94 Questions
What is the primary meaning of the term 'hypokalemia'?
Lower than normal potassium levels in the blood
What percentage of the body's potassium is intracellular?
Around 98%
What is the concentration of potassium inside the cells compared to outside the cells?
It's around 33 times higher inside the cells
What is the purpose of the sodium-potassium pump in maintaining the internal potassium balance?
It pumps 2 potassium ions in for every 3 sodium ions out
What is the result of the difference in potassium concentration inside and outside the cells?
It leads to a difference in charge
What is the term for the balance of potassium ions inside and outside the cells?
Internal potassium balance
What happens to the membrane potential of muscle cells when there is low potassium in the blood?
It becomes more negative
What is a common symptom of diminished skeletal muscle contractions due to hypokalemia?
Muscle weakness
What is the typical diagnostic indicator of hypokalemia in an electrocardiogram?
Prolonged QT interval
What is the main goal of treatment for patients with severe hypokalemia?
Normalizing potassium levels
What type of muscle contractions can be affected by hypokalemia?
Smooth, skeletal, and cardiac muscle contractions
What is the typical blood potassium level that indicates hypokalemia?
Below 3.5 mEq/L
What percentage of potassium is reabsorbed in the proximal convoluted tubule?
67%
What is the primary function of alpha-intercalated cells in the distal tubule and collecting ducts?
Reabsorption of potassium
What is the effect of aldosterone on the principal cells in the distal tubule and collecting ducts?
Increases sodium channels and increases potassium pumps
What is the result of increased aldosterone levels in the kidneys?
Increased potassium secretion
What is the effect of loop diuretics and thiazide diuretics on potassium levels?
Increases potassium secretion
What is the primary cause of hypokalemia in cases of chronic diarrhea?
Direct loss of potassium in the feces
What is the result of hypokalemia on muscle function?
Decreased muscle contraction
What is the role of the principal cells in the distal tubule and collecting ducts?
Secretion of potassium
What is the effect of vomiting on potassium levels?
Metabolic alkalosis
What is the result of increased potassium secretion in the kidneys?
Decreased potassium levels in the blood
What is the main function of the kidneys in maintaining potassium balance?
Excreting excess potassium in the urine
What is the typical range of potassium intake through the diet on a daily basis?
50 mEq/L to 150 mEq/L
What is the effect of excess insulin on potassium balance?
It stimulates the uptake of glucose in cells, leading to hypokalemia
What is the effect of alkalosis on potassium balance?
It stimulates the uptake of potassium in cells
What is the role of beta-2-adrenergic receptors in potassium balance?
They stimulate the uptake of potassium in cells
What is the effect of respiratory alkalosis on potassium balance?
It has no effect on potassium balance
What is the main cause of hypokalemia due to an external potassium balance shift?
Dietary potassium deficiency
What is the role of the sodium-potassium pump in maintaining potassium balance?
It pumps potassium into cells
What is the effect of catecholamines on potassium balance?
They stimulate the uptake of potassium in cells
What is the consequence of insulin overdose on potassium balance?
It leads to hypokalemia
What is the primary component of the total body potassium?
Intracellular potassium
What is the term that refers to the balance of potassium ions inside and outside the cells?
Internal potassium balance
What is the approximate concentration of potassium inside the cells?
150 mEq/L
What is the function of the sodium-potassium pump in maintaining potassium balance?
To pump 2 potassium ions in for every 3 sodium ions out
What is the space between cells where you typically find fibrous proteins and long chains of carbohydrates?
Interstial space
What is the approximate percentage of the body's potassium that is extracellular?
2%
What is the primary mechanism by which the kidneys maintain external potassium balance?
Excretion of excess potassium into the urine
What is the effect of insulin on potassium balance in the body?
Increases potassium uptake into cells
What is the result of an internal potassium balance shift in the body?
Decreased potassium levels in the blood
What is the effect of catecholamines on potassium balance in the body?
Increases potassium uptake into cells
What is the primary cause of hypokalemia due to an external potassium balance shift?
Increased potassium secretion in the kidneys
What is the effect of respiratory alkalosis on potassium balance in the body?
Has no effect on potassium balance
What is the role of the sodium-potassium pump in maintaining potassium balance in the body?
Pulls potassium into cells from the blood
What is the effect of anorexia on potassium balance in the body?
Decreases potassium intake through the diet
What is the primary mechanism by which the body regulates potassium balance?
Internal potassium balance shifts
What is the effect of excess insulin on potassium balance in the body?
Increases potassium uptake into cells
What is the primary function of the alpha-intercalated cells in the distal tubule and collecting ducts?
To reabsorb potassium
What is the effect of aldosterone on the principal cells?
Increases sodium-potassium pumps
What is the result of increased potassium secretion in the kidneys?
Increased potassium excretion
What is the role of the principal cells in the distal tubule and collecting ducts?
To regulate potassium secretion
What is the effect of diuretics on potassium levels?
Increased potassium secretion
What is the consequence of hypokalemia on muscle function?
