Week 4 - Acids, Fluids, Electrolytes PDF

2023-10-03 midterm review Tuesday October 17th 40MC 60 minutes = bring simple math module l calculator open discussion board for to be 10 tested modulel graphs given + scrap paper module 3 will be tested , have 20 have questions picture Module 21 , on phone 10 (module 3 ph...

2023-10-03 midterm review Tuesday October 17th 40MC 60 minutes = bring simple math module l calculator open discussion board for to be 10 tested modulel graphs given + scrap paper module 3 will be tested , have 20 have questions picture Module 21 , on phone 10 (module 3 photo Body fluids Biomedical Chemistry and Lab Diagnostics Fluids, Electrolytes, Acid-Base 1 2 Osmosis Body fluids • Osmotic potential exists when the concentrations of solute on either side of a semi-permeable barrier are different • Osmosis is the net flow of water across the barrier that equalizes those solute concentrations  Fluids shift between the ICF & ECF to keep body in homeostasis • Water across the body will either be a constituent of the intracellular fluid (ICF) or the extracellular fluid (ECF).  Shift occurs in response to changes in the osmotic concentration of the ECF “Water follows solute” www.Wikipedia.org 3 moves freely 4 1 2023-10-03 Hypo Hyper Osmolality and Tonicity Osmolality • Osmolality: # of solute particles per mass of water (mmol/Kg)* • Osmolality of pure water = 0 • Osmolality of water with solutes > 0 Tonicity • Osmotic potential across a permeable barrier • Water moves from low osmolality to high osmolality • Isotonic: no movement • Hypertonic [high solute]: Water moves out of the cell “Hyper high • Hypotonic [low solute]: Water moves into the cell Hypo Low Toe” *Irrespective of size or kind of particle. Osmolarity cares about volume (mmol/L) Fig 2.2 + 2.3 Ha0 moves out of the cell causing shrivel 5 cellswells - Hao moving Water gain/loss is shared among ECF and ICF into cell 6 Fluid Distribution, Composition, & Transport Fluid shifts between the ECF and ICF are driven by disturbances to ___________ MOTIC _____________. nomostasis OS 7 8 2 2023-10-03 Oncotic Pressure vs Hydrostatic Pressure Oncotic Pressure • Water (and low molecular mass solutes) return to the capillary by osmotic pressure of plasma proteins • Constant along the length of the capillary Hydrostatic Pressure • Water (and low molecular mass solutes) are driven out of the capillary by force generated from the heart • Decreases on the length of the capillary Hydrostatic vs Oncotic Pressure pushed in gets pulled back in High [Plasma protein] High oncotic pressure Low [Plasma protein] Low oncotic pressure osmotic potiental- ↓ osmotic pressure 9 heart pumping = Had being physically pumped out 10 3 2023-10-03 Fluid Distribution, Composition, & Transport Biomedical Chemistry and Lab Diagnostics Although the osmotic concentration of the fluid compartments is equal, the concentration of individual solutes varies. Fluids, Electrolytes, Acid-Base 1 2 Electrolytes Osmolality • Substance that dissociate into ions (carry an electric The osmotic activity of fluids is due to the combined osmotic activity of all the dissolved substances. charge [+/-]) once dissolved in water • Enable variety of cellular functions (muscle contraction, membrane transport, nerve signals, cofactors) • Regulate pH enzyme reaction regulation of , • PH Because water moves freely between the ICF and ECF, the _________ is similar between compartments (under normal osmolality conditions). osmolity should balanced in normal conditions be • Regulate tonicity of blood plasma • Na+ is the major ECF cation Cl- is major ECF anion K+ is the major ICF cation, PO4- is the major ICF anion However, concentrations of individual solutes can be vastly different.These differences are maintained by active transport mechanisms, such as ion pumps. Electrolyte status is checked through serum electrolyte tests, urine tests (Na+, K+), blood gas analyzers (Na+, K+, Ca2+,HCO3- , Cl- ) 3 4 1 2023-10-03 Osmolality & Sodium Osmolality & Sodium We can understand a lot about fluid transport and electrolyte balance by focusing