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Electrolytes, Fluids, Acid Base Balance and Shock Gwynne Jones Critical Care.

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1 Electrolytes, Fluids, Acid Base Balance and Shock Gwynne Jones Critical Care

2 Electrolytes, Fluids, Acid Base Balance and Shock Correct Fluid Management faqcilitatescrucial Homeostasis. This permits: – –Optimum Cardio-vascular perfusion – –Optimum Organ Function – –Optimum Cellular Function

3 Electrolytes, Fluids, Acid Base Balance and Shock Knowledge of the Compartmentalisation of Body Fluids forms the basis for: – –Understanding the Pathological Shifts in these Fluid Spaces in Varying Disease States – –Quantifying Deficiencies or Excesses in these Spaces – –Informs Choice of Fluid Type and Quantity

4 Electrolytes, Fluids, Acid Base Balance and Shock Knowledge of the Compartmentalisation of Body Fluids forms the basis for: – –Understanding the Effects of Sodium Concentration on Interstitial and Cellular Volume and Function – –Understanding Acid-Base Homeostasis – –Understanding specific Patient Needs in Renal Failure, Brain Disease, Liver, Heart and Lung Diseases.

5 Electrolytes, Fluids, Acid Base Balance and Shock Body Fluid Compartments: – –Water Contributes 50-70% of Body Weight. – –Fat has Little Water, thus Lean People have greater Body Water as % weight – –Water is distributed EVENLY throughout all body compartments but will follow Osmotic Gradients

6 Electrolytes, Fluids, Acid Base Balance and Shock Body Fluid Compartments: – –Total Cations Must Equal Total Cations – –Sodium is Predominently Extracellular and determines Extracellular Fluid Volume. – –Cell Volume is Controlled mainly by Cell Membrane Ion Pumps

7 Electrolytes, Fluids, Acid Base Balance and Shock Electrolyte Concentration is usually expressed in terms of chemical combining activity, or equivalents. Equivalent = Atomic Wt (g)/valence

8 Electrolytes, Fluids, Acid Base Balance and Shock Body Fluid Compartments: – –Total Cations Must Equal Total Cations – –The Physiological Activity of Electrolytes in Solution depends on the Number of Particles per Unit Volume (milli-mols/Liter, mMol/L – –The Number of Electric Charges per Unit Volume (milli-equivalents per Liter, mEq/L – –The Number of Osmotically Active Ions per unit Volume (milli-osmoles per Liter, mOsm/L)

9 Electrolytes, Fluids, Acid Base Balance and Shock Body Fluid Compartments: – –Total Cations Must Equal Total Cations – –Sodium is predominently Extracellular and determines Extracellular Fluid Volume. – –Cell Volume is Controlled mainly by Cell Membrane Ion Pumps

10 Electrolytes, Fluids and Shock

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13 Two Thirds of the body Water is in the cells.Two Thirds of the body Water is in the cells. This is between 30L to 40 L.This is between 30L to 40 L. Is has an Electrolyte composition very different from the Extra-cellular water.Is has an Electrolyte composition very different from the Extra-cellular water. What is this difference?What is this difference?

14 Electrolytes, Fluids and Shock Two Thirds of the body Water is in the cells.Two Thirds of the body Water is in the cells. Electrolyte composition:Electrolyte composition: Cations:Cations: –Potassium: 150 mMol/L –Sodium: 10 mMol/L –Magnesium: 40 mMol/L. –Calcium and Hydrogen: nanoMols/L Anions:Anions: –Phosphate and Sulphate ± 150 mMol/L. –Proteinate ± 40 mMol/L –Bicarbonate ± 10 mMol/L

15 Electrolytes, Fluids and Shock Two Thirds of the body Water is in the cells.Two Thirds of the body Water is in the cells. This is between 30L to 40 L.This is between 30L to 40 L. Is has an Electrolyte composition very different from the Extra-cellular water.Is has an Electrolyte composition very different from the Extra-cellular water. How is it maintained?How is it maintained?

16 Electrolytes, Fluids and Shock Two Thirds of the body Water is in the cells.Two Thirds of the body Water is in the cells. Electrolyte composition:Electrolyte composition: Cations:Cations: –Potassium: 150 mMol/L –Sodium: 10 mMol/L –Magnesium: 40 mMol/L. –Calcium and Hydrogen: nanoMols/L Anions:Anions: –Phosphate and Sulphate ± 150 mMol/L. –Proteinate ± 40 mMol/L –Bicarbonate ± 10 mMol/L These differences are maintained by various cell membrane ion pumps. Na/K ATPase driven exchangers are most important

17 Electrolytes, Fluids and Shock Two Thirds of the body Water is in the cells.Two Thirds of the body Water is in the cells. Electrolyte composition:Electrolyte composition: Cations:Cations: –Potassium: 150 mMol/L –Sodium: 10 mMol/L –Magnesium: 40 mMol/L. –Calcium and Hydrogen: nanoMols/L Anions:Anions: –Phosphate and Sulphate ± 150 mMol/L. –Proteinate ± 40 mMol/L –Bicarbonate ± 10 mMol/L These differences are maintained by various ion pumps. Na/K ATPase driven exchangers are most important After Severe Shock 20% of Oxygen/fuel consumption is used just to pump the Sodium out of the cells.

