Main»Low Cardiac Output And Circulatory Support

Low Cardiac Output And Circulatory Support

Low Cardiac Output & Circulatory Support

CARDIOGENIC SHOCK

1. Definition

A. Definition
1) BP systolic < 80 mmHg (or 30 mmHg below basal, BP mean <60 mmHg)
2) CI < 2 L/min/M2 (with adequate filling)
3) LAP and/or RAP > 20 mmHg
B. Clinical Manifestations of Low C.O.
1) Decreased peripheral perfusion (pulses, cool, mottled)
2) Restlessness, confusion decreased mentation
3) UO < 20-30 ml/hr (adults)
C. Causes
1) MI, myocarditis, tamponade, arrhythmias, acute MR/AI
2) Massive pulmonary embolism, vena caval obstruction, tension pneumothorax
3) R/O hypovolemia, acidosis, anemia, sepsis

PRIMARY DETERMINANTS OF CARDIOVASCULAR PERFORMANCE

A. Heart Rate & Rhythm
1) Sinus Rhythym vs Atrial Fibrillation,AVB; bradycardia; tachycardia
B. Preload (Ventricular filling)
1) Frank-Starling effect
C. Ventricular Compliance (Distensibility)
1) Effect of ischemia, injury, pericardial space
2) (Tamponade - decreased CO, BP, Pule Pressure, increased LAP=RAP)
D. Ventricular Contractility
E. Inotropes
1) Sympathomimetic amines, phosphodiesterase inhibitors
F. Afterload (Vascular resistance)
1) Vasoactive therapy

SECONDARY DETERMINANTS OF CARDIOVASCULAR PERFORMANCE

A. Oxygen delivery
1) O2 carrying capacity (Hgb)
2) Oxygenation
B. Metabolic - acid/base status
1) Acidosis (effect on contractility)
2) Alkalosis (decreases release of O2 from Hgb, Left shift oxygen-Hgb dissociation curve)
C. Metabolic stress/load
1) Fever, agitation, respiratory distress

APPROACH TO CARDIOGENIC SHOCK

A. Medical Management of Reversible Causes
B. Primary Determinants of CV Performance
1) Rate & Rhythm, Preload, Compliance, Contractility, Afterload
C. Secondary Determinants of CV Performance
1) Oxygen delivery, Acid/base status, Metabolic load
D. Assisted Circulation
1) Intra-Aortic Balloon Pump (IABP)
2) Cardiopulmonary Support (CPS)
3) Ventricular Assist Device(s) (VAD's)
4) Total Artificial Heart (TAH's)

INTRA-AORTIC BALLOON PUMP

1.Indications for Use

A. Failure to wean from CPB (49%)
B. Post-MI cardiogenic shock (22%)
C. Refractory myocardial ischemia (15%)
D. Post-op cardiogenic shock (7%)
E. MR or VSD (temporizing)
F. Ischemic arrhythmias
G. (Bridge to transplant)

2. Contraindications for Use

A. Aortic valve insufficiency
B. Severe peripheral vascular disease (?)

3. Complications

A. Limb ischemia (5-18%)
B. Insertion site hemorrhage (2-4%)
C. Infection (1-2%)
D. Aortic or iliac perforation (1-2%)
E. Aortic dissection (1%)
F. Renal artery embolism or thrombosis (1%)
G. Mesenteric infarction (1%)
H. Spinal cord injury (0.5-1%)
I. Gas embolization/rupture (0.5%)
J. CVA (0.5%)

4. Results

A. Post-cardiotomy Failure
1) 75-85% weaned
2) 55% survival
B. Post-MI Cardiogenic Shock
1) 75% will improve hemodynamically
2) In post MI use, mortality is 85%
3) Post-MI + intervention - mortality = 40-50%

ADVANCED MECHANICAL SUPPORT

1. Indications

A. Post-cardiotomy cardiogenic shock
B. Post-MI cardiogenic shock
C. Post-transplant graft failure
D. High-risk PTCA support
E. Cardiopulmonary Resuscitation (CPR)
F. Hypothermia rewarming
G. Bridge-to-transplant (or recovery)
H. Alternative to transplantation (future)

POST-CARDIOTOMY MECHANICAL CIRCULATORY SUPPORT

1. Intraoperative Management

A. Pharmacologic support
B. Intra-aortic balloon pump
C. Optimization (volume, metabolic, respiratory, drugs)
D. Decision for VAD
1) Patient selection
2) Early intervention

2. Patient Selection

A. Inclusion Criteria
1) Cardiogenic shock: CI <2 l/min/M2, BP systolic <80 mmHg
2) LAP >20 and/or RAP >20 mmHg
3) (after medical optimization - pre/afterload, respiratory, metabolic)
4) (after pharmacologic support)
B. Exclusion Considerations
1) Technically imperfect operation
2) Perioperative MI (vs. stunned myocardium)
3) Age
4) Preoperative "emergency" status
5) Massive bleeding
6) Long CPB
7) End-organ failure (renal, hepatic, pulmonary .. )
8) Infection (i.e. endocarditis)

3. Intraoperative Management - Implementation of support

A. Select VAD, cannulae
B. Cannulate, implement VAD support
C. Re-assess cardiac performance
D. Secure hemostasis
E. Wound handling (close vs. open)

4. Equipment

A. Ventricular Assist Devices
1) (Considerations: cost, availability, familiarity, anticoagulation, blood trauma, monitoring)
2) Pulsatile, pneumatic
3) Centrifugal pumps
4) [ Roller pumps ]
B. Cannulae
1) Uptake: R. side: 34-51 Fr; L.side: 28-36 Fr
2) Return: Ao and PA: 22 Fr

5. Management of VAD Support

A. Observe for bi-ventricular failure
B. Institute second VAD as needed
C. Secure Hemostasis
1) Reverse Heparin
2) Fibrin Glue
D. Wound Handling
1) Close sternum/skin
2) Close skin only, support sternum
3) Leave open (silastic or Esmark ...)

6. Postoperative - General

A. Maximize Myocardial Recovery
1) Reduce Inotrope support
2) Keep heart decompressed
B. Anticoagulation
1) Intraop - heparin is reversed
2) When CT output OK - ACT > 180
3) When weaning VAD - ACT > 220
C. Maintain Pulsatile Perfusion (?)
1) Leave IABP in place

7. Postoperative - Weaning

A. Time Course
1) At least 24 hours
2) But <10% survivorship after 7 days
B. Follow Recovery
1) Reduce VAD flow (i.e. to 1L/min)
2) Observe LAP,RAP,AoP,PAP,SVO2
3) Observe cardiac function w/ TEE
C. Remove VAD
1) With good hemodynamics at low VAD flow
D. Wean IABP & drips as able

8. Problems

A. Cardiovascular
1) RV failure with LVAD
a) decreased LAP, decreased VAD out, increased RAP
2) LV failure with RVAD
a) decreased RAP, decreased VAD out, increased LAP
3) Hypovolemia (decreased LAP/RAP decreased VAD out)
4) Cyanosis - shunting through PFO
B. Device-Related
1) Thromboemboli
2) Cannula obstruction
a) increased LAP/RAP, decreased VAD out
3) Device failure
4) Hemolysis
C. Systemic
1) Bleeding (30-45% return to OR)
2) End-organ failure (renal, respiratory, hepatic)
3) Infection

9. Results

A. Weaned - 50-60%
B. Survived - 25-50%