CNN Exam- Vascular Access 26 Questions with Verified Answers
List when patients should be referred for evaluation when an access clot is suspected -
... [Show More] CORRECT ANSWER - Any abnormal finding with measurement techniques such as U/S or MRA should NOT prompt immediate evaluation
- It is better to obtain serial measurements and conduct a trend analysis (i.e if each measurement suggests less flow than suspect stenosis)
- AV Grafts-
- Flow rate of less than 600 ml/min = referral
-Fistulas-
- Flow rate should be 400-500 ml/min
Other measurements- venous segment static pressure ration > 0.5 and arterial segment static pressure > 0.75 in grafts.
- Access re circulation or inadequate dialysis (Kt/V or urea reduction ratio) should lead to evaluation
***ANY INDICATION OF LIMB ISCHEMIA AT THE ACCESS SITE REQUIRES EMERGENT EVALUATION BY THE VASCULAR SURGEON***
Describe how to properly prepare the skin prior to cannulation of the graft or fistula - CORRECT ANSWER - Skin should be palpated for the thrill of the graft or fistula (this is where the needle will be inserted)
- Site is to be washed with CHG solution in combo with alcohol
- If site gets contaminated must re-wash
- Clean gloves must be worn by staff throughout the entire process. Must be changed if they become contaminated
- After cannulation, new gloves must be worn between patients
List the major disadvantages of tunneled cuffed catheters - CORRECT ANSWER - High rates of infection
- High rates of thrombosis
- Central venous stenosis
- Cosmetically displeasing
- Short shelf life
- Lower blood flow rates which increases dialysis times
Define monitoring, surveillance and diagnostic testing as they relate to vascular access as listed by the National Kidney Foundation - CORRECT ANSWER Monitoring refers to the examination and evaluation of the vascular access via physical examination to detect physical signs which suggest the presence of dysfunction
- Surveillance is the periodic evaluation of the vascular access by using tests that me involve special instrumentation and for which an abnormal test result suggests the presence of dysfunction
- Diagnostic testing refers to specialized testing and is prompted by some abnormality or other medical indication and that is undertaken to diagnose the cause the vascular access dysfunction
Describe how an arteriovenous fistula is made - CORRECT ANSWER Fistula access are done by vascular surgeons. Small incisions are made in the forearm or elbow and an adjoining artery and vein is anastomosed. The increased blood flow from the artery into the vein causes venous dilation. The vein must be allowed to fully dilate and mature which is about a 6 month process.
Fistula are the most preferred method for hemodialysis access because of their decreased infection and clotting rates. The procedure is usually done in an office setting and is relatively quick. Arm exercises are also prescribed to the patient to help facilitate fistula maturation.
List the advantages of arterio-venous grafts - CORRECT ANSWER - Large vessel for easier access during dialysis
- Shorter time to maturation for use (3-6 weeks)
- Many insertion sites
- Technically easier for surgeons
- Easy to repair
Describe the normal physical findings for both fistula and AV grafts - CORRECT ANSWER Fistula
- Well developed venous outflow with no areas of aneurysms
- Vessels partially collapse when the patient raises his/her arm above head
- Low pitch diastolic and systolic murmur with auscultation
- Thrill felt best at the arterial site but can be felt throughout the entire outflow vein
AV grafts
- No irregular areas or sites of aneurysms
- Low pitch systolic and diastolic sounds
- Thrill palpated best at the arterial anastomosis but also throughout the graft with easy compressibility
Describe how infected dialysis catheters should be treated - CORRECT ANSWER - Suggested when the patient presents with fever, access site in duration or elevated white blood cell count
-Initial step should be to draw 2 sets of blood cultures. The first set should come from the catheter itself and the second from a peripheral site. Empiric intravenous antibiotics are indicated to cover gram (+) organisms until culture and sensitivities return.
- Most dialysis catheters are in the IJ or SC veins with their tips lying near the right atrium. That leaves the patient at risk for right sided endocarditis. Thus, echo cardiograms are indicated if a new regurgitant heart murmur is auscultated or if patient has persistently positive blood cultures.
Describe the proper technique for cannulating a mature fistula or graft - CORRECT ANSWER - Skin should be properly cleaned with infection control techniques
- A tourniquet must be applied proximal to fistula. This will decrease the venous return and help engorge the fistula for easier access
- Pull skin in the opposite direction from the needle insertion
- For arterial puncture, the needle can be either in the same direction OR opposite direction as blood flow
- For venous punctures, the needle MUST be inserted in the same direction as the blood flow.
