ECC Fluid Therapy Flashcards
Body Water Distribution
- total body water = 60% BW
- ICF 40%
- ECF 20%
> interstitial fluid 15%
> plasma 5%
Indications of Fluid Therapy
Ø Resuscitation
- Is the patient in shock / hypovolemic?
Ø Rehydration
- Is the patient dehydrated?
Ø Maintenance
- Is the patient eating or drinking?
ØOngoing losses
- How to predict?
The 4D’s of Fluid Therapy
Drug
Dose
Duration
De-escalation
Assessment of Hydration & Volume Status
> what do we look at?
Ø Subjective: no single index
Ø Change in body weight
- 90% of acute ∆ body mass = ∆ TBW
- 3rd spacing, anorexia
Ø Physical examination
- ∆ interstitial volume
- ∆ intravascular volume
Ø ∆ intracellular (ICF) volume: unable on PE
Ø Laboratory findings:
- PCV/TS
- Electrolytes - Lactate
- BUN
- USG
Ø Dehydration = water deficit in interstitial & ICF compartment (% of BW)
- Rehydration / replace water deficit
ØHypovolemia = ↓ intravascular volume (plasma water or whole blood loss)
- Intravascular volume resuscitation
what lab tests to asses hydration and volume status?
- PCV/TS
- Electrolytes
- Lactate
- BUN
- USG
Hypovolemia / Shock
> what are the signs and parameters?
Ø Normal or altered (depressed) mentation
Ø Perfusion parameters:
- injected / pale, grey muddy, white MM
- rapid / prolonged, absent CRT
- warm / cool extremities, hypothermia
- ↑ lactate
Ø Cardiovascular signs:
- tachycardia, bradycardia, inappropriate normocardia
- bounding / poor pulse quality, hypotension
- collapse of peripheral veins
Resuscitation Phase
- what are our goals? what shock syndromes are responsive to fluid resuscitation? contraindications?
Ø Rapid IV fluid bolus: expand intravascular space, correct perfusion deficits
Ø Shock syndromes responsive to fluid resuscitation:
- Hypovolemic
Less so:
- Distributive
> Vasopressor
> Positive inotropes
- Obstructive
> Surgical intervention
> Thrombolysis
Ø Contraindicated: cardiogenic shock!
Balanced Electrolyte Solutions
- plasmalyte A
- lactated ringer
Isotonic Crystalloids
- shock dose? fluid challenge? how do they distribute?
Ø Shock dose: 1 blood volume
- Dog: 80-90 mL/kg/hr
- Cat: 50-60 mL/kg/hr
Ø Fluid challenge:
- Dog: 10-20 mL/kg over 10-20 mins
- Cat: 5-10 mL/kg over 10-20 mins
Ø Rapidly redistribution into ECF compartment
- 30 mins: ∼25% remains in intravascular space
- capillary leak, ↓ oncotic pressure
The Origin of Shock Dose
Ø Total blood volume
- Dog: 8-9% of BW (80-90 mL/kg)
- Cat: 5-6% of BW (50-60 mL/kg)
when do we see detectable shock signs? mild vs moderate?
ØDetectable shock signs: 10-30% blood volume loss
- Mild signs (compensated shock): 10-15% loss
- Moderate signs (early decompensated): 15-30% loss
target of shock dose
Target: expand blood volume by 30%
- Dog: 30 mL/kg
- Cat: 20 mL/kg
Hypertonic Saline
> what is its use and how does it work? additional benefits?
Ø Small volume resuscitation (hypovolemic, hemorrhagic, septic shock)
- Dose: 2-3-5 mL/kg, <1 mL/kg/min
Ø Transient (<30 mins) > osmotic diuresis + rapid Na+ redistribution
- ∴ combined with other resuscitative fluids
ØAdditional benefits:
- ↓ cerebral edema, ↓ ICP (traumatic brain injury, intracranial hypertension)
- ↓ endothelial swelling
- mild peripheral vasodilation
- ↑ cardiac contractility
- immunomodulatory effects
Synthetic Colloids
- what are they? what can they be used for? adverse effects?
