Dr Supachoke maspakorn Chiangrai regional hospital Despite advances in endovascular technology and the increase in the number of endovascular interventions open vascular reconstructions will continue to play a significant role in the management of patients with vascular disease ID: 915014
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Slide1
Basic principle of vascular bypass and AVF creation
Dr. Supachoke maspakorn
Chiang-rai regional hospital
Slide2“Despite advances in endovascular technology and the increase in the number of endovascular interventions, open vascular reconstructions will continue to play a significant role in the management of patients with vascular disease”
FACT
Slide3Clamps
Vascular clamps typically have jaws with rows of fine interdigitating serrations that allow clamping of the vessel without slippage or significant crush injury
.
Slide4Clamps
Bulldog vascular clamp
Slide5Castroviejo
Ryder
Mayo-
Hegar
Needle holder
The choice of needle holder is often dictated by the size of the needle used.
A Mayo-
Hegar
needle holder is typically used with large needles, and Castroviejo needle holders are typically used with small, fine vascular needles.
Slide6Forceps
Jeweler
Micro ring tip
Debakey
The forceps used during vascular procedures typically have very fine, non-crushing jaws.
Slide7Slide8Vascular Sutures
Non-absorbable sutures are used for vascular anastomoses and repairs.
Currently, monofilament sutures are most commonly used for vascular reconstructions.
Vascular sutures are usually double-armed with a needle on each end to allow continuous suturing in both directions from the initial knot.
Slide9Vascular Sutures
Slide10Vascular Grafts
Polyester grafts of different shapes and structures are available to replace the thoracic aorta.
Polyester and PTFE grafts are available as conduits for the abdominal aorta and
infrainguinal
vessels.
Autogenous vein grafts are favored in many small arterial reconstructions.
Slide11Vascular Grafts
Dracon graft
PTFE
Slide12Basic Considerations for vascular bypass
Slide13Basic Vascular Techniques
Vascular Exposure and Dissection
Anticoagulation
Blood Vessel Control
Arteriotomy
ClosureReplacement and Bypass Procedures
Slide14Vascular Exposure and Dissection
The basic concept is to approach and expose the vessels by the
most direct and shortest route possible
.
Use of electrocautery through lymph nodes should be avoided
to prevent significant lymph leak or the need to excise lymph nodes, leaving dead space in the wound.The basic surgical technique of traction with counter-traction is essential in vascular exposure. (Gentle tension on the vessel loop is recommended to prevent injury to the intima)
Slide15Anticoagulation
Before interrupting blood flow, the patient must be adequately anticoagulated
.
Unfractionated heparin at 75 to 100 U/kg is typically administered intravenously approximately 5 minutes before blood flow interruption.
We recommend that the anticoagulation be monitored by measuring the activated clotting time (ACT), aiming for a value of more than 250 seconds.
Slide16Blood Vessel Control
Ideally
, vascular clamps should be applied to a disease-free segment of the artery
.
Palpating the artery against a right-angle clamp can help determine the presence and extent of atherosclerotic plaque, which is often in a posterior location and not appreciated by only palpating the anterior aspect of the artery.
In the presence of significant plaque, the artery should be dissected more proximally to identify a less diseased site for clamping.
Slide17Blood Vessel Control
If clamping is necessary across an area of diseased artery, the clamp should be applied in a manner that opposes the soft part of the artery against the plaque without causing plaque fracture or vessel tear.
Slide18Others methods for blood vessel control
Balloon Occlusion
Vessel Loops
Tourniquet
Slide19Basic Considerations for vascular bypass
The reconstruction should be performed with preservation of the existing circulation
A configuration allows the maintenance of
antegrade
flow in the native vessel at the level of the proximal anastomosis.
The distal anastomosis allows the maintenance of retrograde flow through all patent branches.
The distal anastomosis is placed in a disease-free segment of the vessel distal to the occlusive pathology.