18 Electrolytes, Fluids and Shock Two Thirds of the body Water is in the cells.Two Thirds of the body Water is in the cells. Electrolyte composition:Electrolyte composition: Cations:Cations: –Potassium: 150 mMol/L –Sodium: 10 mMol/L –Magnesium: 40 mMol/L. –Calcium and Hydrogen: nanoMols/L Anions:Anions: –Phosphate and Sulphate ± 150 mMol/L. –Proteinate ± 40 mMol/L –Bicarbonate ± 10 mMol/L These differences are maintained by various ion pumps. Na/K ATPase driven exchangers are most important. Cell volume fluctuates a little in shock and has some influence on resuscitation fluid choice. In the presence of shock (the ebb phase) they swell. In more chronic severe illness (after shock/flow phase) they shrink.

19 Electrolytes, Fluids and Shock Two Thirds of the body Water is in the cells.Two Thirds of the body Water is in the cells. Electrolyte composition:Electrolyte composition: Cations:Cations: –Potassium: 150 mMol/L –Sodium: 10 mMol/L –Magnesium: 40 mMol/L. –Calcium and Hydrogen: nanoMols/L Anions:Anions: –Phosphate and Sulphate ± 150 mMol/L. –Proteinate ± 40 mMol/L –Bicarbonate ± 10 mMol/L These differences are maintained by various ion pumps. Na/K ATPase driven exchangers are most important. Cell volume fluctuates a little in shock and has some influence on resuscitation fluid choice. 1. Smaller cells switch off protein production and thus contribute to nitrogen loss.

20 Electrolytes, Fluids and Shock Two Thirds of the body Water is in the cells.Two Thirds of the body Water is in the cells. Electrolyte composition:Electrolyte composition: Cations:Cations: –Potassium: 150 mMol/L –Sodium: 10 mMol/L –Magnesium: 40 mMol/L. –Calcium and Hydrogen: nanoMols/L Anions:Anions: –Phosphate and Sulphate ± 150 mMol/L. –Proteinate ± 40 mMol/L –Bicarbonate ± 10 mMol/L These differences are maintained by various ion pumps. Na/K ATPase driven exchangers are most important. Cell volume fluctuates a little in shock. Cells are smaller in recovering shock. 2. Insulin and certain Amino Acids stimulate protein synthesis. The re-feeding syndrome is associated with this. How?

21 Electrolytes, Fluids and Shock Two Thirds of the body Water is in the cells.Two Thirds of the body Water is in the cells. Electrolyte composition:Electrolyte composition: Cations:Cations: –Potassium: 150 mMol/L –Sodium: 10 mMol/L –Magnesium: 40 mMol/L. –Calcium and Hydrogen: nanoMols/L Anions:Anions: –Phosphate and Sulphate ± 150 mMol/L. –Proteinate ± 40 mMol/L –Bicardonate ± 10 mMol/L The cell is thus a rich sauce. It is the lean body mass that we survive on. For the rest of the talk/life we leave them in the background. We forget them at our peril.

22 Electrolytes, Fluids and Shock

23 The extracellular space is ± one third of the total Body Water. Blood plasma is a quarter of this (± 5L in an adult). Interstitial fluid is the other three quarters (± 15L in an adult) How is this difference maintained when the endothelium is fully permeable to salt water?

24 Electrolytes, Fluids and Shock There is a subtle difference between blood/plasma and interstitial fluid. This is mainly the difference in protein. As Albumin is a small protein (MW66,000kD), it has the greatest number of osmotically active molecules. These are able to exert an osmotic activity across a semi-permeable membranes.

25 Electrolytes, Fluids and Shock There is a subtle difference between blood/plasma and interstitial fluid. Sodium passively determines the extracellular space volume. Why?

26 Electrolytes, Fluids and Shock Sodium passively determines the extracellular space volume. Total body sodium is around 3000mMol. (±20L X 140mMol/L). Anyone with edema has a high body sodium (and the water it craves). This, unfortunately, does not mean that the Blood/Plasma volume is low/normal/high!

27 Electrolytes, Fluids and Shock Whose Law determines the mechanism by which these intravascular /interstitial volumes are maintained?

