IVMS-CV -Pathophysiology Pharmacology and Treatment of Shock

CV Pharmacology-Pathophysiology and Treatment ofShockPrepared and Presented by: Marc Imhotep Cray, M.D.Professor PharmacologyRecommended Reading:Autonomic pharmacologyFormatives:Practice Question Set #1Clinical:E-Medicine ArticlesShock, CardiogenicShock, HypovolemicShock, Septic9/29/20092Shock (circulatory)See:Shock (circulatory)Effects of inadequate perfusion on cell function. From:http://en.wikipedia.org/wiki/Shock_%28circulatory%299/29/20093Shock, CirculatoryDefinedCirculatory shock, commonly known as just shock, is a serious, life-threatening medical condition where insufficient blood flow reaches the body tissues.As blood carries oxygen and nutrients around the body, reduced flow hinders the delivery of these components to the tissues, and can stop the tissues from functioning properly.The process of blood entering the tissues is called perfusion, so when perfusion is not occurring properly this is called a hypoperfusional (hypo = below) state.See: Shock: An OverviewPDFby 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 9/29/20094The probleminshockAltered circulatory parameters Compromised microcirculationPersistent severe hypoxiaMultiple organ failureFrom: http://www.cvpharmacology.com/clinical topics/hypotension.htm9/29/20095Main typesof 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)Hypothermia9/29/20096ClassificationIn 1972 Hinshaw and Cox suggested the following classification which is still used todayIt uses four types of shock:1.hypovolemic,2.cardiogenic, 3.distributive and 4.obstructive shock 9/29/20097Classification (based on cardiovascularcharacteristics, which was initially proposed in 1972 byHinshaw and Cox)HypovolaemicHemorrhagic, Fluid depletion, Increased vascular capacitanceCardiogenicMyopathic, Mechanical, ArrhythmicDistributiveSeptic, etc.ObstructivePE, pericarditis, pnumothorax etc.9/29/20098Hypovolemic shockHypovolemic 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.9/29/20099Cardiogenic shockCardiogenic 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.9/29/200910Distributive shockDistributive shock –As in hypovolaemic shock there is an insufficient intravascular volume of blood. This form of "relative" hypovolaemia is the result of dilation of blood vessels which diminishes systemic vascular resistance. Examples of this form of shock are:1.Septic shock2.Anaphylactic shock3.Neurogenic shock9/29/200911Obstructive shockObstructive 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.1.Cardiac tamponade2.Tension pneumothorax3.pulmonary embolism4.Aortic stenosis9/29/200912Endocrine shockbased on endocrinedisturbances.Recently a fifth form of shock has been introduced: * Hypothyroidism, in critically ill patients, reduces cardiac output and can lead to hypotension and respiratory insufficiency.* Thyrotoxicosismay induce a reversible cardiomyopathy.* Acute adrenal insufficiencyis 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 insufficiencyin critically ill patients where present hormone levels are insufficient to meet the higher demands9/29/2009 13 Comparison of types of shock (Early stage) Vasoconstrictive Vasodilatative Hypovolamic Cardiogenic 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 stage9/29/200914Decreased cardiac outputDecreased blood pressureDecreased tissue perfusionDecreased coronary perfusionDecreased myocardial functionMicrocirculatoryobstructionCellular aggregationMicrocirculatory demageCell hypoxiaMetabolicacidosisDecreasedmyocardialcontractionInracellularfluidlossDecreased venous returnBP = CO x SVRPathophysiology Concept Map9/29/200915Hypovolemic Shockloss 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.9/29/200916HYPOVOLEMIC (oligemic) SHOCKHemorrhagic-Trauma-Gastrointestinal-Retroperitoneal• Fluid depletion (nonhemorrhagic)External fluid lossDehydrationVomitingDiarrheaPolyuriaInterstitial fluid redistributionThermal injuryTraumaAnaphylaxis• Increased vascular capacitance (venodilatation)-Sepsis-Anaphylaxis-Toxins/Drugs9/29/200917Cardiogenic Shockdependent on poor pump functionacute catastrophic failure of left ventricular pump functionhigh PCWP, low CO and CI, and generally a high SVR9/29/200918CARDIOGENICMyopathic-Myocardial infarction (Left ventricle, Right ventricle)-Myocardial contusion (trauma)-Myocarditis-Cardiomyopathy-Post ischemic myocardial stunning-Septic myocardial depression-Pharmacologic Anthracycline cardiotoxicity Calcium channel blockers9/29/200919Mechanical-Valvular failure Regurgitant Obstructive-Hypertropic cardiomyopathy-Ventricular septal defectArrhythmic-Bradycardia Sinus (e.g.,vagal syncope)Atrioventricular blocks-Tachycardia SupraventricularVentricularCARDIOGENIC(2)9/29/200920DISTRIBUTIVESeptic (bacterial, fungal, viral, rickettsial)Toxic shock syndromeAnaphylactic, anaphylactoidNeurogenic (spinal shock)Endocrinologic Adrenal crisisToxic (e.g., nitroprusside, bretyllium)9/29/200921Extracardiac obstructive shockImpaired 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 pressuresHigh CVP, low PCWP Cardiac output is usually decreased with increased SVR.9/29/200922SymptomsNarrowing of pulse pressureTachycardia, hypotensionRestlessnesDisphoriaDecreased urine outputAnxietyCool, clammy skinObtundationDyspneaUnconsciousness9/29/200923Treatment of shockGeneralities:Positioning, avoiding hypothermiaMaintaining adequate oxygenizationFluid resuscitationPain relief ?(inotropic treatment?)9/29/200924Enhancecompensatory phase of the shockMaintenance of mean circulatory pressureMaximizing cardiac functionRedistributing perfusion to vital organsOptimizing unloading of oxygen at tissues9/29/200925Maintain 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 vasopressin9/29/200926Mintain PressureDecreased venous capacitanceIncreased sympathetic activityIncreased circulating (adrenal) epinephrineIncreased angiotensinIncreased vasopressin9/29/200927Maximize Cardiac PerformanceIncreased contractilitySympathetic stimulationAdrenal stimulation9/29/200928Early mechanical ventilationallows blood flow to beredistributedtends to reverse lactic acidosissupports the patient until other therapeutic measures can be effectiveTidal volumes in the order of 7-10 mlkg-1 of leanbody mass, an O2 concentration that results in arterialsaturation not less than 92%, adequate ventilator rateand sedation to minimize the work of breathing.9/29/200929Fluid resuscitationIVlineLarge bore cannulaMore iv lineChoice of infusionLactated Ringer's solution (initial bolus: 10-25 ml/kg /10 min.) ColloidsDextraneHydroethylstrachGelatineSmall volume resuscitationRate, amountGeneral conditionsparameters ( BP, Pulse, CVP, SatO2etc)9/29/200930Dextrane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kidney9/29/200931Hydroxyethylstrach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 h9/29/200932Inotropic drugsInotropieHeart rateSVRKidneyBlood flowCornarryBlood flowCardiacOutputDoseEpinephrin++++-++10-30mcg/minNorepinephrin++0++--++2-8mcg/minDopamin+++-+++++2-5mcg/min/kgDobutamin+++(+)--++++5-15mcg/min/kgIsoproterenol++++-++++5 mcg/miAmrinon+++0--++++Bolus 0.5 -1.5 mg/kgCont.: 2 to10mcg/kg/min9/29/200933Reference ResourceJoynt, 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, 2006.