Regional Anesthesia Flashcards

In spinal anesthesia, which factor most influences the spread of local anesthetic in the intrathecal space?

Answer: Baricity of the local anesthetic solution relative to CSF

Baricity (density relative to CSF) determines whether the solution is hyperbaric (sinks), hypobaric (rises), or isobaric (stays), making patient positioning and baricity the primary determinants of block spread.

The classic presentation of a 'high spinal' or 'total spinal' includes which combination of findings?

Answer: Severe hypotension, bradycardia, and respiratory arrest

When local anesthetic spreads to high thoracic/cervical levels, it blocks cardiac accelerator fibers (T1–T4) and the respiratory muscles (including the diaphragm at C3–C5), causing cardiovascular collapse and apnea.

During epidural anesthesia, a test dose of 3 mL of 1.5% lidocaine with 1:200,000 epinephrine is used to detect what?

Answer: Intravascular catheter placement (tachycardia) and intrathecal placement (rapid spinal block)

The epinephrine component causes a 20+ bpm heart rate increase if injected intravascularly, while the lidocaine dose would produce a rapid dense spinal block if injected intrathecally.

Interscalene brachial plexus block provides the best anesthesia for surgery on which area?

Answer: Shoulder and proximal humerus

The interscalene approach targets the brachial plexus at the C5–C7 roots, providing excellent coverage of the shoulder, clavicle, and proximal humerus while often missing the ulnar nerve (C8–T1).

What is the most serious complication specific to interscalene brachial plexus block?

Answer: Ipsilateral phrenic nerve palsy causing hemidiaphragm paralysis

Ipsilateral phrenic nerve block occurs in nearly 100% of interscalene blocks, reducing pulmonary function by about 25%, which is contraindicated in patients with severe respiratory disease.

Saddle block is a form of spinal anesthesia providing perineal anesthesia; it is achieved by using which technique?

Answer: Hyperbaric solution injected with patient sitting upright for 5–10 minutes

A saddle block uses a small volume of hyperbaric local anesthetic with the patient sitting; gravity restricts spread to the sacral nerve roots (S2–S5), anesthetizing the perineal 'saddle' area.