- After inserting the needle, it should be advanced slowly and taped to the skin's surface.
- Once dialysis is over, the needle should be removed at the same angle which it was inserted to prevent vessel tearing.
- Pressure should NOT be applied to the needle site until after it is removed to avoid vessel trauma and blood splashes
Describe how infections of AV grafts and fistula should be treated - CORRECT ANSWER SHOULD BE TREATED IMMEDIATELY
- Dialysis through an infected site is contraindicated
- The antibiotic of choice should cover both gram (+) and gram (-) bacteria. Prior to antibiotics, blood cultures should be drawn. Subsequent antibiotics should be based on culture and sensitivity results. Antibiotics have to be administered intravenously to be efficacious. If the infection does not resolve, incision and drainage or complete AV/fistula removal may be necessary
List acceptable methods for fistula and graft surveillance of patency as listed by the National Kidney Foundation - CORRECT ANSWER It is important to monitor patency of both fistula and grafts to ensure adequate dialysis and continued access.
Per the National Kidney Foundation, the following techniques are listed as acceptable for monitoring access patency:
- Doppler U/S
- MRA
- Various dilution techniques
- Physical findings
The physical findings include loss of palpable thrill, lack of bruit on auscultation, persistent arm swelling, presence of collateral veins and prolonged bleeding
Describe how an AV graft is made - CORRECT ANSWER Arteriovenous grafts are a conduit between arteries and veins. A synthetic (most common) material or bio-compatible conduit is inserted subcutaneously connecting an artery with a vein. Blood flows from the artery into the graft and empties in the vein. The graft requires 2-6 weeks to mature.
***It is important to note the direction of blood flow***
List proper infection control techniques which should be used on all catheters - CORRECT ANSWER National Kidney Foundation states the following guidelines should be used to lower infection rates:
- Catheter port site should be inspected for signs of infection prior to use before every dialysis session
- The catheter dressing should be changed with new gauze after each session aseptic techniques must be used which involves the use of gloves for handling of all catheter related procedures and wearing of surgical masks by staff.
List the clinical relevance from each of the history questions asked of patients prior to access - CORRECT ANSWER History of central venous catheter- associated with central vein stenosis
- Dominant arm- attempt to use non-dominant arm for access
- Pacemaker- associated with central vein stenosis
- Congestive heart failure- access can exacerbate CHF via high output cardiac failure
- Recent peripheral access- the integrity if the vein will be damaged and time is required to allow for vessel healing
- Anti-coagulation- can be a contraindication since frequent venous and arterial punctures are required
- Valvular heart disease or replacement- access increases susceptibility of cardiac valve infections
- History of neck, arm, chest trauma/surgery- vessel damage limits access options
- History of failed access- limits sites where access is available
List why the wrist is the first choice in fistula formulation - CORRECT ANSWER The wrist is the first choice by surgeons in choosing access sites. These reasons include:
- Technically easy site to work with
-Preserves proximal vessels in case the fistula fails
- Fewer adverse events including thrombosis, infections and vascular steal
Major disadvantage to wrist fistula is that it offers a lower blood flow rate in comparison to more proximal, larger vessels
List the advantages of tunneled cuffed catheters - CORRECT ANSWER - All patients can receive them
- Easily inserted at various sites
- Can be used immediately post insertion
- Skin puncture is not necessary
- No hemodynamic consequences (i.e. high output cardiac failure)
- Low costs
- Can be used as short term brides until graft/fistula mature
List signs of infections of vascular steal phenomena in patients with fistula and AV grafts - CORRECT ANSWER Signs of infection include erythema, swelling, in duration, warmth and broken skin. This is usually indicative of a local cellulitis but systemic bactermia must also be ruled out. Thus, 2 sets of blood cultures should be sent and antibiotics to cover gram (+) and (-) should be started. Alternate access must also be used while the infection resolves.
Signs of vascular steal syndrome include: cool extremity with discoloration and nail bed changes. One should also compare the extremities for warmth, skin color changes and muscle strength. If the access site differs from the other extremity, vascular steal should be ruled out.
