1. ABG Ph <7.35 Acidemia Ph>7.45 Alkalemia
BE:Base Excess ,defined as the amount of strong acid (Hcl for BE>0)or strong base(NaoH for BE<0)required to return 1 lit of whole blood to a Pco2=40 mmhg to PH=7.4.It shows nonrespiratory or metabolic component of an acid-base disturbance.BE<0 means metabolic acidosis,BE>0 means metabolic alkalosis

2. HCO3=22-26 Physiologic changes to acid-base disturbances:
Buffer system:1)bicarbonate buffer system(H2co3/Hco3)
2)protein buffer system(prH/Pr)
3)hemoglobin buffer system
4)phosphate buffer system
5)ammonia buffer system
Ventilation
Renal responses
These systems try to preserve the proportion of Hco3 to Co2 equal to 20

3. The most important buffering system is bicarbonate
CO2+H2O<<>>H2CO3<<>>H+HCO3
base molecule weak conjugated acid
The second important buffering system is Hgb
These buffering systems try to keep constant the proportion of Hco3 to Co2 equal to 20
VENTILATORY RESPONSE:central chemoreceptors respondto changes in CSF PH.Pripheral chemoreceptors are sensitive to Pao2
RENAL RESPONSE:slow in onset and maximal up to 5 days
1:reabsorption of Hco3
2:excretion of acid
3:production of ammonia

4. Sampling From radial ,brachial,femoral artery
Peripheral venous blood is good for Pco2,PH,BE
Pvco2 4-6 mmhg higher
Phvenous to 0.04 lower
Pvo2 is significantly lower depending on the
site of venous blood draw,differeces in tissue
metabolic activity may alter Pvo2

5. Heparinized,bubble free, fresh
Heparine is acidic then falsely lower PH
Air bubbles influence on Paco2 and Pao2,then should be removed
Delay causes o2 consumption and Co2 generation by metabolic activity of WBC,it can be reduced by place on ice
Hypothermia results decrease in Pco2 and Po2 and increase in PH,while Hco3 doesn’t change and so PH increases

6. THE EFFECT OF ACIDOSIS AND ALKALOSIS
Acidemia results in decrease in myocardial contractility and increase in catecholeamines.
PH<7.1>>>>decrease in myocardial response to catecholamines
Respiratory acidosis may produce more rapid and profound myocardial dysfunction than metabolic acidosis because of rapid entrance of co2 to myocard
PH>7.6>>>>decrease in cerebral and coronary blood flow because of vasoconstriction
In the brain rapid increase in Co2 decrease ph intracellular and then confusion and seizure happens but chronic increase in CO2 till 150 is well tolerated.

7. RESPIRATORY ACIDOSIS
Increased production: _Hyperthyroidism _Sepsis _Overfeeding
Decreased elimination
_pul. Dis.(pneumonia,ARDS,edema)
_upper airway obst.(laryngospasm,foreign body)
_lower airway obst.(asthema,COPD)
_Chest wall restriction(obesity,scoliosis,burns)
_CNS depression(opioids,CNS lesion)
_decreased skeletal muscle strength(myopathy,neuropathy)
_restriction of ventilation(rib fractures,flail chest)

8. Consequences of resp. acidosis
Metabolic alkalosis may accompany resp. acidosis when the body stores of cl and k are decreased and then reabsorption of Hco3,cause metabolic alkalosis,this makes PH normal and Pco2 high
Avoid hyperventilation because of hypocapnea and CNS irritability
PH<7.2>>>>intubation
Treatment:Kcl administration
Decreased renal perfusion in corpulmonal ,COPD >>>metabolic acidosis

9. Respiratory alkalosis
Iatrogenic (mechanical hyperventilation)
Decreased barometric p.
Hypoxia
CNS injury
Salicylate overdose
Hepatic dis.
Pregnancy
Decreased Paco2,PH increased>>>stimulate chemoreceptors>>>MV decrease
_PH>7.6>>>>sedation is required

10. Metabolic acidosis Lactic acidosis DKA Renal failure Hepatic failure
Methanol and ethylen glycol intoxication
Aspirin intoxication
Increased skeletal muscle activity
Cyanide poisoning
CO poisoning
Treatment :cause of acidosis should be treated
_insulin and fluid for DKA
_improvement of tissue perfusion for lactic acidosis
PH<7.1,Hco3<10 meq>>>administration of bicarb
life threatening hyperkalemia>>>>bicarb
cardiac arrest with hyperkalemia>>>bicarb
cardiac arrest with preexisting metabolic acidosis>>>bicarb
Administration of bicarb>>>co2 intracellular increase >>>Ph intracellular decrease,admi. Of bicarb shift PH toward normal and this shifts oxyhemoglobin to left >>>O2 delivery to tissues decrease

11. Metabolic alkalosis Hypovolemia Vomiting NG suctioning
Diuretic therapy
Hco3 administration
Hyperaldostronism
Chloride wasting diarrhea
Treatment :
_volume depletion(vomiting,diarrhea)>>>saline
_volume overload(mineralocorticoid excess)>>>>spironolacton and Kcl

12. Adverse consequences of alkalosis
_Nervous system Decreased cerebral blood flow Seizures Lethargy Delirium Tetany _Cardiovascular system Arteriolar vasoconstriction Decreased threshold for angina pectoris Predisposition to refractory dysrhythmia _ventilation Hypoventilation Hypercapnea Hypoxia _metabolism Hypokalemia,hypocalcemia,hypomagnesemia,hypophosphatemia,glycolysis stimulated

13. Adverse consequences of severe acidosis
Nervous system
Obtundation
Coma
Cardiovascular system
Impaired myocardial contractility
Low CO
Hypotension
Decreased responsiveness to cathecolamines
Decreased threshold for VF
Ventilation
Hyperventilation
Dyspnea
Fatigue of respiratory muscles
Metabolism
Hyperkalemia
Insuline resistance
Inhibition of anaerobic glycolysis

14. Identification of acid base disturbances
Acidosis:PH<7.35
Alkalosis:PH>7.45
_Paco2 high,Hco3 high:resp.acid _Paco2 high,Hco3 normal or low:resp. acidosis plus metabolic acidosis _Paco2 normal,Hco3 low:met.acidosis plus resp.acidosis _Paco2 low,Hco3 low:met.acidosis
Paco2 high,Hco3 high:met.alk.
Paco2 low,Hco3 low:resp. alk.
Paco2 low,Hco3 high:resp.alk. Plus metabolic alkalosis