21 – Hemostasis Flashcards
Why is hemostasis important? What are some patient concerns?
- Medium for bacterial growth: increased risk of post-op infection
- Inflammation
o Delayed healing
o Adhesions
o Pain - Hemorrhage
o Anemia
o Shock
o Death
What is shock?
- Inadequate oxygen delivery
o Can’t meet cellular metabolic needs
o O2 delivery IS LESS THAN tissue/cell O2 requirements
What are some types of shock?
- Cardiogenic
- Hypovolemic
- Distributive
o Septic, anaphylactic, neurogenic - Hypoxemic
What are some surgeon concerns with hemostasis?
- Visualization
o Iatrogenic trauma
o Inaccurate procedures
o Higher complications - Good surgery=good visibility of target tissue
How can you prevent hemorrhage?
- Good history
- Good physical exam
- Breed (ex. von Willebrand’s disease)
- Baseline blood work
What can you do to assess platelet function?
- Buccal mucosal bleeding time (BMBT)
What can you do to assess coagulation factors?
- Prothrombin time (PT)
- Partial throbmoplastin time (PTT)
When do you check hemostatic factors?
- Liver disease
- Exposure to toxin
- Surgery with major bleeding history
What can the surgeon do to prevent hemostasis?
- Careful planning of approaches (KNOW ANATOMY)
- Ligation or coagulation of vessels before transection
- Gentle and accurate dissection
o Don’t grab or cut unless you can visualize structure
o Minimize primary hemorrhage
Secured ligature on major vessels
- Ligature slips=most COMMON cause of intra and post-op hemorrhage
- Hypotensive during surgery
o Normotensive when awake
What do you not do to approach hemostasis?
- DO NOT DO A BLIND OR FRENZIED ATTEMPT
o further laceration of the vessel
o increased hemorrhage
o damage to surround structures
How should you approach hemostasis?
- You have LOTS of time (ex. with a spay you have at least an hour)
- APPLY PRESSURE!
- Vasoconstriction
- Gather thoughts and ideas
o Assistant to scrub in - Instruments
o Suction
o Gauze
o Hemostats
o Suture
What is key to the success with approaching hemostasis?
- Don’t clamp or ligate if you can’t see
o Potential irreversible damage - Good exposure=good hemostasis
o Extend incision or retract tissue - Pre-op management
o Clip hair wide and drape wide
How much is too much?
- If <10% of total blood volume lost=generally okay
- If >15-20% of total blood volume lost=transfusion and support
How can you calculate blood volume?
- 0.08-0.09 x body weight (kg) = estimated volume in liters
o 80-90mL/kg - Ex. 30kg dog=2.5 L of blood, can safely loss 250mL
How do you estimate blood loss in surgery?
- Photo with percent of saturation and the size of the gauze
Pressure: method of hemostasis
- Slows blood flow
o Clot formation (<5mins) - Dab, don’t wipde
o Wipe will remove established clots - Good enough for SMALL vessels
- Larger vessels require more time (clot formation and vessel constriction)
- If NOT stopping: more definitive treatment or clamp vessel
Clamp vessel: method of hemostasis
- Accurate grip
o Minimize trauma to other tissue - Good exposure is essential
o Good hemostasis
o En - *can enlarge incision to visualize the vessel
What happens when you crush tissue when clamping a vessel?
- Arrest hemorrhage
- Damage vascular wall TO activate physiological clotting mechanisms
o Small low-pressure bleeders
o Normal coagulation factors - Larger vessels
o Temporary hemostasis
o Facilitating ligation or cauterization of vessel
What hemostats do you use for small vessels?
- Halstead mosquito and Kelly forceps
- *curved hemostats facilitate visulaizaiton
What hemostats do you use for tissue bundles and vessels?
- Crile
- Ochsner
- Carmalt
- *curved hemostats facilitates visualization
Application of hemostatic foreceps: small superficial bleeders
- Tip
- Parallel to vessel
- Concave surface facing down and fall lateral to incision
Application of hemostatic forceps: large, deep bleeders
- Jaw
- Perpendicular to vessel
- Concave surface facing up or towards proposed line of transection
What do you do if you can’t stop the bleeding with the hemostats?
- Cautery
- Electrosurgery vs. electrocautery
o Often used interchangeably
Electrosurgery
- High-frequency alternating current to cut, coagulate or ablate tissue
- More complex, larger electrosurgical units (ESU)
Electrocautery
- Heated metal probe to destroy tissue
- Uses a direct current to heat a metal probe that is applied to tissue, causing thermal damage
- Small, battery-operated devices
Electrosurgery: technique
- Pass electrical current through tissue
o Ionic agitation in cells and causes frictional heat in the tissues - *results in coagulation (hemostasis) tissue
- Small vessels
o <1mm artery
o <2mm vein - Monopolar and bipolar
Monopolar electrosurgery
- Current: handpiece to tissue to patient to ground plate to generator
- Ground pad: needs GOOD CONTACT
o Hair needs to be shaved
o Broad contact: otherwise burns may occur
When is monopolar electrosurgery NOT recommended?
- Close to heart
- Close to CNS
Bipolar electrosurgery
- Forceps type of active electrodes
- Current: one tip to tissue between to other tip
- NO ground pad required
- Minimal trauma to other tissues
What do you do if cautery is not working?
- Ligatures and vascular clips
Ligature
- GOLD standard
o >1mm artery
o >2mm vein - Tie end of vessel off
o Sacrifice vessel - Absorbable suture: monocryl or PDS
Single ligature
- Circumferential ligature
- GOLD standard
- Square know + 2
o 4 throws total
Double ligation
- Larger artery/veins
Transfixation ligature
- Prevent slippage
- NOT necessary? (preference)
Vascular clips: basic principles
- Dissect vessel wall
- Vessel diameter: no more than 2/3 and no less than 1/3 of length of clip
- Apply several mm from cut end of vessel
- Artery and vein pair are clipped separately
- *can occlude vessels up to 5mm
What are the advantages of vascular clips?
- Quick
- Apply in locations inaccessible to ligation
What are some disadvantages of vascular clips?
- More frequently dislodged
- Persist in wound
o Absorbable clips are now available - Irritating to load into applicator
o New applicators are easier to use
What are some hemostatic agents (2)?
- Gelfoam
- Surgical
Gelfoam
- Procine gelatin sponge
- Forms gel when wet
- Matrix for clot to form to
- Absorbable: 4-6 weeks
- Possible nidus for infection
Surgical
- Cellulose
- Similar action
