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IHG 05 Base Excess and Critical Care in the past and in the future Ivar Hejde Gøthgen M.D., D.M.Sc.

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Presentation on theme: "IHG 05 Base Excess and Critical Care in the past and in the future Ivar Hejde Gøthgen M.D., D.M.Sc."— Presentation transcript:

1 IHG 05 Base Excess and Critical Care in the past and in the future Ivar Hejde Gøthgen M.D., D.M.Sc.

2 IHG 05 Content Acid-base basic Scientist in the acid-base story Instruments in the acid-base story The future and Base excess

3 IHG 05 Acid Base (concept of neutrality) _______________________________________________________________________ pN = [H + ] = [OH - ] (=neutrality) pH = 6.80 [H + ] = [OH - ] = 160 nmol/l = neutrality at 37 o C pH = 7.40 [H + ] = 40 nmol/l [OH - ] = 640 nmol/l = Alkaline offset of 0.6 pH unit

4 IHG 05 pH = 6.8 Extracellular fluid pH = 7.40 Blood and extracellular fluid serve as sink for metabolic produced acids H+H+ Acid Base (the simple model) _______________________________________________________________________

5 IHG 05 Acid Base (the acid production) _______________________________________________________________________ Fixed Acids production [H + ] : 60 mmol/24 hour => 700 nmol/sec Volatile Acids production [H + ] : 13 mol/24 hour => 150000 nmol/sec > 200 times the fixed acids Total extracellular free [H + ] : 40 nmol/l * 15 l => 600 nmol

6 IHG 05 Buffer Base50 mmol/l Buffer base = H + acceptors _____________________________ Red cell Hemoglobin35% Red cell Bicarbonate18% Plasma Bicarbonate35% Plasma Proteins 7% Others (Phosphate ect.) 5% Acid Base (the Metabolic component I ) _______________________________________________________________________

7 IHG 05 BASE EXCESS and the Acid-Base nomogram Base excess was introduced by Ole Siggaard­Andersen for almost 50 years ago. While pH and pCO2 are directly measured, the metabolic component, defined as Base excess, is calculated from pH and pCO2 using the Henderson-Hasselbalch equation and the Van Slyke equation. By using base excess the acid base status is made simple and clinical useful. Acid Base (the Metabolic component II) _______________________________________________________________________

8 IHG 05 Can you go to a Pharmacy and buy a bottle of Base excess ? Acid Base (the Metabolic component III) _______________________________________________________________________ BA S E EXCESS

9 IHG 05 The Van Slyke equation (= The equation for the CO2 equilibration curve of blood in vitro) a-24.4 = -(2.3*b+7.7)*(c-7.40)+d/(1-0.023*b) where: a = bicarbonate concentration in plasma (mmol/l) b = hemoglobin concentration in blood (mmol/l) c = pH of plasma at 37 oC d = base excess concentration in blood (mmol/l) Acid Base (the Metabolic component IV) _______________________________________________________________________ (Scand J Clin lab Invest 1977:37,Suppl 146:15-20)

10 IHG 05 pH: as a measure of the activity of free hydrogen ions. pCO 2 : as a measure of the respiratory component, the activity of free CO2 in the blood. Base Excess: as a measure of the metabolic component, (the concentration of titratable hydrogen ion in the extracellular fluid). Acid Base (the acid-base status) _______________________________________________________________________

11 IHG 05 Acid Base (the acid-base status)

12 IHG 05 Respiratory changes along The bufferlines Acid Base (the acid-base status)

13 IHG 05 Metabolic changes across The bufferlines Acid Base (the acid-base status)

14 IHG 05 Bicarbonate

15 IHG 05 Content Acid-base basic Scientist in the acid-base story Instruments in the acid-base story The future and Base excess

16 IHG 05 S.P.L. Sørensen1868-1939 L.J. Henderson1878-1942 K.A. Hasselbalch1874-1962 Donald D van Slyke1883-1971 Poul Astrup1915-2000 John W. Severinghaus1922- Ole Siggaard-Andersen1932- Scientist in the acid-base story

17 IHG 05 Søren P. L. Sørensen 1868-1939 Protein Chemist at the Carlsberg brewery. To save having to write that H + = 0.000000040M, he devised the scale of acid in terms of pH, as the negative log of H + ion activity. (1907) Scientist in the acid-base story

18 IHG 05 Scientist in the acid-base story

19 IHG 05 Lawrence J Henderson Prof Biochemistry and Physiology. Theory of buffering and of bicarbonate-hydrogen ion-pCO 2 relationship. The Henderson equation K = [H + ][HCO 3 - ]/[H 2 CO 3 ] K is the dissociation constant of carbonic acid, about 10 -3 M A constant 0.1% of dissolved CO 2 in water is hydrated to carbonic acid. Therefore it can be simplified to H 2 CO 3 = dissolved CO 2 Where K is the apparent dissociation constant K = 10 -6.1 Scientist in the acid-base story

20 IHG 05 Scientist in the acid-base story

21 IHG 05 Karl A Hasselbalch 1874-1962 Agricultural chemist, Denmark. Adapted Hendersons equation to Sørensens logarithmic pH by replacing H 2 CO 3 with S. pCO 2 creating the Henderson-Hasselbalch equation : pH=pK + log [ HCO 3 - / ( S. pCO 2 ) ] 7.40 = 6.10 + log[24/{0.31. 40}] Where S (solubility) = 0.031 mM/liter/mmHg at 37 o C Scientist in the acid-base story

