Fluid therapy Flashcards
Describe the distribution of fluids in the body
60% body weight is water
5% intravascular
55% extravascular- 40% intracellular, 15% extracellular
What is meant by starlings forces?
Passive exchange of water between capillaries and interstitial fluid, determined by hydrostatic and oncotic pressure
What are the mechanisms of fluid movement between body compartments?
Osmosis
Starlings forces
What are causes of fluid in balance, and examples of each?
Change in volume- dehydration, hypovolaemia
Changes in content- electrolyte imbalance, changed blood glucose, changed blood protein
Changes in distribution- third spacing (too much fluid moves from intravascular to interstitial space)
Define hypovolaemia
State of decreased intravascular volume
Define hypervolemia
Fluid overload, too much fluid in the blood
Define normovolaemia
Normal blood volume
Define hypoperfusion
Condition brought on by sudden and global deficit in tissue perfusion causing inadequate oxygen and nutrient delivery to tissues
Define shock
Cellular or tissue hypoxia, commonly due to hypoperfusion
Define dehydration
Excessive loss of water from extravascular compartment (slowly so has time to redistribute meaning equal loss across all body compartments)
Define intravenous
Within veins
Define colloid osmotic pressure
Pressure exerted by large molecules to hold water in vascular space
Define oncotic pressure
Pressure exerted by proteins in capillaries causing fluid to be pulled back into them
Define oncotic pressure
Pressure exerted by proteins in capillaries causing fluid to be pulled back into them
Describe the physiological consequences of hypovolaemia
Blood loss Reduced pre-load Reduced stroke volume Reduced CO Decreased BP Vasoconstriction and tachycardia to increase peripheral resistance and perfusion to vital organs Blood pressure to vital organs maintained Changes to MM and CRT
What are normal values expected to be seen in normovolaemia in dogs? (HR, MM, CRT, pulse quality, systolic BP, mentation)
HR- 60-120 MM- pink CRT- less than 2 Pulse quality- normal Systolic BP- over 90 Mentation- normal
What are normal values expected to be seen in mild/compensatory shock in dogs? (HR, MM, CRT, pulse quality, systolic BP, mentation)
HR- 130-150 MM- normal to pinker CRT- less than 1 Pulse quality- bounding Systolic BP- over 90 Mentation- normal
What are normal values expected to be seen in moderate shock in dogs? (HR, MM, CRT, pulse quality, systolic BP, mentation)
HR- 150-170 MM- pale pink CRT- 2 Pulse quality- weak Systolic BP- over 90 Mentation- normal to obtunded
What are normal values expected to be seen in severe/decompensatory shock in dogs? (HR, MM, CRT, pulse quality, systolic BP, mentation)
HR- 170-220 MM- pale pink to white CRT- more than 2 Pulse quality- very weak Systolic BP- less than 90 Mentation- obtunded
What is meant by compensatory and decompensatory shock
Compensatory- perfusion maintained as CO and BP maintained
Decompensatory- unable to maintain perfusion to vital tissues
Define obtunded
Slowed responses and lack of interest in environment
Why in decompensatory shock does the heart rate not exceed 220?
Diastole would be too short to properly fill with blood which would further decrease CO
What are the aims of fluid therapy for treating hypovolaemia?
Need to stabilise as life threatening
Rapid fluid resuscitation using large fluid boluses
What are the 3 body compartments?
Intravascular
Intercellular
Interstitial
What clinicopathological parameters indicate dehydration?
Increased PCV- haemoconcentration
Increased urea, creatinine- pre-renal azotaemia (build up of nitrogenous products)
Increased SG of urine- concentrated urine
What physical parameters indicate less than 5% dehydration?
Not clinically detectable but suspected from clinical history
What physical parameters indicate 5-6% dehydration?
Tacky MM
Mild skin tent
What physical parameters indicate 6-8% dehydration?
Dry MM
Mild increase in CRT
Mild to moderate skin tent
Some signs of sunken eyes
What physical parameters indicate 10-12% dehydration?
Dry MM CRT 2-3 seconds Signs of shock Prolonged skin tent Sunken eyes
What physical parameters indicate more than 15% dehydration?
