24 Mar 25 NMBD & Intro and Succinylcholine Flashcards
What is neuromuscular blockade?
A pharmacological technique used to induce muscle paralysis for surgical procedures.
What is succinylcholine?
A depolarizing drug used for rapid tracheal intubation with an onset of 30-60 seconds and a duration of 3-5 minutes.
List some side effects of succinylcholine.
- Hyperkalemia
- Myalgias
- Increased intraocular pressure
- Increased intracranial pressure
What can mitigate the side effects of succinylcholine?
Pre-treatment with a non-depolarizing drug.
What are the contraindications for using succinylcholine?
- Renal failure
- Pregnancy
- Certain genetic conditions
What is the mechanism of action of succinylcholine?
It mimics the action of acetylcholine at the neuromuscular junction.
What are the two categories of neuromuscular blockade drugs?
- Depolarizing drugs
- Non-depolarizing drugs
What is the primary non-depolarizing drug mentioned?
Pancuronium and vecuronium.
Fill in the blank: Succinylcholine causes _______ and is used for rapid intubation.
muscle paralysis
True or False: Succinylcholine is the only drug in the depolarizing category.
True.
What is myasthenia gravis?
An autoimmune disease that affects neuromuscular transmission, increasing sensitivity to neuromuscular blockade drugs.
What is the role of reversal agents like neostigmine?
To reverse the effects of non-depolarizing neuromuscular blockade drugs.
What is the purpose of using nerve stimulators during anesthesia?
To monitor muscle paralysis and residual paralysis.
What is malignant hyperthermia?
A life-threatening condition triggered by certain anesthetics, treated with dantrolene.
List reasons for using neuromuscular blockade during surgery.
- Minimize tissue trauma
- Facilitate surgical exposure
- Prevent patient movement
What is the significance of documenting the use of reversal agents?
To ensure safe monitoring and recovery of the patient.
What is the effect of autoimmunity on neuromuscular blockade?
Increased sensitivity to neuromuscular blockade drugs.
What should be monitored in patients receiving neuromuscular blockade?
Signs of complications and recovery from paralysis.
Fill in the blank: The use of _______ can help prevent fasciculations associated with succinylcholine.
non-depolarizing drugs
How does succinylcholine affect intraocular and intracranial pressure?
It increases both intraocular and intracranial pressure.
True or False: Succinylcholine is contraindicated in patients with a history of malignant hyperthermia.
True.
What is the historical significance of curare?
It was used by South American tribes for hunting and is a precursor to modern neuromuscular blockade drugs.
What is the importance of individualizing drug doses in anesthesia?
To account for the patient’s medical history and laboratory values.
What is the purpose of using a neuromuscular blocker that lasts longer?
To avoid the need for frequent redosing
Frequent redosing can complicate patient management and increase the risk of side effects.
How is the effective dose of a neuromuscular blocker measured?
By the 80-95% suppression of muscle twitch response
This measurement indicates that the drug is effectively causing neuromuscular blockade.
What is the significance of the order of muscle paralysis with neuromuscular blockers?
It helps determine which muscles are affected first and last during paralysis and recovery
Understanding this order is crucial for effective intubation and monitoring recovery.
Which muscles typically paralyze faster with neuromuscular blockers?
Small, rapidly moving muscles
Examples include eyelids and fingers, which respond quicker than larger muscles like the diaphragm.
What is the role of blood flow in the effectiveness of neuromuscular blockers?
Increased blood flow facilitates faster delivery of the drug to muscles
Muscles with better blood supply will experience faster paralysis and recovery.
Which muscle is considered the gold standard for recovery monitoring with neuromuscular blockers?
Adductor pollicis
It is used because it is a reliable indicator of neuromuscular recovery.
What does the presence of twitching in the orbicularis oculi indicate?
That paralysis may not be complete
This helps assess the depth of neuromuscular blockade.
What is the purpose of a nerve stimulator in anesthesia?
To assess neuromuscular function and monitor paralysis
It provides quantitative data on muscle response to stimulation.
What is a single twitch test?
A test where a single electrical stimulus is applied to assess muscle response
It helps determine if neuromuscular blockade is present.
What does the double burst stimulation evaluate?
Residual neuromuscular block by comparing two twitches
It provides a more sensitive measure of muscle response than a single twitch.
What is the significance of the train of four stimulation?
It provides a quantitative assessment of neuromuscular function by delivering four stimuli
The ratio of the fourth twitch to the first helps determine the level of blockade.
