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Water, Electrolyte & Prof. Mehdi Hasan Mumtaz Acid-Base Balance
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BALANCE Water Balance Electrolyte Balance. Acid Base Balance. Nutritional Balance.
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TOTAL BODY WATER 42L IVS ISS ICS 5L 14L 23L
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FLUID THERAPY CELL CAPILLARY EG OSMOLALITY Na + COP INTRACELLULARINTERSTITIAL VASCULAR
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FLUIDS IVSISSICS 1L 5% Dextros 5/42 X 1000 = 120ml 14/42 X 1000 = 333ml 23/42 X 1000 = 547ml 1L Nacl 0.9% 5/19 X 1000 = 263ml 14/19 X 1000 = 737ml - 1L Colloid containing solution 5/5 X 1000 = 1000ml --
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ACID-BASE BALANCE Terminology. Physiologic Compensation By Body. Pathophysiologic Disturbances. Practical Approach To Assessment. Biochemical Reports & Case Histories.
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DEFINITION OF TERMINOLOGY ACID- STANDARD BICARBONATE. BASE- BUFFER BASE & BASE DEFICIT. ALKALI BUFFERING & BUFFER. PH. 24 x PCO 2 (mmHg) H + (nmol/L)=- ----------------------------- HCO 3 (meq/L) (40nmol/L)
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PRODUCT OF METABOLISM H ++ - Anaerobic Metabolism. CO 2 - Aerobic Metabolism.
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PHYSIOLOGIC COMPENSATION HYDROGEN IONS. Incoporation in water. H + +HCO 3 H 2 C 3 O CO 2 + H 2 O. Loss from body. Kidney – regeneration of HCO 3. Intestine. CO 2. Chemoreceptors in hypothalamus. HCO 3. HCO 3 generation by erythrocytes. HCO 3 re-absorption in renal tubules. HCO 3 generation in renal tubules.
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BICARBONATE GENERATION BY ERYTHROCYTES Cl — HCO - 3 CO 2 Cl — - HCO 3 +H + CO 2 +H 2 O HHB Hb
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BICARBONATE REABSORPTION BY KIDNEY RENAL T. LUMEN STIMULATED BY HCO3 - M. ACIDOSIS HCO 3 - Na + HCO 3 - H 2 CO 3 CO 2 + H 2 O HCO 3 - CELL CD H2O HCO 3 - H+H+ H2CO 3 CO 2
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BICARBONATE GENERATION IN KIDNEY STIMULATED PCO 2 (BY RESP ACIDOSIS) & - HCO3 (M. ACIDOSIS) B-B- Na+ CELL H2O HCO 3 - H+H+ H2O CO 3 B-B- HB HCO 3 -
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PATHOPHYSIOLOGIC DISTURBANCES Lungs Disturbances of CO 2 = R. Centre Disturbance of H + +HCO 3 = Metabolic
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Henderson - Hosselbalch EQUATION Proton Acceptor (Base) PH=PK+Log = -------------------------------- Proton Donor (Acid) - HCO 3 (Metabolic) PH=PK+Log = ---------------------------------- H 2 CO 3 or PCO 2 x 0.03 (Respiratory)
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ACID-BASE DISTURBANCE - HCO 3 PCO 2 x 0.03 MEATBOLICRESPIRATORY ACIDOSISALKALOSIS ACIDOSISALKALOSIS HCO 3 ---------------- PCO 2 x0.03 HCO 3 ---------------- PCO 2 x0.03 RATIO HCO 3 ---------------- PCO 2 x0.03 HCO 3 ---------------- PCO 2 x0.03
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Metabolic acidosis = Respiratory acidosis = Metabolic alkalosis = Respiratory alkalosis = Defect HCO 3 ---------- PCO 2 HCO 3 ---------- PCO 2 HCO 3 ---------- PCO 2 HCO 3 ---------- PCO 2 Correction HCO 3 ---------- PCO 2 HCO 3 ---------- PCO 2 HCO 3 ---------- PCO 2 HCO 3 ---------- PCO 2
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CAUSES OF M. ACIDOSIS 1.Glomeralar failure. 2.Keto-acidosis. 3.Lactic acidosis. 4.Intestinal loss. 5.R. Tubular failure. 6.Actazolamide therapy. 7.R. Tubular acidosis. 8.Ureteric transplantation. 9.NH 4 Cl el therapy. Hyperkalamic M. Acidosis Variable Hyppkalamic Acidosis Hyperchloraemic Acidosis
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SCREENING TESTS METABOLIC ACIDOSIS BLOOD GLUCOSE. URINE/ BLOOD KETONES. SERUM CHLORIDE. SERUM POTASSIUM
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RESPIRATORY ACIDOSIS Acute Respiratory Failure. Erythrocyte Chronic Respiratory Failure. Renal Generation.
