Hydration

body water content

• 60% of body weight in adults

• 80% of body weight in neonates

body water intracellular

66%

body water interstitial (around the cells)

28%

body water in blood vessels

5%

signs of continues loss of body water

• loss of moisture from the skin (results in tenting)

• sunken appearance

• drying of mucous membranes

Normovolemia

• adequate body water volume or normal hydration

• maintained by ensuring input is equal to output

measurable losses

• urination

• other secretory functions- sweat, tears , saliva, feces, vaginal secretions, gland seceretions

non measurable losses

• evaporation from the body surface (skin, eye , mucus membranes)

• during respirations

body water is lost when

• high ambient temp

• dry arid environment

• increased exercise

• fever

• open body cavities

• certain pathological processes (vomit, diarrhea, diuresis, bleeding)

adult water maintenance

60ml/kg//day

pediatric maintenance

120ml/kg/day (2x adult)

maintenance volume

the volume of water that we require for daily survival

pathology occurs when

1. excessive water loss

2. lack in intake

3. excessive intake

hypovolemia

dehydration

hypervolemia

overhydration

overhydration

• aka water intoxication

• uncommon to rare

overhydration causes

• iatrogenic - (excessive fluid therapy)

• endocrine problems

• behavioral overconsumption

overhydration pathological changes

• increased volume in blood vessels

• decreases oncotic and osmotic pressures in blood vessels

• fluid leaves blood vessels and enters interstitial space

• decreases osmotic pressure in the interstitial space

• fluid enters the cells

overhydration pathological effects

• increased demand on the heart (increased water added to blood vessels increases BP)

diuresis

increased urine production

Pulmonary hypertension

• fluid enters in lungs and pleural space

• due a combination of high BP and decreased oncotic pressures in the blood vessels

• if heart can’t push fluid through fast enough there will be increases pressure in pulmonary vessels;s, if significant may force fluid into lungs and pleural space

pulmonary edema

increased fluid in the lungs

Pleural effusion

fluid in the pleural space (around the lungs)

cerebral edema and brain compression

• increased water causes the concentration of Na to drop and this decreases the osmotic pressure in the interstitial space

• water moves from extracellular space into intracellular causing the cells to swell

• swelling of cells causes cerebral edema and compression

Clinical signs of cerebral edema

• increased HR, BP, RR

• dyspnea- increased resp effort

• increased and dilute urine

• neurological signs (headache, behavioural changes,ataxia, tremors, blindness, seizures, coma)

Patients at risk for overhydration

• heart failure

• kidney failure

• end stage liver failure

• small animals

treating overhydration

• stop fluids

• diuretics - drugs that promote urine production

• correct any underlying endocrine condition

dehydration

the body loses more water than it takes in

causes of dehydration

• not drinking enough

• any form of water deprivation

• animals forced to “drink snow”

• animals in drought conditions

increased losses

• lactating animals require more water

• animals that are athletes

• hot weather, hyperthermia, prolonged fever

• vomit, diarrhea

• renal losses

• iatrogenic( diuretics)

• blood loss

• small animals

diagnosing dehydration

1. history

2. PE finding

3. diagnostic tests

history

• very important for determining cause

• owner can comment on amount and duration of losses

• owner to comment on availability and water intake

PE findings

• assessing hydration is part of every PE

• hospitalized patients should be evaluates at least once daily

• minimum exam includes

  • weight changes

  • CRT

  • MM texture

  • skin tent

  • HR

diagnostic tests

• increased pack cell volume

• increased total proteins

• increased urine concentration

degree of dehydration

clinical signs that are noted with diagnostic test results

<3% dehydrated

• subclinical

• no changes on PE

• long term may later production and performance

• changes appear on diagnostic tests

• treatment - drink water

3-5% dehydrated

• mild

• often subclinical

• if clinical- lethargic, maybe tacky MM or weight change

• changes on diagnostic testing

• diagnosis often based on history

• treatment oral fluids

5-8% dehydrated

• moderate

• weight loss, lethargic,prolonged CRT, tacky MM, mild skin tent,

• clearly seen on diagnostics

• treatment- IV fluids

8-10% dehydrated

• marked

• weight loss, lethargic to depressed, prolonged CRT, tacky to dry MM, skin tent, mild tachycardia,may look sunken

• clearly seen on diagnostics

• treatment - IV fluids and correct electrolytes

10-12% dehydrated

• severe

• significant weight loss, depressed, prolonged CRT, dry MM, skin tent, sunken eyes, tachycardia, cool extremities

• diagnostic tests show other changes to electrolytes and other organ functions

• treatment Iv fluids and organ support

>12% dehydrated

• Moribund

• this animal is in shock and dying

• treatment shock fluids, possible CPR

method 2 calculation based on body weight loss

• works best for animal is hospitalised or been seen within days

• calculation should always match up with clinical signs

deficit volume

• teh volume of fluids that’s lacking in a dehydrated patient

• needs to be replaced to return to normal

Pathology associated with dehydration

• danadge is related to decreased blood pressure that causes decreased tissue perfusion. tissue cells receive less oxygen and nutrient delivery, decreased removal of metabolic waste products

Hypernatremia

increased Na concentration causes body water to shift compartments