Interpret Acid Base data 2024-2025 - Dr Sameh Sarray.pdf
Transcript
Biochemistry Lab: Interpret Acid Base data Dr. Sameh Sarray Ph.D Intra Body fluids – ICF = 2/3 of total body fluid in adults; extra – ECF = 1/3 of total body fluid; - The composition of ICF differs Intracellular is...
Biochemistry Lab: Interpret Acid Base data Dr. Sameh Sarray Ph.D Intra Body fluids – ICF = 2/3 of total body fluid in adults; extra – ECF = 1/3 of total body fluid; - The composition of ICF differs Intracellular is different from outra markedly from that of ECF because of because of cell membrane the separation of these compartments by the cell membrane Euvolemia = Normal body fluid volume Hypervolemia = body fluid volume (weight gain) Hypovolemia = body fluid volume (weight loss) Osmosis-Osmotic pressure water movement from low to concentration high water will more from a diluted Solution to a you-diluted solution Osmosis: diffusion of water (solvent) through semi-permeable membrane from a solution of lower concentration ( high concentration in water/ hydrostatic pressure is high) towards a solution of higher concentration (low concentration of water/low hydrostatic pressure) it's the pressure that Osmosis-Osmotic pressure Osmotic pressure stops a solution from Is the pressure that being diluted Stops Osmosis Osmotic pressure is the pressure that must be applied to a solution to prevent it being diluted by the entry of solvent via osmosis (pressure required to prevent osmosis). All non penetrable solutes in a solution exerts osmotic pressure Osmotic pressure depends mainly on molarity of solution: Osmotic pressure is a colligative property as it depends on the number of dissolved particles and not on their identity. osmotic Pressure Is colligative property a , depends on number not Identity. Osmolality and osmolarity Osmolality KG - Solute in osmoles (Number of osmoles of particles)/Kg of solvent. - Expressed in mosmol/kg: - Higher osmolality means more particles in your serum. -Lower osmolality means they’re more diluted. - Not affected by temperature and pressure - Normal serum osmolality=280-298mosmol/kg don't need to know this Osmolarity Liter - Solute in osmoles / per liter (L) of solvent - Expressed in osmoles per liter (mosmol/L ) - Affected by changes in H2O, Temp. & pressure. Calculated serum osmolality know this > 2 x [Na+] + glucose + urea (all in mmol/L) Serum concentration : 2x Sodium + tured glucose osmolal gap : measured osmolality - calculated osmolality BUN: Blood urea nitrogen know this : – is an indication of unmeasured solute in the blood; for example alcano – Is important in determining the presence of exogenous substances that lead to acid base imbalance – A normal Serum osmolal gap = 5 – 15 mosmol/kg – In case a significant osmolal gap is detected, the following causes should be considered : ethylene glycol ingestion, methanol ingestion, ethanol or isopropyl alcohol ingestion, ketoacidosis, lactic acidosis, chronic renal failure, severe hyperlipidemia …… Electrolyte Disturbances - Disturbance of this balance can occur ; - E.g., cases of : less than 135 Hyponatremia = < 135 mmol/L (mild) less than 125 < 125 mmol/L (severe) more than 150 Hypernatremia = > 150 mmol/L Potassium less than 3 5. Hypokalemia = < 3.5 mmol/L Patassium more than 5 Hyperkalemia = > 5.0 mmol/L Pseudo hyponatremia normal osmolality but decreased Sodium cause : glucose (too much glucose will retain sodium) – It is an uncommon laboratory finding that can lead to severe morbidity and mortality – Defined by a serum sodium concentration of less than 135 mEq/L in the setting of a normal serum osmolality (280 to 300 mOsm/kg). – Causes: multiple causes; hyperglycemia (glucose cannot enter cells and hence water moves from intracellular space (ICF) to extracellular space (ECF) (osmotic effect of glucose), which in turn produces a dilutional decrease in serum sodium level. Serum sodium by 1.6 mmol for every 5.6 mmol in blood glucose above the upper limit of the reference range corrected sodium formula Corrected Na+ = Na+ + (excess glucose x 0.3) – [since 1.6/5.6 = 0.285 or approximately 0.3] Anion gap (AG) anion gap anion-cation = In our body fluid, Usually the total number of all anions equal the total number of all cations otherwise will be electrostatic. The anion gap is the difference between the sum of the main anions and the sum of the