Acid-base chemistry and its disturbances MUDr. Stanislav Matoušek, PhD System of the presentation •Difficult subject? •Gradual steps good understanding, building on what I already know •Active learning: •Slide with questions to solve – give it time, try to find solutions by yourself •Minimum time is below •Answers – mostly next slide •Why active learning? •Greater joy and interest (in the end) •Deeper knowledge •Remembering longer •èThe extra effort pays off • Acidobazická rovnováha má pro mnohé pověst obtížné oblasti fyziologie a patofyziologie. Žádný „strašák“ to ale být nemusí, naopak to může být krásná oblast medicíny. K dobrému učení a pochopení této oblasti použijeme několik fines. Jednak – v této oblasti více než v jakékoliv jiné je důležité postupovat postupně, krok za krokem – pokud něco dobře pochopím, tak na tom mohu stavět. Pro dobré pochopení daného kroku je nesmírně důležité aktivní učení, které Vám v této prezentaci nabídnu. Bude to vypadat následovně: Na jednom slidu Vám budu prezentovat daný problém formou otázek, na které hledejte sami odpovědi, zamyslete se nad nimi. Věnujte tomu prosím milimálně čas, který je v dolní části slidu! Poté překlikněte na další slide, kde si správnou odpověď můžete zkontrolovat . Pokud jste si správnými odpověďmi jistí, můžete následující slide přeskočit. V takovém případě také můžete zkrátit čas. Pokud se opravdu tímto způsobem zapojíte do učení, budete mít nejen mnohem větší radost z výsledku, ale také budete jednotlivým částem ABR rozumět mnohem více do hloubky a budete si je déle pamatovat. Tak tedy, pojďme na to. Acid-base Chemistry and Physiology Refresher (hopefully) Hydrogen ions •Is the concentration of hydrogen ions in extracellular fluid (ICF) small, large, huge or minuscule? •Why is maintaining H+ concentration within narrow limits much more important than maintaining strict concentrations of let’s say iodine or zink1? •Is it more accurate to speak of H3O+ or H+? Why? •What is a hydrogen bond (H bond)? •Is there more H3O+ or OH- in plasma under physiological conditions? •Minimum time: 2 min • 1.Hint: Focus on properties of certain biomolecules as well as properties of water itself. Hydrogen ions •Concentration of H+ = [H+] ~ 1 000 000x << [Na+] – minuscule •Maintaining pH within tight limits is important because of very large reactivity of H+ and its effect on the conformation of many macromolecules, especially proteins. •Hydrogen bond – special type of weak chemical bond created by H+; it binds H20 molecules together àliquefaction of water • pHplasma,Norm ≈ 7,4 > 7,0 → alkaline pH → [OH-] > [H3O+] Vodíkový můstek je speciální slabá chemická vazba, která způsobuje vazbu vodíků v molekule H[2]0 na vedlejší molekuly. Díky vodíkovým můstkům je voda za běžkého tlaku a teploty kapalinou a nikoliv plynem. Dynamics of H3O+ and OH- movement in water + + Amino-acid charge and protein conformation Cyclin-dependent kinase 6 (CDK6) bound to the inhibitor ribociclib. Enzyme involved in cell cycle regulation and target of several antitumoral drugs. 