Management of Local Anesthetic Systemic Toxicity — MCQs

10 questions

First step in management of raised intracranial pressure-

Which of the following anesthetic agents causes the LEAST severe complications when accidentally injected intra-arterially?

A child during anesthesia with halothane and succinylcholine develops severe stiffness of masseters. What is the most probable diagnosis?

Anesthetic agents causing bradycardia are all except:

Problems which may result from hypotensive anesthesia include:

What is the effect of adding epinephrine to lignocaine (a local anesthetic)?

A young male was administered regional anesthesia with 0.25% bupivacaine. The patient became unresponsive, and the pulse became unrecordable. What is the best management in this situation?

A 25 year old male with roadside accident underwent debridement and reduction of fractured both bones right forearm under axillary block. On the second postoperative day the patient complained of persistent numbness and paresthesia in the right forearm and the hand. The commonest cause of this neurological dysfunction could be all of the following except –

A patient selected for surgery was induced with Thiopentone iv through one of the antecubital veins and complained of severe pain of the whole hand. The next line of management is:

Q10

An 18 years old woman in the active stage of labour requests an epidural anaesthesia for delivery. Immediately following the epidural injection of 12ml of 2% lidocaine, the patient complains of lip numbness and becomes apprehensive. What is the presumptive diagnosis?

Management of Local Anesthetic Systemic Toxicity Indian Medical PG Practice Questions and MCQs

Question 1: First step in management of raised intracranial pressure-

A. Breathing
B. mannitol
C. Loading dose of phenytoin
D. Airway maintenance (Correct Answer)

Explanation: ***Airway maintenance*** - Maintaining a **patent airway** is the absolute first step in managing any critically ill patient, including those with raised ICP, to ensure adequate **oxygenation and ventilation** [1]. - Without proper airway management, the brain will suffer from **hypoxia**, which can worsen cerebral edema and further increase ICP, leading to a poorer prognosis. *Breathing* - While essential in the **ABCs (Airway, Breathing, Circulation)**, ensuring adequate breathing (ventilation) comes immediately after securing the airway [1]. - An obstructed airway will prevent effective breathing, making airway maintenance the priority. *mannitol* - **Mannitol** is an osmotic diuretic used to reduce ICP by drawing fluid from the brain into the vasculature, but it is a **pharmacological intervention** that follows initial stabilization of the ABCs. - Administering mannitol without first securing the airway and ensuring ventilation could be detrimental if the patient is hypoxic. *Loading dose of phenytoin* - Administering a **loading dose of phenytoin** is primarily for seizure prophylaxis or treatment, which may be necessary in some cases of elevated ICP, but it is not the **immediate first step** in managing acute ICP elevation. - Seizure control is important, but airway, breathing, and circulation take precedence in the initial stabilization phase.

Question 2: Which of the following anesthetic agents causes the LEAST severe complications when accidentally injected intra-arterially?

A. Thiopentone
B. Propofol (Correct Answer)
C. Methohexitone
D. Midazolam

Explanation: **Propofol** * **Propofol** has a relatively low incidence and severity of complications if accidentally injected intra-arterially because of its **lipid emulsion formulation** and mild irritant properties compared to other agents. * While any intra-arterial injection can cause problems, the milder venoconstriction and less direct tissue damage make its intra-arterial complication profile less severe than alternative agents. *Thiopentone* * **Thiopentone** (Thiopental) is highly alkaline, and accidental intra-arterial injection can cause **intense pain**, **vasospasm**, and **gangrene** due to precipitation in the arterioles and widespread endothelial damage. * This severe complication arises from its extreme pH and crystal formation, leading to profound ischemia. *Midazolam* * Accidental intra-arterial injection of **Midazolam** can cause **pain**, **spasm**, and **local tissue damage** due to its relatively acidic pH and solvent properties, though generally less severe than thiopentone. * While not as catastrophic as thiopentone, it can still lead to significant discomfort and localized vascular issues. *Methohexitone* * **Methohexitone** is also an alkaline barbiturate derivative, similar in nature to thiopentone, and its intra-arterial injection carries a significant risk of **vasospasm**, **pain**, and potentially **tissue necrosis**. * Its strong irritant properties and ability to precipitate within the vasculature make it a dangerous agent for inadvertent intra-arterial administration.

