Ah, the kidneys…who doesn’t love ‘em? These two little bean-shaped organs will come into play with just about every single patient you deal with. In some cases it will be a chronic and devastating case of renal failure, (such as those patients requiring dialysis), but in most cases it will be moderate and more subtle. In all cases, renal function will tell you volumes about the patient’s fluid balance, electrolytes, blood pressure, infection and perfusion. Keeping an eye on renal function is a basic skill you’ll use every day as a beside RN…so let’s get to it!
Acute Renal Failure (ARF)
Patients with acute renal failure come in two varieties – those who have no history of renal disease and those who have chronic renal problems and are experiencing an acute worsening of their condition (when this occurs you will likely hear it called “acute on chronic renal failure.). For the purposes of this discussion, let’s focus on the patient who has no history of renal impairment and now…all of a sudden, their kidneys have gone all wonky.
Three types of renal failure
The first question you may be asking is, “What is causing the acute renal failure?” Excellent question! For starters, the ARF will typically be classified as one of three types…prerenal, intrarenal or postrenal, based on what is causing the renal failure in the first place.
Prerenal failure occurs when the cause is something essentially other than the kidneys themselves. The kidneys function fine, but for some reason they’re not getting perfused adequately so they can’t do their job well. A common cause for poor kidney perfusion is hypotension.
Intrarenal failure occurs when the problem has something to do with the kidney’s ability to function. A common cause of intra-renal failure may be due to contrast dye, nephrotoxic medications, infection or trauma to the kidney.
Postrenal failure occurs when the problem lies beyond the kidney, typically due to an obstruction of the urethra that causes urine to back up into the kidneys. Take note that the kidneys never ever ever like to have urine going the wrong direction.
Your patient is s/p AAA repair. For this surgical procedure, the surgeon has to clamp off the renal arteries for a period of time. It has been 8 hours since surgery and your patient has not passed any urine. What type of ARF is this patient experiencing?
You are taking care of an elderly woman with a blazing UTI. You learn from the night RN that the patient has passed only small amounts of urine that appear to be laced with a thick mucus. The morning labs indicate that your patient is in ARF due to what type of renal failure?
You’ve been taking care of a patient with glomerulonephritis. You understand this to be what type of renal failure?
OK! If you answered prerenal, postrenal and intrerenal (in that order), you are a kidney genius. Now to discuss how you’re going to actually take care of these patients.
Regardless of what CAUSED the renal failure, you are going to do pretty much the same things for every patient.
Monitoring urine output is mega important when you’re dealing with a patient in renal failure. Note that renal failure doesn’t always mean the patient is going on dialysis…renal failure doesn’t have to be absolute to be present. So, your patient will likely still be making urine…just probably not enough overall. What you are looking for is any sign that urine output is dropping off.
Normal urine output is 0.5ml/kg/hr. Yes, we’ve all heard that 30ml/hr is sufficient, but what if your patient is 6’4” and weighs 285 pounds? Well, his desired urine output is actually 64ml/hr. If your patient is a teeny tiny little gal who weighs 92 pounds, her urine output goal is actually closer to 21ml/hr. If your urine output is decreased for more than 3-4 hours, then this warrants a call to the doc, especially if it’s causing problems for the patient or you suspect something even scarier is going on (one of the hallmark signs of sepsis is decreased urine output!).
Monitor lung sounds
When the kidneys aren’t working properly, the body’s fluids aren’t expelled as they should be. In many (actually most) cases, this fluid backs up into the lungs causing coarse, wet lung sounds and decreased oxygen saturation. If your patient’s lungs sound wet and their urine output is down, you should probably ask the doc for an order of IV Lasix (provided their blood pressure can handle it.)
Because the kidneys filter some key electrolytes, you can expect these to be altered when renal function is impaired. The MOST important electrolyte you are going to monitor is potassium because of the potential for hyperkalemia to cause cardiac arrhythmias. If you are taking care of a renal patient who starts having runs of V-tach or shows tall, peaked T-waves on their EKG…check a K level and call for a stat order of the hyperkalemia cocktail. This is a standard treatment given to patients with elevated potassium levels in order to get them down to the safes zone. It consists of insulin, glucose, kayexalate and albuterol.
The insulin opens the cell to take the glucose into the cell…recall that potassium will hitch a ride with the glucose and go into the cell, which causes the serum levels of K to decrease. Kayexalate binds potassium in the GI tract (basically the patient poops it out). And, albuterol decreases potassium by also shifting potassium into the cell. Another medication you’ll see given in symptomatic hyperkalemia is calcium gluconate…the calcium protects the myocardium from the elevated levels of potassium and reduces myocardial excitability.
As you just read, hyperkalemia causes arrhythmias, elevated T waves and yes, even cardiac arrest. If your patient’s K levels are high, you’re going to make sure they are on a cardiac monitor at all times.
So, to recap…the four things you are going to monitor if your patient has renal impairment are:
- Fluid balance (I/O)
- Lung sounds
Now go forth and be a renal rockstar!