General anesthesia is a medically induced state of unconsciousness characterized by the loss of protective reflexes, amnesia, and analgesia [1.3.2]. It is a complex process managed by a highly trained physician anesthesiologist, who selects and administers a combination of drugs to ensure a patient is safe, unaware, and free of pain during a surgical procedure [1.4.2]. The process involves three main phases: induction (going to sleep), maintenance (staying asleep), and emergence (waking up), each utilizing specific medications [1.4.4].
The Induction Phase: Initiating Unconsciousness
The start of anesthesia, known as induction, is typically rapid. Medications are usually delivered through an intravenous (IV) line, with effects felt within a minute [1.4.4, 1.5.3].
Intravenous (IV) Anesthetics
IV anesthetics are the most common drugs used to begin the anesthetic process [1.2.1].
- Propofol: This is the most widely used IV anesthetic for induction [1.3.1, 1.5.3]. It is favored for its rapid onset, short duration of action, and anti-nausea properties [1.3.2, 1.3.3]. Patients often experience a smooth awakening with fewer "hangover" effects like confusion [1.2.1]. It acts by enhancing the effect of the inhibitory neurotransmitter GABA in the brain [1.2.3, 1.5.2].
- Etomidate: This agent is known for its cardiovascular stability, making it a preferred choice for patients with heart conditions or those who are critically ill [1.5.2, 1.5.4]. Unlike propofol, it has minimal effect on blood pressure [1.5.3]. However, its use is generally limited to induction because repeated doses can suppress adrenal function [1.3.3].
- Ketamine: Unique among anesthetics, ketamine produces a "dissociative" state, where the patient feels detached from their environment [1.3.3]. It provides strong pain relief (analgesia) and stimulates the cardiovascular system, which is useful in trauma or hypovolemic (low blood volume) patients [1.5.4, 1.5.5]. Possible side effects include hallucinations during emergence [1.3.3].
The Maintenance Phase: Staying Asleep
Once the patient is unconscious, the anesthesiologist's goal is to maintain that state throughout the surgery. This is often achieved with a combination of inhaled gases and additional IV drugs [1.2.4].
Inhaled (Volatile) Anesthetics
These agents are delivered as a gas through a breathing mask or a breathing tube inserted after induction [1.4.1]. They allow for fast and precise control over the depth of anesthesia [1.2.1].
- Sevoflurane: A commonly used agent, sevoflurane has a less pungent odor, making it suitable for mask induction, especially in children [1.6.2, 1.2.5]. It allows for a relatively quick emergence from anesthesia [1.6.3].
- Desflurane: This agent provides very rapid awakening, which is advantageous after long surgeries [1.6.5]. However, its pungency can irritate the airway, sometimes causing coughing or laryngospasm, so it is not typically used for mask induction [1.6.2, 1.6.3].
- Isoflurane: An older but still used agent, isoflurane is effective but has a stronger odor and may lead to a slower wake-up compared to newer drugs [1.2.4, 1.6.5].
Adjunctive Medications: The Supporting Cast
General anesthesia is rarely achieved with a single drug. Anesthesiologists use a "balanced" technique, employing a variety of adjunctive medications to achieve the desired effects while minimizing side effects of any single agent.
Opioids
Potent pain-relievers like Fentanyl, Sufentanil, and Hydromorphone are used to manage pain during and after surgery [1.2.1, 1.3.1]. They are a crucial part of providing analgesia but can cause respiratory depression, which is why they are administered under close monitoring [1.3.1, 1.3.3].
Muscle Relaxants (Neuromuscular Blockers)
These drugs, such as Rocuronium and Succinylcholine, are used to induce muscle paralysis [1.3.1]. This is necessary to facilitate the placement of a breathing tube (intubation) and to prevent patient movement during delicate surgery [1.2.1, 1.3.1]. Their effects are reversible, and specific reversal agents are often given at the end of surgery [1.4.5].
Benzodiazepines
Medications like Midazolam are often given before the patient even enters the operating room to reduce anxiety (anxiolysis) and provide amnesia for the events leading up to surgery [1.2.1, 1.3.2].
Comparison of Common Anesthetic Agents
| Medication | Class | Primary Use | Key Advantage | Common Side Effect |
|---|---|---|---|---|
| Propofol | IV Anesthetic | Induction & Maintenance | Fast, smooth onset/offset; anti-nausea [1.2.1, 1.3.3] | Hypotension (low blood pressure) [1.5.5] |
| Ketamine | IV Anesthetic | Induction (esp. in trauma) | Provides analgesia; cardiovascular stability [1.3.3, 1.5.5] | Emergence hallucinations [1.3.3] |
| Etomidate | IV Anesthetic | Induction (esp. cardiac patients) | Minimal hemodynamic effects [1.5.3] | Adrenal suppression with prolonged use [1.3.3] |
| Sevoflurane | Inhaled Anesthetic | Maintenance & Induction | Smooth induction (less pungent); good for pediatrics [1.6.2] | Can depress respiratory system [1.6.1] |
| Desflurane | Inhaled Anesthetic | Maintenance | Very rapid emergence from anesthesia [1.6.5] | Airway irritation, pungent odor [1.6.3] |
The Emergence Phase: Waking Up
As the surgery concludes, the anesthesiologist will stop administering the anesthetic gases and IV infusions [1.4.5]. They may also give medications to reverse the effects of muscle relaxants. The anesthesia care team monitors the patient closely in the recovery room as they slowly regain consciousness [1.4.1, 1.8.2]. Common, temporary side effects upon waking can include drowsiness, nausea, sore throat (if a breathing tube was used), chills, and confusion [1.8.2].
Conclusion
Putting a patient to sleep for surgery is a highly controlled and customized medical process. Anesthesiologists use a diverse arsenal of medications—from rapid-acting IV agents like propofol to inhaled gases, opioids, and muscle relaxants. The specific combination is carefully chosen based on the patient's health, the type of surgery, and the goal of providing a safe, pain-free, and stable anesthetic experience from beginning to end.
For more patient-focused information, you can visit the American Society of Anesthesiologists' resource page: Made for This Moment [1.10.2, 1.10.3].
