Body water

concept of milliequivalents

osmosis and osmolarity

role in kidney in water and salt regulation

acid-base regulation

60% of BW mature animals

70-75% BW in young

IC fluid=40%

EC fluid=20%

plasma water=5% BW

Interstitial fluid=15% BW

transcellular fluid=1-6% BW

65 ml/kg/day

(50-70 ml/kg/day)

moles=actual wt (g)/mol wt

mmol=actual wt (mg)/mol wt

1 Eq=1 mole (1 mEq=1 mmol)

How many mg is in 1 mEq of NaCl? mw=58.5

1 mEq=1 mmol=X mg/58.5

X=58.5 mg

Eq wt of CaCl2=111 mw/2=55.5

mEq CaCl2=actual wt in mg/Eq wt

How many mg of CaCl2 are in 1 mEq of CaCl2?

1 mEq=x mg/Eq wt=x mg/55.5

x=55.5 mg

most electrolyte concentrations of plasma are expressed as mEq/L

Total plasma concentraion of cationsin mEq/L must be equal to that of anions to maintain electroneutrality

Plasma calcium and phosphorus concentrations are usually measured as mg% or mM

Fluid compartments are separated by semipermeable membranes

allow free passage of water but restrict particles

water moves toward compartment with higher number of particles

describe properties related to number of particles in solution

mOsm/L

isotonic solution=300 mOsm/L

isotonic solution of NaCl in mM=150 mOsm/L

isotonic solution of glucose in mM=300 mOsm/L

isotonic solution of Na lactate in mM=150 mOsm/L

mM=wt (mg)/mol. wt x 1000/V (ml)

M=mol/L

mM=mmol/L

Main purpose is to correct dehydration and/or electrolytes imbalances

use fluids correct acid-base disturbances and K+ imbalances

Routes of administration

Products for fluid therapy

dehydration

acid-base disturbances and/or electrolytes imbalances

nutrional problems

loss of body fluids, esp plasma

causes and treatment-amount to be used

role of electrolytes on water and acid-base balances

role of intermediary metabolism on hydration and acid-base balances

basis for fluid therapy institution:accurate diagnosis

Hypertonic

isotonic

hypotonic

Lack of intake:

1. lack of water source

2. disorders of buccal cavity, pharynx

3. CNS disturbances; paralysis

Respiratory loss of water leads to hypertonic dehydration

polyuria: diabetes, nephrosis, hypoadrenocorticism, diuretics, large wounds

profuse sweating in horses

vomiting/diarrhea

Third space loss: fluid retained in a cavity

Dehydration treatment

iso/hypotonic

administer fluid with or without electrolytes

treatment of third space loss

increased Na+ in ECF-> water retention

Changes in [K+] result in changes in acid-base balance

Changes in [H+] result in changes in [K+]

-increased K+ in plasma->increased K+, decreased H+ in urine

acidemia->hyperkalemia

decreased K+ in plasma

Alkalemia leads to hypokalemia

increased CHO intake or decreased utilization->hyperglycemia->glucosuria->polyuria->dehydration

increased CHO intake (grain overload)->increased lactic acid->acidosis

decreased CHO utilization-> increased gluconeogenesis->ketoacidosis

Amount of fluid to be used

based on:

body water maintenance (sensible loss+ insensible loss)

replacement of deficit

replacement of ongoing loss

Body water turnover: 50-70 ml/kg/d

Average 65 ml/kg/d

based on body weight

mild

a history of fluid loss, but no significant signs of dehydration

no replacement needed

moderate

leathery skin

dogs, cats, calves, foals

when skin is pinched into a tented fold->peaks->slowly return to normal

in larger species pinch neck or dorsal eyelid

decrease skin elasticity also seen in aging, cachexia

obese patients

dull haircoat

dry mucous membranes

can be caused by open-mouth breathing

severe

skin lacks pliability

in dogs and cats skin pinch->peaks and STAY

dry mucous membranes and tongue

soft, sunken eyeballs into orbit (enophthalmus)

cold limbs

capillary refill time >3 s (normal <2s)

extremely severe

all signs seen with 8-10% dehydration

circulatory collapse-shock

Determination of replacement volume (L)

