Cardiology - Cardiogenic Shock, Cardiac Surgery

cardiogenic shock - happens generally because of what? resulting in what?

• happens generally due to an extreme drop in stroke volume secondary to systolic dysfunction

• RESULTS IN:

  • elevated LV preload (PAOP or wedge pressure) with associated pulmonary symptoms

  • elevated LV afterload (SVR) due to vasoconstrictive compensatory mechanisms

  • a resultant drop in cardiac output (CO) to the point where perfusion to organs is no longer adequate

cardiogenic shock - COMPENSATORY STAGE (clinical presentation)

• tachycardia

• tachypnea

• crackles/mild hypoxemia

• ABG with respiratory alkalosis or early metabolic acidosis

• anxiety/irritability

• neck vein distention

• S3 heart sounds (S4 if there is also an acute MI)

• cool skin

• LOW urine output

• NARROW pulse pressure

• BP is maintained or lower than baseline

cardiogenic shock - why is pulse pressure NARROW in the COMPENSATORY stage?

• both LV contractility and stroke volume (the amount of blood ejected with each beat) is SIGNIFICANTLY low (BLOOD ISN’T GOING FORWARD), while the body is releasing catecholamines to cause systemic vasoconstriction (preserving the diastolic pressure)

  • THIS LEADS to a lower SYSTOLIC BP and a maintained/increased diastolic pressure

cardiogenic shock - PROGRESSIVE STAGE (clinical presentation)

• hypotension

• worsening tachycardia, tachypnea, oliguria

• metabolic acidosis

• worsening crackles/hypoxemia

• clammy/mottled skin

• worsening anxiety/lethargy

cardiogenic shock - ETIOLOGIES

• Acute MI

• chronic HF

• cardiomyopathy

• dysrhythmias

• cardiac tamponade

• papillary muscle rupture (obliterates the mitral valve; LIFE THREATENING!! NEEDS SURGERY IMMEDIATELY)

cardiogenic shock - TREATMENTS

• IDENTIFY THE CAUSE

• manage arrhythmias (brady/tachy) that may be contributing to a decrease in cardiac output

• reperfusion if there is STEMI (percutaneous coronary intervention (PCI) or fibrinololytic therapy)

• emergent surgery if due to a mechanical problem (ruptured papillary muscle, VSD)

• mechanical support (IABP, IMPELLA, VAD)

cardiogenic shock - interventions that ENHANCE EFFECTIVENESS OF PUMP

• positive inotropic support (norepinephrine, dopamine, DOBUTAMINE, MILRINONE)

• AVOID negative inotropic agents (such as beta blockers, calcium channel blockers)

• Vasodilators (USED IN CONJUNCTION with IABP therapy and positive inotropes if the patient is in the PROGRESSIVE stage with hypotension)

cardiogenic shock - interventions that DECREASE THE DEMAND ON PUMP

• preload/afterload reduction (nitroprusside, nitroglycerin)

• optimize oxygenation

• mechanical ventilation

• treat pain

• IABP for short term support

• ventricular assist device (VAD) may be used for longer periods of time than IABP

cardiogenic shock - MECHANICAL CIRCULATORY SUPPORT (IABP - used in management of what?)

• LV heart failure

• cardiogenic shock

• cardiomyopathies

• CORONARY PERFUSION

• patients waiting for transplant

IABP therapy - inflation vs. deflation

• INFLATION - happens at beginning of diastole (dicrotic notch of arterial waveform), INCREASES CORONARY ARTERY PERFUSION

• DEFLATION - happens right before systole begins; determined by a set trigger for deflation; DECREASES AFTERLOAD

cardiac surgery - what is cardiopulmonary bypass?

• aortic cross-clamping, stopping heart during surgery; blood is diverted to external machine for oxygenation/circulation

• cannulation sites - aorta, right atrium

• THE LONGER THE BYPASS TIME, THE MORE BLEEDING THERE IS AND THE MROE COMPLICATIONS THERE MAY BE POSTOPERATIVELY

Post-Op Assessment for Complications related to CABG

• hemodynamic abnormalities (HR/BP CHANGES)

• arrhythmias

• TAMPONADE

• PERICARDITIS

• electrolyte abnormalities

• hematologic abnormalities/bleeding

• pulmonary problems (pneumonia, atelectasis, difficulty weaning from mechanical ventilation)

• pain/anxiety

• renal failure

• endocrine problems (issues with glycemic control)

• gastrointestinal problems (N/V, ileus)

• infections

Post-Op CHEST TUBE MANAGEMENT

• MAINTAIN PATENCY

  • no dependent loops; milking/stripping chest tubes is NOT routine indicated (IF CLOTS APPEAR → GENTLY MILK CHEST TUBE)

• mediastinal chest tubes remove serosanguinous fluid from the operative site, whereas pleural chest tubes remove air, blood, or serous fluid from the pleural space

• keep chest tubes LOWER than patient’s chest

• do NOT clamp the system unless you are changing the drainage system or there is a system disconnect; when the tube is clamped, the connection to the negative chamber is LOST

• chest tube output >100 mL for 2 consecutive hours generally requires intervention → MAINTAIN HEMODYNAMIC STABILITY, CORRECT VOLUME STATUS, ADMINISTER BLOOD PRODUCTS

Valve Surgery - Mechanical valve (Advantages/Disadvantages)

• advantages

  • relatively easy to insert

  • very reliable

  • lasts longer than biological valve

• disadvantages

  • high risk of thrombosis

  • PERMANENT anticoagulation therapy

Valve Surgery - Biological Valve (advantages/disadvantages)

• advantages

  • only short-term anticoagulation is required, but the patient will need LONG-TERM ANTIPLATELET (ASA) THERAPY

• disadvantages

  • wears down, especially in high-pressure systems

Post-valve repair / replacement NURSING CONSIDERATIONS

• AVOID A DROP IN PRELOAD (most patients who have had valve stenosis/chronic regurgitation have had ELEVATED end-diastolic volumes; sudden preload normalization (drop) may result in HYPOTENSION)

• anticoagulation will be needed for mechanical valve replacement; biological valve replacement will require antiplatelet therapy (ASA)

• anticipate conduction disturbances since the mitral, tricuspid, and aortic valves are anatomically close to conduction pathways; temporary or permanent pacing may be needed

Transcatheter Aortic Valve Replacement (TAVR) - what is it?

• a procedure that involves placement of a collapsible prosthetic valve (either bovine or porcine) over the diseased valve (either a native valve or a previously placed artificial valve)

• access to the aorta is usually achieved percutaneously or through a small incision, avoiding cross-clamping of the aorta and cardiopulmonary bypass

• most are done via femoral artery and performed in a cardiac cath lab

Transcatheter Aortic Valve Replacement (TAVR) - CANDIDATE?

• severe aortic valve disease that is classified as HIGH RISK for open surgery

• intermediate risk for open surgery may qualify for TAVR OR open surgical replacement (HEART VALVE TEAM DISCUSSION NEEDED)

• patients considered extreme high-risk/inoperable or LOW risk for open surgery are NOT CANDIDATES FOR TAVR

Transcatheter Aortic Valve Replacement (TAVR) - Complications? what is required after the procedure?

• Complications

  • vascular complications (associated with femoral access), such as hematomas, RP bleeding, and arterial occlusion

  • heart block

  • stroke

  • AKI

  • paravalvular regurgitation (associated with mismatch of prosthetic valve and native valve annulus)

• DUAL ANTIPLATELET THERAPY (DAPT) → ASA (75-100 mg/day) for life and clopidogrel (75 mg/day) for 3-6 months