Lecture 8 Shock

From Iusmphysiology

• started here on 01/28/11 at 9AM.

• We won't be tested harder than the objectives.
• Know why the answers to the clinical questions are wrong and right because they may be rewritten.

• recall shock:
  • Brain can go bad from a bump or meds causing sympathetics to go bad
  • Myocardial contractility or valve or rythm can go wrong
  • Toxins or infection can cause anaphylatic shock
  • Blood volume can drop: diarrhea, hemmorage, etc.

Contents 1 Consequences of Loss of Neural Vascular Control 2 Reabsorb water from the interstitial space and take water from cells 3 Flow chart 4 Clinical Example

Consequences of Loss of Neural Vascular Control

• How do you fix shock?
• Hard to fix the brain; sorry.
  • Might give Epi
• Heart attack
  • Usually the remaining part can compensate
• Peripheral resistance
• Endocrine copensation:
  • Hypothal releases antidiuretic hormone
    • Stimulates thirst, helps kidney retain water, vasoconstricts
  • Renin-angiotensin system
    • Angiotensin 2 activates aldosterone at the medulla, and retains K and Na in kdiney
  • Cortisone
    • Cortisol is stimualted to be released from cortex
    • Potentiates norepi
    • Amino acids are released

Reabsorb water from the interstitial space and take water from cells

• Low arterial pressure to reduce capillary pressure
• If arterial resistance elevated, even lower capillary pressure
• Colloidal osmotic pressure of plasma pulls in the interstitial water
• Results of water reabsorption from the tissue
  • There is only so much saline you can give to increase blood pressure before you're diluting the blood too much.

 (a). Gain 500-1000 ml of water for plasma 
 (b).  Dilute the red blood cells, hematocrit falls, viscosity falls 
    (c).  Dilute the plasma proteins with water, colloidal osmotic        pressure falls and the reabsorption of water is limited  

Flow chart

• Most people who go into shock live.
• At some point, not much can save you: the decompensatory phase.
• Blood flow is so low that organs cannot get oxygen so they go into anearobic metabolism.
• Anearobic metabolims will cause leakage, relaxation, and ischemia
• This will make everything worse: decrease in blood volume, decreases vascular resistance, and decreased contractility of the heart.
• Other effects in decompensatory:
  • reabsorption of water from tissue begins to fail
  • water loss to tissue will begin to increase red cell hematocrit
  • venous congestion leads to elevated capillary pressure
  • Vascular smooth muscle overwhelmed by vasodilators in tissue
    • relaxation and decreased resistance
    • diminished response to norepinephrine
  • Kidney failure - the body becomes toxic
    • Kidney doens't have enough pressure to filter correctly.
    • Kidneys need stuff going through tubules for kidney to be healthy
    • If kidney cannot get rid of water and you give saline, then the liquid will just go straight into the tissue
  • Heart problems in deocmpe
    • Stroke volume goes down
    • Contractility goes down
    • We can keep fluids up to keep central venous pressure up (12 mmHg)
      • So shcok pts don't die of low venous pressure
    • Arterial pressure goes down because of contractility issues
    • Tissues that don't have enough oxygen release all cytes of bad things like cytokines and necrosis factors.
    • These interfere with heart regulation and decrease contractility

Clinical Example

• Blood loss
• Heart rate is high
• No chest pain
• EF is 0.4 (should be 0.6 or 0.7, even with low blood volume)
• A. could be
  • This is the answer
• B. not likely (look at the heart rate, the sympathetics are doing what they should)
• C. could happen but EKG says it's something worse, witht he heart
• D. could be happening (in low bp and shock, there is excessive clotting; so the clot could have gotten bigger; probably wouldn't generate EKG problems, though)
• E. this wasn't really mentioned, she might be better with blood, but most pts like this don't get blood

• continued on to Lecture 9 Hypertension and diabetes on 01/28/2011 at 9:20AM.