Incompatible with life
What are the aims of fluid therapy for treating dehydration?
Patient is stable so slowly correct extravascular fluid losses, if done to fast increases arterial pressure, triggering baroreceptors and increased diuretic hormone production and urine output which wont help correct dehydration. If patient is renally compromised may become hypervolaemic
Define crystalloid fluids
Solutions containing solutes dissolved in water
Define colloid fluids
Solutions containing large molecules
What are some complications associated with using fluid therapy?
Are drugs
Consider use when patient has cardiac disease, heart failure, renal disease, respiratory disease etc. as more likely to become hypervolaemic
Volume overload causing pulmonary oedema, cavity effusions, chemosis (eye irritation, outer surface of eye swollen) etc.
What are maintainance fluid requirements?
2ml/kg/hour or 50ml/kg/day
What is the calculation for dehydration deficit?
body weight(kg) x % dehydrated(decimal) then convert from kg to ml (1kg=1000ml)
or
(actual PCV-normal PCV) x bodyweight(kg) x 10
What is the calculation for ongoing losses?
number of times vomited/diarrhoea x 4ml x bodyweight(kg)
How do you calculate total fluid requirement over 24 hours?
Total fluid requirement in 24 hours(ml) = dehydration deficit + maintenance volume + ongoing losses
Total fluid requirement / 24 = ml/hour
ml/hour / 60 = ml/minute
ml/minute x giving set factor = drops/minute
60 / drops/minute = seconds between each drop
List routes of administration of fluid therapy and explain how they work
Per-os- through the mouth by drinking or feeding tube, water absorbed by intestinal tract
Subcutaneous- injected under skin, absorbed into capillaries
Intravenous- IV catheter delivers fluid to veins
Intraosseous- injected into bones medullary cavity, absorbed into vessels
Central venous access- intravenous catheter delivers to non-peripheral vein
What are advantages and disadvantages on per-os fluid administration?
Advantages- non-invasive, least stressful, natural so body controls uptake and electrolytes
Disadvantages- slow uptake, cant if vomiting, body needs to be able to balance fluids, must be willing to drink, harder to monitor
What are advantages and disadvantages on subcutaneous fluid administration?
Advantages- body distributes as needed, good when IV access hard
Disadvantages- more invasive, cant give large boluses, slow absorption
What are advantages and disadvantages on intravenous fluid administration?
Advantages- can give large boluses, can give drugs or electrolytes alongside
Disadvantages- need IV access, more invasive, infection risk, body needs ability to redistribute
What are advantages and disadvantages on intraosseous fluid administration?
Advantages- quickly absorbed, good when cant gain IV access
Disadvantages- painful, invasive, body needs to redistribute, risk of infection
What are advantages and disadvantages on central venous fluid administration?
Advantages- rapid absorption, can give large boluses, easier location to place IV when critical
Disadvantages- invasive, haemorrhage, body needs ability to redistribute
How do crystalloid fluids work?
Water and solutes move freely across membranes allowing distribution within hour of admin
Define isotonic crystalloids, hypotonic crystalloids and hypertonic crystalloids
Isotonic- same tonicity as plasma
Hypotonic- lower tonicity than plasma
Hypertonic- higher tonicity than plasma
What are examples of isotonic crystalloids?
0.9% NaCl
Hartman’s
What is the general electrolyte concentration of isotonic crystalloids?
Mimic intravascular electrolytes, high sodium and low potassium
What are indications for use for isotonic crystalloids?
Replace ongoing losses
Hypovolaemia
Dehydration
0.9% NaCl also used for managing hypochloraemia, hypercalcaemia and hyperkalaemia
What may need to be given to patients when using isotonic crystalloids?
Serum potassium may need supplementing
What are warnings associated with using 0.9% NaCl?
Hypokalaemia- no potassium
Acidosis- more acidic than plasma, no buffers
Hypernatremia and hyponatraemia
What are warnings associated with using Hartman’s?
Dont mix with blood products- clotting risk as calcium interferes with anticoagulants
Risk of precipitation when mixed with sodium bicarbonate
What are the uses of hypertonic crystalloids and how do they work?
