Neuromuscular Monitoring — MCQs
Probable indicators of reversal of neuromuscular blockade are all EXCEPT:
A patient admitted after a road traffic accident is put on mechanical ventilation. He opens his eyes on verbal command and moves all four limbs spontaneously. Calculate his GCS.
Train of four' is characteristically used in concern with
Train of four fade is a characteristic feature of:
Most commonly used nerve for monitoring during anesthesia
The image given below shows neuromuscular monitoring of the patient after anesthesia. What is the most commonly used nerve for monitoring?
Stage 2 block (Phase II block) is seen with:
Neuromuscular monitoring shows TOF ratio 0.7. This indicates:
A 40–year female has to undergo incisional hernia surgery under general anaesthesia. She complains of awareness during her past cesarean section. Which of the following monitoring techniques can be used to prevent such awareness ?
Artery cannulated most commonly for invasive blood pressure monitoring is:
Neuromuscular Monitoring Indian Medical PG Practice Questions and MCQs
Question 1: Probable indicators of reversal of neuromuscular blockade are all EXCEPT:
- A. Sustained hand grip for 5 seconds
- B. Lift head for 5 seconds
- C. Leg lift for 10 seconds (Correct Answer)
- D. Ability to perform sustained tongue depressor test
Explanation: ***Leg lift for 10 seconds*** - A **leg lift for 10 seconds** is a test of lower limb strength, which can be affected by residual neuromuscular blockade, but it is **not a primary or standard indicator** used to assess the reversal of neuromuscular blockade for airway protection and overall recovery. - While it demonstrates muscle strength, it isn't as critical for assessing readiness for extubation as upper airway and respiratory muscle function tests. *Sustained hand grip for 5 seconds* - **Sustained hand grip for 5 seconds** demonstrates adequate neuromuscular transmission in the forearm muscles and is a generally accepted indicator of reversal of neuromuscular blockade. - It suggests sufficient recovery of peripheral muscles to perform voluntary movements effectively. *Lift head for 5 seconds* - The **ability to lift the head off the bed for 5 seconds** is a crucial clinical test indicating significant recovery of the neck and upper airway muscles, which are vital for maintaining airway patency. - This demonstrates adequate strength in the diaphragm, intercostals, and upper airway muscles, suggesting readiness for extubation. *Ability to perform sustained tongue depressor test* - The **sustained tongue depressor test** involves the patient holding an object between their teeth, indicating sufficient strength of the jaw musculature. - This test is a reliable indicator of adequate neuromuscular recovery in the muscles essential for airway protection and swallowing.
Question 2: A patient admitted after a road traffic accident is put on mechanical ventilation. He opens his eyes on verbal command and moves all four limbs spontaneously. Calculate his GCS.
- A. Eyes-3, Verbal -NT, Motor-6 (Correct Answer)
- B. Eyes -3, Verbal-1, Motor -6
- C. Eyes-2, Verbal -1, Motor -5
- D. Eyes-2, Verbal -NT, Motor -5
Explanation: ***Eyes-3, Verbal -NT, Motor-6*** - **Eyes opening to verbal command** scores 3 points on the GCS [1]. - The patient is on **mechanical ventilation**, meaning their verbal response cannot be assessed, leading to a "Non-Testable" (NT) score for verbal [1]. **Spontaneous movement of all four limbs** indicates full motor function, scoring 6 points [2]. *Eyes -3, Verbal-1, Motor -6* - While **eyes opening to verbal command** (3 points) and **spontaneous motor movement** (6 points) are correct, a verbal score of 1 implies **no verbal response** if the patient were able to speak, which is not applicable here due to mechanical ventilation. *Eyes-2, Verbal -1, Motor -5* - **Eyes opening to pain** scores 2, but the patient responded to verbal command. A verbal score of 1 is for no response, and a motor score of 5 indicates localizing to pain, not spontaneous movement. *Eyes-2, Verbal -NT, Motor -5* - **Eyes opening to pain** scores 2, but the patient responded to verbal command (3 points). While **Verbal-NT** is correct due to mechanical ventilation, a motor score of 5 (localizes to pain) is incorrect, as the patient moved limbs spontaneously (6 points).
