Hypovolemic Shock

• Hypovolemic shock• Cardiogenic shock• Obstructive shock• Distributive shock

Classifications of Shock

Hypovolemic Shock• Loss of circulating volume “Empty tank ”

decrease tissue perfusion general shock response

• Etiology: – Internal or External fluid loss– Intracellular and extracellular compartments

• Most common causes:– Hemorrhage– Dehydration

Hypovolemic ShockExternal loss of fluid• Fluid loss

– Nausea & vomitting– Diarrhoea– Massive diuresis

• Plasma loss– Extensive burns

• Blood loss– Blunt– Penetrating

Hypovolemic ShockInternal fluid loss• Loss of vascular integrity• Increased capillary membrane

permeability• Decreased Colloidal Osmotic Pressure

(third spacing)

Imbalances Result From:

• Illness

• Altered fluid intake

• Prolonged vomiting or diarrhea

Fluid Intake• Average adult intake

– 2200-2700 ml/day• Oral : 1100-1400• Solid foods : 800-1000• Oxidative metabolism : 300

– By-product of cellular metabolism of ingested foods

Fluid Intake (cont)

• Must be alert• At risk for dehydration:

– Extreme of age– Neurological disorders– Psychological disorders

Fluid Output Regulation• Kidneys

– Major regulatory organ• Receive about 180 liters of blood/day to filter• Produce 1200-1500 ml of urine

• Skin– Regulated by sympathetic nervous system

• Activates sweat glands– Sensible or insensible-500-600 ml/day

» Directly related to stimulation of sweat glands

• Respiration– Insensible

• Increases with rate and depth of respirations, oxygen delivery– About 400 ml/day

• Gastrointestinal tract – In stool

– Average about 100-200 ml/day» GI disorders may increase or decrease it.

Fluid BalanceFluid Balance

1200-1500 ml urine1200-1500 ml urine

500-600 ml sweat500-600 ml sweat

400 ml respiration400 ml respiration

100-200 ml stool100-200 ml stool

1100-1400 ml oral fuid1100-1400 ml oral fuid

800-1000 ml solid food800-1000 ml solid food

300 ml oxidative 300 ml oxidative metabolismmetabolism

inputinput outputoutput

Fluid Imbalance (hypovolemia)Fluid Imbalance (hypovolemia)

inputinput outputoutputUrine Urine Sweat Sweat Resp. Resp.

DiarrhoeaDiarrhoeaVomittingVomittingBleedingBleeding

Internal fluid lossInternal fluid loss

Intake Intake

Clinical Presentation• Tachycardia and tachypnea• Weak, thready pulses• Hypotension • Skin cool & clammy• Mental status changes• Decreased urine output: dark &

concentrated

Dehydration• Irritability Increased HR with• Confusion decreased BP• Dizziness• Weakness• Extreme thrist• Fever• Dry skin & mucus membranes• Sunken eyeballs• Poor skin turgor• Decreased urine output

Assessing/Managing Fluid Status

• Measuring I & O– Difficult

– Daily weight • Same day• Same clothes, etc• same scale

Assessing/Managing Fluid Status

• Insert Foley catheter to monitor I & O• Monitor vital signs closely• IV therapy• Monitor labs:

– Na+, serum osmolarity, urine specific gravity• Provide skin & oral care frequently• Auscultation of breath sounds• ABG’s for fluid overload• Diuretics if fluid overload

Assessing Fluid Status

• Labs– Creatinine - measure of renal function– BUN - not as reliable

Severe Hypovolemiais a consequence of

• Trauma• Dehydration• Shock syndrome - sepsis, cardiac• Hemorrhage - intra-operative blood loss

Each cause may respond differently to different type of fluid

Hypotension may be a late sign of Hypovolemia

Compensatory Mechanisms

• Redistribution of blood flow– Heart– Brain

• Redistribution of blood volume– Intracellular– Interstitial

• Neurohormonal renin-angiotensin ‘double edge sword’

The reservoirs: ECF and Microcirculation

The Circulatory System (s)

• Macrocirculation• 50% of blood volume• Hb• Plasma• Mixed end products

• Microcirculation• 50% of blood volume• Control local flow• Hb• Plasma• Hemostasis

mediators• Hemodynamic

mediators• Inflammatory

mediators• Oxygen transport

> 250m < 250m

MicrocirculationEndothelium cells or organ“Role of regulation, signal transduction, proliferation and

repair”.» Nitric Oxide production» Endothelin» Rheology and cell adhesion» Leukocyte activation» Clotting » Lysis» Regulation of oxygen transport and more

Management of Hypovolemia

Current – oldTherapy is directed towards

• Optimize Macrocirculation• Optimize Oxygen delivery

New - future Therapy is directed towards

• Optimize the Microcirculation• Reducing the effect compensatory mechanisms

ManagementFive major principles• Prompt recognition – Do not rely on BP!!• Early institution of supportive measures

– ABC– Restore circulating volume

• Determine primary problem leading to shock.• Early correction of primary underlying

problem.– Control vomitting, diarrhoea, hemorrhage

• Management of complications.

