Lecture 1: Hypovolemic Shock Flashcards
Define cardiovascular shock
Cardiovascular shock is a state of cellular and tissue hypoxia due to:
- Reduced oxygen delivery
- Increased O2 consumption
- Inadequate oxygen utilization
(can be due to one of these three or a combo of them)
What is the equation for MAP or “mean arterial pressure”
MAP = CO x TPR
cardiac output x total peripheral resistance
It is essentially the input to the arterial tree times the resistance to that flow
Define Cardiac Output
What are the determinants of CO?
CO = HR x SV
(cardiac output = heart rate x stroke volume)
Determinants for HR: autonomic nervous system and conduction system
Stroke Volume Determinants: Preload (Frank-Starling mechanism), Contractility, and Afterload (arterial pressure)
What are the determinants of TPR?
1.
2.
3.
TPR determinants:
- vessel diameter (controlled by sympathetic activity)
- Length of blood vessel (doesn’t vary)
- Blood Viscosity (hematocrit, RBC aggregation, RBC deformity, plasma viscosity)
Changes in blood pressures are helpful in determining what kind of shock the pt is in..
What kind of shock is indicated by a decrease in systolic blood pressure?
Decrease in systolic blood pressure: Cardiogenic shock
Decrease in diastolic blood pressure: lack of vessel tension (which causes a drop in systolic too)
What are the mechanisms that maintain oxygen consumption?
Main determinants of myocardial O2 consumption:
- Heart Rate
- Rate of tension development (contractility)
- Factors that enhance tension development
What are the mechanisms that maintain oxygen delivery?
Oxygen delivery is dependent on maintanence of mean arterial pressure: MAP = CO x TPR
Cardiac Output determinants:
CO = HR x SV
Heart rate determinants: autunomic NS, conduction system
Stroke Volume Determinants: Preload, Contractility (sympathetic activity), afterload (arterial pressure)
TPR Determinants:
- vessel diameter (sympathetic activity)
- legnth of blood vessel (doesn’t vary)
- RBC aggregation, RBC deformity
- Plasma viscosity (hydration, protein types and concentration)
What are the mechanisms that maintian oxygen utilization?
Utilization of oxygen:
Mitochondrial-dependent generation of ATP
Glycolysis—->—–>—-> Electron Transport Chain
If some pathology happens where your ETC gets poisoned (such as in cyanide) than you cannot utilize the ATP
Sodium nitroprusside is a very common drug given in the ER to treat hypertensive crisis…
If used for too long at high doses, what can it cause?
What kind of shock would that lead to?
Sodium nitroprusside at high levels for a long time can end up mirroring cyanide posioning
The problem with cyanide poisioning, is that it poisions your Electron Transport Chain and your body’s ability to utilize ATP
Unable to utilize ATP: Reduced O2 utilization
List the major symptoms of cardiovascular shock for the stage of PRE-SHOCK
Preshock - Compensated Shock:
- Normal systolic arterial pressure (SAP)
- Compensatory tachycardia
- Peripheral vasoconstriction (hard to tell symptom wise other than pale clammy skin as an indicator)
List the major symptoms of cardiovascular shock for normal shock (symptoms of organ dysfunction)
Shock - symptoms of organ dysfunction:
- hypotention (SAP < 90 or MAP < 70)
- tachycardia
- cool clammy skin, maybe cyanosis
- Oliguria (lack of urine formation, hard to tell without a catheter)
- Metabolic acidosis (hyperlactatemia… indication of anaerobic metabolism trying to compensate, change in blood pH)
- Dyspnea
- Reslestless
- diaphoresis (a sign of the SNS activating for compensatory mechanisms to increase blood flow)
List the stages of shock for end stage of shock or “end organ dysfunction”:
End organ dysfunction:
- acute renal failure
- acidemia (ABG pH < 7.35)
- depressed CO
- resistant hypotension
- obtundation (altered mental status)
- coma
What are the four major forms of cardiovascular shock?
Four Major Forms of Cardiovascular Shock
1. Distributive : inappropriate distrubution of blood
- Hypovolemic: reduced plasma or blood volume
- Cardiogenic: weak pump, the heart is the root of the issue (example being an MI)
- Obstructive: obstruction of cardiac filling or blood flow (issue is due to something outside of the heart)
Assign the various examples with the type of cardiovascular shock they fall under:
Myocardial Infarction (heart attack)
Cardiac Tamponade
MI/ heart attack: cardiogenic shock
Cardiac Tamponade: obstructive shock (pericardial sack is pushing down on the heart, causing issues with its ability to pump blood, aka root issue is outside of the heart itself, making it obstructive)
List the three forms of distributive shock
Three types of distributive shock:
- Septic shock
- Neurogenic shock
- Anaphylactic shock
Explain septic shock:
What is it?
