Hypovolaemia Flashcards
What are the biproducts of anaerobic respiration?
Lactic acid
Carbon dioxide
Water
What are the signs of increased oxygen demand?
Tachypnoea
Tachycardia
Cyanosis
What primary factors influence how oxygen is transported?
Reduced haemoglobin count
Oxygen percentage of the blood
Concentration of carbon dioxide
What occurs in metabolic acidosis? With values for pH and bicarbonate
Decrease in pH <7.35 with decreased bicarbonate <22mEq/L
What occurs in metabolic alkalosis? With values for pH and bicarbonate
Increased pH >7.45 with increased bicarbonate >26mEq/L
What may occur to compensate for metabolic alk/acidosis?
Acidosis: increase in RR
Alkalosis: decrease in RR
What 6 aspects does adequate perfusion of body tissues depend upon?
Efficient respiration- inspiration of O2, expiration of CO2
Efficient contraction of the heart to maintain cardiac output
Adequate BP
Ability of the vascular system to transport blood from the left ventricle via the arteries to the cells, allowing the release of O2 and return of deoxygenated blood back to the heart via the veins to the right atrium then lungs.
Sufficient blood volume within the vascular system
Tissues ability to use and extract oxygen and nutrients from the blood
What is the definition of shock
Pathophysiological condition characterised by inadequate tissue and organ perfusion. Seriously reduces the delivery of oxygen and nutrients to the cells causing a reduction in normal cellular activity.
Shock alters what and what?
Circulation and metabolism.
What occurs at the capillary cellular junction?
Oxygen and nutrients are delivered to the body tissues and metabolic waste is removed.
What does shock mainly result in?
Reduced capillary blood flow potentially resulting in diffuse ischaemic hypoxia.
What two factors are involved in diffuse ischaemic hypoxia? And what do they prevent?
Biochemical and neurological factors which interfere with cellular uptake and use of oxygen.
What is the function of ATP in driving sodium-potassium pumps?
To maintain a constant ionic gradient across the cell wall.
What are the values of sodium and potassium inside of the cell?
Sodium: 10mmol/L
Potassium: 140mmol/L
What are the values of sodium and potassium outside the cell?
Sodium: 140mmol/L
Potassium: 10mmol/L
What does the maintenance of the sodium-potassium gradient determine in relation to the cell?
Determines the cell size, shape and function.
During hypoxaemia how does the cell respire?
Anaerobically
What affect does anaerobic respiration have on ATP production?
Decrease in ATP production up to 20 times less resulting in a cellular energy crisis.
What occurs during a cellular energy crisis as a result of shock ?
Sodium potassium pump fails.
Intracellular potassium leaks out of the cell and sodium followed by water leaks in.
This results in cells swelling and becoming irregular in shape.
This change in shape causes specialised cells to lose their specialist function.
What ultimately occurs as a result of a cellular energy crisis during shock?
The influx of sodium and resulting water into the cell causes intracellular lysosomes to rupture.
The release of hydrolytic enzymes result in the cell being autolysed.
The release of vasoactive metabolites and lysozymes from the dying cell stimulate an inflammatory reaction resulting in an accumulation of activated phagocytes.
Phagocytosis causes more cell injury, creating the lytic cycle.
The lytic cycle can result in organ damage and thus decrease in function.
What occurs in the lytic cycle?
Influx of sodium into the cell causes it to swell and lysozymes to rupture.
The release of hydrolytic enzymes autolyse the cell.
Vasoactive metabolites and lysozymes from the dying cell stimulate an inflammatory response activating phagocytes.
Increase in phagocytosis in turn causes more cellular injury increasing the number of activated phagocytes.
Ultimately leading to cell, then tissue and thus organ damage.
What is compensation in relation to shock? And how long does it last for?
Mechanisms that aim to reverse the shock process, only work short term.
What compensatory mechanisms occur in response to decreased arterial blood pressure? And what do they each result in?
Baroreceptors stimulation - increased HR and blood flow directed centrally= increased blood volume.
Volume and osmoreceptor stimulation- increased blood volume.
Juxtaglomerular apparatus stimulation- blood flow directed centrally = increased blood volume.
Cortisol production increased- increased blood volume.
Disengorgement of spleen- increased blood volume.
During decreased arterial BP, what stimulates baroreceptors and how do they work to increase BP?
Baroreceptors are stimulated by the sympathetic autonomic nervous system.
Causing adrenaline to be released which: Increases HR
Heart contractility
Peripheral vasoconstriction
ALL of which increase cardiac output which increases BP.
During decreased arterial BP volume and osmoreceptors are stimulated, how do they work to increase BP?
Anti-diuretic hormone is released from the posterior pituitary gland.
Causing an increase in the renal retention of water which increases blood volume, increasing cardiac output which increases BP.
During decreased arterial BP the juxtaglomerular apparatus is stimulated, how does this work to increase BP?
Renin release from the kidneys, hydrolyse angiotensinogen synthesised by the liver creating angiotensin I which is weakly bioactive. Angiotensin I travels in the blood to the lungs where the angioconverting enzyme (ACE) converts angiotensin I to angiotensin II which is a strong vasopressor hormone. Angiotensin II stimulates the secretion of aldosterone by the adrenal cortex which increases the renal retention of water. This causes blood flow to be directed centrally, increasing central blood volume and thus increasing cardiac output which in turn increases BP.
What are the clinical signs of compensation deteriorating to decompensation? (In terms of: BP, HR, pulse, RR, skin, urine, bowel, GCS, pupils)
BP: systolic <80-90mmHg HR: rapid, >150bpm Pulse: weak, rapid and thready RR: rapid, shallow, crackly Skin: cold and cyanotic Urine: <20ml/hr Bowel: no sounds present GCS: not responding to verbal stimuli Pupils: dilated, reacting slowly to light
What are the 9 stages of decompensation?
- diffuse cellular hypoxia
- Widespread anaerobic metabolism
- Release of cellular potassium, cell death, lactic acidosis.
- Decreased cardiac contractility, arterial vasodilation, increased capillary permeability, capillary pooling
- Cardiac dysrthymias, decreased blood volume
- decreased cardiac output
- Heart failure and brain stem ischaemia
- Vasomotor collapse
- death
What causes cardiogenic shock? Examples
Results from impaired pumping ability of the heart such as post MI, post cardiac trauma
What causes neurogenic shock?
Results from loss of vasomotor tone caused by post brain stem injury or spinal injury above the midthoracic region.
What is an anaphylaxis?
An exaggerated, violent, systemic allergic response to a drug or substance.
What causes obstructive shock? Examples
Conditions that affect the ability of the heart to contract or empty such as pulmonary embolism or cardiac tamponade
What causes hypovalemic shock?
Haemorrhage or redistribution of blood, plasma or other bodily fluid which causes a decrease in the volume of circulating intravascular blood.
What are the 7 causes of hypovolaemic shock?
Haemorrhage
Severe diarrhoea
Vomiting
Abnormal internal fluid distribution as in sepsis
Burns- resulting in plasma loss
Diuresis- increased or excessive urine production
Dehydration
What is the most common cause of hypovolaemic shock?
Haemorrhage
In terms of fluid loss during hypovolamic shock, what two factors determine the degree of shock experienced?
Volume and rate of fluid loss