Lecture 12 Intra-operative Fluid therapy & Peri-Anesthetic Complications Flashcards
1
Q
Why do IV fluids during anesthesia?
A
- Maintain intra-vascular volume
- Animals are fasted, unlikely to drink for several hours post-op
- Replace fluid losses during anesthesia
- Evaporation, respiratory, hemorrhage, urine/sweat
- Compensate for vasodilation effects of anesthetic drugs, support CO/tissue perfusion
- DO2 = CO x CaO2
- Maintain acid/base & electrolyte normality
2
Q
What are different reasons why you would change different types of fluids
A
- Fluid/Cardiovascular status
- Electrolyte & acid/base
- Albumin, Colloid oncotic pressure (COP)
- Glucose
- Correct/stabilize pre-op to ↓drug induced hypotension & anesthetic risk
3
Q
- What is the target MAP during anesthesia?
- SAP
- HR
A
- MAP > 60 mmHg,
- SAP > 90 mmHg
- HR
- 60-110 bpm dogs,
- 120-160 bpm cats
4
Q
- Target Values for Perioperative plasma albumin?
- Colloid oncotic pressure
- TP
A
- Plasma albumin >2.0 g/dl
- Colloid Oncotic Pressure 15-20 mmHg
- TP > 3.5 g/dl
5
Q
- Target Values for Perioperative PCV?
- Lactate
- Base deficit
- Central venous pressure
A
- PCV > 25-30%
- Lactate < 2 mmol/L
- Base deficit +4 to – 4 mmol/L
- Central venous pressure 6-8 cmH2O
6
Q
What is a Crystalloid
A
contain ions/solutes that distribute to all body fluid compartments, are isotonic, composition similar to extra-cellular fluid (ECF)
7
Q
What are the 4 crystalloids and what do they contain?
A
- Lactated Ringer’s (LRS)
- Na = 130, Cl = 109, K = 4,
- *Ca = 2.7,* lactate
- Plasmalyte A or Normosol-R
- Na = 140, Cl = 98, K = 5,
- *Mg = 3, *Acetate & Gluconate
- .9% Sodium Chloride
- Na = 154, Cl = 154
- No K+, indicated in hyperkalemia, no base => ‘acidifying’
8
Q
Which crystalloids are better for liver patients?
A
Plasmalyte A or Normosol-R
9
Q
- What is the historic intraoperative fluid rate?
- Fluid rate now for normovolemic patients?
A
- Historically, 5-10 ml/kg/hr recommended
- Now:
- 5ml/kg/hr for first hour,
- 2.5ml/kg/hr thereafter
Note: Restrictive IV fluids NOT appropriate for critical patients
10
Q
What are the downfalls of using the old 5-10ml/kg/hr fluid rate?
A
- Median urine output ~0.5 ml/kg/hr
- Fluid retention 1 -2 liters in 30kg dog/4hrs
- Gain in body weight of > 1.0 kg
- PCV ↓ to 29-33, TP ↓ 4.5 – 5.1
- 30-45min after crystalloid, 30% in vascular space, 70% excreted by kidney or into ECF (fluid retention)
11
Q
- What are synthetic colloids?
- Used for?
A
- Contain large MW molecules that stay in vascular space,
- exert colloid oncotic pressure
12
Q
What are the 2 synthetic colloids
A
- Hydroxyethylstarch (Hetastarch)
- Hypertonic Saline – 7.5% NaCl
13
Q
What are 4 side effects of synthetic colloids
A
- Fluid overload
- Coagulopathies
- Anaphylactic reactions
- Renal dysfunction
14
Q
What are the 4 starling forces
A
- Pc = capillary hydrostatic pressure
- Pi = interstitial fluid hydrostatic pressure
- πp = plasma protein oncotic pressure
- πi = interstitial protein oncotic pressure
15
Q
If πp < πi => fluid moves out of vessels => edema
Albumin provides ~80% of plasma oncotic pressure
A
16
Q
- What is the half life of Hydroxyethylstarch (Hetastarch)
- What are the different rate options and when would you use them?
A
- ½ life 12-24hrs
- Fluid rates:
- Maintenance in hypoalbuminemic patients
- 1-2 ml/kg maintenance
- Hypotension or 10-20% blood loss
- bolus 5-20ml/kg
- Up to 20ml/kg/day
- Maintenance in hypoalbuminemic patients
17
Q
- Hypertonic Saline (7.5% NaCl) use?
