Acid—base balance 1

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Acid-
Acid-Base Balance
Physiology
- The pH of ECF is tightly regulated
- Normal: 7: 35 – 7: 45
- Daily production of acid :12000meq
- Removal lung (most)
- kidney (small ,50-100meq/day)but
restore buffer capacity (HCO3)¯¯¯
- Respiratory or renal disfunctionbreakdown in
processacid-base disorders


-addition of acid [H+ ] &pH
&pH
-PH<7.35= [H+ ]=blood is acidotic or acidemic
PH<7 35= [H
-PH>7.45=[H+]=blood is alkalemic or alkalotic
PH>7 45=[H


Effect of PH imbalance

Majority of body functions optimally at or near pH
of 7.40
AcidosisCNS depression,lethargy,disorientation,
coma
Alkalosisover exitability of CNSperipheral
nerves,tetany, muscular spasms of extremities,face
body,respiratory failure
Significant pH alteration Heart contractility


PaCO2
PaCO2

 Normal :35-45mmHg
 paco2 is respiratory componet of acid base status
 regulation: 1) co2 production rate
 2) Alveolar ventilation
 fever or exercise co2 productionVAnormal
paco2
 Paco2 is the most reliable index of VE(minute volume)
 PaCO2 [H+ ]Respiratory Acidosis
 Paco2 [H+ ] = Respiratory Alkalosis


Arterial Hco3¯
Hco3
 Normal = 22—26 mEq/ L
 Metabolic component of Acid –Base status
 Regulation by renal system
 Hco3¯PH=Metabolic Alkalosis
 Hco3¯PH =Metabolic Acidosis
 Hco3¯ may change in response to primary change
of paco2 (12—24 hr )
 Co2 + H2O  H2co3  H+ + Hco3¯
 Paco2 Hco3¯
 Paco2Hco3¯


Base Excess & Base deficit
BE+ BE¯
BE¯
 Normal : 2mEq/L

 Be indicate pure metabolic component


Acid—
Acid—Base disorders
 1 )Simple disorder: Respiratory Acidosis
Respiratory Alkalosis
Metabolic Acidosis
Metabolic Alkalosis
 2 ) Mixed disorders


Respiratory Acidosis
 -Alveolar Ventilation relative to co2 production
 Paco2 (paco2 > 45 mmhg ) or higher than expected level of
compensation
 Ethiology :1) Respiratory :
*Acute upper Airway obstruction
*sever diffuse airway obstruction (Acute or
chronic)
* Massive pulmonary edema
2) Nonrespiratory:
* Drug overdose
*Spinal cord trauma
*Neuromuscular disease
*Head trauma
*trauma to thoracic cage

Compensation of Respiratory
Acidosis
 Acute :pH paco2 Hco3¯ BE
 Partial compensation : PH paco2 Hco3¯ BE
 completely compensated :pH normal up to 7.39
paco2 HCO3¯ BE
 Acute Respiratory Acidosis:10—15mmHg
paco21mEq/L Hco3¯
 Chronic Respiratory Acidosis:10mmhg
paco24mEq/L Hco3¯


Clinical Effect of Respiratory
Acidosis
 Acute:CNS:Headache,sleepy,lethargy,confusion,
semiconciousness,coma(paco2>70 mmhg)
 But chronic :higher level of paco2 may be well
tolerated
 Hypoxemia may presented
 CVS : 1)paco2 vasodilution+COwarm flushed
skin +bounding pulse
 2) Arrhytmias
 3)Cerebral vasodilation ICP,Retinal
venous distention , pupilledema & headache
 Hco3¯(in compensation of Respiratory
Acidosis)Cl level

Respiratory Alkalosis
 Paco2 <35mmHg
 Alveolar Ventilation Relation to co2 Production
 Ethiology :Pain, Hypoxemia(pao2<55-60mmHg),
Acidosis , Anexity, Mechanical ventilation
 pH , paco2 and normal Hco3¯ &
BE=uncompensated R Alkalosis
 pH7.45 , paco2 , Hco3¯ , BE =partial
compensation R Alkalosis
 pH in normal range , paco2 , Hco3¯ , BE=Full
compensated R Alkalosis


Metabolic Acidosis
 Hco3¯ BE
 Buffers : production or loss
 H+Acid) : load H+ or Excretion
 Loss of Hco3¯ : diarrhea , renal disease
 Metabolic Acid production: Keto acidosis , lactic
acidosis,certain toxins(Metanol)
 Post hypocapnia disorder
 ANION GAP:Na–(Cl¯+Hco3¯)
 Normal=8-16mEq/L . With K =1220mEq/L
 Normal Anion gap : HCL , diarrhea , RTA , (type 2 ,
proximal)
 High Anion gap :Renal Failure , lactic acidosis , keto
acidosis

Metabolic Alkalosis
 -Hco3¯> Normal
 -Accumolation of Hco3¯or H loss
 Ethiology: Hypokalemia or hypochloremi
*Nasogastric suction
*persistent vomiting
*post hypercapnia Disorder
*Diuretic therapy
*Steroid therapy
*Excessive Adminstration of sodium bicarbonat


