EEG Pharmacological and Metabolic Effects on EEG

Question 1

A patient on high-dose phenobarbital for status epilepticus shows a burst-suppression pattern on EEG. Which feature is most characteristic of drug-induced burst suppression compared to anoxic burst suppression?

Accepted Answer

Burst suppression is dose-dependent and reverses as the drug is metabolized

Answer

Drug-induced burst suppression (from barbiturates, propofol, or benzodiazepines) is dose-dependent and will improve as serum drug levels fall. Anoxic burst suppression following cardiac arrest is not dose-dependent and carries a far worse prognosis. This distinction is clinically critical for EEG interpretation in the ICU.

Question 2

Benzodiazepine administration typically produces which EEG change that a technologist should recognize and document?

Accepted Answer

Increase in frontocentral beta activity (14–30 Hz)

Answer

Benzodiazepines (and other GABA-A agonists such as barbiturates at sub-anesthetic doses) characteristically increase fast-frequency beta activity, most prominent over frontocentral regions. Recognizing drug-induced beta prevents misinterpretation as normal or abnormal endogenous activity.

Question 3

Triphasic waves with anterior-to-posterior phase lag are most classically associated with which metabolic condition?

Accepted Answer

Hepatic encephalopathy

Answer

Triphasic waves — high-amplitude, anteriorly dominant complexes with three phases and an anterior-to-posterior time lag — are the classic EEG hallmark of hepatic (portosystemic) encephalopathy, though they can also appear in renal failure and other toxic-metabolic states. Recognizing this pattern and its metabolic context is essential for accurate reporting.

Question 4

A critically ill patient is being actively cooled to 33°C for targeted temperature management after cardiac arrest. How does this temperature affect the EEG?

Accepted Answer

Progressively slows and suppresses EEG activity; may produce burst suppression or ECI at very low temperatures

Answer

Hypothermia is a potent EEG suppressant. At 33°C, background slowing and decreased amplitude are expected. As temperature falls further (below ~20°C), burst suppression and eventually ECI can occur — all reversible with rewarming. Failure to account for hypothermia when interpreting EEGs leads to false prognostication.

Question 5

An EEG technologist notes that a patient's EEG shows generalized high-amplitude rhythmic delta with superimposed faster frequencies. The patient's chart indicates a blood glucose of 28 mg/dL. The MOST likely explanation for this EEG pattern is:

Accepted Answer

Hypoglycemic encephalopathy producing diffuse metabolic slowing

Answer

Severe hypoglycemia deprives neurons of their primary energy substrate, producing diffuse encephalopathy with EEG slowing ranging from theta to delta frequencies, often with high amplitude. This metabolic encephalopathy reverses rapidly with glucose correction. The clinical context (blood glucose 28 mg/dL) makes this the most parsimonious explanation.

EEG - Electroencephalography Practice Test

EEG - Electroencephalography Practice Test

EEG Pharmacological and Metabolic Effects on EEG