Shock 090914002728 Phpapp02

SHOCK James Taclin C. Banez, M.D.

Definition:
Conditions that lowers tissue perfusion
decrease tonicity of blood vessel wall
neurogenic shock
early septic shock
anaphylactic shock
decrease blood volume
hypovolemic shock (hemorrhagic shock)
decrease cardiac output due to myocardial failure.
myocardial ischemia
cardiac compressive shock (pericardial tamponade)

TYPE:
Hypovolemic Shock:
low pre-load
low systemic arterial pressure
tachycardia
increase vascular resistance

Traumatic Shock:
hypovolemia
toxic factors (cytokines) from injured tissues enters to the blood ----> activates intravascular inflammation & intravascular coagulation. (increase vascular permeability ---> multiple organ failure).
Cardiogenic Shock:
heart failure
blood clogged behind the heart
increase filling pressure

Cardiac Compressive Shock:
has a normal heart
low cardiac return due to extrinsic compression
pericardial tamponade
Septic Shock
systemic changes brought by bacterial toxins
Neurogenic Shock
loss of arterial and venous tone
pool of blood in dilated peripheral venous system

Cellular Changes:
decrease tissue perfusion ----> decrease oxygen delivery ----> decrease ATP -----> Na/K membrane pump fails ----> Na & Cl enters the cell ---> isotonic cellular swelling ----> cell death.

Renal Response:
Normal kidneys can tolerate renal ischemia from 15 mins to a maximum of 90 mins. Can be prolonged w/ hypothermia and/or steroid)
Prolonged hypoperfusion leads to functional and anatomic changes presenting as azotemia.
Renal failure index :
( Urine Na x Plasma creatinine )
Urine creatinine
< 1 usually indicates pre-renal oliguria
> 1 indicates acute renal failure

Pulmonary Response:
Damage Alveolar – Capillary interface in case of shock ----> acute diffuse lung injury.
Leakage of proteinaceous fluid into the interstitium and alveolar space.
Leads to ARDS :
Hypoxemia unresponsive to elevation of FiO2
Decreased pulmonary compliance
Needs high airway pressure to attain adequate tidal volume

Pathophysiology
Hypovolemic Shock:
most common
Most of the blood is lost from systemic and small veins (50%) ----> decrease cardiac return ----> low cardiac output ----> decrease blood pressure

Degree of Hemorrhagic Shock
Mild Hemorrhagic Shock:
< 20% blood lost
adrenergic constriction of blood vessels in the skin
thirsty, feels cold
normal BP, PR and urine output

Moderate Hemorrhagic Shock:
20 – 40% blood loss
(+) above signs and symptoms
low urine output
Due to aldosteron and ADH

Severe Hemorrhagic Shock:
40% blood lost
In addition to above s/sx pt has low BP and rapid pulse rate
signs of M.I. ---> Q waves and depressed
St-T segments

Compensatory Mechanism
Adrenergic discharge
Hyperventilation:
with spontaneous deep breathing there is a decreased intra-thoracic ----> increase ventricular end diastolic volume ----> increase cardiac output.
Collapse:
Displaced blood from extremity to the heart and the brain

Release of fluid from the interstitium into the vascular space:
Epinephrine causes constriction of the arterioles and precapillary sphincter ----> decrease intracapillary hydrostatic pressure ----> influx of H2O, Na & Cl

Release of vasoactive hormones:
Resorption of fluid from intracellular to extracellular space:
Epinephrine, cortisol and glucagon increases concentration of interstitial glucose ----> extracellular hyperosmolality ----> draws H2O from cell ----> hydrostatic pressure in the interstitium ----> forced H2O and CHON into the lymphatics -------------> oncotic pressure intravascular ----> attracts H2O intravascularly further

Renal conservation of body H2O and electrolyte
aldosterone
anti-diuretic hormone (vasopressin)

Decompensation in Hypovolemic Shock
Relaxation of arteriolar and precapillary spasm
forced H20 and electrolyte from vascular space into the interstitium
Deterioration of cell membrane function

Two Most Sensitive Signs of Hypovolemia are:
Cutaneous vasoconstriction
Oliguria
Alcohol can cause vasodilation and inhibits secretion of ADH

