Eric Schroeder DVM, MS, DACVECC, DACVIMThe Ohio State University College of Veterinary Medicine

601 Vernon L TharpColumbus Ohio 43210

schroeder.257@osu.edu

Hydrating the Dehydrated Horse: Practical Fluid Therapy for the General

Practitioner

Goals for the Presentation

o What is the Fluid Composition of the horse

• Where is all the water?• What are the maintenance needs?

o Assessing Fluid Loss• Dehydration• Hypovolemia

o Oral Fluid Therapy

o Practical Intravenous Fluid Therapy

o What to do With Fluid Shortage?

11/3/2018 2

Introductiono Fluid Therapy

• Corner stone of treatment• Part almost every treatment plan General farm veterinary care Hospital veterinary care

o Fluid therapy is one of the oldest therapies

o Fluid therapy is continuously widely debated in veterinary and human medicine

• What is debated about it? Volume, shock dose vs. maintenance dose? How should each be defined?

Types of fluids colloid vs. crystalloid? Fluid additives?

11/3/2018 3

Critical Care Medicine

o Delivery of large volumes of IV fluids

o Polyionic fluids (IV vs. Orally), colloids, and partial or total parenteral nutrition

o Long term fluid therapy• Replacement therapy • Maintenance therapy No ideal solution for this

11/3/2018 4

Critical Care Medicine

o IV fluid therapy (USA)• 5L fluid bags:~1 million

used annually (Abbott, Baxter, Dechra)

• Considered replacement fluids Composition similar to ECF No energy source provided

• Requires additives Potassium chloride Magnesium sulfate Calcium gluconate

o Replacement fluids=Lots of salt

o Currently the best that we have

>50,000 kg salt>$30 million

11/3/2018 5

Route of Fluid Therapy

o Oralo Intravenous

11/3/2018 6

“Critical” In the Field Medicine

o Are there Other Options?

o Will paste salt solutions work ?

11/3/2018 7

“Critical” In the Field Careo Must consider:

• Type of patient (neonate vs. adult)• Lesion that is present/suspected To date large colon impaction/displacement and spasmotic

colic remain the two most common causes of colicPrimary care facility vs. referral hospital

• Enteral fluid therapy +/- hypertonic electrolyte paste/slurries remain viable therapies for these types of colic Potentially more physiologic increased colonic motilityGastrocolic reflexPotentially more economically appealing

11/3/2018 8

450-500 kg (1000-1200 lb) Horse

60% H2O BWT

300 liters (80 gallons)

2/3 or 66% ICF200 liters

(60 gallons)

1/3 or 33%ECF

100 liters(30 gallons)

25% intravascular50% interstitial

25% transcellular

What makes up the Horse

11/3/2018 9

Central Osmoreceptors = THIRSTo Within the CNS, osmoreceptors

sense changes in plasma osmolality

• Normal ~280 mOsm/L• Increased sodium (Na+) • Receptors triggered with ≤ 2%

change in osmolalityo Activate thirst receptors o ↓ saliva / sensation of dry

moutho Encourages water consumption

11/3/2018 10

How is Fluid Balance controlled in the Body

o Effective circulating volume Blood volume• Renin angiotensin aldosterone system Control renal reabsorption of Na and water in the collecting

ductso Regulation of Osmolality

• ADH controls plasma osmolality• Hypothalamic osmole receptors Sense change in plasma osmolality Changes of

How is Fluid Balance controlled in the Body

Ineffective Osmole

Effective OsmoleConsidered Na, Glucose, Cl, K

11/3/2018 12

Water Movement Between Compartments?o Movement of water:

• Continuous revolving door • Cellular, interstitial, transcellular, and vascular compartments• Requirement for survival

o Movement of water is related to: • “Effective” osmoles DO NOT cross the cell membrane freelyMain effective osmoles (Na, glucose)Mannitol, ketoacids, lactic acid, phosphate, sulfate, contrast

• “Ineffective” osmole DO cross the cell membrane freelyBUN, ethylene glycol, ethanol, methanol, acetylsalicylic acid, isopropyl alcohol