28 Electrolytes, Fluids and Shock Whose Law determines the mechanism by which this intravascular /interstitial process is maintained? Starling’s Law. Jv = Ks (Ppl - Pis) - σ (πpl - πis)

29 Electrolytes, Fluids and Shock Jv = Ks (Ppl - Pis) - σ (πpl - πis)

30 Electrolytes, Fluids and Shock Jv = Ks (Ppl - Pis) - σ (πpl - πis)

31 Electrolytes, Fluids, Acid Base Balance and Shock – –What is σ and why is it important?

32 Electrolytes, Fluids, Acid Base Balance and Shock – –What is σ and why is it important? – –σ is the Protein Reflection Co-efficient – –σ is 0.3 in skin (ie very tight endothelium) – –σ is 0.6 in the lung and Kidney – –σ is 0.9 in the Gut and Liver (ie very Leaky for Protein)

33 Electrolytes, Fluids and Shock Jv = Ks (Ppl - Pis) - σ (πpl - πis)

34 Electrolytes, Fluids and Shock Jv = Ks (Ppl - Pis) - σ (πpl - πis)

35 Electrolytes, Fluids and Shock Jv = Ks (Ppl - Pis) - σ (πpl - πis) The endothelium is more complex than initially imagined. The endothelium is covered by a glyco-calyx. These two barriers: the Endothelium and the Glycocalyx are co-operative. Damage to either one is not associated with an increase in fluid flux. Damage to both is associated with severe leaky vessels (capillaries)

36 Electrolytes, Fluids and Shock Jv = Ks (Ppl - Pis) - σ (πpl - πis) The endothelium is more complex than initially imagined. The endothelium is covered by a glyco-calyx. These two barriers are co- operative: The endothelium is damaged particularly by Reactive Oxygen Species (ROS) The glyco-calyx is damaged particularly by proteases.

37 Electrolytes, Fluids and Shock Jv = Ks (Ppl - Pis) - σ (πpl - πis) The endothelium is more complex than initially imagined. The endothelium is covered by a glyco- calyx. These two barriers are co-operative. They allow a flow of interstitial fluid enriched by sugar and electrolytes. The ¼ Blood/Plasma: ¾ interstitial fluid ratio in health is maintained. Excess is taken up by lymphatics and returned to the blood via the thoracic duct.

38 Electrolytes, Fluids and Shock Blood Volume is ± 5L in the adult. 45% is RBCs The rest is an aqueous solution of electrolytes and proteins. The proteins are functional: Immunoglobulins Coagulation factors ComplementAlbuminHormonesEtc.

39 Electrolytes, Fluids and Shock Blood Volume is ± 5L in the adult. Blood Volume is highly regulated by: What?

40 Electrolytes, Fluids and Shock Blood Volume is ± 5L in the adult. Blood Volume is highly regulated by: Pressure Sensors. Volume Sensors. Osmo-receptors.

41 Electrolytes, Fluids and Shock Blood Volume is ± 5L in the adult. Blood Volume is highly regulated by: Pressure Sensors: Carotid Sinus, Renal Vessels. Volume Sensors: Large Veins/Atria. Osmo-receptors: Hypothalamus.

42 Electrolytes, Fluids and Shock Blood Volume is ± 5L in the adult. Blood Volume is highly regulated by: Pressure Sensors: Carotid Sinus, Renal Vessels. Volume Sensors: Large Vein/Atria. Osmo-receptors: Hypothalamus. These act via the Autonomic Nervous system, the hypothalamic-Pituitary Axis and adrenal glands to stimulate thirst, Sodium and Water Retention, Vaso-constriction etc.

43 Electrolytes, Fluids and Shock Blood Volume is ± 5L in the adult. Blood Volume is highly regulated by: Pressure Sensors: Carotid Sinus, Renal Vessels. Volume Sensors: Large Vein/Atria. Osmo-receptors: Hypothalamus. These act via the Autonomic Nervous system, the hypothalamic-Pituitary Axis and adrenal glands to stimulate thirst, Water Retention, Vaso-constriction etc. Tell me about the hormones!

44 Electrolytes, Fluids and Shock ADHCATECHOLAMINESANGIOTENSINCORTISOLALDOSTERONE ATRIAL NATRIURETIC HORMONE ENDOTHELIN

45 Electrolytes, Fluids and Shock This is going to get Harder!

46 Electrolytes, Fluids and Shock Acid-Base Balance. Hydrogen is in Nano-Molar quantities

47 Electrolytes, Fluids and Shock Hydrogen is in Nano-Molar quantities. It all has to do with the dissociation of water. Most of the water is not dissociated (55mMol/L.) nMol/L of water is dissociated into H + and OH - If all is H + the pH is zero. If all is OH - the pH is 14. The pH scale is zero to 14, neutral is a pH of 7 Acid-Base Balance.

