Читать книгу Emergency Management of the Hi-Tech Patient in Acute and Critical Care - Группа авторов - Страница 88

6 Vascular Access for Hemodialysis

Sarah Fesnak1,2, Xenia Morgan3, and Kimberly Windt3

1 Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA

2 Division of Emergency Medicine, Department of Pediatrics, Children’s Hospital of Philadelphia, Philadelphia, PA, USA

3 Hemodialysis Unit, Division of Nephrology, Children’s Hospital of Philadelphia, Philadelphia, PA, USA

Introduction

Hemodialysis is a procedure to regulate fluid status and remove waste products and/or toxic substances from a patient's blood. Vascular access allows a patient's blood to be circulated extracorporeally through a dialysis machine, where it filters past a semipermeable membrane in contact with a washing solution (diasylate). Fluid and solutes are removed via diffusion, osmosis, and convection. Hemodialysis is one of three forms of renal replacement therapy (the others are peritoneal dialysis and renal transplant) available to patients with advanced renal failure. Patients may require hemodialysis on a long‐ or short‐term basis, depending on their underlying disease process and potential for transplant, with many patients undergoing years of dialysis. Nearly 300 000 patients in the US have end‐stage renal disease, and more than 60% of these undergo hemodialysis. The vast majority of these patients are adults, with fewer than 1% of hemodialysis patients under age 20 years. In both pediatric and adult patients, however, complications of vascular access remain a significant source of morbidity and mortality.

Equipment/Device

All forms of vascular access in hemodialysis allow blood to be pumped from the patient through the dialysis machine and back into the patient in a closed circuit. This circulation requires large‐caliber access for rapid circulation of patient's blood volume. There are several options for short‐ and long‐term vascular access in patients requiring hemodialysis.

Hemodialysis Catheters

These are large‐bore double lumen central venous catheters. Benefits of this type of access are that it can be placed rapidly and used immediately after placement and does not require any additional needle sticks for use. Drawbacks of this form of access include the risk of infection, potential for the catheter to become dislodged or removed inadvertently, and long‐term risk of vascular stenosis.

Nontunneled hemodialysis catheter: This is a short‐term form of access that can be placed emergently for acute use or to bridge to a longer‐term access option. It is typically placed in the internal jugular (<3 weeks) or femoral veins (<5 days) and then stitched into place.

Tunneled hemodialysis catheter: This is a long‐term tunneled and cuffed central venous catheter, typically placed in the right internal jugular vein, but may be placed femorally. It may be kept in place for years (Figure 6.1).

Arterio‐Venous Access

These forms of access are surgically created anastomoses of the arterial and venous system used for hemodialysis. Venipuncture is used to access the anastomosis at each dialysis session. Benefits of these forms of access are decreased risk of infection as compared with central venous catheters and long use life. Note that the risk of infection remains higher in graft. Drawbacks include potential for thrombosis at the anastomosis, delay between placement and maturation/use, need to use needle sticks to access at each use, and potential cosmetic issues.

Figure 6.1 Photo of tunneled catheter in deidentified patient.

(Source: Photo credit Xenia Morgan.)

Figure 6.2 Photo of graft in situ.

(Source: Photo credit Kimberly Windt.)

 Graft: This is a synthetic material that is surgically placed between an artery and a vein in the nondominant arm. It may be placed in a straight, looped, or curved configuration and is palpable under the skin. Gentle palpation will reveal a thrill. Maturation takes at least two weeks before it may be used (Figure 6.2).

 Fistula: This is a surgical connection of patient's native artery to native vein in nondominant arm. It will be palpable under the skin. Gentle palpation will reveal a thrill. Maturation takes one to four months.

Indications

Hemodialysis may be used to replace renal function in acute and chronic renal failure. Some of the elements of renal function that may be controlled include the removal of naturally occurring metabolic waste products, regulation of acid–base status and electrolyte balance, regulation of intra‐ and extra‐vascular volume, and removal of toxic materials (e.g. after toxic ingestion).

