Revision - Blood Products & Head Injuries Flashcards
What does a Group and Save involve?
This determines the patient’s blood group (ABO and RhD) and screens the blood for any atypical antibodies.
No blood is issued.
When is a G&S recommended?
If blood loss is not anticipated, but blood may be required should there be greater blood loss than expected.
What is a X-match involve?
Involves physically mixing the patient’s blood with the donor’s blood, in order to see if any immune reaction takes places.
Blood is issued.
What must be done first, XM or G&S?
G&S
When is a XM done?
If blood loss is anticipated
What stages are involved in requesting blood products?
1) Using 3 points of patient identification e.g. name, DOB, and patient number.
2) Consent the patient appropriately.
3) Labeling the bottle at the bedside.
4) Completing the transfusion request form at the bedside.
What is irradiated blood?
Blood that has been treated with radiation to prevent Transfusion-Associated Graft-versus-Host Disease (TA-GvHD).
What disease do irradiated blood products reduce the risk of?
graft-versus-host-disease in at risk populations
What is graft vs host disease (GVHD)?
A multi-system complication of allogeneic bone marrow transplantation.
Less frequently, it may also occur following solid organ transplantation or transfusion in immunocompromised patients.
What happens in GVHD?
T cells in the donor tissue (the graft) mount an immune response towards recipient (host) cells.
NOT to be confused with transfusion rejection (in which recipient immune cells activate an immune response toward the donor tissue).
What criteria is used in diagnosis of GVHD?
Billingham criteria
What 3 conditions are required for the diagnosis of GVHD?
1) The transplanted tissue contains immunologically functioning cells
2) The recipient and donor are immunologically different
3) The recipient is immunocompromised
What can be given as prophylaxis to reduce risk of GVHD?
Calcineurin inhibitors
Which populations should receive irradiated blood?
1) Those receiving blood from first or second-degree family members
2) Patients with Hodgkin’s Lymphoma
3) Recent haematpoietic stem cell(HSC) transplants
4) After Anti-Thymocyte Globulin (ATG) or Alemtuzumab therapy
5) Those receiving purine analogues (e.g. fludarabine) as chemotherapy
6) Intra-uterine transfusions
How should blood products be prescribed if a patient requires more than one unit of blood?
Each unit should be prescribed individually
Whilst the patient is receiving the blood transfusion, how often should observations be carried out?
1) before transfusion starts
2) 15-20 minutes after it has started
3) at 1 hour
4) at completion
Indications for transfusion of packed red cells?
1) acute blood loss
2) symptomatic anaemia
3) chronic anaemia where the Hb ≤70g/L (or ≤100g/L in those with CVD)
Over what period should packed red cells be administered?
2-4h
How soon after coming out of the store should packed red cells be administered?
within 4 hours
1 unit of blood should increase a patient’s haemoglobin by how much?
Approx 10g/L
What is the major constituent of fresh frozen plasma (FFP)?
Clotting factors (also albumin & immunoglobulin)
Give some indications for FFP
1) DIC
2) Any haemorrhage 2ary to liver disease
3) All massive haemorrhages (typically given after the 2nd unit of packed red cells)
Over what time period is FFP typically administered?
30 mins
What are the major constituents in cryoprecipitate?
- fibrinogen
- vWF
- factor VIII
- fibronectin
Indications for cryoprecipitate?
1) DIC with fibrinogen <1g/L
2) vWD
3) massive haemorrhage
What happens in factor V Leiden?
Mutation in factor V results in resisted degradation by protein C –> increases risk of clotting.
Duration over which platelets are admistered?
30 mins
Indications for the transfusion of platelets?
1) Haemorrhagic shock in a trauma patient
2) Profound thrombocytopenia (<20 x 109/L; normal range 150 – 400)
3) Bleeding with thrombocytopenia
4) Pre-operative platelet level <50 x 109/L
1 ATD (adult therapeutic dose) of platelets should increase platelet levels by how much?
Approx 20-40 x 10^9/L.
Which blood products must be crossmatched?
1) packed red cells
2) cryoprecipitate
3) whole blood
4) FFP
PCC or FPP in reversal of warfarin?
PCC
Which blood product can be ABO incompatible in adults?
Platelets
Who may cell saver devices be useful in?
They may be acceptable to Jehovah’s witnesses.
What is the threshold for transfusion of red cells in:
a) patients with ACS
b) patients without ACS
a) 80 g/L
b) 70 g/L
What are irradiated blood products depleted of?
