Chapter Answers

1. What is the effect on metabolism of reduced blood supply to the tissues? 

Answer: Reduced blood supply diminishes the volume of blood supplying the needs of the cells of the body. Oxygen and nutrient supply is reduced and metabolism moves towards anaerobic metabolism with increased lactate formation and a fall in pH resulting in acidosis. The amount of ATP (energy store for cell function) is drastically reduced. There is thus less energy for the functions required to maintain homeostasis.

2. Describe how atherosclerosis develops and its effect on blood flow. What is the difference between atherosclerosis and arteriosclerosis?

Answer: Chronic inflammation initiates build-up of plaque in the arteries leading to narrowing of the arteries and limited space for blood flow. Plaque is formed of fat, cholesterol, calcium and other substances, which pass through the intima and begin to cause dysfunction of the endothelium and deposition of connective tissue. Atheroma develops over time as:

  • Early fatty streak development
  • Early fibroatheroma
  • Advancing atheroma: thin-cap fibroatheroma and its rupture
  • Complex lesion development

The difference between atherosclerosis and arteriosclerosis is:

  • Arteriosclerosis: the arterial walls become thickened and hardened as smooth muscle is replaced by collagen and hyaline cartilage. No lipid material is deposited. The blood vessel becomes less compliant and is associated with raised blood pressure.
  • Atherosclerosis: fatty material is deposited on the inner walls of the vessels as plaque.

3. Identify the causes of blockage of the veins and describe how an embolism occurs.

Answer: Blockage of the veins can be due to venous thrombosis (the commonest), spasm, or external compression and limits the flow of blood back from the tissues. Venous thrombosis (DVT – deep vein thrombosis) occurs most commonly in the calves of the legs. Risk factors include: surgery or trauma; immobilisation (bed rest or long-haul flights); old age, obesity, heart failure; pregnancy and the puerperium, or the contraceptive pill; familial thrombophilia (an increased level of blood coagulation).

An embolism is when part of the thrombus breaks off and is carried in the bloodstream. It can become impacted in the right side of the heart or carried in the pulmonary artery or arteries to one or both lungs. Emboli can be large (and get stuck in the right ventricle or block circulation to one of the lungs) or many small emboli can enter the lungs and block a number of small blood vessels.

4. What is meant by ‘shock’ and what are the main changes which occur? Specify the different types of shock.

Answer: In shock there is low perfusion of the tissues due to a fall in blood pressure and increased heart rate caused by collapse of the circulation. Reduced blood flow to the organs causes reduced urine output, disturbed consciousness (unconsciousness or confusion), reduced pulse pressure. Shock is a medical emergency necessitating rapid treatment to permit survival. Anaerobic metabolism occurs and inadequate cell function develops. Presentation includes: pale, cold, sweaty skin (possibly with cyanosis of the extremities); confusion and restlessness; low B/P and fast, thready pulse; increased respiratory rate and depth. This will often progress to coma and unless blood flow is restored, multi-organ failure will result in death. The main types of shock are: hypovolaemic, distributive, cardiogenic, obstructive.

5. Clarify the changes that lead to hypovolaemic shock.

Answer: This occurs as a result of a significant decrease in blood volume. The reduced venous return causes reduced cardiac output to supply the organs of the body. Causes include:

  • Bleeding: internal or external blood loss
  • Fluid loss: skin: burns, sweating
  • Fluid loss – GI tract: Diarrhoea, vomiting
  • Fluid loss – Kidneys: diabetes, adrenal insufficiency, salt-losing nephritis, excessive diuretics, diuretic phase of acute renal failure
  • Fluid loss – to extravascular space: Increased capillary permeability due to inflammation, anoxia, sepsis etc.

6. What is meant by distributive shock? Differentiate between the three categories of this type of shock.

Answer: This develops when there is an imbalance between circulatory volume and a dilated circulation, either arterial or venous. The capillaries supplying the tissues are bypassed in various ways, including arteriovenous shunts or blood pooling in capillary beds. The three main types of distributive shock are:

  • Septic shock: due to inappropriate response to infection when tissue perfusion is reduced resulting in failure of a number of bodily organs. DIC (disseminated intravascular coagulation) can occur suddenly with small clots throughout the circulation and mini-infarctions can cause organ damage. These clots use up coagulation factors in the circulation so bleeding becomes uncontrolled. Multiple organ failure can occur.
  • Anaphylactic shock: due to a Type 1 or immediate hypersensitivity to a particular antigen. Anaphylactic shock is severe, being extreme and often life-threatening. Due to bronchospasm causing constriction of the airway and oedema of the respiratory tract leading to difficulty with breathing (dyspnoea).
  • Neurogenic shock: upper parts of the central nervous system (the brain, cervical spine or upper thoracic spine) are severely injured causing hypotension, bradycardia and loss of sympathetic nervous activity to the blood vessels. Damage from thoracic spinal area T5/6 and above inhibits the normal vascular contraction and enables dilation of blood vessels and pooling of blood.

