Week 7 - Fluids, Weight loss/Failure to thrive

What is the difference between a treatment and therapy?

- Treatment = Something you do

- Therapy = Something you do that is beneficial

- We hope all our treatment are therapies, but that is not always the case

What are the most common uses of fluid therapy?

- Correct dehydration

- Correct electrolyte and acid-base imbalances (replacement, diuresis, increase uptake by the liver or other tissues)

- Increase circulatory volume, cardiac output, and peripheral perfusion

- Increase urination

- Increase GI, pulmonary and other secretions

- Vehicle for other treatments

- Wash out or dilute other substances

- Maintenance

What are "everyday challenges" to the aqueous environment of the body?

- Loss of aqueous and electrolyte components by excretion of body fluids (ocular, nasal, and oral discharges, urine, feces, sweat, and milk)

- Evaporative losses of water through body surfaces and the respiratory tract

How are everyday fluid losses normally replaced?

- Ingestion or imbibition of water and feed (Water in feed is especially important in cats and animals on fresh pasture).

How can everyday fluid losses vary under abnormal conditions?

- Losses can accelerate (diarrhea, polyuria, choke, etc.)

- New routes of loss can form (draining wounds)

- Intake can diminish

Non-excretable body fluid exists in two discrete compartments. What are they and what percentage of fluid is in each?

- Intracellular fluid (ICF - 60%)

- Extracellular fluid (ECF - 40%) (The compartment we worry about)

Extracellular fluid can be further subdivided into what two compartments?

(1) Intravascular

(2) Extravascular/interstitial

+/- (3) Transcellular water (Body fluids such as glomerular filtrate and intestinal luminal fluid that are still being modified by the body prior to ultimate excretion of the remainder)

Describe the flow of water and electrolytes between intravascular and extravascular extracellular fluid compartments.

- Fluids and electrolytes move relatively freely between the IV-ECF and EV-ECF.

Describe the balance of fluid and protein between the ICF and ECF

- Albumin and some other protein molecules move with greater difficulty and tend to remain in the IV-ECF -> These protein molecules create an osmotic (plasma oncotic) force that tends to draw fluid into the vascular space from the interstitium.

- As the intravascular fluid creates pressure against the blood vessel walls, hydrostatic pressure causes fluid to exude into the interstitium.

- The balance of hydrostatic versus osmotic pressure dictates the ratio of fluid in these two pools of ECF.

What is a good estimator of the amount of ECF in large animals?

- 0.3 X BW

What is a good estimator of the amount of ECF in neonate large animals?

- 0.5 X BW

What is a good estimator of the amount of ECF in small animals?

- 0.4 X BW

What is a good estimator of the amount of ECF in neonate small animals?

- 0.6 X BW

Estimates of ECF fluid quantities are over or under estimates?

- Overestimates (anesthesiologists will provide lower numbers)

What percent of BW is IV-ECF?

- 8% of body weight used dogs and neonatal large animals

- 6 to 7% is probably more accurate in adult large animals (and maybe cats)

Most fluid therapy plans can be divided into what two phases? Briefly describe the two phases.

1) Replacement (Replacement is used to correct deficits present on initial evaluation)

2) Maintenance (Maintenance is used to keep the animal within certain homeostatic parameters for a longer period of time)

When we determine a rationale for administration of fluids, we create a fluid therapy plan consisting of what 4 components?

1) Type of fluid

2) Rate of administration

3) Route of administration

4) Schedule and type of monitoring

What are the major types of fluids?

1) Colloids

2) Crystalloids

3) Blood/blood replacers

4) Energy supplements

What are the most common crystalloid fluids?

- Norm-R

- LRS

- Normal Saline (0.9%)

What are crystalloids? What is their purpose?

- They are essentially salt water with different salts in them

- They are used to replace water and correct electrolyte and acid/base disturbances

What are the types of colloids?

- Plasma

- Protein

- Synthetic colloids

What are the functions of colloid fluids?