3D rendering based on protein data bank entry 5l2t. Atoms are represented as spheres with conventional co Stock Photo - 78436755 Obrázek(9597750): Mozku anatomie. | Autor: Andreus https://upload.wikimedia.org/wikipedia/commons/thumb/e/ef/Human_heart_outside.svg/220px-Human_heart _outside.svg.png StandaObrazekHistidineAminoAcid.jpg Crucial organs: StandaObrazekCysteineHistidine.png pKA = 6,05 pKA = 9,2 pKA = 8,2 pKA =4,25 Conformation change Dysfunction pH definition and its consequences •Would you remember how pH is defined? •And what are rules of calculating with logarithms? E.g. log(A x B) = •Try to figure out what these rules imply for the pH behavior: For instance, when H+ concentration (denoted as [H+]) increases two times, how does pH change?1 •How does pH change, when the H+ concentration decreases 10x? •For straight-A students: How does pH change, when [OH-] increases 2x? • •Minimum time: 3 minutes or until completion of all tasks. • • •1) You might find it helpful to know that log10(2) = 0.3 • • • • pH definition and its consequences - solution •pH = - log10([H+]) •log(AB)= log(A) + log(B) •H+ concentration increasing twice: [H+]New = 2[H+]Old •From the pH definition and the logarithm calculation rules: • pHNew = - log([H+]New ) = - log(2 x [H+]Old ) = - log(2) + (- log ([H+]Old) = •= -0,3 +pHOld •èTherefore: If H+ concentration doubles: pHNew = pHOld – 0,3 •When [H+]New = 1/10 x [H+]Old : pHNew = - log(1/10) + (- log ([H+]Old)= •= +1 +pHOld . If [H+] decreases ten times, pH goes up by 1. • • Buffers •What are buffers and what their effects in a solution are? •How do buffers influence pH change, when acid or base is added? •What does pKa of a simple buffer denote? •For straight-A students: Can you write down the mass action equation of a simple buffer? •Which pH does render a single substance buffer most effective? • •Minimum time: 3 minutes Buffers – Solution 1 •Buffers inhibit the pH change by binding the extra H+ when their concentration increases (when pH falls) and releasing H+ when [H+] decreases (pH goes up). •They are crucial for stabilizing pH within certain range! •Hydrogen ion and buffer react according to the formula: •HB H+ + B- or: • HB+ H+ + B •Reaction equilibrium concentra-tions can be expressed by the well-known mass action formula: • • •This can be expressed in the logarithmic form as well: • • • [HB] and [B-] are in 1:1 ratio, when pH = pKA •(prove this using the previous relationship) • • Buffers – Solution 2 •Single-substance buffer is most effective when the pH coincides with its pKA . •Efficiency of a buffer at a given pH can be measured by its buffer capacity β. •When pH and pKA fall far, the efficiency of the buffer is constrained by the buffer component that is low in concentration. •For instance, at acidic pH, there is ↓[B-], •At alkalic pH, there is ↓[HB] • •For straight-A students: How does the [B-]/[HB] ratio change when acid is added at pH far from its pKA? Does it change a lot or a bit? • • • • Buffer capacity β : (decreases with distance from pKA) pKA Titration Curve expressed as [B-] vs. pH [B-] at a given pH [B-] [HB] StandaObrazekHistidine.png Protein Buffers •Principal buffers in blood are: •Hemoglobin! •Albumin, and other proteins of blood plasma •Key buffer residues are histidine side chains. •pKA’s of individual histidine side chains differ significantly (influence of surrounding aminoacids) • • pK9 pK15 pK10 pK13 pK11 pK8 pK12 pK7 pK5 pK3 pK1 pK2 pK14 pK16 pK6 pK4 4.85 5.2 5.75 5.82 6.17 6.35 6.73 6.75 7.01 7.10 7.12 7.22 7.3 7.3 7.31 7.49 Tab: pKA’s of 16 histidine side chains in the albumin