Surgery & Anesthesia: Stages/Planes of Anesthesia and Reflexes – Flashcards

Immediately after inhalation or injectable agent administered Patient is conscious but disoriented Decreased sensitivity to pain All reflexes present Patient may struggle, urinate, defecate or show other signs of fear or anxiety

Begins with loss of consciousness All reflexes present (may appear exaggerated) Animal can chew and swallow (may yawn) Brain starts to lose control of voluntary body functions Animal may exhibit involuntary excitement: rapid limb movement, vocalization, struggling Breathing may be irregular or animal may appear to hold its breath Epinephrine release, cardiac arrhythmias & arrest

Light plane of anesthesia Respiratory pattern becomes regular Limb movements cease Eyeballs begin to rotate ventrally Gag and swallow reflexes depressed (intubation) Pedal and palpebral reflexes present but weaker

Medium plane of anesthesia (suitable for most surgical procedures) Eyeballs rotate ventromedially Respiration regular but shallow RR, HR and BP decreased Pedal and swallowing reflexes lost Laryngeal and palpebral reflexes are weakened or lost

Deep plane of anesthesia HR, BP, and RR decrease; increase in CRT Eyeball position - central

Early anesthetic overdose Marked drop in HR & BP CRT is prolonged; pale mm Abdominal breathing (inadequate ventilation) Pupils dilate; pupillary light reflex (PLR) is lost Too deep an anesthetic plane; animal in risk of cardiopulmonary arrest (CPA)

Respiration ceases Cardiac arrest Death Resuscitation of patient required

Blink reflex Lightly tap medial or lateral canthus of eye Loss of this reflex dependent upon drugs used

Lost at medium depth of anesthesia Regained just before patient regains consciousness Once returns, safe to remove ET tube

Toe-pinch Patient withdraws limb in response to pinching of a digit or pad Helpful for mask inductions (when assessing other reflexes difficult)

Pupillary light reflex (PLR) Constriction (miosis) of pupils in response to light

Touch cornea with sterile object (e.g. drop of artificial tears) and note whether blinks Not commonly used in dogs and cats (used primarily for large animals)

Stimulated when larynx touched by object This reflex protects animal from aspiration into lungs Present during intubation if animal not sufficiently anesthetized

Deeper anesthesia, increases muscle relaxation One example is jaw tone Jaw tone is lost when animal anesthetized