- How does it do what it does
A
- ↑ blood volume & blood pressure
- By:
- Draws water from interstitial space
- venoconstriction of large veins
- ↑coronary/cerebral blood flow
- ↑ inotropy by ↑cardiac intra-cellular Ca2+
18
Q
Side effects of using Hypertonic Saline ,7.5% NaCl
A
- Hypernatremia,
- hypokalemia,
- hemolysis,
- hemodilution
19
Q
What are the peri-anesthetic complications
A
- Cardiovascular*
- Hemorrhage, hypotension, arrhythmias, cardiac arrest
- Respiratory insufficiency*
- Hypoventilation, hypoxemia
- Upper Airway Obstruction
- Hypothermia/Hyperthermia
- Gastroesophageal Reflux/Aspiration
- Equine => post anesthetic myopathy/neuropathy
- Ruminants => aspiration of ruminal contents
20
Q
The Key to avoiding peri-anesthetic complications is to
A
- anticipate possible concerns => anesthesia work-up
- Have an action plan should these complications arise
21
Q
Majority of peri-operative mortality occurs at what hours?
A
within 1st 3 hours
22
Q
- What is the equation for delivery of oxygen to tissues?
- equation for Cardiac output
A
- DO2 = CO x CaO2
- CO= cardiac output
- Ca02= content of oxygen in the blood
- CaO2 = HbO2 + PaO2
23
Q
- If you have a normal awake animal with PCV of 20 (anemic) what will compensate?
- Why is anesthesia bad for these patients?
A
- compensate for ↓ O2 content (RBC) by ↑ CO
- by ↑ HR & vasoconstriction
- Anesthesia interferes with ability to compensate
- ↓ HR & causing vasodilation
24
Q
- What do you do if a patient’s PCV is <20 if you plan on anethetizing
- PCV 20-30
- PCV > 30
A
- PCV < 20 => transfusion recommended
- PCV 20-30 => maybe
- depends on organ reserve, expected losses, chronicity/regeneration
- PCV > 30 => no transfusion
25
Q
What are Cases of ‘expected’ Intra-op blood loss
A
- Splenectomy
- Liver biopsy/Liver lobectomy
- Prolonged Pt/Ptt should be corrected pre-op
- Ventral slot
- Limb amputation
- Large tumor removal
- Not expected cases:
- OHE (drop ovarian pedicle),
- TPLO, cutting popliteal artery
26
Q
- What does anesthesia do to PCV, TP, colloid oncotic pressure (COP)
- Why is this important to know?
A
- decreases PCV, TP, COP
- Take PCV, TP or COP after induction
27
Q
How do you prepare for intra-op Blood Loss
A
- Calculate total blood volume, allowable loss
- Quantitate blood loss intra-operatively
- Replace fluid/blood as indicated
28
Q
- How do you calculate total blood volume in dog?
- Cat?
A
- Dog 90ml/kg
- cat 70ml/kg
29
Q
How do you Calculate Allowable Blood Loss
(ask professor)
A
- Calculate 10, 20 & 30% of total blood volume
- Total blood volume x (0.1, 0.2 or 0.3) x 100
30
Q
26
(ask professor)
A
31
Q
- At what % of blood loss will you see clinical signs
- What clinical signs?
A
- May see clinical signs ≥ 10% loss
- Hypotension, +/- tachycardia
32
Q
- As As CO ↓ because of blood loss, what will happen to anesthetic depth
- What do you do with vaporizer
- When do you replace loss?
A
As CO ↓
- anesthetic depth will ↑
- ↓ vaporizer setting
- Replace loss as it occurs
33
Q
- How much blood does a q-tip hold?
- 4x4 sponge
- Lap sponge
- Weight 1gm = how many mls?
A
- Q-tip .1ml
- 4x4 sponge 5-15ml
- Lap sponge 50ml
- Weight 1gm = 1ml
34
Q
How do you use the suction cannister to quantitate blood loss?
A
35
Q
- If you have a 10-15 % blood loss what fluid do you use?
- 15-25%
- 25-30%
A
- 10 - 15%
- replace with crystalloid, 3 x mls lost
- Because crystalloid will move out of vasculature
- replace with crystalloid, 3 x mls lost
- 15 - 25%
- crystalloid + colloid
- >25 - 30%
- whole blood or packed RBCs + colloid (plasma and/or hetastarch)
36
Q
- What does whole blood contain
- At what % of blood loss would you use it?
A
- Contains:
- RBC
- protein
- platelets
- clotting factors
- Severe >30-50% blood loss
37
Q
- What is the PCV of packed RBCs?
- When do you use it?
A
- PCV 80-90%
- Less severe blood loss or + plasma for severe blood loss
38
Q
What is the calculation on how much blood to give?
A
milliters blood required =
Blood Vol. X (desired PCV– recipient PCV*) / Donor PCV
39
Q
*takes up to __ hrs for redistribution after acute hemorrhage
A
24
40
Q
- What does Fresh Frozen Plasma contain?
- When would you use it?
- Need low or high doses?
A
- Contains:
- Albumin
- plasma proteins
- clotting factors
- Use it when:
- Hypoalbuminemia (along with colloids)
- prolonged clotting times
- Need high doses
- 45ml/kg to raise albumin 1g/dl
41
Q
Can you get albumin alone?
A
Yes! Canine/Human Albumin
