Renal Replacement Therapy and Dialysis

Classifications of Dialysis:
- Acute: Utilized for patients requiring only a few sessions to address temporary issues, such as Acute Kidney Injury (AKI).
- Chronic: Utilized for the majority of patients who have End-Stage Kidney Disease (ESKD) and require lifelong therapy.
Major Types of Dialysis:
1. Hemodialysis (HD): Blood is filtered through an external machine (dialyzer). It is most commonly performed in specialized centers $3 \text{ to } 4$ times per week, though it can be performed at home if the patient is properly trained.
2. Peritoneal Dialysis (PD): Utilizes the patient's own peritoneum to complete treatment. This is very commonly performed at home. While it can be done on an acute intermittent basis, this is less common.
3. Continuous Renal Replacement Therapy (CRRT): A continuous form of hemodialysis specifically for critically ill patients in the ICU (covered extensively in adult health modules).

Usage Duration:
- Short-term: Days to weeks for cases of AKI.
- Long-term: Life-long or until a renal transplantation is performed for patients with ESKD.
Prevalence: Over $60\%$ of patients on long-term renal replacement therapy use hemodialysis.
Core Scientific Principles:
- Osmosis: In the context of dialysis, excess fluid is removed from the blood as water moves from an area of lower concentration to an area of higher concentration (the dialysis bath/solution circulating through the dialyzer).
- Diffusion: This removes waste products from the blood. Wastes move from an area of higher concentration (the blood) to an area of lower concentration (the dialysate).
- Ultrafiltration: Fluid moves from an area of high pressure to an area of low pressure. This is more efficient than osmosis or diffusion and is achieved by applying a suctioning-type force to the dialysis membrane.
Professional Roles: The specific type of dialysis and the prescription for ultrafiltration are determined by the nephrologist and executed by a specialized hemodialysis nurse.

Long-Term (Permanent) Access:
- Arteriovenous (AV) Fistula: The preferred method of permanent vascular access. It involves the surgical joining of an artery and a vein. It requires several weeks to "mature" before it can be used for needle insertion.
- AV Graft: A synthetic piece of material placed to link an artery and a vein. This is used when a patient's natural veins are unsuitable (e.g., in patients with diabetes or compromised vascular systems).
Short-Term Access (Central Lines):
- Common names include Permacaths, Vascaths, and Tesio catheters.
- Non-tunneled Catheter: Often placed in the internal jugular. Used for acute dialysis in the hospital or while waiting for a fistula to mature. These are not permanent solutions.
- Tunneled Catheter: Placed in the subclavian vein. Features a cuff for permanency and is sutured in place. Patients can leave the hospital with these while waiting for a fistula to mature or if their kidney recovery is anticipated within a few months.
Safety Warning for Central Access:
- Never administer medications, flush, or draw blood from a dialysis catheter unless it is an emergency and specifically approved by a nephrologist. These are the patient's "lifeline" and are for dialysis only.

Mechanism: Uses the patient's peritoneal membrane as the dialyzer. It removes toxic substances and wastes to establish fluid and electrolyte balance without an external machine.
Frequency and Lifestyle: Requires daily treatment but offers more flexibility in lifestyle and diet compared to hemodialysis (where patients are often strictly fluid-restricted).
The PD Exchange Process:
- An "exchange" consists of three steps: Drainage of previous fluid (dwelling in the abdomen), followed by the installation of new dialysis fluid.
- Drainage: Must monitor that the volume coming out is at least equal to what was put in (e.g., if $2\,L$ went in, at least $2\,L$ plus extra fluid should come out).
- Fill: Fresh solution (usually in $2\,L$ bags) is infused into the abdomen via gravity.
- Dwell: The fluid stays in the abdomen while the patient performs daily activities.
Major PD Approaches:
- Continuous Ambulatory Peritoneal Dialysis (CAPD): Exchanges are performed manually by gravity, usually every six hours or several times a day.
- Continuous Cyclic Peritoneal Dialysis (CCPD): Uses an automated machine called a "cycler." Exchanges are performed automatically while the patient sleeps.

Protecting Vascular Access:
- Auscultation and Palpation: Assess for a "Bruit" (rushing sound of turbulent blood flow heard via stethoscope) and a "Thrill" (a strong, vibration-like pulse felt by hand). Remember: "Feel the thrill, hear the bruit."
- Restricted Extremity: Never take blood pressure, place IVs, or perform blood draws in the arm with the fistula or graft.
Clinical Monitoring:
- Meticulous Intake and Output ( $I/O$ ) tracking.
- Monitoring for uremic symptoms.
- Assessment of cardiac and respiratory status.
- Blood pressure monitoring: Essential for HD patients as taking blood out and putting it back in causes major pressure swings.
- Electrolyte balance evaluation.
Infection Control:
- Meticulous skin care around abdominal PD catheters.
- Maintaining sterile technique during PD access and cycler programming.
Pharmacologic Considerations (Renal Dosing):
- Ensure all providers are aware the patient is on dialysis.
- Adjust dosages for renal impairment; some medications given daily to others are only safe to give on dialysis days for HD patients.