Question 3: A child during anesthesia with halothane and succinylcholine develops severe stiffness of masseters. What is the most probable diagnosis?

A. Malignant hyperthermia (Correct Answer)
B. Halothane hepatitis
C. Neuroleptic malignant syndrome
D. Anaphylaxis

Explanation: ***Malignant hyperthermia*** - **Masseter muscle rigidity** following exposure to **succinylcholine** and a **halogenated inhalational anesthetic** (like halothane) is a hallmark sign of malignant hyperthermia. - This inherited disorder results in uncontrolled **calcium release** from the sarcoplasmic reticulum in skeletal muscle, leading to hypermetabolism, severe muscle contraction, and a rapid rise in body temperature. *Halothane hepatitis* - This is an idiosyncratic liver injury that can occur hours to days after exposure to halothane, not an acute intraoperative event causing muscle stiffness. - Symptoms include elevated liver enzymes, jaundice, and often fever, but without the immediate muscle rigidity seen here. *Neuroleptic malignant syndrome* - This condition is associated with the use of **antipsychotic medications** and presents with muscle rigidity, fever, altered mental status, and autonomic instability. - It does not involve exposure to succinylcholine or inhalational anesthetics and has a slower onset, typically over days. *Anaphylaxis* - Anaphylaxis is a severe, acute allergic reaction characterized by **bronchospasm**, **hypotension**, **urticaria**, and angioedema. - While it can manifest rapidly during anesthesia, it does not typically cause severe, generalized muscle stiffness as the primary symptom.

Question 4: Anesthetic agents causing bradycardia are all except:

A. Procaine
B. Ketamine (Correct Answer)
C. Prilocaine
D. Bupivacaine

Explanation: ***Ketamine*** - Ketamine characteristically causes **sympathetic stimulation**, leading to an increase in **heart rate** and blood pressure, rather than bradycardia. - Its effects can be beneficial in patients with **hemodynamic instability** or compromised cardiac function. *Procaine* - Procaine, like other local anesthetics, can cause **bradycardia** and other cardiac depressant effects, especially at higher doses or with systemic absorption. - This effect is due to its action on **cardiac ion channels**, impairing impulse generation and conduction. *Prilocaine* - Prilocaine can induce **bradycardia**, similar to other amide-type local anesthetics, due to its direct depressant effects on myocardial function and conduction. - High doses can also lead to **methemoglobinemia**, which, while not directly causing bradycardia, complicates cardiovascular status. *Bupivacaine* - Bupivacaine is particularly known for its **cardiotoxic potential**, including severe **bradycardia** and arrhythmias, especially with accidental intravascular injection. - Its prolonged binding to **cardiac sodium channels** makes it more difficult to resuscitate from bupivacaine-induced cardiac arrest.

Question 5: Problems which may result from hypotensive anesthesia include:

A. Deep vein thrombosis
B. Reactionary hemorrhage
C. Retraction anemia
D. All of the options (Correct Answer)

Explanation: ***All of the options*** - Hypotensive anesthesia is a technique used to reduce **blood pressure** during surgery, aiming to decrease **blood loss** and improve the **surgical field visibility**. - While beneficial, it carries inherent risks including **deep vein thrombosis (DVT), reactionary hemorrhage**, and complications like **retraction anemia** if not managed properly. *Deep vein thrombosis (DVT)* - While hypotension might seem to reduce the risk by lowering **blood flow velocity**, prolonged immobility and potential for **venous stasis** during any surgery, especially under hypotension, can increase DVT risk. - The combination of **endothelial dysfunction** and **hypercoagulability** often seen in surgical patients, coupled with reduced peripheral blood flow due to hypotension, can contribute to DVT formation. *Reactionary hemorrhage* - This is a common post-operative complication where bleeding restarts hours after surgery. With hypotensive anesthesia, **blood vessels** are constricted and may not be actively bleeding during the surgery. - As the patient's **blood pressure** returns to normal post-operatively, these previously undetected bleeds can manifest as significant **hemorrhage** due to the increased pressure. *Retraction anemia* - This term is less commonly used in medical literature. However, it likely refers to the complications arising from prolonged tissue retraction during surgery, which, when combined with reduced **perfusion** from hypotensive anesthesia, can lead to **tissue ischemia** or damage akin to anemia in the affected area. - The reduced **oxygen delivery** to tissues during hypotensive states, especially when further compromised by retraction, may result in localized tissue injury or contribute to systemic complications if severe or prolonged.

