Hepatic/pedia Flashcards
Which of the following chemicals is MOST responsible for the maintenance and autoregulation of hepatic blood flow?
The liver has a unique dual blood supply, receiving blood from both the hepatic artery, which arises from the celiac trunk, as well as the portal vein, which is a confluence of the venous drainage from the splanchnic circulation. The hepatic artery provides 25% of the blood flow and 50% of the oxygen supply to the liver, with the portal vein providing 75% of the blood flow to the liver but only 50% of the oxygen supply. The primary means of intrinsic autoregulation of hepatic blood flow is the hepatic arterial buffer response that causes adenosine-mediated vasodilation of the hepatic artery in response to decreased blood flow in the portal vein.
Which of the following will NOT lead to an increased work of breathing in a spontaneously breathing pediatric patient when using a circle system?
Tubular resistance, dead space, and valvular resistance may all increase the work of breathing in spontaneously ventilated patients. When dead space is increased, the pediatric patient must increase minute ventilation to a proportionately greater degree to maintain normocarbia. The size of the patient will determine the degree of increase (infants much higher than older children).
TrueLearn Insight : The most commonly used systems for pediatrics for anesthesia management in the surgical theater is the circle system with carbon dioxide absorbent. Mapleson D and F systems are commonly used for manual ventilation for transport and in the recovery room.
Some facts about Mapleson circuits:
Mapleson D, E and F circuits have no valves: if a circuit has no valves, it can result in rebreathing of exhaled gases if fresh gas flows are not high enough. Use of capnometry to determine if this is occurring can help guide the fresh gas flow rate. General rule – fresh gas flow should be at least 2.5 times the minute ventilation to decrease the risk of rebreathing.
Mapleson B and C are virtually never used in practice today.
Mapleson E is considered a T-piece.
Mapleson D and F circuits can be used with mechanical ventilation by removing the reservoir bag and connecting a ventilator
What is the mechanism by which benzodiazepines act as a muscle relaxant?
Benzodiazepines have centrally acting muscle-relaxing properties and potentiate the effects of GABA.
Which of the following would be the expected blood volume of a 30-kg (66-lb) 7-year-old boy?
Age Group Blood Volume (mL/kg) Premature infant 100 Full-term newborn 90 Infant (3 months to 1 year) 80 Child (1-12 years) 70 Adult male 65 Adult female 60
Which of the following is the MOST deleterious effect of neonatal hypothermia?
Neonates use nonshivering thermoregulation to control body temperature. A decline in temperature below 36° C (96.8° F) is likely to trigger this response. If left uncorrected, maladaptive physiological responses such as metabolic acidosis are likely to occur and could prove lethal for a neonate.
Which of the following immune responses is the pathophysiology of contact dermatitis?
A skin rash represents a cutaneous T cell mediated immune reaction.
A patient presents to the Emergency Department after three days of diarrhea. They are diagnosed with a Campylobacter jejuni infection and intravenous rehydration is started. If an arterial blood gas were collected, which of the following results would be the MOST likely?
Diarrhea causes a non-gap hyperchloremic metabolic acidosis and hypokalemia. Rarely it can lead to metabolic alkalosis. For metabolic acidosis, use the Winter formula to predict the compensatory change in PaCO2. Expected PaCO2 = (1.5 * [HCO3]) + 8 +/- 2. If the PaCO2 is significantly different then expected, suspect a mixed disorder.
TrueLearn Insight : Vomiting and Diarrhea come out of opposite ends. Vomiting goes up, and so does the pH (metabolic alkalosis). Diarrhea goes down, and so does the pH (metabolic acidosis). Vomiting = alkalosis. Diarrhea = acidosis.
Which of the following is seen in morbidly obese patients and helps explain the pharmacokinetic changes with succinylcholine seen in this patient population?
Obesity alters many physiologic compartments. Obese patients have increased butyrylcholinesterase activity and extracellular fluid volume, which affects the pharmacokinetics of succinylcholine. The exact dosage change is still up for debate, though most use total body weight.
TrueLearn Insight : Specific medications in anesthesia and how dosage should be calculated:
Total body weight: maintenance infusion dose of propofol, succinylcholine
Lean body weight: thiopental, induction dose of propofol, fentanyl
Ideal body weight: rocuronium, vecuronium
Still need more studies: dexmedetomidine, etomidate (although LBW is recommended based on the similar properties to propofol).
