Lecture 8: Principles of hemostasis (Exam 1) Flashcards
Exsanguination on your pathology report =’s what
Equals pilot error
What is hemostasis
A complex process that involves platelet activation & circulating clotting factors
Why is hemostasis important
- Allows appropriate visualization of tissue during the procedure
- Prevents life threatening hemorrhage
How are low pressure hemorrhages from small vessels controlled
- By applying pressure to the bleeding points w/ gauze sponges
- Once a thrombus has formed the sponge should be gently removed to prevent disrupting clots
- Soaking the sponge w/ saline before removal may also help prevent clot disruption
How can hemostatic forceps be used to control bleeding from small vessels
The vessel is grasped & clamped w/ the forceps for several mins until coagulation occurs
How do ligatures help with ligation
- Ligate larger vessels
- Double ligatures are recommended for large vessels (especially arteries)
- Transfixation ligatures may be indicated for larger arteries to prevent the ligature from slipping off the end of the vessel
- Use the smallest suture possible for vessel to improve knot security
Describe circumferential ligature for vascular ligation
- Less likely to bleed than transfixation ligature
- More likely to slip than a transfixation ligature
Describe transfixation ligature for vascular ligation
- Penetrates the lumen of the vessel
- Less likely to slip than a circumferential ligature
- More likely to bleed than a circumferential ligature
When double ligating where should the circumferential ligature be placed
Closer to the heart
Describe double ligation
- For larger vessels particularly arteries
- Circumferential + Transfixation ligature
- Transfixation is more secure
- Circumferential is less likely to bleed & is closer to the heart
Why are ligature(s) placed
To ensure the bleeding is stopped
What is the second through in a transfixation ligature for vascular ligation
A square throw (b/c its more secure)
Why should a surgeons throw not be place in the transfixation ligature
Due to the extra suture material this knot cannot easily be tightened & can withstand only a slight strain on the suture loop
List some topical hemostatic agents
- Bone wax
- Gelatin based hemostatic product
- Cellulose based hemostatic products
Describe bone wax
- sterile mixture of beeswax, paraffin, & isopropyl palmitate
- Pressed into bleeding channels of bone to control hemorrhage through a tamponade effect
- Used sparingly & w/ caution b/c it is nonabsorbable
Why should relating products not be used in closure of skin incisions
May interfere w/ healing
Describe gel foam
- Absorbable gelatin sponge that can be used to control hemorrhage
- Provides a physical matrix that initiates clotting through contact activation
- When applied the gel foam swells & exerts pressure on the wound as it absorbs many times its weight in blood
- Absorption occurs in 4 to 6 weeks
- The sponge should not be left in infected sites in areas w/ a high risk of infection or in confined places as it may exert unnecessary pressure on neighboring vital structures
Describe a punch biopsy
- Haemostatic foam
- 6 mm minimum
What is surgicel
- Absorbable cellulose sponge that is more like a 4x4 gauze in appearance
- Oxidized regenerated cellulose
- Substrate for clot formation
- Can be cut to the desired size & placed on an area of hemorrhage
- Removal is recommended
- Not activated by tissue fluids other than blood
Describe electrocautery
- Coagulates small vessels or cuts tissue by using heat generated by direct electric current into a metal wire or probe
- Electrical current doesn’t enter the pxs body
Define electrosurgery
- Refers to generating heat inside the tissue using an alternating electric current that passes through the tissue creating a circuit
- Widely used for hemostasis for vessels less than 1.5 to 2 mm diameter ( larger vessels should be addressed by other means)
What occurs on the “cut setting” for electrosurgery
- Constant waveform occurs
- Produces less heat & creates a coagulum rather than vaporizing tissue
What can be used to perform electrosurgery
Monopolar or bipolar devices
What is monopolar electrosurgery
- Most commonly used method of electrosurgery
- Involves the flow of current from an active electrode (handpicece) through the patient to a ground plate
- Concentrates the current density increasing the temperature of the contact tissue & causing coagulation or tissue vaporization
- Larger surface area of the ground plate reduces the current density so that min tissue heating occurs as the circuit is completed
What happens if an adequate low impedance ground pad is not present
The circuit will inadvertently use alternate paths to ground & will burn the px
How are burns prevent w/ monopolar electrosurgery
- A small ground plate or an alternate path to ground can easily produce a severe burn
- To reduce the risk of a burn use a large pad placed in good contact on a well vascularized area of tissue that is close to the operative site
- Keep electrodes clean & free of eschar will enhance performance by maintaining lower resistance w/in the circuit
- Towels dampened w/ water or conduction gel
- Px return electrodes
- Some models deactivate if the monitor shows impedance levels
What is needed for monopolar electrosurgery
- Field must be relatively dry & the electrode kept clean & free of debris
- Direct contact of the electrode w/ the tissue produces lower heat sufficient to coagulate
- Use of the arc btw/ the electrode & tissue produces higher heat & consequently a cutting or vaporization action
- The standard flat tipped electrode is designed to create an eschar or coagulum directly on tissue
What does indirect contact of monopolar electrosurgery involve
- Touching the electrode to an instrument (hemostat or forceps) that has been applied to the bleed vessel
- Allows more precise application of energy & effective coagulation
Describe bipolar electrosurgery
- Involves forcep like hand piece
- Current passes from one tip of the forceps to the opposite tip through the tissue being held btw/ the tips
- Tips must be held approx 1 mm apart for a current to be generated
- Ground plate or pad is not necessary
- Used when precise coagulation is necessary & to prevent damage to adjacent structures such as in spinal surgery, thyroidectomy, or ophthalmic procedures
What is radiosurgery
- Generators & handpieces are similar to standard electrosurgery units except that the energy is generated by a low temp high freq current
- The radio wave passes from an active electrode in the handpiece to a passive electrode beneath or near the px
- Tissue resistance to the radio waves causes an ionic agitation in the cells @ the tip of the active electrode
Describe the carbon dioxide laser
- Most widely used laser in small animal surgery
- Wavelength of 10,600 nm (highly & selectively absorbed by water)
- Tissue vaporization occurs as this light energy is absorbed by water into the soft tissues
- Penetration into tissue is shallow & precise w/ little heat dissipated to surrounding tissues
What are the proposed advantages of CO2 lasers
- Less bleeding
- Less pain
- Less tissue swelling
- Decreased risk of infection
What is vessel sealing used for
Utilized for hemostasis in laparoscopic & thoracoscopic surgery as well as open abdominal procedures & soft palate resection