molecule (ordered) Consequence: Virtually linear protein titration curve. Buffer capacity is almost constant over a wide range of pH. Protein Buffers Titration curve of a simple buffer Phosphate Buffer •Principal intracellular buffer •Incl. phosphate residues of DNA • •The 2nd dissociation step is important, having pKA = 7.2 • StandaObrazekHistidine.png Bicarbonate Buffer Zjistěte, jak si pročistit plíce během 72 hodin - ČeskoZdravě.cz | Lungs drawing, Lunges, Drawings Bicarbonate Buffer Possible depiction of reaction equilibria (as described by Henderson-Hasselbalch equation): CO2+H2O H2CO3 H+ + HCO3- CO2 H2CO3 HCO3- H+ pH= 7,4 HCO3- CO2 H+ pH= 7,4 Magnifying glass: Concentrations in order of 10 nmol/L Metabolism and the System of Regulating Acid-base Status •The biggest turnover is in the system of CO2 •Thus pCO2 can be easily regulated. CO2 behaves as an open system •Other flows and the relationship with concentrations of other ions (electro-neutrality) are depicted in the figure: schema-acidobaze.jpg Bicarbonate Buffer •It is the principal buffer in terms of longer-term regulation of H+ balance in the body. •Lungs – regulate pCO2 •Kidneys – regulate the level of HCO3- in blood plasma and excretion of H+ Primary Disturbance When H+ = 40 nmol/L Compensation Respiratory Acidosis ↑pCO2 Reacts to the right -↑H+ Kidneys - ↑HCO3-, ↑BE Metabolic Acidosis ↓HCO3- (or ↑↑↑H+ ) Reacts to the right when primary cause ↓HCO3- (Reacts to the left when primary cause ↑↑↑H+ ) –end result - ↑H+ Lungs - ↓pCO2 Respiratory Alkalosis ↓pCO2 Reacts to the left - ↓H+ Kidneys - ↓HCO3-, ↓BE Metabolic Alkalosis ↑HCO3- Reacts to the left -↓H+ Lungs - ↑pCO2 Base Excess - BE •Base Excess – a very precise measure of metabolic disturbances (and metabolic compensations) •Underlying logic: Lungs regulate pCO2 . This regulation does not influence the total concentration of base forms of buffers. •By definition: When pH = 7,4 (norm) and pCO2 = 5,3 kPa (norm), then BE = 0 mmol/L •Now, when we add 10mmol/L of acids, part of this amount reacts away with bicarbonate and part with the B- form of nonbicarbonate buffers – BE decreases to -10 mmol/L •Conversely, taking away 15 mmol/L of acids (H+) when BE =0 increases both the level of bicarbonate and the B- of non-bicarbonate buffers – BE increases to +15 mmol/L •The value of BE is independent of subsequent changes in pCO2 • • • • System of Buffers and Electroneutrality Gamblegram.png Buffers Bicarbonate Albumin „Strong“ ions - Inert in terms of acid-base Electroneutrality: When buffer concentration changes – the concentration of strong ions has to change as well AG AG = Anion gap = Na+ + K+ - Cl- - HCO3- Parameter used in differential diagnosis of metabolic acidoses X- - (ordinarily) unmeasured ions –e.g. lactate, keto-, SO42- Na+ Cl- K+ Ca++,Mg++ System of Buffers and Electroneutrality 2 – Example HCO3- Alb- Kostým - Běžec Smiffys.com Vysoké Tatry: zajímavosti, atrakce a tipy na výlety | Kiska Travel Runner in High Tatras: HLac Lac- H+ HAlb ← Alb- + CO2 ← HCO3-+ Part of X- Production of lactic acid in muscles X- Pathophysiology of ABB disturbances + clinical examples Kreslené vtipy | Loupak.cz Respiratory Disturbances and their Compensation • ledviny ledvinove kameny zanet ledvin kolika procisteni ledvin byliny bylinky babske rady Respiratory Alkalosis and