fluid therapy

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Questions and Answers

What is the primary characteristic of hypovolaemia?

Decrease fluid volume within the vascular space (correct)

Increased electrolyte retention in the vascular space

Loss of only electrolytes without fluid loss

Decrease fluid volume in the interstitial compartment

Which of the following is NOT a consequence of dehydration?

Decrease in blood volume

Rapid onset of circulatory shock (correct)

Water and electrolytes imbalance

Slow, sustained replacement requirement

Which laboratory test result is typically associated with hypovolaemia?

Increased packed cell volume (PCV)

Increased urine output

Increased lactate levels (correct)

Normal total solids (TS)

What physical examination finding is commonly associated with hypovolaemia?

Cold extremities Signup and view all the answers

Which of the following describes the fluid volume effects of dehydration compared to hypovolaemia?

Dehydration reduces fluid in the interstitial compartment Signup and view all the answers

What percentage of body weight in adults is typically made up of total body water?

60% Signup and view all the answers

Which fluid compartment represents the largest portion of total body water in adults?

Intracellular fluids Signup and view all the answers

What is the typical percentage range of blood volume in dogs and horses relative to their body mass?

8-9% Signup and view all the answers

What is the primary factor determining fluid movement between body fluid compartments?

Tonicity of fluid and extracellular compartment Signup and view all the answers

What defines hypovolaemia in a patient?

Insufficient blood plasma volume Signup and view all the answers

What percentage of body weight in neonates is made up of total body water?

80% Signup and view all the answers

Which of the following is NOT a typical indication for different types of intravenous fluids?

Pain management Signup and view all the answers

What is a risk associated with administering too much intravenous fluid?

Iatrogenic fluid overload Signup and view all the answers

What is the primary role of colloids in fluid therapy?

To expand intravascular volume for longer durations Signup and view all the answers

Which of the following is a synthetic colloid?

Hetastarch Signup and view all the answers

What should be monitored closely during a treatment plan for hypovolemia?

Response to bolus administration Signup and view all the answers

What is the recommended maximum amount of colloids for a dog during treatment?

20 mL/kg Signup and view all the answers

What is the preferred method of fluid administration for severe dehydration?

Intravenous or intraosseous administration Signup and view all the answers

Which solution is suitable for maintenance fluid therapy?

Hypotonic crystalloids Signup and view all the answers

For a cat weighing 4 kg and experiencing mild dehydration of 8%, what is the total fluid deficit calculation?

0.24 L Signup and view all the answers

What is the typical dosage range for hypertonic crystalloids in dogs?

4-6 mL/kg Signup and view all the answers

What is the primary use of Hartmann's solution?

For replacement and resuscitation Signup and view all the answers

What is the mechanism through which Hartmann's solution exerts a bicarbonate-sparing effect?

By consuming hydrogen ions during lactate metabolism Signup and view all the answers

What is the primary purpose of hypertonic crystalloids in fluid therapy?

To achieve rapid intravascular volume expansion Signup and view all the answers

Which of the following should be carefully monitored when administering hypertonic crystalloids?

Coagulation status Signup and view all the answers

What condition is primarily treated using hypotonic crystalloids?

Hypernatremia Signup and view all the answers

What effect does hypertonic solution have regarding perfusion?

Causes vasodilation Signup and view all the answers

Which characteristic of hypotonic crystalloids can be helpful in avoiding damage to red blood cells?

Addition of dextrose Signup and view all the answers

What is the recommended rate of administration for hypertonic crystalloids?

No faster than 1 ml/kg/min Signup and view all the answers

What is the recommended first step when treating hypovolemia and dehydration?

Address hypovolemia first Signup and view all the answers

What is the daily fluid requirement for a hydrated dog that cannot maintain fluid homeostasis orally?

60 mL/kg/day Signup and view all the answers

What is a key goal of fluid therapy during anesthesia?

To enhance tissue perfusion Signup and view all the answers

Which approach is recommended for administering fluids during anesthesia?

Administer fluids based on patient's needs Signup and view all the answers

What type of fluid is suggested for short-term hydration in patients?

Isotonic crystalloids with K and dextrose Signup and view all the answers

When calculating the drops per second, which information is NOT needed?

Current heart rate of the patient Signup and view all the answers

In pediatric patients, what is the daily fluid requirement for a dog compared to an adult dog?

