CV Pharmacology-
Pathophysiology and Treatment of Shock Reading: Autonomic Nervous System Notes Clinical: e-Medicine articles Shock, Cardiogenic Shock, Hypovolemic Shock, Septic
Prepared and presented by: Marc Imhotep Cray, M.D. BMS / CK-CS Teacher http://www.imhotepvirtualmedsch.com/
Shock (circulatory) Effects of inadequate perfusion on cell function
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See: Shock (circulatory. pdf)
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Shock, Circulatory Defined
Circulatory shock, commonly known as just shock, is a serious, life-threatening medical condition where insufficient blood flow reaches body tissues As blood carries oxygen and nutrients around body, reduced flow hinders delivery of these components to tissues, and can stop tissues from functioning properly The process of blood entering tissues is called perfusion, so when perfusion is not occurring properly this is called a hypoperfusional (hypo = below) state Shock: An Overview PDF by Michael L. Cheatham, MD, Ernest F.J. Block, MD, Howard G. Smith, MD, John T. Promes, MD, Surgical Critical Care Service, Department of Surgical Education, Orlando Regional Medical Center Orlando, Florida
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The problem in shock
Altered circulatory parameters
Compromised microcirculation
Persistent severe hypoxia
Multiple organ failure
From: http://www.cvpharmacology.com/clinical topics/hypotension.htm
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Main types of Shock
Vasoconstrictive
Trauma, bleeding, burning, ileus (volumen loss)
Pulmonary embolism (impaired cardiac filling)
Myocardial infarction (impaired cardiac contraction)
Vasodilatative
Anaphylaxis, sepsis (maldistribution of blood flow)
Spinal medullary injury (venous pooling)
Hypothermia 5
Classification ď Ž
ď Ž 1. 2. 3. 4.
In 1972 Hinshaw and Cox suggested the following classification which is still used today It uses four types of shock: hypovolemic, cardiogenic, distributive and obstructive shock 6
Classification
(based on cardiovascular characteristics, which was initially proposed in 1972 by Hinshaw and Cox)
Hypovolaemic
Hemorrhagic, Fluid depletion, Increased vascular capacitance
Cardiogenic
Myopathic, Mechanical, Arrhythmic
Distributive
Septic, etc.
Obstructive
PE, pericarditis, pnumothorax etc.
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Hypovolemic shock Hypovolemic shock – This is the most common type of shock and based on insufficient circulating volume. Its primary cause is loss of fluid from the circulation from either an internal or external source. An internal source may be haemorrhage. External causes may include extensive bleeding, high output fistulae or severe burns. 8
Cardiogenic shock Cardiogenic shock – This type of shock is caused by the failure of the heart to pump effectively. This can be due to damage to the heart muscle, most often from a large myocardial infarction. Other causes of cardiogenic shock include arrhythmias, cardiomyopathy, congestive heart failure (CHF), and cardiac valve problems. 9
Distributive shock
Distributive shock – As in hypovolemic shock there is an insufficient intravascular volume of blood This form of "relative" hypovolemia is the result of dilation of blood vessels which diminishes systemic vascular resistance Examples of this form of shock are: 1. Septic shock 2. Anaphylactic shock 3. Neurogenic shock
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Obstructive shock Obstructive shock – In this situation the flow of blood is obstructed which impedes circulation and can result in circulatory arrest. Several conditions result in this form of shock, including: 1. Cardiac tamponade 2. Tension pneumothorax 3. pulmonary embolism 4. Aortic stenosis 11
Endocrine shock
Recently a fifth form of shock has been introduced: based on endocrine disturbances. Causes:
Hypothyroidism, in critically ill patients, reduces cardiac output and can lead to hypotension and respiratory insufficiency
Thyrotoxicosis may induce a reversible cardiomyopathy
Acute adrenal insufficiency is frequently the result of discontinuing corticosteroid treatment without tapering the dosage However, surgery and intercurrent disease in patients on corticosteroid therapy without adjusting the dosage to accommodate for increased requirements may also result in this condition Relative adrenal insufficiency in critically ill patients where present hormone levels are insufficient to meet the higher demands 12
Comparison of types of shock (Early stage)
Vasoconstrictive Hypovolamic
Cardiogenic
Vasodilatative Circulatory
Septic
Cardiac index
Cardiac index
Peripheral resistance
Peripheral resistance
Blood Volume
Blood Volume
Malperfusion and organ dysfunction are the ultimate end point of any shock stage 13
Pathophysiology Concept Map Decreased venous return
Decreased cardiac output Decreased myocardial function
Decreased myocardial contraction
Decreased coronary perfusion
Decreased blood pressure
Inracellular fluid loss
BP = CO x SVR Metabolic acidosis Cell hypoxia
Decreased tissue perfusion Microcirculatory obstruction
Microcirculatory demage Cellular aggregation
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Hypovolemic Shock loss in circulatory volume