48 Electrolytes, Fluids and Shock Acid-Base Balance. Hydrogen is in Nano-Molar quantities. It all has to do with the dissociation of water. Most of the water is not dissociated nMol/L is dissociated into H + and OH - If all is H + the pH is zero. If all is OH - the pH is 14. The pH scale is zero to 14, neutral is a pH of 7 There are three independent variables that affect pH or H ion concentration: The bicarbonate/carbon dioxide system The dissociation of proteins The Strong Ion difference (SID

49 Electrolytes, Fluids and Shock Acid-Base Balance. Hydrogen is in Nano-Molar quantities. It all has to do with the dissociation of water. Most of the water is not dissociated nMol/L is dissociated into H + and OH - If all is H + the pH is zero. If all is OH - the pH is 14. The pH scale is zero to 14, neutral is a pH of 7 The Strong Ion difference (SID). This is the difference between fully dissociated anions and cations. Na + K – Cl + La - = ± 40 in health. This is the bath in which your bicarbonate and proteinate buffers work.

50 Electrolytes, Fluids and Shock The Bicarbonate SystemThe Bicarbonate System [CO 2 ] [H 2 O][H + ] [HCO 3 ]

51 Electrolytes, Fluids and Shock HCO 3 pCO for 10 acutely. How long does it take?

52 Pulmonary Ventilation and Gas Exchange HCO 3 pCO for 10 chronically. How long does it take?

53 Electrolytes, Fluids and Shock A 47 yr old man develops has evident bowel obstruction on the background of severe Crohn’s disease.A 47 yr old man develops has evident bowel obstruction on the background of severe Crohn’s disease. His Blood work shows:His Blood work shows: –`Hb 90G/L WBC 18,000 His Na+ is 150, Cl-110, K+ 3.2, HCO Creatinine 320 pH 7.2, pCO 2 30, HCO 3, 10 pO 2 90 on nasal oxygen, Lactate 5pH 7.2, pCO 2 30, HCO 3, 10 pO 2 90 on nasal oxygen, Lactate 5 Mr. S. P: SBO with Shock How are you going to resuscitate him?

54 Electrolytes, Fluids and Shock pCO 2 =K VCO 2 ________ Alv. Vent. pCO 2 Won’t or Can’t Breath Alveolar Hyperventilation

55 Energy Metabolism in Critically Ill GLYCOLYSIS Why does bicarbonate fall, on roughly a mol for mol basis, when lactic acidosis occurs? H + HCO 3 H 2 CO 3 CO 2 H 2 O

56 Energy Metabolism in Critically Ill GLYCOLYSIS Why does bicarbonate fall, on roughly a mol for mol basis, when lactic acidosis occurs? HLactate + NaHCO 3 NaLactate + H 2 CO 3 H + HCO 3 H 2 CO 3 CO 2 H 2 O

57 Electrolytes, Fluids and Shock What are the determinants of Cardiac Output?

58 Electrolytes, Fluids and Shock Cardiac Output is determined by four variables: PreloadAfterloadContractility Heart Rate

59 Electrolytes, Fluids and Shock Cardiac Output is determined by four variables: 1. Preload: This is the force or load that stretches the cardiac muscle prior to contraction.

60 Electrolytes, Fluids and Shock Cardiac Output is determined by four variables. Afterload: This is the impedence to outflow of the ventricle. This includes the size of the ventricle (La Place), The SVR, PVR, compliance of large vessels and the pleural pressure

61 Electrolytes, Fluids and Shock Cardiac Output must equal Venous return. Venous return is determined by five variables: Stressed Vascular Volume Venous Compliance Venous Resistance Distribution of Blood Flow Right Atrial Pressure

62 Electrolytes, Fluids and Shock: Venous Return This is hard but worth thinking about!

63 Electrolytes, Fluids and Shock ARTERIOLE VENULE X X Pressure ± 35 mmHg Pressure ± 7 mmHg What is the proportion of blood in the arterial side of the circulation compared to the Venous side?

64 Electrolytes, Fluids and Shock ARTERIOLE VENULE X X Pressure ± 35 mmHg Pressure ± 7 mmHg What is the proportion of blood in the arterial side of the circulation compared to the Venous side: ± 70%.Why?

65 Electrolytes, Fluids and Shock The Veins are very compliant.The Veins are very compliant. The arteries are not.The arteries are not. The Venous Anatomy and Venous Return

66 Electrolytes, Fluids and Shock The Veins are very compliant.The Veins are very compliant. The elastic recoil of the compliant capacity vessels is a potential energy (filled by the arterial pressure).The elastic recoil of the compliant capacity vessels is a potential energy (filled by the arterial pressure). This potential energy of elastic recoil acts to transfer blood towards the heart maintaining cardiac filling and output.This potential energy of elastic recoil acts to transfer blood towards the heart maintaining cardiac filling and output. The Venous Anatomy and Venous Return

67 Electrolytes, Fluids and Shock The Veins are very compliant.The Veins are very compliant. The elastic veins have an elasticity that allows them to act like an auxiliary pumpThe elastic veins have an elasticity that allows them to act like an auxiliary pump The Venous Anatomy and Venous Return

