Monitoring and Complications Part 1 Flashcards
what do we monitor during anesthesia?
- anesthetic depths
- cardiovascular system: adequate delivery of oxygen to the tissues
- respiratory system:
-adequate oxygenation
-adequate ventilation - temperature
describe subjective/hand monitoring of anesthetic depth
- jaw tone: want SOME
-if have a lot, too light/not very deep
-if none; potentially too deep - 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 - palpebral/corneal reflexes
-both present: light
-loss of palpebral: surgical plane
-loss of corneal: deep, too deep
(camelids never lose palpebral unless extremely deep) - rectal tone:
yes or no
describe objective/machine monitoring of anesthetic depth
- heart rate:
-tachy: lighter
brady: deeper - respiratory rate
-same as HR - blood pressure:
-hypertension: light
-hypotension: deep - EEG/BIS (not done clinically)
these categories are highly affected by anesthetic drugs!!!
describe subjective/hand monitoring of cardiovascular system
- mucous membrane color: assessment of oxygenation and perfusion
-injected, pink, pale pink, cyanotic - CRT: assess perfusion (should be less than 2 sec)
- cardiac auscultation:
-ID rate, rhythm, murmurs - pulse palpation: assess CV status:
-strong, weak, thready, not palpable
describe objective/machine monitoring of CV system
- ECG: visual representation of electrical activity of heart; does NOT tell you if heart contracts
-used to monitor HR and ID arrhythmias - 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.
how to measure blood pressure?
- 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 - 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
describe subjective/hand monitoring of the respiratory system
- respiratory rate: ventilation
-counting chest excursions or movement of the bag - respiratory depth: ventilation
-assessing size of chest excursions or evacuation of the bag - mucus membrane color: oxygenation
-can be hard if anemic, cannot detect changes in cyanosis
describe objective/machine monitoring of respiratory system
- 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 - 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
- blood gas analysis