Evaluating Renal Function in Aging (Nursing)

00:00 So how do we evaluate the renal function in the aging? Well here's 2 tests I want you to keep an eye on. The 2 tests that we can use are an estimated GFR and we can do that with some fancy math that you don't have to do, lab does it for us. And we can look at creatinine clearance. So I'm going to break both of these tests down because it's important that you understand what they tell us about the kidneys. Now, suddenly renal changes start after age 30 so it does kind of kick in relatively earlier than you would think it would. The GFR is the glomerular filtration rate. When you see that little e by it, that's an estimate of how much blood is actually passing through that glomeruli. Those little tiny filtering units in the nephrons each minute. That's what GFR is and then we can have a pretty wide range of variability among individuals. Okay, so when you're talking about age-related changes or decreases in GFR, there can be a wide range that's still considered normal. But remember these changes start at the age of 30. So, a rough estimate for you, something to kind of keep in mind is there is a decline in their estimated GFR of up to 10% per decade. That's just kind of a rough rule of thumb. Now you also are going to have impaired electrolyte and water management because that's what the kidneys do. Right? That's one of the things that kidneys do is they manage electrolytes and our fluids on-board. So, as you have a change in the eGFR, the function of the kidney, you're going to have, relative to what they were, impaired electrolyte and water management. So let's look at eGFR across the lifespan.

01:51 So we're taking with our little fellar again when Jose was a little tiny guy, you have a low GFR at birth. Seems kind of weird but remember everything is immature in babies.

02:02 Right? They're just brand new to the world. So their lungs are immature, their kidneys are immature, their lungs are immature. It's okay. It's normal to have a lower GFR.

02:13 Now by the age of 2, the terrible 2's, you'll be just right around an adult GFR level.

02:21 Let's look at up to age 40. The GFR maintains usually around 140 ml a minute and then you got that really ugly 1.73 m2. Don't worry about that. We usually just speak in that number, but we wanted to make sure we included the units for you there. So, GFR levels up to about age 40 should be around 140 ml. The second of the two tests that we're talking about evaluating renal function is creatinine clearance. Now creatinine clearance can decline by 0.75 ml per minute per year in older adults even if they don't have kidney disease or other comorbidities. Now, comorbidities refers to other disease processes, maybe like hypertension, diabetes, any of those other comorbid conditions. So, most important point: creatinine clearance can decline by this amount, 0.75 ml/min/year in older adults even if they have no other current disease processes. Now, on the cool side, not all older adults experience this decline. Okay, so it doesn't have to happen but it's still considered normal if it does. Now, independent, so separate from the creatinine clearance, kidney physiology is going to change with aging. Remember we talked about structure and function and hormones. That's going to happen, but even independent of the creatinine clearance test we're going to see those changes.