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Prepared by:Dr. Muhammad Asim FazalMEEQAT GENERAL HOSPITALALMADINAH ALMUNAWARAH
Definition
Brief review of potassium regulation processes
Causes
Clinical Manifestations
Therapy
Hyperkalemia = plasma K+ concentration > 5.1mmol/L
Critical hyperkalemia = plama K+ concentration > 6.5 mmol/L
-The normal serum level of potassium is 3.5 to 5 mmol/L
-Daily Requirements 1-1.5 mmol/kg
-Dietary sources include dried fruits; legumes; meats; poultry; fish; soy; bananas; citrus fruits; potatoes; tomatoes; broccoli; mushrooms; dark, leafy green vegetables
Intracellular concentration about 150 mmol/L
The passive outward diffusion of K+ is the most important factor that generates the resting membrane potential.
Maintenance of steady state requires K+ ingestion = K+ excretion
Nearly all regulation of renal K+ excretion and total body K+ balance occurs in the distal nephron, via principal cells
Potassium secretion regulated by aldosteroneand plasma K+ concentration
Potassium homeostasis
This excess is (10%) excreted through the gut (90%) excreted through the kidneys
- The most important site of regulation is the distal nephron, including the distal convoluted tubule, the connecting tubule, and the cortical collecting tubule
-Gastrointestinal absorption is complete, resulting in daily excess intake of about 1 mmol/kg/d
I. Potassium release from cells
II. Excessive Intake
III. Decreased renal loss
IV. Iatrogenic
(Consider pseudohyperkalemia)
Intravascular hemolysis Tumor Lysis Syndrome Rhabdomyolysis Metabolic acidosis Hyperglycemia Severe Digitalis toxicity Hyperkalemic periodic paralysis Beta-blockers Succinylcholine; especially in case massive
trauma, burns or neuromuscular disease
- Uncommon cause of hyperkalemia.
-The mechanisms for shifting potassium intracellularly and for renal excretion allow a person with normal potassium homeostatic mechanisms to ingest virtually unlimited quantities of potassium in healthy individuals.
-Most often, it is caused in a patient with impaired mechanisms for the intracellular shift of potassium or for renal potassium excretion
Excessive intake
-Is the most common cause
--The causes of decreased renal potassium excretion include:
-renal failure
diabetes mellitus
sickle cell disease
Decreased excretion
Medications (eg, potassium-sparing diuretics, NSAID,angiotensin-convening enzyme inhibitors)
CausesShift from (ICF to ECF)
Decreased renal excretion Excessive intake
Hyperosmolality
rhabdomyolysis
tumor lysis
Succinylcholin
insulin deficiency
acute acidosis.
Diabetes mellitus (esp diabetic nephropathy
Renal failure
Congestive heart failure
SLE
Sickle cell anemia
NSAID
ACE Inhibitor
Potassium sparing Diuretics
Multiple Myeloma
chronic partial urinary tract obstruction
Oral or IV Potassium Supplementation
Salt substitute
Blood transfusion
Pseudohyperkalemia
-It is the term applied to the clinical situation in which in vitro lysis of cellular contents leads to the measurement of a high serum potassium level not reflective of the true in vivo level.
-Condition occurs most commonly withred cell hemolysis during the blood draw
(tourniquet too tight or the blood left sitting too long),
Weakness, which can progress to flaccid paralysis and hypoventilation.
Secondary to prolonged partial depolarization from the elevated K+ , which impairs membrane excitability.
Metabolic acidosis, which further increases K+Secondary to hyperkalemia impairing renal ammoniagenesis and
absorption, and thus net acid excretion.
Altered electrical activity of heart, cardiac arrhythmias.
ECG changes in order of appearance: Tall, narrow-based, peaked T wavesProlonged PR interval and QRS durationAV conduction delayLoss of P wavesProgression of QRS duration leading to sine wave patternVentricular fibrillation or asystole
Weakness and fatigue(most common)
fFank muscle paralysis
Shortness of breath
Palpitations
Symptoms
-Vital signs generally are normal
Exceptbradycardia due to heart block
or tachypnea due to respiratory muscle weakness.