3 X adult dose Signup and view all the answers

Which of the following is considered a risk when using gravity-assisted fluid administration?

Fluid overload Signup and view all the answers

What should be monitored to maintain blood pressure during anesthesia?

Oxygen delivery and tissue perfusion Signup and view all the answers

What is the volume to be infused (VTBI) in using infusion pumps?

Total amount of fluid to be delivered Signup and view all the answers

What happens to sodium concentration during dehydration?

It increases, leading to hypernatremia. Signup and view all the answers

What is the formula to calculate free water deficit?

Free Water Deficit (L) = [(Patient Na / Desired Na) – 1] X 0.6 X Weight (kg) Signup and view all the answers

Which type of crystalloids has a higher osmolality than plasma?

Hypertonic crystalloids Signup and view all the answers

Which statement about saline solution (0.9% NaCl) is true?

It causes a Hamburger shift. Signup and view all the answers

What typically happens to isotonic crystalloids within 30-60 minutes after administration?

They redistribute from intravascular space to interstitial space. Signup and view all the answers

What are crystalloids primarily composed of?

Crystalline compounds dissolved in water. Signup and view all the answers

What is the primary role of Na-K-ATPase pumps in relation to sodium?

To pump sodium ions out of the cell, maintaining concentration gradients. Signup and view all the answers

Study Notes

Fluid Therapy

Fluid Therapy lecture by Hanna Machin, Dip ACVAA, Dip SIAV, MVetMed, MRCVS, Lecturer in Veterinary Anaesthesia, October 4, 2024.

Learning Objectives

Describe the normal distribution of fluid within the body.
Define hypovolaemia and dehydration.
Describe different types of intravenous fluids available and their relative indications.
Describe normal fluid requirements and suggest a treatment plan for maintenance.
Suggest a treatment plan for a hypovolaemic and/or dehydrated patient.
Identify patients at risk of iatrogenic fluid overload.

Total Body Water

Adults: 60% of body weight is total body water, 40% is dry matter.
Neonates: 80% of body weight is total body water, 20% is dry matter.

Fluid Compartments (Adults)

Total Body Water (TBW): 40% of body mass.
Intracellular fluid (2/3 of TBW): 40%
Extracellular fluid (1/3 of TBW): 20%
- Interstitial fluid (3/4 of ECF): 15%
- Intravascular fluid (1/4 of ECF): 5%

Total Blood Volume

Dog/Horse: 8-9% of body mass (80-90 mL/kg).
Cat/Cattle/Sheep: 6-7% of body mass (60-70 mL/kg).

The Body's Fluid Compartments

Fluids move between compartments based on tonicity of the fluid, tonicity of the extracellular compartment (Na+), and the size of macromolecules in the fluid.
Movement occurs across endothelial membranes, which depend on capillary membrane condition, hydrostatic pressure, colloid osmotic pressure, and vascular permeability.

Types of Fluid Loss

Water & electrolytes (ECF loss): Vomiting, diarrhea, diuresis.
Protein-rich ECF loss: Transudate, exudate, effusion, severe enteritis, protein-losing enteropathy/nephropathy.
Pure water: High RR (hyperthermia, pneumonia), water deprivation, excessive water loss.

Fluid Balance

Gains: Water intake (food & water); metabolic water production (10%).
Sensible Losses: Urine output.
Insensible Losses: Faeces, Respiration, Saliva, Cutaneous (sweating), respiratory tract.

Maintenance Requirements

Dog: a. 60 mL/kg/day; b. 132 x BW (kg)^0.75 ; c. 30 x BW (kg) + 70 = mL/kg/day
Cat: a. 40 mL/kg/day; b. 80 x BW (kg)^0.75 ; c. 30 x BW (kg) + 70 = mL/kg/day
Pediatric: Dog: 3 x adult dose; Cat: 2.5 x adult dose.
Losses = Sensible losses + Insensible losses = ~50 mL/kg/day (Over 24 hrs).

Goal Directed Fluid Therapy

Restore homeostasis (euvolemia & hydration).
Correct acid-base & electrolyte imbalances.
Assess the deficit(s).
Choose the best fluid type to replace the deficit(s).
Calculate fluid dose & rate.
Monitor patient's response & potential complications.
Reassess treatment plan.
Adapt plan to patient's needs.
Goal: Zero balance.