% dehydration x body weight (KG)

Replacement volume for 10 kg dog with 10% dehydration=1 L

One kg of water=1 L

A=Maintenance dose= chart ml for weight given

B=Deficit=wt (kg) x % dehydration

C=ongoing loss

Fluid replacement=A+B+C L or ml

After 24 hours->Reassess

Fluid volume to be used is considered estimate

Adjustment based on reassessment is needed

effects young animals much faster and more severe

old patients or patients with a chronic disease may require more water

physical and weather conditions may change water requirement

drugs such as corticosteroids and diuretics may change requirement

good diagnosis needed for fluid therapy

clinical signs

accurate diagnosis based on clinical exams and lab data

for detection of dehydration, skin, buccal mucosa and eyeball conditions

signs of vomiting? diarrhea? polyuria? abnormal respiration? CNS depression (acidotic) or excitation (alkalotic)?

Blood electrolytes, gas and urine analyses important

Therapy for Metabolic Acidosis

Direct agents

Alkalinizing agents

neutralize proton

NaHCO3

THAM (tris; tromethamine)-irritation

Therapy for metabolic acidosis

Indirect agents

metabolized into sodium bicarb to neutralize proton

Na lactate-Lactated Ringer's

Na acetate-Acetated Polyionic

Na gluconate

Na citrate-may induce vomiting

NaHCO3 disadvantages

Short shelf-life in solution: 2 years at 4 C

Can't be autoclaved

2NaHCO3->Na2CO3 +H2O + CO2

Oral dosing interferes with gastric acidity and milk digestion

Na Lactate as indirect agent

Lactate->lactic acid->moved down chain of events->carbonic anhydrase to carbonic acid-> bicarb

bicarb used to neutralize

Indirect alkalinizing agents

Na lactate

onset time following IV administration ~30 min

D-lactate is minimally metabolized, L-form metabolized

Other indirect agents do not have the problem with Na lactate

Do not use Na lactate in patients with lactic acidosis

(plasma lactate > 9 mEq/L)

Indirect alkalinizing agents

Na acetate

Na acetate is used by muscle

Doesn't have minimally metabolized form

Acetate is more efficient than lactate

Acetate induces vasodilation-issue if in shock

Do not use Na acetate in ketoacidosis

Calculating NaHCO3 to use

mEq NaHCO3=BW (kg) x 0.3 x BD

if BD unkown use NaHCO3/indirect agent at 1-2 mEq/kg

difficult to over-alkalinize patient with normal renal function

normal kidney can take care of chemical excess

Treat etiology

Cl- responsive alkalosis: NaCl, KCl+NaCl, Ringers, NH4Cl+NaCl

Cl- resistant alkalosis: Spironolactone

H2-antihistamines or omeprazole (Prilosec) to stop H+ loss in GI tract

Normal renal function:

reabsorption in distal tubule: Cl- > HCO3-

Supply large volume normal saline->more Cl than HCO3 reabsorbed->increase plasma [Cl-], decrease plasma [HCO3-]

NH4Cl->NH3 + HCl (don't want this)

2NH4Cl + CO2 <-> CO(NH2)2 + H2O + 2HCl

NH4Cl for cattle from Univ. Georgia

54 g NH4Cl + 40 g KCL in 500 ml H2O and autoclave-> dilute with 10L of 0.9% NaCl

Don't use in liver disorders, urea poisoning

proper ventilation

treat etiology

alkalinizing agents are optional->used if ventilation alone can't do the job (ex: pulmonary obstruction)

Treat etiology-hyperventilation

Sedatives to reduce excitation and hyperventilation

Acidifying agents optional

mixed acid-base imbalances occur more frequently than simple ones, because of compensations

