PATIENT SUPPORT - Advanced Fluid Therapy Flashcards
What are the indicators for fluid therapy?
Dehydration
Shock
Correct electrolyte abnormalities
Maintain oncotic pressure
Provide maintenance fluids
Diuresis
What is dehydration?
Dehydration is a deficit of total body water
Dehydration results in a decreased volume within the interstitial space. As dehydration worsens, it can affect the vascular and intracellular compartments as well, leading to dehydration with concurrent hypovolemia
What are the general causes of dehydration?
Decreased fluid intake
Increased pathological fluid loss
What can cause decreased fluid consumption?
Anorexia
Starvation
What are some of the causes of pathological fluid loss?
Vomiting
Diarrhoea
Renal disease
Panting (i.e. secondary to pyrexia)
Wound exudation
Third space fluid loss
What are the clinical signs of dehydration?
Skin tenting
Dry mucous membranes
Sunken eyes
What are the clinical signs of a patient less than 5% dehydrated?
Not clinically detectable
What are the clinical signs of a patient 5 - 6% dehydrated?
Subtle skin tent
What are the clinical signs of a patient 6 - 10% dehydrated?
Moderate skin tent
Tacky mucous membranes
Possibly sunken eyes
What are the clinical signs of a patient 10 -12% dehydrated?
Marked skin tent
Dry mucous membranes
Sunken eyes
What are the clinical signs of a patient 12 - 15% dehydrated?
Marked skin tent
Dry mucous membranes
Sunken eyes
Clinical signs of hypovolaemia
What are some other indicators of dehydration other than clinical signs?
Increased PCV/TS
Weight loss
What are your aims when treating dehydration?
When treating dehydration your aims are to replace the fluid deficit over 24 hours as well as provide maintainence fluids and account for ongoing losses. It is also important to assess patient parameters (improved clinical signs) throughout the fluid therapy process with the goal of correcting the full fluid deficit within 24 hours
How do you treat dehydration?
Fluid therapy with isotonic crystalloid fluids
What are isotonic crystalloid fluids?
Isotonic crystalloid fluids are fluids containing water and electrolytes in a similar composition of extracellular fluid (ECF)
What are four examples of isotonic crystalloid fluids?
0.9% NaCl
Ringer’s solution
Hartmann’s (also known as lactated ringers)
Plasmalyte 148
What is the composition of 0.9% NaCL?
Water
Sodium
Chloride
What is the composition of Ringer’s solution?
Water
Sodium
Chloride
Potassium
Calcium
What is the composition of Hartmann’s?
Water
Sodium
Chloride
Potassium
Calcium
Lactate
What is lactate?
Lactate is a bicarbonate precursor which is metabolised by the liver into bicarbonate
What is the composition of plasmalyte 148?
Water
Sodium
Chloride
Potassium
Calcium
Acetate
What is acetate?
Acetate is a bicarbonate precursor which is metabolised by the muscle into bicarbonate
What is the most common route of administration for fluid therapy?
Intravenous fluid administration
When is oral and subcutaneous fluid administration indicated?
Oral and subcutaneous fluid administration is indicated for mild dehydration
What can cause patients to remain clinically dehydrated even with fluid therapy?
Technical issues with fluid administration
Incorrect estimation of dehydration
Ongoing fluid losses
How do you estimate ongoing fluid losses?
You have to reassess your patient every 4 hours and if possible measure the ongoing losses and account for these losses when calculating/altering your fluid rate
What are some of the clinical signs of hypokalaemia?
Asymptomatic
Muscle weakness
Polyuria, polydipsia (PUPD)
What are the general causes of hypokalaemia?
Decreased intake of potassium
Translocation of potassium
Increased loss of potassium
What are some of the gastrointestinal causes of hypokalaemia?
Vomiting
Diarrhoea
How do you correct hypokalaemia?
Fluid therapy using an isotonic crystalloid fluid spiked with potassium
What are some of the main causes of hypernatraemia?
Diabetes insipidus
Neurological disease
How do you correct hypernatraemia?
Bespoke fluid therapy where the change in serum sodium levels is less than 0.5mmol/l/hr
Why should you correct hypernatraemia with a fluid rate of less than 5mmol/l/hr?
In response to hypernatraemia the brain cells produce idiogenic osmoles as a protective mechanism from the high osmolality in the plasma which could draw fluid from the brain cells causing the brain to become dehydrated. Idiogenic osmoles increase the intracellular osmolality to minimise the loss of intracellular water in the brain. However, becaused of these idiopathic osmoles, rapid correction of hypernateaemia can be fatal as a rapid decrease in serum sodium levels will rapidly decrease the osmolality of the blood relative to the cells, causing fluid to move into the brain cells and cause swelling of the brain
How do you correct hyponatraemia?
Fluid therapy using an isotonic crystalloid fluid at a rate of less than 5mmol/l/hr
Why should you correct hyponatraemia with a fluid rate of less than 5mmol/l/hr?
There is a risk of myelinolysis
What is one of the main functions of albumin?
Albumin is a plasma protein which generates oncotic pressure which is a pressure gradient that pulls fluid into the vasculature
What are the general causes of hypoalbuminaemia?
Decreased production of albumin
Increased loss of albumin
What can cause decreased production of albumin?
