potassium homeostasis mohammed almeziny bspharm r,ph. msc phd consultant clinical pharmacist
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POTASSIUM HOMEOSTASIS
Mohammed Almeziny BsPharm R,Ph. Msc PhD
Consultant clinical Pharmacist
Introduction
POTASSIUM is required for neuromuscular
tissues.
Intracellularly (98%).
Approximately 3500 mmol.
45 to 55 mmol/kg and varies with
age, sex, muscle mass.
50 mmol is located in extracellular.
(Hak & Dunham, 1983; Scribner et al, 1956).
Protective effect of potassium
An antihypertensive effect.
Inhibitory effect on free radical formation.
Reduce the relative risk of stroke mortality.
Offer a protective effect on renal arterioles
Daily requirement
Infants: 2-6 mmol/kg/day
Children: 2-3 mmol/kg/day
Adults: 40-80 mmol/day
(1mmol =1mEq 39.1 mg)
HYPOKALEMIA
DEFINITION
Hypokalemia is defined as a serum
potassium concentration less than 3.5
mmol/L. Normal levels range from 3.5 to 5
mmol/L
(Young & Koda-Kimble, 1988)
CAUSES
The most common cause of hypokalemia is drug therapy.
Shifting of potassium from extracellular to intracellular.
Reduction in potassium intake (Lindman, 1976; Lawson et al, 1979; Nardone et al, 1978;
AMA, 1983)
Blood pH effect
0.1 unit potassium of approximately 0.6 mmol/L;
0.1 unit corresponds to slightly less 0.6mmol/L.
Pseudohypokalemia
Leukemic patients whose leukocyte count ranges from 100,000 to 250,000 cells/µL.
The potassium in serum is taken up by the large number of leukemic cells when the blood specimen is allowed to stand at room temperature.
Clinical presentation
Usually are asymptomatic between 3.5-3 mmol/l
Malaise, weakness, fatigue and myalgia.
Renal tubular disorders, myocardial excitability, and metabolic abnormalities
The incidence of ventricular arrhythmia increases with the degree of hypokalemia.Rhabdomyolysis can occur below 2 mmol/L.
(AMA, 1983; Stanaszek & Romankiewicz, 1985)
Calculate adult K deficit in hypokalemia
1 mmol/L fall in serum potassium from 4 to 3 mmol/L =200 mmol.
< 3mmol/L, = 200 to 400 mmol for each 1 mmol/L
*After correct acid-base status of measured serum level.
Treatment and Prevention
Correct coexisting magnesium depletion.
The route of potassium administration depends on the acuity and severity of hypokalemia
Oral supplementation is usually preferred.
Parenteral potassium can be given as chloride, acetate, or phosphate.
POTASSIUM CHLORIDE is the supplement of choice
(Stanaszek & Romankiewicz, 1985; Beck et al, 1982).
Treatment and Prevention
For prevention of hypokalemia during diuretic therapyAdults: 20-40 mmol/day in 1-2 divided doses
Potassium repletion should be guided by close monitoring of serum concentrations and analysis of patient’s urine for potassium content to help assess the need for additional replacement.The potassium concentration should be monitored every 4 hours, more frequently in patients with severe potassium depletion or when a rapid infusion is given >10 mmol/L
Intravenous indication
The parenteral route is indicated for patients who cannot tolerate high dosages of oral potassium
Severe or symptomatic hypokalemia
Also indicated for the treatment of DIGITALIS-
induced arrhythmias.
(Cohen, 1979; McCarron, 1975).
June 1, 1998, Volume 55, Issue 11
Most hospitals removing KCl concentrate from patient units
, ISMP reports
Institute for Safe Medication Practices (ISMP).
JAMA / volume:280 (page: 1444)Promoting Patient Safety by Preventing Medical Error Lucian L. Leape, MD; et al October 28, 1998
Checklist
Independent verification.
Concentration calculations
Infusion rates
Correct line attachments.
WHO Collaborating Centre for Patient Safety Solutions, Control of Concentrated Electrolyte Solutions, Patient Safety Solutions, volume 1, solution 5, May 2007
INTRAVENOUS. POTASSIUM CHLORIDE MUST BE DILUTED BEFORE INFUSION.If serum potassium is > 2.5 mmol/L and neuromuscular and cardiac abnormalities are minimal (and renal function is not impaired),Concentrations not exceeding 40 mmol/L and at a rate of 10 to 15 mmol/hour. Doses should not exceed 100 to 300 mmol/day (AMA, 1983). The preferred diluents is sodium chloride
INTRAVENOUS. Cont’d
If serum potassium is < 2 mmol/L and muscle paralysis or cardiac abnormalities are present.
