Acid-base Banlance and Acid-base Disturbance
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Transcript of Acid-base Banlance and Acid-base Disturbance
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Acid-base balance and
acid-base disturbance
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I. regulation of acid-base balance
1. origin of acid and base in the bodyvolatile acid: H2CO3 (15mol/day)
sulfuric acid1) acids phosphoric acid
fixed acid: uric acid(90mmol/L) mesostate
2)base: salt of organic acid; NH3
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2. regulation of acid-base balance1) role of buffer
HCO-3/H2CO3 53%Hb-/HHb
buffer system HbO-2/HHbO2 35%Pr-/HPr 7%
Phosphate 5%Henderson-Hasselbalch
pH = pKa + lg [HCO-3]/[H2CO3]= 6.1 + lg 20/1 = 6.1 + 1.3 =7.4
buffer of fixed acid: HCO-3/H2CO3buffer of volatile acid: Hb-/HHb
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CO2
Cl-
CO2+H2O
C.A.
H2CO3
HCO-3
H+--Hb-
RBC
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2)respiratory regulationalteration of ventilation
alteration of breathe out of CO2
PaCO2 central
[H+] peripheral respirationPaO2 (receptor)PaCO2 (80mmHg)
inhibition of respiratory center3) cellular action exchanges of H+and K+
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4) renal regulation acidification of proximal renal tubule
Na+ Cl-
HCO-3
H2CO3
H20
H+Cl-NH3
K+
NH3
Na+
H+H2CO3
Na+C.A.
HCO-3 H2O+CO2
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acidification of distal renal tubule
H+-pump
NH+4
H+K+NH3
H2CO3 H+NH3
HCO-3 H2O+CO2
K+
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parameters of acid-base1. pH important and inexact parameter
normal range: 7.35~7.452. PaCO2 partial pressure of CO2of dissolved
in arterial plasma (respiratory parameter)normal range: 4.4~6.25kPa(33~46mmHg)primary change:
respiratory acidosis PaCO2
respiratory alkalosis PaCO2
secondary change:
metabolic acidosis PaCO2metabolic alkalosis PaCO2
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3. standard bicarbonate(SB)
and actual bicarbonate(AB)
SB: [HCO-3] in plasma under standard condition(38; PO2=150mmHg; PCO2=40mmHg)
AB: [HCO-3] in plasma under actual conditionNormal range: 22~27mmol/L ; AB=SB
4. buffer base(BB)sum of all buffer base in bloodnormal range: 45 ~ 55mmol/L
5. base excess(BE)normal range:3mmol/L
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6. anion gap (AG)+ -
Normal range: 12 2 mmol/L
Na+
Cl-
AG
HCO-
3
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. simple acid-base disturbance1. metabolic acidosis
concept: the primary disturbance is a decreaseof [HCO-3] in the arterial plasma
1) cause and pathogenesislactic acidosis: hypoxia, diabetes
liver diseaseketoacidosis: diabetes, starvationmetabolic
acidosis in severe renal failure: fixed acidsincreased AG
salicylic acid acidpoisoning: intake food
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diarrhea;GI: intestinal suction(loss of intestinal fistulaHCO-3) biliary fistula metabolic
acidosis in early renal failure:
normal AG NH3
secretionH+secretion
Renal tubular acidosis:H+secretion
kidney: depressant of C.A.(loss of acetazolamide
HCO-3) intake of Cl-
NaCl, NH4ClHyperkalemia
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2) compensatory regulationbuffer:respiratory compensationcellular compensationrenal compensation
[H+
] : C.A. H+
secretionNH3 secretion
[HCO-3] / [H2CO3] = 20:1 compensation
acidosis
[HCO-3] / [H2CO3] < 20:1 decompensation
acidosis
(SB AB BB BE PaCO2 AB < SB)
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3) effect on bodycardiovascular system
hyperkalemia arrhythmia[H+] : contractility
peripheral resistance
central nervous system[H+] ATP , -amino butyric acid
(somnolence, coma)4) principles of treatment
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2. respiratory acidosisconcept: The primary disturbance is an
elevation in plasma [H2CO3]1) cause and pathogenesis
Barbitaldepression of CNS head injury CO2 breathe paralysis of respiratory muscles
out disease of airway or lungchest injury
inhalation of CO2
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2) compensationbuffer: Hb-/HHbcells: exchange of H
