ELECTROLYTES & ELECTROLYTES & ACID-BASE HOMEOSTASISACID-BASE HOMEOSTASIS

(Keseimbangan Asam-Basa dan Elektrolit)(Keseimbangan Asam-Basa dan Elektrolit)

Oleh:Oleh:dr. Husnil Kadri, M.Kesdr. Husnil Kadri, M.Kes

PSPDG Departement PSPDG Departement Medical Faculty Of Andalas University Medical Faculty Of Andalas University

PadangPadang

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SodiumSodium

• Plays major role in maintaining ECF concentration (osmolality) and volume

• Main cation in ECF; primary determinant of osmolality (a measure of solute concentration)

• Important in generation and transmission of nerve impulses

• Important in acid-base balance

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HypernatremiaHypernatremia

• Hypernatremia due to– Water loss or– Sodium gain

• Hypernatremia results in– Hyperosmolality → water shifts out of cells →

cellular dehydration

• Primary protection against hypernatremia is thirst

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HypernatremiaHypernatremia

• Manifestations include thirst, lethargy, seizures, and coma

• Hypernatremia secondary to water deficiency often due to inability to get fluids

• Also due to deficiency in ADH

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HypernatremiaHypernatremia

• Management includes:– Treating the underlying cause– Hypotonic IV fluids if oral fluids cannot be

ingested – Administering diuretics (promotes excretion of

sodium)

• Serum sodium levels must be reduced gradually to avoid cerebral edema

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HyponatremiaHyponatremia

• Due to:– loss of Na-containing fluids, or – water excess (dilutional hyponatremia)

• Hyponatremia → hypoosmolality → water moves into cells

• Clinical manifestations include confusion, nausea, vomiting, seizures, and coma

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HyponatremiaHyponatremia

• If caused by water excess, fluid restriction is needed

• If severe symptoms (seizures) occur, small amount of intravenous hypertonic saline solution (3% NaCl) is given

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HyponatremiaHyponatremia

• If associated with abnormal fluid loss (diarrhea, polyuria, etc.):

fluid replacement with Na-containing solution (eg.Normal saline [0.9% NaCl])

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PotassiumPotassium

• Potassium major ICF cation

• Potassium is necessary for– Transmission and conduction of nerve

impulses – Normal cardiac rhythms– Skeletal muscle contraction– Acid-base balance

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PotassiumPotassium

• Critical to action membrane potential

– Sources of potassium • Fruits and vegetables (bananas and

oranges)• Salt substitutes • Potassium medications (PO, IV)• Stored blood

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HyperkalemiaHyperkalemia

• Causes– Increased retention

• Renal failure• Potassium sparing diuretics

– Increased intake

– Mobilization from ICF • Tissue destruction • Acidosis

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HyperkalemiaHyperkalemia

• Clinical Manifestations :– Skeletal muscles weak or paralyzed

– Ventricular fibrillation or cardiac standstill

– Abdominal cramping or diarrhea

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Nursing Management of Nursing Management of HyperkalemiaHyperkalemia

• Eliminate oral and parenteral K intake

• Increase elimination of K (diuretics, dialysis)

• Force K from ECF to ICF with IV insulin (or sodium bicarbonate if hyperkalemia is due to acidosis)

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HypokalemiaHypokalemia

• Causes

– Increased loss

• Certain diuretics

• GI losses

• Movement into cells

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HypokalemiaHypokalemiaClinical ManifestationsClinical Manifestations

• Potentially lethal ventricular arrhythmias

• Increased digoxin toxicity in those taking the drug

• ECG changes

• Skeletal muscle weakness and paralysis

• Muscle cell breakdown

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HypokalemiaHypokalemiaClinical ManifestationsClinical Manifestations

• Decreased GI motility

• Altered airway responsiveness

• Impaired regulation of arterial blood flow

• Diuresis

• Hyperglycemia

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Kalsium & FosforKalsium & Fosfor

• Keduanya membentuk garam appatite didalam tulang & gigi (80-90%).

• Absorpsi paling baik jika perbandingan dalam lumen usus Ca : P = 1 : 1 s/d 1 : 3

• Bila perbandingan > 3, maka absorpsi Ca terhambat (Rachitis).

• Makanan penyebabnya disebut rachitogenik

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Interaksi yang MenghambatInteraksi yang Menghambat

• Beras mengandung asam fitat (P) sehingga mengikat Ca membentuk Ca-fitat.

• Sayuran & buah yang mengandung asam oksalat juga akan menghambat absorpsi Ca.

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Fungsi CaFungsi Ca

• Penggumpalan darah

• Kontraksi otot

• Penghantar stimulus saraf

• Aktifitas enzim tertentu

• Membentuk hidroksiapatit pada tulang dan gigi

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Fungsi PFungsi P

• Ikatan fosfat berenergi tinggi ATP, ADP, kreatin-P, PEP, dll.

• Komponen membran sel fosfolipid

• Membentuk hidroksiapatit pada tulang dan gigi

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Defisiensi CaDefisiensi Ca

• Rickets pada anak-anak

• Osteomalacia (osteoporosis) pada dewasa

• Tetani / kejang

• Postmenopause (estrogen rendah)

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Defisiensi PDefisiensi P

• Gangguan absorpsi di usus

• Ekskresi berlebihan melalui ginjal

• Sindrom Milkman

• Sindrom de Toni Fanconi

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Klor (Cl)Klor (Cl)

• Komponen garam NaCl.

• Asam-basa (Chloride shift).

