Exam 3 review - CNS Stimulants & Anesthesia

CNS Stimulants - Anesthetic Considerations

• CNS stimulants increase alertness and concentration
• CNS stimulants increase muscle strength
• Perioperative acute intoxication can lead to increased blood pressure, tachycardia, and bronchodilation
• Acute intoxication increases Minimum Alveolar Concentration (MAC)
• Anesthetic requirements are higher with acute intoxification
• Actively induces emergence in isoflurane and propofol anesthesia with acute exposure
• With acute exposure increases arousal and respiratory drive
• Chronic exposure can lead to catecholamine depletion
• Chronic exposure results in decreased MAC
• Lower anesthetic requirements with chronic exposure
• Avoid indirect-acting vasopressors (ephedrine) when treating hypotension with chronic exposure
• Use direct-acting vasopressors or vasopressin
• Side effects of amphetamines and methylphenidate are hypertension, tachycardia, arrhythmias, weight loss, and insomnia
• The effects of increased heart rate and blood pressure from mixed amphetamine salts should be considered during anesthesia
• Doxapram stimulates medullary respiratory centers via carotid chemoreceptors
• Doxapram increases tidal volume and ventilation
• Doxapram can cause sympathetic nervous system outflow effects and CNS stimulation effects

Antiepileptics - Anesthetic Considerations

• It is important to know the last seizure date and what the seizure looks like
• Generally, antiepileptic drugs should not be held prior to surgery
• Hypoalbuminemia can increase the free concentration of antiseizure drugs
• Many are hepatic enzyme inducers
• Higher doses of propofol, thiopental, midazolam, opioids, and non-depolarizing muscle relaxants (NDMRs) may be needed
• Benzodiazepines are used for short-term treatment of acute seizures and status epilepticus
• Diazepam is preferred for local anesthetic toxicity
• Barbiturates are effective for most seizure types
• Levetiracetam is commonly used for seizure prophylaxis in neurosurgery, with a usual IV dose of 500 to 1000 mg
• Levetiracetam may cause an increase in blood pressure
• Phenytoin increases metabolism of non-depolarizing muscle relaxants
• Carbamazepine stabilizes sodium channels
• Valproic Acid can cause sedation and enzyme inhibition.

Parkinson's - Anesthetic Considerations

• There is a risk for autonomic dysfunction, including baseline orthostatic hypotension
• Temperature control is impaired
• Excess secretions are expected
• Pulmonary dysfunction increases aspiration risk
• There is potential for cognitive impairment and higher risk of post-operative delirium
• Generally, do not hold anti-Parkinsonian medications preoperatively
• Avoid antiemetics that affect the dopamine system
• Ondansetron is the preferred antiemetic
• Diphenhydramine can be given during anesthesia to treat extrapyramidal motor symptoms
• Assess baseline tremor and rigidity preoperatively
• Levodopa/carbidopa cardiovascular effects include orthostatic hypotension, tachycardia, and arrhythmias
• There is a risk of Parkinsonism Hyperpyrexia Syndrome with abrupt withdrawal of Levodopa/carbidopa

MOAs (Common Psych Drugs)

• SSRIs block the serotonin reuptake transporter
• SNRIs block reuptake of both serotonin and norepinephrine
• TCAs block serotonin and norepinephrine reuptake
• MAOIs inhibit monoamine oxidase, reducing breakdown of norepinephrine, dopamine, and serotonin
• Methylphenidate blocks reuptake of norepinephrine and dopamine, increases dopamine release

Serious Adverse Effects & Anesthetic Considerations

• SSRIs can cause Serotonin Syndrome
• SNRI’s can cause tachycardia, hypertension, arrhythmias and have an increased risk of serotonin syndrome.
• TCAs have anticholinergic and cardiovascular effects
• Avoid ephedrine and certain opioids with TCAs
• MAOIs have a risk of hyperadrenergic crisis with tyramine
• Contraindicated with indirect-acting sympathomimetics
• Treat hypotension with cautious use of phenylephrine while using MAOI's
• Lithium can cause dysrhythmias, hypotension, seizures, confusion and prolongs action of muscle relaxants
• Typical Antipsychotics can cause Extrapyramidal side effects and Neuroleptic Malignant Syndrome (NMS)
• Droperidol has a Black Box Warning for QT prolongation and arrhythmias
• Clonidine can cause hypotension and bradycardia

Treatments/Indications in Anesthesia

• Haloperidol can be used for emergence and ICU delirium, acute agitation/aggression, and as an antiemetic
• Droperidol is an effective antiemetic and sedative
• Diphenhydramine treats dystonia related to antipsychotics and can be used for symptom management of Parkinson's
• Clonidine is used as a regional anesthesia adjunct
• Ondansetron is the preferred antiemetic for patients with Parkinson's
• Propofol, etomidate, benzodiazepines, inhalation agents, and anticholinergics are generally safe with MAOIs in smaller doses
• Avoid ephedrine in patients taking MAOIs and TCAs