What does a train of four ratio greater than 0.4 indicate?
It is difficult to assess the degree of neuromuscular recovery accurately
Higher ratios suggest more reliable muscle function.
Fill in the blank: The diaphragm is a _______ muscle that takes longer to paralyze with neuromuscular blockers.
large
True or False: The laryngeal muscles paralyze faster than distal muscles like the feet.
True
What is the relationship between the first and fourth twitches in the train of four assessment?
The fourth twitch should be compared to the first to evaluate recovery
A ratio closer to 1 indicates better recovery.
What does it mean if the orbicularis oculi twitches during monitoring?
The patient is not fully paralyzed
This informs the clinician about the effectiveness of neuromuscular blockade.
What is the typical setting for the nerve stimulator when testing for twitch?
Start at 2 or 3 to avoid discomfort
Higher settings can cause painful stimulation.
What is the subjective nature of twitch response in neuromuscular monitoring?
Twitch response is very qualitative and subjective. Different individuals may perceive the strength of twitches differently.
What does a train of four ratio greater than 0.4% indicate?
It is very difficult to determine a good neuromuscular recovery feel.
What does a train of four ratio of 0.7 to 0.9 indicate?
It suggests that the patient is almost back to complete resolution, but significant neuromuscular blockade may still be present.
What is tetany in the context of neuromuscular monitoring?
Tetany is a rapid, continuous stimulation of 50 hertz for five seconds, resulting in a sustained muscle response.
What does a non-sustained response in tetany suggest?
It suggests either a non-depolarizing block or an overdose of succinylcholine.
What is post-tetanic stimulation?
Post-tetanic stimulation involves a single twitch three seconds after tetany to assess neuromuscular function.
What does a lack of response in post-tetanic stimulation indicate?
It indicates a very strong or deep paralysis at the neuromuscular junction.
What are common bedside tests for extubation?
- Negative inspiratory pressure * Eye opening * Hand squeezing * Toe wiggling * Tongue protrusion
What was the post-operative blockade rate in a study where no reversal agents were used?
The post-operative blockade rate was about 42%.
What effect did education about reversal agents have on their usage?
Usage of neostigmine increased from 6% to 42%, reducing post-operative blockade to less than 4%.
What is the resting membrane potential at the neuromuscular junction?
The resting membrane potential is approximately -90 millivolts.
What type of receptors are located at the neuromuscular junction?
Nicotinic acetylcholine receptors.
What happens when acetylcholine binds to its receptor?
It causes a conformational change that allows ions, especially sodium and potassium, to flow.
What is the key difference between depolarizing and non-depolarizing neuromuscular blockers?
Depolarizing blockers like succinylcholine cause fasciculations, while non-depolarizers do not.
What is the onset time and duration of succinylcholine?
- Onset time: 30 to 60 seconds * Duration: 3 to 5 minutes
What is the dosing guideline for succinylcholine?
The dose is 1 mg per kilogram of actual body weight.
What are the clinical uses of succinylcholine?
- Rapid intubation * Airway protection in trauma or emergencies * Situations with full stomachs
What is one of the side effects of succinylcholine?
It can release histamine.
What does a train of four response indicate in terms of neuromuscular function?
A train of four response indicates the level of neuromuscular blockade and recovery.
What does the presence of fasciculations indicate when using succinylcholine?
It indicates the drug is depolarizing the neuromuscular junction.
Fill in the blank: A post-tetanic stimulation response indicates a _______ level of paralysis.
lesser
What is succinylcholine used for?
Succinylcholine is a neuromuscular blocker used to facilitate intubation and muscle relaxation during surgery.
What can complicate ventilation in obese patients when using succinylcholine?
Obese patients may have a soft tissue airway, making it uncertain if they can be ventilated effectively.
What happens to serum potassium levels when succinylcholine is administered?
Serum potassium levels typically increase by about 0.5 milli equivalents.
Is succinylcholine contraindicated for all renal failure patients?
No, it is contraindicated only for renal failure patients with elevated potassium levels (6 or higher).
What is the difference between phase one and phase two blocks?
Phase one blocks are caused by depolarizing neuromuscular blockers like succinylcholine, while phase two blocks are caused by non-depolarizing blockers.
What is the typical dosing of succinylcholine?
The typical dose is 1 mg/kg of actual body weight.
How long does succinylcholine typically last?
Succinylcholine lasts about three to five minutes.
What is the role of dibucaine in testing for atypical plasma cholinesterase?