Physical
Lab
Assess renal function.
Check serum BUN and creatinine levels to determine whether renal insufficiency is present
Check 24-hour urine for creatinine clearance
Estimate the glomerular filtration rate (GFR)
ECG
Changes occur when Serum Potassium >6.0 mmol /L
A-Initial T Waves peaked or Tented
B-Next ST depression loss of P Wave
QRS widening
C-Final Biphasic wave (sine wave) QRS and T fusion
Measure complete metabolic profile
-Low bicarbonate may suggest hyperkalemia due to metabolic acidosis.
-Hyperglycemia suggests diabetes mellitus.
Treatment
The first step
-determine life-threatening toxicity. By Perform an ECG to look for cardiotoxicity.
- if present Administer Iv Calcium Gluconate to ameliorate
cardiac toxicity.
-Initial dose: 10 ml over 2-5 minutes Second dose after 5 minutes if no response
-Effect occurs in minutes and lasts for 30-60 minutes
Anticipate EKG improvement within 3 minutes
The second step
-Is to identify and remove sources of potassium intake
-Change the diet to a low-potassium diet.
-Measure glucose and potassium every 2 hours
-Correct metabolic acidosis with sodium bicarbonate. 50ml I/V bolus
-Ventolin Nebulization
The third step
-Potassium shift from intravascular to intracellular
-Glucose and Insulin InfusionInsulin Regular 10 units IV 50 ml 50% of dextrose
The fourth step
-Is to increase potassium excretion from the body
-in normal kidney function by the administration of parenteral saline accompanied by a loop diuretic, such as furosemide Dose: 20-40 mg IV.
-Discontinue potassium-sparing diuretics, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and other drugs that inhibit renal potassium excretion.
Monitor volume status and aim to maintain euvolemia.
-In patients with hyporeninemia or hypoaldosteronismRenal excretion can be enhanced by administration of an aldosterone analogue, such as 9-alpha fluorohydrocortisone acetate (Florinef).
Emergency dialysis
Is a final recourse for unresponsive hyperkalemia with renal failure.
A 52-year-old man with hypertension and diabetes complains of weakness, nausea, and a general sense of illness, that has progressed slowly over 3 days. His medications include a sulonylurea, a diuretic, and an ACE inhibitor. On examination, he appears lethargic and ill. His BP is 154/105 mm Hg, HR 70bpm, temperature 98.6° F, and respiratory rate 22 breaths/min. The physical examination reveals moderate jugular venous distension, some minor bibasilar rales, and lower extremity edema. He is oriented to person and place but is able to give further history. The ECG shows a wide complex rhythm.
Laboratory studies performed are significant for potassium 7.8 mEq/L, BUN is 114 mg/dL and creatinine is 10.5.
Easily Distinguished ECG signs:
◦ peaked T wave.
◦ prolongation of the PR interval
◦ ST changes (which may mimic myocardial infarction)
◦ very wide QRS, which may progress to a sine wave pattern and asystole.
Patients may have severe hyperkalemia with minimal ECG changes, and prominent ECG changes with mild hyperkalemia.
Diagnosis: Hyperkalemia- Severe
◦ Classification of Hyperkalemia NORMAL: 3.5 to 5.0 mEq/L.
MILD: 5.5 to 6.0 mEq/L
SEVERE: Levels of 7.0 mEq/L or greater
It is important to suspect this condition from the history and ECG, because laboratory test results may be delayed and the patient could die before those test results become available.
1st Line option
Symptoms of hyperkalemia are usually nonspecific, so risk factors must be used to suspect the diagnosis
ECG changes consistent with hyperkalemia should be treated immediately as a life-threatening emergency. Do not await laboratory confirmation.
Intravenous calcium is the antidote of choice for life-threatening arrhythmias related to hyperkalemia, but its effect is brief and additional agents must be used