VTNE Review: Anesthetic Monitoring

invasive monitoring

refers to any equipment that has to be placed in the body

non invasive monitoring

refers to any equipment that read variables that are readily apparent

simple and easy to use but not always as accurate when compared to invasive equipment

electrocardiogram (ECG)

• visual representation of heart conduction and provides heart rate

• allows you to assess heart rhythm, electrical conduction through the heart, and identify arrythmias’s

• disadvantage: does not indicate cardiac function and can look normal even though peripheral blood pressure is compromised

normal heart rate for dogs

70-100 bpm

normal heart rate for cats

100-200 bpm

pulse oximetry (SPO2)

• measures oxygen saturation in blood and gives a pulse rate

• provides a visual pulse waveform

• disadvantage: has to be moved frequently due to capillaries being crushed under the compression caused by the monitoring device; unreliable at low saturation levels and difficult to get a reading if tissue has dark pigmentation

dopplers

• monitor systolic blood pressure using an ultrasonic doppler, sphygmomanometer, and inflatable cuff

• also gives an audible representation of pulse rate

• disadvantage: accuracy depends on correct cuff size

oscillometric

provide systolic, mean, and diastolic pressures using an inflatable cuff

normal blood pressure range

• systolic: 100-160 mmHg

• diastolic: 70-90 mmHg

• mean: 80-110 mmHg

capnography

• measures the end tidal and inspiratory carbon dioxide and anesthetic gas concentration

• also provides a respiratory rate and waveform

• end tidal CO2 readings are 5-10 mmHg lower than actual alveolar contractions

• allows you to access systematic metabolism, cardiac output, pulmonary perfusion, and the adequacy of patient ventilation

temperature probe

• used to monitor the core temperature of the animal

• normal temp in dogs: 101-102.5

• normal temp in cats: 100.5-102.5

central venous pressure (CVP)

• indicates fluid status and assesses cardiac output

• normal range standing awake: 0-4 cm H2O

• normal range anesthetized: 2-7 cm H2O

• higher readings than normal indicate hypervolemia or myocardial depression/heart failure and lower readings indicate hypovolemia

arterial catheter for blood pressure

• gives a constant systolic, mean, and diastolic blood pressure values along with a visual waveform

• the waveform can be used to evaluate whether cardiac arrhythmias may be causing poor pressures or when pulse deficits become detrimental to the patient

• waveform can also indicate the presence of vasodilation or vasoconstriction

blood gas

• pH, lactate, partial pressure of oxygen and carbon dioxide, bicarbonate

• gives an accurate representation of the respiratory function and acid-base balance

• must be taken from an artery to evaluate respiratory function

normal pH value

7.35-7.45

normal PaCO2

35-45 mmHg

normal PsO2

90-115 mmHg on room air

on oxygen- 500 mmHg

normal SaO2

>95%

normal HCO3

18-26 mEq/L

normal BE

-2 to +2

eye position

• during a surgical plane of anesthesia eyes roll ventrally

• the eye will be central during light and deep planes of anesthesia

• dissociative anesthetics will keep the eye central during all planes of anesthesia

palpebral reflex

• only present during a light plane of anesthesia

• tapping the medial/lateral canthus elicits a response

withdrawal reflex

• only present during light planes of anesthesia

• performed by pinching a toe and is often used to access whether an animal is deep enough for endotracheal intubation during a masked induction

jaw tone

indicates muscle relaxation that varies with anesthetic depth

pale mucous membranes indicate what?

vasoconstriction, decreased cardiac output, hypoxia, and anemia

dark pink mucous membranes indicate what?

vasodilation, sludging of blood in the capillaries, and high CO2 levels

cyanotic mucous membranes indicate what?

severe hypoxemia

tachypnea

can be caused by a light anesthetic plane, pain, hypercarbia, hypovolemia, hypoxemia, drugs, and cerebral spinal fluid acidosis

apnea

can be caused by a deep anesthetic plane, hypothermia, recent hyperventilation, musculoskeletal paralysis and drugs

tachycardia

can be caused by a light anesthetic plane, pain, hypotension, hypoxemia, hypercarbia, ischemia, acute anaphylactic reaction, anemia, and drugs

bradycardia

can be caused by a deep anesthetic plane, hypertension, increased intracranial pressure, surgical vagal reflex, hypothermia, hyperkalemia, myocardial ischemia, and drugs

hypertension

can be caused by a light of an anesthetic plane, pain, hypercarbia, fever, and drugs

hypotension

can be caused by a deep anesthetic plane, hypovolemia, sepsis, shock, and drugs