Test Yourself: Can You Answer this Question from TrueLearn’s Anesthesiology SmartBank?
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Quality questions paired with detailed answer explanations allow residents to test themselves on the content and review the full context behind why answers are correct or incorrect.
Test yourself on TrueLearn’s anesthesiology question of the month, written by Ketan Chopra, MD, a resident at Detroit Medical Center. It has been singled out as one of the many outstanding new questions that were added to the bank in 2017!
TrueLearn’s Anesthesiology Question of the Month
Q: Which of the following is true regarding Parkinson Disease?
A. Levodopa cannot cross the blood brain barrier without the concomitant administration of carbidopa.
B. Levodopa should be continued on the day of surgery.
C. Parkinson disease is considered trinucleotide repeat disorder.
D. Treatment is aimed at increasing serotonin concentration.
The correct answer and answer explanations are listed below.
A Note From DR. James Lamberg
TrueLearn’s physician director Dr. James Lamberg notes: This topic really hits the nail on the head. The answer choice: “Levodopa cannot cross the blood brain barrier without the concomitant administration of carbidopa” is a phenomenal distractor. Most people with basic knowledge will know carbidopa and levodopa are given together, but it’s the “why” part that you don’t know unless you really understand the topic.
Answer choices like these really drive home the learning. When the test taker chooses this wrong answer based on their limited knowledge, it forces them to read why and then comes the better understanding. You don’t get this type of learning from regular textbook reading.
The Correct Answer Is: B
For patients with Parkinson disease, levodopa should be continued on the day of surgery.
Parkinson disease (PD) is a degenerative CNS disease caused by loss of dopaminergic cells in the basal ganglia of the brain. The characteristic pathologic feature is the presence of Lewy bodies in the neurons of the substantia nigra. Lewy bodies are aggregations of damaged proteins.
The etiology of PD is an interaction of genetic predisposition and unidentified environmental factors. Clinically, Parkinson disease, chronic manganese intoxication, phenothiazine or butyrophenone toxicity, Wilson disease, Huntington chorea, traumatic boxing injury, the effects of street drug toxins such as methylphenylterahydropyridine (MPTP), and carbon monoxide encephalopathy all have similar initial features: bradykinesia, muscular rigidity, and tremor.
The patient’s medications for Parkinson disease should be administered on the morning of surgery. Levodopa is the single most effective drug for patients with PD. The half-life of levodopa is short and interruption in therapy for more than six to 12 hours can result in severe skeletal muscle rigidity that interferes with ventilation.
Consultation with the patient’s neurologist and continuation of the patient’s drug regimen may avert complications. Apomorphine is a dopamine agonist that can be administered subcutaneously or intravenously if oral levodopa cannot be given.
Dopamine antagonists such as phenothiazines, droperidol, metociopramide should be avoided; note these are when administered rapidly. Propofol may result in dyskinesias during induction or upon emergence from an infusion. There are no reports of adverse responses to isoflurane, sevoflurane or desflurane. Patients being treated with dopamine agonists may be at increased risk for neuroleptic malignant syndrome (NMS).
Autonomic dysfunction is common. The most consistent cardiovascular finding is orthostatic hypotension that may be aggravated by the vasodilatory effects of anti-Parkinson drugs. Patients with PD are more likely to develop excessive decreases in blood pressure in response to inhaled anesthetics. Salivation and esophageal dysfunction are common in patients with PD and they may be at an increased risk for aspiration pneumonitis.
Answer A: Dopamine does not pass the blood-brain barrier, so its pre-cursor levodopa is used. Unfortunately, levodopa is decarboxylated to dopamine in the periphery and can cause nausea, vomiting, and arrhythmia. To avoid such side effects, levodopa is administered with carbidopa and entacopone. Carbidopa is peripheral decarboxylase inhibitor and entacopone is a catechol-O-methyltransferase inhibitor that increases the bioavailability of levodopa. Levodopa can cross the blodd-brain barrier without the assistance of any other medication.
Answer C: Huntington disease (HD) is a trinucleotide repeat disorder. Clinical features include choreiform movements, depression, and dementia. Onset is typically between 35 and 40 years of age, but can be late as 80 years. The disease continues to progress for several years and depression increases the possibility of suicide.
The medical literature is sparse with regard to the anesthetic management of patients with HD. Many of the manifestations of HD are typical of patients with neurodegenerative disorders. As the disease progresses, the pharyngeal muscles become dysfunctional and the risk of aspiration pneumonitis increases. As for any patient with a neurodegenerative disease, delayed emergence and ad increased likelihood of respiratory complications must be anticipated after surgery.
Although there are no specific contraindications to the use of inhaled or intravenous anesthetics, recovery from propofol may be faster than with other intravenous hypnotics. Short-acting muscle relaxants are preferable to long-acting relaxants. Decreased plasma cholinesterase activity may prolong the response to succinylcholine. Spinal anesthesia has been successfully used in patients with HD.
Answer D: Therapy is directed at (1) increasing the neuronal release of dopamine or the receptor’s response to dopamine, (2) stimulating the receptor directly with bromocriptine and lergotrile, (3) implanting dopaminergic tissue, or (4) decreasing cholinergic activity. Treatment as directed toward increasing dopamine levels in the brain, not serotonin.
Bottom Line: Parkinson disease is a degenerative disorder caused by loss of dopaminergic cells in the basal ganglia of the brain. Levodopa is used to increase dopamine concentrations in the treatment of Parkinson disease and dopamine-responsive dystonia.
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