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Hemodialysis 1120.e1

Hemodialysis
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• Hypotension or cardiovascular instability
Difficulty level: ♦♦♦
of dialysis. Some patients show signs of
(risk of worsening to critical level during • Owners should be prepared for 2-4 weeks
Synonyms treatment) renal recovery more quickly. If no signs of
Blood purification, renal replacement therapy, • Hypovolemia (correct and reassess renal recovery after 4 weeks of therapy, prognosis
dialysis function before therapy) for recovery decreases dramatically, although
• Severe pulmonary or cerebral hemorrhage some patients have recovered after 3-6
Overview and Goal (unless heparin-free therapy is provided) months of treatment.
• Hemodialysis is predominantly used to • Intractable/aggressive demeanor (because
treat kidney failure by removing uremic treatment requires intensive handling) Preparation: Important
toxins, correcting electrolyte and acid-base Checkpoints
disturbances, and normalizing fluid status. Equipment, Anesthesia • Patient exam and lab tests to determine Procedures and Techniques
The patient’s blood is circulated through a Sedation/anesthesia is required for the place- need for treatment, contraindications, or
dialyzer (filter) that is composed of fibers ment of a vascular access but not for the conditions to correct before treatment (e.g.,
made of a semipermeable membrane. hemodialysis procedure itself. Feeding tube anemia, hypotension) and for determin-
• Uremic toxins diffuse from the blood into a placement commonly performed at time of ing dialysis prescription: physical exam,
solution (dialysate) bathing the fibers based dialysis catheter placement; anesthesia with body weight, blood pressure, packed cell
on the concentration gradient. The dialysate tracheal intubation required for this procedure. volume or hematocrit, blood urea nitrogen
is a fluid solution similar in composition to • Vascular access: short-term, temporary, (BUN), creatinine, potassium, coagulation
plasma, having physiologic concentrations of large-bore double-lumen catheter (7 Fr for times (activated clotting time or partial
substances such as sodium, chloride, glucose, cats and small dogs; up to 14 Fr for large thromboplastin time) if using heparin
and bicarbonate. dogs); long-term, permanent, double-lumen anticoagulation
• By applying hydrostatic pressure, excess catheter with subcutaneous tunneling • Adequately functioning dialysis catheter:
fluid in the patient can also be removed. • Hemodialysis delivery system (hemodialysis thrombosis in the catheter or in the blood
Removal of fluid (ultrafiltration) also removes machine) vessel around the catheter is common and
solutes dissolved in the fluid being removed • Disposable extracorporeal circuit and dialyzer may require intervention or replacement
(convective clearance). (artificial kidney) • Dialysis prescription is customized for the
• Hemodialysis restores metabolic stability • Water purification system: particulate filter, patient, based on degree of azotemia and
and provides time for renal recovery to carbon sorbent, water softener, deionization desired clearance goals, patient size (i.e.,
occur. It does not improve renal function; bed, and reverse osmosis (if using hemo- blood volume), volume status, electrolyte
it temporarily replaces it. dialysis machine designed for intermittent balance (especially need for correction of
• In veterinary medicine, hemodialysis is treatment; not required with machines hyperkalemia and acidosis)
used predominantly to treat acute kidney designed for continuous therapy) • Need for special accommodations: using
injury (AKI) when renal recovery is pos- • Dialysate concentrates banked blood to prime the extracorporeal
sible. Hemodialysis for irreversible end-stage • Replacement fluids for convective therapies: circuit in small, hypotensive, or anemic
kidney failure is possible, but the commit- dialysis machine preparation or pre-packaged patients; additions to dialysate (e.g., ethanol
ment to ongoing treatment is financially and replacement fluids as antidote for ethylene glycol intoxication,
logistically taxing. • Monitoring equipment: blood pressure (BP) phosphorus if patient is normophosphatemic)
• Hemodialysis can also be used to remove monitor, coagulation timer (e.g., activated
toxins and certain drug overdoses if the clotting time [ACT]), in-line blood volume Possible Complications and
offending substance is small, has limited and oxygen saturation monitor (e.g., crit- Common Errors to Avoid
protein binding, and has a small volume of line), electrocardiogram (ECG) • Intradialytic: hypotension (extracorporeal
distribution. • Emergency cart: cardiopulmonary resuscita- circuit requires 60-200 mL of patient blood
tion drugs, oxygen, endotracheal tube to fill; more common in small patients),
Indications hemorrhage (excessive heparin effect),
• Acute uremia: oliguria or anuria, fluid Anticipated Time thrombosis (inadequate anticoagulation),
overload, severe refractory hyperkalemia, • Machine set-up: 20-60 minutes (based on dialysis disequilibrium (from rapid osmotic
severe azotemia (creatinine > 10 mg/ type of machine and operator experience) fluid shifts related to rapid correction or
dL [>884 mmol/L], blood urea nitrogen • Acute treatments: generally, a long, slow alteration of blood osmolality), hypocalcemia
> 100 mg/dL [>35.7 mmol/L]), lack of treatment provides better hemodynamic (if using citrate as anticoagulant)
improvement in or worsening azotemia, or stability in critically ill patients; 4-8 hours for • Interdialytic: catheter thrombosis or infection,
clinical signs despite adequate conventional the initial 1-3 daily treatments. Continuous delayed dialysis disequilibrium, hemorrhage
therapy treatment is an alternative. • Other complications: uremia related (uremic
• Chronic kidney disease: end-stage disease • Subacute treatments: after initial stabilization pneumonitis, pericarditis, encephalopathy,
with clinical signs uncontrolled by conven- (1-3 days), 4-5 hour treatments daily to every pancreatitis), treatment (volume overload,
tional therapy, pretransplant conditioning other day may be sufficient to control uremic drug toxicity), or underlying disease (sepsis,
• Miscellaneous: fluid overload (e.g., diuretic- signs. shock)
resistant congestive heart failure), acute • Chronic treatment: 4-5 hour treatment 3
poisoning or drug overdose (e.g., ethylene days per week Procedure
glycol, ethanol, phenobarbital) • Machine shutdown: 30-60 minutes at • Establish vascular access: a dialysis catheter is
the end of treatment to return blood to placed aseptically in the external jugular vein,
Contraindications patient, perform post-treatment patient with the tip reaching the cranial vena cava or
• Small size: < 2 kg (higher risk of hypotension, and laboratory evaluations, clean and store the right atrium (as confirmed by imaging).
inability to place adequately sized catheter) machine The dialysis catheter is strictly dedicated to

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