Haemostasis Flashcards
How does shock occur?
Reduced O2 Perfusion
What are the clinical skills of shock?
- Sinus tachycardia or bradycardia
- Hypotension, poor pulse quality
- Cold extremities (hypothermia)
- Pallor
- Biochemistry changes (renal, lactate?
What is the main approach to intra-operative haemorrhage?
Recognise and address blood loss
* Rule out, identify source of bleeding
* Suture malfunction/deficiency
* Occult haemorrhage (unknown/unexplored/distant to surgical field)
* Accidental damage or collateral damage during surgery
* Damage after surgery (post operative haemorrhage)
* Restore haemostasis
* Reverse hypothermia, shock and other complications
* Monitor
* Stability of coagulation
* New or ongoing blood loss
* Complications
How do you quantify blood loss?
Blood losses should be estimated or measured during surgery
* Swabs contain standard amounts of fluid dependent upon size (6, 8 or 10 mls)
* Weigh swabs
* Compare dry swab with saturated swab
* Blood essentially water; 1g=1ml
* Loss onto floor, drapes should be estimated
* Suctioned blood should be measured and recorded
* Record volume of flush used and remaining and calculate blood loss
What is the function of haemostatic forceps?
- They crush tissue
- Ratchet allows them to be left in position
- Temporarily arrest haemorrhage
- damage the vascular wall to activate the clotting mechanism
What is electrocautery?
Where heat is applied to tissue (e.g disbudding)
What is Electrosurgery/ Electrocoagulation?
electrical current passes from the metal tip to the blood vessel
* Heat produced in tissue itself and converted into thermal energy to seal vessel
* Can use for incision but care with thermal necrosis delaying healing
* Works best for vessels 2mm or less
What is monopolar electrosurgery?
Ground plate lies contact and beneath the patient.
* Current flows through electrode (handpiece) through patient to ground plate
* If contact not good can cause burns
* Cut and coagulate possible
* Requires dry surgical field
* Bipolar more precise
What is radiosurgery?
Similar to electrosurgery
* Cut and coagulation
* Uses high-frequency radio waves
* Patient is not part of the circuit
* Plate is not grounding and doesn’t need to be in contact with skin
What is a hotblade?
- Bipolar vessel sealer
- No automatic adjustment or cutting
- Adequacy of coagulation determined visually
- Surgeon activates knife
- ‘Individual use’ but can be sterilised by ethylene
oxide - Cheaper than the others
What are the two types of harmonic scalpel?
- Ultrasonic energy
- Lasers
How does adrenaline help seal wounds?
- Small superficial wounds
- Vasoconstriction may reduce blood flow to allow clot formation
- 1:1000 to 1: 10000
- Diffuse bleed – intranasal/intraoral
- Can have systemic effects
- Local ischaemia
Name 5 topical haemostatic agents
- Gelfoam-Spongostan (absorbable haemostatic gelatin)
- Lyostypt (collagen sponge)
- Surgicell –surgicell fibrillar (oxidised regenerated cellulose)
- Surgiflo (haemostatic gelatin matrix)-reconstituted with saline
- Bone wax
When might bone wax be used?
Used in neuro-surgery, blocks the blood vessels
Name 4 active topical haemostatic agents
- Autogenous muscle tissue
- Thrombin
- Topical fibrin haemostatic sealant
What is the function of transexamic acid?
- synthetic analogue of lycine
- binds plasminogen and stops the conversion to plasmin and fibrin breakdown
- duration of the thrombus/ clot is prolonged
- Used in grey hounds
What is the function of desmopressin?
- Increases expression of von Willebrand’s factor and factor VIII
- Reduces BMBT in vWD- affected Dobermanns
- Does not work in type III vWD
- Dilute and give 30 minutes before surgery
What is the function of a tourniquet?
Reduce the amount of arterial blood reaching the distal limb
* Causes ischaemic and anaerobic respiration of tissues lactic acid accumulation can result in pain
How long should a tourniquet be applied for?
For most purposes the tourniquet should be applied for less than 2 hours
What is an esmarch bandage used for?
For lower limb surgery
How would you use an esmarch bandage?
Exsanguination of the limb
* Useful technique for digital amputation in several species as well as lower limb
surgery in the horse.
* A rubber (Esmarch) bandage is tightly applied to the limb working from the
distal towards the proximal limb and blood prevented from reperfusing the
limb by application of a tourniquet
How does post-operative haemorrhage occur?
Often result of ineffective haemostasis
* Physiological or surgical
* Slipped ligatures, necrosis, suppuration of ligated or cauterised vessels
* Hypotension during surgery may prevent detection of vascular injury or ineffective
haemostasis resulting in delayed haemorrhage upon restoration of normal BP post op
* Poor secondary haemostatic plug formation common with coagulation deficiencies
How can you use pressure to prevent blood flow?
Abdominal wraps/pressure bandage
* Temporary use in haemoabdomen
* Care with impeding ventilation
* Reduce perfusion to abdominal organs
* Limit/restrict movement
