Claves para conocer la hiperpotasemia

Author: P2P Asistencial

Let’s begin reviewing what potassium is. Potassium is an ion found mostly inside cells, contrary to sodium, which is mainly extracellular. These differences between sodium and potassium levels within and outside the cell are the result of the resting membrane potential. Potassium levels inside and outside the cell are maintained by the sodium-potassium pump. This is what maintains the resting membrane potential. How much potassium do we need each day? Approximately between 40 and 50 mEq/liter per day.

We may ingest much more potassium, but our bodies are prepared to eliminate the excess. Therefore, if there are no other co-occurring issues, we’ll never run the risk of having potassium levels that are too high. In the bloodstream, normal levels will range between around 3 1/2 to 5 mEq/liter. Potassium elimination will take place mostly through the kidneys: about 90% of the potassium we have in the body will be eliminated through the renal system, thus the importance of renal function when managing potassium levels. There are several circumstances and substances that impact potassium shifts from the bloodstream into the cell and from the cell into the bloodstream; therefore, these substances interfere with the movement of potassium. In the case of insulin, what it does is increase potassium permeability in the active cell through the pump that manages potassium levels. Adrenergic stimulation also modifies potassium levels.

Thus, beta-stimulants shift potassium towards the cell; alpha-adrenergic agonists shift potassium outside of the cell and into the plasma. The acid/base equilibrium is also a factor: when there is acidosis, this will cause potassium to flow out of the cell and into the plasma; approximately per each 0/1 decrease in ph there will be an increase of 0/6 in potassium mEq/liter. Hyperosmolar Syndrome will also alter potassium levels. The higher these are, the higher the levels of potassium in the plasma. Aldosterone is also important as it is a hormone that regulates potassium levels. What are the causes of hyperkalemia? There is pseudo-hyperkalemia, which as its name indicates is not real hyperkalemia: there are high levels of potassium, but these are the result of some specific circumstance. There may be a high level in potassium absorption; there might be extracellular redistribution, that is, potassium is leaving the cell and entering the bloodstream, and there might be a reduction in the kidney’s ability to eliminate potassium. Pseudo-hyperkalemia, that is, not actual hyperkalemia, may be due to hemolysis, when blood is drawn for a test, when a tourniquet is too tight, or something is hurting the muscle; also if the sample sat too long before processing this may also increase potassium levels.

Other causes of pseudo-hyperkalemia include a large number of cells in the bloodstream, thrombocythosis or leukocythosis, especially leukocythosis over 200 thousand leukocytes or thrombocythosis over 500,000 platelets. True causes of hyperkalemia include an increase in potassium absorption, excess of potassium intake in the diet, which is a rare cause, since as I explained, the body can only absorb so much potassium and will eliminate any excess naturally, therefore it is very difficult to have high potassium levels due to this if there are no other co-occurring circumstances, such as alteration of renal function or prescription drugs. Potassium levels can also increase due to IV infusion, for example after a transfusion, which is also rare if there are no other co-occurring; also through potassium-chloride IV’s when the level is too high or the infusion speed is too fast, and drugs such as potassium penicillin, of which children above all need to receive smaller amounts of potassium, otherwise hyperkalemia may result. Another cause is extracellular redistribution. There are certain drugs that shift potassium levels, both outside and inside the cell. Thus acidosis increases potassium in the bloodstream because it shifts potassium outside the cell. If there is cellular lysis, destruction of the cell, intracellular potassium will cause an increase in potassium levels. It might also result from malignant hyperthermia, as well as hyperosmolarity syndrome, since the blood’s osmolarity increases and this causes liquid to shift out of the cell, including potassium.

Claves para conocer la hiperpotasemia

If there is an insulin deficiency, since insulin as previously mentioned shifts potassium inside the cell, this deficiency will cause it to shift out of the cell. And then there are genetic conditions, such as hyperkalemic periodic paralysis, or drugs, such as beta-blockers or hypertonic solutions. The other cause of true hyperkalemia would be a decrease in the kidney’s capacity to eliminate potassium; 90% of potassium is eliminated through the kidneys, so if the kidneys are failing, this will result in an increase of potassium. Aldosterone deficiencies as well: if there is a deficiency in this hormone, this will result in potassium retention.

Therefore all causes leading to hypoaldosteronism --whether primary, acquired or hyporeninemic--, will result in hyperkalemia. Also drugs that involve aldosterone, such as ACE’s and ARBs, which are commonly used for treating patients with heart disease and hypertension above all. The basic clinical symptoms we’ll encounter occur on two fronts: at the cardiac and neuromuscular levels. The most important one is the cardiac front, since as we mentioned, this might lead to cardiac instability, even cardiac arrest or death. This is a situation that needs to be diagnosed as soon as possible and also treated very quickly.

Alterations will always occur in terms of conduction; the heart’s contractility will not be altered. Cardiac stimulation will suffer a series of progressive alterations, depending on potassium levels. Alterations will depend on potassium levels: the higher they are, the greater the severity. But it will also depend on how quickly those levels are achieved. If they are achieved quickly, lower levels may cause toxicity much earlier than higher levels achieved chronically. If an ECG is performed we can see those alterations appearing progressively. Thus, with increasing potassium levels after six we’ll see the typical peaked waves, shortening of the QT interval, and above that, with potassium levels of around 7 to 8 mEq/liter, we will notice a broadened QRS complex, which will form almost a biphasic wave with the T wave, and above 8 we may see fused QRS’s, resulting in ventricular fibrillation or asystole. On the screen we see two images; on the one above, peaked T-wave complexes typical of initial hyperkalemia, and in the one below we see the QRS complex broadening; indeed, in one of the leads it begins to look wavy, which indicates asystole is about to occur.

