electrolytes, fluids, acid base balance and shock

Electrolytes, Electrolytes, Fluids, Acid Base Fluids, Acid Base

Balance and ShockBalance and Shock

Gwynne JonesGwynne Jones

Critical CareCritical Care

Electrolytes, Fluids, Acid Base Balance Electrolytes, Fluids, Acid Base Balance and Shockand Shock

• Correct Fluid Management faqcilitatescrucial Homeostasis.

• This permits:– Optimum Cardio-vascular perfusion– Optimum Organ Function– Optimum Cellular Function

• 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

• 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.

• 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

• 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

• Electrolyte Concentration is usually expressed in terms of chemical combining activity, or equivalents.

• Equivalent = Atomic Wt (g)/valence

• 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)

• 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

Electrolytes, Fluids and Electrolytes, Fluids and ShockShock

• Two Thirds of the body Water is in Two Thirds of the body Water is in the cells.the cells.

• This is between 30L to 40 L.This is between 30L to 40 L.• Is has an Electrolyte composition Is has an Electrolyte composition

very different from the Extra-very different from the Extra-cellular water.cellular water.

•What is this What is this difference?difference?

Electrolytes, Fluids and Electrolytes, Fluids and ShockShock• 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/LPotassium: 150 mMol/L– Sodium: 10 mMol/LSodium: 10 mMol/L– Magnesium: 40 mMol/L.Magnesium: 40 mMol/L.– Calcium and Hydrogen: nanoMols/LCalcium and Hydrogen: nanoMols/L

• Anions:Anions:– Phosphate and Sulphate ± 150 mMol/L.Phosphate and Sulphate ± 150 mMol/L.– Proteinate ± 40 mMol/LProteinate ± 40 mMol/L– Bicarbonate ± 10 mMol/L Bicarbonate ± 10 mMol/L

• Two Thirds of the body Water is in Two Thirds of the body Water is in the cells.the cells.

• This is between 30L to 40 L.This is between 30L to 40 L.• Is has an Electrolyte composition Is has an Electrolyte composition

very different from the Extra-very different from the Extra-cellular water.cellular water.

•How is it maintained? How is it maintained?

Electrolytes, Fluids and Electrolytes, Fluids and ShockShock• Two Thirds of the body Two Thirds of the body

Water is in the cells.Water is in the cells.

• Electrolyte Electrolyte composition:composition:

• Cations:Cations:– Potassium: 150 mMol/LPotassium: 150 mMol/L– Sodium: 10 mMol/LSodium: 10 mMol/L– Magnesium: 40 mMol/L.Magnesium: 40 mMol/L.– Calcium and Hydrogen: Calcium and Hydrogen:

nanoMols/LnanoMols/L

• Anions:Anions:– Phosphate and Sulphate ± Phosphate and Sulphate ±

150 mMol/L.150 mMol/L.– Proteinate ± 40 mMol/LProteinate ± 40 mMol/L– Bicarbonate ± 10 mMol/L Bicarbonate ± 10 mMol/L

These These differences differences are are maintained by maintained by various cell various cell membrane ion membrane ion pumps.pumps.Na/K ATPase Na/K ATPase driven driven exchangers exchangers are most are most importantimportant

These differences are These differences are maintained by various ion maintained by various ion pumps.pumps.Na/K ATPase driven Na/K ATPase driven exchangers are most exchangers are most importantimportant

After Severe After Severe Shock 20% of Shock 20% of Oxygen/fuel Oxygen/fuel consumption is consumption is used just to used just to pump the Sodium pump the Sodium out of the cells.out of the cells.

These differences are These differences are maintained by various ion maintained by various ion pumps.pumps.Na/K ATPase driven Na/K ATPase driven exchangers are most exchangers are most important.important.

Cell volume Cell volume fluctuates a little in fluctuates a little in shock and has some shock and has some influence on influence on resuscitation fluid resuscitation fluid choice.choice.In the presence of In the presence of shock (the ebb shock (the ebb phase) they swell.phase) they swell.In more chronic In more chronic severe illness (after severe illness (after shock/flow phase) shock/flow phase) they shrink.they shrink.

These differences are These differences are maintained by various maintained by various ion pumps.ion pumps.Na/K ATPase driven Na/K ATPase driven exchangers are most exchangers are most important.important.Cell volume Cell volume fluctuates a little in fluctuates a little in shock and has some shock and has some influence on influence on resuscitation fluid resuscitation fluid choice.choice.1. Smaller cells 1. Smaller cells switch off protein switch off protein production and thus production and thus contribute to contribute to nitrogen loss.nitrogen loss.

