What is a Phase 2 Block?

What is a Phase 2 Block?

Phase II blockade is thought to be secondary to repeated channel opening, causing distortion of the normal electrolyte balance and desensitizing the junctional membrane to further depolarization. It has some of the characteristics of a nondepolarizing blockade: Fade after tetanic or TOF stimulation.

What is NMJ blockade?

Neuromuscular-blocking drugs block neuromuscular 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.

How is the action of succinylcholine terminated?

Neuromuscular blockade terminates by the diffusion of succinylcholine from the end plate into the extracellular fluid because there is no pseudocholinesterase at the motor end plate. Pseudocholinesterase influences the onset and duration of action by controlling the rate of hydrolysis in plasma.

What are the two types of neuromuscular blockers?

Neuromuscular blocking agents (NMBAs) come in two forms: depolarizing neuromuscular blocking agents (e.g., succinylcholine) and nondepolarizing neuromuscular blocking agents (e.g., rocuronium, vecuronium, atracurium, cisatracurium, mivacurium).

What is the antidote for succinylcholine?

Dantrolene is an effective antidote.

Is succinylcholine a paralytic?

Succinylcholine has been traditionally used as a first-line paralytic due to its quick onset of action and short half-life.

Do you need to reverse succinylcholine?

It should always be reversed to prevent diplopia, laryngeal weakness, atelectasis, CO2 retention and respiratory acidosis. The diplopia contributes to post-operative nausea and vomiting (PONV), and the CO2 retention and respiratory acidosis lead to delayed emergences at the end of surgery.

Does succinylcholine affect breathing?

Adverse reactions to succinylcholine consist primarily of an extension of its pharmacological actions. Succinylcholine causes profound muscle relaxation resulting in respiratory depression to the point of apnea; this effect may be prolonged.

Why is decamethonium not used clinically?

In clinical use, the reliability of action of decamethonium makes an antidote unnecessary, but should a prolonged action occur, then it is likely that this may be due to a dual block, and it would be logical to observe the effect of a small dose of an anticurare drug.

Is succinylcholine reversible?

Sugammadex can reverse profound blockade and can be given for immediate reversal and its use would avoid the potentially serious adverse effects of the currently used agent, succinylcholine. Also, sugammadex can reverse NMB more quickly and predictably than existing agents.

Can you reverse succinylcholine?

How long does succinylcholine stay in your system?

In blood, SUX was usually detectable for up to 10 min post-injection, while detection of SMC was possible over the whole observation period of 6 h.

How much succinylcholine is needed for Phase II blockade?

Definition. The receptor does not respond appropriately to acetylcholine, and neuromuscular blockade is prolonged. Phase II block may be seen clinically with doses of succinylcholine >4mg/kg, but some characteristics of this blockade have been reported at 0.3mg/kg.

How are high doses of succinylcholine related to posttetanic potentiation?

The finding that high doses of succinylcholine inhibited presynaptic α3β2 AChRs ( i.e. , the compound behaved like a nondepolarizing relaxant) may help to explain how high or repeated doses of succinylcholine result in a nondepolarizing type of block (phase II block) characterized by fade and posttetanic potentiation.

Which is associated with the onset of succinylcholine action?

Skeletal muscle fasciculations are associated with initial (onset) succinylcholine (Anectine) action. Phases — Phase II

Can a neuromuscular blocking agent reduce succinylcholine side effects?

Note: Many succinylcholine (Anectine) side effects may be reduced by prior administration of non-paralyzing doses of nondepolarizing neuromuscular-blocking agents