11/3/2018 13

Semi-permeable membranes separate the fluid compartments: fluids are in constant motion between the 3 compartments

plasma

endothelium

tissue cells

Arteriolar end

filtrationreabsorption

Venularend

interstitial fluid

osmosis

11/3/2018 14

Oncotic Pressure:

o Proteins create oncotic pressure (COP) • Albumin 70%• Globulins, fibrinogen, SAA

plasma

endothelium

tissue cells

Arteriolar end

filtrationreabsorption

Venularend

interstitial fluid

osmosis

11/3/2018 15

Edema

plasma

endothelium

tissue cells

Arteriolar end

filtrationreabsorption

Venularend

interstitial fluid

osmosis

11/3/2018 16

Bandaging: Increase Interstitial Pressure

11/3/2018 17

Daily Fluid Ins and Outso 450 kg horse drinks

• 40- 60 ml/kg/day or • 18-27 liters of H2O=5.25 gallons• Dependent on ambient

temperature/activityo Produces 3L daily metabolismo Urinary loss = 5Lo Fecal loss = 20Lo Incessant losses

sweat/breathing11/3/2018 18

DEHYDRATION VS. HYPOVOLEMIA

What’s The Difference

11/3/2018 19

Failure to Replace Losseso Failure to replace insensible losses leads to

Dehydration• Loss of total body water• Failure or inability to drink

o Failure to replace isotonic fluid loss leads to Hypovolemia

• Loss of water + electrolytes• Horses with gastrointestinal losses Diarrhea Nasogastric reflux

• Blood loss• Sepsis/Endotoxemia Vascular fluid pooling

11/3/2018 20

Clinical Signs of Dehydration

o Tachycardiao Irritabilityo Increased skin tento Sunken eyeso Concentrated urineo Dry mucous

membraneso Muscle spasms and

crampingo Difficult to quantify

“opinion driven”

11/3/2018 21

Estimation of % Dehydration:

o 5 – 7% = Mild dehydration • Decreased skin turgor, slightly tacky membranes

o 8 – 10% = Moderate dehydration • Depressed mentation, tacky mm, CRT > 2 – 3 sec• Correlates with hypovolemia

o > 10% = Severe dehydration• Cool extremities, poor perfusion, CRT > 4 sec

o > 15% Lethal

Exam findings are insensitive

11/3/2018 22

Parameters used for Estimation of Dehydration in theHorse

% Dehydration

Heart RateBPM

CRT PCV% / TP g/dl

Creatininemg/dl

6 40-50 2 s 40/ 7 1.5 - 2

8 51-60 3 s 45 / 7.5 2 - 3

10 81-100 4 s 50 / 8 3 – 4

12 >100 >4 s >50 / >8 >4

11/3/2018 23

Cases!

11/3/2018 24

Case #1: Estimating Volume Deficit from Dehydration

o 400 kg horseo Sick 3 days

• Fever• Depression• Poor appetite• Not drinking well

11/3/2018 25

Physical Examination

o S = Depressedo O = T: 101.0F

HR: 50 bpm RR: 28 bpm

o A = Dehydratedo P = 400 kg X 0.06 = 24 liters

o % dehydration equation=o Bw(kg)x % dehydration = Liters11/3/2018 26

Replace Fluid Deficit

o Oral or enteral fluid therapyo Intravenous

• Polyionic (balanced)• Polyionic (hypertonic)• Colloids Plasma Hetastarch Blood

11/3/2018 27

Enteral Fluid Therapy

o Advantages• Fluid does not have to be sterile: cheaper• Estimate electrolyte supplementation• Small intestinal H2O absorption• Stimulates gastro-colic reflex

o Disadvantages• Patients with moderate to severe dehydration• Ileus and/or malabsorption due to ischemia/hypoperfusion• Gastric outflow obstruction Positive net reflux Requires intravenous fluid therapy

11/3/2018 28

Gastric Capacity

o 450 – 500 kg horseo Comfortably 6 - 8 literso Accommodates 20

literso Emptying time

• Water 30 minutes• Hay 3 – 5 hours

o Delayed emptying• Hypoperfusion• Colic

11/3/2018 29

400 kg Horse 6% Dehydratedo Deficit = 24 liters = 400 kg X 0.06o Maintenance = 20 liters = 400 kg X 40-60

ml/kg/24 hourso 24 hours: 44 literso Plan

• Pass nasogastric tube• Administer 10 liters warm water + 2 oz NaCl + 2 oz KCl

• Every 2 – 4 hours “ One kidney is smarter than all the internists in the world.”11/3/2018 30

