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Anesthesia > Intro to Anesthesia and analgesia > Flashcards

Intro to Anesthesia and analgesia Flashcards

1
Q

Define general anesthesia

A

A state of unconsciousness produced by a process of controlled, reversible, intoxication of the CNS whereby the patient neither perceives nor recalls noxious stimuli

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2
Q

Mechanism of action of anesthetics

A

largely unknown

-must be lipophilic to have action within CNS (cross BBB)
-interact with inhibitory pathways

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3
Q

What inhibitory pathways are involved with aesthetics?

A
  • Gamma amino butyric acid (GABA) in the brain

-Glycine in the spinal cord

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4
Q

Triad of anesthesia

A

-unconsciousness
-analgesia
-muscle relaxation

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5
Q

Can one drug fulfill all three components of the triad?

A

No, not without causing undesirable effects

However, all three components can be reached by administering a combination of drugs (in smaller dosages!!)

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6
Q

Balanced/multimodal anesthesia

A

-The use of a number of different drugs to produce a state of general anesthesia which fulfills unconsciousness, analgesia, and muscle relaxation

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7
Q

Common drugs used for unconsciousness

A

-isoflurane, sevoflurane, propofol, alfaxalone, ketamine

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8
Q

Common drugs for analgesia

A

-opioids, NSAIDs, local anesthetics, ketamine, alpha 2 agonists

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9
Q

Common drugs for muscle relaxation

A

-benzodiazepines, guaifenesin, alpha 2 agonists

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10
Q

Muscle relaxation component of anesthesia

A

-high doses of anesthetics working on spinal cord reduce skeletal muscle tone
BUT if need no muscle tone then need to use peripheral neuromuscular blocking agents

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11
Q

Results of high doses of anesthetic

A

-higher doses of anesthetic drugs lead to more/deeper brain depression= suppression of reflexes

-can lead to death

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12
Q

Suppression of reflexes from anesthesia

A
  1. Autonomic reflexes- hemodynamic, respiratory, thermoregulatory = BAD suppression
  2. Somatic reflexes- proprioceptive, muscle= GOOD suppression
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13
Q

Depth of anesthesia

A

Depth is dynamic depending on the procedure and the drug used.
>different parts of the procedure can cause changes in the animals depth

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14
Q

Stages of anesthesia

A

Stage 1: voluntary excitement- drug first given

Stage 2: involuntary excitement

Stage 3: surgical plane of anesthesia

Stage 4: cardiopulmonary arrest imminent!!!

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15
Q

Planes of anesthesia

A

Plane 1: light

Plane 2: surgical depth

Plane 3: deep- hypoventilation; nearing stage 4

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16
Q

Effects of general anesthesia

A
  1. CNS depression
  2. CVS depression
  3. Respiratory depression
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17
Q

CNS depression from anesthesia

A

-loss of consciousness
-dampening of reflexes: CVS (hypotension), resp (hypoventilation), thermoregulatory (hypothermia), postural (reduced muscle tone)
-central modulation of nociception

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18
Q

Depression of CVS from anesthesia

A
  1. Baroreflex suppression (central and peripheral)
    2.Changes in autonomic balance
  2. Changes in vasomotor tone (drug effects, centrally and peripherally)
  3. Myocardial depression (direct-drugs; and indirect- hypoxemia, hypercapnia)
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19
Q

Respiratory depression from anesthesia

A

**Hypoventilation (hypercapnia/hypoxemia)

  1. Reflex suppression leads to decreased ventilatory response, increase in CO2= decrease in pH and O2
  2. Reduced muscle activity
  3. Alveolar collapse/small airway closure (atelectasis)
  4. Reduced functional residual capacity

5.Ventilation/perfusion mismatch

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20
Q

Main objective of anesthesia

A

Maintain tissue perfusion (deliver O2, remove waste)

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21
Q

Anesthetic risk

A
  • majority of deaths due to human error. much higher in animals than humans
    -risk closely linked to physical status (graded 1-5; 5=worst)
    -risk increased in places with poor facilities and equipment, support staff
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22
Q

Steps to help improve outcome of anesthesia

A

-pre-anesthetic assessment
-stabilization prior to anesthesia
-anticipation of complications (exam, bloodwork, history, surgical procedure proposed)

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23
Q

Avoid mistakes with anesthesia

A

delegate, label syringes, double check doses, use checklists, don’t assume anything, teamwork &practice scenarios, review procedures (mortality rounds)

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24
Q

5 phases of anesthesia

A
  1. Pre-operative assessment
  2. premedication
  3. induction

4.Maintenance

5.Recovery

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25
Q

Pre-operative assessment phase

A

-patient stabilization
-provision of analgesia

26
Q

Premedication phase

A

-anxiolysis/sedation and initiation of analgesia if not already provided

27
Q

Induction phase

A

-provide drugs, induce anesthesia (consciousness to unconsciousness)

-often rapid 20-90 secs; slower with inhalation techniques (may see excitement phase)

28
Q

what affects induction drug choice?