Jaundice and elevated bilirubin are noted in a 54-year-old male two days following an exploratory laparotomy. Which of the following is MOST TRUE regarding postoperative hepatic dysfunction?
Desflurane, as a consequence of trifluoroacetic acid (TFA) reactive intermediates, has been implicated in the formation of dangerous immunogenic compounds.
sevoflurane metabolism yields a compound hexafluoroisopropanol (HFIP), which does not accumulate and rapidly undergoes phase II biotransformation. This contributes to the low hepatotoxic potential for sevoflurane.
Which of the following describes midazolam bioavailability, from greatest to least? Assume a dose of 0.1 mg/kg for intramuscular, intranasal, and rectal dosing and 0.5 mg/kg for oral dosing.
Midazolam bioavailability among routes of administration (greatest to least): intravenous > intramuscular > intranasal > rectal > oral. Oral bioavailability is highly dependent on dose; bioavailability is lower with higher doses. This means that rectal bioavailability could potentially be lower than oral, but again it is dose dependent.
You are asked to evaluate a patient with unknown liver disease in the preoperative clinic. Which of the following is TRUE regarding this evaluation?
As a marker of liver synthetic function, serum albumin is inferior to prothrombin time due to its long half-life and lack of specificity for hepatic disorders.
A 66-year-old man with a history of end-stage liver disease, coronary artery disease, hypertension, and diabetes is scheduled to undergo emergent cardiac catheterization after being found unresponsive at home presumably secondary to cardiac arrest. He had return of spontaneous circulation 20 minutes after arrival to the emergency department. Shortly after vascular access is obtained in the operating room, the patient is noted to be bleeding from all IV insertion sites. Which of the following laboratory values would be most helpful in determining the cause of the patient’s bleeding?
Factor VIII can be used to help determine the underlying etiology of coagulation abnormalities in patients with liver disease. In coagulation disorders mostly attributable to DIC, factor VIII will be decreased. Coagulopathy due to end-stage liver disease without concomitant DIC will show a normal or elevated factor VIII level.
A 1-month-old infant is undergoing a modified Blalock-Taussig shunt for palliation until complete Tetralogy of Fallot repair can be performed. During inhalational induction, the patient becomes hypoxic and cyanotic despite adequate ventilation. Which of the following drugs will be MOST useful in this acute setting?
Tetralogy of Fallot is the most common and prototypical cyanotic congenital heart disease. Associated defects include VSD, overriding aorta, infundibular pulmonic stenosis, and RVH. The goals of anesthetic management include maintaining SVR, reducing heart rate and contractility, and ensuring adequate oxygenation and normocarbia. Phenylephrine is the drug of choice for preserving SVR. The modified Blalock-Taussig shunt allows deoxygenated blood to enter the pulmonary tree via the subclavian artery. This is a temporizing procedure and is reversed upon complete surgical repair.
TrueLearn Insight : Systemic vascular resistance can be increased by flexing the legs or by compressing the abdominal aorta directly. Children will squat during a hypercyanotic spell to increase their SVR and thus cause a decrease in the right-to-left shunt. Flexing the legs can also be used during induction of anesthesia for these patients.
Which of the following is the MOST effective medication to prevent postoperative nausea and vomiting in children?
Ondansetron is the most efficacious pharmacotherapy to prevent postoperative nausea and vomiting in pediatric patients.
TrueLearn Insight : Aprepitant is a neurokinin-1 (NK-1) receptor antagonist with similar efficacy to ondansetron in preventing early postoperative nausea and vomiting (PONV) and is significantly more effective at preventing late PONV (24-48 hours post-operatively).
Which of the following is NOT one of the potential sequelae of citrate intoxication in the setting of a rapid massive blood transfusion?
Citrate works by chelating both calcium and magnesium. This mechanism is why it is used as an anticoagulant in the storage of blood products. Citrate intoxication can occur during massive blood transfusion, which can lead to hypocalcemia (D), hypomagnesemia (B), and subsequent myocardial depression (A) or coagulopathy.
Ionized calcium levels begin to decrease when blood is transfused at 6 units/hr (35 mL/min). Hyperkalemia from transfusions occurs with blood infusions of 120 mL/min or more.