Oral/Enteral Fluids

o Commercially available• Resorb

o Oral electrolyte solution• NaCl 10 gm• NaHCO3 15 gm• KCl 75 gm• K2HPO4 60 gm• Q 21 liters of water

11/3/2018 31

Oral/Enteral Fluids

o Enteral Fluids• Useful for treatment of

impaction colic• May also include

osmotic agents

11/3/2018 32

What About Mineral Oil?

o Great marker• 8- 10 hours• Suggests patency• Lubricant

o Doesn’t penetrate impaction

• Does not soften impaction• May be absorbed into

enterocyteo Risk of aspiration

• “Paraffin aspiration”11/3/2018 33

Goals for the Presentation

o Fluid Composition of the horse• Where is the water?• Maintenance needs

o Assessing Fluid Loss• Dehydration• Hypovolemia

o Oral Fluid Therapyo Practical Intravenous Fluid Therapyo What to do with fluid shortage?

11/3/2018 34

Hypovolemic Case – Within Hours

o Loss of vascular volume• Blood loss• Plasma volume• Isotonic fluid loss

o Maldistribution of vascular volume• Sepsis -/+• Septic shock

11/3/2018 35

Hypovolemia

o Depressed/abnormal mentation

• Standing back of stall• Head down• Ears back

o Tachycardia (> 60 bpm)o Tachypnea (> 20 bpm)o Cold appendageso Prolonged CRTo Abnormal mucous

membraneso Poor

• Jugular fill• Pulse pressure

o Not urinating11/3/2018 36

Dehydration vs. Hypovolemia

Dehydrationo Dayso Decrease in TBW o Failure to replace watero Increased skin tento Dry membraneso Muscle crampingo Mild tachycardia

Hypovolemiao Hourso Loss of vascular volumeo Very debilitatedo Shock stateso Indices of poor tissue

perfusiono Tachycardiao Hemoconcentration

11/3/2018 37

Tools to Aid Your Diagnosis…

o PCV• Hematocrit

o Total Solids• Refractometer

(combine with PCV)• Estimate of oncotic

pressure

11/3/2018 38

Additional laboratory data:o Serum Creatinine

• Pre-renal azotemia BUN + creatinine

• Creatinine > 1.5 mg/dl

o Urine specific gravity• Concentrated urine (>1.025)

11/3/2018 39

Additional Laboratory Data:

o Lactate:• Commonly produced anaerobic metabolism poor tissue oxygenation

• Normal < 2 mmol/l• Causes of increased lactate Hypovolemia Endotoxemia Ischemic intestine Myopathy

11/3/2018 40

Fluids Available for Horses

o Intravenous Crystalloids: Isotonic vs. Polyionic

Product pH mOsmol/L Na K Ca Mg Cl Buffer

Lactated Ringers 6.5 273 130 4 3 109 Lactate 28

Plasmalyte 148 7.4 294 140 5 3 98 Acetate 27

0.9%NaCl 5 308 154 154

Normasol-R 6.4 295 140 5 3 98 Acetate 27Gluconate 23

11/3/2018 41

Sheet1

ProductpHmOsmol/LNaKCaMgClBuffer

Lactated Ringers6.527313043109Lactate 28

Plasmalyte 1487.42941405398Acetate 27

0.9%NaCl5308154154

Normasol-R6.42951405398Acetate 27

Gluconate 23

Sheet2

Characteristics of colloid fluids

Characteristics5%albumin25% albuminOxypolygelatinDextran 40Dextran 70PentastarchHetastarch

Molecular weight (Da)

weight average69,00069,00030,00040,00070,000280,000450,000

number-average69,00069,00022,000-24,00025,00039,00039,00070,000

range5,600-100,00010,000-80,00015,000-160,00010,000-1,000,00010,000-3,400,000

SolventBES0.9% saline0.9% saline0.9% saline0.9% saline

or 5% dextroseor 5% dextroseor BES

Maximum water18183937293020

binding (ml/g)