Slide20Slide21Slide22AVF creation
“The use of autogenous AV accesses in preference to prosthetic accesses because of their higher primary patency rates and lower infection rates”
Slide23General Principles
Avoiding Complex Access
A careful investigation of the vascular anatomy is important to identify arterial or venous pathology that may affect access outcome.
Although noninvasive vascular testing is useful, it may provide insufficient anatomic information for patients who have had multiple access procedures; therefore, contrast angiography (either CT or catheter-based) is often required.
Slide24Ideal AV access
A flow rate sufficient for effective dialysis
Excellent long-term patency
Minimal access-related complications
A cosmetic appearance acceptable to patients
“A mature autogenous AV access satisfies most of these criteria and is likely the optimal access choice”
Slide25Autogenous Access Maturation
An obligatory time for the access to “mature” or to become suitable for dialysis.
The access vein wall thickens (or becomes “arterialized”)
The KDOQI guidelines have defined the
“rule of 6s”
as the criteria for access maturation and/or suitability for cannulation 1. a vein diameter of 6 mm 2. an access flow rate of
600 mL/min 3. an access depth of 6 mm below the skin. 4. work length > 6 cm
Slide26Predicting Autogenous Access Outcome
The non-modifiable factors
Increased age
Diabetes
Predialysis
hypotension
Artery diameterArteriosclerosisVein diameterVein distensibility
The modifiable factors
Smoking
Timing of referral for access
Preoperative ultrasound imaging
Anastomotic configuration
Anastomotic techniqueFlow assessment
Antiplatelet agents
Far-infrared therapy
The timing of cannulation
Gender , body mass index,
access surveillance
, and the various needle cannulation techniques were not found to be predictive of autogenous access success.
Slide27Age
Advanced age and life expectancy are interrelated in terms of access choice because the improved long-term patency attributed to autogenous accesses may not be as relevant for elderly patients.
Associated with autogenous AV access failure, particularly with regard to the radial-cephalic configuration.
Tunneled dialysis catheters may be a reasonable option in some elderly patients.
Slide28Diabetes
Associate with failure of autogenous access.
As for advanced age, the negative predictor for the presence of diabetes has been associated primarily with the radial-cephalic configuration.
The overall success rate was poor in the presence
of advanced age, diabetes, and female gender.
Interestingly, diabetic patients have been shown to have comparable success rates for autogenous access procedures in the upper arm.
Slide29Obesity
The presence of obesity clearly affects the decision about the most appropriate access choice and increases the likelihood of postoperative complications, particularly wound complications.
The cephalic vein, which usually courses superficially, may be somewhat deep relative to the skin and mandate elevation and/or transposition in an obese patient.
Slide30Vessel characteristics
The inflow arterial diameters smaller than 2 mm have consistently been associated with poor autogenous maturation rates.
The success rate for brachial artery–based autogenous access have been consistently shown to be greater than those originating off the radial artery, likely reflecting the vessels’ absolute diameters and the distribution of arterial occlusive disease.
The absolute vein diameter that has been predictive of a successful autogenous access have varied, with minimum criteria ranging from more than 2.0 mm to more than 3.0 mm.
Slide31Decision
Slide32Decision
We have avoided placing permanent AV accesses in patients with ipsilateral central vein stenosis or occlusion
Slide33Pre-operative evaluation
Early referral: the KDOQI panel recommends that patients with a GFR lower than 30 mL/min/1.73 m
2
(CKD 4) should be educated about the different renal replacement therapies, also recommends that an
autogenous access be placed at least 6 months
prior to the anticipated dialysis start date, and
a prosthetic access should be placed 3 to 6 weeks in advance.Preservation of Autogenous Options: All upper extremity veins that are potentially suitable for an access should be preserved, and both percutaneously inserted central catheters (PICCs) and subclavian vein catheters should be avoided.Physical examination should include a thorough pulse examination with an Allen’s test to determine the dominant blood supply to the hand along with examination of the neck and chest to look for venous collaterals.
