A 38-year-old woman is undergoing elective abdominal hysterectomy under general anesthesia. After induction with propofol and intubation, the anesthesiologist notes the following during maintenance: the patient's eyes are centrally positioned, pupils are moderately dilated and reactive to light, lacrimation is present, and there is brisk response to surgical stimulation with a heart rate increase from 70 to 95 bpm and blood pressure rise from 110/70 to 130/85 mmHg. Muscle tone is normal and there is purposeful movement in response to the surgical incision. What stage of anesthesia is the patient currently in?

Explanation

## Clinical Assessment of Anesthetic Depth ### Identifying the Stage The patient demonstrates several key features that place her in **Stage 3, Plane 1 (Light Anesthesia)**: **Key Point:** The presence of purposeful movement and brisk cardiovascular response to surgical stimulation indicates insufficient depth of anesthesia for major surgery. ### Guedel's Classification — Stage 3 Planes | Feature | Plane 1 (Light) | Plane 2 (Surgical) | Plane 3 (Deep) | |---------|-----------------|-------------------|----------------| | **Eye position** | Central | Central | Divergent | | **Pupil size** | Moderately dilated | Moderately dilated | Widely dilated | | **Lacrimation** | Present | Absent | Absent | | **Muscle tone** | Normal/↑ | Normal | ↓ ↓ | | **Corneal reflex** | Present | Present | Absent | | **Response to incision** | Purposeful movement | No movement | No movement | | **Cardiovascular response** | Brisk (↑HR, ↑BP) | Stable | Depressed | **High-Yield:** The **presence of lacrimation + purposeful movement + brisk cardiovascular response** is the diagnostic triad for Plane 1 anesthesia. ### Clinical Pearl In Plane 1, the patient is too lightly anesthetized for major surgery. The anesthesiologist must deepen anesthesia by increasing volatile agent concentration or administering additional IV induction agent to reach Plane 2 (surgical anesthesia), where movement and autonomic response are abolished. **Mnemonic: CALM** — Central eyes, Adequate tone, Lacrimation present, Movement to stimulation = Plane 1 ### Why This Matters Operating in Plane 1 risks: - Intraoperative awareness - Excessive sympathetic response - Patient discomfort - Increased myocardial oxygen demand [cite:Gupta & Rana Textbook of Anesthesia Ch 8]