its Compensation HCO3- CO2 H2CO3 H+ Zjistěte, jak si pročistit plíce během 72 hodin - ČeskoZdravě.cz | Lungs drawing, Lunges, Drawings Cause: Hyperventilation 5,3 kPa 2,7 kPa 40 nmol/l 20 nmol/l pH = 7,4 pH = 7,7 Kidney (metabolic) compensation: Takes 2- 3 days to develop Kidneys excrete less H+ and more bicarb. = less bicarbonate returns to blood Alkalosis: Thanks to the compensation the [H+] and pH return closer to norm pH= 7,4 Compensation diagrams and rules • Compensation Diagrams https://png2.cleanpng.com/sh/c9e7b10c7e22fda41425b426ce85a1c8/L0KzQYm3VsE2N5d0gJH0aYP2gLBuTfFkcZVne eVuLYLocbT7if9vNZ90hdHwcnHwPbLqifRjaaRqRdp4bXXyg8XoTfR2bV5peeZuLUXlQoSAVfQ3P2dpfqY9LkG8SIGBV8gzOWY3 UaIAMEW7QoWBVskveJ9s/kisspng-acidbase-reaction-nomogram-acidbase-homeosta-due-date-5b2375d676df44.1 980878215290505824869.png HCO3- CO2 H2CO3 H+ Compensation Diagrams 2 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 10 20 30 40 50 60 70 80 90 PCO2 torr Base Excess mmol/l Acute metabolic acidosis Acute metabolic alkalosis Compensation Diagram pCO2 vs BE – Different Interpretation - Acid Base Tutorial “Boston” Rules for Diagnosing ABB Disturbances Alternative to the compensation diagrams - however, you have to remember them L For straight-A students - optional: This is for pCO2 expressed in mmHg – convert to a version in kPa (pCO2 40 mmHg = 5,3 kPa) Respiratory Acidosis and its Compensation ledviny ledvinove kameny zanet ledvin kolika procisteni ledvin byliny bylinky babske rady HCO3- CO2 H2CO3 H+ Zjistěte, jak si pročistit plíce během 72 hodin - ČeskoZdravě.cz | Lungs drawing, Lunges, Drawings Cause: Hypoventilation Part of global respiratory insufficiency (insufficiency type II) pH = 7,1 pH = 7,4 Acidosis: Kidney (metabolic) compensation: Takes 2- 3 days to develop Kidneys excrete more H+ = returning more bicarbonate into blood Thanks to the compensation the [H+] and pH return closer to norm 10,6 kPa 5,3 kPa 80 nmol/l 40 nmol/l Case Study No. 1 •You examine a 20 YO student at the hospital admission. •Cannot concentrate and even could not move her fingers for a brief moment (which scared her). Still feels strange pins and needles in her fingers. • She has not been seriously ill until now, no medication •Physical examination – normal •SA: She has split with her boyfriend recently, had been together for 4 years. Difficult to go thru. •Lab: pH = 7.49 •pO2 = 13.4 kPa •pCO2 = 4.1 kPa •HCO3- = 22 mmol/L •BE = -1 mmol/l What acid-base disturbance this is? What kind of acute problem do we see here? What would be your advise her? Possible Causes of Respiratory Alkalosis •Hyperventilation •A) At hypoxemia •High altitude disease •Right-left pulmonary shunting •And ventilation-perfusion dysbalance similar to shunt •With artificial ventilation • •B) Respiratory center irritation •Trauma, inflammation, salicylates. • •C) Panic attack • • Case study No. 2 •68 year old male comes to your ambulance. •History of chronic bronchitis and pulmonary emphysema. •Mild dyspnea, COVID antigen test negative •Lab: pH = 7.31 •pO2 = 8.0 kPa •pCO2 = 10.6 kPa •HCO3- = 38 mmol/L •BE = 12 mmol/L What kind of acid-base disturbance do we deal with? It this an acute a chronic problem? Possible Causes of Respiratory Acidosis •Decreased alveolar ventilation •A) Respiratory center depression •Drugs, medicaments (e.g. opioids) •Damage