A Detailed Look at What is Stage 2 of Anesthesia?

October 14, 2025 •

4 min read

In 1937, Dr. Arthur Guedel first systematically described the four stages of anesthesia, a classification still referenced by anesthesiologists today. A crucial, and sometimes challenging, phase within this framework is understanding what is stage 2 of anesthesia, also called the excitement or delirium stage. This phase is characterized by a loss of consciousness coupled with disinhibited, involuntary movements and physiological instability.

Quick Summary

Stage 2 of anesthesia is the period of excitement and delirium following the loss of consciousness, characterized by involuntary movements, irregular breathing, and heightened airway reflexes. Anesthesiologists use fast-acting agents and careful management to minimize this risky stage.

Key Points

Excitement and Delirium: Stage 2 is characterized by involuntary movements, excitement, and potential delirium after the initial loss of consciousness.
Physiological Instability: Vital signs such as heart rate, blood pressure, and respiration become irregular during this stage.
Heightened Airway Reflexes: Airway reflexes are often hypersensitive in Stage 2, increasing the risk of complications like laryngospasm and vomiting.
Historical Context: The classification of four anesthesia stages was developed by Dr. Arthur Guedel in 1937, based on observations during ether administration.
Modern Anesthesia Minimizes Stage 2: Fast-acting intravenous agents like propofol are used today to induce surgical anesthesia rapidly, often bypassing or significantly shortening the excitement stage.
Aspiration Risk: Due to the combination of vomiting and compromised airway reflexes, Stage 2 carries a risk of aspirating stomach contents into the lungs.

The Historical Significance of Guedel's Classification

The concept of four distinct stages of general anesthesia was first introduced by Dr. Arthur Guedel in 1937, based primarily on observations made during the administration of diethyl ether. At the time, monitoring a patient's depth of anesthesia relied heavily on physical signs such as eye movements, breathing patterns, and muscle tone. Guedel's classification provided a systematic, if rudimentary, safety system for clinicians during an era with limited pharmacological agents and monitoring technology. The framework provided a roadmap from induction to overdose, helping anesthesiologists navigate the patient's unconscious state. While the advent of modern anesthetic drugs and technologies has largely rendered many of Guedel's classical signs unreliable, his staging system remains a foundational concept in anesthesiology education.

Unpacking the Characteristics of Stage 2

Stage 2, often referred to as the excitement or delirium stage, is the period that begins with the loss of consciousness and lasts until the onset of surgical anesthesia (Stage 3). This phase is characterized by a paradoxical increase in physiological activity, despite the patient becoming unconscious. The central nervous system is inhibited in a non-uniform manner, leading to disinhibition of excitatory pathways. This results in the following defining features:

Excitement and Delirium: Patients may exhibit non-purposeful movements, involuntary struggling, or agitation. This can be distressing for observers but is a normal, albeit brief, response to the anesthetic agents. The amnesia that sets in during Stage 1 typically ensures the patient does not remember this period.
Physiological Instability: The patient's vital signs become erratic. Breathing patterns may become irregular, rapid, or include episodes of breath-holding. There can also be fluctuations in heart rate (tachycardia) and blood pressure (hypertension).
Loss of Reflexes: A key marker of entering this stage is the loss of the eyelid (or eyelash) reflex, where a light touch to the eyelash no longer causes a blink. However, other reflexes, particularly those controlling the airway, remain active and are often hypersensitive.
Increased Risk of Laryngospasm and Vomiting: The hypersensitive airway reflexes during this stage make patients susceptible to laryngospasm, an involuntary closure of the vocal cords. Combined with the risk of vomiting and irregular respiration, this can quickly compromise the patient's airway, posing a significant risk of aspiration.
Eye Signs: In addition to the loss of the eyelid reflex, the eyes may exhibit divergent gaze and reflex pupillary dilation.

Modern Anesthesia: Minimizing the Excitement Stage

With older anesthetic agents like diethyl ether, the transition through Stage 2 could be prolonged and challenging. Modern anesthesiology practices, however, prioritize a rapid and smooth progression past this risky phase using a 'balanced anesthesia' approach. This involves a combination of fast-acting intravenous induction agents, analgesics, and muscle relaxants. The goal is to induce a state of surgical anesthesia (Stage 3) so quickly that the excitement and delirium phase is either significantly shortened or bypassed entirely.

Intravenous Induction Agents: Medications like propofol, etomidate, and ketamine are commonly used to induce general anesthesia. Propofol, in particular, is associated with a rapid onset and less post-operative nausea, helping to facilitate a fast transition to Stage 3.
Premedication: Before induction, patients may receive premedication with benzodiazepines such as midazolam. These medications help to calm the patient and provide amnesia, contributing to a smoother induction process.
Avoiding Airway Stimulation: Anesthesiologists are careful to avoid any airway manipulation, such as placing or removing an endotracheal tube, during Stage 2 due to the high risk of laryngospasm.

