serum electrolytes & arterial blood gases dr. mohammed k. el-habil msc. pharmacology 2014

Serum Electrolytes & Arterial blood gases

Dr. Mohammed K. El-HabilDr. Mohammed K. El-Habil

MSC. PharmacologyMSC. Pharmacology

20142014

Electrolytes

Solutes that form ions (electrical Solutes that form ions (electrical charge)charge) Cation (+)Cation (+) Anion (-)Anion (-)

Major body electrolytes: Major body electrolytes: Na+, K+, Ca++, Mg++Na+, K+, Ca++, Mg++ Cl-, HCOCl-, HCO33-, HPO-, HPO44--, SO--, SO44--

Electrolyte Distribution

Major ICF ionsMajor ICF ions K+ K+ HPOHPO44----

Major ECF ionsMajor ECF ions NA+ NA+ CL-, HCOCL-, HCO33--

Electrolyte Normal Values

Sodium 135 – 145 mEq/LSodium 135 – 145 mEq/LPotassium 3.5 – 5 mEq/LPotassium 3.5 – 5 mEq/LPhosphrus 1.8-2.3 mEq/LPhosphrus 1.8-2.3 mEq/LChloride 98 – 106 mEq/LChloride 98 – 106 mEq/LCalcium 9 – 11 mEq/LCalcium 9 – 11 mEq/LUrea 20 – 40 mEq/LUrea 20 – 40 mEq/LCreatinine 0.7 – 1.2 mEq/LCreatinine 0.7 – 1.2 mEq/LMagnesium: 1.5 – 3 mEq/LMagnesium: 1.5 – 3 mEq/LCO2 22 – 26 mEq/LCO2 22 – 26 mEq/LBicarbonate 24-30 mEq/L Bicarbonate 24-30 mEq/L

Hypernatremia

NaNa++ is more than is more than 135 – 145 mEq/L135 – 145 mEq/LManifestationsManifestations

Thirst, lethargy, agitation, seizures, and Thirst, lethargy, agitation, seizures, and coma, shrinking of brain.coma, shrinking of brain.

Similar to :Similar to :Central or nephrogenic diabetes Central or nephrogenic diabetes insipidus (DI).insipidus (DI).

In treatment, reduce NaIn treatment, reduce Na++ levels levels gradually to avoid cerebral edemagradually to avoid cerebral edema

Hyponatremia

Results from loss of sodium-containing Results from loss of sodium-containing fluidsfluids

Sweat, diarrhea, emesis,..etc.Sweat, diarrhea, emesis,..etc.Or from water excessOr from water excess

Inefficient kidneysInefficient kidneysDrowning, excessive intakeDrowning, excessive intake

ManifestationsManifestationsConfusion, nausea, vomiting, seizures, Confusion, nausea, vomiting, seizures, Brain Brain edemaedema and coma and coma

Hyperkalemia

Serum Potassium greater than 5.5 Serum Potassium greater than 5.5 mEq/LmEq/L- More dangerous than hypokalemia More dangerous than hypokalemia

because cardiac arrest is frequently because cardiac arrest is frequently associated with high serum K+ levelsassociated with high serum K+ levels

Hyperkalemia

ManifestationsManifestationsWeak or paralyzed skeletal musclesWeak or paralyzed skeletal musclesVentricular fibrillation or cardiac blockVentricular fibrillation or cardiac blockAbdominal cramping or diarrheaAbdominal cramping or diarrhea

Hypokalemia

Low serum potassium caused byLow serum potassium caused byAbnormal losses of KAbnormal losses of K++ via the kidneys via the kidneys or gastrointestinal tractor gastrointestinal tract Drugs: DiureticsDrugs: DiureticsMagnesium deficiencyMagnesium deficiencyMetabolic alkalosis enhance H-K Metabolic alkalosis enhance H-K pumping & entrance of K intracellular . pumping & entrance of K intracellular .

Hypokalemia

ManifestationsManifestationsMost serious are cardiac arrhythemiasMost serious are cardiac arrhythemiasSkeletal muscle weaknessSkeletal muscle weaknessWeakness of respiratory musclesWeakness of respiratory musclesDecreased gastrointestinal motilityDecreased gastrointestinal motility

Calcium

Obtained from ingested foodsObtained from ingested foodsMore than 99% combined with More than 99% combined with phosphorus and concentrated in phosphorus and concentrated in skeletal systemskeletal systemInverse relationship with phosphorusInverse relationship with phosphorus

Otherwise…Otherwise…

Calcium

Balance controlled byBalance controlled byParathyroid hormoneParathyroid hormoneCalcitoninCalcitoninVitamin D/IntakeVitamin D/Intake

