Chapter 5

1. Chapter 5 Anesthetic Monitoring To keep the patient safe and to regulate anesthetic depth

2. Monitoring Parameters • Vital signs • Homeostatic mechanism’s response to anesthesia • Heart rate • Heart rhythm • Respiratory rate and depth • Mucous membrane color • Capillary refill time • Pulse strength • Blood pressure • Body temperature • Best indicator of patient wellbeing

3. Monitoring Parameters (Cont’d) • Reflexes • Involuntary response to stimulus • Palpebral, corneal, pedal, swallowing, laryngeal, and papillary light reflexes • Indicators of anesthetic depth • Parameters offer predictable responses to anesthesia at various depths • May be affected by drugs, disease, or individual response variation • Monitor anesthetized patients as often as possible; continuously is ideal

4. Stages and Planes of Anesthesia • Four stages (I, II, III, IV) • Stage III divided into four planes • From stage I through stage IV there is a progressive decrease in pain perception, motor coordination, consciousness, reflex responses, muscle tone, and cardiopulmonary function

5. Stage I • Period of voluntary movement • Patient begins to lose consciousness • Characterized by: • Fear, excitement, disorientation, struggling, urination, defecation • Increased heart rate and respiratory rate • Stage ends with loss of ability to stand and recumbency

6. Stage II • Period of involuntary movement; the “excitement stage” • Characterized by: • Breathing irregular • Vocalization, struggling, paddling • Increased heart and respiratory rate, pupils dilated, muscle tone marked, reflexes present • Actions are not under conscious control • Stage ends with muscle relaxation, decreased respiratory rate, and decreased reflex activity

7. Stage III • Period of surgical anesthesia • Divided into four planes • Plane 1: not adequate for surgery: • Regular respiratory pattern, no involuntary limb movements • Eyeballs start to rotate ventrally, pupils partially constricted, decreased pupillary light reflex • Endotracheal tube may be passed and connected to gas anesthetic machine • Other reflexes are still present but decreased response

8. Stage III Plane 2 • Suitable depth for most surgical procedures • Characterized by: • Regular and shallow respiration with decreased rate • Blood pressure and heart rate mildly decreased • Relaxed muscle tone • Pedal and swallowing reflexes are absent • Ventromedial eye rotation

9. Stage III Plane 2 (Cont’d) • Surgical stimulation may produce: • Mild increase in heart rate, blood pressure, or respiratory rate • Patient remains unconscious and immobile • Pupillary light response is sluggish; pupil size is moderate

10. Stage III Plane 3 • Deep anesthesia—excessive for most procedures • Characterized by: • Low heart and respiratory rates, decreased tidal volume • Reduced pulse strength • Increased capillary refill time (CRT) • Poor to absent papillary light reflex; central eyeballs; moderately dilated pupils • Reflexes are totally absent; muscle tone is very relaxed

11. Stage III Plane 4 • Early anesthesia overdose • Characterized by: • Abdominal breathing • Fully dilated pupils; dry eyes • All reflexes are absent • Marked depression of the cardiovascular system, pale mucous membranes, increased CRT • Flaccid muscle tone

12. Stage IV • Period of anesthetic overdose • Characterized by: • Cessation of respiration • Circulatory collapse • Death • Resuscitate immediately to save the patient

13. Stage III in 3 Planes • Alternative classification • Plane 1: “light” surgical anesthesia • Not suitable for surgery • Plane 2: “medium” surgical anesthesia • Optimum depth for most surgical procedures • Plane 3: “deep” surgical anesthesia • Excessive depth

14. Objectives of Surgical Anesthesia • Patient doesn’t move • Patient isn’t aware • Patient doesn’t feel pain • Patient has no memory of the procedure