7.  Outline the physiological changes in cardiogenic shock and the main approaches to management.

Answer: This occurs because the heart cannot any longer pump blood round the body adequately. The commonest cause is myocardial infarction (heart attack, MI) but other possible causes exist. Reduced cardiac output and stroke volume cause hypotension and lowered perfusion of tissues. Vasoconstriction aims to compensate for the fall in B/P but decreases the blood supply to tissues. Increased secretion of catecholamines and cortisol increase muscle activity and tissue blood flow, but also raise oxygen requirements. Hypotension and hypoperfusion leads to enhanced inflammation and further tissue damage. Cardiogenic shock results in a mortality rate of 40–50%. Management aims to re-open blocked coronary vessels and reduce blood clotting. Intensive care support maintains physiological function.

8. What is meant by obstructive shock and what are the three main causes?

Answer: This occurs when some physical obstruction prevents normal blood flow which limits ventricular filling and diminishes cardiac output. The pressure exerted by the right ventricle in expelling blood to the lungs is raised and the right ventricle becomes enlarged, while the compression on the left ventricle leads to a decrease in size. Cardiac output and stroke volume are reduced leading to a fall in B/P which exacerbates deterioration and can lead to death. The three main causes are:

  • Pulmonary embolism.
  • Cardiac tamponade: when fluid accumulates in the pericardium around the heart due to pericarditis, blunt chest trauma or surgery. Pressure is on right and left sides of the heart.
  • Tension pneumothorax: when air accumulates in the pleural cavity by escaping from the chest cavity. This may be due to spontaneous rupture of the pleural membrane covering the lungs allowing air to escape into the pleural cavity, or trauma. The trachea deviates from the centre line, breath sounds are reduced and blood gas levels fall. The increasing pressure in the chest causes collapse of the lung on the affected side and shifting and compression of mediastinal structures, including pressure on the heart which limits filling of the left ventricle.

The patient may deteriorate rapidly if the obstruction is not removed quickly.

9. What are the main signs and symptoms of anaemia? Identify at least four types of anaemia.

Answer: The main signs and symptoms are:

  • fatigue, weakness, breathlessness, lightheadedness or dizziness
  • the skin may be pale or yellowish, hands and feet may be cold
  • irregular heart function and chest pain
  • headache

The various types of anaemia include:

  • iron deficiency anaemia: treatment is iron supplements
  • vitamin deficiency anaemia: folate and vitamin B12 needed to form red blood cells
  • anaemia of chronic disease: some diseases disrupt red cell formation
  • aplastic anaemia: rare, life-threatening anaemia – inadequate red blood cells
  • anaemias due to bone marrow disease: certain diseases reduce bone marrow blood production
  • haemolytic anaemias: red blood cells destroyed faster than replaced

10. What is a stroke (CVA) and how does it differ from a TIA? Describe the Public Health England (2018) scale for identifying the occurrence of a stroke.

Answer: A stroke is due to a sudden loss of normal circulation to the brain affecting function. There are two types – ischaemic and haemorrhagic: the second significantly more severe with much higher mortality rate. Effects vary considerably depending on which blood vessels are affected and the size and location of damage to the brain and nervous supply to the body. A major cause of mortality and morbidity in the UK, with 1 in 6 people having a stroke at some time. A transient ischaemic attack (TIA) is similar but lasts less than 24 hours. A scale by Public Health England (PHE) aims to encourage rapid action through the guidance given. The FAST Stroke Campaign stands for: 

  • Face – has their face fallen on one side? Can they smile?
  • Arms – can they raise both their arms and keep them there?
  • Speech – is their speech slurred?
  • Time – to call 999

11. Identify the effects on the heart of reduced blood supply.

Answer: The three main effects on the heart are:

  1. Coronary heart disease: plaque develops in the coronary arteries which normally supply the heart with oxygen-rich blood. Reduces blood flow to the myocardium and increases risk of thrombosis causing complete or partial arterial blockage. Two main conditions can occur: angina and myocardial infarction (heart attack).

  2. Angina: reduced blood flow provides less oxygen to myocardium and blood flow to heart muscle is reduced or blocked, causing angina with pain in the chest, often radiating to shoulders, neck and (left) arm. Treatment relieves the pain rapidly.

  3. Heart attack: serious medical emergency when blood supply to the heart is suddenly blocked, usually by a blood clot, and can lead to sudden death due to serious myocardial damage. The signs and symptoms are similar to angina but more severe and longer lasting. They consist of:

  • Chest pain: like heavy object pressing on the chest and radiating from the chest to the jaw, neck, arms and perhaps back. Chest pain is usual, but not always severe. It can be mild and feels like indigestion

  • Feeling lightheaded or dizzy, sweating

  • Being short of breath, coughing or wheezing

  • Feeling nauseated or vomiting

  • Overwhelming sense of anxiety (similar to a panic attack)