These differences are These differences are maintained by various ion maintained by various ion pumps.pumps.Na/K ATPase driven Na/K ATPase driven exchangers are most exchangers are most important.important.Cell volume fluctuates Cell volume fluctuates a little in shock. Cells a little in shock. Cells are smaller in are smaller in recovering shock.recovering shock.2. Insulin and certain 2. Insulin and certain Amino Acids stimulate Amino Acids stimulate protein synthesis . The protein synthesis . The re-feeding syndrome is re-feeding syndrome is associated with this. associated with this. How?How?

150 mMol/L.150 mMol/L.– Proteinate ± 40 mMol/LProteinate ± 40 mMol/L– Bicardonate ± 10 mMol/L Bicardonate ± 10 mMol/L

The cell is thus a The cell is thus a rich sauce.rich sauce.It is the lean It is the lean body mass that body mass that we survive on.we survive on.For the rest of For the rest of the talk/life we the talk/life we leave them in the leave them in the background.background.We forget them We forget them at our peril.at our peril.

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?

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.

There is a subtle difference between blood/plasma and interstitial fluid.Sodium passively determines the extracellular space volume.

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!

Whose Law determines the mechanism by which these intravascular /interstitial volumes are maintained?

Whose Law determines the mechanism by which this intravascular /interstitial process is maintained?

Starling’s Law.

Jv = Ks (Ppl - Pis) - Jv = Ks (Ppl - Pis) - σσ ( (ππpl pl - - ππis)is)

Jv = Ks (Ppl - Pis) - σ (πpl - πis)

–What is σ and why is it important?

–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)

Jv = Ks (Ppl - Pis) - σ (πpl - πis) The endothelium is more The endothelium is more

complex than initially complex than initially imagined.imagined.The endothelium is The endothelium is covered by a glyco-calyx.covered by a glyco-calyx.These two barriers: the These two barriers: the Endothelium and the Endothelium and the Glycocalyx are co-Glycocalyx are co-operative.operative.Damage to either one is Damage to either one is not associated with an not associated with an increase in fluid flux.increase in fluid flux.Damage to both is Damage to both is associated with severe associated with severe leaky vessels (capillaries)leaky vessels (capillaries)

Jv = Ks (Ppl - Pis) - σ (πpl - πis) The endothelium is The endothelium is

more complex than more complex than initially imagined. The initially imagined. The endothelium is covered endothelium is covered by a glyco-calyx.by a glyco-calyx.These two barriers These two barriers are co-operative:are co-operative:The endothelium is The endothelium is damaged damaged particularly by particularly by Reactive Oxygen Reactive Oxygen Species (ROS)Species (ROS)The glyco-calyx is The glyco-calyx is damaged damaged particularly by particularly by proteases.proteases.

Jv = Ks (Ppl - Pis) - σ (πpl - πis) The endothelium is more complex than The endothelium is more complex than

initially imagined. The endothelium is initially imagined. The endothelium is covered by a glyco-calyx.covered by a glyco-calyx.

These two barriers are co-These two barriers are co-operative. They allow a flow operative. They allow a flow of interstitial fluid enriched of interstitial fluid enriched by sugar and electrolytes.by sugar and electrolytes.The ¼ Blood/Plasma: ¾ The ¼ Blood/Plasma: ¾ interstitial fluid ratio in interstitial fluid ratio in health is maintained.health is maintained.Excess is taken up by Excess is taken up by lymphatics and returned to lymphatics and returned to the blood via the thoracic the blood via the thoracic duct.duct.

Blood Volume is Blood Volume is ± 5L in the adult.± 5L in the adult.45% is RBCs45% is RBCsThe rest is an The rest is an aqueous solution aqueous solution of electrolytes of electrolytes and proteins.and proteins.The proteins are The proteins are functional:functional:ImmunoglobulinsImmunoglobulinsCoagulation Coagulation factorsfactorsComplementComplementAlbuminAlbuminHormonesHormonesEtc.Etc.

Blood Blood Volume is ± Volume is ± 5L in the 5L in the adult.adult.Blood Blood Volume is Volume is highly highly regulated by: regulated by: What?What?

Blood Blood Volume is ± Volume is ± 5L in the 5L in the adult.adult.Blood Blood Volume is Volume is highly highly regulated by:regulated by:Pressure Pressure Sensors.Sensors.Volume Volume Sensors.Sensors.Osmo-Osmo-receptors.receptors.