Question 3: Train of four' is characteristically used in concern with
- A. Malignant hyperthermia
- B. Mechanical ventilation
- C. To check hemodynamic parameters
- D. Non-depolarizing neuromuscular blockers (Correct Answer)
Explanation: ***Non-depolarizing neuromuscular blockers*** - The **train-of-four (TOF)** stimulus is a method used to monitor the depth of **neuromuscular blockade** induced by drugs like non-depolarizing neuromuscular blockers. - It involves applying four supramaximal electrical stimuli to a peripheral nerve, and the ratio of the fourth twitch to the first twitch is measured to assess the degree of blockade. *Malignant hyperthermia* - **Malignant hyperthermia** is a severe, life-threatening pharmacogenetic disorder triggered by certain anesthetic agents, leading to high body temperature and muscle rigidity. - It is diagnosed through clinical signs and a **caffeine halothane contracture test**, not primarily with TOF monitoring. *Mechanical ventilation* - **Mechanical ventilation** is a life-support treatment that helps patients breathe when they cannot do so effectively on their own. - While patient comfort and adequate ventilation are essential, TOF is not a direct monitoring tool for the efficacy or parameters of mechanical ventilation itself, though it can be used to assess the level of paralysis for intubation. *To check hemodynamic parameters* - **Hemodynamic parameters** include measurements such as blood pressure, heart rate, cardiac output, and central venous pressure, which assess the circulatory system's function. - These parameters are typically monitored using devices like arterial lines, central venous catheters, and ECG, not by train-of-four stimulation.
Question 4: Train of four fade is a characteristic feature of:
- A. Non depolarizing block (Correct Answer)
- B. Depolarizing block
- C. Both depolarizing and non-depolarizing block
- D. Malignant hyperthermia
Explanation: ***Non depolarizing block*** - A **train-of-four (TOF) fade** is a hallmark of **non-depolarizing neuromuscular block**, due to the competitive antagonism of acetylcholine at the postsynaptic receptor. - The first twitch depletes a portion of readily releasable acetylcholine, and the subsequent twitches show progressive fade because less acetylcholine is released with each successive stimulus. *Depolarizing block* - In a **Phase I depolarizing block**, there is **no fade** with TOF stimulation because the acetylcholine receptor is continuously activated, leading to sustained depolarization. - During prolonged exposure to a depolarizing agent, a Phase II block may develop which *can* exhibit fade, but this is a secondary phenomenon, and the primary characteristic of a depolarizing block is lack of fade. *Both depolarizing and non-depolarizing block* - While a **Phase II depolarizing block** can show fade, it is not a *characteristic* feature of all depolarizing blocks, distinguishing it from the consistent fade seen in non-depolarizing blocks. - The primary action of depolarizing agents (Phase I block) does not involve fade, making this option incorrect as a universal characteristic. *Malignant hyperthermia* - **Malignant hyperthermia** is a hypermetabolic crisis triggered by certain anesthetic agents, primarily involving uncontrolled calcium release from the sarcoplasmic reticulum, not directly related to neuromuscular blockade monitoring patterns. - While muscle rigidity can be a symptom, it does not manifest as a **train-of-four fade**, which is specific to postsynaptic acetylcholine receptor interactions.