- Provide oncotic pressure via larger molecules (i.e., proteins) to maintain fluids in the intravascular space

- Replace lost protein

- Supply deficient/specific immunoglobulins

- Increase IV-ECF oncotic pressure

What are the uses of blood or blood replacers?

- Same benefits as colloids (blood has protein in it) but also increased oxygen carrying capacity of blood

What are the types of blood or blood replacers?

- Whole blood

- Plasma

- Purified hemoglobin derivatives

What are the types of energy supplements?

- Lipids

- Glucose

- Amino acids

Why types of fluids are suited for maintenance?

- Crystalloids

- Energy supplements

What is the normal plasma osmolality?

~ 300 (most crystalloids are around this number)

During the Replacement phase, our goal is to correct hydration deficits, usually over about ____________, although newer trends are towards less aggressive, goal-oriented replacement.

- 4hours

What is the rule of thumb for a shock dose?

- Up to a Blood Volume may be given over 20 minutes

What is a typical shock dose for small animals?

- Give a quarter of 60-90 mL/kg, repeat PRN

What percent of body weight is water?

- 60%

What percentage of body weight is blood volume?

- 8% dogs

- 7% cats

- 6% LA

True or false: Patients in hypovolemic shock will always be clinically dehydrated.

- False

What is a convenient and direct technique to judge dehydration?

- By the percentage of body weight lost

- Note: While weighing a patient would offer the most direct method of measuring this, pre-dehydration weights are not always available, and other factors such as fat stores and GI fill affect body weight.

What are some common clinical pathology measurements used to aid in the diagnosis of dehydration (or in some cases, of shock)?

- BUN and creatinine

- PCV and TP

- Lactate

Dehydration under __________% is usually subclinical, except in neonates, meaning the physical exam will reveal no abnormalities.

- 6

Describe the following characteristics associated with mild dehydration:

A. Percent of body weight loss

B. Skin tent

C. Mucous membranes

D. Eyes

E. Other

A. 6%

B. 1-3 seconds

C. Moist to slightly tacky

D. Normal

E. Decreased urine production

Describe the following characteristics associated with moderate dehydration:

A. Percent of body weight loss

B. Skin tent

C. Mucous membranes

D. Eyes

E. Other

A. 8%

B. 3-5 seconds

C. Tacky

D. Normal

E. Weaker pulse

Describe the following characteristics associated with severe dehydration:

A. Percent of body weight loss

B. Skin tent

C. Mucous membranes

D. Eyes

E. Other

A. 10%

B. 5+ seconds

C. Dry

D. Sunken

E. Poor jugular fill

Describe the following characteristics associated with very severe dehydration:

A. Percent of body weight loss

B. Skin tent

C. Mucous membranes

D. Eyes

E. Other

A. 12%

B. Forever

C. Dry, pale, cold

D. Sunken

E. +/- absent pulse

For replacement of dehydration, what is the quantity and duration of administration?

- The calculated percent of Body weight is given, usually over 2-4 hours, usually as crystalloids

What is the quantity and duration of maintenance fluids to deliver?

- The amount administered should roughly equate the amount used or lost over the same period of time.

- We are replacing this over a large period of time (L/day) not a small one (drops/second), whether we do it in drips or boluses.

What is an appropriate maintenance fluid plan over 24 hours for...

A. Adult horses

B. Adult cattle

C. Neonatal large animals

D. Adult small animals

E. Neonatal small animals

A. Adult horses require: 4-6% of BW (40-60 ml/kg/d or about 2 ml/kg/h)

B. Adult cattle require: 7-10% of BW (70-100 ml/kg/d or about 3-4 ml/kg/h)

C. Neonatal large animals: 10% of BW (100 ml/kg/d or 4 ml/kg/h)

D. Adult small animals: 5-8% of BW (50-80 ml/kg/d or about 2-3 ml/kg/h; cats lower end, dogs higher)

E. Neonatal small animals:10% of BW (same as LA neonate)

What are the benefits and limitations of oral fluid administration?