Blood Volume is ± Blood Volume is ± 5L in the adult. 5L in the adult. Blood Volume is Blood Volume is highly regulated highly regulated by:by:Pressure Sensors:Pressure Sensors:

Carotid Sinus, Renal Carotid Sinus, Renal Vessels.Vessels.

Volume Sensors:Volume Sensors:Large Veins/AtriaLarge Veins/Atria..

Osmo-receptors:Osmo-receptors:HypothalamusHypothalamus..

Blood Volume is ± 5L in the Blood Volume is ± 5L in the adult. Blood Volume is highly adult. Blood Volume is highly regulated by:regulated by:Pressure Sensors:Pressure Sensors:

Carotid Sinus, Renal Vessels.Carotid Sinus, Renal Vessels.

Volume Sensors:Volume Sensors:Large Vein/AtriaLarge Vein/Atria..

Osmo-receptors:Osmo-receptors:HypothalamusHypothalamus..

These act via the These act via the Autonomic Nervous Autonomic Nervous system, the system, the hypothalamic-Pituitary hypothalamic-Pituitary Axis and adrenal glands Axis and adrenal glands to stimulate thirst, to stimulate thirst, Sodium and Water Sodium and Water Retention, Vaso-Retention, Vaso-constriction etc.constriction etc.

Blood Volume is ± 5L in the adult. Blood Volume is ± 5L in the adult. Blood Volume is highly regulated Blood Volume is highly regulated by:by:Pressure Sensors:Pressure Sensors:

Carotid Sinus, Renal Vessels.Carotid Sinus, Renal Vessels.

Volume Sensors:Volume Sensors:Large Vein/AtriaLarge Vein/Atria..

Osmo-receptors:Osmo-receptors:HypothalamusHypothalamus..These act via the Autonomic These act via the Autonomic

Nervous system, the Nervous system, the hypothalamic-Pituitary Axis and hypothalamic-Pituitary Axis and adrenal glands to stimulate adrenal glands to stimulate thirst, Water Retention, Vaso-thirst, Water Retention, Vaso-constriction etc.constriction etc.Tell me about the hormones!

ADHADHCATECHOLAMINCATECHOLAMINESESANGIOTENSINANGIOTENSINCORTISOLCORTISOLALDOSTERONEALDOSTERONEATRIAL ATRIAL NATRIURETIC NATRIURETIC HORMONEHORMONEENDOTHELINENDOTHELIN

Electrolytes, Fluids and ShockElectrolytes, Fluids and Shock

This is going to get This is going to get Harder!Harder!

Acid-Base Balance. Hydrogen is in Nano-Acid-Base Balance. Hydrogen is in Nano-Molar quantitiesMolar quantities

Hydrogen is in Nano-Molar quantities.Hydrogen is in Nano-Molar quantities.It all has to do with the dissociation of water.It all has to do with the dissociation of water.Most of the water is not dissociated Most of the water is not dissociated (55mMol/L.)(55mMol/L.)1010-14 -14 nMol/L of water is dissociated into nMol/L of water is dissociated into HH++and OHand OH--

If all is HIf all is H++ the pH is zero. If all is OH the pH is zero. If all is OH- - the pH the pH is 14.is 14.The pH scale is zero to 14, neutral is a pH of The pH scale is zero to 14, neutral is a pH of 77

Acid-Base Balance.Acid-Base Balance.

Acid-Base Balance. Hydrogen is in Nano-Molar quantities.Acid-Base Balance. Hydrogen is in Nano-Molar quantities.It all has to do with the dissociation of water.It all has to do with the dissociation of water.Most of the water is not dissociated.Most of the water is not dissociated.1010-14 -14 nMol/L is dissociated into HnMol/L is dissociated into H++and OHand OH--

If all is HIf all is H++ the pH is zero. If all is OH the pH is zero. If all is OH- - the pH is 14.the pH is 14.The pH scale is zero to 14, neutral is a pH of 7The 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 proteinsThe Strong Ion difference (SID

Acid-Base Balance. Hydrogen is in Nano-Molar quantities.Acid-Base Balance. Hydrogen is in Nano-Molar quantities.It all has to do with the dissociation of water.It all has to do with the dissociation of water.Most of the water is not dissociated.Most of the water is not dissociated.1010-14 -14 nMol/L is dissociated into HnMol/L is dissociated into H++and OHand OH--

If all is HIf all is H++ the pH is zero. If all is OH the pH is zero. If all is OH- - the pH is 14.the pH is 14.The pH scale is zero to 14, neutral is a pH of 7The 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.