or ischemia: •Trauma •Stroke •Tumor •Cerebral edema / increased intracranial pressure •B) Nerve or muscle disease •Myasthenia gravis •Polyradiculoneuritis •Serious obesity/ Pickwickian syndrome • •C) Lung disease •Restrictive diseases •ARDS •Pulmonary fibroses •Obstructive diseases •Astma •Tumor •Foreign body •Increase in dead space •Pulmonary embolism •Pulmonary emphysema •Trauma, pneumothorax, • serial rib fractures •Increased pCO2 in the inspired air • What is Taken and Assessed? •Blood Gases Measurement in Arterial Blood (so called „Astrup“) •Serum electrolytes •Concentrations of buffers (e.g. hemoglobin) and other parameters Blood Gases Measurement – „Astrup“ •Assessed by the machine (sensors = selective electrodes): •pH = 7,4 ± 0,04 •pCO2 = 5,3 kPa •pO2 = 13,3 kPa • •Calculated by the machine: •[HCO3-] = 24 mmol/l • calculated using HH equation •BE = 0 mEq/l •Base Excess, Hb concentration is needed for the calculation. Metabolic Disturbances and their Compensation • Thanks to the compensation the [H+] and pH return closer to norm Uncompensated metabolic acidosis: H+ HCO3- CO2 H2CO3 pCO2 = 5,3 kPa H+ < million times ↑ < < Concentration in order of 10 mmol/L X- pH= 7,4 Zjistěte, jak si pročistit plíce během 72 hodin - ČeskoZdravě.cz | Lungs drawing, Lunges, Drawings Metabolic Acidosis 1 + Compensation Zjistěte, jak si pročistit plíce během 72 hodin - ČeskoZdravě.cz | Lungs drawing, Lunges, Drawings Hyperventilation as a compensation of acidosis: Kussmaul breathing Concentration in order of 10 nmol/L AG = Na+ + K+ - Cl- - HCO3- (does not include X-) è AG is equivalent to X- Metabolic Acidosis 2 + Compensation H+ Thanks to the compensation the [H+] and pH return closer to norm HCO3- CO2 H2CO3 pCO2 = 5,3 kPa Zjistěte, jak si pročistit plíce během 72 hodin - ČeskoZdravě.cz | Lungs drawing, Lunges, Drawings Zjistěte, jak si pročistit plíce během 72 hodin - ČeskoZdravě.cz | Lungs drawing, Lunges, Drawings Hyperventilation as a compensation of acidosis: Kussmaul breathing pH= 7,4 Cl- Compartment border AG = Na+ + K+ - Cl- - HCO3- Uncompensated metabolic acidosis: Case Study No. 3 •38 yo female, DM 1st type •Chills and fever lasting several days •She has not felt well --> not eaten much à not taken much insulin •During admission day: Abdominal cramps, vomited several times •Physical exam: BF 30 min-1, HF 112 min-1, BP 110/70 lying and 100/60 standing, 37 °C, •Dry mucosae and fruity breath odor • • •What acid base disturbance do we deal with? Is it a compensated disturbance? •What else could be said about her hydration and ion concentrations? • Lab: pH 7.20 pO2 12.8 kPa pCO2 2.8 kPa HCO3- 8 mEq/L Glc 15 mmol/L Na+ 148 mEq/L K+ 5.5 mEq/L Cl- 110 mEq/L Positive aceton in urine Metabolic Acidosis-Compensation Diagrams https://png2.cleanpng.com/sh/c9e7b10c7e22fda41425b426ce85a1c8/L0KzQYm3VsE2N5d0gJH0aYP2gLBuTfFkcZVne eVuLYLocbT7if9vNZ90hdHwcnHwPbLqifRjaaRqRdp4bXXyg8XoTfR2bV5peeZuLUXlQoSAVfQ3P2dpfqY9LkG8SIGBV8gzOWY3 UaIAMEW7QoWBVskveJ9s/kisspng-acidbase-reaction-nomogram-acidbase-homeosta-due-date-5b2375d676df44.1 980878215290505824869.png HCO3- CO2 H2CO3 H+ pH= 7,4 Draw our patient status into the compensation diagram and model her situation with the beakers pH 7.20 pO2 12.8 kPa pCO2 2.8 kPa HCO3- 8 mEq/L Possible Causes of Metabolic Acidosis A)Loss of bicarbonates