ACIDBASE DISORDERS I M SIALA MD Acidbase disorders

ACID-BASE DISORDERS I. M. SIALA, MD

Acid-base disorders Bl oo d Pr e e ss s ul ur e P Proper Cell Function Temperature n o I on n ti e g tra o r n d y ce H on C Hemoglobin Ca NORMAL RANGE , K , …

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

p. H and H+ concentration o The blood p. H represents the H+ concentration o [ p. H = the negative log of H+]. o o (H+) concentration p. H (alkalosis) o The body will try to restore the p. H to normal “Compensatory mechanisms”. n Complete (if p. H returns to normal range)or n Incomplete (if p. H approches normal ranges but still abnormal.

Compensatory mechanisms o Body buffers n CO 2 -bicarbonate system REGULATED BY KIDNEY REGULATED BY LUNG H+ + HCO 3 H 2 O + CO 2 n n Hemoglobin Hydroxyapatite

o Lungs n n Hyperventilation wash out CO 2 Hypoventilation retain CO 2 n Response is immediate o Kidneys n Proximal tubule: o n All HCO 3 is filtered body reabsorb ONLY its requirements rest lost in urine Distal tubule o Na is reabsorbed in exchange of K or H+. o K H+ is excreted more alkalosis o K H+ is excreted less acidosis n Kidney needs 6 – 12 hours to start its compensating mechanisms.

H+ + HCO 3 H 2 O + CO 2 Alkalosis Acidosis

Acid base disturbances Arterial blood sample • 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 Normal values PH 7. 36 -7. 44 7. 4 +. 04 Pa. CO 2 35 – 45 mm. Hg 40 + 5 HCO 3 21 – 28 mmoll 25 +3 Pa. O 2 83 – 108 mm. Hg

Acid-base disorders o. Acidosis o. Alkalosis

ACIDOSIS

ALKALI HCO 3 ACID Pa. CO 2 7. 36 7. 44

COMPANSATED ACIDOSIS METABOLIC ACIDOSIS O 3 C H CO 2 HCO 3 CO 2 ALKALI HCO 3 ACID Pa. CO 2 7. 36 7. 44

COMPANSATED RESPIRATORY ACIDOSIS O 3 C H CO 2 HCO 3 CO 2 ALKALI HCO 3 ACID Pa. CO 2 O 3 C H 7. 36 7. 44

ALKALOSIS

ACID 2 Pa. CO ACID ALKALI HCO 3 Pa. CO 2 7. 36 7. 44

COMPANSATED RESPIRATORY ALKALOSIS CO 2 HCO 3 HC O 3 ACID Pa. CO 2 ALKA LI HCO 3 7. 36 7. 44

COMPANSATED ALKALOSIS METABOLIC ALKALOSIS CO 2 CO 2 HCO 3 HC O 3 ACID Pa. CO 2 ALKA LI HCO 3 7. 36 7. 44

Acid-base disorders o. Acidosis n Metabolic n Respiratory o. Alkalosis n Metabolic n Respiratory

Metabolic acidosis Definition: o a p. H< 7. 36 due to a reduction in plasma HCO 3 -. o Pa. CO 2 will secondary to hyperventilation.

ANION GAP Unmeasured Cations: calcium, Mg, globulins, K. Anion Gap _ Na+ HCO 3_ Unmeasured Anions: albumin, phosphate, sulphate, lactate, ketoacids, others. Cl- “Anion gap represents the difference between readily measured anions and cations” Anion gap = Plasma Na+ - (Cl- + HCO 3 -) N= 8 – 14 mmoll

Aetiology of metabolic acidosis Increased Anion gap acidosis: Lactic acidosis Ketoacidosis Toxins Uraemia Diabetic Alcohol Methanol Ethylene glycol Salicylate ARF CRF Anion Gap HCO 3_ Na+ Cl- Normal Anion gap acidosis Hyperchloremic acidosis GIT HCO 3 - loss Diarrhea Pancreatic drainage Ureterosigmoidostomy Renal tubular acidosis Drugs CA inhibitors HCO 3_ Anion Gap Na+ Cl-

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

Arterial blood gas findings o p. H o HCO 3 o Pa. CO 2 low<7. 36 or in the lower limit of normal low <21 mmoll low < 35 mm. Hg

Treatment o A- treat the underlying disease. o B- control the acidosis; n Correct fluid & electrolyte disturbances n Indications of parentral Na HCO 3: o in severe acidosis p. H <7. 1 n GI loss or RTA HCO 3 can be given as replacement therapy, usually orally.

