Acid-Base Balance Flashcards
yield hydrogen ion (H+) or hydronium ion when dissolve in water
Acid
yield hydroxyl ion
Base
relative strength of an acid and base ; ability to dissociate in water
K value or ionization constant
Negative log of ionization constant
pKa
Combination of weak acid and weak/conjugate base; prevents changes in pH
Buffer
Principle Buffer System:
Bicarbonate-Carbonic Acid System (pKa of 6.1)
Buffer Reference Value
7.40 H+ or 40 mmol/L
Major Buffer System (4)
Bicarbonate -Carbonic Acid
Protein Buffer
Phosphate Buffer
Hemoglobin Buffer System
Principle Buffer System of the Body
Bicarbonate-Carbonic Acid Buffer System
H2CO3 (Weak Acid)
A. Releases Hydrogen ion
B. Do not release ion
B. Do not release ion
It carries both acidic and basic charge to be able to find or release excess hydrogen
Protein Buffer System
present in plasma proteins which are NEGATIVE in charge and capable of binding with H+
Imidazole groups of histidine
Buffer System by which excess H+ combines in renal tubules with Na2PO4
Sodium is reabsorbed and H+ is passed in urine
Phosphate Buffer System
Plays a role in plasma and RBC involved in exchange of sodium ion in the urine H+ filtrate
Phosphate Buffer System
Amino acid that produces NH3
Glutamine
Excreted form of ammonia in urine
NH4
Decreased pH = ____ NH3
Increased NH3
Inability to produce acidic urine
Renal Tubular Acidosis
Type of Renal Tubular Acidosis that is characterized with defective H+ secretion
Type I (Distal RTA)
Type of RTA with reduced reabsorption of HCO3
Type II (Proximal RTA)
Type of RTA with decreased ammoniagenesis
Type IV RTA
Buffer system involves CO2 combining with H2O forming H2CO3 by CARBONIC ANHYDRASE found in RBC then dissociates into HCO3+
Hemoglobin-Oxyhemoglobin Buffer System
Oxygen Dissociation Curve:
Shift to the ___: Acidosis
Right
Oxygen Dissociation Curve:
Shift to the ___: Alkalosis
Left
Organs Associated in Maintaining pH
Lungs and Kidneys
Reference range of Acid-Base Balance
35 to 45 mmol/L
Main role to regulate H+
Bicarbonate + Carbonic Acid System
Two Components: Bicarbonate and Carbonic acid
- Bicarbonate
- Carbonic Acid
Bicarbonate
HCO3 —> H + HCO3 = H2CO3
Basic pH
Carbonic acid
H2CO3 –> H2CO3 + OH = HCO3 + H2O
Acidic pH
HCO3 to H2CO3 ratio
20:1
pKa = pKa + log A/HA
Henderson-Hasselbach Equation
Regulates pH by retention or elimination of CO2 by changing the rate and volume of VENTILATION
Lungs (Respiratory)
Represented by pCO2 (H2CO3)
Lungs
Hypoventilation - ____ CO2
Increased CO2 : Acidosis
Hyperventilation - ____ CO2
Decreased CO2 - Alkalosis
Regulates pH by excreting acid, primarily ammonium ion and reclaimingHCO3 from glomerular filtrate
Kidney
Represented by HCO3
Kidney (Metabolic)
IV Infusion of lactate, acetate and HCO3
Excess chloride (sweating, vomiting, prolonged nasogastric suction)
Increased HCO3
Use of diuretics
Excessive loss of cations
Kidney dysfunction like chronic nephritis
Decreased HCO3
Increased pCO2
Observed in Chronic Obstructive Pulmonary Disease (COPD)
Emphysema, Asthma
Myasthenia gravis
Barbituates, Morphine, Alcohol
Asphyxiation
Congestive Heart Failure (CHF)
Primary Respiratory Acidosis
Hyperventilation
Hysteria
Hypoxia
Salicylates
Increase Environmenal Temperature
Pulmonary Emboli, Fibrosis
Hepatic Cirrhosis
Asipirin Overdose
Primary Respiratory Alkalosis
Excess administration of sodium bicarbonate
Ingestion of bicarbonate producing salts such as lactate, citrate and acetate
loss of acid due to VOMITING
Primary Metabolic Alkalosis
Specimen needed for Acid-Balance and Blood-Gas Test
Arterial Blood (warmed @45 dec for 5 minutes)
Sample taken for pH and CO2
Venous blood (w/o tourniquet & clenching)
Dead space in the needle should be filled with sterile
Anticoagulant (Heparin)
Samples are placed in ___
Ice (Slurry Ice)
For every 20 minutes delay the pH lowers
0.01
Blood Gas Analysis routinely made @37c
For each grade of Fever in the patient:
pO2 will fall by 7%
pCO2 will rise by 3%
pH will decrease by 0.015
Measured by Blood Gas Instrument (3)
pH
pCO2
pO2
Instrument to Measure:
pH
Potentiometry
Sands Electrode
Instrument to Measure:
Silver-Silver Chloride
Calomel (HgCl2) is a reference method for
pH
Instrument to Measure:
pCO2
Clark Electrode (Polarography/Amperometry)
Instrument to Measure:
pO2
Severinghaus Electrode (Potentiometry)
Total CO2 Content:
HCO3 is converted to oxaloacetic acid by PHOSPHOENOLPYRUVATE CARBOXYLASE
measured spectrophotometrically
(malate –> malate dehydrogenase)
NADH ; UV Light Chromogen
Automated Enzymatic Method
Total CO2 Content:
Use of Silicone-rubber gas dialysis membrane
Cresol res at pH 9.2
Buffered Cresol Red Solution
Decrease in Color Intensity is proportional to CO2 content
Spectrophotometer at 430 nm
Automated Colorimetric Method
Total CO2 Content:
Pulse oximeter principle
Photometry
Total CO2 Content:
Based on red and Infrared Light
Pulse Oximeter
