Surgical Bleeding and Hemostasis

What happens during vasoconstriction?

injured endothelial cellular membrane releases phospholipids activation arachidonic acid and metabolites that mediate vascular tone and permeability; last 5-10 minutes

What happens during vasoconstriction that improves platelet activation?

lowers O₂ and pH

What happens during platelet activation and clot formation?

exposure to collagen, vWF, and TF will activate platelets and the clotting cascade

What is the percentage of blood loss that constitutes hemorrhagic shock?

25-35%

What percentage of blood loss is a risk of death?

>35-40%

What are the indications for whole blood transfusion?

PCV <20% with acute loss, decreasing total solids (<5), increasing lactate, etc

Why might the PCV not reflex accurate blood loss for the first 24 hours?

splenic contraction

During a surgery under general anesthesia, what percentage of blood will require transfusion?

>30% due to loss of oxygen carrying capacity

What is used in blood collection for the storage of blood to be transfused?

citrate-phosphate-dextrose-adenine (CPDA) to prevent coagulation

What are cats blood types?

type A, B, and AB

What are dogs blood types?

dog erythrocyte antigen system (DEA)

What are horses blood types?

8 major blood types and 30 subfactors

What are the most immunogenic horse blood types?

Aa and Qa

Why should donkeys and mules not be used as donors?

“donkey factor” causes an allergic reaction in horses

What is the major crossmatch testing?

recipients serum with donors RBCs

What is the minor crossmatch testing?

donors serum with recipients RBCs

How should you monitor for a transfusion reaction?

assess every 5 minutes for the first 15-20 and every 15 minutes until completed; rectal temp, heart rate, respiratory rate, etc

How do you calculate acute blood loss volume?

body weight (kg) x 0.08 × 0.30; 30% for shock in horse and start with transfusion of 50% of estimated loss

How do you manage a hemorrhage of a small vessel?

direct pressure with moistened gauze and apply mosquito hemostatic forceps

How do you manage a hemorrhage of a large vessel?

ligature with suture or double ligate larger arteries

What is a transfixation ligature?

take one bite into vessel then circle and close

What is a circumferential ligature?

simply tied around vessel

Where does the transfixation and the circumferential ligatures go?

more secure suture (transfixation) goes closer to your cut, circumferential would go under/above transfixation at that point (farthest from your cut)

What is bone wax?

mixture of beeswax and paraffin that is nonabsorbable, may interfere with bacterial clearance

What is gelfoam?

absorbable gelatin sponge, physical matrix that initiates clotting through contact activation, swells and applies pressure by absorbing, absorbed within 4-6 weeks, increased risk of infection

Why is gelfoam not for skin incision closure?

may impede healing

What is electrocautery?

coagulates small vessels by using heat and generated by direct (electrons flowing in one direction) electric current into a metal wire or probe; current is used to heat a handheld element, which is then applied to tissue

What is electrosurgery?

generates heat inside the tissue using a high-frequency (radiofrequency current) alternating electric current that passes through the tissue creating a circuit

In what kind of electrical hemostasis does the electric current not enter the patient’s body?

electrocautery

What color is assigned to cutting on electrosurgery?

yellow

What color is assigned to coagulation on electrosurgery?

blue

What is the cut feature of the electrosurgery?

constant waveform to vaporize tissue, high frequency current with low voltage, current is delivered 100% of the work cycle

What is the coagulation feature of the electrosurgery?

intermittent waveform less heat creating a coagulum, low frequency and high voltage, current is delivered for limited time (6%) of the work cycle

What are the electrosurgery blend modes?

modifies the waveform’s duty cycle, the % of time the current is on vs off will allow the tissue time to cool between bursts of energy; created to have more efficient coagulation without increase tissue damage

What is monopolar electrosurgery?

most commonly used method, flow of current from an active electrode (handpiece) through the patient to a ground (diversion) plate

What is the direct application of monopolar electrosurgery?

direct application of handpiece to tissue/vessel

What is the indirect application of monopolar electrosurgery?

handpiece contacts hemostatic forceps applied to tissue/vessel; allows for more precise application of energy and effective coagulation

What is bipolar electrosurgery?

utilizes a forceps-like handpiece, current passes from one tip of the forceps to the opposite tip through the tissue being held between the two, no ground plate is necessary

What is a carbon dioxide laser?

non-contact, shallow yet precise tissue penetration with little heat dissipated to surrounding tissues, highly and selectively absorbed by water

What is a vessel sealing device (ligasure)?

electrothermal, feedback-controlled bipolar vessel sealing system, fuses collagen and elastin of the vessel wall to achieve hemostasis, permanently seals blood vessels up to 7 mm in diameter

What are some systemic therapies for hemorrhage?

aminocaproic acid, formalin, yunnan baiyao

What does aminocaproic acid do?

inhibits fibrinoloysis by binding plasminogen activator & enhancing antiplasmin activity

What does formalin acid do?

proposed to enhance endothelial or platelet activation but does not influence hemostatic

What does yunnan baiyao acid do?

chinese herbal medication, enhanced expression of surface glycoproteins on platelet