RESPIRATORY ACIDOSIS Definition: o a p. H < 7. 36 due to o increased retention of CO 2 as a result of alveolar ventilation

Respiratory Physiology

Aetiology a-Acute b-Chronic o Airway obstruction o COAD n Foreign body n Laryngospasm n Severe bronchospasm o Respiratory center depression n Morphine overdose n CVA n Trauma o Neuromuscular n High cervical cord resection n Myasthenia gravis n Gullian Barre syndrome n Organophosphorus o Restrictive defects n Pneumothorax n Flail chest o Cardiac Arrest & sever pulmonary oedema o Neuromuscular n n MS Muscular dystrophies Motor neuron disease Diaphragmatic paralysis o Chest wall deformities o n Kyphoscolisis n Ankylosing spodylitis Primary alveolar hypoventilation-Obesity

RESPIRATORY ACIDOSIS Clinical Picture: o n n n n o A-Features of CO 2 retention Headache Altered level of consciousness(severe) Myoclonus &hyperreflexia Astrexis Central cyanosis Collapsing pulse Warm periphery Papilloedema B-Features of the underlying illness.

RESPIRATORY ACIDOSIS Acute chronic p. H low <7. 36 or at lower limit of normal Pa. CO 2 high >45 mm. Hg HCO 3 Normal high >28 mmoll

Respiratory failure o Type I respiratory failure: Pa. O 2 < 60 mm. Hg with normal or low Pa. CO 2 o Type II respiratory failure: Pa. CO 2 >55 mm. Hg irrespective of O 2 value.

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

METABOLIC ALKALOSIS Definition: o a p. H > 7. 44 due to an increase in plasma HCO 3 o Pa. CO 2 may . o In normal renal function it is rare, why?

Aetiology Loss of H+, Cl, & Na Associated with EC volume depletion n GIT loss n Vomiting n Aspiration of gastric contents Loss through kidney Diuretics Carbenicillin, penicillins K depletion Mineralocorticoid excess Bartter`s syndrome 1 o & 2 o Aldosteronism Cushing syndrome Adrenal enzyme deficiency Hyperreninism Exogenous mineralocorticoids Carbenoxolone Exogenous alkali Na. HCO 3(Baking soda) Blood transfusions-citrate Antacids

METABOLIC ALKALOSIS Clinical picture AB- o o n Features of underlying illness Features related to metabolic alkalosis; Tetany Manifest Latent o o n n Due to acute fall in ionized Ca level Chvostok sign Traussau sign Altered state of consciousness

Arterial blood gas picture o p. H o o HCO 3 Pa. CO 2 >7. 44 or in the Upper limit of normal in compensated cases >28 mmoll >45 mm. Hg or normal

Treatment o A- Correct the metabolic alkalosis; n Correct EC volume depletion enhance HCO 3 excretion o B- Treat the underlying cause; n mineralocorticoid excess n Correct K

RESPIRATORY ALKALOSIS Definition: o p. H>7. 44 due to CO 2 washout as a result of hyperventilation

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

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

Arterial blood gas o p. H o Pa. CO 2 o HCO 3 high >7. 44 low<35 mm. Hg normal or low<21 mmoll

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

Summary METABOLIC ACIDOSIS METABOLIC ALKALOSIS RESPIRATORY ACIDOSIS RESPIRATORY ALKALOSIS p. H Pa. CO 2 HCO 3 (OR LOW NORMAL) Compensatory (OR HIGH NORMAL) Compensatory (OR LOW NORMAL) (OR HIGH NORMAL) Compensatory