What are some common Vitals that can indicade septic shock?
Septic shock: severe sepsis plus persistently low blood pressure, most common form of shock in ICU caused by infection
Bacteria in circulation… produces NO and other vasodialators… ends up in a decrease in diastolic pressure
Symptoms: high body temp/ fever
Explain neurogenic shock
What is it?
Neurogenic shock is low tissue perfusion due to a distruption of autonomic pathways in the spinal cord
Our body has tonic sympathetic activity to maintain blood pressure normally, if you have some sort of injury to your spinal cord (around T6) that messes with the body’s ability to maintain tissue perfusion… neurogenic shock
The ANS would no longer be able to control the diameter of your blood vessels and your blood pressure would decrease (both systolic and diastolic)
Explain anaphylactic shock
Anaphhylactic shock: Severe “anaphylaxis” or allergic reaction
- MAST cells release histamine, MAJOR vasodilator
Also, you’ll see signs of a rash, swelling of the face, hives
What do physician’s look at to assess shock?
Physicians look at the following to assess shock:
- Hypotension?
- Mental status
- Skin perfusion
- Kidneys (measure urine output)
- heart rate
- look at blood lactate levels
How can you distinguish distributive shock vs all the other types (cardiogenic, hypovolemic, obstructive)?
Distributive shock will have normal O2 levels
(normal SpO2 and normal mixed venous O2)
List the three mechanisms of cardiogenic shock
Cardiogenic shock: inadequate blood flow due to dysfunction in the ventricles of the heart (or somewhere in the heart), resulting in low blood pressure and hypoperfusion
Three mechanisms of cardiogenic shock:
- Cardiomyopathic
- Arrhythmic
- Mechanical
Remember, sign of cardiogenic is decrease in systolic
Explain cardiomyopathic sources of cardiogenic shock
Cardiomyopathic sources of cardiogenic shock:
- Dilated cardiomyopathy (dilated ventricle will need more O2 than it is receiving)
- Hypertrophic cardimyopathy
- Restrictive cardiomyopathy
- Arrhythmogenic right ventricular dysplagia
(which is genetic disease causing fat to build up in the falls of the ventricles, causing arrhythmias)
Explain how arrhythmia’s can lead to cardiogenic shock
Arrthymia’s that can contribute to cardiogenic shock:
- VTach
- VFib
- Bradyarrthymia’s
all of these cause a decrease in CO because the heart is not contracting as it should
Explain mechanical sources of cardiogenic shock
Mechanical sources of cardiogenic shock- due to anatomical abnormalities that reduce cardiac output
Examples:
- Severe aortic valve insufficiency (leaky aortic valve would cause a decrease in CO)
- Severe mitral valve insufficiency (where the LV ventricle contracting would cause blood to back up into the LA)
- Dissecting aneursym, septal defect, ventricular aneursym, atrial myxoma
Explain what an atrial myxoma is… what kind of shock does it create?
Atrial myxoma is a type of benign tumor that ends up growing and taking up so much space in the LA that it actually decreases cardiac output
It is a type of mechanical source for cardiogenic shock
Describe the key difference between mechanical shock and obstructive shock
Obstructive shock: outflow from the left or right side is physically obstructed due to something outside the heart (extracardiac mechanical alteration)
Most common type of obstructive shock is a Pulmonary Embolism
Mechanical shock: tension pneumo, pericardial tamoonade, tension pneumothorax
Decreases in systolic pressire with normal diastolic pressure are indicative of which type of shock?
Cardiogenic shock
decrease in systole only indicates a problem with the heart/pump
Distuinguish between hemorrhagic and non-hemmorhagic forms of hypovolemic shock:
Hypovolemic shock : _______ intravascular volume, _____ preload and ____ CO
- Hemmorhagic shock: ______ intravascular volume due to _____
- Nonhemmorhagic hypovolemic shock: _____ intravascular volume due to ____
Give examples:
Hypovolemic shock means decreased intravascular volume…. reduced preload and reduced CO
Hemorrhagic shock: decreased intravascular volume from blood loss
Nonhemmorhagic hypovolemic shock: decreased intravascular volume from non-blood fluid loss
- GI: diarrhea, vomit, drainage
- Skin: heat stroke, burns, stevens johnson syndrome (mucousal membranes swell during a severe allergic rxn)
- Renal: diuresis
- Third space: trauma, intestine obstructive, crush injury etc.
List some possible clinical signs of non-hemorrhagic hypovolemic shock
Clinical signs of non-hemorrhagic hypovolemia:
Symptoms related to:
- volume depletion, cause of fluid loss
- electrolyte imbalancies
- low arterial blood pressure
- low jugular venous blood pressure
- low urine volume
- normal or increased hematocrit and serum albumin
- manifestations of shock