Decreased venous return
Decreased filling of the cardiac chambers
Decreased cardiac output
increase in the systemic vascular resistance (SVR). low central venous pressure (CVP), a low pulmonary capillary wedge pressure (PCWP), low cardiac output (CO) and cardiac index (CI), and high SVR. The arterial blood pressure may be normal or low. 15
HYPOVOLEMIC (oligemic) SHOCK
Hemorrhagic
Interstitial fluid redistribution
- Trauma
Thermal injury
- Gastrointestinal
Trauma
- Retroperitoneal
Anaphylaxis
• Fluid depletion (nonhemorrhagic)
• Increased vascular capacitance (venodilatation)
External fluid loss
- Sepsis
- Anaphylaxis
- Toxins/Drugs
Dehydration Vomiting
Diarrhea
Polyuria
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Cardiogenic Shock ď Ž
ď Ž
dependent on poor pump function
acute catastrophic failure of left ventricular pump function
high PCWP, low CO and CI, and generally a high SVR
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CARDIOGENIC
Myopathic
-Myocardial infarction (Left ventricle, Right ventricle) -Myocardial contusion (trauma) -Myocarditis
-Cardiomyopathy -Post ischemic myocardial stunning -Septic myocardial depression -Pharmacologic Anthracycline cardiotoxicity Calcium channel blockers 18
CARDIOGENIC (2)
Mechanical -Valvular failure Regurgitant Obstructive -Hypertropic cardiomyopathy -Ventricular septal defect Arrhythmic -Bradycardia Sinus (e.g.,vagal syncope)Atrioventricular blocks -Tachycardia SupraventricularVentricular 19
DISTRIBUTIVE
Septic (bacterial, fungal, viral, rickettsial)
Toxic shock syndrome
Anaphylactic, anaphylactoid
Neurogenic (spinal shock)
Endocrinologic
Adrenal crisis
Toxic (e.g., nitroprusside, bretyllium) 20
Extracardiac obstructive shock Impaired diastolic filling (decreased ventricular preload)
a physical impairment to adequate forward circulatory flow involving mechanisms (different than primary myocardial or valvular dysfunction) Frank decrease in filling pressures (as in mediastinal compressions of great veins) or trends towards equalization of pressures in the case of cardiac tamponade or markedly increased right ventricular filling pressures High CVP, low PCWP Cardiac output is usually decreased with increased SVR.
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Symptoms
Narrowing of pulse pressure
Tachycardia, hypotension
Anxiety
Cool, clammy skin
Obtundation
Dyspnea
Unconsciousness
Restlessnes Disphoria
Decreased urine output
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Treatment of shock Generalities: Positioning, avoiding hypothermia Maintaining adequate oxygenization Fluid resuscitation Pain relief ? (inotropic treatment?) 23
Enhance compensatory phase of the shock
Maintenance of mean circulatory pressure
Maximizing cardiac function
Redistributing perfusion to vital organs
Optimizing unloading of oxygen at tissues 24
Maintain Volume
-Fluid redistribution to vascular space
From interstitium (Starling effect) From intracellular space (Osmotic effect)
-Decreased renal fluid losses
Decreased glomerular filtration rate (GFR) Increased aldosterone Increased vasopressin 25
Mintain Pressure
Decreased venous capacitance
Increased sympathetic activity
Increased circulating (adrenal) epinephrine
Increased angiotensin
Increased vasopressin 26
Maximize Cardiac Performance
Increased contractility
Sympathetic stimulation Adrenal stimulation
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Early mechanical ventilation ď Ž
allows blood flow to be redistributed
ď Ž
tends to reverse lactic acidosis
ď Ž
supports the patient until other therapeutic measures can be effective
Tidal volumes in the order of 7-10 mlkg-1 of lean body mass, an O2 concentration that results in arterial saturation not less than 92%, adequate ventilator rate and sedation to minimize the work of breathing. 28
Fluid resuscitation
IV line
Colloids
Large bore cannula
Dextrane
More iv line
Hydroethylstrach
Choice of infusion
Gelatine
Lactated Ringer's solution (initial bolus: 10-25 ml/kg / 10 min.)
Small volume resuscitation
Rate, amount
General conditions parameters ( BP, Pulse, CVP, SatO2 etc)
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Dextrane
Molecular weight: 40K - 60/70K Dalton
Concentration: 10% (40K)*; 6% (60/70K)**
Water binding: 25 ml/g -- 4 - 6 h
Plasma expanding effect: * 180-200; ** 150%
Elimination:
metabolic
kidney 30
Hydroxyethylstrach
Molecular weight: 450K - 200K - 40K Dalton
Substitution: 0,5 - 0,62 - 0,7
Water binding: 15 - 20 ml/g -- 3 - 6 h
6% HES (200K/0,5) -- plasma substitution (100%)
10%HES (200K/0,5) -- plasma expanding (140%)
Elimination:
kidney
12 - 24 h (65 - 70 %) --- 168 h 31
Inotropic drugs Inotropie
Heart rate
SVR
Epinephrin
++
+
+
-
Norepinephrin
++
0
++
Dopamin
++
+
Dobutamin
+++
Isoproterenol
++
Amrinon
+++
Cardiac Output
Dose
+
+
10-30 mcg/min
--
+
+
2-8 mcg/min
-
++
+
++
2-5 mcg/min/kg
(+)
--
+
+
++
5-15 mcg/min/kg
++
-
+
+
++
5 mcg/mi
++
Bolus 0.5 1.5 mg/kg Cont.: 2 to 10 mcg/kg/min
0
--
Kidney Cornarry Blood flow Blood flow
+
+
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Further Study: Joynt, Gavin (April 2003). "Introduction to management of shock for junior ICU trainees and medical students". The Chinese University of Hong Kong. Retrieved on 9 October, 2014.
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