68 Electrolytes, Fluids and Shock There is a progressive drop in pressure within the systemic circuit from the highest value, at the outlet of the left ventricle to the lowest value, at the right atrium.There is a progressive drop in pressure within the systemic circuit from the highest value, at the outlet of the left ventricle to the lowest value, at the right atrium. What would happen to these pressures if it were possible to switch off the heart, without reflex change, for 30 seconds?What would happen to these pressures if it were possible to switch off the heart, without reflex change, for 30 seconds? The Venous Anatomy and Venous Return

69 Electrolytes, Fluids and Shock What would happen to these pressures if it were possible to switch off the heart, without reflex change, for 30 seconds?What would happen to these pressures if it were possible to switch off the heart, without reflex change, for 30 seconds? Without flow, the pressure throughout the system would equalise to a level determined by the compliance of the whole system.Without flow, the pressure throughout the system would equalise to a level determined by the compliance of the whole system. As the venous system is hugely compliant, the pressure would equalise at a pressure just above the RA pressure.As the venous system is hugely compliant, the pressure would equalise at a pressure just above the RA pressure. This is The Mean Systemic Pressure.This is The Mean Systemic Pressure. The Venous Anatomy and Venous Return

70 Electrolytes, Fluids and Shock ARTERIOLE VENULE X X The Venous Anatomy and Venous Return X X Pressure ± 35 mmHg Pressure ± 7 mmHg This is the mean systemic pressure

71 Electrolytes, Fluids and Shock Without flow, the pressure throughout the system would equalise at all points to a level determined by the compliance of the whole system.Without flow, the pressure throughout the system would equalise at all points to a level determined by the compliance of the whole system. This is The Mean Systemic Pressure.This is The Mean Systemic Pressure. It is the pressure in the small veins which distends the capacitance vessels, thereby producing a potential energy for flow to return to the RA.It is the pressure in the small veins which distends the capacitance vessels, thereby producing a potential energy for flow to return to the RA. The RA pressure is constantly emptied by the RVThe RA pressure is constantly emptied by the RV The Venous Anatomy and Venous Return

72 Electrolytes, Fluids and Shock As the venous system is hugely compliant, the pressure would equalise at a pressure just above the RA pressure. The Mean Systemic Pressure.As the venous system is hugely compliant, the pressure would equalise at a pressure just above the RA pressure. The Mean Systemic Pressure. The Mean Systemic Pressure is the driving pressure for venous return.The Mean Systemic Pressure is the driving pressure for venous return. It is 5 to 10 mmHg. in the normal circulation.It is 5 to 10 mmHg. in the normal circulation. As RA pressure is less, only - 4 to + 4 mmHg., venous return is fine.As RA pressure is less, only - 4 to + 4 mmHg., venous return is fine. The Mean Systemic Pressure.

73 Electrolytes, Fluids and Shock As the venous system is hugely compliant, the pressure would equalise at a pressure just above the RA pressure. The Mean Systemic Pressure.As the venous system is hugely compliant, the pressure would equalise at a pressure just above the RA pressure. The Mean Systemic Pressure. The Mean Systemic Pressure is the driving pressure for venous return.The Mean Systemic Pressure is the driving pressure for venous return. It is 5 to 10 mmHg. in the normal circulation.It is 5 to 10 mmHg. in the normal circulation. As RA pressure is less, only - 4 to + 4 mmHg., venous return is fine.As RA pressure is less, only - 4 to + 4 mmHg., venous return is fine. The Mean Systemic Pressure. The Job of the Right Ventricle is to keep the Right Atrium empty. It does the job amazingly well as long as the RV afterload is low (ie the lungs are OK).

74 Electrolytes, Fluids and Shock The Mean Systemic Pressure. Imagine the pressure change as you fill a collapsed bag. Until filled, there will be no pressure change The bag is very compliant. It has a large unstressed volume This is how the veins are with a blood volume of 4L.

75 Electrolytes, Fluids and Shock Now the bag has filled, the pressure will increase in proportion to the compliance of the wall of the bag, together with the rate at which fluid is entering the bag.Now the bag has filled, the pressure will increase in proportion to the compliance of the wall of the bag, together with the rate at which fluid is entering the bag. You have reached the bag’s stressed volume.You have reached the bag’s stressed volume. The Mean Systemic Pressure. This is how the veins are with a blood volume of 5L.

76 Electrolytes, Fluids and Shock The Mean Systemic Pressure. Imagine the pressure change as you fill a collapsed bag. Until filled, there will be no pressure change The bag is very compliant. It has a large unstressed volume This is how the veins are with a blood volume of 4L.

77 Electrolytes, Fluids and Shock The Mean Systemic Pressure. Imagine the pressure change as you fill a collapsed bag. Until filled, there will be no pressure change The bag is very compliant. It has a large unstressed volume Fluid Resuscitation would be Good. Which Fluid would you Choose?