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METABOLIC ALKALOSIS Administration of HCO 3. K+ depletion – Generation by kidney. Pyloric Stenosis.
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RESPIRATORY ALKALOSIS Hysterical Over-breathing. ICP. Brain Stem Injury. Hypoxia. Pulmonary Oedema. Lobar Pneumonia. Pulmonary Collapse. Excessive Artificial Ventilation.
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BALANCE OF ACID-BASE NORMAL VALUES PCO 2 30-50mmHg or 4-6.6kPa. >50mmHgrespiratory or 6.6kPaacidosis <30mmHgrespiratory or 4kPaalkalosis PH 7.30 – 7.50 >7.50 alkalaemia. <7.30 acidosis
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BALANCE OF ACID-BASE RELATIONSHIP PCO 2 and PH. PCO 2 & ventilation. PO 2 and normal range. PO 2 and FIO 2. PCO 2, and temperature.
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TERMINOLOGY ACIDAEMIA- PH<7.30 ALKAEMIA- PH>7.50. ACIDOSIS- Base Deficit Present. ALKALOSIS - Base Excess Present.
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HOW TO ASSESS BLOOD GASES? STEP-1 Assessment of Acid-Base Balance. STEP-2 Assessment of Hypoxaemic State. STEP-3 Assessment of Tissue Oxygenation State.
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STEP-1 Assessment of Acid-Base Balance CLASSIFICATION ACIDOSIS ALKALOSIS METABOLICRESPIRATORYMETABOLICRESPIRATORY ACUTE CHRONIC ACUTE CHRONIC ACUTE CHRONIC ACUTE CHRONIC
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STEP-1 Assessment of Acid-Base Balance Acute- Uncompensated. Chronic- Compensated. -Fully. - Partially. COMPENSATED PH 7.30-7.50 DIAGNOSIS.
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DIAGNOSIS SEQUENCE. PH. PCO 2. HCO 3. PH Normal 7.4 Compensated 7.3-7.5 PCO 3 Normal 40mmHg (5.3kPa) Compensated 30-50mmHg (4-6.6 kPa)
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DIAGNOSIS IF PH LOW – acidosis. Look at PCO 2. If PCO 3 high - respiratory acidosis If PH low - acidosis Look at PCO 2 If it is normal or low. Look at HCO3. It is low – metabolic acidosis. IF PH HIGH - alkalosis Look at PCO 2. If it is low - respiratory alkalosis If PH high - PCO 2 normal or high. Look at HCO3. High - metabolic alkalosis. NOW LOOK FOR COMPENSATION
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Classification PHPCO 2 HCO 3 K+K+ ActualStandard Metabolic Uncompensated Compensated <7.3 7.3-7.4 N 30-40 Except Respiratory Uncompensated Compensated <7.3 7.3-7.4 >50 N NN Metabolic Uncompensated Compensated >7.5 7.4-7.5 N 40-50 Respiratory Uncompensated Compensated >7.5 7.4-7.5 <30 N NN ACIDOSISACIDOSIS ALKALOSISALKALOSIS Primary change
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STEP-2 Hypoxaemic State Below 60 years of age: Normal PO 2 = 97mmHg. Acceptable range= >80mHg. Mild hypoxiaemia= <80mmHg. Moderate hypoxiaemia= <60mmHg. Severe hypoxiaemia= <40mmHg.
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STEP-2 Hypoxaemic State Above 60 years of age: Subtract 1mmHg from minimal 80mmHg for every year over 60; this means acceptable range: 60 years = >80 mmHg. 70 years = >70 mmHg. 80 years = >70 mmHg. 90 years = >50 mmHg. New Born: Acceptable = 40-70 mmHg.