Decreased muscle contractions
What is the primary cause of hypokalemia in cases of primary hyperaldosteronism?
Increased aldosterone levels
What is the effect of metabolic alkalosis on potassium levels?
Increased potassium secretion
What is the role of the sodium-potassium pump in maintaining potassium balance?
To pump potassium into the cell and sodium out
What is the percentage of potassium reabsorbed in the proximal convoluted tubule?
67%
What is the likely effect of hyperpolarization of muscle cell membranes on muscle contractions?
Muscle contractions become weaker
What is the primary function of the sodium-potassium pump in maintaining potassium balance?
To maintain the concentration gradient of potassium ions across the cell membrane
What is the consequence of diminished skeletal muscle contractions due to hypokalemia?
Muscle weakness, cramps, and flaccid paralysis
What is the primary way the body maintains external potassium balance?
Through the kidneys excreting excess potassium in the urine
What is the typical range of potassium levels in the blood that indicates hypokalemia?
Below 3.5 mEq/L
What is the effect of hypokalemia on cardiac muscle contractions?
It leads to cardiac arrhythmias and cardiac arrest
What is the role of potassium leak channels in maintaining internal potassium balance?
To allow potassium ions to leak out of the cell
What is the consequence of respiratory muscle weakness due to hypokalemia?
Respiratory depression
What is the primary source of potassium intake in the body?
The diet
What is the term for the balance of potassium ions inside and outside the cells, maintained by the sodium-potassium pump and other channels?
Internal potassium balance
What is one possible cause of an internal potassium balance shift that leads to hyperkalemia?
Insulin deficiency
What is the primary mechanism of hyperkalemia in acidosis?
Exchange of hydrogen ions for potassium ions across the cell membrane
What is the effect of beta-2-adrenergic antagonists on potassium balance?
They decrease potassium uptake in cells
What is the result of cell lysis on potassium balance?
It increases potassium levels in the blood
What is the effect of exercise on potassium balance?
It increases potassium levels in the blood
What is the effect of alpha-adrenergic receptors on potassium balance?
They decrease potassium uptake in cells
What is the effect of hyperosmolarity on potassium balance?
It increases potassium levels in the blood
What is the effect of catecholamines on potassium balance?
They decrease potassium uptake in cells
What is the primary mechanism of hyperkalemia in patients with type I diabetes?
Insulin deficiency
What is the effect of acidosis on potassium balance in respiratory acidosis?
It has no effect on potassium balance
What is the typical effect of high potassium levels on muscle contractions?
It causes weakness and flaccid paralysis
What is the primary diagnostic indicator of hyperkalemia in an electrocardiogram?
Tall, peaked T waves with a narrow base
What is the effect of hyperkalemia on cardiac muscle contractions?
It leads to cardiac arrhythmias and cardiac arrest
What is the typical treatment for severe hyperkalemia?
Calcium, insulin, glucose, and sodium bicarbonate
What is the typical blood potassium level that indicates hyperkalemia?
Above 5.5 mEq/L
What is the primary effect of hyperkalemia on skeletal muscle contractions?
It causes weakness and flaccid paralysis
What is the typical cause of hyperkalemia resulting from excessive potassium infusion?
Rapid, excessive infusion of potassium into the bloodstream
What percentage of potassium is reabsorbed in the proximal convoluted tubule and the thick ascending limb?
67% and 20% respectively
What is the role of aldosterone in the kidneys?
Increases the number of sodium channels and potassium channels on the lumen side of the principal cell
What is the consequence of acute kidney injury on potassium levels?
Increased potassium retention leading to hyperkalemia
What is the primary function of the principal cells in the distal tubule and collecting ducts?
Secretion of potassium
What is the effect of hyperkalemia on muscle contractions?
Decreased muscle contractions
What is the term for the balance of potassium ions inside and outside the cells?
Potassium homeostasis
What is the consequence of hypoaldosteronism on potassium levels?
Increased potassium retention leading to hyperkalemia
What is the role of alpha-intercalated cells in the distal tubule and collecting ducts?
Reabsorption of potassium
What is the effect of drugs that reduce the effect of aldosterone on potassium levels?
