shock kvb. what is shock? shock is the clinical syndrome that results from inadequate tissue...
TRANSCRIPT
What is shock?
Shock is the clinical syndrome that Shock is the clinical syndrome that results from inadequate tissue perfusionresults from inadequate tissue perfusion
Classification of shock
Cardiogenic, due to heart failure
Hypovolemic (oligemic), due to fluid or blood loss
Distributive (hypotensive) owing to peripheral vasodilation
Types of ShockTypes of Shock
• Hypovolemic
• Cardiogenic
• Neurogenic
• Anaphylactic
• Septic
• Hypovolemic
• Cardiogenic
• Neurogenic
• Anaphylactic
• Septic
Types of ShockTypes of Shock
• Hypovolemic
• Cardiogenic
• Neurogenic
• Anaphylactic
• Septic
• Hypovolemic
• Cardiogenic
• Neurogenic
• Anaphylactic
• SepticDistributive shock
Common factor
• Circulatory collapse resulting from a disproportion between circulating blood volume & the vascular space that it has to fill.
• The ensuing tissue hypoxia or anoxia leads to multiple organ failure.
What happens with the perfusion deficit?
1. Insufficient delivery of oxygen & nutrients to cells and tissues.
2. Inadequate clearance of metabolites.
Outcomes of cellular hypoxia
1. Shift from aerobic to anaerobic metabolism.
2. This results in increased lactate production and later on, lactic acidosis.
• The metabolic & hemodynamic derangements are correctible at the outset & are associated with reversible cell injury.
• Persistence or worsening of the shock state leads to irreversible injury and death of cells and possibly , death of the patient.
Cellular Response to ShockCellular Response to Shock
TissueTissueperfusionperfusion
TissueTissueperfusionperfusion
NaNa++ Pump PumpFunctionFunction
NaNa++ Pump PumpFunctionFunction
ATPATPsynthesissynthesis
ATPATPsynthesissynthesis
AnaerobicAnaerobicmetabolismmetabolism
AnaerobicAnaerobicmetabolismmetabolism
Cellular edemaCellular edema Vascular volumeVascular volume
Cellular edemaCellular edema Vascular volumeVascular volume
Impaired cellularImpaired cellularmetabolismmetabolism
Impaired cellularImpaired cellularmetabolismmetabolism
OO22
useuse
OO22
useuse
Intracellular NaIntracellular Na++
& water& water
Intracellular NaIntracellular Na++
& water& water
Impaired Impaired glucose glucose
usageusage
Impaired Impaired glucose glucose
usageusage
Stimulation of Stimulation of clotting cascade & clotting cascade &
inflammatoryinflammatoryresponseresponse
Stimulation of Stimulation of clotting cascade & clotting cascade &
inflammatoryinflammatoryresponseresponse
Hypovolemic ShockHypovolemic Shock
• Decreased intravascular volume
• Causes:– Diarrhoea– Prolonged & excessive vomiting– Massive haemorrhage– Burns
• Decreased intravascular volume
• Causes:– Diarrhoea– Prolonged & excessive vomiting– Massive haemorrhage– Burns
Hypovolemic Shock
• Hemorrhage– external– internal
• GI tract
• hemothorax
• peritoneal or retroperitoneal space
• Loss of fluid into third space– burns– pancreatitis
Causes of cardiogenic shock1. Pump failure:
Ejection fraction < 20% Associated with myocardial
infarction Associated with Conduction
disturbances ( heart block or arrhythmias)
2. Obstructive heart failure Caused by massive pulmonary
emboli or valvular disease (Aortic stenosis)
Cardiogenic Shock
• Myocardial pump failure– myocardial infarction– myocardial rupture– cardiac arrhythmia
• Extrinsic compression– cardiac tamponade
• Outflow obstruction– pulmonary embolus
Cardiogenic ShockCardiogenic Shock
COCO COCOR.A.S.R.A.S.ActivationActivation
R.A.S.R.A.S.ActivationActivation
DyspneaDyspnea DyspneaDyspnea
OO22
supplysupply
OO22
supplysupply
Volume/Volume/PreloadPreload
Volume/Volume/PreloadPreload
SVRSVR SVRSVR
PeripheralPeripheral& pulmonary& pulmonary
edemaedema
PeripheralPeripheral& pulmonary& pulmonary
edemaedemaImpairedImpaired
myocardial functionmyocardial function
ImpairedImpairedmyocardial functionmyocardial function
MyocardialMyocardialOO22 demand demand
MyocardialMyocardialOO22 demand demand
CatecholamineCatecholamineReleaseRelease
CatecholamineCatecholamineReleaseRelease
Neurogenic ShockNeurogenic Shock
Sympathetic ToneSympathetic ToneOrOr
Parasympathetic ToneParasympathetic Tone
Sympathetic ToneSympathetic ToneOrOr
Parasympathetic ToneParasympathetic Tone
Vascular ToneVascular ToneVascular ToneVascular Tone
Massive VasodilationMassive VasodilationMassive VasodilationMassive Vasodilation
SVR & PreloadSVR & Preload SVR & PreloadSVR & Preload Cardiac OutputCardiac Output Cardiac OutputCardiac Output
TissueTissueperfusionperfusion
TissueTissueperfusionperfusion
Anaphylactic Shock
• Massive & systemic allergic reaction
• Large release of histamine
• Increases membrane permeability & vasodilation
Anaphylactic Shock
Caused by a hypersensitivity reaction to an allergen in a previously sensitised patient
Common Features
• Angio-oedema• Bronchoconstriction• Vasodilatation and hypotension• Urticareal rash
Septic Shock
• Leading cause of death in intensive care units
• Most cases (70%) are caused by gram negative bacteria (LPS-lipopolysaccharide)