Treatment may convery one type to another

If pH <7.2 or >7.6 then must correct

If status unclear->give Ringer's

-have NaCl, KCl, CaCl so components can treat both

treat respiratory acidosis first

use alkalinizing agent next

Hypokalemia

causes

decreased intake

loss via GI tract

Ex: vomiting, severe salivation, diarrhea

increased aldosterone

diuretics

Hypokalemia

Signs

weak skeletal muscle contractions

cardiac arrhythmias: due to increase intracellular [Ca2+] and other things

1. increased amplitude of QRS and P wave

2. Prolongation of QT interval

3. Depressed ST segment and flattened T waves

Hypokalemia

Therapy

lab data similar to metabolic alkalosis

only tx for severe acute hypokalemia (<2.5 mEq/L) or chronic hypokalemia

KCl, K gluconate or K citrate PO, SC, IV (<0.5 mEq/kg/h)

Monitor signs of hyperkalemia

Hypokalemia+Digitalis=severe cardiac arrhythmias

Hyperkalemia

Causes

decreased urinary excretion

acidosis

diabetes mellitus

Addison's disease

excessive cell damage

increased intake

Hyperkalemia

Signs

increased neuromuscular excitability

Skeletal muscle twitching, irritability, muscle weakness

Cardiac disturbances

decreased amplitude or disappearance of P waves

decreased amplitude of R waves

intraventricular conduction blocks

widened QRS interval, QT interval

High peaked T waves

Hsu hypothesis: cardiac disturbances largely due to decreased myocardial [Ca2+] intracellularly

Hyperkalemia

therapy

lab data similar to metabolic acidosis

Ca gluconate administration

Cation-exchange resin, PO

Peritoneal dialysis

Diuretics administration

NaHCO3 (1-2 mEq/kg)

Dextrose to effect or insulin for diabetes

Routes of administration

Oral whenever possible

IV: 5% dextrose continuous for a few days in bovine fatty liver/ketosis treatment

SC routes

High K+ solutions (>30 mEq/L) may be given

Do not give 5% dextrose SC->too much fluid

can give if animal is hypertonic and needs maintenance or off feed to improve hydration status

for shock

FRVR-fluid replacement via the rectum

viable alternative for fluid resuscitation in hypovolemic shock

may be useful with IV not feasible

Disadvantage" erratic absorption rate

Contraindication in animals with diarrhea

used commonly in vitro

contains 10 mM phosphate

plasma contains ~ 0.5 mM phosphase

Would bind Ca and create hypocalcemia

Normal heart, lung, kidneys=90 ml/kg/h

Faster rate with acute condition

slow rate with chronic condition

Recommended rate: 15 ml/kg/h in most chronic conditions

Rate of IV infusion

side effects

rapid infusion may cause

1. vagal stimulation

2. pulmonary edema

Monitor central venous pressure (CVP)

1. Normal CVP (0-3 cm of water)

2. Suspend if CVP >3cm of water

May be determental to patients with CHF or acute renal failure

Rate of infusion

glucose

rapid infusion of glucose (>4 mg/kg/min)->hyperglycemia

Slow down infusion after 1st hour-particularly if anuria

After 4 h of anuria->2 ml/kg/h

Don't use K+ or Ca2+ for rapid infusion->effect on heart

plasma expanders that exert colloid osmotic pressure (COP) so body water would not easily diffuse into interstitial tissue

natural and synthetic

Crystalloids

Maintenance solutions

Do not exert COP

replacement solution or dilute an electrolytes solution using 5% dextrose/water (1:1) + 11-16 mEq/L KCl

used in liver disease

Crystalloids

other solutions

5% and 50% dextrose

7.2% NaCl

8.4% (1 M) NaHCO3

14.9% (2 M) KCl

10-40 mEq/L KCl

2M Na acetate

5M Na lactate

Synthetic colloids

plasma expanders

Fluid (1L)       Plasma Vol Expansion (L)          Duration (hr)

L. Ringer's                  0.194                                  2

6% hetastarch            0.710                                24-36

     (Hespan)

6% dextran 70            0.800                                 24

    (RescueFlow)