+
and K+kidney: secretion of H+and NH3
(PaCO2 SB AB BB BE ABSB)3) effect on bodyCNS
CO2 CO2 narcosis respirationcardiovascular system
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4) principles of treatmentNaCO3
3. metabolic alkalosisconcept: the primary disturbance is
an increase of [HCO-3] in the
arterial plasma
1) causes and pathogenesis
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digestive tractvomiting; gastric suction(loss of HCl)
loss diuretics distal flow rateof H+ (furosemide) blood volume ADS
kidney hyperaldosteronism H+-Na+exchange
H+-K+exchange betweenHypokalemia
intra- and extra-
cell
renal secretion of H+hypochloremia
renal secretion of H+
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NaHCO3intake transfusion of banked bloodof base (citrate)
2) compensation of the bodyrespiration compensation are limited
(hypoxia)cells compensation hypokalemiakidney pH inhibition of carbonic
anhydrase (C.A.)secretion of H+
(SB AB BB BE PaCO2
ABSB)
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3) effects on bodyinhibition of glutamate decarboxylase
CNS -amino butyric acid dysphoriainsanity
pH brain-vessel dizzinesscontraction brain delirium
O2dissociation hypoxia Comacurve shifting to left
neuromuscle pH free Ca2+ tichypokalemia arrhythmia
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4) principles of treatmentloss of H+digestive tractdiuretic ; hypokalemia 0.9%NaCl; KCl
hyperaldosteronism
antisterone; diamox()
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4. respiratory alkalosis
concept: the primary disturbance is decrease
of [H2CO3] in plasma1) cause and pathogenesis
hypotonic hypoxia
pneumoniahyperventilation hysteria(); fever; [NH3]
hyperthyroidism()misoperation of ventilator
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respiration (slight inhibition)2) compensation cells (exchange of H+-K+)
kidney secretion of H+
(PaCO2 ; SB AB BB BE ; ABSB)3) effects on body
It is as same as metabolic alkalosis.dizziness and convulsion are happened easily() ()
4) principles of treatmentinhalation of 5%CO2
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IV. Mixed acid-base disturbance1. dual acid-base disturbance1)metabolic acidosisplusrespiratory acidosis
heart beat [HCO-3]respiration
stop character PaCO2pH
2) metabolic alkalosis plus respiratory alkalosishepatic NH3 PaCO2
failure diuretic character [HCO-3]pH
3)respiratory acidosis
plusmetabolic alkalosis
pulmonary heart diseasediuretic pH
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4) respiratory alkalosis plus metabolic acidosisinfective shockfever
pH5) metabolic acidosis plus metabolic alkalosis
ketoacidosis(diabetes)vomiting pH
2. triple acid-base disturbance1) respiratory acidosis; metabolic acidosis
and alkalosispulmonary heart disease; vomiting2) respiratory alkalosis; metabolic acidosisand metabolic alkalosis
fever; vomiting; diarrhea (food poisoning)
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discuss of casemethod:
1. pH2. primary factor and parameter3. secondary factor and compensation4. expected range of compensation
1:
patient, female, 46, chronic pyelitispH 7.32PaCO2 28mmHgCO2.CP. 19.2ml%SB 13.6mmol/LBE -15.3mmol/L
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The scope of compensatory
responses of acid-base disordersacute respiratory acidosis : [HCO-3]=0.1 PaCO2 1.5chronic respiratory acidosis: [HCO-
3
]=0.4 PaCO2
3.0
acute respiratory alkalosis : [HCO-3]=0.2 PaCO2 2.5chronic respiratory alkalosis:[HCO-3]=0.5 PaCO22.5
metabolic acidosis: PaCO2=1.2 [HCO-3] 2.0metabolic alkalosis: PaCO2=0.7[HCO-3]5.0
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2:patient, male, 45, chronic bronchitispH 7.26PaCO2 60mmHgBB 46.2mmol/LSB 22mmol/L
BE -7.5mmol/L
after treatmentpH 7.34PaCO2 70mmHgBB 58mmol/LBE 5.5mmol/L
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3.
patient, male, 47, purulent appendicitis, he
was treated with abdominal suction andpersistent gastrointestinal decompressionafter operation.
pH 7.56PaCO2 50mmHgCO2.CP. 90ml%SB 34mmol/LBE 10mmol/LK+ 3.2mmol/LCl- 105mmol/L
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4.
, 3, 20 / T 39.81200ml.