Fluid Therapy 1: Patient Assessment

What is hypovolaemia?

• fluid lost quickly from intravascular space

• results in hypoperfusion

• results in inadequate delivery of oxygen and nutrients to cells

• causes shock

hypoperfusion

inadequate tissue perfusion

What is dehydration?

fluid lost slowly from extravascular space (in cells)

What are the physiological consequences of hypovolaemia?

1. blood loss

2. reduced pre-load

3. reduced stroke vol

4. decreased CO

5. vasoconstriction & tachycardia

   1. maintenance of blood pressure to vital organs

   2. changes in mucous membrane colour (pale) and CRT

CRT

capillary refill time

What components should you assess a patient for to get information about their intravascular volume status (for hypovolaemia)?

• HR

• pulse quality

• mucous membrnae colour

• CRT

• BP

• mentation

• temp

Normal HR for dogs (bpm)

70-140

HR in mild shock (compensatory) (bpm)

130-150

HR in moderate shock (bpm)

150-170

HR in severe shock (decompensatory) (bpm)

170-220

What is the normal colour of mucous membranes?

pink

What is the colour of the mucous membranes in an animal with mild shock?

normal to pinker

What is the colour of the mucous membranes in an animal with moderate shock?

pale pink

What is the colour of the mucous membranes in an animal with severe shock (decompensatory)?

pale pink - white

What is the normal CRT?

<2sec

What is the CRT of an animal with mild shock (compensatory)?

<1sec

What is the CRT of an animal with moderate shock?

2sec

What is the CRT of an animal with severe shock (decompensatory)?

>2sec

What the pulse quality of a patient with mild shock (compensatory) like?

bounding

What is the pulse quality of a patient with moderate shock like?

weak

What is the pulse quality of a patient with severe shock (decompensatory)?

very weak

What is the normal systolic BP (mmHg)?

>90

What is the systolic BP (mmHg) for a patient in mild shock (compensatory)?

>90

What is the systolic BP (mmHg) for a patient in moderate shock?

>90

What is the systolic BP (mmHg) for a patient in severe shock (decompensatory)?

>90

At what level of shock does mentation begin to get obtunded?

moderate

What components of your triage/physical exam will give you information about the patient’s extravascular volume status (for dehydration)?

• moistness of mucous membranes

• skin turgor

• weight

• globe position

• urine output

• severe dehydration → signs of hypovolaemia

How does dehydration impact urine output?

more concentrated = stronger colour

What can complicate patient assessment of hypovolaemia?

species variation (e.g. blue tongue of chow chow, cold ambient temp)

What are the physical exam findings of a patient with <5% body weight dehydration?

• not clinically detectable

• suspected from clinical history

What are the physical exam findings of a patient with 5-6% body weight dehydration?

• tacky mucous membranes

• minor delay in skin tent return

What are the physical exam findings of a patient with 6-8% body weight dehydration?

• dry mucous membranes

• mild to moderate delay in skin tent return

What are the physical exam findings of a patient with 8-10% body weight dehydration?

• dry mucous membranes

• marked delay in skin tent return

• retracted globes within orbits

What are the physical exam findings of a patient with >10-12% body weight dehydration?

• dry mucous membranes

• persistent skin tent

• dull corneas

• retracted globes within orbits

• evidence of hypovolaemia

What are the physical exam findings of a patient with >12% body weight dehydration?

• hypovolaemic shock

• death

At what %dehydration would you see hypovolaemic shock or death?

>12%

What can complicate patient assessment for dehydration?

• hypersalivation

• amount of subcut fat

• skin‘s collagen content

What parameters from haematology, biochemistry and urinalysis may be affected by a patient’s hydration status?

• PCV/TS

• urea & creatinine

• USG

PCV

packed cell volume

TS

total solids

USG

urine specific gravity

What type of assessment does patient assessment of dehydration/hypovolaemia need to be?

global assessment

What’s meant by a ‘global assessment’?

no single physical exam finding/clinicopathological parameter should be interpreted in isolation

Are patients with hypovolaemia ever stable?

NO

How do you administer fluids to a patient with hypovolaemia?

• rapid fluid resuscitation of patient

• large boluses of fluid (large volumes of fluid over a short period of time)

How do you administer fluids to a patient without hypovolaemia?

• check for extravascular fluid losses

• if present these should be corrected slowly (after 24/48hr time period)

• a 20kg, 1yr 6m FN Labrador Retriever

• spayed this morning

• 3hrs following surgery, your nurse notices blood dripping from the patient’s abdominal incision

Does this patient need fluids?

maybe

• a 20kg, 1yr 6m FN Labrador Retriever

• spayed this morning

• 3hrs following surgery, your nurse notices blood dripping from the patient’s abdominal incision

What will you assess Misty for first: dehydration or hypovolaemia?

hypovolaemia

• a 20kg, 1yr 6m FN Labrador Retriever

• spayed this morning

• 3hrs following surgery, your nurse notices blood dripping from the patient’s abdominal incision

You assess Misty for Hypovolaemia, and you find that she is QAR, has a HR of 150bpm, pale mucous membranes, a CRT of 2 seconds and reduced pulse quality. Is misty hypovolaemic?

YES

QAR

quiet alert responsive

• a 20kg, 1yr 6m FN Labrador Retriever

• spayed this morning

• 3hrs following surgery, your nurse notices blood dripping from the patient’s abdominal incision

You assess Misty for Hypovolaemia, and you find that she is QAR, has a HR of 150bpm, pale mucous membranes, a CRT of 2 seconds and reduced pulse quality.

How can fluids be used to stabilise misty?

give a rapid fluid bolus to restore the patient’s intravascular fluid volume

• a 20kg, 1yr 6m FN Labrador Retriever

• spayed this morning

• 3hrs following surgery, your nurse notices blood dripping from the patient’s abdominal incision

You assess Misty for dehydration, and you find that her mucous membranes are moist, she has no delay in skin tent and there is no change in her globe position within the orbit.

Is misty dehyrdated?

no

fluid requirement (ml) =

extravascular fluid deficit (ml) + maintenance requirements (ml) + ongoing loss (ml)

What’s an example of an ‘ongoing loss’

vomiting/diarrhoea

extravascular fluid deficit (ml) =

%dehydration x body weight (kg) x 10

maintenance requirements

rate of fluid needed to maintain a neutral fluid balance

What do ‘maintenance requirements’ replace losses from?

• urination

• respiration

• sweating

• defecation

What is the value of the maintenance requirement?

2ml/kg/hr

What do ‘maintenance requirements’ vary according to?

• age

• environment

• exercise

• diet

• disease

How do you work out ongoing losses?

• sometimes measured

• visually estimated

hypervolaemia

aka fluid overload, medical condition where there’s too much fluid in the body

shock

a state of cellular and tissue hypoxia, most commonly caused by hypoperfusion

oncotic pressure

form of osmotic pressure induced by proteins (e.g. albumin) in a blood vessel’s plasma (blood/liquid)

normovolaemia

normal blood volume