Integrated Cardiovascular Responses II, Hemorrhage, Shock and Ageing Flashcards
Definition of revealed haemorrhage
Obvious lending, quantity often hard to measure accurately
Definition of concealed haemorrhage
Bleeding not obvious but can occur in trauma
Definition of circulatory shock
Generalised inadequacy of blood flow throughout the body
Can lead to tissue damage due to inadequate O2 delivery and other nutrients
Definition of hypovolemia
State of decreased intravascular volume
May be due to loss of salt and water or decrease in blood volume
Definition of cardiogenic shock
Heart suddenly can’t pump enough blood to meet the needs of the body
Most often caused by MI
Definition of cardiopulmonary stretch receptors
Mechanoreceptors in the heart and large pulmonary vessels that respond to changes in the blood volume
Activate reflexes that reverse volume change, support BP and CO
Definition of haemodilution
Decreased conc of cells and solids in the blood resulting from gain of fluid
Definition of acute lung injury (ALI)
Characteristic form of parenchyma lung disease and represents a wide range of severity from short lived dyspnoea => terminal resp failure
Definition of acute respiratory distress syndrome (ARDS)
Life threatening condition when lungs cant provide enough O2
Definition of non progressive shock
Shock that gets better without treatment
Definition of refractory shock
Shock where death is inevitable
Definition of disseminated intravascular coagulation
Appearance of clots all over the body, cause damage
Definition of arteriosclerosis
Stiffening, increased fibrosis and calcification of arteries
What are the 2 main types of haemorrhage
Revealed, obvious bleeding, quantity hard to measure accurately
Concealed, can be due to trauma or other problems
What trauma can cause a concealed haemorrhage
Ruptured spleen
Pelvic floor fracture
Renal damage
What are the other possible causes of a concealed haemorrhage
Leaking aortic aneurysm
Ruptured ectopic pregnancy
Bleeding peptic ulcers before vomit
What are the possible effects of haemorrhage and what are they dependent on
Depends on the volume and speed of blood loss
- Chronic, slow, persistent => Fe deficiency anaemia
- Acute large loss => decrease in circulatory volume and circulatory shock
What is circulatory shock and what can it result it?
What can it be cause by
Generalised inadequate flow of the blood in the body
If prolonged, causes inadequate O2 and nutrient delivery => tissue damage
Caused by
- Haemorrhage
- Hypovolumia
- Cardiogenic
- Anaphalaxis
- Sepsis
What are the signs and symptoms of circulatory shock
Anxiety, restless, confused, aggressive, lethargic, coma
Rapid shallow breaths, rapid weak pulse
Intense thirst, nausea
BP generally low, pulse pressure always low
Pale, grey cyanosis, clammy skin
Reduced urine output
Acidotic, decreased coagulation time, increased neutrophils
According to the WHO Haemorrhage classification system, what are the effects of minimal blood loss (<15%)
Shock unlikely in fit individual
According to the WHO haemorrhage classification system, what are the effects of mild blood loss (20-30%)
Generally induces shock
BP falls but not life threatening
According to the WHO haemorrhage classification system, what are the effects of moderate blood loss (30-40%)
Severe shock, significant fall in BP and CO
May become refractory
According to the WHO Haemorrhage classification system, what are the effects of severe blood loss (>50%)
Death inevitable
How does the rate of blood loss affect your chances of survival according to the WHO
Rapid 30% loss => death
50% loss over 24hrs => could survive due to compensatory mechanisms
What are the immediate forms on compensation
Why do we have compensation?