22 IHG 05 Scientist in the acid-base story

23 IHG 05 Donald D Van Slyke 1883-1971 Major developer of clinical chemistry in the 1910-50 period. His manometric blood gas apparatus (1924) was used to measure the content in blood of oxygen, carbon dioxide and many other variables. Laboratories calculated pCO 2 using the Henderson-Hasselbalch equation after measuring pH of blood and the total plasma CO 2 by the Van Slyke apparatus until the polio epidemics resulted in two new methods: Astrups equilibration scheme and Severinghaus modification of the Stow CO 2 electrode. Scientist in the acid-base story

24 IHG 05 Scientist in the acid-base story

25 IHG 05 Poul Astrup 1915-2000 Prof of Clinical Chemistry Univ. of Copenhagen New method for pCO 2 To avoid need for the VanSlyke and Henderson- Hasselbalch method, he devised a method for graphically calculating pCO 2 by measuring pH before and again after equilibration of the blood to a known pCO 2 Scientist in the acid-base story

26 IHG 05 Scientist in the acid-base story

27 IHG 05 John W Severinghaus 1922 Prof of Anestesia University of California San Francisco Major developer of blood gas measurents since 1950. His modification (invention) of the CO2 electrode, the first blood gas apparatus (1958), the blood gas ruler, transcutaneous blood gas measurement and pulsoximetry, as well as important work in high altitude respiratory physiology Scientist in the acid-base story

28 IHG 05 Scientist in the acid-base story

29 IHG 05 Ole Siggaard Andersen 1932 Prof of Clinical Chemistry Univ. of Copenhagen A student of Astrup, he devised the micro-method and the concept of base excess and ECF base excess, now called SBE, for standard base excess. His equation for SBE is now used in most blood gas apparatus. Photo 1999 by JWS Scientist in the acid-base story

30 IHG 05 Scientist in the acid-base story

31 IHG 05 Content Acid-base basic Scientist in the acid-base story Instruments in the acid-base story The future and Base excess

32 IHG 05 First Astrup pH apparatus for equilibration of blood sample with known Pco 2, then repeated pH measurement 1953 Instruments in the acid-base story

33 IHG 05 Micro-Astrup pH and reference electrodes, 1957 Radiometer Co, Copenhagen, Denmark The widely used Astrup equilibration method for estimating blood pCO 2 by pH measurement before and after equilibration with gas of known pCO 2. The glass pH capillary is A, filled by suction from G, and then connected to reference electrode K in saturated KCl I. Instruments in the acid-base story

34 IHG 05 First blood gas apparatus. Severinghaus and Bradley (1958) O 2 electrode consumed so much oxygen it needed stirring and calibration with equilibrated blood. CO 2 electrode O 2 electrode stirrer tonometer Instruments in the acid-base story

35 IHG 05 Instruments in the acid-base story ABL-1

36 IHG 05 Instruments in the acid-base story BMS-2, OSM-3 and ABL-4 ( incl. Ole Siggaard-Andersen at work)

37 IHG 05 Instruments in the acid-base story ABL-700

38 IHG 05 Polio victim in Copenhagen epidemic being ventilated manually by medical student through tracheostomy, 1952. Critical care treatment and the acid-base story Invasive ventilation

39 IHG 05 Critical care treatment and the acid-base story Non-invasive ventilation in Critical Care around 1955

40 IHG 05 Critical care treatment and the acid-base story To put a patient into a ventilator

41 IHG 05 Critical care treatment and the acid-base story Invasive ventilation in Critical Care in 2003

42 IHG 05 Content Acid-base basic Scientist in the acid-base story Instruments in the acid-base story The future and Base excess

43 IHG 05 Acid-Base status and Normal Saline versus Lactated Ringers solution ? The future and Base excess

44 IHG 05 The future and Base excess

45 IHG 05 The future and Base excess

46 IHG 05 The future and Base excess

47 IHG 05 How to interpret the difference in Acid Base Status after Infusion of Normal Saline and Lactated Ringers Solution: - Dilutional Acidosis versus HyperChloremic Acidosis - Brønsteds definition versus Arrhenius definition - Buffer Base (BB) versus Strong Ion Difference (SID) When adding Lactate and Chloride measument, the interpretation of acid base status may be simple and illustrates that - Buffer base equals SID as well as - Changes in Buffer Base equals Base Excess The future and Base excess

48 IHG 05 Electrolyte balance of arterial plasma showing columns of cations and anions of equal height (law of electro-neutrality). The equality of the strong ion difference (SID) and buffer base (BB) is illustrated. The change in concentration of buffer base from normal (at pH = 7.40, pCO2 = 5.3 kPa, and T = 37 C) with opposite sign equals the concentration of titratable hydrogen ion. The future and Base excess (O. Siggaard-Andersen in Encylopedia of Respiratory Medicine 2006)

49 IHG 05 The future and Base excess Base Excess is a virtual parameter, making some very complex matter simple and clinical useful Base Excess may continue to exist as the metabolic parameter in Acid-Base status

50 IHG 05 Thanks to John W Severinghaus for his kind advice and help Reykjavik june 2005 Thanks to Ole Siggaard-Andersen for his kind advice and help Gilleleje 2003

51 IHG 05 Advice from your brain and body: Use me or loose me


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