A

-species
-facilities
-health status of patient
-clinician preference

29
Q

Maintenance phase

A

-monitoring life support; risk increases with time under
-continuation of analgesia

30
Q

Recovery phase

A

-aftercare- day patient; ICU
-continuation of analgesia
-may need sedation

31
Q

Pre anesthetic prep for dogs, cats, horses

A

-fasted at least 6-8 hrs (12 hrs common)
-access to water until 1hr before premed
-horses may also have a small amount of hay to prevent ileus for short procedures

32
Q

Pre anesthetic prep for ruminants

A

-fasted 24-48hrs
-no water last 6 hrs since gorging water increases volume of rumen contents
-less than 18hrs fasting increases the risk of bloat
-very prone to regurgitation

33
Q

What factors affect pre-anesthetic drug choice?

A

-species
-facilities
-clinician preference
- health status of the animal

34
Q

pre-medication drugs

A

-acepromazine
-benzodiazepines
-alpha 2 agonists
-opioids

35
Q

Deep sedation vs. general anesthesia

A

Anesthesia if you can pass endotracheal tube. With deep sedation, animal will have swallowing reflex and can protect its own airway

**however heavy sedation may still be detrimental

36
Q

Respiratory stats during anesthesia

A

RR 6-12 br/min
SatO2: 99-100%
ETCO2: 35-45mmHg

37
Q

Cardiovascular stats during anesthesia

A

Minimum BP: 80/40 (60) mmHg
**kidney and brain affected under 60

Normal BP: 120/80 (90) mmHg

Check for good peripheral pulse quality

38
Q

Can heart rate be used to assess cardiovascular system during anesthesia?

A

No

39
Q

How to check renal system during anesthesia?

A

-place urinary catheter
>important for horses as don’t want them to slip when they wake
>important during procedures that increase diuresis

40
Q

How to check hepatic system during anesthesia?

A

-maintain good perfusion

41
Q

How to check GI, musculoskeletal systems during anesthesia?

A

-cannot assess easily under GA
-must keep hemodynamics stable, leads to good perfusion or important tissues

42
Q

Lactate and GA

A

-lactate accumulates during a long GA

43
Q

Minimal monitoring of CNS

A

-intermittent every 5mins

Check:
-eye position and reflexes
-skeletal muscle tone (as brain depresses=lose muscle tone)
-breathing patterns (more abdominal with depth)
-vasomotor tone (lose vascular tone with depth=BP decreases)

44
Q

Eye reflexes (dog/cat) when in light plane of anesthesia

A

-eye central
-palpebral reflex present
-shiny cornea

45
Q

Eye reflexes (dog/cat) when in surgical plane of anesthesia

A

-eye rotated ventral/medial
-no (or slight) palpebral reflex
-more upper eyelid to check
-dry cornea- Need lube

46
Q

Eye reflexes of horse during anesthesia (deep)

A

-inhalational= central eye, sluggish palpebral

-injectable= central eye, rapid palpebral

47
Q

Eye reflexes of horse during anesthesia (light)

A

-tearing
-nystagmus
-spontaneous blinking

48
Q

Pedal withdrawal reflex

A

-all or nothing information
-no info on anesthetic depth
-useful more in exotics

49
Q

Corneal reflex

A

-causes blink
-not advised=corneal damage and loss of reflex=patient already dead

50
Q

Anal tone

A

-anus may wink when poked
-useful if you don’t have access to head

51
Q

Muscle tone under anesthesia

A

Light= muscle tone +++, rigid
Surgical= muscle tone ++
Deep= muscle tone +

*can assess jaw tone
*too much relaxation can compromise lung ventilation

52
Q

Breathing patterns under anesthesia

A

Light=fast, deep breath hold

Surgical= rhythmic, intercostal/abdominal

**Note: ruminants have fast and shallow (tachypnea) breathing= normal

53
Q

Life support during anesthesia

A

-warmth
-hydration
-BP support (IV fluids, drugs)
-delivery of oxygen and lung ventilation
-protect musculoskeletal and NS with positioning and padding- especially heavy/large animals

54
Q

How do animals lose heat?

A

-convection
-radiation
-conduction
-evaporation

*lack of muscle activity, depressed metabolic rate, vasodilatory drugs

55
Q

How do animals lose fluid during anesthesia?

A

-cold, dry gases= evaporate
-open body cavities
-bleeding
-maintenance (cannot drink)

56
Q

How do we play a role in fluid support?

A

-balanced electrolyte solutions
-colloid oncotic agents
-monitor ins/outs where possible

57
Q

Normal ins/outs of fluid loss

A

Blood loss: 1gram=1ml

Urine production: 1-2 ml/kg/hr

58
Q

Pre-emptive analgesia

A

-anticipate painful event and give analgesics ahead of time
-minimize wind up/sensitization

59
Q

Multi-modal analgesia

A

-different drugs combat pain in different ways
-type of pain will help you decide which drug to try

60
Q

What happens if pain goes untreated?

A

Acute pain which is a symptom of disease CAN RESULT IN chronic pain=disease

Anesthesia (24 decks)

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