Supportive Care and Fluid Therapy

Question 1

define supportive care

Answer 1

non-pharmaceutical methods to enhance the quality of care the patient receives, including thermal support, padding and positioning, eye protection, and management of oral secretions and regurgitation

Question 2

how does heat loss occur? 4 mechanisms

Answer 2

radiation: most important
-heat generated in body is given off to atmosphere

conduction:
movement of heat from the body to a surface it is in contact with

convection:
a fluid (air or water flowing by the skin carries away heat (wind chill)

evaporation: of liquid (sweat) promotes heat loss from skin surface

Question 3

describe normal thermoregulation

Answer 3

the body normally maintains its temp within 0.2 degrees celsius of normal when not anesthetized

response to cold: shivering and peripheral vascocontstriction

response to heat: sweating, panting, vasodilation

Question 4

describe thermoregulation and anesthesia

Answer 4

1. gen anesthesia depresses thermoregulation
2. increases interthreshold range from +/- 0.2 to +/- 3.5!!
3. hypothermia promoted by:
   -cold operating rooms
   -room temp scrub solutions
   -room temp IV fluids and lavage
   -contact with cold surgery tables
   -heat loss to airway by admin of cold and dry gases

Question 5

describe adverse effects of hypothermia

Answer 5

1. increased infection rates
2. prolonged recovery
3. decreased anesthetic requirements
4. cold discomfort
5. increased viscosity of the blood: increases workload of heart
6. abnormalities in coagulation
7. arrhythmias
8. cardiac arrest

Question 6

describe prevention of each type of heat loss

Answer 6

radiation:
1. blankets: keep non surgical surface area of patient covered
2. warm opterating rooms

conduction:
1. ensure always a pad or blanket between the patient and the table
2. keep patient protected from other cold surfaces

convection:
1. warm scrub/lavage fluids
2. no fans in operating room

evaporation:
1. ensure patient stays as dry as possible at all times
2. only scrub areas that are required to be scrubbed
3. heat and moisture exchange devices

Question 7

describe active warming

Answer 7

1. forced air warming devices (bear hugger)- most common!
2. circulating warm water blankets; can get holes though and patient is covered in water
3. conductive polymer blankets: HotDog; pretty safe as long as towel between device and patient is kept dry

dangerous!!
1. microwaved objects!!- okay for awake patients that can get off if too hot, but NOT for anesthetized patients
2. warm fluid bags
3. microwavable discs
4. heating blankets designed for humans

Question 8

describe hyperthermia and anesthesia

Answer 8

less frequently a concern than hypothermia

causes: often iatrogenic
1. overzealous active warming of patients
2. opioids
3. malignant hyperthermia; was in pigs, has mostly been bred out

Question 9

describe padding and positioning

Answer 9

1. most procedures requiring anesthesia place the patient in an abnormal position for a prolonged period of time (dorsal recumbency)
2. inadequate padding and unnatural positioning can lead to post-anesthetic patient discomfort, wounds, myopathies, and neuropathies
3. most concerning in: very large patients (horses, cattle), and patients without inherent padding (emaciated patients)
4. ensure ample padding that is applicable to the individual:
   -thinner pads or blankets are sufficient for small anima; patients
   -10-15cm thick pads for large animals
5. place extremities and joints in a natural position if possible:
   -avoid extreme extension or flexion of the legs
   -ensure that the patient isn’t resting on top of the tail
6. pull dependent forelimb cranially in large animal patients to avoid radial nerve injury!

Question 10

describe eye protection (why needed and consequences if not)

Answer 10

1. patients are unable to protect their own eyes under anesthesia
   -eyelids are often open
   -patients do not blink while under anesthesia
   -may have forced air warming device blowing dry air onto the cornea
   -cornea may come into contact with towels, drapes, and surgery tables
2. common consequences of general anesthesia:
   -corneal ulcerations and/or perforation

Question 11

describe methods of protecting they eye

Answer 11

1. frequent application of eye lubricant
2. closing eyelids when possible
3. taping the eyes shut: especially if surgeon is working around the head

Question 12

describe management of saliva

Answer 12

1. ruminant patients continue to produce saliva throughout anesthesia
2. the pharynx should be elevated such that saliva goes forward and out of the mouth
3. saliva entering the trachea can cause resp difficulty and if severe could lead to post op pneumonia
4. if possible, the oral cavity can be suctioned periodically to remove saliva

Question 13

why does regurgitation occur in patients under anesthesia? (3)

Answer 13

1. relaxation of esophageal sphincters
2. manipulation of abdominal contents
3. dorsal positioning of the patient

Question 14

what complications can result from regurgitation?

