108.Vascular Sx Flashcards
3 layers of an artery
TUNICS1. tunica externa or tunica adventitia (CT, fibroblasts, collagen)—important to resect to avoid inadvertent infolding into the lumen2. tunica media (smooth muscle, elastic)3. tunica intima (endothelial cells, fragile)** veins have the same layers but thinner media/muscle and no contraction and have valves
arteries are found in all locations EXCEPT
hairepidermiscorneacartilagenails
which veins carry oxygenated blood
pulmonary veins (bring oxygenated blood from lungs to left side of heart)umbilical vein carries oxygenated blood from dam to fetus
another name for a double loop around a vessel for retraction
Potts double loopused for retraction and prevent hemorrhage in case of accidental vessel trauma
ideal suture for vascular surgery
–swaged small needle/ round, circular taper point needle end–3-0 to 8-0suture with excellent knot holding capability and ease of handling with minimal inflammation–nylon, polypropylene (both monofilament)–small multifilament can be used when passed thru bone wax/mineral oil
concern with synthetic grafts in vascular surgery
infectionthrombogenicex textile graft–Dacron, nontextile graft–PTFE
characteristics of PTFE
polytetrafluoroethylene–hydrophobic (resists water, creates good seal)–biologically inert—relative thromboresistent–ductile and easy to use–cut to shape/length–strong and durable
options to locate a vessel
- palpation2. doppler color flow US
what are the normal “marking” of adventitia of the perivascular sheath
the adventitial surface of the artery is marked by a characteristic vaso vasorum pattern perfusing vessels “white line” seen which facilitates plane of dissection
if local anticoagulation is elected, what protocol is recommended
ice cold 2% lidocaine, heparin, 0.9% saline to flush the isolated segment at the arteriotomy/venotomy sitealso prior to closure, remove proximal inflow occlusion device to allow any air or clots to escape before placing final suturesMAKE sure to remove adventita to avoid infolding and potential thrombus formation or occlusion of lumen
indications for systemic anticoagulation
—cardiopulmonary bypass—renal transplant–placement of vascular autogenous or prosthetics–adrenalectomy for adrenocortical tumorseither heparin given IV or heparin placed in plasma given before surgery and either IV, SQ post op if indicatedusually monitored with ACT (normal is < 150 secs but goal is 480sec for heparinization)
recommendation for vessels that may be prone to recanalization
single transfixation ligature btwn two circumferential ligatures
options for venotomy/arteriotomy incision
—longitudinal–good exposure, easily manipulation but may get narrow with closure–transverse–recommended in vessels smaller than 4 mm; incision should NOT extend 180 degrees of vessel circumference
Kunlin’s technique for venotomy/arteriotomy closure
double swaged needle suturestarting the pattern with a horizontal mattress suture on each end
three types of vascular anastomoses
- end to end 2. side to side (not commonly done)3. end to side
methods for end to end anastomosis
- running continuous2. beveled or split edges3. triangulationavoid purse string effect with different continuous lines and allow release of proximal inflow occlusion to allow flow on incision
method to create a hemodialysis site from a vein
deliberate surgical correction of an AV fistulaadding artery to vein creates turbulence within the vein making is larger and more resilientex. common carotid artery and external jugual vein OR brachial artery and cephalic vein type of end to end anastomosis
indications for end to side anastomoses
- feline and canine renal transplant2. grafting free vascularized segments of skin and musle3. systemic–pulmonary shunting (Blalock-Taussig) for treatment of metrology of fallot
optimal angle for end to side anastomosis
< 30-45 degrees to functionally approximate vessels and minimize turbulence NOT FREQUENTLY POSSIBLEup to 75 degree is considered acceptable
length of receiving vascular incision in an end to side anastomosis
length ~2x the donor vessel/graft (2:1) a ratio of 1:1 is commonly achieved
suturing an end to side anastomosis
can bevel donor sidestart at “heel” firstuse double armed suture+/- plegets +/- dacron, PTFE reinforcementthen start at “toe”tie in the middle of each sideallow release of proximal inflow occlusion to allow release or air and thrombi before closure
predominant autologous vascular grafting material in vet med
JUGULAR VEINharvested and kept MOISTlidocaine or papaverine may be applied to limit vessel spasmligated caudally, cannulated proximally and flushed with heparinized saline/lidocainethen ligate cranial segment and transect donor segment
gold standard vascular imaging modality for endovascular surgery
ANGIOGRAPHY
composition of a guidewire
outer stainless steel coil warpinner wire (mandrel) that taperdistal is softer and more flexibleusually have anti friction coatingcommon 0.035 inch
major components for endovascular surgery
–angiography/fluoro–needle–guidewire–vessel dilator–vascular access or introducer sheath–catheter or stentSeldinger technique
types of intravascular stents
—self expanding or balloon expandingself expanding are more flexible but cannot be over expandedballoon expanding can have variation in final diameter BUT may be prone to dislodging prior to reaching site (thus may need to use delivery sheath or guiding catherSE is better choice for tortuous areas and areas of significant motion (ie. trachea)
stent materials
Stainless steel: braided, foreshorten, less radial strength, less useful in high motion areas, but RECONSTRAINABLE ex. WallstentNitinol: nickel and titanium alloy has thermal memory, less foreshortening, more predictable length and diameter
indications for central venous catheter placement
—hemodynamic monitoring/pressures—frequent blood sampling—parenteral nutrition–medication administrationjugular access or PICC (peripherally inserted central catheter)–medial or lateral saphenousfor jugular placement measure to first rib or caudal ipsilateral tricep; should end in cava BEFORE RA
indications for subcutaneous venous access port placement
companion port–keep HepLocked–serial sedation or anesthesia for long term wound mgmt or radiation therapy–administration of IV medications longterm (Ab or chemo)–serial blood samplingdisadvantages: kink, dislodge, hematoma, swelling, pain, bruising, need for surgical procedure placement (most are self limiting and prevented with good surgical technique/planning)
what is embolotherapy
selectively occlude blood flow–obliterate/reduce tumor blood supply–occlude aberrant vascular anomalies (PDA, PSS)—stop or reduce hemorrhagemechanical: silk, coils, ductal occludersliquids: lipiodol, cyanoacrylateparticulate: polyvinvyl alcohol, gelatin microspheres, autogenous blood clot material
what is embolectomy
removes blood clot to restore patencyarteriotomy, venotomy, or embolectomy cathetertx: feline aortic thromboembolism
pathologic consequence to AV malformations
reduced systemic vascular resistancearterial pressures decrease and venous pressures increaseif the AV fistula is large enough, HR and SV will increase in an effort to maximize CO to maintain arterial pressuresmay lead to high output cardiac failure
TX peripheral AV fistula
complete closure or removal of the aberrant AV communicationligation and division of artery proximal and sitar to communication is needed but venous ligation is not generally necessaryfailure to completely obliterate will need to formation of new communicationsalternative option: embolize area–cyanoacrylate embolization