Large animals where too large volume of isotonic would be needed, commonly to manage hyponatraemia and intercranial hypertension
Draws out fluid from extravascular compartment which is replaced once stable
What are examples of hypertonic crystalloids?
7.2% and 7.5% NaCl
When cant you use hypertonic crystalloids?
Dehydrated
When are hypotonic crystalloids used?
Rarely, manage hypernatremia
What are examples of hypotonic crystalloids?
0.18% NaCl and 4% glucose (glucose makes solution isotonic at admin to prevent irritation, metabolised to become hypotonic)
How do colloid fluids work?
Large molecules cant cross semi-permeable membranes so increase colloid osmotic pressure in intravascular system
When are colloids indicated for use?
Rarely used in vet medicine
Managing hypovolaemia- 5ml/kg boluses to total 10(cats)-20(dogs)ml/kg to reduce rate of crystalloid therapy by 50%
Coagulopathies- plasma due to clotting factors
Management of hypoproteinaemia- poorly effective
Name examples of colloid fluids
Natural- plasma
Synthetic- gelatine, hydroxyethyl starches
State some risks of colloid therapy
Coagulopathy
Allergic reaction
What are the general stages of shock when not treated?
Cells dont receive enough oxygen Anaerobic respiration so lactate and H+ produced Cell death Organ damage Death
What are the equations for BP and CO?
BP = CO x systemic vascular resistance CO = HR x SV
What are the 4 main types of shock?
Hypovolaemic- decreased blood volume
Obstructive- physical obstruction to blood flow
Cardiogenic- reduced cardiac output
Distributive- widespread vasodilation causing poor blood distribution
Describe what causes hypovolaemic shock
Internal or external haemorrhagic or non-haemorrhagic fluid losses or reduced fluid intake causing low blood volume, blood pressure and perfusion
What are causes of cardiogenic shock?
Dilated cardiac myopathy
Pericardial tamponade
AV block
Arrhythmias
What are causes of obstructive shock?
Gastric dilation-volvulus
Pericardial tamponade
Pneumothorax
thromboembolisms
What are causes of distributive shock?
Anaphylaxis
Generalised uncontrolled inflammatory response
Non-infectious injury
What are common signs of shock in cats?
Pulse quality changes
Bradycardia
Hypothermia
What is initial treatment of hypovolaemic shock?
Rapid fluid administration to restore intravascular volume and improve perfusion
Treat underlying cause of hypovolaemia
What is meant by shock dose?
Patients total blood volume
Describe how crystalloids are given to patients in hypovolaemic shock
20 minute bolus then reassess
Further bolus if needed
Move to maintenance when CV parameters normal
If no improvement after 2-3 boluses consider blood product
Aim to not reach shock dose as can cause volume overload, if reached reconsider approach/diagnosis
How do you monitor and assess effectiveness of fluid treatment of shock?
Monitor every 15-30 minutes Mentation HR Pulse quality MM CRT Temperature Lactate will decrease as treatment takes effect Urine output should exceed 0.5ml/kg/hour
Why are supportive diagnostics used for fluid therapy?
Support assessment of patient status
Investigate underlying cause
Decide best course of treatment
Monitor effectiveness of treatment
What is meant by minimum database and what does it include?
Commonly used diagnostic tests used in critically ill patients, quick and cheap PCV TS Urea Glucose Lactate Blood smear analysis
What tests can be run beyond the minimum database?
Electrolyte levels Minerals Acid base balance Blood gas analysis Urinalysis Common in emergency medicine
What are normal values for PCV and TS?
PCV dogs- 35-55%
PCV cats- 25-45%
TS- 50-70g/l
What are potential causes of increased PCV and normal TS?
Polycythaemia (high RBC)
Dehydration with protein loss
What are potential causes of normal PCV and increased TS?
Hyperglobulinaemia
Lipemia
What are potential causes of normal PCV and decreased TS?
Acute haemorrhage
Hypoproteinaemia
What are potential causes of decreased PCV and normal TS?
Haemolytic anaemia
What are potential causes of decreased PCV and decreased TS?