•The Bicarbonate The Bicarbonate SystemSystem

[CO[CO22] [H] [H22O]O] [H[H++] ] [HCO[HCO33]]

HCOHCO33

pCOpCO22

4040 8080

25251 for 10 1 for 10 acutely.acutely.

How long does it take?How long does it take?

Pulmonary Ventilation and Gas Pulmonary Ventilation and Gas ExchangeExchange

HCOHCO33

pCOpCO22

4040 8080

25253 for 10 3 for 10 chronically.chronically.

How long does it How long does it take?take?

• A 47 yr old man develops has evident bowel A 47 yr old man develops has evident bowel obstruction on the background of severe obstruction on the background of severe Crohn’s disease.Crohn’s disease.

• His Blood work shows:His Blood work shows:– `Hb 90G/L WBC 18,000`Hb 90G/L WBC 18,000

His Na+ is 150, Cl-110, K+ 3.2, HCOHis Na+ is 150, Cl-110, K+ 3.2, HCO33 10. Creatinine 10. Creatinine 320320

• pH 7.2, pCOpH 7.2, pCO22 30, HCO 30, HCO33, 10 pO, 10 pO22 90 on nasal oxygen, 90 on nasal oxygen, Lactate 5 Lactate 5

Mr. S. P: SBO with ShockMr. S. P: SBO with Shock

How are you going to How are you going to resuscitate him?resuscitate him?

pCOpCO22 = KKVCOVCO22________________

Alv. Vent.Alv. Vent.

pCOpCO22

Won’t or Can’t Won’t or Can’t BreathBreathAlveolar Alveolar HyperventilationHyperventilation

Energy Metabolism in Energy Metabolism in Critically IllCritically IllGLYCOLYSISGLYCOLYSIS

Why does bicarbonate fall, on Why does bicarbonate fall, on roughly a mol for mol basis, when roughly a mol for mol basis, when lactic acidosis occurs?lactic acidosis occurs?

HH++ HCO HCO33 HH22COCO33 COCO22

HH22OO

Energy Metabolism in Energy Metabolism in Critically IllCritically IllGLYCOLYSISGLYCOLYSIS

Why does bicarbonate fall, on Why does bicarbonate fall, on roughly a mol for mol basis, when roughly a mol for mol basis, when lactic acidosis occurs?lactic acidosis occurs?

HLactate + NaHCOHLactate + NaHCO33 NaLactate NaLactate + H+ H22COCO33

HH++ HCO HCO33 HH22COCO33 COCO22

HH22OO

What are What are the the determinantdeterminants of Cardiac s of Cardiac Output?Output?

Cardiac Output Cardiac Output is determined by is determined by four variables:four variables:

PreloadPreloadAfterloadAfterloadContractilityContractilityHeart RateHeart Rate

Cardiac Output Cardiac Output is determined by is determined by four variables:four variables:1. Preload: This 1. Preload: This is the force or is the force or load that load that stretches the stretches the cardiac muscle cardiac muscle prior to prior to contraction.contraction.

Cardiac Output is Cardiac Output is determined by four variables.determined by four variables.

Afterload: This is the Afterload: This is the impedence to outflow impedence to outflow of the ventricle.of the ventricle.This includes the size This includes the size of the ventricle (La of the ventricle (La Place), The SVR, PVR, Place), The SVR, PVR, compliance of large compliance of large vessels and the vessels and the pleural pressure pleural pressure

Cardiac Output must equal Cardiac Output must equal Venous return.Venous return.Venous return is determined Venous return is determined by five variables:by five variables:

Stressed Vascular Stressed Vascular VolumeVolumeVenous ComplianceVenous ComplianceVenous ResistanceVenous ResistanceDistribution of Blood Distribution of Blood FlowFlowRight Atrial PressureRight Atrial Pressure

Electrolytes, Fluids and Shock: Electrolytes, Fluids and Shock: Venous ReturnVenous Return

This is hard but worth This is hard but worth thinking about!thinking about!

ARTERIOLEARTERIOLEVENULEVENULE

Pressure Pressure ± 35 ± 35 mmHgmmHg

What is the proportion of blood in What is the proportion of blood in the arterial side of the circulation the arterial side of the circulation compared to the Venous side?compared to the Venous side?

