CRNA Procedures Practice Questions (210 Flashcards)

This is **overdamping**. Common causes include air bubbles, blood clots, or long/compliant tubing. Effect: Systolic BP is underestimated, and diastolic BP is overestimated (MAP remains relatively accurate). Strategy: NBCRNA often tests the under-over rule: Overdamping = Under-estimates SBP. Clinical pearl: Always check for air bubbles in the transducer or tubing first when the waveform appears rounded.

DPE involves puncturing the dura with a spinal needle before placing the epidural catheter, but no spinal drugs are given. This "vent" allows better trans-dural spread of epidural local anesthetics into the subarachnoid space. Benefits include: faster onset of sacral coverage (S1-S2), more symmetric block, and lower incidence of "patchy" blocks compared to standard epidurals, without the hemodynamic instability or pruritus sometimes seen with CSE. This is a high-yield 2026 exam topic.

The Common Peroneal (Fibular) nerve is being stimulated. Yes, this is an acceptable endpoint, though some practitioners prefer Tibial stimulation (plantar flexion/inversion) as it is often more robust for foot surgery. Current 2026 standards emphasize that either branch stimulation at <0.5 mA suggests proximity. Clinical Pearl: Eversion/Dorsiflexion = Peroneal; Inversion/Plantarflexion = Tibial. Distractors often swap these actions.

In the lateral decubitus position with OLV: 1. Perfusion (Q): Gravity favors the dependent (lower, ventilated) lung (approx. 60-80% of blood flow). 2. Ventilation (V): 100% of ventilation goes to the dependent lung. 3. Shunt: The non-dependent (upper, non-ventilated) lung continues to receive 20-40% of cardiac output, creating a large right-to-left intrapulmonary shunt. \n\nHPV (Hypoxic Pulmonary Vasoconstriction) normally reduces this shunt by 50% by diverting blood away from the hypoxic, collapsed lung. Factors that blunt HPV (vasodilators, high MAC, hypocapnia) will worsen the shunt and hypoxemia.

The combination increases Intracranial Pressure (ICP) through two mechanisms: 1. Trendelenburg position impairs venous drainage from the cranium. 2. CO2 absorption causes respiratory acidosis and cerebral vasodilation, increasing cerebral blood volume. While Cerebral Perfusion Pressure (CPP = MAP - ICP) is usually maintained because MAP also rises, patients with pre-existing high ICP are at risk for cerebral herniation or ischemia. Exam Tip: In these patients, maintain strict normocapnia and minimize the degree/duration of Trendelenburg.