Concentrations not exceeding 60 mmol/L at a rate of 40 mmol/hour. Doses should not exceed 400 mmol/day (AMA, 1983).
Administration of potassium in high concentration should be given after strict evaluation.
Intravenous Rate of Administration
Should be kept within 10 to 20 mmol/hour. Frequent biochemical and ECG monitoring is necessary when rates >10 mmol/hour.The faster rates should be continued for only short periods of time
(Lawson, 1976; Lawson & Henry, 1977; van der Linde et al, 1977; Porter, 1976; Beeson et al, 1958; Schwartz, 1976; Dipiro et al, 1989).
Paediatrics dosing
Neonatal: Prevention of hypokalemia
Prevention of hypokalemia during diuretic therapy: 1-2 mmol/kg/day in 1-2 divided doses
Neonatal:Treatment of hypokalemia
Oral: 2-5 mmol/kg/day in divided doses; not to exceed 1-2 mmol/kg as a single dose.
If deficits are severe or ongoing losses are great, I.V. route should be considered preferred route of administration
Neonatal:Treatment of hypokalemia cont’d
Intermittent I.V. infusion): 0.5-1 mmol/kg/dose
Infuse at 0.3-0.5 mmol/kg/hour (maximum dose/rate: 1 mmol/kg/hour)
Repeated as needed based on frequently obtained lab values.
Severe depletion or ongoing losses may require >200% of normal daily limit needs
Prevention of hypokalemia
During diuretic therapyInfants and Children: 1-2 mmol/kg/day in 1-2 divided doses
Treatment of hypokalemia:
Infants and Children:Oral: 2-5 mmol/kg/day in divided doses; not to exceed 1-2 mmol/kg as a single dose
Treatment of hypokalemia: cont’d
Infants and Children:Intermittent I.V. infusion: 0.5-1 mmol/kg/dose (maximum dose: 40 mmol)
Infuse at 0.3-0.5 mmol/kg/hour (maximum dose/rate: 1 mmol/kg/hour)
Repeated as needed based on frequently obtained lab values;
Severe depletion or ongoing losses may require >200% of normal daily limit needs
Preparation and dispensing
I.V. Potassium intravenous preparations MUST BE DILUTED BEFORE ADMINISTRATION.
Mixing of potassium intravenous preparations is always the responsibility of Pharmacy I.V. section.
The additive port of the infusion bag should be held uppermost.
Preparation and dispensing cont’d
where potassium chloride solutions are prepared using potassium chloride ampoules, Potassium Chloride injection should be injected downwards into the bag the solution MUST be inverted at least 10 times to ensure potassium chloride is thoroughly mixed throughout the solution. Unshaken bags are prone to layering of added concentrate and are extremely hazardous.
Preparation and dispensing cont’d
Extra potassium MUST not be added to pre-mixed solutions containing potassium.
Potassium chloride ampoules MUST never be added to a hanging bag.
The preferred vehicle is normal saline
Dextrose solution should be avoided as the vehicle, unless is the patient has hypernatremia
glucose-induced insulin secretion will promote intracellular potassium uptake
Administration
Maximum recommended concentration (peripheral line): 80 mmol/L
Maximum recommended concentration (central line): 150 mmol/L
In severely fluid-restricted patients (with central lines): 200 mmol/L some studies 400 mmol/L
Monitoring
Continued therapy should be guided by clinical assessments plus potassium levels. Since potassium is an intracellular cation, the potassium level should be checked after one hour of stopping infusion or maximum within 12 hours of starting therapy.
Serum potassium level (s) shall be monitored every 24 hours for all patients receiving IV potassium supplements
Monitoring cont’d
In case of severe hypokalemia less than or equal 2.5 mmol/L baseline ECG is advisable.
ECG monitoring is required in children if the rate of infusion is 0.5mmol/kg per hour or greater
Continuous ECG monitoring should be used for intermittent doses >0.5 mmol/kg/hour.
Potassium infusion I.V. order
I.V fluid Concentration mmol/L
Rout of infusion
Peripheral/ Central
Infusion rate mmol/h
Ward ECG monitoring Yes/no
Standardisation
Standardisation
Without consistency there can be NO Quality
Non standardisation is a prime reason for waste
Reasons of non standardisation in IVWork practices not standardised (Potassium chloride)
Everyone uses their discretion
No predictability
Standardised Work
The current one best way to safely complete an activity with the proper outcome and the highest quality, using the fewest possible resources.
