Renal Replacement Therapy study guide previews.

Comparison CVVH vs CVVHD vs CVVHDF introduces the clinical pattern, physiology, and bedside decisions that matter for emergency and critical care practice.

Scope includes cRRT modalities (CVVH, CVVHD, CVVHDF), key terms (blood flow rate, dialysate rate, effluent rate, ultrafiltration rate), and core mechanisms (diffusion vs. convection).

Continuous Renal Replacement Therapy (CRRT) is a form of dialysis used in critically ill patients with acute kidney injury (AKI), particularly those who are hemodynamically unstable. It provides slow and continuous removal of solutes and fluid over 24 hours, helping maintain acid-base, fluid, and electrolyte balance.

Continuous Renal Replacement Therapy (CRespiratory RateT) Basics: Core Principles is the rate at which blood is pumped through the circuit (typically 100-200 mL/min). Why it matters includes determines the volume of plasma available for solute clearance. Higher flow enhances solute delivery to the filter. The mechanism involves diffusion. Continuous Renal Replacement Therapy (CRespiratory RateT) Basics: Core Principles is the rate at which dialysate flows countercurrent to blood (typical: 20-25 mL/kg/h total effluent).

Continuous Renal Replacement Therapy (CRRT) refers to a group of dialysis modalities used primarily in critically ill patients with acute kidney injury (AKI) who are hemodynamically unstable or require slow, continuous fluid and solute removal. CRRT mimics the natural kidney’s continuous function over 24 hours, unlike intermittent hemodialysis (IHD), which occurs over hours.

Hemodynamic instability includes slower removal of fluids and solutes avoids hypotension. Volume overloaded patients includes allows fine control of fluid balance (e.g., in ARDS). Cerebral edema patients includes gradual solute shifts reduce risk of intracranial pressure increases. Typically a large-bore double-lumen catheter in internal jugular or femoral vein. Draws blood through the filter (typically 100-200 mL/min flow rate). Semi-permeable membrane where solute and water exchange occurs. Administered before or after the filter depending on modality.

Explanation (why B): Life-threatening electrolyte derangements-especially refractory hyperkalemia with ECG changes-are absolute indications for urgent RRT. In hemodynamically fragile patients on vasopressors, CRRT is preferred over IHD because solute and fluid removal are gradual, minimizing abrupt intravascular shifts that can worsen hypotension. Although you’ve temporized, the rapid rebound indicates ongoing generation and limited renal excretion, so definitive potassium removal via RRT is warranted.

Why the others are wrong include Volume overload is an important indication, but in this moment it is not the most immediate life-threatening issue compared to malignant hyperkalemia, Creatinine value alone is not an indication; clinical context and complications drive the decision, and Uremic pruritus is a soft indication compared with hyperkalemia + ECG changes.

Eliminations include IHD > CRRT for rapid small-solute clearance, Infection risk is comparable when catheters are used; not a defining advantage, and Rapid correction is an IHD feature, not a CRRT one. Eliminations include Systemic heparin increases bleeding risk; use when citrate is contraindicated, LMWH accumulates in renal failure and is less titratable for CRRT circuits, and No anticoagulation often leads to early filter clotting.

Continuous Veno-Venous Hemodiafiltration CVVHDF is a type of continuous renal replacement therapy (CRRT) that removes solutes using both diffusion and convection. This allows removal of small and middle molecules while maintaining continuous fluid control.

CVVHDF removes waste using two mechanisms simultaneously Solutes move down a concentration gradient into dialysate (diffusion), Solutes are dragged with filtered plasma water (convection), CVVHDF = diffusion plus convection working together, and This provides the most comprehensive solute clearance of CRRT modalities.

Pressure forces plasma water across membrane leading to convection. Solutes move from higher concentration in blood to lower concentration in dialysate. Plasma water is pushed across membrane and solutes move with it.

It provides continuous clearance of small solutes and fluid in critically ill patients, especially those with hemodynamic instability. CVVHD removes waste by allowing solutes to move from blood into dialysate down a concentration gradient. Unlike CVVH, replacement fluid is typically not required for solute clearance. In CVVHD include Blood contains high concentration of waste.

It is designed for critically ill patients who cannot tolerate intermittent dialysis, particularly those with hemodynamic instability. CVVH removes plasma water across a filter leading to solutes are dragged with it leading to removed fluid is replaced. This mimics the function of the kidney’s glomerulus. In CVVH, pressure pushes plasma water across a filter membrane leading to solutes get dragged along with that water. This is called solvent drag. Simple concept includes cVVH removes waste by pushing fluid out of blood - the waste goes with the fluid.

Severe metabolic acidosis (e.g., pH < 7.1) unresponsive to medical therapy. The mechanism involves diffusion-driven solute clearance using a dialyzer. Cons includes hemodynamic instability risk due to rapid fluid shifts. Modes include CVVH (Convection): Continuous venovenous hemofiltration, CVVHD (Diffusion): Continuous venovenous hemodialysis, CVVHDF (Mixed): Continuous venovenous hemodiafiltration, Hemodynamically unstable ICU patients, and Gentle fluid removal, stable hemodynamics.

It provides slow, prolonged dialysis over several hours, allowing better hemodynamic stability than traditional intermittent dialysis. SLED removes waste using slow diffusion over an extended period of time, allowing gentler fluid and solute removal. In SLED include Blood contains high concentration of waste. This is the same mechanism as intermittent hemodialysis.