Critical-Cardiac
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Anatomy and physiology review A. Layers B. Chambers C. Heart valves D. Flow of blood E. Blood supply of myocardium 1. RCA 2. L Main 3. LAD 4. Circumflex F. Cardiac cycle 1. Systole 2. Diastole G. Cardiac output and cardiac index - SV x HR. CI = CO /body surface area. 1. Preload 2. Afterload H. Cardiac pressures p. 1557 of Black and Hawks 1. R atrium 2. R ventricle 3. Pulmonary artery 4. L atrium 5. L ventricle I. Electrophysiology 1. Properties of heart a. Excitability - ability to respond - Na and K b. Automaticity (rhythmicity) - ability to initiate impulse spontaneously and repetitively without neurohormonal influence (1) SA node 60-100 bpm (2) atria 60-100 (3) AV node 40-60 (4) Ventricles 20-40 c. Contractility - extracellular calcium required! Then triggers more calcium from sarcoplasmic reticulum. Significance: Ca channel blockers alter cardiac rate but not skeletal muscle contraction. d. Refractoriness - inability to respond to new stimulus while still in state of depolarization - can shorten as HR increases
Cardiac - E 2 (1) ventricles - absolute refractoriness - .25 to .3 sec (2) ventricles - relative refractoriness - .05 sec e. Conductivity - move electrical impulses along and across cell membranes of muscle mass but not through fibrous bands. SA node AV node - delay is .07 Bundle of His and bundle branches a. R bundle b. L bundle - 2 fascicles (branches) Purkinje fibers
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Monitor waves - p. 120 in Urden. A. P B. QRS C. T D. PR Interval (PRI) E. ST segment 1. Depressed 2. Elevated Rate A. Using monitor paper B. Six second strip Rhythms - p. 123, Urden, Stacy, and Lough A. Normal sinus rhythm 1. Rate 2. Rhythm 3. P wave 4. PRI 5. QRS complex a. Shape b. Width (duration) 6. Etiology 7. Treatment B. Sinus bradycardia 1. Rate 2. Rhythm 3. P wave 4. PRI 5. QRS complex a. Shape b. Width 6. Etiology
Cardiac - E 3 Treatment - atropine, pacer (see p. 1691 in Black) - look for pacer spike (p 1696), Oxygen Sinus tachycardia 1. Rate 2. Rhythm 3. P wave 4. PRI 5. QRS complex a. Shape b. Width 6. Etiology - FEVER, shock, pain, meds (including dopamine), hormones (epi) 7. Treatment - varies by cause. Channel blockers, beta blockers, oxygen! Sinus dysrhythmia - variance of NSR with respiratory cycle Premature Atrial Contraction (PACs) 1. P wave - shape varies 2. QRS complex - < .12 Paroxysmal supraventricular tachycardia (PSVT) - begins and ends suddenly 1. Rate - 150 - 250 2. Rhythm - regular 3. P waves - rate may be too fast to see P wave 4. PRI - normal 5. QRS - normal 6. Etiology - caffeine, nicotine, digitalis, mitral prolapse, CHF 7. Treatment - Adenocard (adenosine) - antiarrhythmic (slows the conduction in the AV node), vagal maneuver, Ca channel blockers, digitalis, and cardioversion. Atrial flutter - several P waves called flutter waves for each QRS Atrial fibrillation 1. Rate a. Atrial- 350 to 600 fibrillatory waves b. Ventricular - 60 to 100 = controlled; >100 = uncontrolled 2. Rhythm - irregularly irregular ventricular complex 3. P wave - fibrillations 4. PRI - absent 5. QRS - normal 6. Etiology - various sites in atria 7. Treatment a. Convert electrically or chemically (amiodarone, calcium channel blockers, beta blockers, dig) b. Control the rate with medication c. NOTE: mural thrombi 7.
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Cardiac - E 4 I. Premature ventricular contractions (PVCs) 1. Rate - underlying rhythm 2. Rhythm - Early QRS complex 3. P wave - absent or after PVC 4. PRI - absent 5. QRS - > 0.12 - wide with bizarre shape a. Unifocal b. Multifocal 6. Etiology - myocardial ischemia (may be secondary to MI, especially anterior), electrolyte (especially K & Ca) imbalance, hypoxia, acidosis, heart disease, meds. 7. Physiology - ectopic focus, impulse spreads through unusual pathways 8. Treatment - treat...
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