Increased potassium retention leading to hyperkalemia
Study Notes
Hyperkalemia i hipokalemia - podstawy
- Hipokalemia to stan, gdzie poziom potasu we krwi jest niższy niż 3,5 mEq/L
- W organizmie ludzkim większość potasu (około 98%) znajduje się wewnątrz komórek
- Stężenie potasu wewnątrz komórki wynosi około 150 mEq/L, a na zewnątrz komórki tylko 4,5 mEq/L
- Różnica stężeń potasu między wnętrzem i zewnątrzem komórki tworzy gradient elektrochemiczny
Różnice w stężeniu potasu
- Stężenie potasu we krwi: 4,5 mEq/L
- Stężenie potasu wewnątrz komórki: 150 mEq/L
Wewnętrzny równowaga potasu
- Utrzymywany przez pompę sodowo-potasową, która pompuje 2 jony potasu do komórki za każde 3 jony sodu na zewnątrz
- Równowaga potasu jest ważna dla utrzymania potencjału spoczynkowego błony komórkowej
Zewnętrzny równowaga potasu
- Uzyskiwany z diety: 50-150 mEq/L dziennie
- Większość potasu jest wydalana przez nerki do moczu
- Nerki regulują ilość potasu we krwi przez filtrację, reabsorpcję i sekrecję w nefronie
Przyczyny hipokalemii
- Zewnętrzna nierównowaga potasu:
- Nadmierna wydzielina potasu przez nerki
- Niewystarczająca ilość potasu w diecie
- Wewnętrzna nierównowaga potasu:
- Insulina powoduje przeniesienie potasu do komórki
- Zmiana pH krwi (alkaloza) powoduje wymianę jonów wodorowych na jony potasu
Objawy hipokalemii
- Osłabienie mięśni szkieletowych
- Skurcze mięśni
- Problemy z oddychaniem
- Arrythmia serca
- Zatrzymania akcji serca### Zmiany w równowadze potasu w organizmie
- Najpierw potas jest swobodnie filtrowany z krwi do moczu w kłębuszku nerkowym
- Następnie około 67% jest wchłaniane w zwoju spiralnym kanalika proksymalnego, a dodatkowe 20% w zwoju thick ascending limb
- Pozostałe 13% wchłaniania lub wydzielania potasu w kanaliku dalszym i kolektorycznym zależy od potrzeb organizmu
- Reabsorpcja w tej strefie jest prowadzona przez α-interkalowane komórki, a wydzielanie przez główne komórki
- Hormonem regulującym reabsorpcję lub wydzielanie potasu w nerkach jest aldosteron
Hipokaliemia
- Przyczyny hipokaliemii:
- Niedostateczna podaż potasu
- Zwiększony napływ potasu do komórek
- Utrata potasu przez nerki
- Skutki hipokaliemii:
- Osłabienie mięśni szkieletowych
- Zaparcie
- Depresja oddechowa
- Arytmie sercowe
Nadmiar potasu w organizmie
-
Przyczyny hiperkaliemii:
- Zewnętrzna zmiana równowagi potasu
- Wewnętrzna zmiana równowagi potasu
-
Zewnętrzna zmiana równowagi potasu:
- Zmniejszenie wydalania potasu przez nerki
- Zwiększone wchłanianie potasu z pożywienia
-
Wewnętrzna zmiana równowagi potasu:
- Insulinooporność
- Kwasica
- Catecholaminy
- Hyperosmolarność
- Liza komórek
- Aktywność fizyczna
-
Skutki hiperkaliemii:
- Osłabienie mięśni szkieletowych
- Zaparcie
- Arytmie sercowe
- Zatrzymanie krążenia### Upośledzenie wydalania K+ przez nerki
-
Upośledzenie wydalania K+ przez nerki organiczne AKI lub PChN prowadzi do hiperkaliemii
-
Najczęściej spotykane, gdy GFR < 15 ml/min/1,73m2
-
Hiperkaliemia rzadko spotykana, chyba że występuje oliguria, podaż K+, rozpad tkanek, spadek aldosteronu
-
CKD > 900 G/l, leukocytoza > 70 G/l, hemoliza
Objawy hiperkaliemii
- Pojawiają się, gdy K+ > 7 mmol/l
- Zmniejszony stosunek ICF/ECF
- Upośledzone wyładowania nerwowe
- Osłabienie, parestezje, apatia
- Porażenie wiotkie, podobne do zespołu Guillain-Barré
- Zmiany EKG
Zmiany EKG
- Wzrost K+ średniego stopnia powoduje częściową depolaryzację
- Wzrost potencjału spoczynkowego do granicy z potencjałem czynnościowym
- Łatwa aktywowalność szybkich kanałów sodowych Nav1,5
- Wzrost pobudliwości oraz prędkości przewodzenia
- Przedwczesna repolaryzacja
Fizjologia wody
- Prawo elektroobojętności płynów ustrojowych (prawo Gamble’a)
- Prawo izoosmolarności
- Prawo izojonów
- Prawo izohydrii
- Osmolity efektywne: glukoza, Na+
- Osmolity nieefektywne: etanol, mocznik
Odwodnienie izotoniczne
- Etiopatogeneza: utrata izotonicznych płynów
- Przyczyny:
- Utrata płynów przez PP (biegunka, wymioty, utrata soku żołądkowego)
- Przetoki jelitowe
- Niedrożność porażenna jelit
- Odsysanie żołądka
- Skutki:
- Utrata płynów izotonicznych, bogatych w białko i elektrolity
- Utrata komórek morfotycznych
- Utrata płynów z równoczesną utratą elektrolitów
Get familiar with the concepts of water-electrolyte balance, including the calculation of pH and the causes of hypokalemia. Learn about the importance of potassium supply and the effects of pH changes on the body.
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