1. Acid and Base Disturbance

2. pH Review H+ is a proton pH Range is from 0 - 14
If [H+] is high, the solution is acidic; pH < 7
If [H+] is low, the solution is basic or alkaline ; pH > 7

3. The Body and pH Homeostasis of pH is tightly controlled
Extracellular fluid = 7.4
Blood = 7.35 – 7.45 (7.40)
< 6.8 or > 8.0 death occurs
Acidosis (acidemia) below 7.35
Alkalosis (alkalemia) above 7.45
Normal Serum HCO3- is mmol/L

5. Small changes in pH can produce major disturbances
Most enzymes function only with narrow pH ranges
Acid-base balance can also affect electrolytes (Na+, K+, Cl-)

6. The body produces more acids than bases
Acids take in with foods
Cellular metabolism produces CO2.
CO2 + H20 ↔ H2CO3 ↔ H+ + HCO3-
Slightly Alkaline plasma of 7.40(H+ : 40 nmol/L) is maintained by kidney capacity to produce an Acidic Urine(PH typically 5-6)in which the excess of metabolic acid can be excreted.

7. Renal Control of Acid-Base balance
Kidneys are Most effective regulator of pH
If kidneys fail, pH balance fails
Collecting ducts cells, Can eliminate large amounts of acid (Acid is secreted into the lumen by H+_ATPas )
Can also excrete base
Can conserve and produce bicarb ions Renal compensatory mechanisms may take hours to days OR EVEN WEEKS

8. Respiratory mechanisms
Exhalation of carbon dioxide CO2
CO2 + H20 ↔ H2CO3 ↔ H+ + HCO3-
Body pH can be adjusted by changing rate and depth of breathing
Respiratory mechanisms (hypo or hyperventilation) take several minutes to hours

9. Urinary Buffers
Bicarbonate: some 85% of the filtered Bicarbonate reabsorbed in the Proximal tubule
phosphate: Maintain a 20:1 ratio
HCO3- : H2CO
Ammonia : Major intracellular buffer
H+ + HPO42- ↔ H2PO4-

12. Compensation to Acid-Base Imbalances
If underlying problem is metabolic, hyperventilation or hypoventilation can help : respiratory compensation.
If problem is respiratory, renal mechanisms can bring about metabolic compensation.

13. Acidosis
Principal effect of acidosis is depression of the CNS through ↓ in synaptic transmission.
Generalized weakness
Deranged CNS function the greatest threat
Severe acidosis causes
Disorientation
coma
death

14. Alkalosis
Alkalosis causes over excitability of the central and peripheral nervous systems.
Numbness
Lightheadedness
It can cause :
Nervousness
muscle spasms or tetany
Convulsions
Loss of consciousness
Death

15. Simple Acid-Base Disorders
Primary Compensatory
Disorder pH H+ Disorder Response
Metabolic acidosis   HCO3_  pCO2
Metabolic alkalosis  HCO3_  pCO2
Respiratory acidosis  pCO2  HCO3_
Respiratory alkalosis  pCO2  HCO3_

17. Respiratory Acidosis
Carbonic acid excess caused by blood levels of CO2 above 45 mm Hg(= PCO kpa). Hypercapnia – high levels of CO2 in blood causes
Chronic conditions:
Depression of respiratory center in brain that controls breathing rateby drugs or head trauma
Paralysis of respiratory or chest muscles
_Emphysema
Acute conditons:
Adult Respiratory Distress Syndrome
Pulmonary edema
Pneumothorax
* Compensation: Kidneys eliminate hydrogen ion and retain bicarbonate ion

18. Signs and Symptoms of Respiratory Acidosis
Breathlessness
Restlessness
Lethargy and disorientation
Tremors, convulsions, coma
Respiratory rate rapid, then gradually depressed
Skin warm and flushed due to vasodilation caused by excess CO2
Treatment Restore ventilation
Treat underlying dysfunction or disease

19. Respiratory Alkalosis
cause is sustained hyperventilation
Carbonic acid deficit..washing of CO2
pCO2 less than 35 mm Hg (hypocapnea),Most common acid-base imbalance causes
high altitudes (Oxygen deficiency) Hyperventilation
Pul embolisim,Acute anxiety….HYS,Fever, anemia
Early salicylate intoxication..stim brain stem resp.center
&Cirrhosis chronic liver disease
Cl/p: perioaral & digital tingling ,Tetany (due to decrease ionised Ca++ caused by increase binding of Ca++ to Albumen in Alkalosis
Treatment :Treat underlying cause
rebreathe into a paper bag

20. Metabolic Acidosis characterized HCO3- less than 24,Caused by:
Loss of bicarbonate through diarrhea or renal dysfunction
Accumulation of acids (lactic acid or ketones)
Failure of kidneys to excrete H+

21. Causes of Normal AG (Hyperchloremic) Metabolic Acidosis
High K Low K+
Adrenal insufficiency Diarrhea
Interstitial nephritis RTA proximal,Distal
Ureteral diversion
AG = (Na+ + K+) - (Cl- + HCO3-) = 15

22. Metabolic Acidosis: Elevated Anion Gap
AG = (Na+ + K+) - (Cl- + HCO3-) = 15
[Note: Diagnostic utility is best when AG > 25]
Causes Ketoacidosis
Lactic acidosis
Intoxications(salicylate ,Methanol poisoning)
Renal failure
Rhabdomyolysis

23. Compensation for Metabolic Acidosis
Increased ventilation
Renal excretion of hydrogen ions if possible
K+ exchanges with excess H+ in ECF
( H+ into cells, K+ out of cells)

24. Metabolic Alkalosis
Bicarbonate excess - concentration in blood is greater than 24 mmol/L
compensation…hypoventilation..ie PCO2 will be more than 5.33 kpa
Causes:
Excess vomiting = loss of stomach acid
Loop &Thiazide Diuretics (loss of H+ in urine)
Cushing synd, ,primary hyperaldoteronism(corticosteroid excess)
Heavy ingestion of antacids
Severe dehydration