Postoperative residual curarization

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Postoperative residual curarization
Electromyographic recording at adductor pollicis muscle and stimulation of the ulnar nerve.jpg
Electromyographic monitoring at the adductor policies muscle.
Specialty Anesthesia

Postoperative residual curarization (PORC) or residual neuromuscular blockade (RNMB) is a residual paresis after emergence from general anesthesia that may occur with the use of neuromuscular-blocking drugs. [1] [2] Today residual neuromuscular blockade is defined as a train of four ratio [3] of less than 0.9 when measuring the response to ulnar nerve stimulation at the adductor pollicis muscle using mechanomyography or electromyography. [4] A meta-analysis reported that the incidence of residual neuromuscular paralysis was 41% in patients receiving intermediate neuromuscular blocking agents during anaesthesia. [1] It is possible that > 100,000 patients annually in the USA alone, are at risk of adverse events associated with undetected residual neuromuscular blockade. [5] Neuromuscular function monitoring and the use of the appropriate dosage of sugammadex to reverse blockade produced by rocuronium can reduce the incidence of postoperative residual curarization. [6] In this study, with usual care group receiving reversal with neostigmine resulted in a residual blockade rate of 43%.[ citation needed ]

Contents

Incidence

Multiple studies have demonstrated that incomplete reversal of NMBDs is an important risk factor for postoperative morbidity and mortality. Multiple studies have shown that postoperative residual curarization in the post-anesthesia care unit (PACU) is a common complication, with 40% of patients exhibiting signs of residual paralysis. The incidence of this complication continues to be high and does not seem to be decreasing over time. [7]

Types of neuromuscular blocking agents

Classified into two main groups:

•Depolarizing NMBDs: produces skeletal muscle relaxation by binding directly with nAChRs to cause prolonged depolarization.

•Non-depolarizing NMBDs: competitive antagonists (competing with acetylcholine [ACh] for the binding sites at the nAChRs), preventing the initiation of action potential. [8]

Non-depolarizing neuromuscular blocking agents

Non-depolarizing NMBAs are classified based on their duration of action (short, intermediate, or long-acting agents. The two most commonly used non-depolarizing NMBDs in the operating room are rocuronium and vecuronium. Both are intermediate-acting, steroidal NMBAs. Vecuronium and rocuronium can be reversed by anticholinesterases (neostigmine) or sugammadex. If sufficient spontaneous recovery has not been achieved, neostigmine (or sugammadex) should be administered. [9]

Depolarizing neuromuscular blocking agents

Succinylcholine is the only depolarizing NMBA available for clinical use. It produces a neuromuscular blockade that is the fastest in onset and has the shortest duration of all NMBDs. Due to these properties, succinylcholine is often used for rapid sequence induction and intubation. When a continuous infusion, repeated doses, or a large dose of succinylcholine (>4 mg/kg) is used, the risk of a Phase II block and prolonged paralysis is increased. This type of block occurs when the desensitizing phase sets in and the muscle is no longer responsive to acetylcholine and full neuromuscular blockade is achieved. TOF fade is indicative of phase II block that is likely to occur in patients who received succinylcholine and may resemble features of a nondepolarizing block. During phase II, reversal with neostigmine should not be attempted. Anticholinesterase agents can worsen paralysis in this setting. [10] Prolonged paralysis after succinylcholine administration may be due to butyrylcholinesterase (pseudocholinesterase) deficiency and may require prolonged mechanical ventilation. Unlike non-depolarizing NMBDs, reversal with neostigmine should not be attempted and sugammadex will have no effect on recovery. [11]

Adverse events from inadequate neuromuscular blockade reversal

Inadequate reversal of NMBAs is an important risk factor for anesthesia related complications. Even small degrees of residual paralysis are associated with weakness of upper airway muscles which may lead to airway obstruction and increased risk of aspiration. The hypoxic ventilatory response (HRV) can also be severely depressed as well leading to hypoxemia and need for reintubation. [7] Studies have shown that incomplete neuromuscular recovery is associated with an increased risk of pulmonary complications. A prospective observational study including patients who underwent general anesthesia for noncardiac surgery reported that the "use of NMBAs was independently associated with an increase in postoperative pulmonary complications within 28 days of surgery." [12]

Monitoring neuromuscular blockade

Peripheral nerve stimulation patterns and definitions

Train-of-four (TOF)

TOF stimulation consists of four successive supramaximal stimuli delivered at 2 Hz. After administration of a nondepolarizing NMBD, responses at this frequency progressively decrease in amplitude (referred to as "fade" or a decrease in the TOF ratio from a normal ratio of 1).

