Electrolytes and Drug Effects Flashcards
Hypokalemia
- (Level < 3.5 mmol/L)
- EKG changes when K < 2.7
- Flattening/inversion of T waves
- ST depressions with prominent U waves
- T and U waves may fuse together
end result of hypokalemia
- Ventricular arrhythmias and death!
- Common causes: Diuretic medications, Vomiting & diarrhea
- Top tip: Hypokalemia & hypomagnesemia often go together. Check labs on both & replace both!
hyperkalemia
- (Level > 5.5 mmol/L)
- Lethal due to cardiac toxicity
- Narrowing and peaking of T waves
- PR interval prolongation
- Diminished or absent P waves
- Widening of QRS complexes (sine-wave pattern)
- Most commonly in kidney failure
drug/medication effects
- Numerous medications affect EKG
- Most are slight and non-specific
- Common examples (Anti-arrhythmics - Digoxin; Psychotropics; Methadone; Antibiotics - FQs)
Digoxin
- tx arrhythmias, CHF
- Positive inotropic effects
- Increase in AV nodal refractory period
- Adverse effects: HA, weakness, seizure, drowsiness
- Signs toxicity: anorexia, N/V, visual changes – yellow halo around objects, palpitation, dec HR
- Shortens QT interval & scooping of ST-T complex - “digitalis effect” - ST segment & T wave are fused together
digitalis effect
A – biphasic T wave
B – inverted T wave – terminal portion of T wave is pointed
C – inverted T (scooping) and positive U waves
Hypokalemia vs C – hypo you have inverted T and prominent U
anti-arrhythmics prolong ventricular repolarization
- e.g. quinidine, procainamide, disopyramide
- Cause QT interval prolongation & T wave flattening
- In toxic doses, may prolong ventricular depolarization - Lead to widening of QRS complexes, Prominent U waves resembling hypokalemia
hypothermia
- Body’s core temp < 95°F (35°C)
- Result in artifacts during shaking and slowed conduction through cardiac tissue
- Osborn/J waves most apparent in precordial and inferior leads (II, AVf, III)
- Disappear after body temperature normalized
- Degree of hypothermia correlates with prognosis
- May also occur with hypercalcemia
J waves/Osborn waves
- Positive deflections occurring at the junction between QRS complex and ST segment
- Seen in 80-85% of patients
- Strong positive correlation between Osborn wave size and degree of hypothermia
pulmonary embolism
- NOT a sensitive test for pulmonary embolism
- No single pattern diagnostic
Findings suggestive for pulmonary embolism:
- Sinus tachycardia
- Right ventricular strain pattern (inverted T in V1 to V4)
- S1Q3T3 pattern (likely d/t right ventricular dilation)
- ST segment depressions (ischemia)
- Incomplete/complete right bundle branch block
EKG Pre-op clearance
-ECG is not useful in asx patients undergoing low risk procedures
When to get pre-op EKG?
- Known coronary artery disease
- Significant arrhythmia
- Peripheral arterial disease
- Cerebrovascular disease
- Other significant structural heart disease
- Asymptomatic patients undergoing surgery with elevated risk
EKG pre-op clearance why get it and what to look for
Why get the EKG?
-Having a baseline EKG should a postoperative EKG be abnormal
What to look for?
- Presence of Q waves
- Significant ST-segment elevation or depression (myocardial ischemia or infarction)
- Left ventricular hypertrophy
- QTc prolongation
- Bundle-branch block
- Arrhythmia
pathological q waves
- Q wavescan be normal or abnormal
- When abnl → an ongoing or an old MI
- Q waveduration of > 40 milliseconds (one small box) or size > 25-33% of the QRS complex amplitude
continuous EKG monitoring
Holter Monitor - 24-48h
-a portable device that records the rhythm of the heart continuously, typically for 24–48 hours, by means of electrodes attached to the chest.
Ziopatch - Up to 14d
-TheZIO XT Patchis a single-channel continuous-recording ECG monitor, available by prescription, that can be worn up to 14 days by patients being evaluated for possible cardiac dysrhythmias