What is the proportion of blood in What is the proportion of blood in the arterial side of the circulation the arterial side of the circulation compared to the Venous side: ± compared to the Venous side: ± 70%.70%. Why?Why?

•The Veins are very The Veins are very compliant.compliant.

• The arteries are not.The arteries are not.

The Venous Anatomy and The Venous Anatomy and Venous ReturnVenous Return

• The Veins are very compliant.The Veins are very compliant.• The elastic recoil of the compliant The elastic recoil of the compliant

capacity vessels is a potential energy capacity vessels is a potential energy (filled by the arterial pressure).(filled by the arterial pressure).

• This potential energy of elastic This potential energy of elastic recoil acts to transfer blood recoil acts to transfer blood towards the heart maintaining towards the heart maintaining cardiac filling and output.cardiac filling and output.

• The Veins are very compliant.The Veins are very compliant.

• The elastic veins have an The elastic veins have an elasticity that allows them to act elasticity that allows them to act like an auxiliary pumplike an auxiliary pump

• There is a progressive drop in pressure There is a progressive drop in pressure within the systemic circuit from the within the systemic circuit from the highest value, at the outlet of the left highest value, at the outlet of the left ventricle to the lowest value, at the ventricle to the lowest value, at the right atrium.right atrium.

• What would happen to these pressures What would happen to these pressures if it were possible to switch off the if it were possible to switch off the heart, without reflex change, for 30 heart, without reflex change, for 30 seconds?seconds?

The Venous Anatomy and Venous The Venous Anatomy and Venous ReturnReturn

• What would happen to these pressures if it were possible What would happen to these pressures if it were possible to switch off the heart, without reflex change, for 30 to switch off the heart, without reflex change, for 30 seconds?seconds?

• Without flow, the pressure throughout the Without flow, the pressure throughout the system would equalise to a level determined system would equalise to a level determined by the compliance of the whole system.by the compliance of the whole system.

• As the venous system is hugely compliant, As the venous system is hugely compliant, the pressure would equalise at a pressure the pressure would equalise at a pressure just above the RA pressure. just above the RA pressure.

• This is This is The Mean Systemic Pressure.The Mean Systemic Pressure.

Pressure Pressure ± 7 ± 7 mmHgmmHgThis is This is

the the mean mean systemic systemic pressurepressure

• Without flow, the pressure throughout the system Without flow, the pressure throughout the system would equalise at all points to a level determined would equalise at all points to a level determined by the compliance of the whole system.by the compliance of the whole system.

• This is This is The Mean Systemic The Mean Systemic Pressure.Pressure.

• It is the pressure in the small veins which It is the pressure in the small veins which distends the capacitance vessels, thereby distends the capacitance vessels, thereby producing a potential energy for flow to return to producing a potential energy for flow to return to the RA.the RA.

• The RA pressure is constantly emptied by The RA pressure is constantly emptied by the RVthe RV

• As the venous system is hugely compliant, the As the venous system is hugely compliant, the pressure would equalise at a pressure just above pressure would equalise at a pressure just above the RA pressure. The Mean Systemic Pressure.the RA pressure. The Mean Systemic Pressure.

• The Mean Systemic Pressure is the The Mean Systemic Pressure is the driving pressure for venous return. driving pressure for venous return.

• It is 5 to 10 mmHg. in the normal It is 5 to 10 mmHg. in the normal circulation.circulation.

• As RA pressure is less, only - 4 to + 4 As RA pressure is less, only - 4 to + 4 mmHg., venous return is fine. mmHg., venous return is fine.

The Mean Systemic Pressure.The Mean Systemic Pressure.

• As the venous system is hugely compliant, the pressure would equalise As the venous system is hugely compliant, the pressure would equalise at a pressure just above the RA pressure. The Mean Systemic Pressure.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 Job of the Right Ventricle is The Job of the Right Ventricle is to keep the Right Atrium empty.to keep the Right Atrium empty.It does the job amazingly well as It does the job amazingly well as long as the RV afterload is low (ie long as the RV afterload is low (ie the lungs are OK).the lungs are OK).

Electrolytes, Fluids and ShockElectrolytes, Fluids and ShockThe Mean Systemic Pressure.The Mean Systemic Pressure.

Imagine the pressure Imagine the pressure change as you fill a change as you fill a collapsed bag.collapsed bag.