It is not absolute but the basis for kaizen (改善 ) (continuous improvement).
Standardised Work cont’d
One of the best strategy to reduce errors in addition it help to reduce the work load.
All standardised work must benefit the patients, nurses, physicians, other team members and the institute.
The advantages of premixed I.V. admixtures
preparation-time savings,
Assurance of properly reconstituted drugs,
Lengthy expiration dating,
Appropriate labelling.
Increased health care professional participation in direct patient care
Providing safe, effective and high-quality patient care.
Standardised Work cont’d
Premixed preparations
Batch preparations in PSMMC pharmacy.
20 mEq/L Potassium Chloride in 0.45% Sodium Chloride Injection, USP20 mEq/L Potassium Chloride in 0.9% Sodium Chloride Injection, USP40 mEq/L Potassium Chloride in 0.9% Sodium Chloride Injection, USP10 mEq/L Potassium Chloride in 5% Dextrose Injection, USP20 mEq/L Potassium Chloride in 5% Dextrose Injection, US20 mEq/L Potassium Chloride in 5% Dextrose and 0.2% Sodium Chloride Injection, USP20 mEq/L Potassium Chloride in 5% Dextrose and 0.45% Sodium Chloride Injection, USP30 mEq/L Potassium Chloride in 5% Dextrose and 0.45% Sodium Chloride Injection, USP40 mEq/L Potassium Chloride in 5% Dextrose and 0.45% Sodium Chloride Injection, USP10 mEq/L Potassium Chloride in 5% Dextrose and 0.45% Sodium Chloride Injection, USP40 mEq/L Potassium Chloride in 5% Dextrose and 0.9% Sodium Chloride Injection, USP20 mEq/L Potassium Chloride in 5% Dextrose and 0.9% Sodium Chloride Injection, USP, 1000 mL VIAFLEX Plastic Container
20 mEq/L Potassium Chloride in Lactated Ringer's and 5% Dextrose Injection, USP, VIAFLEX Plastic Container, 1000mLHighly Concentrated Potassium Chloride Injection, 10 mEq/ 50 mL, VIAFLEX Plus Container
ICUHighly Concentrated Potassium Chloride Injection. 20 mEq/50 mL, VIAFLEX Plus ContainerHighly Concentrated Potassium Chloride Injection, 40 mEq/100 mL, VIAFLEX Plus ContainerHighly Concentrated Potassium Chloride Injection, 10 mEq/100 mL, VIAFLEX Plus ContainerHighly Concentrated Potassium Chloride Injection, 20 mEq/100 mL VIAFLEX Plus Container
ORAL
Liquid, enteric-coated, and slow release preparation.Slow release:
1) Sugar-coated (slow-K) or film coated (K-Tab) tablets;
2) KCL incorporated into wax matrix, controlled release tablets (K-Dur)
3) A gelatin capsule containing microencapsulated KCL crystals that are coated with a water polymer
Monitoring for oral
Should be monitored at least every two weeks in ambulatory patients with mild deficiencies and in patients requiring prophylactic.
After a pattern is established, monitoring every 3 to 6 months is adequate (Stanaszek & Romankiewicz, 1985).
Dietary intake
Dietary intake alone will not induce hyperkalemia unless renal excretion is impaired.
Usually, the GFR must be less than 10 to 15 mL/minute
Unless there is concurrent hypoaldosteronism or distal tubular potassium secretory defects.