• Also can occur with gram positive bacteria and fungal organisms
Multiple Organ Dysfunction System
• Progressive dysfunction of two or more organ systems
• Caused by uncontrolled inflammatory response to injury or illness– Typically sepsis
Stages of ShockStages of Shock
• Compensated
• Uncompensated
• Irreversible
• Compensated
• Uncompensated
• Irreversible
STAGES OF SHOCK
• Initial stage (early compensation stage)
• Nonprogressive stage (compensatory)
• Progressive stage (intermediate)
• Refractory stage (irreversible)
Homeostatic Mechanisms in Shock• Baroreceptor reflexes and catecholamine release
– maintain cerebral and cardiac perfusion– decrease perfusion to gut, skin and kidneys
• Activation of renin-angiotensin system– angiotensin II constricts efferent arteriole of
glomerulus to maintain GFR– aldosterone promotes sodium retention
• Release of Arginine Vasopressin (ADH)– promotes renal conservation of water
Renin-Angiotensin-Aldosterone
PlasmaPlasmavolumevolume
PlasmaPlasmavolumevolume
[Na+][Na+] [Na+][Na+]
KidneyKidney(juxtaglomerular(juxtaglomerular
apparatus)apparatus)
KidneyKidney(juxtaglomerular(juxtaglomerular
apparatus)apparatus)Detected by
Releases
ReninReninReninRenin
AngiotensinogenAngiotensin I…Angiotensin I…Angiotensin I…Angiotensin I…
Converts
&/Or
Via ACE(AngiotensinConvertingEnzyme)
Angiotensin II…Angiotensin II…Angiotensin II…Angiotensin II…
Uncompenstated ShockUncompenstated Shock
• Defense mechanisms begin to fail
• Presentation– Hypotension– Marked increase in heart rate– Rapid, thready pulse– Agitation, restlessness, confusion
• Defense mechanisms begin to fail
• Presentation– Hypotension– Marked increase in heart rate– Rapid, thready pulse– Agitation, restlessness, confusion
Irreversible ShockIrreversible Shock
• Complete failure of compensatory mechanisms
• Death even in presence of resuscitation
• Complete failure of compensatory mechanisms
• Death even in presence of resuscitation
Symptoms of Shock
• Anxiety /Nervousness
• Dizziness• Weakness• Nausea &
Vomiting• Thirst• Confusion• Decreased Urine
Output
• History of Trauma / other illness
• Vomiting & Diarrhoea
• Chest Pain• Fevers / Rigors• Shortness of
breath (stridor)
General Symptoms Specific Symptoms
Signs of Shock• Pallor• Cold and clammy extremities• Sweating• Cyanosis• Tachypnoea• Tachycardia• Confusion & agitation• Stridor• Hypotension• Loss of consciousness
Features of compensated shock
• Tachycardia
• Skin pallor due to constriction of arterioles
• Reduced urine production
Features of decompenstaed but still reversible shock
• Hypotension
• Dyspnoea & tachypnoea
• Pulmonary oedema slowly develops, further worsening hypoxia
• Oliguria (urine volume<500ml/24hr)
• Acidosis due to anaerobic glycolysis
Features of irreversible shock
• Marked hypotension with extreme tachycardia (filiform pulse)
• Respiratory distress which is not responsive to oxygen therapy & assisted ventilation
• Loss of consciousness progressing to coma• Gastrointestinal bleeding• Anuria with elevated BUN & creatinine• Severe acidosis• Laboratory & clinical signs of DIC
Clinical Course
• Hypovolemic shock– If patient is young and healthy, most survive if
resuscitation restores perfusion
• Cardiogenic shock and septic shock– Up to 75% mortality even with best care
• Patients succumb with multi-organ failure– Tubular necrosis of kidneys– Ischemic enteropathy – Disseminated intravascular coagulation– Acute respiratory distress syndrome (septic shock)
Morphology of ShockHypoxic injury to multiple organs• Kidneys
– medulla and tubules most affected– acute tubular necrosis
• Gastrointestinal tract– mucosa most sensitive to hypoxia
• Brain• Heart
– subendocardial necrosis of myocardium
• Lungs– resistant to hypoxia but involved with septic shock
Renal Biopsy in DIC
Capillary loops of glomeruli occluded by fibrin thrombi.
H&E stain on left and MSB (Martius scarlet blue) for fibrin on the right
Adult respiratory syndrome (ARDS)
Synonyms:– Shock lung– Diffuse alveolar damage– Acute alveolar injury– Traumatic wet lungs
These are descriptive terms for a syndrome caused by diffuse alveolar capillary damage.
Clinically characterized by:
• Rapid onset of severe life-threatening respiratory insufficiency
• Cyanosis
• Severe arterial hypoxemia that is refractory to oxygen therapy
• Frequently progresses to extrapulmonary multisystem organ failure.
Morphology:
• In the acute edematous stage, the lungs are heavy, firm & boggy due to congestion, edema & inflammation.
This is followed by:
• Proliferation of type II pneumocytes.
• However resolution does not usually occur.
• More commonly, there is organization of the fibrin exudate, with resultant intra-alveolar fibrosis.
• There is marked thickening of the alveolar septae.
Approach to study:1. Definition of shock2. Classification of shock3. Causes of shock4. Pathogenesis of cardiac, neurogenic,
septic & anaphylactic shock5. Stages of shock including
compensatory mechanisms6. Clinical features of shock (at each
stage)7. Morphology of various organs &
tissues in shock