- Benefits: Cheapest, non-sterile, requires the least medical equipment, allows physiologic control of absorption

- Limitations: Require a functional, moving gut (cats are not great oral re-hydrators with water)

What are the benefits and limitations of SubQ fluid administration?

- Benefits: Bypasses gut and well absorbed in most patients

- Limits: Requires sterile procedures and some medical equipment, and limited by amount of subcutis, aesthetic considerations (Poorly absorbed in very dehydrated patients and should not give hypertonic fluids by this route)

What are the benefits and limitations of IV fluid administration?

- Benefits: Most rapid correction

- Limits: Requires sterile procedures, medical equipment and training (must be careful with certain electrolytes and fluids of non-physiologic tonicity)

What are the benefits and limitations of IO fluid administration?

- Benefits: Useful for neonates or other small animals with poor venous access

- Otherwise similar advantages and disadvantages as IV fluids.

What are the benefits and limitations of IP fluid administration?

- Similar to subcutaneous, except that absorption is less restricted in severely dehydrated patients and the need for sterility is greater.

- Rarely used

What can be used to assess the fluid administration plan to avoid over-hydration/over-treatment and judge efficacy of the plan?

1) Body weight

2) Physical determinants: heart rate, mucous membranes, skin turgor, eye luster.

3) Central Venous Pressure

4) PCV/TP; measures of azotemia, measures of underperfusion (lactate)

5) Urine volume

6) Evidence of pulmonary, cerebral or peripheral edema

In general, when can fluids be discontinued?

- When the animal is getting enough fluid from other sources to maintain itself

What is the definition of failure to thrive?

- Non- specific sign characterized by failure to gain weight/persistent weight loss

Why is BCS sometimes difficult to assess visually?

- Thick hair coats

What are major causes of weight loss and failure to thrive?

1) Inadequate intake

2) Malabsorption

3) Increased metabolic demands

What are causes of inadequate intake?

- Inability/reluctance to access food

- Inadequate diet (Amount/quantity)

- Competition

- Hierarchy

- Inadequate animal:feed ratio

What are some causes of an inability/reluctance to access food?

- Palatability

- Poor dentition (Impaired digestion)

- Pain (Dentition, trauma)

- Neurological conditions (Prehension, mastication, swallowing)

- Musculoskeletal conditions (Weakness)

What are some causes of malabsorption?

- Poor definition

- GIT disease (small intestine, large intestine; Proliferative diseases (IBD, neoplasia), Motility disorders, Partial obstructions, Lactase deficiency in neonates)

- Endocrine disorders

- Parasitism

What are some physiologic causes of increased metabolic demands?

- Environmental conditions

- Exercise

- Pregnancy

- Lactation

What are some pathophysiologic causes of increased metabolic demands?

- Chronic inflammation (TNF alpha/cachectin)

- Neoplasia (TNF alpha/cachectin)

- Kidney disease (chronic inflammation essentially)

- Heart disease

- Respiratory disease

What is the function of TNF alpha/cachectin?

- Will lead to reduced appetite and induce catabolic state/weight loss (animal can lose 50-100 lb in a one week period - LA)

What are some important history questions to ask/consider in a patient with weight loss or failure to thrive?

- Diet (amount, quality, changes)

- Management (Travel, exercise, dental care)

- Deworming (Frequency, product, dose)

- Housing (alone, herd)

- Known conditions, concerns (Examples: PPID, EMD, Neoplasia, anything that results in a catabolic state which is difficult to reverse)

- Duration

When assessing the BCS of an animal with weight loss or failure to thrive, what is it important to note the difference between?

- Weight loss vs. muscle wasting

What are the "basics" to begin evaluating in a patient with weight loss/failure to thrive when you are unsure where to start?

- Dentition

- Nutrition

- Parasitism