What is happening at the neuromuscular level? Above all weakness, flaccid weakness. There will be no alterations in sensitivity, but mostly in strength. This diminished strength will have an ascending progression, that is, a person with hyperkalemia will lose strength from the feet up. It does not typically affect respiratory muscles, which often occurs with potassium levels above 8, although in cases of periodic paralysis may appear with lower levels of potassium. How to diagnose it? To diagnose any condition the main thing is to have the suspicion, and to have a suspicion we need a good medical history and physical examination. Medical history will show whether the person is suffering from weakness, bradycardia, dizziness. It will allow us to find out whether the person has a history of kidney failure, whether they are taking drugs that put them at risk for kidney failure or reduction in potassium levels.

Afterwards, through and EKG, we continue to collect data that suggests there is an alteration in potassium levels, and we only need to confirm this through a blood test. The blood test will ultimately confirm that the patient has high potassium levels and thus hyperkalemia. Blood tests will not only show high potassium levels, but also complement other data that will inform us about renal function, what do sodium ions look like, calcium levels, whether there is an excess of blood cells as a result of pseudo-hyperkalemia; whether there is metabolic acidosis, in which case bicarbonate would be of relevance. If the test results show diminished renal function, then we can conclude that reduction in potassium is due to renal failure. There is a reduction in urinary excretion of potassium. If on the other hand renal function is normal, this would point to an alteration in aldosterone levels, that is, the transtubular potassium gradient, which when under a level of 7, would point to hyperaldosteronism. What does the treatment look like? It is important to recognize hyperkalemia, to diagnose it and more importantly, treat it. We would come across a serious situation before asystole, so treatment has to be quick and effective.

The treatment consists of two parts: we have to eliminate potassium, but also stabilize the cardiac membrane, otherwise this would lead to the more serious result. In order to stabilize the cardiac membrane, we use calcium, both calcium gluconate and calcium chloride. These substances do not reduce the levels of potassium, and only affect potassium toxicity in the heart. These drugs act quickly, in around five minutes they already produce an effect, and in a very short time we can counteract the toxicity. However, their effect is short-lived, lasting about 30 to 60 minutes, and above all, they do not decrease potassium levels, for which we would have to use other treatments. We can potassium levels or eliminate it from the body, which is the most effective course, as the potassium will not return to the bloodstream, or shift it back into the cell, which is also effective, but runs the risk of shifting out again, if the circumstances that caused it to shift out remain. Thus, to increase potassium elimination we have non-loop diuretics: torsemide, furosemide, but only if kidney function is good, otherwise they will not be as effective.

There are also ion exchange resin beads. These eliminate potassium from the digestive tract. What is the problem with these substances? They are slow to act, and may take up to four to five hours to produce an effect, so if the situation is serious they are not effective. They are effective for maintenance treatment, and may be used orally or through an enema. We must be careful with enemas: there are descriptions of cases in which they were accompanied by sorbitol, resulting in intestinal necrosis. Lastly, if kidney function is not good, even if it is very poor and dialysis is needed, dialysis is another way of eliminating potassium from the bloodstream.

Another way of eliminating potassium would be, instead of removing it from the organism, removing it from the bloodstream, that is, shifting it inside the cell. What can we use for that? Insulin especially: insulin shifts potassium back into the cell. Generally it must be used with glucose to avoid hypoglycemia, and we administer 10 units of insulin with glucose at 10%, and this will shift potassium back into the cell. It begins to act in about 15 to 30 minutes, and lasts approximately 4 to 6 hours, in which case the effect is maintained longer once there is no toxicity due to the calcium administered at first, so the rest will help to maintain levels.

The other substance used is salbutamol, due to the beta-stimulant effect, both inhaled and IV. And sodium bicarbonate. It will be most effective in cases of acidosis, especially metabolic acidosis, and always being especially mindful of not introducing bicarbonate simultaneously with calcium gluconate and classical chloride, as it may rush into the bloodstream. To conclude, it is important to correctly diagnose the condition and treat it accordingly. It’s very easy to diagnose hyperkalemia once suspected though a clinical history and an EKG, after which treatment can be started, both to prevent heart toxicity as well as to reduce potassium levels, which we can later continue in case of confirmations 335 00:14:50,230 -- 00:14:51,960 through a blood test.

Drugs in Hypertension: Diuretics – Cardiovascular Pharmacology | Lecturio

Let's start off with the diuretics. And let's start with the most simple of diuretic mechanisms, the osmotic diuretics. The most commonly used osmotic diuretic is mannitol.…

By: Lecturio Medical Videos
CKD Video - ACE and ARB

Chronic kidney disease is a common, but serious condition that often goes undetected until the late stages. Caring for your kidneys is important for everyone. However, anyone with high…

By: Care for your Kidneys
Claves para conocer la hiperpotasemia

Let’s begin reviewing what potassium is. Potassium is an ion found mostly inside cells, contrary to sodium, which is mainly extracellular. These differences between sodium and potassium…

By: P2P Asistencial