• Pengaturan osmotik.

• Komponen HCl lambung.

• Ekskresi melalui keringat.

• Defisiensi Cl menyebabkan alkalosis metabolik akibat muntah proyektil.

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MagnesiumMagnesium

• Terdapat dalam semua jaringan tubuh.

• Komponen ATP.

• Berperan dalam sintesis protein.

• Berperan dalam kontraksi otot.

• Absorpsi usus meningkat bila terdapat Ca, P, & protein.

• Ekskresi melalui ginjal.

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Defisiensi MagnesiumDefisiensi Magnesium

• Terjadi pada alkoholisme/malnutrisi.

• Mempengaruhi sistem:

1. kardiovaskuler

2. ginjal

3. neuromuskuler

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Fluor (F)Fluor (F)

• Komponen jaringan keras, tu gigi.• Melindungi email gigi.• Fluor bersifat racun thd enolase (glikolisis)• Air PAM mengandung fluor 1 -2 ppm.• Defisiensi fluor --> karies dentis.• Kelebihan fluor --> fluorosis (mottled enamel)

= cekungan-cekungan kuning kecoklatan pada email & dentin

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• Acidosis: plasma pH– Protein damage– CNS depression

• Alkalosis: plasma pH– Hyperexcitability– CNS & heart

• Buffers: HCO3- & proteins

• H+ input: diet & metabolic

• H+ output: lungs & kidney

Acid/Base Homeostasis: OverviewAcid/Base Homeostasis: Overview

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Acid/Base Homeostasis: OverviewAcid/Base Homeostasis: Overview

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• Buffers

–Blood seconds

–Intracellular minutes

• Lung hours

• Kidneys days

Removing Acid or Base

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• pH = pKa + log [HCO3-]/[H2CO3]

• pH = pKa + log [HCO3-]/0.03 x PCO2

• 7.4 = 6.1 + log 20 / 1

• 7.4 = 6.1 + 1.3

• Plasma pH equals 7.4 when buffer ratio is 20/1

• The solubility constant of CO2 is 0.03

Henderson-Hasselbalch equationHenderson-Hasselbalch equation

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Physiological Buffer SystemsPhysiological Buffer Systems

• The respiratory system regulation of acid-base balance is a physiological buffering system

• There is a reversible equilibrium between:– Dissolved carbon dioxide and water– Carbonic acid and the hydrogen and

bicarbonate ions

CO2 + H2O H2CO3 H+ + HCO3¯

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Physiological Buffer SystemsPhysiological Buffer Systems

• During carbon dioxide unloading, hydrogen ions are incorporated into water

• When hypercapnia or rising plasma H+ occurs:– Deeper and more rapid breathing expels more

carbon dioxide– Hydrogen ion concentration is reduced

• Alkalosis causes slower, more shallow breathing, causing H+ to increase

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Acid-base disturbancesAcid-base disturbances

• Plasma pH may be affected by a change in either the [bicarbonate] or the PCO2:

– When the primary change is in the PCO2, the disturbance is called respiratory;

– When it is the [bicarbonate], it is called metabolic:

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Acid-base changes in Acid-base changes in acidosis and alkalosisacidosis and alkalosis

Acid-base Disturbance pH HCO3- PCO2

Respiratory acidosis Respiratory alkalosis Metabolic acidosis

Metabolic alkalosis

Thicker arrows indicate primary disorder

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• Metabolic Acidosis: Diabetic ketoacidosis, diarrhea

• Metabolic Alkalosis: antacid, vomiting (will loose Cl too)

• Respiratory Acidosis: Hypoventilation, pulmonary edema, narcotic, chronic bronchitis

• Respiratory Alkalosis: Hyperventilation, asthma, pneumoni, brain injury, anxiety

Clinical Causes …

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CompensationCompensation

• The purpose of the compensation is to return the blood pH to normal

• The change in the PCO2 in the metabolic disorders represents the lung’s role in compensation

• The change in the bicarbonate level represents the kidney’s attempt to compensate for the respiratory acidosis or alkalosis

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Metabolic and Respiratory Acid-Base Changes in Blood

pH pCO2 HCO3-

Acidosis

1. Acute metabolic N 2. Compensated metabolic N 3. Acute respiratory N4. Compensated respiratory N

Alkalosis

1. Acute metabolic N 2. Chronic metabolic 3. Acute respiratory N4. Compensated respiratory N =decreased; =increased; N=normal

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Normal values for arterial blood gases

Blood Gas Parameter Parameter Reported and Symbol Used

Normal Value

Carbon dioxide tension*

PCO2 35 – 45 mm Hg (average, 40)

Oxygen tension* PO2 80 – 100 mm Hg

Oxygen percent saturation

SO2 97

Hydrogen ion concentration*

pH 7.35 – 7.45

Bicarbonate HCO3- 22 – 26 mmol/L

Arterial Blood Gases (ABG)

* Indicates measured parameter Normal values may differ slightly in exams

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KepustakaanKepustakaan

• Booth, HD. Integrative Physiology II: Fluid and electrolyte balance.PPt. 2004

• Hale, J. Fluid and electrolytes. PPT. 2009.• Hardjasasmita, P. Ikhtisar: biokimia dasar B. Balai Penerbit

FKUI. Jakarta: 50 - 6. 1993.• Ivkovic, A ., Dave, R. Renal review. PPT. 2007• Mineral 2007. website.• Rashid, FA. Respiratory mechanism in acid-base homeostasis. PPT. 2005.