Water deprivation--Na ion toxicosis

Question 1

Sources?

Answer 1

• Feeding brine, whey, or garbage
• Ingestion of salt-licks or ice-melts
• Drinking water might contain salt
• All factors that cause excess Na and water deprivation
  
  • Over crowding
  • Frozen water
  • Unpalatable (medicated) water
  • Lack of water

Question 2

T/F: Salt taste is attractive to animals and has a mild irritant effect on mucous membranes

Answer 2

TRUE

Question 3

What is the normal level of NaCl in feed?

Answer 3

About 0.5-1.0%

Question 4

What are the acute oral lethal doses of salt?

Answer 4

• Horses, cattle, swine: ~2.2g/kg
• Sheep: 6g/kg
• Dogs: 4g/kg (depending on water intake)

Question 5

T/F: Animals can only tolerate up to 10% salt in feed, even with free access to water

Answer 5

FALSE–animals can tolerate more than 10% salt in feed if they have free access to water

Question 6

Which species are the most susceptible to salt poisoning?

Answer 6

Pigs, cattle, and poultry; dogs are less susceptible

Question 7

Salt is rapidly absorbed from the ____ and is distributed ____.

Answer 7

Salt is rapidly absorbed from the GI tract and is distributed all over the body.

Question 8

Does sodium enter the brain? If so, how?

Answer 8

Yes–sodium enters the brain by passive diffusion and is removed by active transport

Question 9

What happens to excess absorbed sodium?

When might this not occur, and what will be the result?

Answer 9

• The excess of absorbed sodium following large dietary intake is rapidly excreted in urine as long as there is enough water
• Excess sodium (and water deprivation) results in hypertonicity of the blood and toxicosis

Question 10

What are the normal Na levels in plasma and CSF?

Answer 10

Plasma = 135-145 mEq/L

CSF = 130-140 mEq/L

Question 11

Restricted water intake and dehydration increases Na levels in plasma and CSF to what?

Answer 11

Plasma = 150-190 mEq/L

CSF = 145-185 mEq/L

Question 12

What does high Na in the brain inhibit?

Answer 12

Inhibits anaerobic glycolysis –> lack of energy necessary for active transport of Na

Question 13

What occurs when sodium is trapped in the brain?

Answer 13

Na trapped in the brain attracts water b/c the osmotic gradient–> cerebral edema

Question 14

General clinical signs?

Answer 14

• Early constipation and thirst
• Vomiting, PU, metabolic acidosis
• Intermittent convulsive seizures
  
  • Lasts from 0.5 to 2-3 min
  • Interrupted by other signs
  • Not elicited by external stimuli
• Circling, pivoting, head-pressing
• Blindness and deafness
• Inability to eat and drink or even recognize the feed or water

Question 15

Clinical signs in poultry?

Answer 15

Poultry only show depression, ascites, and collapse

Question 16

Gross lesions?

Answer 16

• Gastric congestion or inflammation with pinpoint ulcers
• Fluid in body cavities and organ edema
• Prominent cerebral edema

Question 17

Histopathological lesions?

Answer 17

Eosinophilic meningoencephalitis (filling of cerebral and meningeal perivascular spaces w/ eosinophils) is pathognomonic in pigs only, if the animal dies early

Question 18

Laboratory diagnosis?

Answer 18

• Serum and CSF (or ocular fluid) Na concentrations are 160 mEq/L or more
• Brain Na concentrations above 2000ppm support diagnosis
• Salt in feed

Question 19

Diagnosis

Answer 19

History, encephalitic signs, lesions, and lab diagnosis

Question 20

DDx?

Answer 20

• Encephalitic diseases
  
  • Trauma
  • Tumor
  • Heat stroke
  • Viral encephalomyelitic conditions
• Chlorinated hydrocarbon insecticides
• Roxarsone
• Pseudorabies

Question 21

Treatment?

Answer 21

• Giving small amounts of fresh water (0.5% of body wt.) gradually over 2-3 days, if the animal is able to drink
• IV fluids (5% dextrose) and furosemide in small animals
• Anticonvulsants in small animals

Question 22

T/F: Giving water in large amounts as treatment may kill the animal by aggravating cerebral edema

Answer 22

TRUE

Question 23

Prognosis?

Answer 23

Poor

Mortality rate is ~50%