Train-of-four ratio (TOFR)

A TOF ratio (TOFR) is calculated by dividing the amplitude of the fourth response by the amplitude of the first response (requires an quantitative measure of the response to stimulation). [13]

Train-of-four count (TOFC)

The TOF count (TOFC) is defined as the "number of detectable evoked responses, and it correlates with the degree of neuromuscular block, as follows:

  • TOFC = 1 : >95 percent of nicotinic acetylcholine receptors (nAChRs) blocked
  • TOFC = 2 : 85 to 90 percent of nAChRs blocked
  • TOFC = 3 : 80 to 85 percent of nAChRs blocked
  • TOFC = 4 : 70 to 75 percent of nAChRs blocked [13]

Train-of-four ratio <0.9

Data suggests that a TOF ratio measured qualitatively with EMG, MMG, or AMG must reach the threshold value of >0.9 to assure recovery of neuromuscular function. TOF ratios <0.9 are associated with residual blockade and paralysis and have demonstrated an increased risk of aspiration. [14]

Subjective monitoring

Subjective monitoring refers to the clinical evaluation of assessing the TOFC or degree of fade by using methods such as physically touching the patient and feeling movement or visibly observing a twitch in response to neurostimulation provided by a peripheral nerve stimulator. If subjective monitoring is used, its limitations should be recognized: "clinicians tend to overestimate the TOFC when using subjective evaluation, especially at moderate levels of block. Likewise, the level of fade is difficult to detect subjectively, with most clinicians unable to detect fade when TOF ratios >0.4." [15]

Objective/quantitative monitoring

Due to the difficulty detecting fade subjectively (TOF ratios between 0.4 and 0.9) when using peripheral nerve stimulators, clinicians are unable to reliably exclude residual neuromuscular blockade. TOF ratios >0.4 can be measured accurately and displayed numerically using quantitative neuromuscular monitoring. However, TOF ratios >4 can be measured accurately by using quantitative monitoring methods such as electromyography (EMG), kinemyography (KMG), phonomyography (PMG), and acceleromyography (AMG). [14]

Reversal of NMBDs and methods to avoid residual neuromuscular blockade

•Using short-acting or intermediate-acting NBMDs whenever possible can decrease the risk of residual neuromuscular blockade when compared with long-acting NMBDs.

•Use objective neuromuscular monitoring (acceleromyography, electromyography, kinemyography) if possible. Peripheral nerve stimulators may be more readily available and can be used as well. However, peripheral nerve stimulators can only subjectively determine the depth of block (train-of-four count) and cannot provide accurate information needed for the timing and dosing of reversal agents as well as ensure full recovery (TOF fade). [16]

•If spontaneous recovery has not reached a TOFC = 4, use sugammadex rather than neostigmine for reversal of steroidal NMBDs. [17]

•If sugammadex is unavailable, wait for spontaneous recovery to achieve a TOFC = 4 before administering neostigmine.

•Extubate the trachea only after a TOFR ≥0.9 is achieved (if quantitative monitors are available)

•If objective monitoring is not available, administer reversal agents (neostigmine) only when TOFC = 4. Wait at least 10 minutes after neostigmine is given to ensure enough time for the neuromuscular blockade to be fully reversed before tracheal extubation. [18]

Related Research Articles

<span class="mw-page-title-main">Suxamethonium chloride</span> Chemical compound

Suxamethonium chloride, also known as suxamethonium or succinylcholine, or simply sux by medical abbreviation, is a medication used to cause short-term paralysis as part of general anesthesia. This is done to help with tracheal intubation or electroconvulsive therapy. It is administered by injection, either into a vein or into a muscle. When used in a vein, onset of action is generally within one minute and effects last for up to 10 minutes.