78 Electrolytes, Fluids and Shock Venous Return and Cardiac Function Venous Return RA Pressure Venous return will be zero when RA pressure equals mean systemic pressure Mean Systemic Pressure

79 Are We Treating The Right Ventricle? Venous Return and Cardiac Function RA Pressure Cardiac output Venous Return or Venous return can be increased in three ways 1. Reduce Atrial Pressure 2. Increase PMS

80 Electrolytes, Fluids and Shock The Mean Systemic Pressure (PMS). Systemic Vascular volume Mean systemic pressure INFUSED VOLUME INCREASED PMS REDUCTION IN UNSTRESSED VOLUME INCREASED PMS DECREASE IN COMPLIANCE INCREASED PMS

81 Electrolytes, Fluids and Shock The systolic and diastolic dysfunction after acute MI produces LV failure.The systolic and diastolic dysfunction after acute MI produces LV failure. Pre-load recruitable stroke work (move up the Frank-Starling Curve) increases LV end-diastolic pressure.Pre-load recruitable stroke work (move up the Frank-Starling Curve) increases LV end-diastolic pressure. LV end-diastolic pressure (the wedge/PAOP) was measured at 28mm Hg.LV end-diastolic pressure (the wedge/PAOP) was measured at 28mm Hg. This high wedge/PAOP induces pulmonary hypertension, thereby increasing RV afterload.This high wedge/PAOP induces pulmonary hypertension, thereby increasing RV afterload. The RV is failing also, as indicated by the high right atrial pressure.The RV is failing also, as indicated by the high right atrial pressure. Sympathetic activation at low levels mostly produces a decrease in venous capacity.Sympathetic activation at low levels mostly produces a decrease in venous capacity. This produces the equivalent of a blood transfusion.This produces the equivalent of a blood transfusion. This volume load increases venous return and right ventricular dilation.This volume load increases venous return and right ventricular dilation. RV volume increase may increase RV ejection fraction, although the high RV afterload may not permit this increase, The RV being excellent at increasing output if impedence is low but poor when impedence to outflow is high, as in pulmonary hypertension.RV volume increase may increase RV ejection fraction, although the high RV afterload may not permit this increase, The RV being excellent at increasing output if impedence is low but poor when impedence to outflow is high, as in pulmonary hypertension.

82 Electrolytes, Fluids and Shock Sympathetic Nervous System Output Systemic Vascular Resistance Venous Capacity SVR VC Effect of Sympathetic activation on preload and afterload

83 Electrolytes, Fluids and Shock The Venous Innervation Artery Sympathetic Nerve α1α1α1α1α1α1α1α1α1α1α1α1 α2α2α2α2α2α2α2α2 α2α2α2α2α2α2α2α2 α2α2α2α2α2α2α2α2 Vein α1α1α1α1α1α1α1α1α1α1α1α1 α1α1α1α1α1α1α1α1α1α1α1α1 α1α1α1α1α1α1α1α1α1α1α1α1 α2α2α2α2α2α2α2α2 α2α2α2α2α2α2α2α2 α2α2α2α2α2α2α2α2

84 Electrolytes, Fluids and Shock The Venous Innervation Artery Sympathetic Nerve α1 or α2 Vein or Adenyl Cyclase Cyclic AMP Protein Kinase G Phosphodiesterase 3 Multiple Kinases iCa ++ Vaso- constriction

85 Electrolytes, Fluids and Shock The venous system has a potentially huge unstressed volume which is controlled by many of the humoral and neural networks we have been discussing.The venous system has a potentially huge unstressed volume which is controlled by many of the humoral and neural networks we have been discussing. You know the difficulty in maintaining BP in someone in neurogenic shock. Large amounts of volume are initially needed to increase pressure.You know the difficulty in maintaining BP in someone in neurogenic shock. Large amounts of volume are initially needed to increase pressure. Although some of this BP fall is secondary to loss of arteriolar tone, until the venous tank is filled, arterial constrictors are poorly effective.Although some of this BP fall is secondary to loss of arteriolar tone, until the venous tank is filled, arterial constrictors are poorly effective. The Mean Systemic Pressure.

86 Electrolytes, Fluids and Shock A fall in arteriolar tone may permit more flow into the venous circuit. This will increase the mean systemic pressure once the unstressed volume is filled.A fall in arteriolar tone may permit more flow into the venous circuit. This will increase the mean systemic pressure once the unstressed volume is filled. Otherwise mean systemic pressure must be increased by reducing the venous capacity or by reducing the compliance of the veins. (Reducing the size of the bag or making the bag stiffer.)Otherwise mean systemic pressure must be increased by reducing the venous capacity or by reducing the compliance of the veins. (Reducing the size of the bag or making the bag stiffer.) These effects usually occur together in a reflex fashion.These effects usually occur together in a reflex fashion. The Mean Systemic Pressure.

