Dehydration

Dehydration



Basic Information image



Definition


A state in which fluid losses (apparent losses as well as insensible losses combined) outpace fluid intake



Synonym(s)




• Hypovolemia


• Negative fluid balance



Epidemiology



Species, Age, Sex


Foals are particularly at risk because of their high body water content and surface-to-volume ratio.



Contagion and Zoonosis


Dehydration is not contagious itself; however, some of the diseases that cause it may be communicable to others (eg, colitis caused by Salmonella spp. or rabid encephalitis).



Geography and Seasonality




• Cold weather may limit access to water because of freezing of water sources or reduced intake because of the decreased palatability of cold water.


• Hot weather may increase fluid and electrolyte losses through sweat.



Associated Conditions and Disorders


Diseases that increase fluid losses in excess of the horse’s ability to take in fluids, toxins that increase vascular leakage, disruption of the protective dermis by burn injury, as well as disorders that inhibit the horse’s ability to drink and swallow may cause dehydration.



Clinical Presentation



Disease Forms/Subtypes




• Hypertonic dehydration


• Isotonic dehydration


• Hypotonic dehydration



History, Chief Complaint


Variable because of the diverse etiology



Physical Exam Findings




• Depression; lethargy; tachycardia; reduced pulse quality; increased duration of skin tent test; dry mucous membranes; increased capillary refill time (CRT); cool extremities; mucus-covered fecal balls; or dry, scant feces (Figures 1 and 2)


• Weight loss is the gold standard for determining the percent of body weight lost to dehydration.


• The approximate percent dehydration can be estimated from physical examination findings as follows:


• Heart rate 40 to 60 beats/min, CRT <2: approximately 6% dehydration

• Heart rate 61 to 80 beats/min, CRT <3: approximately 8% dehydration

• Heart rate 81 to 100 beats/min, CRT <4: approximately 10% dehydration

• Heart rate 101+ beats/min, CRT >4, packed cell volume (PCV) >50%: approximately >10% dehydration; the horse is in hypovolemic shock

image

FIGURE 1 Skin tent test for dehydration using the upper eyelid of the horse. This test may also be performed on the neck dorsal to the cervical vertebrae and cranial to the shoulder.


image

FIGURE 2 Prolonged skin tent test of >4 seconds. Based on the complete physical examination, this horse was more than 10% dehydrated.



Etiology and Pathophysiology




• Pathophysiology: Dehydration results in a reduction of relative circulating volume. Decreased tissue perfusion reduces oxygen delivery to the tissues, increasing anaerobic metabolism and reducing tissue pH through acid accumulation and lactate production.


• Reduced intake


• Environmental: Weather, lack of available water

• Mechanical obstruction: Jaw fracture, pharyngeal injury, choking

• Neurologic disorders causing dysphagia
< div class='tao-gold-member'>

Related posts:

  1. Codocytes
  2. Rhabdomyolysis
  3. Albumin
  4. Protein-Losing Nephropathy

Stay updated, free articles. Join our Telegram channel
Tags:
Jul 24, 2016 | Posted by in SMALL ANIMAL | Comments Off on Dehydration

Full access? Get Clinical Tree
Get Clinical Tree app for offline access