Physiology Cardiodynamics and Shock Bill Cayley MD MDiv University of Wisconsin

Learning Objectives Participants will be able to – Describe normal cardiac function – Describe and differentiate types of shock – Discuss the significance of cardiac rate and pressure parameters – Discuss appropriate medical and surgical management of the patient in shock

John 50 year old traffic accident victim – Awake, moderate distress, c/o chest pain & SOB – PMH: Hypertension, diabetes. – SH: ½ ppd cigarettes, taxi driver – Exam: HR 120, BP 80/40. PERRLA. Lips cut. Heart irregular. Chest has wet crackles. Abdomen tender.  What is the clinical syndrome?  What could be the underlying diagnoses? Why?  What do you do? Why?

Shock Insufficient circulation of oxygenated blood to meet metabolic demands.

Shock Hypovolemic Obstructive Distributive Cardiogenic

Shock Hypovolemic – Hemorrhage – Aortic dissection – Anemia Obstructive – Aortic valve stenosis Distributive – Sepsis – Thyrotoxicosis – Shunt syndromes Cardiogenic – Decompensated CHF – Acute coronary syndrome – Dysrhythmia Bradycardia Tachycardia Fibrillation – Valvular regurgitation – Myocarditis, – Cardiomyopathy – Tamponade

Normal cardiac function

Stroke volume (SV) – Volume per cycle Cardiac Output (CO) – CO = SV x HR  Typical 70 kg adult 70cc/cycle X 70 cycles/min 4900 cc/minute

Stroke volume determinants Preload – Due to venous return Blood volume Venous tone Afterload – Due to systemic vascular resistance (SVR) Contractility (inotropy)

Stroke volume determinants Frank-Starling Law – Contraction proportional to stretch (to a point…)

Blood pressures CVP – Central venous pressure – Right ventricular preload MAP = (SV x HR) x SVR

Blood pressures PAOP – Pulmonary artery occlusion pressure – RV output – LV preload Left Ventricular End Diastolic Pressure (LVEDP) MAP = (SV x HR) x SVR

Blood pressures MAP – Mean Arterial Pressure – MAP =DBP +(PP/3) – MAP = CO x SVR MAP = (SV x HR) x SVR

? ? ? Preload Afterload Inotropy Shock What types of shock will affect each of the cardiac parameters? MAP = (SV x HR) x SVR

Cardiogenic CHF ACS Dysrhythmia Valve Dz Cardiac tamponade Distributive Sepsis Thyrotoxicosis Shunt syndromes Obstructive Aortic valve stenosis Hypovolemic Hemorrhage Anemia Preload Afterload Inotropy HypovolemicCardiogenicDistributiveObstructive Low CVPHigh CVPLow CVP Low CO HIgh COLow CO High SVR Low SVR+/- SVR Shock MAP = (SV x HR) x SVR

Shock: ACLS approach Quadrad 1: Primary BLS – A, B, C’s – Defibrillation Quadrad 2: Secondary BLS – A, B, C’s – Diagnosis Quadrad 3: – Oxygen, IV, Monitor, Fluids Quadrad 4: – Temperature, HR, BP, Respirations Quadrad 5: – Tank (volume) – Tank (resistance) – Pump (inotropy) – Rate

Acute shock VolumePumpResistanceRate Fluids? Transfusion? Vasopressors? Hypertension Nitrates Hypotension Norepinephrine Dopamine Bradycardia? Tachycardia?

Hypovolemic shock Dehydration Emesis and diarrhea Environmental losses (perspiration) Hemorrhage Traumatic – External, Internal Gastrointestinal – malignancy, ulcer, varices Obstetric or gynecologic – previa, ectopic, cyst Vascular – rupture of AAA Pulmonary – PE, cavitary tuberculosis

Class ParameterIIIIIIIV Blood loss (ml)<750750– –2000>2000 Blood loss (%)<15%15–30%30–40%>40% Pulse rate (beats/min)<100>100>120>140 Blood pressureNormalDecreased Respiratory rate (breaths/min)14–2020–3030–40>35 Urine output (ml/hour)>3020–305–15Negligible Mental statusNormalAnxiousConfusedLethargic Classification of hemorrhage

Hypovolemic shock: physiology Reduced blood volume Reduced preload Reduced stroke volume Reduced cardiac output Response to shock - physiology – Cathecholamines, ADH – Vasoconstriction, tachycardia – Improve venous return and CO MAP = (SV x HR) x SVR

