acid-base disorders
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ACID-BASE DISORDERS
I.M.SIALA, MD
Acid-base disorders
Pulse
Pulse
HemoglobinHemoglobin
Blood Pressure
Blood Pressure
TemperatureTemperature
Hydro
gen Io
n
Conce
ntrat
ion
Hydro
gen Io
n
Conce
ntrat
ion
ProperCell
Function
ProperCell
FunctionCa, K, …
Ca, K, …
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
Hydrogen Ion ConcentrationHydrogen Ion Concentration
pH and H+ concentration
Compensatory mechanisms
Body buffers CO2-bicarbonate system
H+ + HCO3 H2CO3 H2O + CO2
Hemoglobin Hydroxyapatite
REGULATED BY KIDNEY
REGULATED BY LUNG
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 Na is reabsorbed in exchange of K or H+. KK H+H+ is excreted more alkalosis KK H+H+ is excreted less acidosis
Kidney needs 6 – 12 hours to start its compensating mechanisms.
+ CO2H2OH2CO3HCO3H++
Alkalosis
Acidosis
PHPH 7.36-7.447.36-7.44 7.4 7.4 ++.04.04
PaCO2PaCO2 35 – 45 mmHg35 – 45 mmHg 40 40 ++ 5 5
HCO3HCO3 21 – 28 mmol\l21 – 28 mmol\l 25 25 ++33
PaO2PaO2 83 – 108 mmHg83 – 108 mmHg
Acid base disturbancesArterial blood sampleArterial blood sample Normal valuesNormal values
Heparinized Heparinized syringesyringe
Radial Radial arteryartery
•A 2 ml syringe•Heparinized•Radial/ femoral artery•Draw 1 ml of blood•Send for analysis immediately or send in an ice pack
Acid-base disorders
AcidosisAlkalosis
ACIDOSISACIDOSIS
ACID ACID PaCOPaCO22
ALKALI ALKALI HCOHCO33
ACID ACID PaCOPaCO22
ALKALI ALKALI HCOHCO33
7.367.36 7 .447 .44
HCOHCO33COCO22
HCOHCO 33
COCO 22
COCO22
7.36 7 .44
METABOLIC ACIDOSISCOMPANSATED METABOLIC ACIDOSIS
HCOHCO33
COCO 22
ACID ACID PaCOPaCO
22
ALKALI ALKALI HCOHCO33
HCOHCO33COCO22
HCOHCO 33
COCO 22
HCOHCO 33
HCOHCO33COCO22
7.36 7 .44
RESPIRATORY ACIDOSISCOMPANSATED RESPIRATORY ACIDOSIS
HCOHCO33
COCO 22
COCO 22
COCO22
ACID ACID PaCOPaCO
22
ALKALI ALKALI HCOHCO33
ALKALOSISALKALOSIS
ACID ACID PaCOPaCO22
ALKALI ALKALI HCOHCO33
ACID ACID PaCOPaCO22
ALKALI ALKALI HCOHCO33
7.367.36 7 .447 .44
HCOHCO33COCO22
HCOHCO
33
COCO22
HCOHCO
33
HCOHCO33COCO22
7.36 7 .44
RESPIRATORY ALKALOSISCOMPANSATED RESPIRATORY ALKALOSIS
ACID ACID PaCOPaCO
22
ALKAALKALI LI
HCOHCO33
HCOHCO33COCO22
HCOHCO
33
COCO22
HCOHCO
33
HCOHCO33COCO22
7.36 7 .44
METABOLIC ALKALOSISCOMPANSATED METABOLIC ALKALOSIS
HCOHCO33
COCO22
COCO22
HCOHCO
33
ACID ACID PaCOPaCO
22
ALKAALKALI LI
HCOHCO33
Acid-base disorders
AcidosisMetabolicRespiratory
AlkalosisMetabolicRespiratory
Metabolic acidosis
a pH< 7.36 due to a reduction in plasma HCO3-.
PaCO2 will secondary to
hyperventilation .
a pH< 7.36 due to a reduction in plasma HCO3-.
PaCO2 will secondary to
hyperventilation .
Definition:Definition:
ANION GAP
Na+Na+
Anion GapAnion Gap
HCOHCO33__
ClCl--
“Anion gap represents the difference between readily measured anions and cations”
Anion gap = Plasma Na+ - (Cl- + HCO3-)
N= 8 – 14 mmol\l
Unmeasured Anions: albumin, phosphate, sulphate, lactate, ketoacids, others.
Unmeasured Cations: calcium, Mg, globulins, K.