Question 5: Most commonly used nerve for monitoring during anesthesia
- A. Facial nerve
- B. Ulnar nerve (Correct Answer)
- C. Radial nerve
- D. Median nerve
Explanation: ***Ulnar nerve*** - The **ulnar nerve** is most commonly used for **neuromuscular monitoring** during anesthesia due to its accessibility at the wrist and predictable response to stimulation. - Stimulation typically elicits an adductor pollicis contraction, which is easily observed and quantified with various monitoring devices. *Facial nerve* - The **facial nerve** is primarily monitored during **neurosurgical procedures** where facial nerve integrity is at risk, such as parotidectomy or acoustic neuroma resection. - While it can be monitored, it is not the standard choice for general neuromuscular blockade assessment due to its complex innervation patterns and the need for specific electrode placement. *Radial nerve* - The **radial nerve** is less frequently used for standard neuromuscular monitoring compared to the ulnar nerve. - Its stimulation can lead to more variable and less quantifiable thumb or finger extension, making it less ideal for precise assessment of blockade depth. *Median nerve* - The **median nerve** can be used for neuromuscular monitoring, often stimulating the thenar muscles to produce thumb flexion. - However, it is generally considered a secondary site compared to the ulnar nerve due to greater anatomical variability in electrode placement and response.
Question 6: The image given below shows neuromuscular monitoring of the patient after anesthesia. What is the most commonly used nerve for monitoring?
- A. Ulnar nerve (Correct Answer)
- B. Median nerve
- C. Radial nerve
- D. Metacarpal nerve
Explanation: ***Ulnar nerve*** - The **ulnar nerve** is the most commonly chosen site for neuromuscular monitoring due to its ease of accessibility and predictable response of the **adductor pollicis muscle**. - Stimulation of the ulnar nerve at the wrist causes **adduction of the thumb**, which is easily quantifiable and provides reliable information about neuromuscular blockade. *Median nerve* - While the median nerve can be monitored, it is **less commonly used** than the ulnar nerve due to potential for confusing responses or less clear twitch measurements. - Stimulation of the median nerve primarily leads to **flexion of the thumb and fingers**, but the adductor pollicis response from ulnar nerve stimulation is often preferred for its clear isolation. *Radial nerve* - The radial nerve innervates muscles involved in **wrist and finger extension**, which are not typically targeted for standard neuromuscular monitoring. - Its stimulation can be more complex to interpret and may not provide the precise information needed for monitoring paralytic depth in the same way as the ulnar nerve. *Metacarpal nerve* - The term "metacarpal nerve" is broad and refers to nerves near the metacarpals, which are **not primary sites** for direct neuromuscular blocking agent monitoring. - Specific named peripheral nerves like the ulnar, median, or radial nerves are targeted for their predictable muscle responses, not generalized metacarpal innervation.
Question 7: Stage 2 block (Phase II block) is seen with:
- A. Isoflurane
- B. Enflurane
- C. Suxamethonium (Correct Answer)
- D. Sevoflurane
Explanation: ***Suxamethonium*** - **Suxamethonium** (succinylcholine) is a depolarizing neuromuscular blocker that can cause a **Phase II block** with prolonged or high-dose administration. - Phase II block, also known as **desensitization block**, clinically resembles a non-depolarizing block and can be antagonized by **anticholinesterases**. *Isoflurane* - **Isoflurane** is an inhaled anesthetic that causes muscle relaxation by enhancing the effects of non-depolarizing neuromuscular blockers, but does not directly induce a Phase II block. - It primarily acts on GABA receptors in the CNS to produce anesthesia and has minimal direct effect on **nicotinic acetylcholine receptors** at the neuromuscular junction. *Enflurane* - **Enflurane** is another inhaled anesthetic that, similar to isoflurane, potentiates neuromuscular blockade but does not directly cause a **Phase II block**. - Its effects are primarily on the **central nervous system**, contributing to anesthesia and muscle relaxation through central mechanisms. *Sevoflurane* - **Sevoflurane** is a commonly used inhaled anesthetic that also enhances the effects of neuromuscular blockers but does not cause a unique **Phase II block** itself. - Like other volatile anesthetics, it facilitates muscle relaxation, thereby reducing the dose of neuromuscular blockers required.
