Monitoring and Complications Part 1

Question 1

what do we monitor during anesthesia?

Answer 1

1. anesthetic depths
2. cardiovascular system: adequate delivery of oxygen to the tissues
3. respiratory system:
   -adequate oxygenation
   -adequate ventilation
4. temperature

Question 2

describe subjective/hand monitoring of anesthetic depth

Answer 2

1. jaw tone: want SOME
   -if have a lot, too light/not very deep
   -if none; potentially too deep
2. eye position: will change
   -surgical plane is ideally ventromedial
   -staring right at you? could be light and could be deep; if central, nystagmus indicates lighter, esp in large animals
3. palpebral/corneal reflexes
   -both present: light
   -loss of palpebral: surgical plane
   -loss of corneal: deep, too deep
   (camelids never lose palpebral unless extremely deep)
4. rectal tone:
   yes or no

Question 3

describe objective/machine monitoring of anesthetic depth

Answer 3

1. heart rate:
   -tachy: lighter
   brady: deeper
2. respiratory rate
   -same as HR
3. blood pressure:
   -hypertension: light
   -hypotension: deep
4. EEG/BIS (not done clinically)

these categories are highly affected by anesthetic drugs!!!

Question 4

describe subjective/hand monitoring of cardiovascular system

Answer 4

1. mucous membrane color: assessment of oxygenation and perfusion
   -injected, pink, pale pink, cyanotic
2. CRT: assess perfusion (should be less than 2 sec)
3. cardiac auscultation:
   -ID rate, rhythm, murmurs
4. pulse palpation: assess CV status:
   -strong, weak, thready, not palpable

Question 5

describe objective/machine monitoring of CV system

Answer 5

1. ECG: visual representation of electrical activity of heart; does NOT tell you if heart contracts
   -used to monitor HR and ID arrhythmias
2. blood pressure: representative of perfusion pressure to the periphery
   -systolic arterial pressure: peak pressure reached by arterial pulse
   -diastolic arterial pressure: lowest value
   -mean arterial pressure: avg arterial blood pressure throughout pulse wave
   -range of autoregulation: range of blood pressure in which blood flow to organ is autoregulated by body (MAP 60-150mmHg)
   –MAP minimum during anesthesia:
   –SA: 60mmHg
   –LA: 70mmHg
   -hypotension can lead to decreased delivery of oxygen to the tissues and ischemic injury
   -hypertension can lead to over-perfusion, which can cause an increase in intracranial pressure, retinal detachment, hemorrhage, etc.

Question 6

how to measure blood pressure?

Answer 6

1. invasive: most accurate
   -need an arterial catheter connected to a pressure transducer; provides beat to beat blood pressure measurement
   -disadvantages: technically challenging, potential complications (hematoma, ischemic injury to extremity, infection)
   -best for critical patients in which fluctuations in blood pressure are anticipated
2. non-invasive: for healthy, non-critical patients
   -oscillometric: cuff on an extremity; machine provides SAP, DAP, MAP
   -doppler + sphymomanometer: cuff on extremity proximal to a doppler crystal; inflate cuff until pulse sound stops then slowly deflate; pressure when pulse sounds return = SAP (not in cats; is closer to MAP); also gives audible pulse of patient

disadvantages of noninvasive:
-less accurate so can really only use as trends (going up or going down, not exact numbers)
-accuracy affected by severe hypotension or hypertension, arrhythmias
-does not provide continuous measurement

Question 7

describe subjective/hand monitoring of the respiratory system

Answer 7

1. respiratory rate: ventilation
   -counting chest excursions or movement of the bag
2. respiratory depth: ventilation
   -assessing size of chest excursions or evacuation of the bag
3. mucus membrane color: oxygenation
   -can be hard if anemic, cannot detect changes in cyanosis

Question 8

describe objective/machine monitoring of respiratory system

Answer 8

1. pulse oximetry:
   -measures the % of hemoglobin that is saturated with oxygen
   -normal: healthy, awake adult breathing room air: 98-100%
   -uses alternating red and infrared light, commonly placed on tongue or digit: can shave fur on carpus, tarsus, or base of tail and apply a transreflectance (flat) probe
   -sources of error: pigmentation, vasoconstriction, motion, thickness of tissue, anemia, ambient light
   -how trust? if HR matches true pulse, quality of pulse signal, quality of plethysmograph
   -if in doubt, the only way to check is arterial blood gas
2. capnography
   -a measure of the amount of CO2 in expired gas
   –normal EtCo2 in awake, healthy patient is 35-45mmHg
   -direct assessment of patient ventilatory status
   -indirect assessment of patient cardiac output and metabolic rate
   -some units also measure oxygen and anesthetic gases
   -expired anesthetic gas levels used as a surrogate measure of the amount of inhalant in the brain and can be used to titrate the inhalant anesthetic to effect
   -amount of CO2 expired is inversely related to adequacy of alveolar ventilation

-hypercapnia: hypoventilation
-hypocapnia: hyperventilation

3. blood gas analysis