acid—base balance 1

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AcidAcid--Base Balance 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 disfunctionbreakdown in

processacid-base disorders




--addition of acid addition of acid [[HH++ ]] &pH&pH--PH<PH<77..3535= [= [HH++ ]]=blood is acidotic or acidemic=blood is acidotic or acidemic--PH>PH>77..4545=[H=[H++]]=blood is alkalemic or alkalotic=blood is alkalemic or alkalotic




Effect of PH imbalanceEffect of PH imbalance

Majority of body functions optimally at or near pH of 7.40

AcidosisCNS depression,lethargy,disorientation,comaAlkalosisover exitability of CNSperipheral

nerves,tetany, muscular spasms of extremities,face body,respiratory failure

Significant pH alteration Heart contractility




PaCOPaCO22

Normal :35-45mmHg paco2 is respiratory componet of acid base status regulation: 1) co2 production rate 2) Alveolar ventilation fever or exercise co2 productionVAnormal

paco2 Paco2 is the most reliable index of VE(minute volume) PaCO2 [H+ ]Respiratory Acidosis Paco2 [H+ ] = Respiratory Alkalosis




Arterial HcoArterial Hco33¯̄ 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¯ Paco2Hco3¯




Base Excess & Base deficitBase Excess & Base deficitBBEE++ BEBE¯̄

Normal : 2mEq/L

Be indicate pure metabolic component




AcidAcid——Base disordersBase disorders

1 )Simple disorder: Respiratory AcidosisRespiratory AlkalosisMetabolic AcidosisMetabolic Alkalosis

2 ) Mixed disorders




Respiratory AcidosisRespiratory 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 Compensation of Respiratory AcidosisAcidosis

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

paco21mEq/L Hco3¯ Chronic Respiratory Acidosis:10mmhg

paco24mEq/L Hco3¯




Clinical Effect of Respiratory Clinical Effect of Respiratory AcidosisAcidosis

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+COwarm flushed

skin +bounding pulse 2) Arrhytmias 3)Cerebral vasodilation ICP,Retinal

venous distention , pupilledema & headache Hco3¯(in compensation of Respiratory

Acidosis)Cl level




Respiratory AlkalosisRespiratory 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 pH7.45 , paco2 , Hco3¯ , BE =partial

compensation R Alkalosis pH in normal range , paco2 , Hco3¯ , BE=Full

compensated R Alkalosis




Metabolic AcidosisMetabolic 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 =1220mEq/L Normal Anion gap : HCL , diarrhea , RTA , (type 2 ,

proximal) High Anion gap :Renal Failure , lactic acidosis , keto

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Metabolic AlkalosisMetabolic 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 AlkalosidCompensation 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

PHNormal




Mixed Acid Mixed Acid ––Base disorderBase 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




یون ھیدروژن یون ھیدروژن باز در رابطھ با غلظتباز در رابطھ با غلظت- - پارامتر ھاي اسیدپارامتر ھاي اسیداجزاياجزاي

باز-پارامترھاي اسیدتنفسي و اجزاي متابولیكتنفسي و اجزاي متابولیك اجزا PH غلظت یون ھیدروژن

Paco2 Pao2o2sat

تنفسي , اجزا

Hco3BEBEecfBB

متابولیك , اجزا




Interpretation and discussionInterpretation and discussion

PH Acidosis PH Alkalosis

PaCo2 Acidosis Paco2 Alkalosis

BE Alkalosis BE Acidosis

Pao2<60mmHg Hypoxia Sao2<%90 Hypoxia




MIXED VENOUS BLOOD

pH 7.36PCO2 46 mmHgPO2 40 mmHgSO2 75%

pH 7.40PCO2 40 mmHgPO2 95 mmHgSO2 95%

ARTERIAL BLOOD

External Respiration

Internal Respiration




در شرایط طبیعي و بحرانيدر شرایط طبیعي و بحراني PHPHغلظت یون ھیدروژن و غلظت یون ھیدروژن و

تشنج طبیعي كوما

پارامتر

١٦ ١٢٥ ٤٠ [ H ]

٧/٨ ٦/٩ ٧/٤ PH




Interpretation and discussion Interpretation and discussion

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 = +5mEqL





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





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




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