on the major solutes that influence plasma osmolality. Unfortunately, the relationship between osmolality, [glucose] and [Na+] can be complex. • Plasma osmolality is usually measured as… Osmolality = 2 x [Na+] + [glucose] + [urea nitrogen] in _______ mmol/kg • What happens if [serum glucose] is high? • Osmolality increases • Hyperosmolality leads to shift of water from ICF to ECF • Dilutes sodium, and so [Na+] is low. • Hyponatremia. Hyperosmolality can be due to increased serum sodium, glucose, urea, or other clinical conditions in which toxins (e.g., methanol/ethanol) are elevated in serum. Hyperosmolality causes a shift of water from the ICF have hyperosmorality to ECF. loosing fluid can occur 5 6 Osmolality & Sodium Na+ primary cation ECF [Na+]: ~135-145 mOsm/L ICF [Na+]: ~ 10 mOsm/L The movement of water across cell membranes is most affected by the concentration of serum sodium! Let’s look at the relationship between water and sodium in our bodies. 7 Roles: maintaining tonicity of ECF, acid-base balance (renal reabsorption of sodium & excretion of H+), neural + neuromuscular function, water balance For constant [Na+] water gain/loss must be compensated by a loss/gain water. • Na+ excretion depends on glomerular filtration rate. • ↑GFR Nat • ↓GFR Nat • Active controls • Too much Na+? • The body filters more Na+ into urine Too little Na+ ? • Re-absorption of Na+ 8 2 2023-10-03 Osmolality & Sodium Condition Volume Volume Volume (ECF) (ICF) (total body water) Review ! Serum sodium conc. 1 Water excess alone Increases Increases Increases Decreases 2 Water decrease alone Decreases Decreases Decreases Increases 3 Sodium excess alone Increases Decreases No change Increases 4 Sodium deficiency Decreases Increases No change Decreases 5 H2O and Na+ similarly increased Increases No change Increases No change 6 H20 excess > Na+ excess Increases Increases Increases Decreases 7 H20 / Na+ similarly decreased Decreases No change Decreases No change Na+ decrease > H20 deficiency Decreases Increases Decreases Decreases 8 9 3 2023-10-03 Acid-Base Balance: pH pH is the negative logarithm of the H+ concentration. 𝑝𝐻 = −log[𝐻 ] Biomedical Chemistry and Lab Diagnostics Fluids, Electrolytes, Acids + Bases 1 If the [H+] is high, the pH is low (acidic) • If the [H+] is low, the pH is high (alkaline) • The pH scale ranges from 0 to 14 • 0 is very acidic, 14 is very alkaline • Each number represents a factor of 10 • If a solution moves from a pH of 6 to a pH of 5, the [H+] has increased tenfold 2 Regulation of Acid-Base Balance pH in our body must be maintained within a very narrow range  7.35 – 7.45 in arterial blood. The most important reason to maintain normal pH is that many _______ have optimal pH ranges. enzymes Acidosis is malfunction of body systems due to excess acidity (low pH; <7.35). Alkalosis is malfunction of body systems due excess alkalinity (high pH; >7.45). 3 • Regulation of Acid-Base Balance There are two broad classes of acid-base disorders: Respiratory acid-base disorders result from a mismatch between carbon dioxide generation in peripheral tissues and carbon dioxide excretion by the lungs. When a respiratory acid-base disorder is present, the CO2 level in the ECF is abnormal. Metabolic acid-base disorders are caused by the generation of acids or by conditions affecting the concentration of HCO3- in the ECF. 4 1 2023-10-03 Intracellular buffering Regulation of Acid-Base Balance • Changes in intracellular pH are mostly buffered by the proteins of the cytoplasm • Certain amino acid side groups can behave as weak acids and bases • Certain mechanisms of ac ve transport can also be ac vated to ↑↓[H+] in ICF • Following the acute onset of any of these disorders, the body tries to compensate, to restore acid-base balance. • Unfortunately, compensation can interfere with reaching a diagnosis. pKa of His = 6.0 Let’s look at how the body compensates. When pH = 6.0….. disassociation • 50% 50% • Protein folding depends on charge of side chains, which means pH outside normal range can cause denaturation • Most tissues maintain a pH between 7.0-7.4 • Skeletal muscle is better adapted for handling lower pH conditions (6.8-7.1) 5 6 ECF Acid-Base Balance Bicarbonate-Carbonic Acid Buffer System Acid-base balance: Normal body function requires that [H+] is regulated within pH range of 7.35-7.45 3 body systems work together in maintaining the carbonic-acid bicarbonate buffer system 1. Blood buffer: shifts in response to excess acids & base, 2. Respiratory Buffer: lungs excrete acid in the form of CO2, 3. Renal Buffer: kidneys excrete H+ or regenerate/reabsorb HCO3- Rxn 1 Rxn 2 Imbalance (excess gain) Accumulation Accumulation Leftwards increase <H = " Rightwards increase CO2 amount bicarbonate Respiratory compensation focuses on this end Renal compensation focuses on this end Imbalance (excess loss) Depletion Depletion Leftwards decrease 7 8 general rule : what Rightwards decrease happens o one end it will ripple on the other side 2 2023-10-03 CO2 Transport Physiological management of CO2  Excess CO2 combines with H2O  H2CO3  For blood to maintain its proper pH range there must be 20:1 of HCO3- : H2CO3 • Aerobic respiration produces CO2 as a waste product • CO2 (nonpolar) diffuses freely out of cells along its concentration gradient into ECF and RBC • In RBC…. the CO2 is biochemically recycled into HCO3- (a base which your body needs to maintain its pH balance) • In ECF…. CO2 diffuses down its concentration gradient into the lungs. Ventilation expels CO2, speed and depth of breathing controls rate of expulsion remember 20 : 1 ratio that must be maintained to keep normal ranges/levels of PH Respiratory compensation:  ↑ H2CO3 causes ↑ depth and rate of respira on to reduce the C02, PH this reduces the carbonic acid and adjusts the blood pH respirations  ↓ H2CO3 causes respira on to ↓ and become shallow thereby apH retaining C0 , this increases the carbonic acid and adjusts the blood 2 pH • Activation of the lungs to compensate starts to occur within 1 – 3 minutes of a significant pH change ~ Renal Compensation: • ↑CO2 = ↑H+ excre on, ↑HCO3- retention 9 10 Physiological management of HCO3- Regulation of Acid-Base Balance  Four major classifications: Normal range of HCO3- is 22 – 26 mEq/L  Measuring HCO3- indicates the alkaline reserve (ability to buffer •  The significance of HCO3- readings are opposite of CO2: a high HCO3(>26mEq/L) indicates alkalinity and a low reading (<22mEq/L) indicates acidity ____________ acidosis develops when the respiratory system cannot eliminate respiratory all the CO2 generated by peripheral tissues (e.g., asthma, CNS disorders, impaired respiration, decreased circulation). • ____________ alkalosis develops when respiratory activity lowers plasma CO2 respiratory to below-normal levels (e.g., drug stimulation of respiratory centres, emotional states like anxiety, hypoxia) • Renal compensation solves most acid-base imbalances (but may take hours to days to fully correct imbalance) • metabolism ____________ acidosis develops either due to the excess production of acids, impaired secretion of H+ at kidneys or loss of bicarbonate (e.g., diabetic ketoacidosis, lactic acidosis). • metabolism ____________ alkalosis occurs when HCO3- concentrations become elevated (hyperkalemia, antacids, hyperaldosteronism). acid) baseline buffer for acidty HCO3- alkalizes blood H+ acidifies blood H+, reabsorb HCO3- When in acidosis: excrete more more When in alkalosis: reduce excretion of H+, don’t reabsorb HCO3- 11 12 3 2023-10-03 Lungs + Kidneys are responsible for control of Acid-base balance Regulation of Acid-Base Balance Respiratory disorders Compensation in response to respiratory acidosis ↑CO2 Respiratory acidosis • CAUSE: Hypoven la on ↑PCO2 (>45 mmHg) • head/spinal cord injury, drugs/medications, pulmonary diseases, chest wall trauma • EFFECT: lowering of the blood pH (< 7.35) • COMPENSATION: • Activates renal compensation (increased reabsorption of HCO3- and secretion of H+) 13 14 Lungs + Kidneys are responsible for control of Acid-base balance Regulation of Acid-Base Balance Respiratory disorders Compensation in response to respiratory alkalosis Respiratory alkalosis • CAUSE: Hyperven la on ↓PCO2 (<35 mmHg) • Stroke, Anxiety-hyperventilation syndrome, pain, stress, drugs, pulmonary embolism, pneumonia, asthma, pulmonary edema, fever, high altitude • EFFECT: increase in the blood pH (>7.45) • COMPENSATION: Activates renal compensation (Solved by letting HCO3- filter freely through glomerulus into urine) 15 16 4 2023-10-03 Lungs + Kidneys are responsible for control of Acid-base balance Regulation of Acid-Base Balance Compensation in response to metabolic acidosis Metabolic disorders lose of buffer : Part I loss of bicarbonate Metabolic acidosis: (HCO3-<22 mEq/L) • CAUSE (excess acid): Ingestion/production of acids in excess of kidney capacity for excretion (diabetic ketoacidosis, renal disease, drug use) • CAUSE (loss of basic buffer): Severe diarrhea (Loss of HCO3-) • EFFECT: pH< 7.35 • EFFECT: Bodily reserves of HCO3- will eventually be depleted if continually used to buffer H+ causing PH • COMPENSATION: • Activates Respiratory compensation (Hyperventilation depletes CO2) 17 18 Regulation of Acid-Base Balance Lungs + Kidneys are responsible for control of Acid-base balance Compensation in response to metabolic acidosis Metabolic disorders Part 2 generating only' not 20 to maintan normal Metabolic alkalosis (HCO3 >26 mEq/L) PH leVelS I Balance • CAUSE: Loss of H+ (excessive vomiting, gastric suction, medications) • CAUSE: Retention of HCO3• EFFECT: An increase in pH value (>7.45) reasoning : bicarbonate = pH levels • COMPENSATION: Respiratory compensation (Hypoventilation preserves CO2) But pushing the rxn rightwards creates HCO3- while replacing lost H+ !(that’s fine we’ll try to get rid of in HCO3 urine) 19 20 5 2023-10-03 Regulation of Acid-Base Balance Compensation in response to metabolic alkalosis Acid-base testing When we are assessing the acid-base status of a patient, the primary questions that we are asking are: 1. Is the patient’s acid-base status normal or is the patient in acidosis or alkalosis.  This is the simplest question. • pH < 7.35 = acidosis • pH > 7.45 = alkalosis 2. Is the disorder metabolic or respiratory in origin? 3. Is the normal compensatory mechanism at work? 4. How effective is the compensatory mechanism? 21 Acid-base testing Steps in diagnosis of acid-base disorders 22 Important measures for analysis of arterial blood gasses 1) Collect three measurements • pH • [HCO3-] • PCO2 partical pressure of CO2 Acid-base Testing pH needs to be tested immediately after specimen collection Red blood cells are not ‘proper’ cells -Anucleate -No Mch -All energy from anaerobic respiration (glycolysis) -Glycolysis produces Lactic acid which will change pH of sample 23 O2 and CO2 status changes across cardiovascular system. mostly discussed and PaO2 & PaCO2 – Partial pressures of O2 and CO2 dissolved in arterial blood PvO2 & PvCO2 – Partial pressures of O2 and CO2 dissolved in venous blood referenced I 24 6 2023-10-03 Acid-base testing Steps in diagnosis of acid-base disorders 1) Collect three measurements • pH • [HCO3-] • PCO2 Steps in diagnosis of acid-base disorders 2) Evaluate pH: Acidosis or alkalosis? >7.45 alkalosis, <7.35 acidosis Normal Is it normal? pH 7.35-7.45 22-26 mEq/L 35-45 mm Hg 3) Establish metabolic or respiratory? [HCO3-] >26 mEq/L Metabolic PCO2 <35 mm Hg Respiratory [HCO3-] <22 mEq/L Metabolic PCO2 >45 mm Hg Respiratory pH Acidic 7.35-7.45 Basic [HCO3-] Acidic 22-26 mEq/L Basic PCO2 Is it basic because of metabolic alkalosis or respiratory alkalosis? Is it acidic because of metabolic acidosis or respiratory acidosis? Basic 35-45 mm Hg Acidic **** You must know the range, and which end of each range corresponds to acidic or basic conditions***** 25 26 Arterial Blood Gas problems (using Tic Tac Toe Method) Steps in diagnosis of acid-base disorders 4) Is compensation occurring? If respiratory alkalosis then we should see metabolic acidosis in response Normal Range Respiratory alkalosis- If [HCO3-] <22 mEq/L then YES Metabolic alkalosis- If PCO2>45 mm Hg then YES If metabolic alkalosis then we should ACIDIC pH 7.35-7.45 NORMAL BASIC PH [HCO3-] 22-26 see respiratory