Spinal Anesthesia: Subarachnoid Block

In a pregnant patient undergoing spinal anaesthesia, what physiological change most significantly contributes to the increased block height?

A patient undergoing a lower limb surgery develops significant hypotension immediately following spinal anaesthesia. Assuming standard resuscitative measures have been initiated, which vasopressor would be most appropriate if the patient has a known history of ischemic heart disease?

You are about to administer spinal anesthesia to an adult patient. Which anatomical landmark should guide your needle insertion to accurately target the L3-L4 interspace?

A patient undergoing epidural anesthesia experiences a sudden and rapid onset of motor blockade ascending to the cervical region, accompanied by difficulty breathing and loss of consciousness. What is the most likely cause?

Which factor least influences the spread and level of blockade achieved during spinal anesthesia?

Why are neuraxial techniques relatively contraindicated in patients with severe aortic stenosis?

A 30-year-old patient reports a severe headache 24 hours after an epidural for labor analgesia. The headache is significantly worse when she sits up. After conservative management fails, what is the next most appropriate step in managing this patient's headache?

During an interscalene brachial plexus block, a patient reports feeling acutely short of breath. What is the most likely cause of this symptom?

Which factor would most significantly prolong the duration of action of a local anesthetic administered for a peripheral nerve block.

How does the addition of sodium bicarbonate to lidocaine enhance its efficacy and speed of onset?

You are managing a patient who develops signs of bupivacaine toxicity following a peripheral nerve block. After ensuring adequate ventilation and circulation, what is the next immediate step in managing this toxicity?

What is the mechanism underlying the increased risk of local anesthetic systemic toxicity (LAST) in pregnant patients?

Which Mapleson circuit is least suited for controlled ventilation because it requires very high fresh gas flows to prevent rebreathing?

In a closed-circuit anesthesia system, what byproduct is formed when volatile anesthetic agents like sevoflurane interact with desiccated (dried-out) carbon dioxide absorbent?

What is the primary mechanism by which soda lime removes carbon dioxide ($CO_2$) from the breathing circuit?

A surgeon is performing a lengthy procedure and requests that the anesthesia team use a peripheral nerve block to provide postoperative analgesia. Which local anesthetic would be most appropriate in this scenario to provide the longest duration of pain relief with a single injection?

During a surgical procedure, a patient's end-tidal $CO_2$ abruptly rises from 35 mmHg to 65 mmHg. The patient's minute ventilation is unchanged. Assuming the capnograph is functioning correctly, what is the most likely cause of this sudden increase in end-tidal $CO_2$?

What is the rationale behind using dilute concentrations of bupivacaine (e.g., 0.0625%) combined with an opioid (e.g., fentanyl) for labor analgesia?

What is the most likely mechanism by which Horner's syndrome occurs as a complication of interscalene brachial plexus block?

During a Bier block procedure, after injecting the local anesthetic, the patient suddenly complains of dizziness, tinnitus, and circumoral numbness. What is the most appropriate immediate action?