Define dialysis catheter dysfunction and how to treat it - CORRECT ANSWER Dialysis catheters are said to be dysfunctional or under functioning when the blood flow rate is less than 300 ml/min. Dysfunctional catheters should be treated via the following methods:
- re-positioning
- thrombolytic
- catheter exchange
Sometimes catheters can get stuck of are lodged in next to the venous wall. This will obstruct flow and re-positioning the catheter will free it from adhering to the wall.
Thrombolytic are indicated when there is a suspected clot in the catheter. Usually heparin is administered with each dialysis session to prevent clot formation but it is not absolute. Small thrombolytic doses can aid in breaking up a clot.
If the aforementioned measures fail, a catheter exchange may be needed.
Describe the appropriate timing to prepare patients for vascular access and list what precautions should be taken - CORRECT ANSWER Patients with chronic kidney disease stage IV and V should be made aware of their prognosis and need for renal replacement. Consent must be obtained and type of access discussed with the patient.
In general, fistulas require 6 months lead time prior to dialysis, arterio-venous grafts require 3-6 weeks, peritoneal catheters need 2 weeks and permcaths can be used immediately. In preparation for permanent access, the upper extremity should not be punctured with small intravenous lines, peripheral intravenous central catheters or subclavian catheters. The helps ensure the integrity of the native veins and arteries in preparation for fistulas and grafts.
List the advantages of fistula over other access types - CORRECT ANSWER Fistulas are recommended by the National Kidney Foundation because of their lower complication rates. Foremost, they have the lowest rate of thrombosis and failures. Thus, they require fewer interventions which make them very cost effective. Fistulas do not get infected as often as permcaths or grafts. The combination of the stated advantages leads to lower hospitalizations and increased survival for dialysis patients.
Explain why fistulas and grafts are preferred over long term catheters - CORRECT ANSWER Long term catheters (permcaths) are associated with high infection rates and are frequently clotted.
- A permcath placed in the subclavian or IJ veins drains near the right atrium. This will subject the patient's cardiac valves (particularly tricuspid) to infections by staphylococcus and streptococcus. Fistulas and grafts also last longer and will decrease hospitalizations and improve patients' quality of life. All long term catheters should be placed with plans for more permanent access.
List the advantages and disadvantages of accessing the elbow for fistula formation - CORRECT ANSWER Elbow is the second choice for fistula
Major advantages
- Higher blood flow rate
- Easier to cannulate for hemodialysis access (large vessel)
Disadvantages:
- Technically more difficult for surgeons
- More edema
- Higher incidence of vascular steal syndrome and stenosis
List the preferred access types as per the current recommendations of the National Kidney Foundation - CORRECT ANSWER Order of preference:
Fistulas
- Wrist (radiocephalic)
- Elbow (brachiocephalic)
- Transposed brachial basilic vein
AV grafts (less preferred than fistulas)
- Forearm
- Upper arm
- Chest wall or lower extremity
Long term catheters (should generally be avoided)
- Long term (tunneled catheters)
- Short term catheters
List the appropriate history which should be elicited from patients in preparation for access - CORRECT ANSWER Patients should be asked the following:
- Have you previously had a central venous catheter
- Which is your dominant arm
- Do you have a pacemaker
- Does the patient have congestive heart failure
- Did the patient recently have a large peripheral or intravenous catheter
- Is the patient on anti-coagulation
- Does the patient have a history of valvular heart disease or valve replacement
- Does the patient have a history of neck, arm or chest surgery or trauma
- Any history of failed access
List the advantages and disadvantages of wrist and elbow fistula over other access sites - CORRECT ANSWER Advantages:
- Greater patency to flow after maturing
- Lower rates of stenosis, infection and vascular steal syndrome (the new conduit "steals" blood from the radial artery)
Disadvantages:
- Long time to mature (1-4 months)
- Difficulty accessing vein during hemodialysis relative to grafts
- Cosmetically displeasing
Discuss the limitations of placing long term catheters - CORRECT ANSWER Should not be placed:
- Where current or future AV access is maturing or to be placed
- In femoral veins in patients waiting for transplants
AV fistulas need time to mature as do AV grafts
- Placing a permcath near the site of the maturing access will endanger the access. In patients on the transplant list, access via the femoral vein should be avoided (places patient at risk for femoral vein thrombosis and femoral vein is near the renal vein) [Show Less]