A Comparison: Guedel's Era vs. Modern Anesthesia


Feature	Guedel's Era (e.g., using ether)	Modern Anesthesia (Balanced)
Pharmacological Agents	Primarily single agent (e.g., ether).	Combination of intravenous and inhaled agents (e.g., propofol, opioids, sevoflurane).
Induction Speed	Relatively slow, resulting in a more pronounced and prolonged Stage 2.	Rapid, often bypassing or significantly minimizing the experience of Stage 2.
Patient Experience	Likely to experience the full physiological and motor disturbances of Stage 2.	Patients are rapidly transitioned to Stage 3, and the experience of Stage 2 is generally not apparent.
Monitoring	Relied heavily on physical signs like eye movement, breathing patterns, and pupil size.	Relies on sophisticated electronic monitoring of vitals, brain function (e.g., EEG), and end-tidal anesthetic concentration.
Risk Management	Significant risk of airway complications due to prolonged Stage 2.	Risks are minimized through pharmacological agents designed for rapid, stable induction and vigilant electronic monitoring.

List of Key Pharmacological Agents

Modern anesthesiologists utilize a targeted cocktail of medications to ensure a rapid and safe transition through the stages of anesthesia. Here are some of the key agents involved in the induction process to manage or bypass Stage 2:

Propofol: A fast-acting intravenous anesthetic that promotes a rapid and smooth loss of consciousness, helping to limit time spent in the excitement phase.
Etomidate: Another short-acting IV agent used for induction, particularly favored in patients with cardiovascular instability.
Midazolam: A benzodiazepine used for premedication to produce sedation and amnesia before induction begins.
Opioids (e.g., Fentanyl): Administered to provide analgesia and supplement other anesthetic agents.
Neuromuscular Blockers: These medications paralyze muscles, which aids in intubation and avoids muscle contractions during the excitement stage.

Conclusion: The Evolving Landscape of Anesthetic Care

While Guedel's description of the stages of anesthesia was revolutionary for its time, modern pharmacology and monitoring have dramatically changed anesthetic practice. The transition through what is stage 2 of anesthesia is now a carefully controlled and often imperceptible event for the patient. By using a sophisticated combination of fast-acting drugs, anesthesiologists can rapidly and safely guide a patient into surgical anesthesia, minimizing the risks associated with the excitement and delirium of Stage 2. This evolution from relying on physical signs to utilizing advanced pharmacological precision has significantly enhanced patient safety and comfort during surgical procedures. For further reading, resources like OpenAnesthesia provide comprehensive information on modern anesthetic practice.

Frequently Asked Questions

The main characteristics of Stage 2 anesthesia include delirium, involuntary movements, irregular breathing, an elevated and erratic heart rate, and increased blood pressure. The patient has lost consciousness but is physiologically unstable.

Stage 2 is considered dangerous because the patient's airway reflexes are hypersensitive, increasing the risk of laryngospasm (vocal cord closure) or vomiting. The combination of spastic movements and airway issues can lead to aspiration, where stomach contents are inhaled into the lungs.

Today, anesthesiologists use fast-acting intravenous agents like propofol for induction, which allows them to transition the patient to surgical anesthesia (Stage 3) very quickly. Premedication with sedatives is also used to ensure a calmer induction.

Dr. Arthur Guedel's classification, introduced in 1937, was one of the first systematic approaches to monitoring anesthetic depth. It provided a safety framework for anesthesiologists in an era with limited technology, even though modern techniques have made some of its physical signs less relevant.

No, a patient typically does not remember the excitement phase of anesthesia. This is because the amnesia that begins in Stage 1 ensures that the patient has no memory of the events that occur after losing consciousness.

Stage 1, or induction, is the period from the administration of anesthesia until the loss of consciousness, during which the patient is still awake and may feel disoriented. Stage 2 begins after consciousness is lost and is characterized by the excitable, involuntary movements and physiological instability.

Modern practice uses rapid, smooth-acting medications like propofol to bypass Stage 2 quickly. Other drugs, such as benzodiazepines for premedication and opioids for analgesia, are used in a 'balanced anesthesia' approach to ensure a swift and safe transition to surgical anesthesia.

While modern anesthesia relies on advanced electronic monitoring, Guedel's stages remain a foundational teaching concept in anesthesiology. The principles help explain the progression of anesthetic depth, even though the specific physical signs are less reliable with contemporary agents.