Monitoring:
Management:
resuscitate patient and control blood lost and correct dehydration
give balance salt solution (crytalloid)
disadvantage of giving colloid resuscitation.
Post-resuscitation HPN
Increase intravascular volume at the expense of necessary interstitial fluid
Depression of albumin synthesis
Depression of circulating immunoglobulin
More expensive and less easier to titrate

Management:
Supine position w/ elevated both lower extremities :  preferred position for patient in shock
Elderly patient ---> check condition of the heart (digitalis) ability to compensate.
Steroid is not indicated
O2 inhalation is of little value if vascular volume is not corrected

Causes of Refractory Shock:
Continuing blood loss from primary injury or another source
Inadequate replacement of fluids
Massive trauma or other derangement
Myocardial infarction
Concomitant septic shock

Traumatic Shock
Traumatized tissue activates coagulation system forming:
Microthrombi:
Occludes pulmonary vasculature ---> increase pulmonary vascular resistance ----> increase right arterial pressure
Humoral products of microthrombi :
cytoxines
Increases vascular permeability ---> loss of plasma

Traumatic Shock
Treatment:
Primary treatment is correct hypovolemia
Debridement of ischemic or dead tissue
If necessary connect to a mechanical ventilatory support

Cardiogenic Shock
s/sx of myocardial ischemia
Increase CVP and pulmonary artery wedge pressure w/ decrease C.O. and fails to respond with fluid solution.
Treatment:
Bed rest, O2 inhalation, narcotic analgesic
Monitoring of cardiac function
Medications: digitalis / dopamine / ganglionic blocking agents / lidocaine
Low cardiac output secondary to low heart rate ---> cardiac pacemaker

Cardiac Compressive Shock
Pericardial tamponade:
there is decrease pericardial compliance on right atrium, right ventricle and left atrium --------> decrease cardiac output associated with high filling pressure and small chamber volumes.

Sign/Symptoms:
Distended neck veins
Muffled heart sound
Hypotension
Tachycardia
Pulsus paradoxicus
Oliguria
Cold clammy skin

Chest X-ray:
Water bottle shape (erect film)
Management:
in unstable pt . – do anterolateral thoracotomy w/ decompression of the tamponade and surgical control of the abnormality
In stable pt. – do pericardiocentesis, withdrawal of 50cc. Blood shd. Return cardiovascular dynamics to normal

Septic Shock
Causes:
Gram positive sepsis (exotoxin)
Gram negative sepsis (endotoxin)
More common
Source of infection:
genito-urinary
respiratory
alimentary
integumentary

Septic Shock
Early septic shock:
warm extremity, pt is still normovolemic
toxin increases core body temperature
BP decreases due to vasodilatation (decrease peripheral resistance)
increase cardiac output due to minimal resistance
increase heart rate and increase cardiac contractility
hyperventilation ----> respiratory alkalosis

Septic Shock
Late septic shock:
cold extremity, patient is hypovolemic
hypovolemia due to --> increase vascular permeability and decrease cardiac output
Increase vascular permeability (endotoxin)
Decrease cardiac output  due to increased pulmonary vascular resistance (endotoxin)
Increase right ventricular pressure --> due to impairment of emptying.
Increase peripheral resistance (cold cyanotic extremities)
Decrease CVP

Septic Shock
Treatment:
volume replacement
look for the source of infection to give the proper antibiotic (culture and sensitivity)
Earliest sign of gm(-) infection:
hyperventilation
respiratory alkalosis
altered sensorium

Neurogenic Shock
Seen in spinal cord injuries and spinal anesthesia.
normovolemic / hypovolemic pt.:
Blood pool in the systemic venules and small veins resulting to decrease right heart filling ----> decrease stroke volume ----> decrease cardiac output ----> (+) angiotensin and ADH

Neurogenic Shock
hypervolemic pt.:
cardiac output increase due to expanded blood volume and decrease vascular resistance.
hypotension due to decrease vascular resistance
Treatment:
Give IVF, if BP does not respond ----> give vasoconstrictor to restore venous tone ----> restore right cardiac filling ----> increase cardiac output.
Elevate the lower extremities

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Shock 090914002728 Phpapp02

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