Food, Standard Amount Potassium
(mg) Potassium
mmol Calories
Sweetpotato, baked, 1 potato (146 g) 694 17.75 131
Tomato paste, ¼ cup 664 16.98 54
Beet greens, cooked, ½ cup 655 16.75 19
Potato, baked, flesh, 1 potato (156 g) 610 15.60 145
White beans, canned, ½ cup 595 15.22 153
Yogurt, plain, non-fat, 8-oz container 579 14.81 127
Tomato puree, ½ cup 549 14.04 48
Clams, canned, 3 oz 534 13.66 126
Yogurt, plain, low-fat, 8-oz container 531 13.58 143
Prune juice, ¾ cup 530 13.55 136
Food, Standard Amount Potassium
(mg) Potassium
mmol Calories
Carrot juice, ¾ cup 517 13.22 71
Blackstrap molasses, 1 Tbsp 498 12.74 47
Halibut, cooked, 3 oz 490 12.53 119
Soybeans, green, cooked, ½ cup 485 12.40 127
Tuna, yellowfin, cooked, 3 oz 484 12.38 118
Lima beans, cooked, ½ cup 484 12.38 104
Winter squash, cooked, ½ cup 448 11.46 40
Soybeans, mature, cooked, ½ cup 443 11.33 149
Rockfish, Pacific, cooked, 3 oz 442 11.30 103
Cod, Pacific, cooked, 3 oz 439 11.23 89
Bananas, 1 medium 422 10.79 105
Food, Standard Amount Potassium
(mg) Potassium
mmol Calories
Spinach, cooked, ½ cup 419 10.72 21
Tomato juice, ¾ cup 417 10.66 31
Tomato sauce, ½ cup 405 10.36 39
Prunes, stewed, ½ cup 398 10.18 133
Peaches, dried, uncooked, ¼ cup 398 10.18 96
Pork chop, center loin, cooked, 3 oz 382 9.77 197
Milk, non-fat, 1 cup 382 9.77 83
Apricots, dried, uncooked, ¼ cup 378 9.67 78
Rainbow trout, farmed, cooked, 3 oz 375 9.59 144
Food, Standard Amount Potassium
(mg) Potassium
mmol Calories
Buttermilk, cultured, low-fat, 1 cup 370 9.46 98
Cantaloupe, ¼ medium 368 9.41 47
1%-2% milk, 1 cup 366 9.36 102-122
Lentils, cooked, ½ cup 365 9.34 115
Honeydew melon, 1/8 medium 365 9.34 58
Kidney beans, cooked, ½ cup 358 9.16 112
Plantains, cooked, ½ cup slices 358 9.16 90
Split peas, cooked, ½ cup 355 9.08 116
Orange juice, ¾ cup 355 9.08 85
Yogurt, plain, whole milk, 8 oz container 352 9.00 138
HYPERKALEMIA
Introduction
Hyperkalemia is a potentially life-
threatening illness, which can be
difficult to diagnose clinically because of
paucity of reliable signs and symptoms.
Definition
Hyperkalemia is defined as a serum potassium concentration greater than 5.5 mmol/L
(Cox, 1981).
Clinical Manifestation
Cardiac excitability, possibly progressing to
ventricular fibrillation and asystole.
Coexisting hyponatremia, hypocalcemia, and
hypomagnesemia all reduce the threshold
potential, thereby increasing the patient’s
susceptibility to the cardiac effects of
hyperkalemia.
Mortality/Morbidity
Reported death rates rate range up to 67% if
severe hyperkalemia is untreated.
Gender: Male = Female
Causes Decreased or impaired potassium excretion.
Acute or chronic renal failure (most common).Potassium sparing diuretics.Urinary obstruction. Sickle cell disease. Addison disease (chronic adrenal
insufficiency).Systemic lupus erythematosus (SLE).
Causes cont’d
Additions of potassium into extracellular space:
potassium supplements (eg, PO/IV
rhabdomyolysis,
hemolysis (eg, venipuncture, blood transfusions,
burns, tumor lysis).
Causes cont’d
Transmembrane shifts
Acidosis.
Medication effects (eg, acute digitalis
toxicity, beta-blockers, succinylcholine).
Elevating the plasma tonicity by 15 to 20
mOsm/kg will increase the plasma
potassium concentration by 0.8 mmol/L
Causes cont’d
Pseudohyperkalemia: Improper blood collection (eg, ischemic
blood draw from venipuncture technique)Laboratory errorLeukocytosisThrombocytosis.
Classification of Hyperkalemia
Serum sodium is usually decreased, and acidosis is usually present.
The relationship between serum potassium and symptoms is not consistent.
Classification of Hyperkalemia cont’d
MINIMAL TOXICITY - < 6.5 mmol/L. MODERATE TOXICITY - 6.5-8 mmol/L give lassitude, fatigue, and weakness.SEVERE TOXICITY - >8 mmol/L, complete neuromuscular paralysis may dominate the clinical picture. Death from cardiac arrest occurs usually at 10 to 12 mmol/L. It may occur at lower levels if cellular potassium is severely depleted.
Treatment
Urgency of therapy depends on EKG findings and level of serum potassium.
If serum K is greater than 8 mmol/L. If the EKG shows the changes of
hyperkalemia.If the patient is extremely symptomatic.
Goal of therapy
Stabilizing the myocardium.The cardiac toxicity of hyperkalemia is a major cause of morbidity and mortality,
Shifting potassium from the extracellular to the intracellular compartment.
Promoting the renal excretion and GI loss of potassium.
Calcium
The first drug to be used for severe hyperkalemia (> 7.0 mmol/L) when the ECG also manifests significant abnormalities.
Antagonizes cardiac toxicity.
onset < 5 min and lasts 30-60 min.
