Which of the following statements is incorrect regarding the physiological process depicted in the figure?
Wrong Answer: A. The initial stage of urine formation involves a substantial volume of fluid through the glomerular capillaries into Bowman's capsule, amounting to around 180 liters daily. Ultrafiltration is the separation of plasma water from whole blood using a semipermeable membrane and a pressure gradient. The procedure specifically removes cells and colloids, while retaining solutes and crystalloids. The pressures involved in the process are commonly referred to as Starling forces, namely hydrostatic and colloid osmotic (oncotic) pressures.
Wrong Answer: B. Most of this filtrate is reabsorbed, resulting in just approximately one liter of fluid that is eliminated from the body daily. Nearly 99 percent of ultrafiltration is reabsorbed. The glomerular capillaries, similar to other capillaries, have a high level of impermeability to proteins. As a result, the glomerular filtrate, which is the filtered fluid, is essentially free of proteins and does not include any cellular components, such as red blood cells.
Wrong Answer: C. Although the glomerular filtration barrier has a high filtration rate, it selectively filters molecules based on their size and electrical charge. Despite the considerable filtration rate, the glomerular capillary membrane typically inhibits the filtration of plasma proteins. Therefore, one may easily comprehend the level of integrity that the membrane necessitates. Filtration fraction = GFR/Renal plasma flow The plasma protein albumin has a molecular diameter of approximately 6 nanometres (60 angstroms), while the pores of the glomerular membrane are estimated to be around 8 nanometres (80 angstroms) in size. Albumin can be cleared via filtration due to its negative charge and the repulsion caused by the negative charges of the proteoglycans in the glomerular capillary wall.
Right Answer:D. The glomerular capillary membrane is similar to that of other capillaries, except that it has three (instead of the usual two) major layers: (1) the endothelium of the capillary, (2) a basement membrane, and (3) a layer of epithelial cells (podocytes) surrounding the outer surface of the capillary basement membrane. Hemodialysis membranes should replicate the glomerular filtration barrier. The solute clearance profile closely resembles that of the native kidneys. These membranes are impermeable to albumin, which is a large MW molecule. However, they are capable of removing low MW molecules such as urea, as well as middle MW uremic toxins like Beta 2 microglobulin. However, in dialyzer membranes, no electrostatic interactions are possible.
Wrong Answer:A. Citrate anticoagulation is associated with a higher risk of bleeding compared to heparin. This is incorrect. Citrate anticoagulation is associated with a lower risk of bleeding compared to heparin because it provides regional rather than systemic anticoagulation, which means it primarily affects the blood within the dialysis circuit.
Right Answer:B. Citrate is metabolized in the liver to bicarbonate, which helps manage metabolic acidosis. This is correct. Citrate is converted to bicarbonate in the liver, which can help manage metabolic acidosis in patients undergoing CRRT. This is a significant advantage as it helps correct acid-base imbalances.
Clinical Pearls: Different types of anticoagulation used in CRRT
Wrong Answer: C. ACE inhibitors should be avoided in all patients with cardiorenal syndrome. This is incorrect. ACE inhibitors can be beneficial in certain patients with cardiorenal syndrome, particularly those with heart failure, as they help reduce afterload and potentially improve cardiac output. However, their use must be balanced against the risk of worsening renal function and monitored carefully.
Wrong Answer:D. Renal function typically improves immediately following aggressive fluid removal. This is incorrect. While removing excess fluid can relieve symptoms and potentially improve heart function, renal function does not always improve immediately and can sometimes worsen temporarily due to hemodynamic changes.