Haemorrhage
Anaemia
Aggressive IVFT
What are potential causes of increased PCV and increased TS?
Dehydration
How are PCV and TS tests carried out?
Using micro-haematocrit tubes allowing observation of visual changes
How are urea tests carried out and what do results mean?
Dipstick blood urea nitrogen
Low values- accurate
High values- confirm with lab tests
What are causes of high urea in the blood?
Pre-renal, renal or post-renal issues
What are causes of low blood urea?
Severe hepatic dysfunction
Why does blood glucose levels need correcting for IVFT?
Therapy wont work in hypoglycaemic patients
When is it indicated to check blood glucose levels?
Altered mentation Seizures Paediatric patients Distributive shock Diabetes history
What are causes of hypoglycaemia?
Young patients Sepsis Insulin overdose Hypoadrenocorticism Severe hepatic dysfunction Insulinoma
Causes of hyperglycaemia?
Uncontrolled diabetes Stress Head trauma Seizures Hypovolaemia
What does lactate levels in the blood show?
Tissue hypoxia
High in shock patients
What do blood smear analysis show?
Type on anaemia Morphology changes of RBC WBC count Platelet count Parasites
When are blood ketones measured?
Patients with high blood glucose
What is the effect of hyperkalaemia?
Affected myocardial conduction
What causes hyperkalaemia?
Decreased urinary excretion
Major cell death causing translocation extracellularly
Insulin deficiency
Acute acidosis
How is hyperkalaemia treated?
IVFT of isotonic crystalloids
Calcium gluconate to stabilise myocardium
Glucose and insulin to more potassium intracellularly
Treat underlying cause
Signs of hypokalaemia
Weakness
Lethargy
Anorexia
Hypoventilation
What causes hypokalamia?
Increased loss
Translocation intracellularly
Decreased intake
How is hypokalaemia treated?
Treat underlying cause
Supplement potassium, not bolus
What is the important factor regarding sodium abnormailitys?
The rate of the abnormality developing rather than amount of sodium
What happens when sodium levels suddenly change?
Body can’t adapt to fast changes
Neurological signs due to oedema and dehydration
Causes of hypernatremia?
Solute gain
Pure water deficit
Loss of water in excess of sodium
Causes of hyponatraemia?
Impaired water excretion
Polydipsia
Loss of sodium in excess of water
How to treat sodium imbalances
Treat underlying cause with treatment for any clinical signs
Dont make rapid changes as makes worse, correct sodium over 24-48 hours
How should chloride levels be assessed?
Should be 1:1 with sodium
If abnormal determine if proportionate with sodium levels
What are causes of hypocalcaemia?
Eclampsia
Pancreatitis
Urethral obstruction
What are signs of hypercalcaemia?
Anorexia
Lethargy
Shivering
Vomiting
How is hypocalcaemia treated?
Calcium gluconate IV
ECG monitoring
What are signs of hypocalcaemia?
Panting
Hyperthermia
Facial pruritis
How is hypercalcaemia treated?
Correct dehydration and underlying cause
What are causes, compensatory mechanisms and presentation of metabolic acidosis?
Causes- loss of base, acid excretion failure, acid accumulation
Compensation- hyperventilation
Presentation- low pH and pCO2
What are causes, compensatory mechanisms and presentation of metabolic alkalosis?
Causes- iatrogenic, excess HCO3- admin, loss of acid
Compensation- hypoventilate
Presentation- high pH and pCO2
What are causes, compensatory mechanisms and presentation of respiratory acidosis?
Causes- hypoventilation
Compensation- kidneys retain more HCO3- and excrete more H+ slowly
Presentation- low pH and high pCO2, over time HCO3- increases
What are causes, compensatory mechanisms and presentation of respiratory alkalosis?
Causes- hyperventilation
Compensation- kidneys increase HCO3- elimination
Presentation- high pH and low pCO2, gradually decreasing HCO3-
Define metabolic acidosis
High H+ and low HCO3-
Define metabolic alkalosis
High HCO3-
Define respiratory acidosis
High blood CO2
Define respiratory alkalosis
Low blood CO2
What can be supplemented when patient is acidotic?
Na2CO3
