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ACID-BASE DISORDERS

ACID-BASE DISORDERS. I.M.SIALA, MD. Acid-base disorders. Blood Pressure. Pulse. Proper Cell Function. Temperature. Hemoglobin. Ca, K, …. Hydrogen Ion Concentration. NORMAL RANGE. Hydrogen Ion Concentration. may change out of the normal range:

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ACID-BASE DISORDERS

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  1. ACID-BASE DISORDERS I.M.SIALA, MD

  2. Acid-base disorders Blood Pressure Pulse Proper Cell Function Temperature Hemoglobin Ca, K, … Hydrogen Ion Concentration NORMAL RANGE

  3. Hydrogen Ion Concentration may change out of the normal range: 1- physiological: during daily metabolism 2- Pathological: e.g diabetic keto-acidosis If not corrected  major cell dysfunction

  4. pH and H+ concentration • The blood pH represents the H+ concentration • [ pH = the negative log of H+]. •  (H+) concentration   pH (acidosis) •  (H+) concentration   pH (alkalosis) • The body will try to restore the pH to normal “Compensatory mechanisms”. • Complete (if pH returns to normal range)or • Incomplete (if pH approches normal ranges but still abnormal.

  5. Compensatory mechanisms • Body buffers • CO2-bicarbonate system H+ + HCO3 H2CO3 H2O + CO2 • Hemoglobin • Hydroxyapatite REGULATED BY LUNG REGULATED BY KIDNEY

  6. Lungs • Hyperventilation  wash out CO2 • Hypoventilation  retain CO2 • Response is immediate • Kidneys • Proximal tubule: • All HCO3 is filtered  body reabsorb ONLY its requirements  rest lost in urine • Distal tubule • Nais reabsorbed in exchange of K or H+. •  KH+ is excreted more  alkalosis •  KH+ is excreted less  acidosis • Kidney needs 6 – 12 hours to start its compensating mechanisms.

  7. + H+ + HCO3 H2CO3 H2O CO2   Alkalosis Acidosis

  8. Acid base disturbances Arterial blood sample Normal values • A 2 ml syringe • Heparinized • Radial/ femoral artery • Draw 1 ml of blood • Send for analysis immediately or send in an ice pack Heparinized syringe Radial artery

  9. Acid-base disorders • Acidosis • Alkalosis

  10. ACIDOSIS

  11. ALKALI HCO3 ACID PaCO2 ACID PaCO2 ALKALI HCO3 ACIDOSIS 7.36 7 .44

  12. CO2 HCO3 ACID PaCO2 ALKALI HCO3 METABOLIC ACIDOSIS COMPANSATEDMETABOLIC ACIDOSIS HCO3 CO2 HCO3 CO2 CO2 7.36 7 .44

  13. CO2 HCO3 CO2 CO2 HCO3 HCO3 HCO3 ACID PaCO2 ALKALI HCO3 RESPIRATORY ACIDOSIS COMPANSATEDRESPIRATORY ACIDOSIS CO2 CO2 HCO3 HCO3 CO2 CO2 7.36 7 .44

  14. ALKALOSIS

  15. ALKALI HCO3 ACID PaCO2 ACID PaCO2 ALKALI HCO3 ALKALOSIS 7.36 7 .44

  16. CO2 HCO3 ACID PaCO2 ALKALI HCO3 RESPIRATORY ALKALOSIS COMPANSATEDRESPIRATORY ALKALOSIS CO2 CO2 HCO3 HCO3 HCO3 7.36 7 .44

  17. CO2 HCO3 CO2 CO2 HCO3 HCO3 HCO3 ACID PaCO2 ALKALI HCO3 METABOLIC ALKALOSIS COMPANSATEDMETABOLIC ALKALOSIS CO2 CO2 CO2 HCO3 HCO3 HCO3 7.36 7 .44

  18. Acid-base disorders • Acidosis • Metabolic • Respiratory • Alkalosis • Metabolic • Respiratory

  19. Metabolic acidosis • a pH< 7.36 due to a reduction in plasma HCO3-. • PaCO2 will  secondary to hyperventilation . Definition:

  20. ANION GAP Unmeasured Anions: albumin, phosphate, sulphate, lactate, ketoacids, others. Unmeasured Cations: calcium, Mg, globulins, K. + - Anion Gap HCO3_ Na+ Cl- “Anion gap represents the difference between readily measured anions and cations” Anion gap = Plasma Na+ - (Cl- + HCO3-) N= 8 – 14 mmol\l