Ø Hydroxyethyl starch (e.g. Vetstarch, Voluven)
- Draw fluid (controversial) + retain fluid (not if “leaky” vessels) within intravascular space
Ø Small volume resuscitation: 2-5 mL/kg over 10-30 mins
- Dog: 10-20 mL/kg
- Cat: 5-10 mL/kg
Ø Hypoproteinemia (TS <3.5 g/dL), ↓ oncotic pressure
ØAdverse effects:
- Human: ↑ mortality, AKI, coagulopathy
- Veterinary: dose-dependent coagulopathy (>20 mL/kg/d)
Blood Component Therapy
> what are our options? dose rate?
- Fresh / stored whole blood
- Fresh frozen plasma (FFP) / Frozen plasma (FP)
- Packed RBCs
- etc.
Ø Dose rate: underlying condition + hemodynamics
- 1.5 mL/kg/min over 15-20 mins vs. 4-6 hours
- whole blood: 20-30 mL/kg
- pRBCs: 10-20 mL/kg
- FFP: 10-20 mL/kg
Clinical hemodynamic parameters:
- HR
- BP, pulse quality
- Mentation
- MM colour, CRT
- Extremities & core temperatures
- Lactate <2.5 mmol/L, ∆ lactate better predictor of survival
- POC bloodwork (PCV, TS, electrolytes, acid-base)
() - Other parameters:
- UOP (indirect measurement of renal blood flow) ≥ 1 mL/kg/hr
- PCV/TS
- BG
- Electrolytes
- Acid-base balance
- Oxygenation
- Ventilation
Interstitial Dehydration Estimation
- < 5%
> not detectable
> history of volume loss - 5-6% (mild)
> tacky mucous membranes - 7-10% (moderate)
> decreased skin turgor
> prolonged capillary refill times
> dry mucous membranes
> retracted globes with orbits - 10-12% (severe)
> CV effects (tachycardia, poor pulse quality, +/- hypotension)
> Dull corneas
> persistent skin tent (complete loss of skin elasticity)
> signs of compensated shock - > 12% (moribund)
signs of decompensated shock
imminent death
Replacement Phase
- how is fluid deficit calculated?
- how long do we do fluid therapy for? what are we trying to replace?
Ø Fluid deficit (L) = estimated % dehydrated x ideal BW (kg)
Ø Sustained fluid therapy for 12-36 hours: replace interstitial + ICF losses
Ø Analogy: dried-up sponge
- Different sponges: intrinsic rate of fluid absorbency
- Impossible to predict which type of sponge
Ø Rehydrate over 24 hr ± front loading > reassessment
Maintenance Phase
- what is this? what is this requirement?
Ø Not eating / drinking: unable to maintain own fluid balance
Ø Daily maintenance fluid requirements:
- Energy (water) to maintain homeostasis in fed, thermoneutral environment
- Non-linear relationship: BSA
- Over-conditioned / anorexic patient: ↓ fluid rate
- Puppies & kittens: ↑ fluid rate
Estimated Ongoing Losses
- due to what conditions?
Ø GI losses: diarrhea, vomiting, ptylism
- Double the crude estimated volume
Ø Renal losses: polyuria
- Free catch, catheter collection system, metabolic cage, weigh litter/bedding
Ø Additional losses:
- Fever: + 10% maintenance fluid for every ↑ 1°C
- 3rd space loss: drain production
- Burn (mL/h): [25 + % total BSA burned] x BSA (m2)
Formulating IV Fluid Therapy Plan
- Replacement: Fluid deficit = estimated % dH2O x ideal BW
- Maintenance: RER = BW0.75 x 70 or pre-made charts
- Ongoing losses: ~100mL x 2
> reassess & adjust
Types of Intravenous Fluids
Crystalloids
- small solutes (electrolytes)
- readily cross endothelial membrane
- equilibrate throughout ECF space
Colloids
- large macromolecules
- restricted by healthy* endothelium
- ↑ COP, retain* fluid in intravascular space
what are isotonic solutions? examples? what are they for / indications?