<span class="mw-page-title-main">General anaesthesia</span> Medically induced loss of consciousness

General anaesthesia (UK) or general anesthesia (US) is a method of medically inducing loss of consciousness that renders a patient unarousable even with painful stimuli. This effect is achieved by administering either intravenous or inhalational general anaesthetic medications, which often act in combination with an analgesic and neuromuscular blocking agent. Spontaneous ventilation is often inadequate during the procedure and intervention is often necessary to protect the airway. General anaesthesia is generally performed in an operating theater to allow surgical procedures that would otherwise be intolerably painful for a patient, or in an intensive care unit or emergency department to facilitate endotracheal intubation and mechanical ventilation in critically ill patients.

<span class="mw-page-title-main">Edrophonium</span>

Edrophonium is a readily reversible acetylcholinesterase inhibitor. It prevents breakdown of the neurotransmitter acetylcholine and acts by competitively inhibiting the enzyme acetylcholinesterase, mainly at the neuromuscular junction. It is sold under the trade names Tensilon and Enlon.

<span class="mw-page-title-main">Anesthetic</span> Drug that causes anesthesia

An anesthetic or anaesthetic is a drug used to induce anesthesia ⁠— ⁠in other words, to result in a temporary loss of sensation or awareness. They may be divided into two broad classes: general anesthetics, which result in a reversible loss of consciousness, and local anesthetics, which cause a reversible loss of sensation for a limited region of the body without necessarily affecting consciousness.

Awareness under anesthesia, also referred to as intraoperative awareness or accidental awareness during general anesthesia (AAGA), is a rare complication of general anesthesia where patients regain varying levels of consciousness during their surgical procedures. While anesthesia awareness is possible without resulting in any long-term memory of the experience, it is also possible for victims to have awareness with explicit recall, where they can remember the events related to their surgery.

<span class="mw-page-title-main">Neostigmine</span> Anti-full body paralysis drug treatment

Neostigmine, sold under the brand name Bloxiverz, among others, is a medication used to treat myasthenia gravis, Ogilvie syndrome, and urinary retention without the presence of a blockage. It is also used in anaesthesia to end the effects of non-depolarising neuromuscular blocking medication. It is given by injection either into a vein, muscle, or under the skin. After injection effects are generally greatest within 30 minutes and last up to 4 hours.

<span class="mw-page-title-main">Vecuronium bromide</span> Muscle relaxant

Vecuronium bromide, sold under the brand name Norcuron among others, is a medication used as part of general anesthesia to provide skeletal muscle relaxation during surgery or mechanical ventilation. It is also used to help with endotracheal intubation; however, agents such as suxamethonium (succinylcholine) or rocuronium are generally preferred if this needs to be done quickly. It is given by injection into a vein. Effects are greatest at about 4 minutes and last for up to an hour.

In anaesthesia and advanced airway management, rapid sequence induction (RSI) – also referred to as rapid sequence intubation or as rapid sequence induction and intubation (RSII) or as crash induction – is a special process for endotracheal intubation that is used where the patient is at a high risk of pulmonary aspiration. It differs from other techniques for inducing general anesthesia in that several extra precautions are taken to minimize the time between giving the induction drugs and securing the tube, during which period the patient's airway is essentially unprotected.

<span class="mw-page-title-main">Tubocurarine chloride</span> Obsolete muscle relaxant

Tubocurarine is a toxic alkaloid historically known for its use as an arrow poison. In the mid-1900s, it was used in conjunction with an anesthetic to provide skeletal muscle relaxation during surgery or mechanical ventilation. Safer alternatives, such as cisatracurium and rocuronium, have largely replaced it as an adjunct for clinical anesthesia and it is now rarely used.

<span class="mw-page-title-main">Neuromuscular-blocking drug</span> Type of paralyzing anesthetic including lepto- and pachycurares

Neuromuscular-blocking drugs, or Neuromuscular blocking agents (NMBAs), block transmission at the neuromuscular junction, causing paralysis of the affected skeletal muscles. This is accomplished via their action on the post-synaptic acetylcholine (Nm) receptors.

<span class="mw-page-title-main">Rocuronium bromide</span> Chemical compound

Rocuronium bromide is an aminosteroid non-depolarizing neuromuscular blocker or muscle relaxant used in modern anaesthesia to facilitate tracheal intubation by providing skeletal muscle relaxation, most commonly required for surgery or mechanical ventilation. It is used for standard endotracheal intubation, as well as for rapid sequence induction (RSI).