Hepatic disease
What can cause an increased loss of albumin?
Protein-losing enteropathy
Protein-losing nephropathy
Negative acute phase protein (decreases with inflammation)
Third space losses
When are serum albumin levels classified as critically low?
Serum albumin levels of less than 15g/l is classified as critically low
How do you correct hypoalbuminaemia?
Correcting hypoalbuminaemia is challenging and often requires treatment of the underlying disease which is causing the hypoalbuminaemia, however, synthetic colloids can be used to try and help maintain oncotic pressure. This should be done in addition to isotonic crystalloid fluid therapy
Which rate of synthetic colloids can be used to attempt to maintain oncotic pressure due to hypoalbuminaemia?
20ml/kg/day
What are synthetic colloids?
Synthetic colloids are fluids containing large molecular weight particles (such as starch or gelatin) which cause rapid expansion of the intravascular volume and cannot easily diffuse out of the intravascular space
What are the potential side effects of synthetic colloids?
Dilutional coagulopathy
Renal failure
Anaphylaxis
What is the most common synthetic colloid available for use in the UK?
Haemaccel (gelatin based colloid)
Other than synthetic colloids, what else can be used to correct hypoalbuminaemia?
Fresh frozen plasma
Human serum albumin
What are the limitations of fresh frozen plasma for correcting hypoalbuminaemia?
Fresh frozen plasma is expensive and not very effective at correcting hypoalbuminaemia
What are the benefits and limitations of human serum plasma for correcting hypoalbuminaemia?
Human serum plasma is very effective at correcting hypoalbuminaemia however there is a risk of anaphylaxis due to an autoimmune response against the human plasma
Which electrolyte and acid base imbalances can be seen with diarrhoea and vomiting?
Hypokalaemia
Metabolic acidosis
How do you correct the electrolyte and acid base imbalances seen in patients with diarrhoea and vomiting?
Hartmann’s spiked with potassium. The hartmann’s spiked with potassium will correct the fluid deficit and hypokalaemia as well as provide lactate which will be converted into bicarbonate and correct the metabolic acidosis
What is pre-pyloric vomiting?
Pre-pyloric vomiting is the evacuation of gastric contents before the pylorus
Which electrolyte and acid base imbalances can be seen with pre-pyloric vomiting?
Hypokalaemia
Hyponatraemia
Hypochloraemia
Hypochloraemic metabolic alkalosis
How does the body self-perpetuate states of metabolic alkalosis?
The body will prioritise correcting volume loss over correcting the metabolic alkalosis through increasing renal reabsorption of water and bicarbonate into the blood and secreting chloride into the urine which will help to correct volume loss however will exacerbate the metabolic alkalosis. A chloride (Cl-) depletion stimulates the kidneys to resorb bicarbonate ions (HCO3-) to maintain electroneutrality. The HCO3- ions would bind to H+ in the blood, further increasing the pH and maintaining the alkalosis. This will also result in paradoxical aciduria due to the increased secretion of chloride into the urine
How do you correct the electrolyte and acid base imbalances seen in patients with pre-pyloric vomiting?
Fluid therapy with chloride containing fluids such as 0.9% NaCl to correct the alkalosis. You may also have to spike these fluids with potassium
How can you use fluids in the management of intestinal obstructions?
Fluid therapy can be used to correct any dehydration, electrolyte and acid base imbalances seen with intestinal obstructions, especially as these cases are often surgical and these factors need to be corrected prior to anaesthesia. Generally these patients will have diarrhoea so will be hypokalaemia and acidotic (so give fluids appropriately)
Which features of liver disease can affect fluid choice for fluid therapy?
Hypoalbuminaemia
Hypoglycaemia
Hypokalaemia
Coagulopathy
Acid/base imbalances
Hepatic encephalopathy
Ascites
Why should hartmann’s ideally not be used in patients with severe hepatic dysfunction?
Hartmann’s contains lactate which needs to be metabolised into bicarbonate by the liver. Thus if you are trying to correct acidosis, this will not be achieved as the lactate will not be converted to bicarbonate by the liver
What is the difference between replacement fluids and maintenance fluids?
Replacement fluids are are intended to correct fluid deficits and replace lost body fluids and electrolytes. Maintenance fluids are used to maintain normal hydration and electrolyte balance for a long period of time in patients unable to intake oral fluids
How does the composition of replacement and maintenance fluids differ?
Replacement fluids have a higher sodium content to restore the sodium lost in excess with fluid deficits. However, maintenance fluids have a lower sodium content compared to replacement fluids, as the primary goal is to maintain normal hydration. Maintenance fluids also typically have higher potassium levels to replace the daily potassium losses, as potassium is usually lost in small amounts daily through urine
What are the potential complications of fluid therapy?
Iatrogenic electrolyte disturbances
Catheter complications
Volume overload
What are the clinical signs of fluid overload?
Chemosis
Serous nasal discharge
Increased respiratory, rate and effort (due to pleural effusion)
Restlessness
Peripheral oedema
Polyuria
Due to venous congesion secondary to fluid overload
What is chemosis?
Chemosis is swelling of the conjunctiva
Which patients are predisposed to fluid overload?
Renal disease patients
Cardiac disease patients
Hypoalbuminaemia patients
Pulmonary contusion patients
