anesthesia and analgesia for foals

Question 1

Foals may be treated anesthesiologically like young adults when they have acquired mature cardiopulmonary function and metabolic pathways at __ to __ ___________ of age.

Answer 1

4 to 5 months

Question 2

The microsomal cytochrome ____ _______ system is primarily responsible for transformating lipophilic compounds to polar and pharmacologically less-active or inactive substances (phase I reactions), whereas _____________ and other conjugation processes (phase II reactions) render the metabolites more hydrophilic, facilitating ______ elimination.

Answer 2

P450 enzyme; glucuronidation; renal

Question 3

T/F: Functional maturity of the liver is incomplete at birth and thus the capacity to metabolize endogenous substances such as bilirubin or drugs is markedly lower in newborn foals than in the adult horse.

Answer 3

True

Question 4

T/F: Metabolism and half-lives of organic waste products (e.g., bilirubin) are expected to be prolonged causing higher plasma concentrations to persist in the newborn foal.

Answer 4

True; Likewise drugs have longer plasma half-lives and may accumulate on repeated dosing, thereby extending effects and slowing elimination from the body.

Question 5

What is the normal blood volume in adult horses? what is the normal blood volume in neonatal foals?

Answer 5

8-10% of total body weight (adult)

13-15% of total body weight (foals)

Question 6

T/F: Serum enzyme activities (including creatinine kinase, sorbitol dehydrogenase, γ-glutamyl transferase, lactate dehydrogenase, and aspartate aminotransferase) have been reported to be transiently elevated in the first few weeks after birth as a result of hepatocellular maturation.

Answer 6

True

Question 7

What reversal agents are available to antagonize benzodiazepines?

Answer 7

sarmazenil (IV) and flumazenil, (IV)

Question 8

What reversal agents are available to antagonize opiods?

Answer 8

naloxone (IV) and levallorphan (IV)

Question 9

What reversal agents are used in foals to antagonize the effects of xylazine in foals?

Answer 9

yohimbine (IV or IM), atipamezole (IV or IM), and tolazoline

Question 10

T/F: The PaCO2 changes proportionately with metabolic activity and hence production of CO2 in the body and inversely with its elimination (i.e., alveolar ventilation).

Answer 10

True

Question 11

Under physiologic conditions ETCO2 changes with alveolar PCO2 (PACO2) and therefore with PaCO2, with some predictable inaccuracy. An ETCO2 value in excess of 45 mm Hg (__________) indicates ____________, a value below 35 mm Hg (_________) indicates _______________.

Answer 11

hypercapnia; hypoventilation; hypocapnia;hyperventilation

Question 12

T/F: Changes in ETCO2, whether sudden or gradual, may reflect changes in circulatory function (CO) as blood transports CO2 from the periphery to the lungs.

Answer 12

True

Question 13

T/F: In the foal, multiple factors may contribute to severe respiratory depression and impairment of pulmonary gas exchange leading to poor arterial oxygenation and CO2 retention: persistent pulmonary hypertension, drug-induced central respiratory center depression, reduced FRC, exhaustion of respiratory muscles from increased work of breathing, immature lung, lung disease, and airway obstruction.

Answer 13

True

Question 14

What would be a reason for why PaCO2 would increase without an increase in ETCO2?

Answer 14

increased alveolar dead space (secondary to low cardiac output, or pulmonary embolism); leaks in the sampling lines

Question 15

What is FRC?

Answer 15

Functional residual capacity is the gas volume left in the lung after a normal expiration.

Question 16

What three fetal anatomic structures allow for bypass of the pulmonary circulation?

Answer 16

ductus arteriosus (by-pass the lungs), foramen ovale, ductus venosus (by-pass the liver)