87 Electrolytes, Fluids and Shock The Mean Systemic Pressure may be increased up to 40mmHg. In exercise or vaso-dilation.The Mean Systemic Pressure may be increased up to 40mmHg. In exercise or vaso-dilation. The higher the Mean Systemic Pressure, the greater will be the venous return.The higher the Mean Systemic Pressure, the greater will be the venous return. Venous return equals cardiac output.Venous return equals cardiac output. The Mean Systemic Pressure

88 Electrolytes, Fluids and Shock The Mean Systemic Pressure minus the right Atrial pressure is the pressure governing the venous return.The Mean Systemic Pressure minus the right Atrial pressure is the pressure governing the venous return. RVEF increases as RA pressure increases via the Frank-Starling mechanism.RVEF increases as RA pressure increases via the Frank-Starling mechanism. However, the higher the RA pressure the smaller will be the Mean Systemic to RA pressure promoting venous returnHowever, the higher the RA pressure the smaller will be the Mean Systemic to RA pressure promoting venous return The Mean Systemic Pressure

89 Electrolytes, Fluids and Shock The higher the RA pressure the smaller will be the Mean Systemic to RA pressure promoting venous return.The higher the RA pressure the smaller will be the Mean Systemic to RA pressure promoting venous return. There are a family of Venous return curves.There are a family of Venous return curves. The Mean Systemic Pressure

90 Electrolytes, Fluids and Shock The central venous pressure is dependent upon:The central venous pressure is dependent upon: –Blood Volume. –Venous Capacity and Resistance. –RV performance. This makes the CVP hard to understand. The Venous Anatomy and Venous Return

91 Electrolytes, Fluids and Shock Venous Return and Cardiac Function RA Pressure Cardiac output Venous Return or Venous Return and Cardiac Output are equal Mean Systemic Pressure

92 Electrolytes, Fluids and Shock Venous Return and Cardiac Function RA Pressure Cardiac output Venous Return or Cardiac Output can be increased in three ways A B Cardiac output increases from A to B from this increase in PMS

93 Electrolytes, Fluids and Shock Venous Return and Cardiac Function RA Pressure Cardiac output Venous Return or Cardiac Output can be increased in three ways: 1.Increase MSP 2.Increase up the Frank- Starling curve 3. Increase Cardiac Contractility

94 Electrolytes, Fluids and Shock

95 A 47 yr old man has planned open Right Hemi- Colectomy.A 47 yr old man has planned open Right Hemi- Colectomy. The Surgery is Uneventful.The Surgery is Uneventful. How would you manage his IV fluidsHow would you manage his IV fluids Mr. S. P: SBO with Shock

96 Electrolytes, Fluids and Shock A 47 yr old man has planned Laparoscopic Right Hemi-Colectomy.A 47 yr old man has planned Laparoscopic Right Hemi-Colectomy. The Surgery is Uneventful.The Surgery is Uneventful. How would you manage his IV fluidsHow would you manage his IV fluids Mr. S. P: SBO with Shock

97 Electrolytes, Fluids and Shock A 47 yr old man with no Co-morbidities has planned Laparoscopic or Open Right Hemi-Colectomy.A 47 yr old man with no Co-morbidities has planned Laparoscopic or Open Right Hemi-Colectomy. The Surgery is Uneventful.The Surgery is Uneventful. Why would you manage his IV fluids differently.Why would you manage his IV fluids differently. Mr. S. P: SBO with Shock

98 Electrolytes, Fluids and Shock A 47 yr old man with no Co-morbidities has planned Laparoscopic or Open Right Hemi-Colectomy.A 47 yr old man with no Co-morbidities has planned Laparoscopic or Open Right Hemi-Colectomy. The Surgery is complicated by Fecal Contamination and the need for an Ileostomy.The Surgery is complicated by Fecal Contamination and the need for an Ileostomy. Why would you manage his IV fluids differently.Why would you manage his IV fluids differently. Mr. S. P: SBO with Shock

99 Electrolytes, Fluids and Shock A 47 yr old man is admitted with bowel obstruction. He has been Vomiting for 2 days and has not eaten for 5 days.A 47 yr old man is admitted with bowel obstruction. He has been Vomiting for 2 days and has not eaten for 5 days. Surgery is complicated. Open Right Hemi-Colectomy is necessary.Surgery is complicated. Open Right Hemi-Colectomy is necessary. There is much Fecal Contamination and the need for an Ileostomy.There is much Fecal Contamination and the need for an Ileostomy. Why would you manage his IV fluids differently.Why would you manage his IV fluids differently. Mr. S. P: SBO with Shock

