Lecture 12 Intra-operative Fluid therapy & Peri-Anesthetic Complications

Question 1

Why do IV fluids during anesthesia?

Answer 1

1. —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
2. —Compensate for vasodilation effects of anesthetic drugs, support CO/tissue perfusion
   
   • DO2 = CO x CaO2
3. —Maintain acid/base & electrolyte normality

Question 2

What are different reasons why you would change different types of fluids

Answer 2

1. —Fluid/Cardiovascular status
2. —Electrolyte & acid/base
3. —Albumin, Colloid oncotic pressure (COP)
4. —Glucose
5. —Correct/stabilize pre-op to ↓drug induced hypotension & anesthetic risk

Question 3

1. What is the target MAP during anesthesia?
2. SAP
3. HR

Answer 3

1. —MAP > 60 mmHg,
2. SAP > 90 mmHg
3. —HR
   
   • 60-110 bpm dogs,
   • 120-160 bpm cats

Question 4

1. Target Values for Perioperative plasma albumin?
2. Colloid oncotic pressure
3. TP

Answer 4

1. —Plasma albumin >2.0 g/dl
2. —Colloid Oncotic Pressure 15-20 mmHg
3. —TP > 3.5 g/dl

Question 5

1. Target Values for Perioperative PCV?
2. Lactate
3. Base deficit
4. Central venous pressure

Answer 5

1. —PCV > 25-30%
2. —Lactate < 2 mmol/L
3. —Base deficit +4 to – 4 mmol/L
4. —Central venous pressure 6-8 cmH2O

Question 6

What is a Crystalloid

Answer 6

—contain ions/solutes that distribute to all body fluid compartments, are isotonic, composition similar to extra-cellular fluid (ECF)

Question 7

What are the 4 crystalloids and what do they contain?

Answer 7

1. —Lactated Ringer’s (LRS)
   
   • —Na = 130, Cl = 109, K = 4,
   • *Ca = 2.7,* lactate
2. —Plasmalyte A or Normosol-R
   
   • —Na = 140, Cl = 98, K = 5,
   • *Mg = 3, *Acetate & Gluconate
3. —.9% Sodium Chloride
   
   • —Na = 154, Cl = 154
   • —No K+, indicated in hyperkalemia, no base => ‘acidifying’

Question 8

Which crystalloids are better for liver patients?

Answer 8

—Plasmalyte A or Normosol-R

Question 9

1. What is the historic intraoperative fluid rate?
2. Fluid rate now for normovolemic patients?

Answer 9

1. —Historically, 5-10 ml/kg/hr recommended
2. Now:
   • —5ml/kg/hr for first hour,
   • —2.5ml/kg/hr thereafter

Note: —Restrictive IV fluids NOT appropriate for critical patients

Question 10

What are the downfalls of using the old 5-10ml/kg/hr fluid rate?

Answer 10

• 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)

Question 11

1. What are synthetic colloids?
2. Used for?

Answer 11

1. —Contain large MW molecules that stay in vascular space,
2. exert colloid oncotic pressure

Question 12

What are the 2 synthetic colloids

Answer 12

1. Hydroxyethylstarch (Hetastarch)
2. Hypertonic Saline – 7.5% NaCl

Question 13

What are 4 side effects of synthetic colloids

Answer 13

1. —Fluid overload
2. —Coagulopathies
3. —Anaphylactic reactions
4. —Renal dysfunction

Question 14

What are the 4 starling forces

Answer 14

1. Pc = capillary hydrostatic pressure
2. Pi = interstitial fluid hydrostatic pressure
3. πp = plasma protein oncotic pressure
4. πi = interstitial protein oncotic pressure

Question 15

—If πp < πi => fluid moves out of vessels => edema

—Albumin provides ~80% of plasma oncotic pressure

Answer 15

Question 16

1. What is the half life of Hydroxyethylstarch (Hetastarch)
2. What are the different rate options and when would you use them?

Answer 16

1. ½ life 12-24hrs
2. 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

Question 17

1. Hypertonic Saline (7.5% NaCl) use?
2. How does it do what it does

Answer 17

1. ↑ blood volume & blood pressure
2. By:
   
   • —Draws water from interstitial space
   • —venoconstriction of large veins
   • —↑coronary/cerebral blood flow
   • —↑ inotropy by ↑cardiac intra-cellular Ca2+

Question 18

Side effects of using Hypertonic Saline ,7.5% NaCl

Answer 18

1. —Hypernatremia,
2. hypokalemia,
3. hemolysis,
4. hemodilution

Question 19

What are the peri-anesthetic complications

Answer 19

1. —Cardiovascular*
   
   • —Hemorrhage, hypotension, arrhythmias, cardiac arrest
2. —Respiratory insufficiency*
   
   • —Hypoventilation, hypoxemia
   • —Upper Airway Obstruction
3. —Hypothermia/Hyperthermia
4. —Gastroesophageal Reflux/Aspiration
5. —Equine => post anesthetic myopathy/neuropathy
6. —Ruminants => aspiration of ruminal contents

Question 20

The Key to avoiding peri-anesthetic complications is to

Answer 20

• —anticipate possible concerns => anesthesia work-up
  
  • —Have an action plan should these complications arise

Question 21

Majority of peri-operative mortality occurs at what hours?