Maintain BP and CO despite the fall in BV
Reverse stress contraction Reflex response CNS ischaemic response RAAS activation Baroreceptor reflex
What is reverse stress contraction
Most blood in veins => VC
Maintains venous P => maintains CVP => increased CO => increased BP
-Starts 10 mins after bleed
What are the reflex responses
Increased HR and contractility => increased CO
Peripheral VC in skin, splanchnic, renal, muscle to increase BP
Increased sweating due to SNS activation via M3 cholinergic receptors
What is the CNS ischaemic response
When is this activated
When MABP < 50mmHg
Profound peripheral VC => more blood to brain
Splanchnic, renal perfusion severely reduced => dangerous if sustained
What happens when the RAAS system is activated
Electrolyte, water retention
VC, thirst, ADH
All maintain BV
What is the baroreceptor reflex
Decreased PNS stimulation Increased SNS stimulation -Increased HR, contractility, CO -Venoconstriction => increased CVP -VC of splanchnic, skin, renal, skeletal muscle => increase TPR
Describe the acute response to severe blood loss
Describe the pathway of action
Cardiopulmonary stretch receptors in heart and large pulmonary vessels
Respond to changes in BV
Decreased BV => decreased stretch atria and cardiopulmonary receptor stimulation => hypothalamus and brain stem => increased ADH and A => increased VC => increased CVP, TPR, CO, BP => increased thirst and water reabsorption
Describe blood volume and flow when there is no blood loss
All organs have an appropriate blood flow
Arterial P = normal
Vascular R = normal
F =normal
Describe the flow of blood during a moderate haemorrhage
SNS VC of splanchnic, renal, muscle skin
-Vascular R increased => decreased F
Coronary, cerebral circulation
-Vascular R normal => normal F
MABP is normal
Decreased CO
Increased TPR but pulse P is low
Describe what systolic and diastolic pressure is determined by and the effects of haemorrhage on pulse pressure
Systolic dominated by CO => falls
Diastolic determined by VC => rises
Pulse pressure is the difference between the 2 => weak
How is blood volume restored
Internal transfusion associated with haemodilution (within hours)
Increased thirst, decreased urine production
Increased renal Na and water reabsorption (days)
What is internal transfusion
VC and decreased venous P => decreased capillary hydrostatic P
Net absorption occurs as net force => -ve
Increased hepatic glucose production/release => increased capillary oncotic P => net absorption
Describe the renal mechanisms that help restore the blood volume
Decreased BP, BV
Carotid sinus baroreceptors, decreased atrial stretch
Hypothalamus and brain stem
Increased thirst, ADH, SNS
Decreased diuretics, increased renin, Ang 2, aldosterone
Increased Na, water reabsorption
BV restored
How does the quality of blood recover
Contents take around 6 weeks to recover (120 days = RBC lifespan)
Erythropoietin prod from kidney stimulated in renal hypoxia
Plasma proteins produced in liver
Reticulocytes count increases by 5-15% => increased RBC counts
How to restore haemoglobin in the blood
[Hb] immediately after haemorrhage = normal as no of RBCs and plasma volume have fallen to the same extent
In haemodilution BV= normal but [Hb] and RBC nos fall
6 weeks until full recovery
Blood gas reduced O2 carrying capacity but effect lessened by decreased viscosity which favours perfusion
What are the 3 other responses to haemorrhage
Increased ventilation
- Decreased flow through carotid bodies
- Acidosis, decreased pH
Increased platelet and fibrinogen
- Decreased coagulation time
- All clotting factors decreased, all used up
Increased WBC for ALI/ARDS
What is non progressive shock and how long does it take to restore the blood volume
Gets better without treatment (<20% blood loss)
Restored within 16-24 hours
After a blood donation
What is refractory shock and what should you do before you reach this stage
If loss, greater than 30%, CO may improve due to compensation but will worsen unless transfusion given within reversible shock phase (golden hour)
Transfusions in irreversible shock cant help as irreversible cardiac damage has occurred
What happens during circulatory failure
Decreased BP
Decreased perfusion
Hypoxia, increased acidosis, toxins and DIC
Decreased cardiac function and CO
Decreased vascular tone, increased vascular permeability and fluid loss to tissues
Loss of proteins to TF, loss of oncotic P grad
Lead to multi organ failure Renal failure Intestinal mucosal damage Sepsis Cardiac failure ARDS Hepatic failure
What are the 4 cardiovascular effects of ageing
Changes in artery wall structure (arteriosclerosis)
Increase in systolic, decrease in diastolic
Decreased baroreceptor sensitivity
Impaired cardiac performance in exercise
How does systolic and diastolic pressure change in ageing
Systolic P increases => HTN
Diastolic P increases then falls
Describe the vascular changes in ageing
Decreased compliance in larger arteries
Elastic layers => thin and fragmented => arterial dilation
Collagen increases => increased stiffness, intimal layer thickens
SNS increases, NO release decreases => Increase in TPR, decrease in VD => decreased muscle flow in exercise
Lead to increase in systolic, pulse pressure and afterload
Describe how arterial stiffening can lead to isolated systolic hypertension and widening of pulse pressure
Normally pulse wave reflected back by branching arteries
With age and HTN, pulse wave reflected back faster due to decreased compliance
Pulse wave returns faster, merges with forward wave => increased systolic
Decreased elasticity => decreased F => decreased diastolic
Results in widening of pulse pressure
Describe the cardiac changes in ageing at rest
Little effect on resting cardiac function
Cardiac fibrosis => decreased relaxation and diastolic filling => decreased CO
Describe the cardiac changes in ageing in stress
Less able to increase CO in stress
- Max HR = 220 - age
- Decreased contractility => decreased SV
Decreased B1 response, decrease in myocytes
Increased afterload due to increased stiffness => decreased SV and CO => increased cardiac O2 demand
Describe how the cardiovascular reflexes change with age
Baroreceptor reflex still works but slower
-SNS, PSN responses impaired
Cardiopulmonary reflexes attenuated
-Fluid and electrolyte imbalances, harder to deal with
