7. Haemostasis

1. Definition

• Haemostasis → stopping of bleeding
• Spontaneous (physiological) → the body's own mechanisms
• Artificial (surgical) → temporary or definitive methods used by the doctor

2. Classification of bleeding

By vessel

• Arterial → bright red, pulsatile jet
• Venous → dark red, steady flow; risk of air embolism in neck veins
• Capillary → oozing from the whole surface
• Parenchymal → liver, spleen, kidney; no spontaneous stop

By direction

• External → onto the body surface
• Internal → into a cavity (haemothorax, haemoperitoneum) or tissue (haematoma)
• Occult → found only by tests (faecal occult blood)

By time

• Primary → at the time of injury or operation
• Reactionary → within 24 h; slipped ligature, rising blood pressure
• Secondary → 7–14 days; infection eroding a vessel

By volume: American College of Surgeons classes of haemorrhage

1. Class I → < 15% blood volume (< 750 mL); minimal signs
2. Class II → 15–30% (750–1500 mL); tachycardia, narrowed pulse pressure
3. Class III → 30–40% (1500–2000 mL); hypotension, confusion, oliguria
4. Class IV → > 40% (> 2000 mL); life-threatening, marked hypotension

3. Spontaneous haemostasis

1. Vascular phase → reflex vasoconstriction, retraction of the cut vessel ends
2. Platelet phase → adhesion to collagen (von Willebrand factor), activation, aggregation → white platelet plug
3. Coagulation phase → cascade activates thrombin; fibrinogen → fibrin; red thrombus
4. Clot retraction → seals the defect
5. Fibrinolysis → plasmin removes the clot as the vessel heals
6. Effective → capillaries, small veins and arteries
7. Ineffective → large arteries, parenchymal organs, coagulopathy, anticoagulants

4. Artificial haemostasis: temporary

• Elevation of the limb
• Direct pressure on the wound → first measure in all external bleeding
• Pressure dressing → venous and capillary bleeding
• Digital pressure on the artery against bone, proximal to the wound:
  • Common carotid → transverse process of C6 (carotid tubercle)
  • Subclavian → first rib
  • Brachial → humerus, medial bicipital groove
  • Femoral → superior pubic ramus, mid-inguinal point
• Maximal joint flexion → elbow, knee
• Tourniquet → limb arterial bleeding not controlled by pressure
  • Applied proximal to the wound, over one bone
  • Record the time of application
  • Maximum 2 h
  • Too loose → venous congestion, more bleeding
• Haemostatic clamp in the wound
• Wound packing (tamponade) → haemostatic gauze
• Balloon tamponade → Sengstaken-Blakemore tube, Foley catheter in a wound
• Resuscitative endovascular balloon occlusion of the aorta (REBOA)
• Temporary vascular shunt

5. Artificial haemostasis: definitive

Mechanical

• Ligation of the vessel in the wound
• Transfixion (suture) ligation → large vessels, slip-proof
• Ligation in continuity (at a distance) → secondary bleeding in infected wounds
• Clips, staplers
• Vascular suture or repair, patch, graft → restores blood flow in main arteries
• Packing of the liver → damage control surgery
• Organ removal → splenectomy, nephrectomy

Thermal

• Diathermy → monopolar, bipolar
• Ultrasonic and advanced bipolar energy devices
• Argon plasma coagulation, laser
• Hot saline packs → diffuse oozing
• Cold → cryotherapy, ice packs

Chemical and pharmacological

• Local:
  • Adrenaline infiltration → vasoconstriction
  • Haemostatic agents → oxidised cellulose, gelatin sponge, collagen
  • Fibrin sealant, thrombin
  • Bone wax → bone bleeding
• Systemic:
  • Tranexamic acid → inhibits fibrinolysis; 1 g within 3 h of injury
  • Vitamin K, protamine (heparin reversal)
  • Prothrombin complex concentrate → warfarin reversal
  • Desmopressin

Biological

• Muscle, omentum, fat → placed on a bleeding surface
• Blood products → fresh frozen plasma, platelets, cryoprecipitate

Endovascular

• Embolisation → coils, particles, glue
• Stent graft

6. Clinical and surgical significance

• External limb bleeding → direct pressure first, tourniquet if it fails
• Massive haemorrhage → damage control resuscitation:
  • Permissive hypotension
  • Early blood products in 1:1:1 ratio
  • Tranexamic acid
  • Avoid the lethal triad: hypothermia, acidosis, coagulopathy