Question 8: Neuromuscular monitoring shows TOF ratio 0.7. This indicates:
- A. Adequate recovery
- B. Complete recovery
- C. Partial recovery (Correct Answer)
- D. Deep block
Explanation: ***Partial recovery*** - A **TOF ratio of 0.7** indicates significant recovery from neuromuscular blockade, but not full return to baseline. - This level might allow for some spontaneous movements but could still pose a risk for **post-operative respiratory complications** due to residual weakness. *Adequate recovery* - Adequate recovery is generally considered when the **TOF ratio is 0.9 or greater**, indicating near-normal muscle function and reduced risk of residual block complications. - At a TOF ratio of 0.7, although significant recovery has occurred, the patient is still susceptible to **airway obstruction** and **hypoventilation**. *Complete recovery* - **Complete recovery** from neuromuscular blockade is defined by a TOF ratio of **1.0**, meaning the fourth twitch is equal in amplitude to the first, indicating no residual paralysis. - A TOF ratio of 0.7 does not signify complete recovery as there is still a noticeable fade in subsequent twitches. *Deep block* - A **deep block** would be characterized by a very low TOF ratio or the absence of all four twitches in the train-of-four stimulus. - A TOF ratio of 0.7 clearly shows the presence of all four twitches, negating the possibility of a deep block.
Question 9: A 40–year female has to undergo incisional hernia surgery under general anaesthesia. She complains of awareness during her past cesarean section. Which of the following monitoring techniques can be used to prevent such awareness ?
- A. Color doppler
- B. Transesophageal echocardiography
- C. Bispectral index monitoring (Correct Answer)
- D. Pulse plethysmography
Explanation: ***Bispectral index monitoring*** - **Bispectral Index (BIS) monitoring** is a technology that processes electroencephalogram (EEG) signals to provide a numerical value (0-100) indicating the patient's **level of consciousness or depth of anesthesia**. - A lower BIS value (typically 40-60) indicates a suitable depth of anesthesia for surgery, helping to prevent **intraoperative awareness**, especially in patients with a history of it. *Color doppler* - **Color Doppler** is an imaging technique used to visualize blood flow in vessels and assess the speed and direction of flow. - It is primarily used to diagnose conditions like **deep venous thrombosis**, *arterial stenosis*, or to evaluate blood flow to organs, and has no direct role in monitoring depth of anesthesia. *Transesophageal echocardiography* - **Transesophageal echocardiography (TEE)** is an invasive imaging technique that uses ultrasound from a probe inserted into the esophagus to provide detailed images of the heart. - TEE is critical for assessing **cardiac function**, *valvular heart disease*, or *aortic dissection* during surgery, but it does not monitor brain activity or the depth of anesthesia. *Pulse plethysmography* - **Pulse plethysmography** is a non-invasive method that measures changes in blood volume in a part of the body, often used to determine **heart rate** and assess peripheral perfusion. - While it is a component of pulse oximetry, it does not provide information about the **depth of anesthesia** or brain activity.
Question 10: Artery cannulated most commonly for invasive blood pressure monitoring is:
- A. Radial artery (Correct Answer)
- B. Femoral artery
- C. Ulnar artery
- D. Carotid artery
Explanation: ***Radial artery*** - The **radial artery** is the most common site due to its **superficial location**, ease of access, and presence of collateral circulation via the **ulnar artery** (Allen's test). - This allows for safe cannulation with a low risk of **ischemia** to the hand, even if the radial artery becomes thrombosed. *Femoral artery* - The **femoral artery** is used, especially in emergencies or when radial access is not possible, but it carries a higher risk of **infection** and hematoma. - Its deep location can make cannulation more challenging, and complications like **retroperitoneal hemorrhage** are possible. *Ulnar artery* - The **ulnar artery** is generally avoided for primary arterial cannulation because the radial artery is the more dominant blood supply to the hand. - Cannulating the ulnar artery carries a higher risk of **ischemia** to the hand if an anatomical anomaly exists or if the radial artery's collateral flow is compromised. *Carotid artery* - The **carotid artery** is rarely, if ever, cannulated for routine invasive blood pressure monitoring due to the significant risk of **neurological complications** such as stroke or cerebral embolism. - This artery supplies blood directly to the brain, and any damage or clot formation during cannulation could have devastating consequences.
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