Shock hypovolemic

Hypovolemic Shock

ShockVascular compartments:

TBW (60% of IBW) Total Body Water

ICW (40%) ECW (20%) Intracellular Water Extracellular Water

Interstitium Plasma(1/3) (2/3)

ShockLoss of circulating blood volume

Normal Blood Volume:- 7% IBW in adults

- 9% IBW in kids

Understanding Shock

• Inadequate systemic oxygen delivery activates autonomic responses to maintain systemic oxygen delivery• Sympathetic nervous system

• NE, epinephrine, dopamine, and cortisol release• Causes vasoconstriction, increase in HR, and increase of cardiac

contractility (cardiac output)

• Renin-angiotensin axis• Water and sodium conservation and vasoconstriction• Increase in blood volume and blood pressure

Understanding Shock

• Cellular responses to decreased systemic oxygen delivery• ATP depletion → ion pump dysfunction• Cellular edema• Hydrolysis of cellular membranes and cellular death

• Goal is to maintain cerebral and cardiac perfusion• Vasoconstriction of splanchnic, musculoskeletal, and

renal blood flow• Leads to systemic metabolic lactic acidosis that

overcomes the body’s compensatory mechanisms

Global Tissue Hypoxia

• Endothelial inflammation and disruption• Inability of O2 delivery to meet demand• Result:

• Lactic acidosis• Cardiovascular insufficiency• Increased metabolic demands

Multiorgan DysfunctionSyndrome (MODS)

• Progression of physiologic effects as shock ensues• Cardiac depression• Respiratory distress• Renal failure• DIC

• Result is end organ failure

ShockHypovolemic

Septic

Cardiogenic (Obstructive)

Neurogenic

Adrenal

Hypovolemic ShockDefinition:Reduction in intravascular volume leading to

insufficient oxygen delivery to cells (mitochondria)

Site of fluid loss Mechanism of lossSkin Thermal or chemical burn,

sweating from excessive heat exposure

GI tract Vomiting or diarrhea

Kidneys Diabetes mellitus or insipidus, adrenal insufficiency, “salt-losing” nephritis, polyuric phase after acute tubular damage, and use of potent diuretics

Intravascular fluid lost to the extravascular space

Increased capillary permeability secondary to inflammation or traumatic injury (e.g. crush), anoxia, cardiac arrest, sepsis, bowel ischemia, and acute pancreatitis

Hypovolemic ShockReduced intravascular volume?

No oxygen delivery!

No aerobic metabolism!

Then… Metabolic acidosis (lactic acid production) Endoplasmic recticulum swelling Mitochondrial damage Cell Death!

EFFECTIVE RESUSCITATION

IRREVERSIBLE

Assessment of Stages of Shock% Blood Volume loss

< 15% 15 – 30% 30 – 40% >40%

HR <100 >100 >120 >140

SBP N N, DBP, postural drop

Pulse Pressure

N or

Cap Refill < 3 sec > 3 sec >3 sec or absent

absent

Resp 14 - 20 20 - 30 30 - 40 >35CNS anxious v. anxious confused lethargicTreatment 1 – 2 L

crystalloid, + maintenance

2 L crystalloid, re-evaluate

2 L crystalloid, re-evaluate, replace blood loss 1:3 crystalloid, 1:1 colloid or blood products. Urine output >0.5 mL/kg/hr

Hypovolemic ShockHemorrhagic shock (3 categories)

1. Compensated:– 0-20% of blood loss

– Blood pressure is maintained via increased vascular tone and increased blood flow to vital organs

Hypovolemic ShockThe body’s response:

Compensated shock Baroreceptor mediated vasoconstriction!

Increased epinephrine, vasopressin, angiotensinResults in:– Tachycardia– Tachypnea– Lowered pulse pressure– Slightly lowered urine output

Hypovolemic ShockThe Organs who win:BrainHeartKidneysLiver

The Organs who lose:SkinGI tractSkeletal Muscle

Hypovolemic Shock The body will make whatever adjustsments it can to

maintain…. Adequate

Cardiac Output

Brain and heart perfusions remain near normal while other less critical organ systems are, in proportion to the blood volume deficit, stressed by ischemia.

Hypovolemic Shock2. Uncompensated:

20-40% loss of blood volume

Decrease in BP

Tachycardia

Hypovolemic ShockThe body’s response:

Uncompensated shockThe intravascular volume deficit exceeds the capacity

of vasoconstrictive mechanisms to maintain systemic perfusion pressure.

Increased cardiac outputIncreased respirationSodium retention

Hypovolemic Shock3. Lethal exsanguination:

40% loss of blood volume

Profound hypotension and inability to perfuse vital organs

Hypovolemic ShockManagement:

ABCs of trauma (AIRWAY is always first!) Control hemorrhage (splint the limb!!) Obtain IV access and resuscitate with fluids and blood

– 2 liters crystalloid for adults– 20 cc/kg crystalloid x 2 for kids

• Normal saline• Ringers Lactate solution• Plasmalyte

– Require 3:1 replacement of volume loss

Long term critical care management

Hypovolemic Shock

Your management goals AFTER securing the ABCs:

• STOP THE BLEEDING!

• RESTORE VOLUME!

• CORRECT ANY ELECTROLYTE/ACID-BASE DISTURBANCES!

Hypovolemic ShockVolume Resuscitation ~ What are my goals?

1. Rapid Responder– Give 500cc-1 Liter crystalloid rapid improvement

of BP/HR/Urine output– < 20% blood loss– Surgery consult

Hypovolemic ShockVolume Resuscitation ~ What are my goals?

2.Transient Responder– Give 500cc-1 Liter crystalloid improves briefly

then deteriorates– 20-40% blood loss– Continue crystalloid infusion +/- Blood– Surgery consult

Hypovolemic ShockVolume Resuscitation ~ What are my goals?

3. Non Responder– Give 2 Liters crystalloid/ 2 units Blood no

response– > 40% blood loss– STAT Surgery consult!

Hypovolemic ShockIs my volume resuscitation

adequate/inadequate?

Urine output Vital signsSkin perfusionPulse Oximetry

References

• Clinical Anesthesia 4th Ed. Morgan et al. Lange Medical / McGraw Hill, 2006, P.242-250

• SAFE Investigators. NEJM 2004; 350: 2247 – 56