Bone used as reservoirBone used as reservoir

Hypercalcemia

High serum calcium levels more than High serum calcium levels more than 9 – 11 mEq/L 9 – 11 mEq/L caused bycaused by

Hyperparathyroidism (two thirds of Hyperparathyroidism (two thirds of cases)cases)Malignancy (parathyroid tumor)Malignancy (parathyroid tumor)Vitamin D overdoseVitamin D overdoseProlonged mobilizationProlonged mobilization

Hypercalcemia

ManifestationsManifestationsDecreased memoryDecreased memoryConfusionConfusionDisorientationDisorientationFatigueFatigueConstipation Constipation

Treatment

Excretion of Ca with loop diureticExcretion of Ca with loop diureticHydration with isotonic saline Hydration with isotonic saline infusioninfusionSynthetic calcitoninSynthetic calcitonin

Hypocalcemia

Low serum Ca levels caused byLow serum Ca levels caused byDecreased production of PTHDecreased production of PTHAcute pancreatitis Acute pancreatitis Multiple blood transfusions Multiple blood transfusions AlkalosisAlkalosisDecreased intakeDecreased intake

Hypocalcemia

ManifestationsManifestationsWeakness/TetanyWeakness/TetanyPositive Trousseau’s or Positive Trousseau’s or Chvostek’s signChvostek’s signLaryngeal stridorLaryngeal stridorDysphagiaDysphagiaTingling around the Tingling around the mouth or in the extremities mouth or in the extremities

Treatment

Treat causeTreat causeOral or IV calcium supplementsOral or IV calcium supplements

Not IM to avoid local reactionsNot IM to avoid local reactions

Treat pain and anxiety to prevent Treat pain and anxiety to prevent hyperventilation-induced respiratory hyperventilation-induced respiratory alkalosisalkalosis

Phosphate

Primary anion in ICFPrimary anion in ICFEssential to function of muscle, red Essential to function of muscle, red blood cells, and nervous systemblood cells, and nervous systemDeposited with calcium for bone and Deposited with calcium for bone and tooth structuretooth structure

Hyperphosphatemia

High serum POHigh serum PO4433 (more than (more than1.8-2.3 1.8-2.3

mEq/L) mEq/L) caused by: caused by: Acute or chronic renal failureAcute or chronic renal failureChemotherapyChemotherapyExcessive ingestion of phosphate or Excessive ingestion of phosphate or vitamin Dvitamin D

Manifestations Manifestations Calcified deposition: joints, arteries, skin, Calcified deposition: joints, arteries, skin, kidneys, and corneaskidneys, and corneasNeuromuscular irritability and tetanyNeuromuscular irritability and tetany

Hypophosphatemia

Low serum POLow serum PO4433 caused by caused by

Malnourishment/malabsorptionMalnourishment/malabsorptionAlcohol withdrawalAlcohol withdrawalUse of phosphate-binding antacidsUse of phosphate-binding antacidsDuring parenteral nutrition with During parenteral nutrition with inadequate replacementinadequate replacement

Hypophosphatemia

ManifestationsManifestationsCNS depressionCNS depressionConfusion Confusion Muscle weakness and painMuscle weakness and painDysrhythmias Dysrhythmias Cardiomyopathy Cardiomyopathy

Magnesium

50% to 60% contained in bone50% to 60% contained in boneCoenzyme in metabolism of protein and Coenzyme in metabolism of protein and carbohydrates carbohydrates Factors that regulate calcium balance appear to Factors that regulate calcium balance appear to influence magnesium balance.influence magnesium balance.Acts directly on myoneural junction Acts directly on myoneural junction Important for normal cardiac functionImportant for normal cardiac function

Hypermagnesemia

High serum Mg more than High serum Mg more than 1.5 – 3 mEq/L 1.5 – 3 mEq/L caused caused byby

When renal insufficiency or failure is presentWhen renal insufficiency or failure is presentManifestationsManifestations

Lethargy or drowsinessLethargy or drowsinessNausea/vomitingNausea/vomitingImpaired reflexes***Impaired reflexes***Respiratory and cardiac arrestRespiratory and cardiac arrest

Hypomagnesemia

ManifestationsManifestationsConfusionConfusionHyperactive deep tendon reflexesHyperactive deep tendon reflexesTremorsTremorsSeizures Seizures Cardiac dysrhythmias Cardiac dysrhythmias

Electrolytes

Electrolytes

Renal Function

Arterial blood gasesArterial blood gases

Interpretation of ABGs

Diagnosis in six stepsDiagnosis in six stepsEvaluate pH Evaluate pH Analyze PaCOAnalyze PaCO22