main cations, concentrations formula : Equations: (sodium + Potassium) (Chloride - + bicarbonate) AG= (Na+ + K+) – (Cl- + HCO3-) Or Normal anion gap (RR) is 10-12 mmol/L AG= (Na+) - (Cl-+ HCO3-) Diagnostic tool: HIGH anion gap indicates metabolic acidosis Causes: ketoacidosis, lactic acidosis, intoxications, renal failure… To assess fluid and electrolyte disturbances You need – Weight of patient – Blood urea – Blood glucose – Electrolytes in serum and urine – Osmolarity in blood and urine – Osmolar gap Acid base balance and its regulation The basic meaning of acid base balance is the stable [H+] in the body fluid Acid-Base Disorders Respiratory acidosis/alkalosis Metabolic acidosis/alkalosis Acidosis = High [H+] (pH < 7.35) Alkalosis = Low [H+] (pH > 7.45) bicarbonate Metabolic – due to changes in bicarbonate: high or low HCO3- CO2 Respiratory – due to changes in pCO2: high or low pCO2 REGULATION OF ACID BASE IMBALANCE Acid-Base Disorders Compensation: Metabolic Respiratory disorder – renal compensation Metabolic disorder – respiratory compensation The respiratory compensation mechanism respiratory (rapid results) (breath fast to eliminate (O2) s increases PH so for acidosis hyperventilation - , to accumulate (02) decrease PH , so for alkalosis hypoventilation (breath Slowly - Rapid; the lungs regulate blood levels of Co2 Hyperventilation (Breathing faster), eliminate more CO2 leading to increase pH Hypoventilation: (Slow and shallow breathing), lead to CO2accumulation which decrease pH In case of metabolic acidosis: Respiratory compensation increases the respiratory rate (hyperventilation) to drive off CO2 and readjust the bicarbonate to carbonic acid ratio to the 20:1 level. This adjustment can occur within minutes. In case of metabolic alkalosis: The normal response of the respiratory system is to elevate pH by increasing the amount of CO2 in the blood, by decreasing the respiratory rate (hypoventilation) to conserve CO2. However, There is a limit to the decrease in respiration, that the body can tolerate. Hence, the respiratory route is less efficient at compensating for metabolic alkalosis than for acidosis. reducing => because theres a limit at CO2 The renal/metabolic compensation mechanism Kidneys make long term adjustment to pH. Kidneys reabsorb acids and bases or excrete them into urine and can also produce HCO3 to replenish lost supply In cases of respiratory acidosis (blood is acidic), the kidney increases the conservation of bicarbonate (reabsorption of HCO3-) and secretion of H+.These processes increase the concentration of bicarbonate in the blood, reestablishing the proper relative concentrations of bicarbonate and carbonic acid. In cases of respiratory alkalosis, the kidneys decrease the production of bicarbonate and reabsorb H+ from the tubular fluid. These processes can be limited by the exchange of potassium by the renal cells, which use a K+- H+ exchange mechanism (antiporter transport) 1 look at PH If acidosis ,. whatever is acidosis 2 Examples of simple disorder from CO2 or bicarb You'll choose it Disorder pH HCO3disorder Examples of smple pCO2 7.15 8 24 Low HCO3 and CO2 Metabolic acidosis Low CO2: alkalosis CO2 low bicarbonate low matche (aihalosis) Low HCO3: acidosis Cacidosis) this Respiratory acidosis 7.15 30 90 acidosis high bicarbonate high co2 Callealosis) Lacidos) Well choose this Metabolic alkalosis 7.7 36 48 bicarbonate alkalosis high high coz ~ Callalosis) Cacidosis) Respiratory alkalosis 7.7 12 10 low bicarb low CO2 alkalosis Cacidosis) Calraiosis) v Simple Acid-Base Disorders Arterial blood pH < 7.4 pH > 7.4 Acidosis Alkalosis [HCO3-] < 24 PCO2 > 40 [HCO3-] > 24 PCO2 < 40 mmol/L mm Hg mmol/L mm Hg Metabolic Respiratory Metabolic Respiratory PCO2 < 40 mm Hg [HCO3-] > 24 mmol/L PCO2 > 40 mm Hg [HCO3-] < 24 mmol/L Resp Comp Renal Comp Resp Comp Renal Comp ↓PCO2 by 1.2 mm Hg ↑[HCO3-] by 0.35 mmol/L ↑PCO2 by 0.7 mm Hg ↓[HCO3-] by 0.5 mmol/L /1 mmol/L /1 mmol/L /1 mm Hg Don't need to memorite this Mixed A-B disorders acid-base A mixed acid-base disorder is the simultaneous coexistence of two or more primary acid-base disorders in the same patient. END HCO3- Respiratory Alkalosis Respiratory acidosis >24mM Metabolic Alkalosis Metabolic Alkalosis Metabolic Alkalosis (M) © Respiratory Alkalosis Normal pH Respiratory acidosis 24mM 7.4 Respiratory Alkalosis Respiratory acidosis