Hypovolemic shock: management Hemostasis – AMPLE H&P Allergies Medications Past illnesses /Pregnancy Last meal Events / Environment – What happened? When? Where? – Treat source of bleeding! Volume restoration – IV crystalloid Saline Ringer’s lactate – Transfusion If no response to 2 Liters of crystalloid If Class III hemorrhage Critically ill pt with Hb < 8 – If no T&C available O pos – males O neg – females MAP = (SV x HR) x SVR

Cardiogenic shock Causes – Acute coronary syndrome – Myocarditis – Acute valve disease – Pulmonary embolism – Pericardial tamponade – Dysrhythmia Bradycardia Tachycardia Killip stages I.No heart failure, no signs of decompensation II.Heart failure, rales, S3 gallop, pulmonary venous hypertension III.Severe heart failure, frank pulmonary edema, rales throughout lung fields IV.Cardiogenic shock, hypotension (SBP <90mmHg), peripheral vasoconstriction with as oliguria, cyanosis and diaphoresis

Cardiogenic shock: physiology Reduced inotropy Reduced stroke volume Reduced cardiac output Left-sided heart failure – Increased PAOP, pulmonary edema Right-sided heart failure – Peripheral edema MAP = (SV x HR) x SVR

Heart failure syndromes “Forward” HF – Weakness, confusion, low BP – Vasodilation, fluid replacement, inotropic support ↓ LV intropy, ↓SV, ↓ CO, ↓PAOP

Heart failure syndromes “Left-backward” HF – DOE, pulmonary edema, BP normal or high – Vasodilation, diuretics, bronchodilators (?), respiratory support (?) ↓ LV intropy, ↓SV, ↓ CO, ↑PAOP

Heart failure syndromes “Right backward” HF – Peripheral edema, dyspnea, and ascites – Diuretics for fluid overload – Fluids for RV infarction ↓ RV intropy, +/- PAOP

PA catheterization? PAC not needed to dx heart failure or shock – PAC may help differentiate cardiogenic vs non-cardiogenic shock PCOP gives inaccurate estimation of LVEDP if: – Valvular disease such as MS or AR – Ventricular shunting – Stiff left ventricle PAC only recommended in unstable patients not responding to standard interventions

Oxygen, IV, Monitor Pulmonary Edema?Volume Problem?Pump Problem?Rate Problem? Dopamine Tachycardia? Bradycardia? Actions Oxygen (& intubation?) Nitroglycerin SL Furosemide Morphine Administer Fluids Transfuions? Cause-specific interventions Vasopressors (?) Blood pressure? Norepinephrine SBP > 100SBP , no shockSBP , shockSBP < 70, shock Nitroglycerin OR Nitroprusside Dobutamine Adapted from: ALCS Resource Text. Dallas, TX: American Heart Association, Acute shock, hypotension, pulmonary edema

Distributive shock High-output heart failure – ↑ CO unable to match systemic demand Thyrotoxicosis Anemia Hypotensive heart failure – ↓MAP & peripheral perfusion Shunt syndromes Septic shock – May also have ↓ venous return and ↓ preload MAP = (SV x HR) x SVR

Obstructive Shock Resistance to cardiac outflow – ↑ afterload, but ↓ SVR and MAP MAP = (SV x HR) x SVR

Obstructive Shock Aortic stenosis – Angina, DOE, exertional syncope – SEM initially, softens w/ progressive stenosis – Diagnosis suspected on exam, ECG, CXR – Echo vital for definitive diagnosis Management – Avoid reductions in MAP (avoid hypotension) – Correction requires surgery MAP = (SV x HR) x SVR

Preload Afterload Inotropy In conclusion… Systematic approach (ABC’s, 5 quadrads) 4 classes – Hypovolemic – Cardiogenic – Obstructive – Distributive MAP = (SV x HR) x SVR Continual assessment of ABCs

Resources Executive summary of the guidelines on the diagnosis and treatment of acute heart failure. Eur Heart J Feb;26(4):384. ( Rogers J. Cardiovascular Physiology. Updates in Anaesthesia (Issue 10): 1-4. ( (accessed 8 December 2008) ALCS Resource Text. Dallas, TX: American Heart Association, Gutierrez G, Reines HD, Wulf-Gutierrez ME. Clinical review: hemorrhagic shock. Crit Care Oct;8(5): Epub 2004 Apr 2. PMID: Committee on Trauma. Advanced Trauma Life Support Manual. Chicago. American College of Surgeons, 1997: 103 – 112. ACC/AHA 2006 guidelines for the management of patients with valvular heart disease. J Am Coll Cardiol Aug 1;48(3):e (

THANKS!