Monitoring the Anesthetized Patient Flashcards
What is analgesia?
The absence of pain
What is hypnosis?
Artificially induced sleep or a trance resembling sleep from which an animal can be aroused by a stimulus
How are oxygenation and ventilation assessed subjectively?
Reflex activity Eye position Muscle relaxation Heart rate, pulse quality and strength Respiratory rate, volume, character Mucous membrane color and refill time Response to noxious stimulus
How are oxygenation and ventilation assessed objectively?
ECG Blood pressure Hemoglobin saturation CO2 production/elimination Inhaled anesthetic concentration Neuromuscular responses EEG Temporally processed data
What types of equipment is used to measure oxygenation and ventilation objectively?
Doppler (indirect), oscillometric (indirect), or arterial catheter (direct) for blood pressure
Pulse oximeter for Hgb saturation
Capnograph for CO2 production/elimination
Train-of-four, tetanic fade for neuromuscular responses
Bispectral index from EEG, heart rate variability from ECG for temporally processed data
What types of equipment is used to measure oxygenation and ventilation subjectively?
Does not require specialized monitoring
What are the normal parameters for heart rate?
Dog: 60-160 Cat: 120-220 Horse: 25-45 Cow, sheep, goat: 60-80 Pig: 60-110
What are the normal parameters for respiratory rate?
Dog: 20-40 Cat: 20-40 Horse: 8-10 Cow: 10-30 Pig: 12-20 Sheep, goat: 15-30
What is the normal parameter for systolic pressure?
100-160 mmHg
What is the normal parameter for diastolic pressure?
60-90 mmHg
What is the normal parameter for mean arterial pressure?
60-80 mmHg
Is it possible to be well oxygenated but poorly ventilated?
Yes, due to poor perfusion, delivery of oxygen to tissues is dependent on CO2 and arterial CO2 content. Ventilation is defined by the level of CO2.
What are causes of pulse oximeter artifact?
Vasoconstriction
Probe motion
Hypotension
Large number of false alarms (probe slips out of position)
Limited placement locations
Misleading results in the face of severe anemia
What does the ECG represent?
ECG produces a continuous waveform representing the summation of electrical ativity of the heart for a given axis or plane
Is ECG a good stand-alone monitor?
No, it does not provide assessment of perfusion, information on cardiac pumping activity, and it is limited to its assessment of the conduction speed
What are the differences between direct and indirect methods to measure blood pressure?
Indirect is non-invasive and direct is invasive
What are the 2 methods to indirectly measure blood pressure?
Doppler and oscillometric
How are doppler and oscillometric similar?
The both proved systolic BP and HR, they do not measure flow or perfusion
How are doppler and oscillometric different?
Oscillometric also gives diastolic and mean arterial pressures, doppler does not
What is the accuracy of any indirect blood pressure method directly related to?
Cuff fit
What are the differentials for absence of a CO2 waveform following endotracheal intubation?
Improper ET tube placement and patency: depressed or absent capnogram may be due to a dislodged ET tube
Misplaced ET tube (place it in esophagus)
Obstructed ET tube or airway, a leak around ET tube cuff, or disconnection of the ET tube from the anesthetic machine
What objective parameter solely defines the adequacy of ventilation?
Capnography
What is the most useful subjective sign for assessing the depth of anesthesia?
Respiratory rate, volume, and character (gives the best indicator of ventilation)
What are the 4 guidelines for monitoring veterinary patients advocated by the ACVA?
Assessment of circulation
Assessment of ventilation
Maintenance of an anesthetic record of events
Assignment of a responsible person to be aware of the patient’s status and prepared to intervene, if necessary
What are Guedel’s 4 stages of anesthesia?
Stage 1: Stage of voluntary movement
Stage 2: stage of delirium or involuntary excitement
Stage 3: Stage of surgical anesthesia
Stage 4: stage of medullary depression
Describe stage 1 of anesthesia
Patient is awake or asleep but arousable
This stage lasts until ataxia and the loss of righting reflex
Describe stage 2 of anesthesia
Lasts from the loss of unconsciousness to the onset of regular breathing
CNS is depressed
Patient shows signs of exaggerated reflex activity, vocalization, swallowing, urination/defecation, dilated pupils, breath holding and/or hyperpnea, tachypnea, palpebral reflexes will be prominent, and vomiting
These patients are not conscious and are not aware of what they are doing
Describe stage 3 of anesthesia
Light, medium, and deep
Medium is where we want patients for surgery
Describe light stage 3 of anesthesia
Spontaneous eyeball movement, may respond to toe pinch, brisk palpebral reflex present, strong jaw tone, eye rotated ventrally in ruminants
Describe medium stage 3 of anesthesia
Stable respiration and pulse, abolished laryngeal reflexes, response to toe pinch, sluggish palpebral reflex, strong corneal reflex, adequate muscle relaxation, pupil is central but not dilated in ruminants, no purposeful response to noxious stimuli
Describe deep stage 3 of anesthesia
Decreased intercostal muscle function, reduced tidal volume, increased respiratory rate, diaphragmatic breathing, profound muscle relaxation, weak corneal reflex, ventrally rotate pupil in ruminants, pupil sluggish or non-responsive to light
Describe stage 4 of anesthesia
Do not want patients here
CNS is extremely depressed and spontaneous respiration ceases
The heart continues to beat for only a short time
Blood pressure is low, CRT is delayed, pupils are widely dilated and nonresponsive to light, sphincter tone is lost
What is a differential list for a tachycardic anesthetized patient?
Sympathetic stimulation Hypotension Hypovolemia Hypoxemia (early) or anemia Hypercarbia Hyperthermia Acute anaphylactoid response Drugs Electrolyte disturbances
What is a differential list for a bradycardic anesthetized patient?
Excessive sympathetic depression Increased vagal tone Hypothermia Hyperkalemia Elevated intracranial pressure Hypoxemia (late) Drugs
What is a differential list for a tachypneic anesthetized patient?
Sympathetic stimulation or pain Hypoxemia Hypercarbia Hyperthermia CSF acidosis Drug effects
What is a differential list for a bradypneic/apneic anesthetized patient?
Excessive respiratory depression
Recent hyperventilation
Hypothermia
Musculoskeletal weakness or paralysis
Do anesthetized animals feel pain? Justify your answer based on your knowledge of neurophysiology and anesthetic action.
No, pain is a conscious experience and the anesthetized animal is unconscious. However, adequate analgesia will reduce physiologic and autonomic response (non-purposeful movement) to noxious stimuli (movement occurring at the level of the spinal cord not brain) which anesthesia does not have control over