Calcium chloride is the preferred salt.
Calcium chloride is very irritating, and should only be given via a central venous catheter.
CALCIUM cont’d
Dose of 10 to 20 mL of 10% calcium gluconate IV over the course of 1 to 3 minutes =(2.32 mmol)
10 gram (100ml) calcium gluconate = 930 mg elemental calcium = 46.50 mEq = 23.25 mmol.
CALCIUM cont’d
The dose can be repeated in 5 minutes if ECG changes do not resolve and as needed afterward for recurrence.
With no response after the second dose, additional attempts, however, are not beneficial..
Enhance the effects of the cardiac glycoside by causing arrhythmias.
SODIUM BICARBONATE
Shift potassium intracellularly.
Its efficacy in this setting has been questioned.
The usual dose, 44 to 50 mmol, is infused slowly over the course of 5 minutes and repeated in 30 minutes when necessary.
Blood pH should be monitored to avoid excess alkalosis.
May be beneficial in patients with severe metabolic acidosis (pH <7.20).
SODIUM BICARBONATE cont’d
Onset of action is within minutes and lasts approximately 15-30 min.
The hypokalemic effect is variable and may be delayed up to 4 hours,
It is reportedly ineffective in patients on maintenance hemodialysis.
INSULIN/DEXTROSE
Enhances intracellular potassium shift.
This regimen will lower serum potassium by 1 to 2 mmol/L within 30 to 60 minutes with the decrease lasting for several hours (Saxena, 1989).
ADULT DOSE
Administer 25 g of dextrose (250 ml of a 10% solution) I.V + 10 units of regular insulin over 30 minutes, and then continue the infusion at a slower rate. (Saxena, 1989).
Or, 50 ml of a 50% dextrose solution with 5 to 10 units of regular insulin may be administered I.V over 5 minutes.
If the serum glucose is more than15mmol/l glucose administration with insulin is not required
PEDIATRIC DOSE
0.5 to 1 g/kg/dose followed by 1 unit of regular insulin intravenously for every 4 grams of glucose infused; may repeat every 10 to 30 minutes (Barkin, 1986).
HYPEROSMOLARITY
It must be remembered that 50% dextrose (2525 mOsm/L) , and even 25% dextrose (1330 mOsm/L) , are very hyperosmolar and may be sclerosing to peripheral veins (Chameides, 1988).
Peripheral veins can tolerate up to (900 mOsm/L).
Administration of hypertonic solutions via central lines is preferred, if possible.
Calcium Polystyrene Sulphonate Powder “Calcium Resonium”
Onset of action: May be delayed 2-3 days due to GI transit time
Absorption: None
Excretion: Feces (100%)
Patient information:Take a laxative, drink plenty of water and increase intake of fibrous food to prevent constipation.
Calcium Polystyrene Sulphonate Powder “Calcium Resonium”
Treatment Initiation
if potassium level >6 mmol/L discontinue when potassium ≤5 mmol/L
Dose AdultsGeriatric
Oral administration: 15g once to four times daily as a slurry in waterRectal route: Single dose of 30g as a warm emulsion up to four times daily
Small children and infants
The practical exchange ratio of 1 mmol/L potassium/g of resin as the basis for calculation.
Calcium Polystyrene Sulphonate Powder “Calcium Resonium”
Children Oral (preferred route): Initial: 1 g/kg/day in divided doses; Maintenance: May reduce dose to 0.5 g/kg/day in divided dosesRectal: Initial: 1 g/kg/day in divided doses; Maintenance: May reduce dose to 0.5 g/kg/day in divided doses
Neonates: Rectal: 0.5-1 g/kg/dose
BETA-2-AGONIST
Appears to be a safe and reasonably effective means of treatment while waiting for dialysis or other potassium removing therapies to be initiated.
20 mg dissolved in 4 mL of saline over 10 minutes
Use with caution in hyperthyroidism, diabetes mellitus, or cardiovascular disorders.
Diuretics
Effects of diuretics are slow and frequently take an hour to begin.
Avoid use in patients with anuria
DIALYSIS
Peritoneal and hemodialysis are effective methods.
Slow to be practical in treatment of acute poisoning.
Dialysis with a glucose-free dialysate will remove 30% more potassium than one containing 200 mg/dL of glucose.
Patients who cannot tolerate fluids or have kidney dysfunction may benefit from dialysis (Ellenhorn & Barceloux, 1988).
Summary
Chronic Vs Acute
Symptomatic Vs Asymptomatic
Level
Summary of Treatment of Hyperkalemia
Questions?
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