Compensation of M Alkalosid
 Hypoventilation paco2(Not in awake paients)
 Uncompensated M Alkalosis :Hco3¯ BE
PH & Normal paco2
 Partial compensated: ph is not yet normal ,
Hco3¯ BE Paco2>45mmHg
 Complet compensation : paco2 enough to
PHNormal


Mixed Acid –Base disorder
 When two of the symple are Acid –Base are present
simultaneosly
 Respiratory & metabolic Acidosis: cardiopulmonary
arrest , COPD , Hypoxia , poisoning & Drug
overdosage (Barbiturate)
 Metabolic & Respiratory Alkalosis :Critical care
unit:MV , anxeity , pain , Nasogastric suctioning ,
vomiting , transfusion, antiacid
 Metabolic Acidosis & Respiratory Alkalosis:lactic
acidosis(Hypoxia)+MV(Hyper ventilation)
 Metabolic Alkalosis & Respiratory
Acidosis:COPD+Diuretic therapy


‫ﭘﺎراﻣﺘﺮ ھﺎي اﺳﯿﺪ-ﺑﺎز در راﺑﻄﮫ ﺑﺎ ﻏﻠﻈﺖ ﯾﻮن ھﯿﺪروژن‬
‫اﺟﺰاي‬
‫ﺗﻨﻔﺴﻲ و اﺟﺰاي ﻣﺘﺎﺑﻮﻟﯿﻚ‬
‫ﭘﺎراﻣﺘﺮھﺎي اﺳﯿﺪ-ﺑﺎز‬ ‫اﺟﺰا‬
‫‪PH‬‬ ‫ﻏﻠﻈﺖ ﯾﻮن ھﯿﺪروژن‬
‫2‪Paco‬‬ ‫اﺟﺰا, ﺗﻨﻔﺴﻲ‬
‫2‪Pao‬‬
‫‪o2sat‬‬
‫3‪Hco‬‬ ‫اﺟﺰا, ﻣﺘﺎﺑﻮﻟﯿﻚ‬
‫‪BE‬‬
‫‪BEecf‬‬
‫‪BB‬‬

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Interpretation and discussion
 PH Acidosis PH Alkalosis

 PaCo2 Acidosis Paco2 Alkalosis

 BE Alkalosis BE Acidosis

 Pao2<60mmHg Hypoxia
 Sao2<%90 Hypoxia


External Respiration

MIXED VENOUS BLOOD ARTERIAL BLOOD

pH 7.36 pH 7.40
PCO2 46 mmHg PCO2 40 mmHg
PO2 40 mmHg PO2 95 mmHg
SO2 75% SO2 95%

Internal Respiration

‫ در ﺷﺮاﯾﻂ ﻃﺒﯿﻌﻲ و ﺑﺤﺮاﻧﻲ‬PH ‫ﻏﻠﻈﺖ ﯾﻮن ھﯿﺪروژن و‬

‫ﺗﺸﻨﺞ‬ ‫ﻃﺒﯿﻌﻲ ﻛﻮﻣﺎ‬ ‫ﭘﺎراﻣﺘﺮ‬

١٦ ١٢٥ ٤٠ [H]

٧/٨ ٦/٩ ٧/٤ PH



 PH=7/16 7.35-7.45
 Paco2=40mmHg 35-45mmHg
 Pao2=60mmHg 80-100mmHg
 Sao2=85% >90%
 Cao2=11vol% 16-20 vol%
 BE= 14 ±2
 Hco3¯ = 14mEq/L 22-26mEq/L



 PH = 7.49
 Paco2 = 32mmHg
 Pao2 = 68 mmHg
 Sao2=91.5%
 Cao2 = 16 vol%
 Hco3¯ = 22mEq/L
 BE = 1



 Ph = 7.41
 Paco2 = 61mmHg
 Pao2 = 66 mmHg
 Sao2=91. 4%
 Cao2 = 12.2 vol%
 Hco3¯ = 37mEq/L
 BE =+11



 PH = 6.96
 Paco2 = 17mmHg
 Pao2 = 110mmHg
 Sao2=99. 9%
 Cao2 = 19 vol%
 Hco3¯ = 3.5mEq/L
 BE = 24



 PH = 7.53
 Paco2 = 31mmHg
 Pao2 = 90mmHg
 Hco3¯ =25mEq/L
 BE = +5mEqL


 PH = 7.25
 Paco2 = 32mmHg
 Hco3¯ =16mEq/L
 BE = - 10 mEqL


 PH = 7.21
 Paco2 = 67mmHg
 Pao2 = 49 mmHg
 Sao2=76%
 Cao2 = 10.4 vol%
 Hco3¯ = 26 mEq/L
 BE = 2
 Hb = 10


 PH = 7/409
 Paco2 = 27/2
 BE = -5/2
 Hco3¯ = 16/7
 Pao2 = 53
 O2sat = 86


Acid—base balance 1

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