Question 6: What is the effect of adding epinephrine to lignocaine (a local anesthetic)?

A. Increases distribution of local anesthetic
B. Decreases absorption of local anesthetic (Correct Answer)
C. Decreases duration of local anesthetic
D. Increases metabolism of local anesthetic

Explanation: ***Decreases absorption of local anesthetic*** - Epinephrine causes **vasoconstriction** at the site of injection, which reduces the rate at which the local anesthetic is absorbed into the systemic circulation. - This slower absorption leads to a **higher concentration of the anesthetic** at the nerve fibers, prolonging its effect and reducing systemic toxicity. - This is the primary mechanism by which epinephrine enhances local anesthetic efficacy. *Increases distribution of local anesthetic* - The primary effect of epinephrine is to **localize the anesthetic** by reducing its systemic distribution. - This localization is achieved through **vasoconstriction**, which keeps the drug at the desired site rather than allowing it to distribute widely. *Decreases duration of local anesthetic* - By slowing absorption, epinephrine effectively **increases the duration of action** of the local anesthetic. - The anesthetic remains at the site of action for a longer period, providing **extended pain relief**. *Increases metabolism of local anesthetic* - Epinephrine does not directly affect the **metabolic rate** of local anesthetics. - The primary mechanism of metabolism for amides like lignocaine is in the **liver** by cytochrome P450 enzymes.

Question 7: A young male was administered regional anesthesia with 0.25% bupivacaine. The patient became unresponsive, and the pulse became unrecordable. What is the best management in this situation?

A. ECPR with calcium
B. ECPR with dobutamine
C. ECPR with 20% intralipid (Correct Answer)
D. ECPR with sodium bicarbonate

Explanation: ***ECPR with 20% intralipid*** - The scenario describes **Local Anesthetic Systemic Toxicity (LAST)**, likely due to bupivacaine, leading to cardiovascular collapse. - **Intralipid 20%** is the first-line treatment for LAST-induced cardiovascular toxicity, as it acts as a lipid sink for the lipophilic local anesthetic. *ECPR with calcium* - While calcium may be used in certain cardiac arrest scenarios, it is **not the primary treatment for bupivacaine-induced cardiovascular collapse** and LAST. - Calcium might offer some cardiac support but does not directly neutralize the local anesthetic's toxic effects. *ECPR with dobutamine* - **Dobutamine is an inotropic agent** used to improve cardiac contractility but is not indicated as a primary rescue therapy for severe LAST. - It would not address the underlying toxicity caused by bupivacaine and could potentially worsen the situation by increasing myocardial oxygen demand without reversing toxin effects. *ECPR with sodium bicarbonate* - **Sodium bicarbonate** is used to treat metabolic acidosis and can be beneficial in certain drug overdoses to enhance excretion or stabilize cardiac membranes. - However, it is **not the primary or most effective treatment for bupivacaine-induced LAST** and cardiovascular collapse compared to lipid emulsion therapy.

Question 8: A 25 year old male with roadside accident underwent debridement and reduction of fractured both bones right forearm under axillary block. On the second postoperative day the patient complained of persistent numbness and paresthesia in the right forearm and the hand. The commonest cause of this neurological dysfunction could be all of the following except –

A. A tight cast or dressing
B. Systemic toxicity of local anaesthetics (Correct Answer)
C. Tourniquet pressure
D. Crush injury to the hand and lacerated nerves

