Blood loss and transfusions Flashcards
Causes of blood loss?
Whole blood loss
Reduced RBC production - anaemia of chronic disease, bone marrow suppression, not common: CRF, neoplasia, iron deficiency anaemia, EIA
Red cell loss - haemolytic disease
When may blood products be required?
Blood loss
Anticipated blood loss
RBC production issues
Hb binding issues
Colloidal support - e.g. PLE/PLN
Failure of passive transfer
Platelet/factor deficiencies - uncommon in horses
Sepsis/SIRS/endotoxaemia - can benefit from plasma tranfusion
Types of haemorrhage?
Internal vs external
Controlled cs uncontrolled
Mild, moderate, severe
Common reasons for external haemorrhage?
Guttural pouch mycosis
Surgery
Laceration
EIPH
Where can internal haemorrhage occur?
Abdomen
Thorax
Broad ligament
Uterus
Intestinal lumen - conditions causing erosion
How much blood volume loss is fatal?
Around 40%
What does ‘shock mean’?
Inadequate perfusion of tissues, leading to decreased oxygen delivery
What are hypovolaemic shock and haemorrhagic shock?
Hypovolaemic shock = decrease in intravascular volume, to the point of cardiovascular collapse
Haemorrhagic shock = subset of hypovolaemic shock, blood loss causing the hypovolaemia
What happens with hypovolaemic and haemorrhagic shock?
Haemodynamic instability, causing many knock on effects
Decreased perfusion and oxygen delivery to tissues -> cellular hypoxia -> mitochondria switch to less efficient anaerobic metabolism -> organ damage -> death
Loss of volume causes horse to compensate by increasing HR and contractility in attempt to maintain CO
Also activation of sympathetic nervous system, to cause peripheral vasoconstriction to try to centralise blood volume and get blood to critical organs - good for heart and brain, but leads to other tissues being further depleted of oxygen, more lactate production, worsening acidosis
Diastolic ventricular filling will decline as the blood volume decreases, CO will reduce, systolic BP will drop
Also can get trauma induced coagulopathy if haemorrhagic
What is the lethal triad of trauma in humans, which all happen during haemorrhagic shock?
Acidosis
Trauma induced coagulopathy
Hypothermia
Clinical signs associated with haemorrhage?
Dull or agitated/distressed, or collapse when sever
Pale mm, prolonged CRT (peripheral vasoconstriction)
Thready peripheral pulses (CO reducing, peripheral vasoconstriction)
Tachycardia - trying to maintain CO
Tachypnoea - horse is trying to oxygenate tissues, hypoxic respiratory drive, also trying to compensate for metabolic acidosis by blowing off CO2
Cold extremities
How to assess a blood loss patient?
Assess cardiovascular function to gauge perfusion:
- Palpate peripheral arteries
- MM colour
- Extremities - ears, legs
HR - keep checking so not just initial vet stress if increased
RR
Anxious/obtunded/weak
Colic
Lactate - very useful gives idea of global oxygen delivery
PCT/TP unreliable - useful to get baseline, but be aware takes few hrs for fluid shifts to occur
Clotting - not always easy to test, often will be normal but may lose factors over time
TEG/ROTEM - not many practices have immediately avilable, more advanced for clotting
How to control haemorrhage?
Compression if able to - esp distal limbs with compression bandage
Topical haemostatic agents - Chitosan, absorbable gelatin powder/sponge, collagen sponge, fibrin sealants, ‘Celox veterinary’
Surgical control if can - e.g. lacerated neurovascular bundle block the foot and then haemostats on end of artery if can
Immediate supportive for for haemorrhage, other than controlling haemorrhage?
Transport? Difficult as many horses will get stressed, but often necessary evil for mod-severe haemorrhage e.g. mare bleeding into braod ligament after foaling better to refer sooner rather than later
Reduce stress - keep companions close etc, keep as calm as possible
Baseline bloods - lactate, PCV, TP
IV access? Sensible as if haemorrhage is ongoing becomes increasingly difficult to get access
Oxygen?
Do not drain haemorrhage from body cavities - better to leave as lots of it will be absorbed (only time to consider draining would be if resp distress which is rare in horses), in theory if do drain and do it sterile can poss readminister to patient (ideally run haematology on it first and give through filter giving set if frank blood, whilst if more sanguinous effusion then less appropriate)
ACP? Some people give to reduce BP to help clotting and to not disrupt formed clots, but risk syncope so avoid if med-severe haemorrhage, esp as long lasting effects and no antagonist
Should you use ACP for haemorrhaging horse?
Some people give to reduce BP to help clotting and to not disrupt formed clots, but risk syncope so avoid if med-severe haemorrhage, esp as long lasting effects and no antagonist
Should you drain haemorrhage from body cavities in horses?
Generally no - better to leave as lots of it will be absorbed
Only time to consider draining would be if resp distress which is rare in horses)
In theory if do drain and do it sterile can poss readminister to patient (ideally run haematology on it first and give through filter giving set if frank blood, whilst if more sanguinous effusion then less appropriate)
Pro-coagulants for haemorrhaging patient?
= promote clot formation
Etamsylate - licensed haemostatic agent, improves platelet adhesiveness and causes some vasoconstriction, limited veterinary evidence, cheap, IV or IM
IV formalin - don’t use it, no evidence to support its use, evdience to suggest can cause toxicity and organ damage
Yunnan Baiyao - chinese herbal medicine, limited evidence it’s of any use
Anti-fibrinolytics for haemorrhaging patient?
= Reduce clot lysis so ‘stabilise clot’ and inhibit it breaking down once clot has formed
Synthetic lysin analogues - inhibit plasminogen activator, decrease plasmin formation
- Epsilon aminocaproic acid
- Tranexamic acid 5mg/kg BID - use pre and peri-op in humans with haemorrhage, some evidence
Serine protease inhibitors (aprotinin) - directly inhibit plasmin activity
Oxygen delivery for haemorrhaging patient?
Can help increase PaO2
Practicalities of administration - can use nasal cannulas, but not always tolerated (and don’t want to cause stress)
Decision making for whether fluid therapy is required after blood loss?
Consider controlled vs uncontrolled haemorrhage,circulating volume, blood pressure, oxygen delivery
In mild blood loss (<15%), generally no fluids required
Around 15% loss - could likely benefit from some help to restore circulating volume and blood pressure (IV crystalloids)
15-25% loss - may also benefit from synthetic colloids, monitor PCV, poss whole blood
25% + - now definitely need help with oxygen carrying capacity = whole blood
Note - yes the crystalloids will dilute the RBCs and clotting factors, but it will improve the circulatory volume and delivery to tissues
What fluids to give in a case of uncontrolled haemorrhage? And what to monitor?
Start with Hartmann’s: 2-3ml/kg/hour (maintenance) - aim is to help circulating volume, without increasing BP and dislodging clots
Avoid hypertonic saline
?Blood products - if had loads of blood then could start giving straight away, but in horses we have limited supply, e.g. if only have 6L of blood no point giving it whilst haemorrhage uncontrolled as will just end up on the floor, hold off until haemorrhage controlled, discuss PTS if severe haemorrhage
Lactate monitoring
Monitor clinical parameters
^If worsening, prompts discussion about prognosis
How to calculate how much blood to give after blood loss?
1/4 to 1/2 of the volume lost (or if very small patient can replace more)
Can base it on PCV (2ml/kg of donor blood will raise recipient PCV by 1%)
Give what you have…
Or:
Ml blood required = recipient blood volume (ml) x ((desired PCV 30% - recipient PCV)/donor PCV)) - often will tell you you need lots of L, but may not have this much