Answer 14

1. esophageal stricture due to damage caused by acidic stomach contents
2. pneumonia caused by aspiration of gastric contents
3. nasal and pharyngeal irritation

Question 15

describe prevalence and reduction of regurgitation

Answer 15

1. most frequently documented peri operative GI complication
2. progression to aspiration pneumonia is 0.17%
3. give antacids to make stomach contents less acidic, begin several days pre op for effect
4. metaclopromide and cisapride decrease incidence but do not completely prevent regurg
   -cerenia/metaclopramide does NOT decrease regurg!

Question 16

describe regurgitation management during induction and operation

Answer 16

1. observe patient diligently throughout premedication, induction, maintenance, and recovery
2. capture airway rapidly after induction and inflate cuff appropriately
3. recheck tube placement and cuff inflation frequently
4. when regurgitating: keep head tipped down to encourage drainage of reflux out of the mouth as opposed toward airway (+/- suction)

Question 17

describe regurgitation management during recovery

Answer 17

1. examine oral cavity and pharynx prior to extubation
2. lavage esophagus when regurg has occurred
3. extubate the cuff partially inflated (squeegee contents out with it)
4. position in sterna recumbency with head/nose down

Question 18

what are 5 goals of peri-operative fluid therapy? when studying, also be familiar with distribution of body water slides!

Answer 18

1. correction of pre-existing abnormalities
2. correction of normal on-going and surgically induced losses
3. support of cardiovascular function
4. counter negative physiologic effects associated with anesthetic drugs
5. maintenance of a patent intravenous catheter

Question 19

describe the types of fluid used under anesthesia (3)

Answer 19

1. replacement solutions (isotonic):
   -LRS, plasmalyte A, 0.9% saline
2. hypertonic saline: resuscitation measures
   -7.5% NaCl, 23.4% NaCl
3. colloids:
   -hetastarch, vetstarch, albumin, etc.

Question 20

describe isotonic replacement solutions

Answer 20

1. most common fluid type used in anesthesia
2. isotonic formulations containing electrolytes and buffers such as lactate and acetate
3. high sodium concentrations close to ECF
4. used for replacement of existing and ongoing losses
5. advantages: low cost, low viscosity, vehicle for many fluid additives and drugs

Question 21

describe hypertonic saline

Answer 21

1. use:
   -rapid resuscitation of patients in shock
   -treatment of elevated intracranial pressure
2. 100mL of hypertonic expands plasma volume by up to 400mL (1:4 return); bolus effect only lasts for 20-30 minutes
3. dose: 4-6ml/kg for dogs or 4ml/kg for cats, administered for over 5 minutes
4. pulls volume from interstitial fluid

Question 22

describe colloids

Answer 22

1. cause an increase in colloid osmotic pressure which pulls fluid into the vasculature, expanding circulating volumne
2. most useful in patients that are already hypoalbuminemic
3. natural colloids: products containing albumin: whole blood, plasma, canine albumin
4. synthetic: hydroxyethyl starches- modified polymers of amylopectin
   -in patients under general anesthesia; generally administered as a single bolus of 3-5ml/kg IV
   -adverse effects:
   –altered coagulation, renal injury
   –recommended to avoid in septic patient
   current recommendation:
   -do not exceed 20 ml/kg/day in dogs and 10ml/kg/day in cats

Question 23

describe methods of fluid administration

Answer 23

1. IV:
   -most common
   -simple, minimal adverse effects
2. intraosseous:
   -often necessary in tiny patients when venous access unavailable
   -complications: pain, potential fracture of bone, often fall out
3. subcutaneous:
   -not commonly used peri-anesthetically
   -less effective for rapid resuscitation
   -fluid must be absorbed from interstitial space

Question 24

what is the current IV fluid rate for healthy patients under anesthesia?

Answer 24

dogs: 5ml/kg/hour
cats: 3

rate should be adjusted to account based on patient needs (existing dehydration, cardiovascular disease, renal disease)

Question 25

what is the current shock dose of fluids”

Answer 25

based on patient’s blood volume
dogs: 90ml/kg
cats: 55ml/kg

used in patients in need of rapid volume resuscitation: give 1/4 then reassess and repeat