Until filled, there will be Until filled, there will be no pressure changeno pressure change

The bag is very compliant. The bag is very compliant. It has a It has a large unstressed large unstressed volumevolume

This is how the veins are with a blood This is how the veins are with a blood volume of 4Lvolume of 4L..

• Now the bag has filled, Now the bag has filled, the pressure will the pressure will increase in proportion increase in proportion to the compliance of to the compliance of the wall of the bag, the wall of the bag, together with the rate together with the rate at which fluid is at which fluid is entering the bag.entering the bag.

• You have reached the You have reached the bag’s bag’s stressed volume.stressed volume.

This is how the veins are with a blood This is how the veins are with a blood volume of 5L.volume of 5L.

This is how the veins are with a blood This is how the veins are with a blood volume of 4Lvolume of 4L..

Fluid Resuscitation would be Fluid Resuscitation would be Good. Which Fluid would you Good. Which Fluid would you Choose?Choose?

Electrolytes, Fluids and ShockElectrolytes, Fluids and ShockVenous Return and Cardiac FunctionVenous Return and Cardiac Function

Venous Venous ReturnReturn

RA PressureRA Pressure

Venous return will be zero Venous return will be zero when RA pressure equals when RA pressure equals mean systemic pressuremean systemic pressure

Mean Systemic Pressure

Are We Treating The Right Are We Treating The Right Ventricle?Ventricle?

Venous Return and Cardiac FunctionVenous Return and Cardiac Function

Cardiac Cardiac outputoutput

Venous Venous return can return can be increased be increased in three in three waysways

1. Reduce Atrial Pressure1. Reduce Atrial Pressure

2. Increase PMS2. Increase PMS

Electrolytes, Fluids and ShockElectrolytes, Fluids and ShockThe Mean Systemic Pressure (PMS).The Mean Systemic Pressure (PMS).

Systemic Systemic Vascular Vascular volumevolume

Mean systemic pressureMean systemic pressure

INFUSED VOLUMEINFUSED VOLUME

INCREASED PMSINCREASED PMS

REDUCTION IN REDUCTION IN UNSTRESSED VOLUMEUNSTRESSED VOLUME

INCREASED PMSINCREASED PMSDECREASE IN DECREASE IN COMPLIANCECOMPLIANCE

INCREASED PMSINCREASED PMS

Electrolytes, Fluids and ShockElectrolytes, 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-Pre-load recruitable stroke work (move up the Frank-Starling Curve) increases LV end-

diastolic pressure.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 This high wedge/PAOP induces pulmonary hypertension, thereby increasing RV

afterload.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 Sympathetic activation at low levels mostly produces a decrease in venous capacity.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 This volume load increases venous return and right

ventricular dilation.ventricular dilation.• RV volume increase may increase RV ejection RV volume increase may increase RV ejection

fraction, although the high RV afterload may not fraction, although the high RV afterload may not permit this increase, The RV being excellent at permit this increase, The RV being excellent at increasing output if impedence is low but poor when increasing output if impedence is low but poor when impedence to outflow is high, as in pulmonary impedence to outflow is high, as in pulmonary hypertension.hypertension.

Sympathetic Nervous System Sympathetic Nervous System OutputOutput

Systemic Systemic Vascular Vascular ResistancResistancee

Venous Venous CapacityCapacity SVRSVR

Effect of Sympathetic activation Effect of Sympathetic activation on preload and afterloadon preload and afterload

The Venous InnervationThe Venous Innervation

ArteryArtery

Sympathetic Sympathetic NerveNerve

αα11αα11αα11

αα22αα22

αα22αα22 αα22αα22

VeinVeinαα11αα11αα11

αα11αα11αα11

αα22αα22

αα22αα22αα22αα

The Venous InnervationThe Venous Innervation

ArteryArtery

αα1 or 1 or αα22

VeinVeinoror

Adenyl Adenyl CyclaseCyclase

Cyclic Cyclic AMPAMP ProteiProtei

n n Kinase Kinase GG

PhosphodiesterPhosphodiesterase 3ase 3

Multiple Multiple KinasesKinases

iCaiCa++++ Vaso-Vaso-constrictconstrictionion

• The venous system has a potentially huge The venous system has a potentially huge unstressed volume which is controlled by unstressed volume which is controlled by many of the humoral and neural networks we many of the humoral and neural networks we have been discussing.have been discussing.

• You know the difficulty in maintaining BP in You know the difficulty in maintaining BP in someone in neurogenic shock. Large someone in neurogenic shock. Large amounts of volume are initially needed to amounts of volume are initially needed to increase pressure.increase pressure.

