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Renal System: Acute Kidney Injury

This post will cover the Renal System: Acute Kidney Injury.

Before we start, be sure to download the free PDF study guide to enhance your learning. Link is listed here.

Acute Kidney Injury

Acute Kidney Injury is a rapid loss of renal function due to renal damage. This injury happens suddenly when it occurs but the good news is that it is reversible meaning the patient can go back to their previous health condition.

Acute Kidney Injury is serious because this can lead to hypo-perfusion and death of many cells throughout the body along with loss of renal function.

Though this condition is reversible, it takes time for the kidney to go back to its normal kidney function.


There are three terms that are very important to know when thinking of possible causes of the Acute Kidney Injury.

Prerenal means outside of the kidney. So causes done here would be due to blood loss due to trauma or surgery, dehydration or obstruction.

Intrarenal means within the kidney. Causes would include tubular necrosis, prolonged ischemia and nephrotoxicity.

Postrenal means between the kidney and urethral meatus. Causes would include bladder neck obstruction, bladder cancer or calculi.

When remembering signs and symptoms of AKI, remember that the kidneys are not able to excrete any wastes or fluid. So primary signs and symptoms of AKI will be retention of waste, fluids and electrolytes. Now let's move onto the different phases.

Phases of AKI and Interventions as a Nurse

There are different phases that we will go over along with actions to take as a nurse for each phase.

Onset is the first phase which starts with the event that caused it.

The next phase is the Oliguric Phase. Note that this phase happens to some patients, but not all. If the patient does have this phase, it typically lasts from 8 to 15 days. The longer the phase lasts, the less likely the patient will recover.

Oliguria means that there is a sudden decrease of urine. If the patient's urine output is less than 400 mL/day, they have oliguria.

Signs and Symptoms of Oliguria

Now, if a patient is unable to urinate, then that means that the patient will have fluid volume excess because they are unable to get rid of fluids due to kidney damage.

Signs of fluid volume excess are hypertension, edema, heart failure and pulmonary edema.

Another issue that a patient will have is Uremia which is when toxins build up in their system. Again because the kidneys cannot get rid of the toxins, signs of Uremia will include anorexia, nausea and vomiting.

What else would be an issue for a patient when their kidneys are not doing their task? Metabolic wastes build up. This is known as metabolic acidosis.

Signs of metabolic acidosis are Kussmaul's respirations which may look like the patient is hyperventilating as a response of acidosis.

In the previous videos we talked about electrolytes having a major role of homeostasis. Some of the electrolytes that build up in the body will cause neurological changes. Signs of this include tingling of the extremities, disorientation and even coma.

Another sign of oliguria is pericarditis which is an inflammation of the heart layer that causes chest pain. The patient will have friction rub and a low grade fever.

Oliguric Phase Interventions

The major action of the nurse is to restrict fluid intake if the patient has hypertension. Remember the more fluids the patient has, the higher their blood pressure.

Daily allowance for fluids may range from 400 to 1000 mL a day. Closely monitoring of input and output is vital.

Medications that will help the patient are diuretics which will help increase renal blood flow and get rid of retained fluids and electrolytes.

Diuretic Phase

After the Oliguric phase is the diuretic phase which is when the urine output rises slowly then suddenly the body gets rid of a lot of fluids. The amount of fluids could be from 4 to 5 liters a day.

When this happens, this is a good sign because it means that the kidneys are finally recovering. The patient's level of consciousness will also improve.

However, the main issue during the diuretic phase is that the patient could become dehydrated, hypotensive and tachycardic. So the most important interventions include monitoring vital signs, administering IV fluids and electrolytes to replace losses.

Recovery Phase

After the Diuretic phase is that recovery phase, this phase is also known as convalescent phase.

Now this phase is the longest because it may take up to 2 years for the patient to fully recover.

During this phase, the urine volume is back to normal. Memory greatly improves and the patient gets their strength back.

General Assessments for Acute Kidney Injury

Monitor vital signs mainly for hypertension, tachycardia and irregular heartbeat.

It is important to monitor urine intake and output as well as its color and characteristics.

Another very important assessment is daily weight. Remember that this is the best indicator for fluid volume changes of the patient. Any increase of ½ to 1 pound indicates retention.

Labs to monitor are the BUN, creatinine and serum electrolytes.

Auscultate the patients lung for wheezing, rhonchi and look for signs of edema which indicate fluid overload.

Be aware of medications that may be metabolized by the kidney because this can cause more harm to the patient.

Prepare the patient for dialysis or continuous renal replacement to treat fluid volume overload or metabolic acidosis.

Let’s recap

Acute kidney injury is a rapid loss of kidney function resulting in retention of fluids, wastes and electrolytes. Knowing this allows us to think of the signs of symptoms which would be hypertension and chest pain.

There are three causes of AKI which are prerenal, intrarenal and postrenal.

There are four phases of acute kidney injury which are onset, oliguria, diuretic and recovery phase.

Treatments include diuretic meditation and dialysis.

Well that concludes this video, join us in the next video as we cover chronic kidney disease. Thanks for watching!

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