Fluids are Drugs...

Are IV fluids indicated?
Correct drug choice.
Correct dose/volume.
Administration (rate/bolus).
Patient considerations (hypotension? causes? contraindications?).
Monitoring.
Side effects.

Hypovolemia vs Dehydration

Hypovolemia: Decrease in fluid volume within the vascular space, leading to tissue perfusion loss, blood and/or fluid & electrolyte loss. Rapid replacement therapy.
Dehydration: Decrease in fluid volume within the interstitial compartment, affecting all compartments. Causes water & electrolyte imbalance(especially Na+). Requires slower, sustained replacement.

Assessing Intravascular Space Deficits (Hypovolemia)

History: V+, D+, anorexia, fever, hemorrhage, edema, ascites
Physical examination: Altered mentation, tachycardia/arrhythmias, changes in CRT & MM (vasoconstriction), weak peripheral pulses, low BP, cold extremities, tachypnoea.
Laboratory tests: ↓ PCV, TS, ↑ lactate, metabolic acidosis, anaemia, electrolyte abnormalities, ↓ urine output, ↑ urine specific gravity.

Phases of Hypovolemic Shock

Compensatory
Early decompensatory
Late decompensatory

Assessing Dehydration

Physical Examination Findings by Dehydration percentage.
Different parameters for assessment include skin turgor, mucous membrane moisture, PCV, total protein, blood urea nitrogen, urine osmolality, and urine specific gravity.

Assessing Intracellular Space

Sodium concentration
Free water deficit.
Na-K-ATPase pumps.
Water moves freely.
Dehydration: Hypernatremia and hypertonicity.

Types of Fluids Available

Crystalloids
Colloids
Oxygen-carrying solutions
Blood products

Crystalloids

Solutions prepared with crystalline compounds (electrolytes +/– sugar) in water, often with buffers (acetate, lactate, gluconate).
Classification: tonicity (isotonic, hypotonic, hypertonic) compared to plasma.

Isotonic Crystalloids

Composition matches extracellular fluid.
Redistribution of fluid from intravascular to interstitial space over 30-60 minutes.
Only 25% remains in intravascular space
Includes: 0.9% NaCl, Hartmann's, Plasma-Lyte 148.

Saline Solution (0.9% NaCl)

Not balanced.
Acidifying solution.
Potential risk for heart or renal disease.

Hartmann's Solution

Balanced, most used for replacement/resuscitation and peri-operative fluid therapy.
Contains precursors for bicarbonate (lactate).
Liver converts lactate into glucose, consuming H+, which is HCO3- sparing effect).
Careful with blood transfusions (clots).

Hypertonic Crystalloids (7.5% NaCl)

Rapid intravascular volume expansion (3X volume infused).
Draws water from ICF & ECF to intravascular space (transient effect).
Dehydration: Administer with isotonic crystalloids.
Inotropic effect.
Vasodilation: Do not administer too fast! Dose: 4–5 mL/kg

Hypotonic Crystalloids

Water loss treatment.
Often with dextrose to increase tonicity to avoid RBC damage.
Water shift from extracellular to intracellular space.
For hypernatremia treatment only.
No boluses.

Colloids

Macro-molecules suspended in crystalloid solutions (proteins, sugars, starches).
Longer lasting in intravascular space (hours).
Natural: blood products (plasma, whole blood, albumin).
Synthetic: Dextrans, hydroxyethyl starches (HESs).

Resuscitation (Hypovolemia)

Rapid intravascular volume expansion.
Draws water from interstitial and intracellular spaces (osmotic gradient) into intravascular space.

Fluids Can Be Helpful For...

Resuscitation (e.g., hypertonic saline, Hartmann's solution, blood products) to correct intravascular volume deficit.
Replacement (e.g., Hartmann's solution) to replace lost body fluids, electrolytes not compensated by oral intake
Maintenance (e.g., hypotonic crystalloids) to meet daily basal requirements for water, electrolytes, and glucose.