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STEP-2 Hypoxaemic State Oxygen Therapy FIO 2 x 5 = Expected PO 2. Uncorrected Hypoxaemia = PO 2 <Room Air Acceptable Limit. Corrected Hypoxaemia = PO 2 > Room Air Acceptable Limit. <100mmHg. Excessively Corrected Hypoxaemia = PO 2 >100mmHg < minimal predicted.
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STEP-3 Assessment of Tissue Oxygenation 1.Cardiac Status. 2.Peripheral Perfusion Status. 3.Blood Oxygen Transport Mechanism. Depends on: Vital Signs Physical Examination.
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STEP-3 Assessment of Tissue Oxygenation BP. Pulse Pressure. Heart Rate ECG. Skin Color & Condition. Capillary Fill. Senosrium. Electrolyte Balance. Urine Out Put. If Above 1,2 Good Only 3 Interfering. Arterial Oxygen Tension Po2. Blood Oxygen Content. Hb Oxygen Affinity.
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SUMMARY ASSESS ACID/BASE STATUS. ASSESS HYPOXAEMIC STATE ASSESS TISSUE OXYGENATION. TRY TO FIND OUT THE CAUSE. SEE FOR THE NEED OF HCO 3.
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SUMMARY Acidosis Metabolic Look at 1. Blood urea If and K+ G.F. 2. Blood Glucose ket If and K+ ketoacidosis. 3. PO2 If K+ Lactic acidosis 4. Serum HCO3. If only H/o Therapy 5. If K+ think of NH4Cl therapy + G. Transplantation 6. If Cl - K + Think of actazolamide therapy and R. Tubul Acidosis. 7. If Cl - N K + Proximal Tubul Failure. OTHERWISE THINK ABOUT GIT INVOLVEMENT
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SUMMARY Lung Functions will Help Respiratory METABOLIC Look at K+ & Cl- K+ Cl- H/o vomiting Pyloric stenosis If K+ find cause. H/o bicarb therap. Alkalosis RESPIRATORY - H/o H. Injury - L. Infection - IPPV
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BASE EXCESS/ DEFICIT “mEq of HCO3 that is excess/ deficit per litre of E. C. Water” PREDICTED RESPIRATORY PH? PCO 2 -- PH RELATIONSHIP PCO 2 20mmHg = 0.1PH. PCO 2 10mmHg = 0.1PH
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BASE EXCESS/ DEFICIT 1.Calculate difference between measured PCO 2 and 40mmHg. Move decimal 2 places to left. 2.If PCO 2 > 40 subtract ½ difference from 7.4. 3.If PCO 2 < 40 add the difference to 7.40. PH 7.21 PCO 2 90 90-40 = 50 = 0.50 = 0.50x ½ = 0.25 7.40-0.25 =7.15 PH 7.47 PCO2 18 40-18 = 22= 0.22 7.40 + 0.22 =7.62 Predicted Resp PH.
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DETERMINATION OF METABOLIC COMPONENT 10mEq/L variance from buffer base PH change of c-15 units. Move decimal 2 places to right i.e. 15 ratio 15:, 2:3=2/3 Measured PH - Predicted PH (resp) - metabolic PH change.
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DETERMINATION OF METABOLIC COMPONENT 1.Determine PCO 2 variance. I.e. PCO 2 -40mmHg PCO 2. Move decimal 2 point to left. 2.Determine Predicted Resp. PH. 3.Measured PH – Predicted PH difference move decimal 2 places to rt. X 2/3=base excess/deficit. Base Excess = measured PH> predicted PH. Base Deficit = measured PH> predicted PH.
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APPROXIMATE Na + & K + CONCENTRATION IN BODY FLUID PlasmaGastricBiliaryPancraticS. Intestine Na + K + 140 4 60 10 40 5 110 5 IlealIleost0myDiarrhoeaSweat 120 5 130 15 60 40 60 10
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DOES TRADITIONAL BLOOD GAS ANALYSIS SERVES THE PURPOSE? PH PCO 2 PO 2 HCO 3
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WHAT INFORMATION DOES IT GIVE? OXYGEN UPTAK CO 2 PRODUCTION ACIDITY/ ALKALINITY
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WHAT INFORMATION IS REQUIRED FOR THERAPY? UPTAKE- O 2 uptake in lungs. TRANSPORT- from lungs to capillaries. RELEASE- from capillaries to tissues. HOW TO WE GET? DEEP PICTURE OF BLOOD GASES
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O 2 UPTAKE MOUTH TO ALVEOLI “Grahams’ Law” of diffusion
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O 2 UPTAKE Alveoli to Hb “Henrys’ Law” of diffusion
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COMBINE BOTH LAWS Mouth to Alveoli Grahams’ Law of diffusion Alveoli to Hb Henrys’ Law of diffusion.