<span class="mw-page-title-main">Mivacurium chloride</span> Drug used in a hospital setting

Mivacurium chloride is a short-duration non-depolarizing neuromuscular-blocking drug or skeletal muscle relaxant in the category of non-depolarizing neuromuscular-blocking drugs, used adjunctively in anesthesia to facilitate endotracheal intubation and to provide skeletal muscle relaxation during surgery or mechanical ventilation.

<span class="mw-page-title-main">Sugammadex</span> Selective relaxant binding agent

Sugammadex, sold under the brand name Bridion, is a medication for the reversal of neuromuscular blockade induced by rocuronium and vecuronium in general anaesthesia. It is the first selective relaxant binding agent (SRBA). It is marketed by Merck.

Guedel's classification is a means of assessing of depth of general anesthesia introduced by Arthur Ernest Guedel (1883-1956) in 1920.

<span class="mw-page-title-main">Gantacurium chloride</span> Chemical compound

Gantacurium chloride is a new experimental neuromuscular blocking drug or skeletal muscle relaxant in the category of non-depolarizing neuromuscular-blocking drugs, used adjunctively in surgical anesthesia to facilitate endotracheal intubation and to provide skeletal muscle relaxation during surgery or mechanical ventilation. Gantacurium is not yet available for widespread clinical use: it is currently undergoing Phase III clinical development.

<span class="mw-page-title-main">Brachial plexus block</span>

Brachial plexus block is a regional anesthesia technique that is sometimes employed as an alternative or as an adjunct to general anesthesia for surgery of the upper extremity. This technique involves the injection of local anesthetic agents in close proximity to the brachial plexus, temporarily blocking the sensation and ability to move the upper extremity. The subject can remain awake during the ensuing surgical procedure, or they can be sedated or even fully anesthetized if necessary.

<span class="mw-page-title-main">Acceleromyograph</span> Used to measure the force produced by a muscle

An acceleromyograph is a piezoelectric myograph, used to measure the force produced by a muscle after it has undergone nerve stimulation. Acceleromyographs may be used, during anaesthesia when muscle relaxants are administered, to measure the depth of neuromuscular blockade and to assess adequacy of recovery from these agents at the end of surgery. Acceleromyography is classified as quantitative neuromuscular monitoring.

<span class="mw-page-title-main">Neuromuscular monitoring</span>

In anesthesia, neuromuscular blocking agents may be required to facilitate endotracheal intubation and provide optimal surgical conditions. When neuromuscular blocking agents are administered, neuromuscular function of the patient must be monitored. Neuromuscular function monitoring is a technique that involves the electrical stimulation of a motor nerve and monitoring the response of the muscle supplied by that nerve. It may be used from the induction of to recovery from neuromuscular blockade. Importantly, it is used to confirm adequacy of recovery after the administration of neuromuscular blocking agents. The response of the muscles to electrical stimulation of the nerves can be recorded subjectively (qualitative) or objectively (quantitatively). Quantitative techniques include electromyography, acceleromyography, kinemyography, phonomygraphy and mechanomyography. Neuromuscular monitoring is recommended when neuromuscular-blocking drugs have been part of the general anesthesia and the doctor wishes to avoid postoperative residual curarization (PORC) in the patient, that is, the residual paralysis of muscles stemming from these drugs.

Tetanic fade refers to the diminishing muscle twitch response from an evoked potential stimulation of muscle under the effect of either a non-depolarizing neuromuscular blocking agent, or a muscle that is under a phase 2 depolarizing neuromuscular blocking agent.

<span class="mw-page-title-main">Neuromuscular drug</span>

Neuromuscular drugs are chemical agents that are used to alter the transmission of nerve impulses to muscles, causing effects such as temporary paralysis of targeted skeletal muscles. Most neuromuscular drugs are available as quaternary ammonium compounds which are derived from acetylcholine (ACh). This allows neuromuscular drugs to act on multiple sites at neuromuscular junctions, mainly as antagonists or agonists of post-junctional nicotinic receptors. Neuromuscular drugs are classified into four main groups, depolarizing neuromuscular blockers, non-depolarizing neuromuscular blockers, acetylcholinesterase inhibitors, and butyrylcholinesterase inhibitors.

References

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