• Although some of this BP fall is secondary to Although some of this BP fall is secondary to loss of arteriolar tone, until the venous tank loss of arteriolar tone, until the venous tank is filled, arterial constrictors are poorly is filled, arterial constrictors are poorly effective. effective.

• A fall in arteriolar tone may permit more A fall in arteriolar tone may permit more flow into the venous circuit. This will flow into the venous circuit. This will increase the mean systemic pressure increase the mean systemic pressure once the unstressed volume is filled.once the unstressed volume is filled.

• Otherwise mean systemic pressure must Otherwise mean systemic pressure must be increased by reducing the venous be increased by reducing the venous capacity or by reducing the compliance capacity or by reducing the compliance of the veins. (Reducing the size of the of the veins. (Reducing the size of the bag or making the bag stiffer.)bag or making the bag stiffer.)

• These effects usually occur together in a These effects usually occur together in a reflex fashion.reflex fashion.

• The Mean Systemic Pressure may The Mean Systemic Pressure may be increased up to 40mmHg. In be increased up to 40mmHg. In exercise or vaso-dilation.exercise or vaso-dilation.

• The higher the Mean Systemic The higher the Mean Systemic Pressure, the greater will be the Pressure, the greater will be the venous return.venous return.

• Venous return equals cardiac Venous return equals cardiac output.output.

The Mean Systemic PressureThe Mean Systemic Pressure

• The Mean Systemic Pressure minus the The Mean Systemic Pressure minus the right Atrial pressure is the pressure right Atrial pressure is the pressure governing the venous return.governing the venous return.

• RVEF increases as RA pressure RVEF increases as RA pressure increases via the Frank-Starling increases via the Frank-Starling mechanism.mechanism.

• However, the higher the RA pressure However, the higher the RA pressure the smaller will be the Mean Systemic the smaller will be the Mean Systemic to RA pressure promoting venous to RA pressure promoting venous returnreturn

• The higher the RA pressure the The higher the RA pressure the smaller will be the Mean smaller will be the Mean Systemic to RA pressure Systemic to RA pressure promoting venous return.promoting venous return.

• There are a family of Venous There are a family of Venous return curves.return curves.

• The central venous pressure is The central venous pressure is dependent upon:dependent upon:– Blood Volume.Blood Volume.– Venous Capacity and Resistance.Venous Capacity and Resistance.– RV performance.RV performance.

This makes the CVP hard to This makes the CVP hard to understand.understand.

Venous Return and Venous Return and Cardiac Output are Cardiac Output are equalequal

Mean Systemic Mean Systemic PressurePressure

Cardiac Cardiac Output can Output can be increased be increased in three waysin three ways

Cardiac output increases from A to B Cardiac output increases from A to B from this increase in PMSfrom this increase in PMS

Venous Return and Cardiac FunctionVenous Return and Cardiac Function

Cardiac Output can be Cardiac Output can be increased in three ways:increased in three ways:

1.1.Increase MSPIncrease MSP

2.2.Increase up the Frank- Increase up the Frank- Starling curveStarling curve

3. Increase Cardiac 3. Increase Cardiac ContractilityContractility

3. Increase Cardiac Contractility3. Increase Cardiac Contractility

• A 47 yr old man has planned open Right A 47 yr old man has planned open Right Hemi-Colectomy.Hemi-Colectomy.

• The Surgery is Uneventful.The Surgery is Uneventful.• How would you manage his IV fluidsHow would you manage his IV fluids

• A 47 yr old man has planned A 47 yr old man has planned Laparoscopic Right Hemi-Colectomy.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

• A 47 yr old man with no Co-morbidities A 47 yr old man with no Co-morbidities has planned Laparoscopic or Open Right has planned Laparoscopic or Open Right Hemi-Colectomy.Hemi-Colectomy.

• The Surgery is Uneventful.The Surgery is Uneventful.• Why would you manage his IV fluids Why would you manage his IV fluids

differently.differently.

• A 47 yr old man with no Co-morbidities A 47 yr old man with no Co-morbidities has planned Laparoscopic or Open Right has planned Laparoscopic or Open Right Hemi-Colectomy.Hemi-Colectomy.

• The Surgery is complicated by Fecal The Surgery is complicated by Fecal Contamination and the need for an Contamination and the need for an Ileostomy.Ileostomy.

• Why would you manage his IV fluids Why would you manage his IV fluids differently.differently.