  21. Aetiology of metabolic acidosis Increased Anion gap acidosis: Lactic acidosis Ketoacidosis Diabetic Alcohol Toxins Methanol Ethylene glycol Salicylate UraemiaARF CRF + - Anion Gap Anion Gap HCO3_ Na+ Cl- Normal Anion gap acidosis Hyperchloremic acidosis GIT HCO3- loss Diarrhea Pancreatic drainage Ureterosigmoidostomy Renal tubular acidosis Drugs CA inhibitors + HCO3_ - Anion Gap Na+ Cl-

  22. Metabolic acidosis Clinical picture A- due to acidosis: • Deep & rapid breathing, Kussmaul`s breathing. • Altered state of consciousness • Hypotension in severe cases B- Due to primary disease

  23. Arterial blood gas findings • pH low<7.36 or in the lower limit of normal • HCO3- low <21 mmol\l • PaCO2 low < 35 mmHg

  24. Treatment • A- treat the underlying disease. • B- control the acidosis; • Correct fluid & electrolyte disturbances • Indications of parentral Na HCO3: • in severe acidosis pH <7.1 • GI loss or RTA HCO3 can be given as replacement therapy, usually orally.

  25. RESPIRATORY ACIDOSIS Definition: • a pH < 7.36 due to • increased retention of CO2 as a result of  alveolar ventilation

  26. Respiratory Physiology

  27. Aetiologya-Acute b-Chronic • Airway obstruction • Foreign body • Laryngospasm • Severe bronchospasm • Respiratory center depression • Morphine overdose • CVA • Trauma • Neuromuscular • High cervical cord resection • Myasthenia gravis • GullianBarre syndrome • Organophosphorus • Restrictive defects • Pneumothorax • Flail chest • Cardiac Arrest & sever pulmonary oedema • COAD • Neuromuscular • MS • Muscular dystrophies • Motor neuron disease • Diaphragmatic paralysis • Chest wall deformities • Kyphoscolisis • Ankylosingspodylitis • Primary alveolar hypoventilation-Obesity

  28. RESPIRATORY ACIDOSISClinical Picture: • A-Features of CO2 retention • Headache • Altered level of consciousness(severe) • Myoclonus &hyperreflexia • Astrexis • Central cyanosis • Collapsing pulse • Warm periphery • Papilloedema • B-Features of the underlying illness.

  29. RESPIRATORY ACIDOSIS

  30. Respiratory failure • Type I respiratory failure: PaO2 < 60 mmHg with normal or low PaCO2 • Type II respiratory failure: PaCO2 >55 mmHg irrespective of O2 value.

  31. Treatment • A- Treat the underlying cause • B- Treat carbon dioxide retention • Naloxone if Narcotic overdose is suspected • Low oxygen concentration • Mechanical ventilation in severe cases

  32. METABOLIC ALKALOSIS Definition: • a pH > 7.44 due to an increase in plasma HCO3 • PaCO2 may  . • In normal renal function it is rare, why?

  33. Aetiology • Loss of H+, Cl, & Na Associated with EC volume depletion • GIT loss • Vomiting • Aspiration of gastric contents • Loss through kidney • Diuretics • Carbenicillin, penicillins • K depletion • Mineralocorticoid excess • Bartter`s syndrome • 1o & 2o Aldosteronism • Cushing syndrome • Adrenal enzyme deficiency • Hyperreninism • Exogenous mineralocorticoids • Carbenoxolone • Exogenous alkali • NaHCO3(Baking soda) • Blood transfusions-citrate • Antacids

  34. METABOLIC ALKALOSISClinical picture • A- Features of underlying illness • B- Features related to metabolic alkalosis; • TetanyDue to acute fall in ionized Ca level • Manifest • Latent • Chvostok sign Traussau sign • Altered state of consciousness

  35. Arterial blood gas picture • pH >7.44 or in the Upper limit of normal in compensated cases • HCO3 >28 mmol\l • PaCO2 >45 mmHg or normal

  36. Treatment • A- Correct the metabolic alkalosis; • Correct EC volume depletion  enhance HCO3 excretion • B- Treat the underlying cause; • mineralocorticoid excess • Correct  K

  37. RESPIRATORY ALKALOSIS Definition: • pH>7.44 due to CO2 washout as a result of hyperventilation

  38. Aetiology • Hypoxia • Voluntary • CNS Disease • CVA • Infections • Trauma • Tumours • Drugs Aspirin • Hepatic Failure • Gram Negative Septicaemia • Heat Exposure • Mechanical overventilation

  39. Clinical picture • A- features of the underlying cause. • Anxiety • B- Features of Alkalosis; • Tetany • Parasthesia, numbness around the mouth, tingling in hands & feet • Tetany

  40. Arterial blood gas • pH high >7.44 • PaCO2 low<35 mmHg • HCO3 normal or low<21 mmol\l

  41. Treatment • A- Treat the underlying cause • B- Supportive measures; • Rebreathing in a paper bag in Hyperventilation syndrome + sedation

  42. Summary

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