10% dextran 40          1.000                                 4-6

    (Rheomacrodex)

Synthetic colloid infusion

dosages and rates

Acute condition:10-40 ml/kg IV bolus to effect->constant-rate infusion (CRI)->maintain MAP 80 mmHg

Acute cats: <20 ml/kg at slow rate (10-20 min) followed by CRI (careful with allergic response, watch for hypersensitivity)

Chronic: use CRI to maintain 80 mmHg

Volume expansion: may dilute blood constituents

Rapid volume expansion: detrimental to patient with acute renal failure or CHF

Dextran 40 may cause acute renal failure

Ag-Ab reactions (except homologous plasma)-inject slowly in cats

Dextrans and hetastarch may interfere with fibrin clot formation

Hypertonic Solution

(7.2% NaCl)

Resuscitation of animals suffering from shock; large burns; tx of injury

"Small-volume resuscitation"-draw water from interstitial tissue to circulation

Decreased afterload due to vasodilation-Baroreceptor reflex

Increased O2 delivered to the heart

Hypertonic solution

combo with colloids

Hypertonic solution

adverse effects

contraindications

Volume overload

Edema

Patients hypernatremia or coagulation problems

in animals who can't voluntarily consume food

prevent malnutrition or treat malnourished animals

average treatment 3-4 days

risk/benefit ratio before prolonged treatment

infusion into a large bore vein

-hypertonic solution ~1000 mOsm/L

continuous 24 h infusion

Problems: infection, expenses, care

Total Nutritional Therapy

Calories

Glucose, fructose, invertose=4 Kcal/gm

Lipid=9 Kcal/gm

Glucose in 50% dextrose sol=50 g dextrose/100 ml H2O

1 g water=1 mL

Total nutritional therapy

Calories->math example

20 kg dog treated with glucose to meet daily requirement

How much 50% dextrose?

dog needs 1100 Kcal to meet daily requirement

1100Kcal/4 Kcal/gm=275 gm glucose

275 g/ 50 g/100 ml=550 ml

Nutritional therapy

Lipid

Lipid emulsions used as energy and EFA's provider

Used for prolonged PN

Nutritional therapy

Lipid

Preparations and dosage

soybean oil/safflower oil

egg yolk phospholipids

glycerin mixed with water

<2 g/kg/d

Nutritional therapy

Lipid

Adverse effects

High dosages cause

1. dysfunction of granulocytes, macrophages

2. phospholipids->increased eicosanoids->inflammation

Nutritional therapy

Lipid

Contraindication

Patients with high triglyceride levels

esp. hereditary hyperlipidemia

Nutritional therapy

Amino acids

general

to induce (+) nitrogen balance and provide essential amino acids

do not use intact proteins

Aminosyn, Travasol

Nutritional therapy

Amino acids

Dosages

40-50 mg/Kcal/d (dogs)

60 mg/Kcal/d (cats)

More in young, growing animals or hypoproteinemia, large draining wound

Reduced in patients with protein intolerance, ex: hepatic encephalopathy

provide calories concurrently

Severe metabolic acidosis-diarrhea, shock, gut obstruction, chock

Respiratory acidosis with inhalation anesthesia

Severe hyponatremia associated with dehydration

Severe hyperkalemia (>7 mEq/L) associated with acidosis in foals

Prompt correction of acidosis usually corrects hyperkalemia

Metabolic alkalosis and hypokalemia-abomasum disease

Severe metabolic acidosis and dehydration-grain overload and calf diarrhea

Severe K+ deficit in anorectic animals

Oral fluid therapy in neonatal diarrhea in suckling calf

Effects of anesthetic and surgery

Problems in all species

1. general anesthetics: decreased CP, blood flow and GFR, increased vasodilation (Closure of Ca2+ channels)->

increased fluid requirement

2. increased fluid loss via expired air and surgery

3. third space

Fluid therapy:2-5 ml/kg/h crystalloid routinely

IV fluid->decreased plasma proteins and blood cell

Volume overload and hypertension in post-surgical period