• A 47 yr old man is admitted with bowel A 47 yr old man is admitted with bowel obstruction. He has been Vomiting for 2 obstruction. He has been Vomiting for 2 days and has not eaten for 5 days.days and has not eaten for 5 days.

• Surgery is complicated. Open Right Hemi-Surgery is complicated. Open Right Hemi-Colectomy is necessary.Colectomy is necessary.

• There is much Fecal Contamination and the There is much Fecal Contamination and the need for an Ileostomy.need for an Ileostomy.

• A 47 yr old man is admitted with bowel obstruction. He has been A 47 yr old man is admitted with bowel obstruction. He has been Vomiting for 2 days and has not eaten for 5 days.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 There is much Fecal Contamination and the need for an

Ileostomy.Ileostomy.

• 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

• A 47 yr old man is admitted with bowel obstruction. He has been Vomiting for 2 days and has not eaten for A 47 yr old man is admitted with bowel obstruction. He has been Vomiting for 2 days and has not eaten for 5 days.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?

• His Blood work shows:His Blood work shows:– `Hb 90G/L WBC 18,000`Hb 90G/L WBC 18,000

His Na+ is 150, Cl-110, K+ 3.2, HCOHis Na+ is 150, Cl-110, K+ 3.2, HCO33 10. Creatinine 10. Creatinine 320320

• pH 7.2, pCOpH 7.2, pCO22 30, HCO 30, HCO33, 10 pO, 10 pO22 90 on nasal oxygen, 90 on nasal oxygen, Lactate 5 Lactate 5

What is the proportion of blood in What is the proportion of blood in the arterial side of the circulation the arterial side of the circulation compared to the Venous side?compared to the Venous side?

ARTERIOLE in ARTERIOLE in Sepsis; Pressure Sepsis; Pressure ± ± 30mmHg.30mmHg.

VENULE in VENULE in Sepsis: Sepsis: Pressure Pressure ± ± 20 mmHg.20 mmHg.

Capillary system in SepsisCapillary system in Sepsis

VASOSPASMVASOSPASM

THROMBUSTHROMBUS

VASODILATATIONVASODILATATION

• In intestinal obstruction, not only does absorbtion stop, fluid is In intestinal obstruction, not only does absorbtion stop, fluid is secreted into the bowel lumen.secreted into the bowel lumen.

• This can increase dilation/pressure enough to produce This can increase dilation/pressure enough to produce ischemia/translocation.ischemia/translocation.

• The shock state thus comprises:The shock state thus comprises:– Fluid loss from vomiting and inanitionFluid loss from vomiting and inanition– Fluid loss into the gutFluid loss into the gut– Leaky capillaries from inflammation/sepsisLeaky capillaries from inflammation/sepsis

Secretion type

Volume Na K Cl HCO3

Stomach 1000-2000

60-90 10-30 100-130 0

Small Intestine

2000-3000

120-140 5-10 90-120 30-40

Colon Little 60 30 40 0

Pancreas 600-800 135-145 5-10 70-90 95-115

Bile 300-800 135-145 5-10 90-110 30-40

• There is thus, hypovolemia, Sodium and There is thus, hypovolemia, Sodium and Chloride loss.Chloride loss.

• Intra-cellular cations (K+, Mg++) may Intra-cellular cations (K+, Mg++) may be lost if this process has occurred over be lost if this process has occurred over days.days.

Can Your Patient Cope with the Can Your Patient Cope with the Inflammation of Surgery?Inflammation of Surgery?

Ebb Ebb or or Shock Shock PhasePhase

Flow or Healing PhaseFlow or Healing Phase

The “ebb” phase is really the The “ebb” phase is really the inflammatory stimulus inflammatory stimulus induced by everything. induced by everything.

The “flow” needed to permit The “flow” needed to permit healing is determined by the healing is determined by the Ebb.Ebb.

But you are smart and the anesthetist is smart. No shock will occur during the surgery.

Can Your Patient Cope with the Can Your Patient Cope with the Inflammation of Surgery?Inflammation of Surgery?

Cuthbertson Quart.J.Med.1932;1:233-38Cuthbertson Quart.J.Med.1932;1:233-38Time

Ebb Ebb or or Shock Shock PhasePhase

Flow or Healing PhaseFlow or Healing Phase

The more severe and more The more severe and more prolonged the “ebb”, the prolonged the “ebb”, the greater the “flow” must be to greater the “flow” must be to permit healing.permit healing.

That’s Enough about That’s Enough about ScienceScience

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