Analyze HCOAnalyze HCO33

Determine if Balanced or UnbalancedDetermine if Balanced or UnbalancedDetermine if CODetermine if CO22 or HCO or HCO33

matches the matches the alterationalterationDecide if the body is attempting to Decide if the body is attempting to compensatecompensate

Interpretation of ABG

1.1. pH over balancepH over balance2.2. PaCO2 = “respiratory” balancePaCO2 = “respiratory” balance3.3. HC03- = “metabolic” balanceHC03- = “metabolic” balance4.4. If all three normal = balancedIf all three normal = balanced5.5. Match direction. e.g., if pH and PaCO2 are Match direction. e.g., if pH and PaCO2 are

both acidotic, then primary respiratory both acidotic, then primary respiratory acidosisacidosis

6.6. Together, CO2 & HCO3 act as metabolic & Together, CO2 & HCO3 act as metabolic & respiratory buffer like:respiratory buffer like:

7.7. H2O + CO2 ˭ ˭ ˭ H2CO3 ˭ ˭ ˭ HCO3 + H H2O + CO2 ˭ ˭ ˭ H2CO3 ˭ ˭ ˭ HCO3 + H

Metabolic Acid-base Disorders: Metabolic Acid-base Disorders: Some Clinical CausesSome Clinical Causes

METABOLIC ACIDOSISMETABOLIC ACIDOSIS ↓↓HCOHCO33-- & & ↓↓ pH pH

- lactic acidosis; ketoacidosis; drug poisonings (e.g., aspirin, ethylene - lactic acidosis; ketoacidosis; drug poisonings (e.g., aspirin, ethylene glycol, methanol)glycol, methanol)

-- diarrhea; some kidney problems (e.g., renal tubular diarrhea; some kidney problems (e.g., renal tubular acidosis, interstitial nephritis)acidosis, interstitial nephritis)

METABOLIC ALKALOSISMETABOLIC ALKALOSIS ↑↑ HCO HCO33-- & & ↑↑ pHpH

contraction alkalosis, diuretics, corticosteroids, gastric suctioning, contraction alkalosis, diuretics, corticosteroids, gastric suctioning, vomiting vomiting

hyperaldosterone state (e.g., Cushing’s syndrome, Bartter’s syndrome, hyperaldosterone state (e.g., Cushing’s syndrome, Bartter’s syndrome, severe Ksevere K++ depletion) depletion)

RESPIRATORY ACIDOSISRESPIRATORY ACIDOSIS ↑↑PaCOPaCO2 2 & & ↓↓ pHpH Central nervous system depression (e.g., drug overdose)Central nervous system depression (e.g., drug overdose)

Chest bellows dysfunction (e.g., Guillain-Barré syndrome, Chest bellows dysfunction (e.g., Guillain-Barré syndrome, myasthenia gravis) myasthenia gravis)

Disease of lungs and/or upper airway (e.g., chronic obstructive Disease of lungs and/or upper airway (e.g., chronic obstructive lung lung disease, severe asthma attack, severe pulmonary edema)disease, severe asthma attack, severe pulmonary edema)

RESPIRATORY ALKALOSISRESPIRATORY ALKALOSIS ↓↓PaCOPaCO2 2 && ↑↑ pH pH

Hypoxemia (includes altitude)Hypoxemia (includes altitude)

AnxietyAnxiety

SepsisSepsis

Any acute pulmonary insult (e.g., pneumonia, mild asthma Any acute pulmonary insult (e.g., pneumonia, mild asthma attack, early pulmonary edema, pulmonary embolism)attack, early pulmonary edema, pulmonary embolism)

Respiratory Acid-base Disorders:Respiratory Acid-base Disorders:Some Clinical CausesSome Clinical Causes

Acid-Base Disorders

Acid-Base Disorders

Interpretation of ABGs

pH 7.26 Normal (7.35-7.45)pH 7.26 Normal (7.35-7.45)PaCOPaCO22 67 mm Hg (35-45) 67 mm Hg (35-45)

PaOPaO22 47 mm Hg (80-100) 47 mm Hg (80-100)

HCOHCO33 26 mEq/L (22-26) 26 mEq/L (22-26)What is this?What is this?

Respiratory acidosisRespiratory acidosis

Interpretation of ABGs

pH 7.18pH 7.18PaCOPaCO22 38 mm Hg 38 mm Hg

PaOPaO22 70 mm Hg 70 mm Hg

HCOHCO33 15 mEq/L 15 mEq/L

What is this?What is this?

Metabolic acidosi Metabolic acidosi