Monitoring the CirculationMonitoring the Circulation

• Vital signsVital signs• PAWP and cardiac indexPAWP and cardiac index• Arterial and venous oxygen admixtureArterial and venous oxygen admixture• Gastric and other tissue oxygen and/or Gastric and other tissue oxygen and/or

carbon dioxide tensioncarbon dioxide tension• Base deficit and lactate levelsBase deficit and lactate levels

No direct measure of effects of No direct measure of effects of hypovolemia on cell survivalhypovolemia on cell survival

Shoemaker WC et al. Shoemaker WC et al. CCMCCM 1999;27(10) 1999;27(10)

Shock ManagementShock ManagementAirwayAirway

• Does the patient need tracheal Does the patient need tracheal intubation?intubation?– Most pts. w/ fully developed shock Most pts. w/ fully developed shock

require intubation and mechanical vent. require intubation and mechanical vent. • Resp. muscles require disproportionate Resp. muscles require disproportionate

share of total cardiac output during shock. share of total cardiac output during shock. • Mental status often abnormal severelyMental status often abnormal severely• Pulmonary complications including ARDSPulmonary complications including ARDS

Shock ManagementShock ManagementInitial therapy for hypotensionInitial therapy for hypotension

• Aggressive therapy indicated for BP < Aggressive therapy indicated for BP < 90 syst.; 40 < baseline; or MAP < 50-60. 90 syst.; 40 < baseline; or MAP < 50-60.

• Two large bore IV’s and poss. central Two large bore IV’s and poss. central venous line (large bore introducer 8.5 frvenous line (large bore introducer 8.5 fr

• If no evidence of cardiogenic pulmonary If no evidence of cardiogenic pulmonary edema, trial of volume expansion and edema, trial of volume expansion and vasopressor therepyvasopressor therepy

Shock ManagementShock ManagementInitial therapy for hypotensionInitial therapy for hypotension

• Initially, 1-2 litres crystalloid or 500-750 Initially, 1-2 litres crystalloid or 500-750 of colloid during the first hour. of colloid during the first hour.

• Severe BP drop is disasterous to brain Severe BP drop is disasterous to brain and heart. Use vasopressor initially, and heart. Use vasopressor initially, even in hypovolemic shock, in order to even in hypovolemic shock, in order to keep MAP > 50-60 until caught up w/ keep MAP > 50-60 until caught up w/ volume. volume.

Shock ManagementShock ManagementInitial therapy for hypotensionInitial therapy for hypotension

• Rate and type of on-going fluid Rate and type of on-going fluid administration depends on:administration depends on:– Clinical scenario - Clinical response Clinical scenario - Clinical response

• Presence of pulmonary edema (cardiac Presence of pulmonary edema (cardiac or non-cardiac) is strong or non-cardiac) is strong contraindication to more fluid admin contraindication to more fluid admin withoutwithout more hemodynamic informations more hemodynamic informations

Shock ManagementShock ManagementUse of SG catheterUse of SG catheter

• Should be employed to – Sort out type of shock– Guide therapy– Sort out confusing dilemmas (eg,

hypotension with pulmonary infiltrates)

Shock ManagementShock ManagementEndpoint of ResuscitationEndpoint of Resuscitation

• Reversal of previous abnormalities. • Cerebral, renal function improvement• BP up, HR down, improved 02• Improving base deficits, MV02 up

Monitor response of therapies!

Shock ManagementShock ManagementOutcome and MortalityOutcome and Mortality

• Dependant on– Severity.– Duration.– Underlying cause.– Pre-morbid organ disease / function.– Reversibility of clinical syndrome.

Dehydration

• Mild (3-5% BW)• Moderate (5-8% BW)• Severe (> 8% BW)

Volume ReplacementVolume Replacement• Maintenance fluidsMaintenance fluids• Replace deficit:Replace deficit:

– Rapid : iv bolusRapid : iv bolus– Intermediate : replace ½ deficit over 6-8 hrsIntermediate : replace ½ deficit over 6-8 hrs– Slow : remainder over 16-18 hrsSlow : remainder over 16-18 hrs

• Replace ongoing losses: Insensible losses, Replace ongoing losses: Insensible losses, GI losses, renal losses, burns.GI losses, renal losses, burns.

• e.g.:e.g.: FluidFluid NaNa K+K+ Cl -Cl -GastricGastric 20-8020-80 5-305-30 100-120100-120

BileBile 120-140120-140 2-102-10 90-12090-120

IleostomyIleostomy 100-140100-140 5-155-15 80-12080-120