Explanation: ***Systemic toxicity of local anaesthetics*** - **Systemic toxicity** of local anesthetics would typically manifest with symptoms like **seizures**, **cardiac arrhythmias**, or **respiratory depression** within minutes to hours of administration, not persistent numbness and paresthesia on the second postoperative day. - While local anesthetic toxicity can occur, its acute nature and generalized systemic effects make it an unlikely cause for delayed, localized neurological symptoms. *A tight cast or dressing* - A **tight cast or dressing** can cause **compression neuropathy**, leading to persistent numbness and paresthesia by putting pressure on nerves. - This is a common cause of **neurological dysfunction** following orthopedic procedures, especially in the forearm where nerves like the median or ulnar nerve can be vulnerable. *Tourniquet pressure* - **Tourniquet-induced nerve injury** can occur if the tourniquet is applied for too long or at excessive pressure, leading to **ischemia and direct compression** of nerves. - This can result in **postoperative numbness and paresthesia** that persists for days or weeks after surgery. *Crush injury to the hand and lacerated nerves* - A **crush injury** or laceration during the initial trauma, especially if severe, could directly damage nerves, causing **immediate and persistent numbness** and paresthesia. - Even after debridement and reduction, existing nerve damage from the trauma itself would manifest as prolonged neurological deficits.

Question 9: A patient selected for surgery was induced with Thiopentone iv through one of the antecubital veins and complained of severe pain of the whole hand. The next line of management is:

A. Leave it alone
B. IV ketamine through same needle
C. Give IV propofol through same needle
D. IV lignocaine through same needle (Correct Answer)

Explanation: **_IV lignocaine through same needle_** - **Lignocaine** (lidocaine) is a **local anesthetic** that can alleviate the severe pain caused by the extravasation or intra-arterial injection of thiopentone by **vasodilatation** and nerve block. - This immediate intervention helps to mitigate the consequences of thiopentone injection outside the vein or into an artery, which can include **vasoconstriction**, tissue necrosis, and **compartment syndrome**. *Leave it alone* - Ignoring the patient's complaint of severe pain, especially after thiopentone administration, could lead to **severe tissue damage**, including **vasoconstriction**, necrosis, and potential limb loss. - Doing nothing is a **negligent approach** that fails to address a potentially serious complication of intravenous drug administration. *IV ketamine through same needle* - **Ketamine** is a dissociative anesthetic and analgesic, but it is not the primary drug for managing local pain and potential vascular complications from thiopentone extravasation or intra-arterial injection. - Administering ketamine in this scenario would **not address the underlying vascular injury** or tissue irritation caused by thiopentone and might only mask the pain without resolving the issue. *Give IV propofol through same needle* - **Propofol** is an intravenous anesthetic that generally causes less pain on injection than thiopentone and has some vasodilatory properties, but it is not the immediate or primary treatment for managing the severe pain and potential vascular injury caused by thiopentone outside the vein or in an artery. - While it may offer some comfort, propofol does not have the **specific local anesthetic action** or immediate **vasodilatory effect** needed to reverse the harmful effects of thiopentone in this situation.

Question 10: An 18 years old woman in the active stage of labour requests an epidural anaesthesia for delivery. Immediately following the epidural injection of 12ml of 2% lidocaine, the patient complains of lip numbness and becomes apprehensive. What is the presumptive diagnosis?

A. Allergy to drug administered
B. Systemic toxicity to drug administered (Correct Answer)
C. Vasovagal shock
D. Drug entered SA space

Explanation: ***Systemic toxicity to drug administered*** - **Lip numbness** and apprehension immediately following epidural lidocaine injection are classic signs of **local anesthetic systemic toxicity (LAST)** due to unintended intravascular injection. - The rapid onset of symptoms suggests direct access to the systemic circulation via a blood vessel, leading to high plasma concentrations of lidocaine. *Allergy to drug administered* - Allergic reactions to local anesthetics are rare and typically involve **urticaria**, **bronchospasm**, or **anaphylaxis**, which are not described here. - Symptoms of allergy usually do not include lip numbness and apprehension as the primary manifestations. *Vasovagal shock* - Vasovagal reactions are characterized by **bradycardia**, **hypotension**, and syncope, usually triggered by pain or anxiety. - While apprehension is present, the specific symptom of lip numbness is not typical of a vasovagal response. *Drug entered SA space* - If the drug had entered the subarachnoid (SA) space, the patient would likely experience a **rapid onset of profound motor and sensory block**, potentially leading to **total spinal anesthesia** and respiratory compromise. - Lip numbness and apprehension are not primary indicators of inadvertent subarachnoid injection; rather, they point to systemic absorption.

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