Treatment Plan for Hypovolemia (Resuscitation)

Rapid correction of intravascular deficits.
Buffered isotonic crystalloids (boluses over 15–30 min).
Only 25% remains in intravascular space after 30–60 min.
Dog: 15–20 mL/kg; Cat: 5–10 mL/kg.
Monitor closely, and if hemorrhage, consider blood products.
+/- hypertonic crystalloids. Dog: 4-6 mL/kg; Cat: 1-4 mL/kg.
+/- colloids. Dog: 2.5–5 mL/kg; Max amount: Dogs: 20 ml/kg; Cats: 10–15ml/kg.

Treatment Plan For Dehydration

Balanced isotonic crystalloids (IV or IO).
PO administration (voluntary oral intake or orogastric tube) if dehydration is not severe.
Calculate total fluid deficit.
Administer over 12–24 hours.
Continuous monitoring.
If recovery is achieved, continue oral administration if possible.

Treatment Plan if Hypovolemia & Dehydration

Address hypovolemia first.
Then rehydration (account for ongoing losses).
Add maintenance rate.

Treatment Plan for Maintenance

Hypotonic crystalloids (or balance isotonic crystalloids + K & dextrose).
Daily fluid requirement for hydrated patients unable to maintain homeostasis through oral ingestion.
Dog: 60 mL/kg/day (equivalent to 2 mL/kg/hr).
Cat: 40 mL/kg/day.
Paediatric patients: 3 x adult dose, 2.5 x adult dose

Fluid Approach in Anaesthesia

Previous approach: Large volume crystalloids (10 ml/kg/hr).
Restricted approach: Fluid administration based on patient needs (3ml/kg/hr (cats), 5ml/kg/hr (dogs)), considering normal cardiac & renal function.

Goals of Fluid Therapy During Anaesthesia

Oxygen delivery & tissue perfusion
Macro circulation
Microcirculation
Maintaining/correcting electrolyte composition & acid-base balance.
Stabilizing before anaesthesia
Monitoring.
Maintaining adequate blood pressure.

Infusion Equipment

Intravenous cannula
Intraosseous catheters
Fluids of choice
Giving set
Fluid pump/syringe driver
Pressure bag

Giving Sets for Free Flow Fluid Administration

20 drops/mL (adult set), 60 drops/ml (pediatric set).
Micro dripper: Delivers 60 drops per mL.
Gravity assisted delivery.
Risk of fluid overload and air embolism.

Fluid Rate Calculations Using a Giving Set

Required information: Giving set type, patient body mass, desired administration rate.
Calculation steps: 1. ml/kg/hr * body mass (kg) = mL/hr; 2. mL/hr / 60 = mL/min; 3. mL/min / 60 = mL/sec; 4. mL/sec * drops/mL = drops/sec

Infusion Pumps & Syringe Drivers

VTBI (Volume To Be Infused)-- Total volume of fluid you want to deliver.
VI (Volume Infused)-- Amount of fluid already in the pump.
Improve accuracy & consistency.
Boluses administration.
Auditory alarms (e.g., air bubbles).

Fluid Therapy Monitoring

Monitor clinical signs, heart rate, arterial pressure, pulse rate, capillary refill time, mucous membrane colour, core-peripheral temperature gradient, respiratory rate, mental status, urine output, skin turgor, body weight, and signs of edema.
Monitor laboratory findings (urine specific gravity, hematocrit, total protein, lactate, and electrolytes).

Fluid Therapy Complications

Fluid overload/intolerance: Interstitial edema & tri-cavitary effusion.
Electrolyte & acid-base imbalances.
Dilution coagulopathy.

Fluid Overload Therapy

If patient has increased body weight, mild to localized peripheral edema, respiratory distress, or dysfunction in the renal, hepatic, or gastrointestinal system.
Discontinue IV fluids and increase patient mobility.
Provide oxygen support, administer a diuretic.
Remove pleural fluid (thoracentesis) or abdominal fluid (abdominocentesis).
Consult for hemodialysis.
Consider discontinuing ACE inhibitors and ARBs to improve GFR.

References (partial)

Authors, year, and names of the 2024 AAHA Fluid Therapy Guidelines for Dogs and Cats.
Various sources for fluid therapy, dehydration, and hypovolemia in veterinary medicine.

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Description

Test your knowledge on the characteristics and implications of hypovolaemia and dehydration. This quiz includes questions on laboratory tests, physical examination findings, and the effects of fluid volume changes. Perfect for medical students and healthcare professionals.