100 Electrolytes, Fluids and Shock A 47 yr old man is admitted with bowel obstruction. He has been Vomiting for 2 days and has not eaten for 5 days.A 47 yr old man is admitted with bowel obstruction. He has been Vomiting for 2 days and has not eaten for 5 days. Surgery is complicated. Open Right Hemi-Colectomy is necessary.Surgery is complicated. Open Right Hemi-Colectomy is necessary. There is much Fecal Contamination and the need for an Ileostomy.There is much Fecal Contamination and the need for an Ileostomy. Why would you manage his IV fluids differently.Why would you manage his IV fluids differently. He has a huge inflammatory processHe has a huge inflammatory process His micro-circulation is very alteredHis micro-circulation is very altered His Capillaries are LeakyHis Capillaries are Leaky Mr. S. P: SBO with Shock

101 Electrolytes, Fluids and Shock A 47 yr old man is admitted with bowel obstruction. He has been Vomiting for 2 days and has not eaten for 5 days.A 47 yr old man is admitted with bowel obstruction. He has been Vomiting for 2 days and has not eaten for 5 days. Surgery is complicated. Open Right Hemi-Colectomy is necessary.Surgery is complicated. Open Right Hemi-Colectomy is necessary. There is much Fecal Contamination and the need for an Ileostomy.There is much Fecal Contamination and the need for an Ileostomy. Why would you manage his IV fluids differently.Why would you manage his IV fluids differently. He has a huge inflammatory processHe has a huge inflammatory process His micro-circulation is very alteredHis micro-circulation is very altered His Capillaries are LeakyHis Capillaries are Leaky Would you admit him to ICU?Would you admit him to ICU? Would you leave him on the Ventilator?Would you leave him on the Ventilator? Would you put in an Epidural Catheter?Would you put in an Epidural Catheter? Mr. S. P: SBO with Shock

102 Electrolytes, Fluids and Shock A 47 yr old man develops has evident bowel obstruction on the background of severe Crohn’s disease.A 47 yr old man develops has evident bowel obstruction on the background of severe Crohn’s disease. His Blood work shows:His Blood work shows: –`Hb 90G/L WBC 18,000 His Na+ is 150, Cl-110, K+ 3.2, HCO Creatinine 320 pH 7.2, pCO 2 30, HCO 3, 10 pO 2 90 on nasal oxygen, Lactate 5pH 7.2, pCO 2 30, HCO 3, 10 pO 2 90 on nasal oxygen, Lactate 5 Mr. S. P: SBO with Shock How are you going to resuscitate him?

103 Electrolytes, Fluids and Shock ARTERIOLE VENULE X X Pressure ± 35 mmHg Pressure ± 7 mmHg What is the proportion of blood in the arterial side of the circulation compared to the Venous side?

104 ARTERIOLE in Sepsis; Pressure ± 30mmHg. VENULE in Sepsis: Pressure ± 20 mmHg. Capillary system in Sepsis Electrolytes, Fluids and Shock X VASOSPASM THROMBUS VASODILATATION

105 A 47 yr old man develops has evident bowel obstruction on the background of severe Crohn’s disease.A 47 yr old man develops has evident bowel obstruction on the background of severe Crohn’s disease. In intestinal obstruction, not only does absorbtion stop, fluid is secreted into the bowel lumen.In intestinal obstruction, not only does absorbtion stop, fluid is secreted into the bowel lumen. This can increase dilation/pressure enough to produce ischemia/translocation.This can increase dilation/pressure enough to produce ischemia/translocation. The shock state thus comprises:The shock state thus comprises: –Fluid loss from vomiting and inanition –Fluid loss into the gut –Leaky capillaries from inflammation/sepsis Mr. S. P: SBO with Shock How are you going to resuscitate him?

106 Electrolytes, Fluids and Shock Secretion typeVolumeNaKClHCO3 Stomach Small Intestine ColonLittle Pancreas Bile

107 Electrolytes, Fluids and Shock A 47 yr old man develops has evident bowel obstruction on the background of severe Crohn’s disease.A 47 yr old man develops has evident bowel obstruction on the background of severe Crohn’s disease. There is thus, hypovolemia, Sodium and Chloride loss.There is thus, hypovolemia, Sodium and Chloride loss. Intra-cellular cations (K+, Mg++) may be lost if this process has occurred over days.Intra-cellular cations (K+, Mg++) may be lost if this process has occurred over days. Mr. S. P: SBO with Shock How are you going to resuscitate him?

108 Can Your Patient Cope with the Inflammation of Surgery? Time Flow Ebb or Shock Phase Flow or Healing Phase The “ebb” phase is really the inflammatory stimulus induced by everything. The “flow” needed to permit healing is determined by the Ebb. But you are smart and the anesthetist is smart. No shock will occur during the surgery.

109 Can Your Patient Cope with the Inflammation of Surgery?

110 Cuthbertson Quart.J.Med.1932;1: Time Flow Ebb or Shock Phase Flow or Healing Phase The more severe and more prolonged the “ebb”, the greater the “flow” must be to permit healing.

111 That’s Enough about Science


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