Ø Similar osmolarity & [Na+] as plasma and ECF
Ø Normal saline
- 0.9% NaCl
Ø Balanced electrolyte solutions
- Plasma-Lyte A, Plasma-Lyte 148 (Normosol-R), Lactated Ringer’s solution
Ø Indications: expand intravascular + interstitial space (ECF)
- IV fluid resuscitation
- Replacement
- Maintenance: kidneys excrete excess electrolytes
Hypertonic Saline
- what is it? rate? effects? indications?
Ø Higher osmolarity + [Na+] than plasma + ECF
- 3%, 5%, 7.5%, 10%, 23.5% NaCl
Ø <1 mL/kg/min > bradycardia, vasodilation, hypotension
- acute hyperosmolarity
- central vasomotor center inhibition
- peripheral vasomotor effect
Ø Indications:
- Small volume resuscitation: hypovolemic / hemorrhagic / septic shock
- Traumatic brain injury, intracranial hypertension
- Severe hyponatremia
Hypertonic Saline additional benefits
- ↓ cerebral edema, ↓ ICP, ↑ CPP
- ↑ rheology: ↓ endothelial swelling
- mild peripheral vasodilation > ↑ CO + tissue perfusion
- ↑ cardiac contractility, augment MAP
- immunomodulatory effects
Hypotonic Solutions
- purpsoe and use? indications?
Ø Lower osmolarity + [Na+] than plasma and ECF
- 0.45% NaCl, 1⁄2 strength PLA, 1⁄2 strength LRS
Ø Combine with dextrose to ↑ osmolarity
- D5W & 0.45% NaCl, 2/3 & 1/3, Plasma-Lyte 56 (Normosol-M), D5W
Ø Indications: replace free water deficit
- Hypernatremia, hypotonic fluid loss
- Maintenance: ↓ ability to excrete excess electrolytes or tolerate ↑ intravascular volume
Hypotonic Solutions contraindications?
IV fluid resuscitation (bolus therapy)
- Ineffective intravascular volume expansion
- Intravascular hemolysis
- Life-threatening cerebral edema
synthetic colloids - how do they compare to plasma? how do they impact coagulation?
Ø Isooncotic (6%) or hyperoncotic (10%) to plasma
Ø Dose-dependent (>20 mL/kg/d) coagulopathy
- Platelet function, vWF, FVIII, ristocetin cofactor activities
Natural Colloids
- how do they compare to plasma? issues with certain kinds?
ØAllogenic blood products
- Isooncotic to plasma
ØHuman serum albumin (HSA)
- hypersensitivity reactions
- healthy or repeated dosing»_space;> critically ill
ØLyophilized canine serum albumin (CSA)
- acceptable safety profile
- cost prohibitive
Distribution of IV Fluids
- colloid vs isotonic vs hypotonic?
colloid - stays in plasma
isotonic - plasma and interstitial fluid
hypotonic - plasma, intersticial fluid, and ICF
Potential Complications for overzealous fluid support
- increased hydrostatic pressures
- increased vascular endothelial permeability
- hypoalbuminemia
Predispositions to complications from fluid therapy
Predispositions:
- severe inflammation
- severe hypoproteinemia
- cardiac disease
- pulmonary disease
somewhat common Potential Complications of fluid therapy
Ø Dilutional coagulopathy
Ø Aggravate recent hemorrhage
Ø Reperfusion injury
Ø Volume overload:
- Pulmonary & organ edema
- Cavitary effusion
- Gelatinous subcutaneous tissue
- Peripheral pitting edema
- Increased jugular venous distention
- Chemosis, serous nasal discharges
Discontinuation of Fluid Therapy
- how should we do it, to avoid what problems?
Gradual weaning over 24 hr if high flow rates
- Renal medullary washout
- Impaired urine concentrating abilities
- Severe dehydration (if drinking insufficiently to keep up)