Management

Hemodialysis Catheters

 Contact with the institution's or patient's renal and/or dialysis team is appropriate early during the patient's evaluation.

 Like all forms of central access, these devices should be handled by individuals trained in appropriate infection control and following the existing protocols of the home institution.

 Dressings vary by institution but may include a transparent dressing or one with a dry gauze component. Antiseptic and topical antibiotic use at exit site should conform to institutional policies.

 Note that catheters are locked with anticoagulant (e.g. high‐dose heparin, altepase, and citrate), and this must be removed prior to blood draws or instillation of medications (e.g. antibiotics) through the catheter. If not otherwise instructed by dialysis team, typically the volume removed should be three times the volume of the lumen (listed on the clamp of the device).

Arterio‐venous Access

 Contact with the institution's or patient's renal and/or dialysis team is appropriate prior to access. In general, access should be avoided aside from dialysis procedure This site should not be used for blood draws, administration of medications, etc.

 Avoid any other intravenous access or needle sticks in the extremity; avoid taking blood pressures or constricting clothing on the extremity.

 Note that only gentle palpation of the site is appropriate; firm pressure may occlude blood flow.

Complications/Emergencies

Hemodialysis Catheters

 Inability to draw blood from catheter: If the patient requires blood draw from the central access (e.g. in the setting of workup for fever) and clinician cannot draw from the lumen, contact the dialysis or renal team prior to attempting to flush. Recall that there is anticoagulant in the lumen which should not be flushed into patient without careful consideration. Conversation with renal or dialysis team will assist in planning appropriate approach.

 Hole or break in catheter: This should be treated, as with all compromise of central access, as a potential bloodstream infection. Cultures should be drawn, and the access should not be used pending repair or replacement by interventional radiology. Note that lab draws may be inaccurate for up to four hours after a dialysis session.

 Fever or evidence of exit site infection: Cultures should be drawn and antibiotics administered through both lumens of the catheter. Contact with renal and/or dialysis team will help direct therapy; in general, broad‐spectrum empiric antibiotic coverage is appropriate but review of prior culture data may further determine care. Note that lab draws may be inaccurate for up to four hours after a dialysis session.

 Displacement or migration of catheter: Displaced or migrated (for example, cuff is now visible outside of skin (as in Figure 6.3) catheters require replacement by interventional radiology. X‐ray may help determine the positioning of the catheter. Conversation with renal and/or dialysis team can determine urgency and protocol. Recall that this is a form of central access, and care should be used to apply appropriate pressure to stop bleeding.

Figure 6.3 Photo of fistula in situ.

(Source: Photo credit Xenia Morgan.)

Arterio‐venous Access

 Decreased or absent thrill: Patients will typically be familiar with the location and quality of the thrill at their access site. They will have been instructed on assessing it daily. If a patient presents with concern for a decreased or absent thrill at their site, assessment by Doppler ultrasound and rapid communication with the renal and/or dialysis team is appropriate. Delay in treatment may lead to worse outcomes for the access site.

 Swelling or discoloration surrounding access: This may indicate thrombosis or infection. Any evidence of discoloration, induration, swelling, pain, or warmth should be discussed with the renal and/or dialysis team. Peripheral cultures and Doppler ultrasound are often appropriate. Recall that lab draws may be inaccurate for up to four hours after a dialysis session.

Consultation

All forms of hemodialysis access are best managed by, or in consultation with, a patient or institution's own renal or dialysis experts. Early communication with these teams will reduce complications and morbidity for these patients.

Further Reading

1 1 National Kidney Foundation (2001a). K/DOQI clinical practice guidelines for hemodialysis adequacy, 2000. Am. J. Kidney Dis. 37 (Suppl. 1): S7–S64.

2 2 National Kidney Foundation (2001b). NKF‐K/DOQI clinical practice guidelines for vascular access: update 2000. Am. J. Kidney Dis. 37 (Suppl. 1): S139–S140.