CVS 12 (Shock) Flashcards
List some symptoms of Peripheral Artery Disease:
- Intermittent claudication
- Cold extremities
- Weak pulse in legs/feet
Which arteries are usually affected in Peripheral Artery Disease?
- Femoral
- Iliac
Define varicose veins:
Dilated torturous superficial veins
Where is the most common location of venous ulcers, due to varicose veins?
Over the medial malleolus (great saphenous vein)
Define shock:
Acute circulatory failure with either inadequate or inappropriately distributed tissue perfusion, resulting in generalised lack of oxygen supply to cells.
= Decreased MaBP due to decreased CO or TPR
Name the 4 types of shock:
1) Distributive/Normovolaemic shock
2) Hypovolaemic shock
3) Cardiogenic shock
4) Mechanical shock
Which types of shock are caused by a decreased cardiac output?
- Hypovolaemic
- Cardiogenic
- Mechanocal
Which type of shock are caused by a decreased total peripheral resistance?
Distributive
Define cardiogenic shock:
Inability of heart to eject enough blood = decreased cardiac output
Name some possible causes of cardiogenic shock:
- Myocardial infarction
- Arrhythmias
- Acute heart failure
What are the 2 types of mechanical shock, and name a common cause of each:
1) Due to restricted filling of heart
- Cardiac tamponade (infection/trauma/cancer/MI)
2) Due to obstruction to blood flow through lungs
- Pulmonary embolism (from DVT or surgery)
Define hypovolaemic shock:
Decreased MaBP due to loss of circulating volume
Name some possible causes of hypovolaemic shock:
- Haemorrhage due to trauma
- Severe burns
- Severe diarrhoea/vomiting (massive loss of Na+)
What percentage of blood must be lost for body to go into severe shock?
~ 30-40% of normal blood volume lost
What type of receptors detect shock?
High pressure baroreceptors (in arteries)
Low pressure baroreceptors (in veins and heart)
How do the high pressure baroreceptors respond when shock is detected?
Cause increase in SNS activity =
- Tachycardia
- Increased force of contraction (heart)
- Peripheral vasoconstriction
- Venoconstriction
How do the low pressure baroreceptors respond when shock is detected?
Renal reflex (RAAS) activated:
- Increased Angiotensin II = vasoconstriction
- Increased aldosterone = increased H2O reabsorption
- Increased ADH = increased H2O reabsorption
Define ‘transcapillary refill’:
Movement of interstitial fluid into the vasculature (autoinfusion)
What factor limits transcapillary refill during shock?
Haemodilution:
Movement of fluid from interstitium into the capillaries reduces the capillary oncotic pressure
Decreased cerebral perfusion occurs at what MaBP?
< 60 mmHg
What is the compensatory response during shock, when decreased cerebral perfusion is detected?
Massive increase in SNS innervation
What are the classic symptoms of shock due to decreased CO?
- Tachycardia
- Weak pulse
- Pale skin
- Cold and clammy extremities
Name the 2 types of distributive/normovolaemic shock:
1) Toxic/Septic
2) Anaphylactic
List some risk factors for toxic/septic shock:
- Diabetes
- Immunocompromised
- Catheter
- Leukaemia/lymphoma
- Long-term antibiotic use
- Recent infection
- Recent surgery
- Recent steroid use
- Transplant
How does toxic/septic shock cause decrease in MaBP?
Endotoxins cause:
1) Vasodilation = decreased TPR
2) Increased vascular permeability = blood volume
What are the classic symptoms of toxic/septic shock?
- Tachycardia
- Warm and red extremities
What are the symptoms of a pulmonary embolism?
- Shortness of breath
- Sharp, stabbing chest pain
- Peripheral oedema
- Cough
- Cyanosis
List some common causes of anaphylactic shock:
- Medication ie Penicillin
- Food ie Nuts/peanuts/wheat/shellfish
- Insect stings
- Latex
What immune cell is responsible for an allergic reaction? What is the main mediator it releases?
Mast cell
Histamine
Which mediators released in anaphylactic shock cause bronchoconstriction and laryngeal oedema?
- PGD2
- Leukotrienes
What are the classic symptoms of anaphylactic shock?
- Tachycardia
- Difficulty breathing
- Red, warm extremities
- Lightheaded/collapse/unconscious
- Itchy skin/rash
What is the treatment for anaphylactic shock?
Adrenaline shock ie EpiPen
Define hypertension:
Sustained arterial BP > 140/90 mmHg
What are some non-pharmacological treatments for hypertension?
- Increase exercise levels
- Weight loss
- Decreased salt intake
Name some commonly used drugs used to treat hypertension:
- Diuretics (Usually Thiazide, if due to Conn’s syndrome use Aldosterone antagonists)
- ACE inhibitors
- DHP Ca2+ channel blockers
- Alpha-1 antagonists
- ARBs (Angiotensin II Receptor Blockers)
What is the most common type of hypertension, and what is the cause?
Primary/essential hypertension
Unknown cause, associated with increased TPR
How can renovascular disease cause secondary hypertension?
Can causes renal artery stenosis:
- Decreased perfusion pressure activates RAAS
- Vasoconstriction and Na+ retention at other kidney
How can renal parenchymal disease cause secondary hypertension?
Damage to renal parechyma may reduce amount of vasodilators released:
- Decrease GFR = Na+ and H2O retention
What is Conn’s syndrome?
Hypertension and hypokalaemia due to an Aldosterone-secreting adenoma
How can Cushing’s syndrome cause secondary hypertension?
Excess cortisol acts on aldosterone receptors in late DCT and CD = H2O retention
How can a Phaeochromocytoma cause secondary hypertension?
Tumour secretes catecholamines, which bind to alpha-1 adrenoceptors on vasculature = vasoconstriction
What is the body’s major compensatory mechanism to shock?
Reabsorption of tissue fluids into plasma (transcapillary refill)
