Lecture 26:

Question 1

Describe the direct cardiovascular
consequences of the loss of 30% of the
circulating blood volume on cardiac
output, central venous pressure, and
arterial pressure.

Answer 1

-Decompensated shock

CO: Decreased

CVP: Decreased

Atrial pressure: Decreased

Question 2

Describe the compensatory mechanisms
activated by these changes.

Explain three positive feedback mechanisms activated during severe haemorrhage that may lead to circulatory collapse and death.

Answer 2

• Takes place in decompensated shock
  1) Decrease Sympathetic activity –> Massive vasodilation –> Reduced Coronary perfusion –> Acidosis –> Decreases CO and MAP –> Decreases tissue perfusion –> Vasodilation
  2) Reduces MAP –> Decrease tissue blood flow –> Increase tissue hypoxia –> Vasodilation –> Decreases MAP
  3) Reduces MAP –> Decreased coronary perfusion –> Decreases contractility –> Decreases CO –> Decreases MAP

Question 3

Contrast the change in plasma
electrolytes, hematocrit, proteins, and
oncotic pressure following resuscitation
from haemorrhage using a) water, b) 0.9%
NaCl, c) plasma, and d) whole blood

Answer 3

water:
plasma electrolytes: Cl decrease
hematocrit: Decrease
proteins: Cl decrease
oncotic pressure: Decrease

0.9% NaCl:
plasma electrolytes: No change
hematocrit: Decrease
proteins: Cl decrease
oncotic pressure: Decrease

plasma:
plasma electrolytes: No change
hematocrit: Decrease
proteins: No change
oncotic pressure: No change

whole blood
plasma electrolytes: No change
hematocrit: No change
proteins: No change
oncotic pressure: No change

Question 4

Types of shock?

Determine the type based on the
effect on CO, Systemic vascular resistance-SVR (Afterload) and PCWP (Preload)

Treatments?

Answer 4

Low Stroke Volume Shocks:

1) Hypovolemic
Cause: Decrease Blood Volume
Due to: Hemorrhage, Diarrhea, Vomiting
Skin: Cold, clammy
Effects: Preload: Decrease, CO: Decrease, Afterload: Increase
-MAP 50-70mmHG = serious shock, irreversible
Treatment: IV Fluids

2) Cardiogenic 
Cause: Pump failure
Due to: MI, Arrhythmias 
Skin: Cold clammy 
Effects: Preload: Increased, CO: Decreased, SVR: Increased
Treatment: Ionotropes, diuresis

3) Obstructive
Cause: Obstruction to blood flow
Due to: Major pulmonary embolism, cardiac
tamponade, tensions pneumothorax 
-Rest is the same as Cardiogenic

Vasodilation /Distributive Shocks:
-All make skin dry and warm, Decrease Prelaod, decrease after load, and can be treated w IV Fluids and Pressors

1) Septic
Cause: Decrease TPR
Due to: Endotoxins
Increase CO

2) Anaphylactic
Cause: Decrease TPR
Due to: Allergic rxn
Increase CO

3) Neurogenic
Cause: Disruption of neurogenic vasomotor control
Due to: Major brain or spinal injury/loss sympathetic
Decrease CO

Question 5

What are the compensatory

mechanisms?

Answer 5

1) Baroreceptor Reflex
- Response to decreased MAP –> Increases MAP –> Preserve perfusion of heart and brain

2) Activation of Renin-Angiotensis System:
(Increases RAS)
-Response to decreased blood volume –> Replaces fluid loss
-Moves fluid from interstitum –> vascular

Question 6

What happens when the body no

longer compensates?

Answer 6

Decompensated shock develops

• Cause: > 30% blood volume, no fluid replacement 3-4 hrs
• Initially: Increases sympathetics –> Baroreceptors

Later: Hypoxia not relieved –> Vasodilation = decrease sympathetic activity –> Decrease CO and MAP

Question 7

Describe the cardiac output, circulation, respiration response to physical exercise.

Answer 7

Circulatory Response:
Action: Increase Blood flow to muscles
-Increased CO bc increased O2 consumption
-Increased output by increased HR and SV by increased contractility
-Sympathetic stimulation and vasodilator metabolites are key mediators

Respiratory Response:
Action: Increases blood flow to both skeletal, cardiac muscles, and pulmonary vessels
-Increased O2 and CO2 consumption —> increased ventilation (rate of breathing)
-Increased CO to meet oxygen needs to demanding skeletal muscles –> Increased pulmonary blood flow
-Arterial PO2 and PCO do not change

Question 8

Explain the adaptations to training in the cardiovascular, respiratory, musculosketetal systems and metabolic adaptations

Answer 8

Adaptations Cardiovascular:

• Muscle mass of ventricles increases –> Increases the force of contraction
• LV size can be increased –> Increase force of contraction
• Increased capillary capacity –> Decreases TPR

Adaptation respiratory:

• Under strenuous exercise lactate builds up when it’s produced faster that it can be metabolized through TCA cycle –> Anaerobic threshold or lactate threshold = increased lactic acid–> Increase ventilation rate
• Doesn’t utilize carbohydrates as the fuel, but fat for metabolism = Decreased lactate accumulation = reduces ventilator demands –> Less sympathetic feedback to heart –> Reduced cardiac oxygen demand = Lower lactate production –> reduced sympathetic effects

Adaptations musculosketetal:

• Increase in size and number of mitochondia
• Increase TCA intermediates in muscle mitochondria
• Increased storage of glycogen
• Increased fat utilization, spare glycogen stores

Question 9

Discuss the benefits of regular physical activity and exercise

Answer 9

Some examples:

-Lowers risk of coronary heart disease and other types

Question 10

Discuss the risks of exercise

Answer 10

-Benefits far outweigh possible risks

Some risks Include:
1) Musculoskeletal injury
2) Arrhythmia
3) Sudden cardiac death (Due to CAD)
4) Bronchoconstriction –> Asthma
5) Hyper/hypothermia, dehydration
6) Amenorrhoea, infertility –> Women low weight
7) Rhabdomylsis - a syndrome caused by injury to skeletal muscle and involves
leakage of large quantities of potentially toxic intracellular contents into plasma

Question 11

Describe the medical evaluations necessary prior to exercise

Answer 11

•Appropriate history with age, past medical history, focusing especially on cardiac,
pulmonary, orthopaedic history.

• History of diabetes, hypertension, hyperlipidaemia.
• General physical condition
• Medication use e.g. Sulphonylureas, insulin, betablockers, nitrates
• Anticipated type of exercise
• Disabilities

• Perform periodic exercise stress testing in asymptomatic clients with multiple
cardiovascular risk factors e.g. Hypertension, diabetes, hypercholesterolaemia,
smoking.

• Screening not necessary for asymptomatic clients at low risk of coronary artery
disease.

• H/O premature myocardial infarct or sudden cardiac death in a first degree
relative < 60 yrs old.

• Appropriate screening blood tests based on history

Question 12

Effects of exercise on the heart?

Answer 12

Increased:

1) HR
2) SV
3) Pulse pressure
4) CO
5) Venous return
6) Mean arterial pressure
7) Arteriovenous O2 difference

Decreased:
1) TPR