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TRANSPORT TO CAPILLARIES DO 2 “ 520 - 720ml/min/m 2 ”
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O 2 RELEASE TO TISSUE VO 2 “ 110 - 160ml/min/m 2 ”
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WIHAT IS DEEP PICTURE? PCO 2. tHb. oS 2. O 2 Hb. ctO. p50. VO 2.
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O 2 TRANSPORT AMOUNT OF HB. FRACTION OF OXYGENATED HB. O 2 TENSION.
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MAJOR CHALLENGES Balancing O 2 Supply and O 2 Demand
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O 2 CARRYING CAPACITY 98% Bound to Hb. 2% in plasma. Forms of hemoglobins. Oxygenated – O 2 Hb. Deoxygenated – RHb. Dyshaemoglobins. Carboxyhaemoglobin (CoHb). Methaemoglobin (MetHb). tHb = cO 2 Hb + cRHb + cCoHb + cMetHb
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DEGREE TO WHICH Hb CARRIES O 2 Expressed in two Different Ways. 1. Fraction of Oxygenated Hb. cO 2 Hb O 2 Hb = ----------------------------------------------- cO 2 Hb + cRHb + cCoHb + cMetHb FRACTIONAL SATURATION 2. O2 Saturation. cO 2 Hb sO 2 = --------------------------- X 100 cO 2 Hb + cRHb
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DEGREE TO WHICH Hb CARRIES O 2 “FUNCTIONAL SATURATION” Relationship between Oxygenated Hb (O 2 Hb) and Oxygen Saturation sO 2 ) O 2 Hb = sO 2 x (1-CoHb – cMetHb)
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Example: Patient exposed to carbon monoxide tHb =10.0 mmol/L cO 2 Hb =07.7 mmol/L cRHb = 0.3 mmol/L cCoHb =2.0 mmol/L 7.7 mmol/L 0.77 cO 2 Hb = ---------------------------= ---------- (7.7+0.3+2.0) mmol/L (or 77%) 7.7 mmol/L sO 2 = -------------------------- X 100 = 96.25% (7.7+0.3) mmol/L
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OXYGEN CONTENT ctO 2 = tHb x O 2 Hb + pO 2 x DYSHAEMOGLOBINS BLOOD TRANSFUSION FIO 2
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OXYGEN RELEASE cPO 2 + tPO 2 Capillary – tissue PO 2 Hb – O 2 affinity
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Hb – OXYGEN AFFINITY 98%_____________________________ Normally the arterial blood is approximately 98% saturated with oxygen. 75%_________________ After release of oxygen to the tissue, mixed venous blood is approximately 75% saturated. A left shift of th ecurve <> A right sift of the curve Indicates impeded release of oxygen.Indicates facilitated release of O2. The Oxygen Dissociation Curve (ODC) depicts the relationship between sO2 and pO2. sO 2 (%) pO 2
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The blood oxygen mL/100ml Absorption curve Depicts the Relationship between ctO 2 and pO 2. ctO 2 20 18 16 14 12 10 8 6 4 2 0 987654321987654321 2 4 6 8 1012 20 40 60 80 mmHg pO 2 kPa ctO 2 /(mmol/L a v PO 2
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DEEP PICTURE CONTAINS INFORMATION on OXYGEN UPTAKE TRANSPORT RELEASE
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Deep Picture Contains Information OXYGEN UPTAKE PaO 2 = 9.2 – 15.5 Kpa Q S Q T = 2-6% (PAO 2 – PaO 2 ) = 5 - 15mmHg Optimise Ventilation Optimise Specific Lung Disease Specific Lung Disease
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Deep Picture Contains Information RELEASE PO 2 Gradient O 2 Dissociation Curve - Optimise Ventilation - Optimise Factors
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Deep Picture Contains Information TRANSPORT tHb= 11.7–14.6G/dl-F = 13/8–16.4 G/dl-M O 2 Hb = 0.94 – 098 PO 2. CTO 2. Blood transfusion RBC production Optimise Ventilation Dyshaemoglobins
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