due to increased acid buffering •Ketoacidosis •Diabetic •Alcohol •Starving •Lactic Acidosis •Enormous physical strain •Circulatory shock / systemic ischemia •Allogenic substances •Salicylate poisoning •B) Loss of bicarbonates into the third space/out of body •Through intestines •Diarrhea • Fistulas and stomias •Through kidneys (loss of regulation) •So called Renal tubular acidoses •Renal failure (can have ↑AG) • • • AG (anion gap) is increased!: Anion of the buffered away acid accumulates in the body. The difference in common strong ions reflects ↓ HCO3- E.g. ↑ Cl- (instead of the bicarbonate)- so called „hyperchloremic acidoses“ (Or there can be e.g. ↓ Na+ or..) AG (anion gap) is normal! Exercise – Metabolic Alkalosis •Try to derive the beaker chart of metabolic alkalosis and its compensation by yourself. (result can be checked on the next slide) Interpretation - Acid Base Tutorial Cl- Zjistěte, jak si pročistit plíce během 72 hodin - ČeskoZdravě.cz | Lungs drawing, Lunges, Drawings Metabolic Alkalosis + Compensation HCO3- H+ Thanks to the compensation the [H+] and pH return closer to norm pH= 7,4 CO2 H2CO3 Compensation of metabolic alkalosis by hypoventilation is limited by hypoxia Compartment border (e.g. stomach mucosa) Clinically, it is often referred to as: „Hypochloremic“ alkalosis Interpretation - Acid Base Tutorial Metabolic alkalosis and its compensation Possible Causes of Metabolic Alkalosis •Loss of acid by vomiting •↑ HCO3- produced by stomach into the blood (when H+ is secreted into the lumen). •Increased renal HCO3- production/ increased urine H+ secretion •Hyperaldosteronism •So called Bartter syndrome •Liver failure (↓production of urea from NH4+ - the reaction would be acidifying) •Non-adequate infusion of bicarbonates/ Ringer lactate. • Pathogenesis of Paradoxical Aciduria and Loss of K+ after Severe Vomiting •Clinacally important! •After profuse vomiting, hyperchloremic metabolic alkalosis develops •Under normal circumstances, kidneys should regulate and produce only slightly acidic or alkaline urine. •Instead, kidneys can worsen the alkalosis •See next slide: H+ Cl- + K+ H+ K+ H+ Paradoxial Aciduria Potassium depletion Chloride depletion Increased loss of potassium Intracellular fluid Primary cause: Loss of Cl- and H+ by vomiting Metabolic alkalosis Na+ H+ Cl- Cl- K+ K+ H+ Na+ Na+ Glomerular filtrate: hypochloremic metabolic alkalosis Reabsorption of sodium with chlorides is diminished Sodium more available to be exchanged for potassium and H+ Potassium excretion increased and despite the metabolic alkalosis there is aciduria Remaining sodium is exchanged for potassium a H+ Na+ Cl- Cl- K+ K+ H+ H+ Na+ Na+ Glomerular filtrate: Normal situation Reabsorption of sodium with chlorides NH4+ obr. 13.42 Patogeneze vzniku paradoxní acidifikace moči a deplece draslíku po ztrátách chloridů při těžkém zvracení. Summary 1.Physiology and chemistry •H+, pH, buffers, buffers incorporated into metabolism, HH equation, electroneutrality 2.Disturbances divided into respiratory and metabolic 3.Clinical examples and causes 4. • Primary disturbance Compensation Respiratory acidosis ↑pCO2 Renal - ↑HCO3-, ↑BE Metabolic acidosis ↓HCO3- Pulmonary - ↓pCO2 Respiratory alkalosis ↓pCO2 Renal - ↓HCO3-, ↓BE Metabolic alkalosis ↑HCO3- Pulmonary - ↑pCO2 Thank you for your attention