Measured Magnitude of the Second Gas Effect? Anesthesiology 2018;128:1075.
[6]van den Berg JP, Vereecke HE, Proost JH, et al.
Pharmacokinetic and pharmacodynamic interactions in anaesthesia.
A review of current knowledge and how it can be used to optimize anaesthetic drug administration.
Br J Anaesth 2017;118:44.
[7]Hendrickx JF, Eger EI 2nd, Sonner JM, Shafer SL.
Is synergy the rule? A review of anesthetic interactions producing hypnosis and immobility .
Anesth Analg 2008; 107:494.
[8]Torri G.
Inhalation anesthetics: a review.
Minerva Anestesiol 2010;76:215.
[9]Piao G, Wu J.
Systematic assessment of dexmedetomidine as anesthetic: a meta- analysis of randomized controlled trials.
Arch Med Sci 2014; 10:19.
[10] Gallego-Ligorit L, Vives M, Vallés-Torres J, et al.
Use of Dexmedetomidine in Cardiothoracic and Vascular Anesthesia.
J Cardiothorac Vasc Anesth 2018;32:1426.