T lymphocytes
What blood product can be used for the emergency reversal of anticoagulation in patients with either severe bleeding or a head injury with suspected intracerebral haemorrhage?
PCC
How can the risk of clotting impairment in a packed red cell transfusion be reduced?
FFP and platelets should be administered concurrently.
(typically done for patients receiving more than 4 units RBCs)
What are the 2 main electrolyte abnormalities that can occur in blood transfusions?
1) hyperkalaemia
2) hypocalcaemia
What can confirm the diagnosis of an acute haemolytic reaction?
A positive Direct Antiglobulin Test (DAT) will confirm the diagnosis.
What happens in TRALI?
Non-cardiogenic pulmonary oedema thought to be secondary to increased vascular permeability caused by host neutrophils that become activated by substances in donated blood.
Which blood product tranfusion is most likely to cause a non-haemolytic febrile reaction?
Platelet transfusion
What is anaphylaxis caused by a blood transfusion thought to be the result of?
Can be caused by patients with IgA deficiency who have anti-IgA antibodies.
When is GvHD most common?
It is most common in the transfusion of non-irradiated blood products to an immunocompromised recipient.
Clinical features of GvHD?
- fever
- skin involvement (ranging from macropapular rash to toxic epidermal necrolysis)
- diarrhoea
- vomiting
What blood product should be ordered prior to surgery in operations where there is a definite chance of transfusion?
Cross match 4-6 units depending on local protocols.
1st line imaging following a head injury?
CT without contrast
1st line imaging for diffuse axonal injury detection?
MRI
Triad of symptoms in Cushing’s reflex (raised ICP)?
1) Bradycardia
2) Irregular respiration
3) HTN with widened pulse pressure
Does the Cushing’s reflex often occur early or late?
often occurs late and is usually a pre terminal event
What is the most common cause of SAH?
Ruptured cerebral (berry) aneurysm i.e. spontaneous
What conditions are associated with berry aneurysms?
1) HTN
2) ADPKD
3) Ehlers-Danlos
4) Coarctation of the aorta
In which time frame is a non-contrast head CT sufficient to rule out SAH in most patients?
Within 6 hours
If CT head is done more than 6 hours after symptom onset in SAH and is normal, what is next step?
Do a LP at 12 hours post-onset
Complications of SAH?
1) rebleeding
2) hydrocephalus
3) SIADH –> hyponatraemia
4) vasospasm
5) seizures
How does an intracerebral haemorrhage present?
Very similarly to ischaemic stroke
What investigation is key in differentiating between intracerebrael haemorrhage and ischaemic stroke?
Non-contrast head CT
What are the 2 surgical options for treating an extradural or subdural haematoma?
1) Craniotomy (open surgery by removing a section of the skull)
2) Burr holes (small holes drilled in the skull to drain the blood)
Head injury vs traumatic brain injury?
Head Injury = a patient who has sustained any form of trauma to the head, regardless of whether they have any symptoms of neurological damage
Traumatic Brain Injury = evidence of damage to the brain as a result from trauma to the head, represented with a reduced Glasgow Coma Scale or presence of a focal neurological deficit
Any patients presenting to A&E with evidence of head injury should be examined how quickly?
Within 15 minutes of arrival
Palsy to which cranial nerve causes a ‘down and out’ pupil?
CN III (oculomotor)
What is cerebral perfusion pressure (CPP)?
The pressure driving blood through the brain tissue, allowing the delivery of oxygen and nutrients.
How can CPP be calculated?
CPP = mean arterial pressure (MAP) - ICP
How will a rise in ICP affect CPP?
Will reduce it.
If CPP drops too low for a significant amount of time, ischaemia occurs.
What will the cerebellar tonsils herniate through in raised ICP?
The foramen magnum - ‘coning’ –> compression of brainstem
What will the uncus of the temporal lobe herniate through in raised ICP?
Tentorial notch
Effect of herniation of the uncus of the temporal lobe through the tentorial notch?
Compression of CN III –> “blown pupil” that is often assessed for in TBI patients.
What are some factors that may contribute to 2ary brain injury (indirect damage to brain tissue that that occurs after the primary insult)?
1) Hypoxia & hypercapnia
2) Hypovolaemia & hypotension
3) Cerebral oedema & raised ICP
4) Expanding haematoma
5) Hypoglycaemia or hyperglycaemia
6) Increased metabolic demand (e.g. hyperthermia or seizures)
How many times can administration of fluid boluses be repeated for hypovolaemia in TBI?
Up to four times (e.g. 2000ml or 1000ml in patients at increased risk of fluid overload), reassessing the patient each time.