Concentration (%)5255.6106106

Half-life14-16 days14-16 days2-4 hours2.5 hrs6 hrs2.5 hrs25 hrs

Plasma percentage121829738

(after 24 hrs)

Extravascular22333339

percentage (After 24 hrs)

Overall survival168 hrs44 hrs4-6 weeks96 hrs17-26 weeks

in blood

Colloid oncotic2010045-47402530

pressure (mm Hg)

Sheet3

Designing a Fluid Therapy Regimen

o Determine AMOUNT to give per dayo Determine TYPE of fluid to giveo Determine METHOD of fluid administration

11/3/2018 42

Fluid Therapy Regimens

MAINTENANCE

No dehydrationNo additional lossesFluid composition

Low NaLow ClHigher KHigher Mg

REPLACEMENT

DehydrationOngoing lossesFluid composition

Similar to plasma

11/3/2018 43

Fluid Replacement - Amounto Maintenance + % dehydration + ongoing losses

• Total fluid plan/24 hours Dynamic patiient

o Bw(kg) x % dehydration = L of fluids to correct dehydration

o 40-60 ml/kg/day x BW(kg)= L/day Maintenance

o Shock Dose 80-100ml/kg= give in ¼ dose amounts for total of 100ml/kg

• Reserved for patients displaying signs of hypovolemia

11/3/2018 44

Dehydration Vs. Hypovolemia

o A horse can be suffering from both dehydration that has progressed to be also hypovolemia

However………………….o A hypovolemic horse CANNOT ever become

systemically dehydrated…… It will be dead

11/3/2018 45

Evaluation of Dehydration vs Hypovolemia

o History• Acute vs chronic

o Physical exam• Heart rate, mucous

membraneso Laboratory data

• PCV/TP, creatinine

11/3/2018 46

Evaluation of Hypovolemia

o Aggressive volume supporto Intravenous fluids

• IV catheter• Method for administration

o Crytalloids• Polyionic (80 – 100 ml/kg) “Shock dose” Give in ¼ volumes and reassess

• Hypertonic (4 ml/kg)o Colloids

• Plasma• Hetastarch (10 -25 ml/kg)

Equine Infectious Diseases, Sellon & Long, 2007.

11/3/2018 47

Types of Catheters Available

o Catheter material:• Teflon Rigid Most thrombogenic Short-term use only

• Polyurethane Least thrombogenic Supple, may be more difficult to place Long-term use

11/3/2018 48

IV Catheter Placement

o Aseptic techniqueo Suture in place

• ± Bandage useful for protection

o Monitor site for signs of inflammation• Thrombophlebitis

o Flush frequently• Heparinized saline• Heparin lock (3 ml heparin) 12 -

24 hourso Change extension set /

PRN cap as needed11/3/2018 49

Size of Cathetero Larger bore catheters for

emergency resuscitation 10 – 14 go Greater the radius

• Faster the fluids run in to the 4thpower

o Shorter the catheter length multiply flow by 8

Q = π r 4 P 8 η L

11/3/2018 50

Using Crystalloid Fluids• Emergency Therapy

• Hypertonic saline: 4 ml/kg or 2 liters/1000 lbs• Administer 2 L 7.2 %NaCl• Administer 20 L isotonic replacement

• Expand the vascular volume• Positive ionotropic effects

• Improve cardiac output• Improve oxygen delivery

11/3/2018 51

http://www.vetone.net/images/pdf/hypertonic_sellsheet.pdf

Hypertonic saline pulls water from the intracellular space into the vascular space4 X amount givenLasts 30 – 60 minutes

plasma

endothelium

tissue cells

Arteriolar end

filtrationreabsorption

Venularend

interstitial fluid

osmosis

Na+

Na+

Cl+

Cl+

Cl+

Cl+

Na+

Na+ Na+

Cl+

H2O H2O H2O

H2O H2O H2O

Cl+Cl+

11/3/2018 52

Emergency Crystalloid Therapy

11/3/2018 53

5 yr. old Arabian gelding – 400 kg

o Digital vessel lacerationo Hypovolemia

• HR = 80 - 100 bpm• Membranes = pale• Cold ears/muzzle• Very quiet

o Stop the bleeding• Tight bandage

o Administer • 2 liters 7.4% saline• 30 liters LRS

11/3/2018 54

Response to therapy:

o Signs at presentation:o Quieto HR 80 - 100 bpm o Tacky , CRT > 3so Slow jugular fillo Poor pulse pressureo Cool distal extremities

o Response to Therapy:o Brighter, Front of stallo HR = 56 bpmo Moist, CRT ~1.5 so Improved jugular fillo Stronger pulse pressureo Urination!!

