Fluids and Anaphylaxis Flashcards
Why are children more at risk of hypothermia than adults?
Larger % body water. Water has a high specific heat capacity therefore it takes longer for a hypothermic child to readjust to their optimum body temperature because more water has to heat up.
Describe the fluid compartments of the human body
60% of our body is water
Intercellular fluid - 40%
Extra cellular fluid- 20% (interstitial fluid>plasma)
What is osmosis ?
Net diffusion of water across a semipermeable membrane from an area of high water contraction to low water concentration (low solute concentration to high solute concentration)
What is osmolarity ? What is the difference in units in osmolarity and osmolality ?
Osmolarity is the total solute concentration of a solution . Osmolarity is measured in kg whereas osmolality is measured in mols
What is hydrostatic pressure?
The pressure exertion by a fluid
What is oncotic pressure?
Oncotic pressure is a type of osmotic pressure that is generated by plasma proteins preventing the net diffusion of water from an area of high water concentration to low water concentration.
What is an isotonic solution?
Solution that contains the same number of non penetrating solute molecules as those in extra cellular fluid
What is a hypertonic solution?
Solution that contains more non penetrating solute particles than normal extracellular fluid
What is a hypotonic solution?
Solution that contains fewer non penetrating solute particles than normal extracellular fluid
List 5 things that can alter fluid distribution in the human body?
ADH, aldosterone , ANP, oestrogen, progesterone, glucocorticoids
+ baroreceptors
What is starlings equation (in relation to fluid)?
The net direction of fluid across vasculature as a result of the hydrostatic and oncotic pressure acting against ex
What is the metabolic consequence of rapid saline 0.9% infusions?
Hypercholaemic metabolic acidosis.
Strong ion theory. A strong ion is one that dissociates straight away when in water. NA+ and Cl- are both strong ions in this sense.
Strong ion difference (SID) affects pH with a decrease in SID reducing the pH. The difference between NA+ and Cl- dissociation dictates pH. Increase in Cl- relative to NA+ increases the dissociation of water, increasing the number of H+ ions resulting in a metabolic acidosis as the SID decreases.
What type of shock is anaphylaxis? What is the definition of this shock?
Distributive shock . Low systemic vascular resistance secondary to the release of vasodilators
What is the definition of shock ?
Acute circulatory failure resulting in inadequate/inappropriate tissue perfusion which leads to decreased delivery of oxygen to tissues
Explain the pathophysiology of anaphylaxis
Genetically predisposed individual exposed to allergen ‘sensitisation’
APC T helper stimulate memory B cells which result in B cell production of IgE.
IgE circulate the body and bind to mast cells. When the person is exposed to the allergen for the second time, the allergen binds to the IgE antibody on the mast cell causing the release of histamine and other inflammatory markers.
This exact process also occurs in basophils
Describe and explain the symptoms of anaphylaxis
Acute onset
Life threatening airway / breathing problems- smooth muscle contraction, laryngeal oedema leads to wheeze and stridor
Skin changes - urticaria rash, hives, angioedema, mouth and tongue swelling.
What GI symptoms may occur with a mild allergic reaction?
Diarrhoea and abdominal pain
What are the cardiovascular risks of anaphylaxis?
Coronary artery spasm- ACS caused by rupture of an atherosclerotic plaque in CA caused by release of inflammatory markers
Circulatory collapse due to combination of vasodilation and hypotension
Describe the management of anaphylaxis . Include drug doses
Basic supportive care with A-E primary survey. Raise patients legs and try and remove stimulating cause
Adrenaline- 500 micro grams IM of adrenaline (concentration of 1:1000) repeat after 5 minutes if no improvement
Fluids -IV 500-1000 mL of 0.9% Saline. Stop colloid as this could be causing anaphylaxis
High flow oxygen
IV 10mg chlorphenamine or slow IV
IV 200 mg hydrocortisone or slow IV
ADMIT patient for observation (in case of late reaction) and then perform ELISA testing to identify precipitant
How does adrenaline work?
Acts on beta and alpha adrenergic receptors.
Beta 1- increases the force of myocardial contractions.
Beta 2- bronco dilation AND stabilises mast cell membranes
Alpha- vasoconstriction
What can be used as an alternative to adrenaline for patients taking beta blockers?
Glucagon
What are the two types of fluid?
Crystalloids and colloids
Name 5 crystalloids
Saline, 5% dextrose in water, Hartmann, plasmalyte, hypertonic saline
How do colloids work?
Increase oncotic pressure so reduce the net diffusion of water into ISF increasing intravascular volume
What is 5% dextrose used for?
Hypoglycaemia treatment
What is the advantage of using 0.9% saline?
Isotonic
Few contraindications
What are the advantages and disadvantages of Hartmann solution?
Advantages- isotonic, cheap
Disadvantage- contains potassium therefore not good in hyperkalaemia. Also contains lactate
What is the advantage of plasmalyte?
Acid and base balanced very equally. Very isotonic
What do HEMS give for increased ICP?
Hypertonic (3%) saline
Draws water intravascularly
Superior to mannitol as doesn’t crystallise in cold
Name three synthetic colloid fluids
Gelatins, starchs, mannitol
Why are gelatins are starches not used?
Gelatins can cause anaphylaxis.
Starchs build up in body tissues and take a long time to be excreted by the kidneys
Why is it risky to give someone mannitol?
Head injury may have haemorrhage. Breach in endothelial lining may allow big sugar molecule to enter interstitial space which would increase oncotic pressure increased diffusion of water and further increasing ICP.
What are the difficulties faced with whole blood transfusions?
Hard to get, store and cross match
Why are packed RBCs inferior to whole blood transfusions?
Contain 2,3-DPG which means they have a lower oxygen carrying capacity as preferentially bind to deoxygenated haemoglobin >oxygenated haemoglobin
Disadvantage and advantage of albumin infusion?
Disadvantage- expensive and risk of allergy
Advantage- reduces oedema and need for saline