Slide34Pre-operative evaluation: non invasive imaging
preoperative noninvasive imaging was associated with a lower initial failure rate for autogenous access, improved primary assisted patency at 1 year, but no difference in primary patency at the same time point.
There is some variation in the vein diameter measurements, likely secondary to the variations in the patients’ general state of hydration related to their dialysis cycle.
This variation justifies repeating the peripheral vein imaging if the
basilic
and cephalic veins are deemed too small on the initial study.
Slide35Distal Radial-Cephalic Autogenous Arteriovenous Access
A meta-analysis of autogenous radial-cephalic access, reported an initial failure rate of 15% with a primary patency rate of 65% at 1 year.
A randomized trial of autogenous radial-cephalic and prosthetic AV accesses in patients with compromised vessels and concluded that the patency rates were poor in this setting, although there was no benefit for prosthetic access.
The anastomosis for the autogenous radial-cephalic AV access is traditionally configured in an
end (vein)-to-side (artery)
configuration to reduce the likelihood of venous hypertension in the hand from retrograde venous flow (side-to-side configuration).
Slide36Distal Radial-Cephalic Autogenous Arteriovenous Access
side
Slide37Upper Arm Autogenous Arteriovenous Access
The brachial-cephalic and brachial-
basilic
are the traditional or common upper arm autogenous access.
Access procedures based on the proximal radial artery may have a lower incidence of access-related ischemia, commonly referred to as “steal syndrome”.
Both a randomized, controlled trial and a meta-analysis have reported that the autogenous
brachial-basilic access is superior to an upper arm prosthetic AV access in terms of patency and reintervention rates.The transposed brachial-basilic AV access can be performed as either a single- or a two-stage procedure.
The other autogenous AV access options in the upper arm include the brachial-brachial and brachial-median antecubital AV accesses.
the patency rates were superior for the two-stage approach in a small, randomized trial
Slide38Upper Arm Autogenous Arteriovenous Access
side
side
Slide39Operative techniques
Regional anesthesia
may lead to dilatation of both the peripheral veins and inflow arteries, thereby facilitating autogenous access creation and
improving their maturation rate
.
A randomized trial examining the role of heparin anticoagulation at the time of access construction demonstrated
no benefit in terms of patency but increased bleeding.The flow through a large AV fistula is independent of the extent of the anastomotic length once the length exceeds 75% of the arterial diameter.
Slide40Postoperative Care
The patient’s wound and hand function are monitored closely, given the risk of access-related hand ischemia.
The patient is seen in the outpatient clinic within 2 weeks after the procedure and then at monthly intervals thereafter until the access is suitable for cannulation.
Ultrasound is quite helpful to determine the vein diameter, although we have not found the ultrasound-based flow measurements to be reliable or reproducible.
The KDOQI “rule of 6’s” to determine whether the access is suitable for cannulation.
Slide41Strategies to Facilitate Maturation
Balloon Angioplasty Maturation
Access Elevation
“
superficializing
”Accessory Branch LigationCentral Vein Stenosis: the treatment of asymptomatic stenoses greater than 50% were associated with a more rapid progression of stenosis and an escalation of the lesion, as compared with no treatment.
Medical Treatment: clopidogrel and dipyridamole/aspirin improved the primary patency rates for autogenous and prosthetic accesses, respectively, without an increase in the rate of bleeding complications, although there was no improvement in the fistula maturation or cumulative patency rates.
Warfarin may have a modest effect on access patency but is clearly associated with an increased risk of bleeding complications
Slide42Follow-up and Surveillance
The KDOQI expert panel recommends “an organized monitoring/surveillance approach with regular assessment of clinical parameters of the AV Access and HD (hemodialysis) adequacy”
“prospective surveillance of fistulae and grafts for hemodynamically significant stenosis, when combined with correction of the anatomic stenosis, may improve patency rates and may decrease the incidence of thrombosis.”
Several randomized trials have
failed to demonstrate a benefit
for
prosthetic AV access surveillance.
Slide43Thank you for your attention