Basic Sciences Flashcards

In a patient with renal failure, which muscle relaxant is MOST appropriate due to organ-independent elimination?

Answer: Cisatracurium

Cisatracurium undergoes Hofmann elimination (spontaneous non-enzymatic degradation at physiological pH and temperature), making it independent of renal or hepatic function.

The cerebral metabolic rate for oxygen (CMRO2) is coupled to cerebral blood flow (CBF) through which mechanism?

Answer: Metabolic autoregulation via local vasoactive metabolites

Increased neuronal activity produces CO2, H+, K+, and adenosine, which act as local vasodilators coupling metabolic demand to blood flow.

Propofol's mechanism of action primarily involves:

Answer: Positive allosteric modulation of GABA-A receptors

Propofol enhances inhibitory chloride currents by binding to GABA-A receptors at a site distinct from benzodiazepines, potentiating GABAergic neurotransmission.

The pulmonary vascular resistance (PVR) is LOWEST at which lung volume?

Answer: Functional residual capacity (FRC)

At FRC, both alveolar vessels (compressed at high volumes) and extra-alveolar vessels (collapsed at low volumes) are at their optimal diameter, minimizing total PVR.

Which coagulation pathway is assessed by the prothrombin time (PT/INR)?

Answer: Extrinsic pathway (factors VII, X, V, II, I)

PT measures the extrinsic pathway initiated by tissue factor (FIII) + FVII, then the common pathway; it is prolonged by warfarin which inhibits vitamin K-dependent factors II, VII, IX, X.

Hypoxic pulmonary vasoconstriction (HPV) serves which physiological purpose?

Answer: Diverting blood from poorly ventilated lung regions to better-ventilated areas

HPV constricts pulmonary arterioles in hypoxic lung segments, redirecting blood to better-oxygenated alveoli to optimize V/Q matching and arterial oxygenation.

The osmotic pressure exerted by plasma proteins (mainly albumin) across the capillary wall is termed:

Answer: Colloid oncotic pressure

Colloid oncotic pressure (~25 mmHg) is generated by large plasma proteins that cannot freely cross the capillary membrane, opposing fluid filtration into the interstitium.