Aetiology of metabolic acidosis
Na+Na+
Anion GapAnion GapHCOHCO33
__
ClCl--
Na+Na+
Anion GapAnion GapHCOHCO33
__
ClCl--
Increased Anion gap acidosis:Lactic acidosisKetoacidosis Diabetic
AlcoholToxins Methanol
Ethylene glycolSalicylate
Uraemia ARF CRF
Normal Anion gap acidosisHyperchloremic acidosis
GIT HCO3- lossDiarrheaPancreatic drainageUreterosigmoidostomy
Renal tubular acidosis
Drugs CA inhibitors
Anion GapAnion Gap
Metabolic acidosis
Clinical pictureClinical picture
A- due to acidosis:A- due to acidosis: Deep & rapid breathing, Kussmaul`s
breathing. Altered state of consciousness Hypotension in severe cases
B- Due to primary diseaseB- Due to primary disease
Arterial blood gas findings
pH low<7.36 or in the lower limit of
normal HCO3
- low <21 mmol\l
PaCO2 low < 35 mmHg
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.
RESPIRATORY ACIDOSIS
Definition:Definition: a pH < 7.36 due to increased retention of CO2 as a result
of alveolar ventilation
Definition:Definition: a pH < 7.36 due to increased retention of CO2 as a result
of alveolar ventilation
Respiratory Physiology
Aetiologya-Acutea-Acute Airway obstructionAirway obstruction
Foreign body Laryngospasm Severe bronchospasm
Respiratory center Respiratory center depressiondepression Morphine overdose CVA Trauma
NeuromuscularNeuromuscular High cervical cord
resection Myasthenia gravis Gullian Barre syndrome Organophosphorus
Restrictive defectsRestrictive defects Pneumothorax Flail chest
Cardiac Arrest & sever Cardiac Arrest & sever pulmonary oedemapulmonary oedema
COADCOAD
NeuromuscularNeuromuscular MS Muscular dystrophies Motor neuron disease Diaphragmatic paralysis
Chest wall deformitiesChest wall deformities Kyphoscolisis Ankylosing spodylitis
Primary alveolar Primary alveolar hypoventilation-hypoventilation-ObesityObesity
b-Chronicb-Chronic
RESPIRATORY ACIDOSIS Clinical Picture:Clinical 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.
AcuteAcute chronicchronic
pHpH low <7.36low <7.36 or atlower limit of
normal
PaCOPaCO22 high >45 mmHg high >45 mmHg
HCOHCO33 Normal high >28 mmol\l
RESPIRATORY ACIDOSIS
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.
A- Treat the underlying cause B- Treat carbon dioxide retention
Naloxone if Narcotic overdose is suspected Low oxygen concentration Mechanical ventilation in severe cases
Treatment
METABOLIC ALKALOSIS
Definition:Definition: a pH > 7.44 due to an increase in
plasma HCO3
PaCO2 may . In normal renal function it is rare,
why?
Definition:Definition: a pH > 7.44 due to an increase in
plasma HCO3
PaCO2 may . In normal renal function it is rare,
why?
Aetiology
Loss of H+, Cl, & NaAssociated with EC volume depletion
GIT loss Vomiting Aspiration of gastric
contentsLoss through kidney
DiureticsCarbenicillin, penicillins
K depletion
Mineralocorticoid excess
Bartter`s syndrome1o & 2o AldosteronismCushing syndromeAdrenal enzyme deficiencyHyperreninismExogenous mineralocorticoidsCarbenoxolone
Exogenous alkaliNaHCO3(Baking soda)Blood transfusions-citrateAntacids
METABOLIC ALKALOSISClinical picture A- Features of underlying illness
B- Features related to metabolic alkalosis;
Tetany Due to acute fall in ionized Ca level
Manifest Latent
Chvostok sign Traussau sign
Altered state of consciousness
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
Treatment
A- Correct the metabolic alkalosis; Correct EC volume depletion enhance HCO3
excretion
B- Treat the underlying cause; mineralocorticoid excess Correct K
RESPIRATORY ALKALOSIS
Definition:Definition: pH>7.44 due to CO2 washout as a
result of hyperventilation
Definition:Definition: pH>7.44 due to CO2 washout as a
result of hyperventilation
Aetiology
Hypoxia Voluntary CNS Disease
CVA Infections Trauma Tumours
DrugsAspirin Hepatic Failure Gram Negative Septicaemia Heat Exposure Mechanical overventilation
Clinical picture
A- features of the underlying cause. Anxiety
B- Features of Alkalosis; Tetany
Parasthesia, numbness around the mouth, tingling in hands & feet
Tetany
Arterial blood gas
pH high >7.44 PaCO2 low<35 mmHg
HCO3 normal or low<21 mmol\l
Treatment
A- Treat the underlying cause
B- Supportive measures; Rebreathing in a paper bag in
Hyperventilation syndrome + sedation
pHpH PaCO2PaCO2 HCO3HCO3
METABOLIC ACIDOSIS
(OR (OR LOWLOW NORMAL)NORMAL)
CompensatoryCompensatory
METABOLIC ALKALOSIS
(OR (OR HIGH HIGH NORMALNORMAL))
CompensatoryCompensatory
RESPIRATORY ACIDOSIS
(OR (OR LOWLOW NORMAL)NORMAL)
CompensatoryCompensatory
RESPIRATORY ALKALOSIS
(OR (OR HIGHHIGH
NORMAL)NORMAL)
CompensatoryCompensatory
SummarySummary
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