Fencl–Stewart approach: Telaah Kasus Gangguan Asam-Basa

Kiki MK Samsi, dr.,Sp.A, M.Kes

Pediatric Critical Care UnitTarumanagara University - Sumber Waras Hospital

30

Kasus 1 Seorang anak 2 thn, BB 10 kg:

Ileus obstruktifMuntah-muntah Dehidrasi beratpH 7.6, Kalium 2 meq/L, Cl 82 meq/L

TatalaksanaPasang NGT untuk DEKOMPRESIResusitasi cairan dengan RLBeri KCl untuk hipokalemia

58

Na+ = 140 mEq/LCl- = 82 mEq/L

SID = 58 mEq/LOH- = 58 mEq/L

Hypocloremic Alkalosis

The adverse effects of a severe alkalosis

Decreased myocardial contractility Arrhythmias Decreased cerebral blood flow Confusion Mental obtundation Neuromuscular excitability Impaired peripheral oxygen unloading

(due shift of oxygen dissociation curve to left).

The adverse effects of a severe alkalosis

Hypoventilation (due respiratory response to metabolic alkalosis)

Pulmonary microatelectasis (consequent on hypoventilation)

Increased ventilation-perfusion mismatch (as alkalosis inhibits hypoxic pulmonary vasoconstriction).

Na+ = 140 mEq/LCl- = 82 mEq/L

SID = 58 mEq/LOH- = 58 mEq/L

+

Hypocloremic Alkalosis

Na+ = 137 mEq/LCl- = 109 mEq/LLactat = 28 mEq/L

SID = 0 mEq/LOH- = 0 mEq/L

Ringer Lactat

Na+ = (140 + 137 mEq/L) : 2 = 138,5 mEq/L Cl- = ( 82 + 109 mEq/L) : 2 = 95,5 mEq/L

SID = 43 mEq/LOH- = 43 mEq/L

5843

Na+ = 140 mEq/LCl- = 95 mEq/L

SID = 45 mEq/LOH- = 45 mEq/L

+

Hypocloremic Acidosis

Na+ = 154 mEq/LCl- = 154 mEq/L

SID = 0 mEq/LOH- = 0 mEq/L

NaCl 0,9%

Na+ = (140 + 154 mEq/L) : 2 = 147 mEq/L Cl- = ( 82 + 154 mEq/L) : 2 = 118 mEq/L

SID = 29 mEq/LOH- = 29 mEq/L

5829

Kasus 2 Seorang anak 4 thn, BB 15 kg:

Sepsis pasca luka bakar BSA 20% (1 minggu)Nafas cepat, febrisPenurunan kesadaran

AGDpH 7,2; PCO2 30 mmHg; PO2 80 mmHgBE – 2; SaO2: 92%

The major effects of a metabolic acidosis

Depression of myocardial contractility Sympathetic overactivity (incl tachycardia,

vasoconstriction, decreased arrhythmia threshold)

Resistance to the effects of catecholamines Peripheral arteriolar vasodilatation Venoconstriction of peripheral veins Vasoconstriction of pulmonary arteries Shift of K+ out of cells -> hyperkalaemia

Terapi

Resusitasi cairan RL disertai: Bicarbonat natrikus:

Setuju atau Tidak Setuju

Penderita kejang-kejangHypocapnia

Recognised undesirable effects of bicarbonate administration

• Hypernatraemia • Hyperosmolality • Volume overload • Rebound or ‘overshoot’ alkalosis • Hypokalaemia • Hypercapnia • Impaired oxygen unloading due to left shift of the oxyhaemoglobin dissociation curve

Kasus 2 Elektrolit

Natrium : 160 mEq/LChlorida : 110 mEq/LKalium : 3.5

Lab lain:Darah rutin dalam batas normalProtein total 4.0 Albumin 1.2 g/dL

Kasus 2

Stong Ion Difference=[Na+]–[Cl–] = 160-110 = 50

ALBUMIN EFFECT = albumin 1.2 g/dL = HIPOALBUMIN UNMEASURED ION EFFECT ????

As. Laktat akibat gangguan perfusi dan oksigenisasi

Clinical InvestigationsStrong ions, weak acids and base excess: a simplified Fencl–Stewart approach to clinical acid–base disorders

D. A. Story*,1, H. Morimatsu2 and R. Bellomo2British Journal of Anaesthesia, 2004, Vol. 92, No. 1 54-60

Four variables

STANDARD BASE EXCESS (mmol /litre = meq / litre) from a blood gas

machine SODIUM–CHLORIDE EFFECT (meq / litre)

=[Na+]–[Cl–]–38ALBUMIN EFFECT (meq/ litre)

=0.25x[42–albumin (g/litre)] UNMEASURED ION EFFECT (meq / litre)

= standard base excess–(sodium–chloride effect)– albumin effect

Kasus 2

STANDARD BASE EXCESS from a blood gas machine = -2 mEq/L

SODIUM–CHLORIDE EFFECT (meq / litre)=[Na+]–[Cl–]–38 = 160-110-38 = 12 mEq/L

ALBUMIN EFFECT (meq/ litre)= 0.25 x [42–albumin (g/litre)] = 0.25 x [42-12 g/L] = 7.5 mEq/L

UNMEASURED ION EFFECT (meq / litre)= standard base excess–(sodium–chloride effect)–

albumin effect= -2 – 12 – 7.5 = -21.5

TATALAKSANA KASUS 2

Untuk memperbaiki asidosis: perbaiki oksigenisasi jaringan

Koreksi hypernatremia Koreksi hipoalbuminemia

Na Bicarbonat ????

Important points about the use of bicarbonate in metabolic acidosis

Ventilation must be adequate to eliminate the CO2 produced from bicarbonate

Bicarbonate therapy can increase extracellular pH only if the CO2 produced can be removed by adequate ventilation.

Indeed if hypercapnia occurs then as CO2 crosses cell membranes easily, intracellular pH may decrease even further with further deterioration of cellular function.

Important points about the use of bicarbonate in metabolic acidosis

Bicarbonate may cause clinical deterioration if tissue hypoxia is present

If tissue hypoxia is present, then the use of bicarbonate may be particularly disadvantageous due to increased lactate production (removal of acidotic inhibition of glycolysis) and the impairment of tissue oxygen unloading (left shift of ODC).

This means that with lactic acidosis or cardiac arrest then BICARBONATE THERAPY MAY BE DANGEROUS.

Important points about the use of bicarbonate in metabolic acidosis

Bicarbonate is probably not useful in most cases of high anion gap acidosis

As mentioned above lactic acidosis can get worse if bicarbonate is given. Studies have shown no benefit from bicarbonate in diabetic ketoacidosis. In these cases, the only indication for bicarbonate use is for the emergency management of severe

hyperkalaemia

NatriumClorideAlbuminUnmessurement ion

Lactat acidPhosphor

+