acidosis in response PCO2 35-45 PCO2 respiratory Example 1: The following measures are taken from a patient: pH 7.33, PaCO2 60mm Hg, HCO3- = 34 mEq/L If respiratory acidosis then we should Respiratory acidosis- If [HCO3-] >26 mEq/L then YES see metabolic alkalosis in response Metabolic acidosis- If PCO2 <35 mm Hg then YES If metabolic acidosis then we should see respiratory alkalosis in response Step 1: Label your values pH 7.33 is ACID PaCO2 60 is ACID HCO3- 34 is BASE If you want more instruction on Tic Tac Toe method click here to watch a video tutorial 27 28 7 2023-10-03 Arterial Blood Gas problems (using Tic Tac Toe Method) Normal Range ACIDIC pH 7.35-7.45 pH NORMAL [HCO3-] 22-26 PCO2 35-45 Arterial Blood Gas problems (using Tic Tac Toe Method) BASIC ACIDIC pH 7.35-7.45 pH NORMAL [HCO3-] 22-26 PCO2 35-45 HCO3- BASIC HCO3- PCO2 respiratory acidois Example 1: The following measures are taken from a patient: pH 7.33, PCO2 60mm Hg, HCO3- = 34 mEq/L PaCO2 Example 1: The following measures are taken from a patient: pH 7.33, PaCO2 60mm Hg, HCO3- = 34 mEq/L Step 2: Interpret chart Step 2: Put them in the correct column pH 7.33 is ACID PaCO2 60 is ACID HCO3- 34 is BASE ACIDIC, pH and PCO2 all line up. TIC TAC TOE, we have respiratory acidosis Is compensation occurring? Yes, the HCO3- is alkalotic, which means the body is trying to compensate through metabolic alkalosis If you want more instruction on Tic Tac Toe method click here to watch a video tutorial 29 If you want more instruction on Tic Tac Toe method click here to watch a video tutorial 30 Arterial Blood Gas problems (using Tic Tac Toe Method) Normal Range ACIDIC pH 7.35-7.45 pH [HCO3-] 22-26 PCO2 35-45 NORMAL Arterial Blood Gas problems (using Tic Tac Toe Method) BASIC Normal Range ACIDIC pH 7.35-7.45 HCO3- NORMAL BASIC pH [HCO3-] 22-26 HCO3- PCO2 Example 1: The following measures are taken from a patient: pH 7.33, PCO2 60mm Hg, HCO3- = 34 mEq/L Step 3: Interpret chart ACIDIC, pH and PCO2 all line up. TIC TAC TOE, we have respiratory acidosis Is compensation occurring? Yes, the HCO3- is alkalotic, which means the body is trying to compensate through metabolic alkalosis HOWEVER- the pH is still abnormal which means it is only PARTIALLY COMPENSATED PCO2 35-45 PCO2 Example 2: The following measures are taken from a patient: pH 7.43, PCO2 60mm Hg, HCO3- = 34 mEq/L Step 3: Interpret chart When HCO3- , pH and PCO2 are in different columns. TIC TAC TOE, we are FULLY COMPENSATED But is it respiratory or metabolic? Ask if pH closer to acidic or basic end of spectrum? 7.43 is closer to basic end of range…. So we have fully compensated metabolic alkalosis If you want more instruction on Tic Tac Toe method click here to watch a video tutorial 31 Normal Range If you want more instruction on Tic Tac Toe method click here to watch a video tutorial 32 8 2023-10-03 Arterial Blood Gas problems (using Tic Tac Toe Method) Normal Range ACIDIC NORMAL BASIC pH 7.35-7.45 pH [HCO3-] 22-26 HCO3- PCO2 35-45 PCO2 Example 3: The following measures are taken from a patient: pH 7.47, PCO2 40mm Hg, HCO3- = 34 mEq/L Step 3: Interpret chart When HCO3- , pH and BASIC all line up. TIC TAC TOE, we are in metabolic alkalosis Compensated? NO Body has not responded with respiratory acidosis therefore we have: UNCOMPENSATED metabolic alkalosis If you want more instruction on Tic Tac Toe method click here to watch a video tutorial 33 9 2023-10-03 ABG Problems basic normal normal acidic Interpret these patient results: 1. Patient 1: pH 7.48; PCO2 42mm Hg; HCO3- 30 mEq/L 2. Patient 2: pH 7.42; PCO2 33mm Hg; HCO3- 18 mEq/L PH 7 35 . ranges : 7 45 . 22-26mEqL fully compensated 3545MMH9 How these problems will look in a test situation: 3. Gideon is a 74-year-old male admitted to the unit with COPD. His ABG measures are: pH 7.31; PaCO2 52mm HG; HCO3- 28 mEq/L. What acid-base balance condition is he in? – A. Fully compensated respiratory acidosis – B. Uncompensated metabolic alkalosis – C. Partially compensated respiratory acidosis – D. Uncompensated respiratory acidosis – E. Partially compensated metabolic acidosis 1 1