…following 2L hypertonic + 30L crystalloid…

11/3/2018 55

But I can’t even get IV fluids

http://www.fullbuckethealth.com/latest-articles/cat/fullbucket-products/post/how-to-deal-with-iv-fluid-shortage-v2/11/3/2018 56

But I can’t even get IV fluids

19 liters of 0.9% NaCl Can mix with 110 g NaCl

11/3/2018 57

But I can’t even get IV fluids

http://www.fullbuckethealth.com/latest-articles/cat/fullbucket-products/post/how-to-deal-with-iv-fluid-shortage-v2/

Complicationso Signs of endotoxemia

• Tachycardia• Fever• Colicky?• Muscle fasciculations/shaking

o Why these clinical signs with fluids• Potential risk for endotoxin present in the distilled H2O

o Potential increased risk of vein phlebitis and thrombophlebitis?

• Most likely no greater risk then with conventional fluidso Is this a revelation in “standard of care”

• Will the shortage end?11/3/2018 59

Questions?

11/3/2018 60

Thank You

11/3/2018 61

Low Oncotic Pressure

o PCV = 55%o TS = 3.5 g/dlo Albumin = 1.0 g/dlo Colloid Therapy

• Plasma or hetastarch or both• 10 -25 ml/kg hetastarch• 100 kg X 10 ml/kg = 1 liter

11/3/2018 71

Fluid Therapy Plan

o Place IV cathetero Administer 1 liter hetastarcho Follow with 9 liters LRS

• Bolus 3 liters• 6 liters 1 - 2 liters/hr

o Monitor response to therapyo Will she drink?

11/3/2018 72

Slide Number 1Goals for the PresentationIntroductionCritical Care MedicineCritical Care MedicineRoute of Fluid Therapy“Critical” In the Field Medicine “Critical” In the Field CareWhat makes up the HorseCentral Osmoreceptors = THIRSTHow is Fluid Balance controlled in the BodyHow is Fluid Balance controlled in the BodyWater Movement Between Compartments?Semi-permeable membranes separate the fluid compartments: fluids are in constant motion between the 3 compartmentsOncotic Pressure:EdemaBandaging: Increase Interstitial PressureDaily Fluid Ins and OutsDehydration vs. HypovolemiaFailure to Replace LossesClinical Signs of DehydrationEstimation of % Dehydration:Slide Number 23Cases!Case #1: Estimating Volume Deficit from DehydrationPhysical ExaminationReplace Fluid DeficitEnteral Fluid TherapyGastric Capacity400 kg Horse 6% DehydratedOral/Enteral FluidsOral/Enteral FluidsWhat About Mineral �Oil?Goals for the PresentationHypovolemic Case – Within HoursHypovolemiaDehydration vs. Hypovolemia Tools to Aid Your Diagnosis…Additional laboratory data:Additional Laboratory Data:Fluids Available for HorsesDesigning a Fluid Therapy RegimenFluid Therapy RegimensFluid Replacement - AmountDehydration Vs. HypovolemiaEvaluation of Dehydration vs HypovolemiaEvaluation of HypovolemiaTypes of Catheters Available IV Catheter PlacementSize of CatheterUsing Crystalloid FluidsHypertonic saline pulls water from the intracellular space into the vascular space�4 X amount given�Lasts 30 – 60 minutes��Emergency Crystalloid Therapy5 yr. old Arabian gelding – 400 kgResponse to therapy:But I can’t even get IV fluidsBut I can’t even get IV fluidsBut I can’t even get IV fluidsComplicationsQuestions?Thank YouLow Oncotic PressureFluid Therapy Plan