Dibucaine inhibits butyrylcholinesterase and is used to measure the effectiveness of succinylcholine breakdown.
What is the significance of a dibucaine number of 80?
A dibucaine number of 80 indicates normal plasma cholinesterase activity, allowing for normal metabolism of succinylcholine.
What effect does obesity have on succinylcholine metabolism?
Obesity quickens the breakdown of succinylcholine, shortening the duration of its effects.
What are common side effects of succinylcholine?
Common side effects include hyperkalemia, increased intracranial pressure, and increased intraocular pressure.
What is a pre-treatment with a non-depolarizing agent before succinylcholine intended to do?
It aims to reduce fasciculations and associated increases in intraocular and intracranial pressures.
Fill in the blank: Succinylcholine is metabolized by _______.
plasma cholinesterase
True or False: Neostigmine is effective in reversing the effects of succinylcholine.
False
What should be monitored when administering succinylcholine?
The patient’s response to ventilation, serum potassium levels, and any signs of prolonged neuromuscular blockade.
What factors can prolong the effects of succinylcholine?
- Abnormal plasma cholinesterase activity
- Liver failure
- Renal failure
- Genetic variations
What is the mechanism of action of succinylcholine?
It attaches to the alpha subunits of the acetylcholine receptor, causing depolarization and subsequent muscle paralysis.
What is the primary concern when giving succinylcholine to patients with liver failure?
They may not metabolize succinylcholine effectively, leading to prolonged neuromuscular blockade.
What is a common effect of succinylcholine on vision?
Blurriness of vision
This can cause the patient to feel weaker and unable to take a deep breath.
What cardiac dysrhythmias can occur with succinylcholine use?
Bradycardia, junctional rhythms, loss of P waves
These are generally not concerning and can offset each other.
Why should potassium levels be monitored before administering succinylcholine?
To prevent hyperkalemia, especially in patients with renal failure or muscle disorders
Conditions like burns or muscular dystrophy can predispose patients to hyperkalemia.
What side effect can succinylcholine cause related to muscle pain?
Myalgias and fasciculations
Patients may be advised to take Advil to manage post-treatment soreness.
What is myoglobinuria and its significance in patients receiving succinylcholine?
Release of myoglobin causing darker urine
It may indicate underlying conditions like malignant hyperthermia or muscular dystrophy.
How does succinylcholine affect intraocular pressure?
It increases intraocular pressure within 2-4 minutes of administration
This increase can be problematic for patients with glaucoma or open globe injuries.
What is the Monroe-Kelly theory related to intracranial pressure?
The cranium can only hold a fixed volume of brain, cerebrospinal fluid, and blood
An increase in one component must be compensated by a decrease in another.
What is malignant hyperthermia and its trigger?
A hereditary condition causing muscle destruction, triggered by succinylcholine or volatile anesthetics
It leads to rhabdomyolysis and release of myoglobin and potassium.
What is the recommended dose of succinylcholine for patients with myasthenia gravis?
1.5 to 2 mg/kg
Myasthenia gravis decreases acetylcholine receptors, requiring higher doses.
What is Lambert-Eaton syndrome and its effect on neuromuscular blockade?
An autoimmune disorder causing decreased release of acetylcholine, leading to increased sensitivity to neuromuscular blockers
Patients may require less succinylcholine than expected.
True or False: Succinylcholine is contraindicated in patients with an open globe injury.
True
This is an absolute contraindication due to the risk of increased intraocular pressure.
Fill in the blank: Succinylcholine can cause _______ in patients with a prolonged skeletal muscle contraction.
malignant hyperthermia
This can be indicated by sustained muscle rigidity.
What should be monitored when administering dantrolene for malignant hyperthermia?
Cardiac output
Dantrolene is a calcium channel blocker and may exacerbate hypotension.
What effect does hyperventilation have on cerebral blood flow?
It decreases cerebral blood flow by lowering CO2 levels
This can be a strategy to manage increased intracranial pressure.
What is a potential complication of rapid sequence induction when using succinylcholine?
Inability to hyperventilate the patient
This is critical for managing airway control and preventing aspiration.
What is the effect of increased sensitivity on depolarizers and non-depolarizer drugs?
It blocks a little bit earlier than expected, with less than expected.
What tool is recommended to check paralysis and residual paralysis?
A nerve stimulator.
Why is it important to check for paralysis during anesthesia?
To determine if there is still adequate blockade or if more is needed.
Fill in the blank: The effectiveness of paralysis monitoring is __________, no matter what The Book says.
individualized.