Answer 21

—within 1st 3 hours

Question 22

1. What is the equation for delivery of oxygen to tissues?
2. equation for Cardiac output

Answer 22

1. DO2 = CO x CaO2
   
   • CO= cardiac output
   • Ca02= content of oxygen in the blood
2. CaO2 = HbO2 + PaO2

Question 23

1. If you have a normal awake animal with PCV of 20 (anemic) what will compensate?
2. Why is anesthesia bad for these patients?

Answer 23

1. —compensate for ↓ O2 content (RBC) by ↑ CO
   
   • —by ↑ HR & vasoconstriction
2. —Anesthesia interferes with ability to compensate
   
   • ↓ HR & causing vasodilation

Question 24

1. What do you do if a patient’s PCV is <20 if you plan on anethetizing
2. PCV 20-30
3. PCV > 30

Answer 24

1. —PCV < 20 => transfusion recommended
2. —PCV 20-30 => maybe
   
   • —depends on organ reserve, expected losses, chronicity/regeneration
3. —PCV > 30 => no transfusion

Question 25

What are Cases of ‘expected’ Intra-op blood loss

Answer 25

1. —Splenectomy 2. —Liver biopsy/Liver lobectomy * —Prolonged Pt/Ptt should be corrected pre-op 3. —Ventral slot 4. —Limb amputation 5. —Large tumor removal 6. —Not expected cases: * OHE (drop ovarian pedicle), * TPLO, cutting popliteal artery

Question 26

1. What does anesthesia do to —PCV, TP, colloid oncotic pressure (COP) 2. Why is this important to know?

Answer 26

1. —decreases PCV, TP, COP 2. —Take PCV, TP or COP after induction

Question 27

How do you prepare for intra-op Blood Loss

Answer 27

1. —Calculate total blood volume, allowable loss 2. —Quantitate blood loss intra-operatively 3. —Replace fluid/blood as indicated

Question 28

1. How do you calculate total blood volume in dog? 2. Cat?

Answer 28

1. —Dog 90ml/kg 2. —cat 70ml/kg

Question 29

How do you Calculate Allowable Blood Loss (ask professor)

Answer 29

* Calculate 10, 20 & 30% of total blood volume * Total blood volume x (0.1, 0.2 or 0.3) x 100

Question 30

26 | (ask professor)

Answer 30

Question 31

1. At what % of blood loss will you see clinical signs 2. What clinical signs?

Answer 31

1. May see clinical signs ≥ 10% loss 2. Hypotension, +/- tachycardia

Question 32

1. As As CO ↓ because of blood loss, what will happen to anesthetic depth 2. What do you do with vaporizer 3. When do you replace loss?

Answer 32

As CO ↓ 1. anesthetic depth will ↑ 2. ↓ vaporizer setting 3. Replace loss as it occurs

Question 33

1. How much blood does a q-tip hold? 2. —4x4 sponge 3. —Lap sponge 4. —Weight 1gm = how many mls?

Answer 33

1. —Q-tip .1ml 2. —4x4 sponge 5-15ml 3. —Lap sponge 50ml 4. —Weight 1gm = 1ml

Question 34

How do you use the suction cannister to quantitate blood loss?

Answer 34

Question 35

1. If you have a 10-15 % blood loss what fluid do you use? 2. 15-25% 3. 25-30%

Answer 35

1. —10 - 15% * replace with crystalloid, 3 x mls lost * Because crystalloid will move out of vasculature 2. —15 - 25% * crystalloid + colloid 3. —\>25 - 30% * whole blood or packed RBCs + colloid (plasma and/or hetastarch)

Question 36

1. What does whole blood contain 2. At what % of blood loss would you use it?

Answer 36

1. Contains: * —RBC * protein * platelets * clotting factors 2. —Severe \>30-50% blood loss

Question 37

1. What is the PCV of packed RBCs? 2. When do you use it?

Answer 37

1. PCV 80-90% 2. —Less severe blood loss or + plasma for severe blood loss

Question 38

What is the calculation on how much blood to give?

Answer 38

milliters blood required = Blood Vol. X (desired PCV– recipient PCV\*) / Donor PCV

Question 39

\*takes up to __ hrs for redistribution after acute hemorrhage

Answer 39

24

Question 40

1. What does —Fresh Frozen Plasma contain? 2. When would you use it? 3. Need low or high doses?

Answer 40

1. Contains: * —Albumin * plasma proteins * clotting factors 2. —Use it when: * Hypoalbuminemia (along with colloids) * prolonged clotting times 3. —Need high doses * —45ml/kg to raise albumin 1g/dl

Question 41

Can you get albumin alone?

Answer 41

Yes! —Canine/Human Albumin