True or False: The effects of paralysis monitoring are the same for all patients.
False.
What factors contribute to the variability in monitoring paralysis?
Individual patient characteristics and timing of the procedure.
What is the potency of a neuromuscular blocking drug (NMBD)?
Equal Potency: dose necessary to produce 95% suppression of single twitch in the presence of nitrous/barbiturate/opioid anesthesia
Evaluated using adductor pollicis muscle with single twitch at 1Hz and ulnar nerve stimulation.
What is the resting membrane potential of the post-synaptic membrane at the neuromuscular junction (NMJ)?
-90 mV
Maintained by sodium/potassium nAChRs directly opposite.
What are the components of the synaptic cleft in the NMJ?
- Collagen
- Acetylcholinesterase
- 5,000-10,000 vesicles releasing ACh
The synaptic cleft is 20-50 nm wide and contains fluid.
What is the role of acetylcholinesterase in the NMJ?
Hydrolyzes ACh to acetic acid and choline
Located close to the synaptic cleft.
What is the structure of the nAChR?
Pentameric unit with 5 sub pores
Transmembrane structure that undergoes conformational change when ACh binds.
What happens when a neuromuscular blocking drug (NMBD) binds to nAChR?
No conformational change occurs, resulting in no ion flow
Probability of binding depends on concentration of NMBD vs ACh.
What are the characteristics of succinylcholine (SCh) as a depolarizing NMBD?
- Intense, rapid paralysis
- Offset of effects prior to hypoxia
- Useful for tracheal intubation
- Releases histamine
- Phase II block
SCh is the only depolarizing NMBD used in clinical practice.
What defines a Phase I block in neuromuscular blockade?
- Decreased contraction to single twitch stimulation
- Decreased amplitude to continuous stimulation
- TOF ratio > 0.7
- Absence of post-tetanic facilitation
- Skeletal muscle fasciculations
Typical of depolarizing NMBDs.
What is the onset and duration of succinylcholine when administered?
Onset: 30-60 seconds; Duration: 3-5 minutes
Not a good bedside criterion for extubation.
What is the significance of the TOF (Train of Four) ratio?
Amplitude of the 4th twitch to the 1st twitch indicates the degree of neuromuscular blockade
A TOFR of 0.5 indicates that the amplitude of the 4th twitch is 50% of the 1st.
What is the difference between depolarizing and non-depolarizing NMBDs?
- Depolarizing: Mimics action of acetylcholine
- Non-depolarizing: Interferes with action of acetylcholine
Examples include succinylcholine for depolarizing and pancuronium for non-depolarizing.
What are the side effects of succinylcholine?
- Cardiac dysrhythmias
- Hyperkalemia
- Myalgia
- Myoglobinuria
- Increased intragastric pressure
- Increased intraocular pressure
- Masseter spasm
These side effects can complicate the use of SCh.
What is Myasthenia Gravis?
Autoimmune disease with antibodies against ACh receptor leading to decreased ACh receptors
Symptoms include weakness, diplopia, and respiratory muscle weakness.
What is the mechanism of action of dantrolene?
Inhibits calcium release into the sarcoplasmic reticulum by affecting the ryanodine receptor
Reduces mortality in malignant hyperthermia.
What triggers malignant hyperthermia?
- All volatile anesthetics
- Succinylcholine
Associated with mutations in skeletal muscle calcium release.
What is the dibucaine number?
Reflects quality of normal variant butyrylcholinesterase activity
The lower the number, the greater the prolongation of succinylcholine effect.
What is the clinical significance of a TOFR below 0.4?
Experienced anesthetists may be unable to detect fade
Poor choice to administer reversal in this situation.
What is the effect of pretreatment with non-depolarizing NMBD?
Controversial efficacy in preventing side effects of succinylcholine
Some studies suggest it may reduce fasciculations.
What are the common side effects associated with cholinesterase inhibitors?
- Weakness
- Phlebitis
- Respiratory failure
- Gastrointestinal upset
Less common effects include confusion, dizziness, and drowsiness.
What is the typical duration of action for non-depolarizing NMBD?
Normal duration: 3-5 minutes
Termination occurs by diffusion out of NMJ into plasma.
What factors influence the order of neuromuscular blockade?
- Number of presynaptic ACh containing vesicles released
- Number of postsynaptic ACh receptors
- Blood flow to area
- Drug potency
Smaller, rapidly moving muscles block faster than larger muscles.
