What is the most common complication of general anaesthesia?

September 25, 2025 •

4 min read

While general anaesthesia is incredibly safe today, minor side effects are still very common. With up to 30% of patients experiencing nausea and vomiting post-surgery, it's a frequently discussed issue. But what is the most common complication of general anaesthesia, and what should you be prepared for?

Quick Summary

Postoperative nausea and vomiting (PONV) is the most frequently reported minor complication following general anaesthesia, though a sore throat is also extremely common due to intubation. Many factors can influence the likelihood of these effects, which are typically managed and resolve quickly.

Key Points

Postoperative Nausea and Vomiting (PONV) is Most Common: Affecting up to 30% of average patients and 80% of high-risk patients, PONV is the most frequently cited minor complication of general anaesthesia.
Sore Throat is Also Very Common: The breathing tube used during surgery can cause a sore throat and hoarseness, a frequent but temporary side effect that often resolves within a few days.
Risk Factors Influence Complications: Your risk for complications can depend on factors like age, gender, smoking status, medical history (e.g., heart disease), and the type/duration of surgery.
Serious Complications Are Extremely Rare: While terrifying issues like malignant hyperthermia or anaesthesia awareness can occur, modern anaesthesia techniques have made them exceedingly rare.
Communication and Preparation are Key: Giving your anaesthesiologist a complete medical history and strictly following pre-operative instructions, like fasting, are the best ways to reduce your risk.
Recovery Is Temporary: Most common side effects, like nausea, fatigue, and muscle aches, are temporary and resolve within a few days.

Common Postoperative Side Effects

Though many complications are possible after a procedure requiring general anaesthesia, the most common issues are minor and temporary. The two most frequently reported are nausea and a sore throat.

Postoperative Nausea and Vomiting (PONV)

Postoperative nausea and vomiting (PONV) is widely cited as the most common complication of general anaesthesia, affecting a significant portion of the patient population. Rates can vary, with an estimated incidence as high as 30% in low-risk patients and up to 80% in high-risk patients. This can be distressing for patients and, in some cases, delay hospital discharge.

Several factors contribute to PONV, including:

Patient characteristics: Female gender, non-smokers, and individuals with a history of motion sickness or previous PONV are at higher risk.
Type of surgery: Certain procedures, such as gynecological, ear, and eye surgeries, are associated with an increased risk.
Anaesthetic agents: The specific medications used during and after surgery play a role, particularly the use of postoperative opioids.

Sore Throat and Hoarseness

A sore throat or hoarse voice is another extremely common side effect, resulting from the placement of a breathing tube (endotracheal tube) during surgery. The likelihood and severity of this discomfort are influenced by:

The size of the breathing tube
The duration of anaesthesia
The number of intubation attempts
The patient's age

Symptoms typically subside within a few days, and lozenges or throat sprays can provide relief.

Other Common, Minor Issues

Beyond nausea and sore throats, other minor complications often occur in the immediate recovery period:

Muscle aches: Relaxant medications used during surgery can cause temporary muscle soreness.
Chills and shivering: A drop in body temperature during the procedure can lead to chills as the body warms up.
Drowsiness and fatigue: It is normal to feel groggy and tired for several hours or even days after receiving general anaesthesia.
Temporary confusion or memory loss: Patients, particularly older individuals, may experience temporary delirium or confusion as they wake up.
Itching: This can be a side effect of pain medication, such as narcotics, used during or after surgery.
Dry mouth: Fasting before surgery and the anaesthetic medications can cause temporary dry mouth.

Rare, But Serious Complications

While the vast majority of patients only experience minor, temporary side effects, rare and more serious complications can occur. These risks are carefully managed by anaesthesiologists and are much less common due to modern techniques and monitoring.

Malignant hyperthermia: A rare, inherited reaction to certain anaesthetic drugs that causes a rapid fever and severe muscle contractions.
Anaesthesia awareness: In extremely rare cases, a patient may regain some consciousness during surgery. This is often brief and typically does not involve pain, but it can cause significant psychological distress.
Aspiration pneumonitis: This occurs when stomach contents are inhaled into the lungs, potentially leading to lung inflammation and infection. Fasting instructions before surgery are crucial for preventing this.
Blood clots: Prolonged immobility during surgery can increase the risk of developing deep vein thrombosis (DVT), most commonly in the legs.
Cognitive dysfunction: In some cases, particularly in elderly patients with pre-existing conditions, cognitive issues like memory and learning problems can last longer than a few days.

Preventing and Managing Complications

Anaesthesiologists take numerous steps to prevent and manage potential complications, but patients also play a vital role in their own care. Here are some key recommendations:

Be Transparent with Your Anaesthesiologist: Before surgery, disclose all medical conditions, allergies, medications, and any past issues with anaesthesia. This information allows the anaesthesiologist to tailor a plan to your specific needs.
Follow Pre-Surgery Instructions Carefully: Adhering strictly to fasting guidelines is critical for reducing the risk of aspiration. Your provider will specify when you should stop eating and drinking.
Ensure a Smooth Recovery: For outpatient procedures, arrange for someone to drive you home and stay with you for the first 24 hours. This is essential, as your judgment and reflexes will be impaired.
Stay Hydrated and Rest: Proper hydration and rest can aid recovery and help reduce common side effects like headaches.
Communicate Post-Surgery: Report any concerning or persistent symptoms to your healthcare provider immediately. Timely intervention can prevent minor issues from becoming more serious.

Comparison of Common vs. Serious Anaesthesia Complications


Aspect	Common Minor Complications	Rare Serious Complications
Examples	Nausea, vomiting, sore throat, shivering, muscle aches	Malignant hyperthermia, anaesthesia awareness, aspiration
Incidence	Frequent; affects many patients to varying degrees	Very low; affects a tiny fraction of patients
Severity	Generally low; causes discomfort but not life-threatening	High; can be life-threatening or cause long-term harm
Duration	Typically lasts hours to a few days, then resolves fully	Can have long-term consequences, psychological distress, or permanent injury
Management	Often managed with simple medications or comfort measures	Requires immediate, advanced medical intervention and specialized care

The Anaesthesiologist's Role in Patient Safety

Anaesthesiologists are highly trained medical doctors who specialize in administering anaesthesia, managing pain, and overseeing critical care. They perform a comprehensive risk assessment before any procedure, considering a patient’s full medical history to create an individualized anaesthetic plan. During surgery, they continuously monitor vital signs and adjust medication levels to ensure patient safety and comfort. Their expertise is key to minimizing both common and rare complications and managing any issues that may arise.

For more information on patient safety, visit the Anesthesia Patient Safety Foundation website: https://www.apsf.org/

Frequently Asked Questions

Most minor side effects, such as nausea or drowsiness, typically last for a few hours to a couple of days. In some cases, fatigue or confusion may linger slightly longer, but most people feel close to normal within about a week.

Risk factors include advanced age, obesity, smoking, and certain pre-existing medical conditions like heart disease, lung conditions, diabetes, and sleep apnea. Your risk also depends on the type of surgery and its duration.

Side effects are the common, expected, and usually minor reactions to the drugs, like drowsiness or a sore throat. Complications are more serious and uncommon adverse events, such as a severe allergic reaction or aspiration.

This phenomenon, known as anaesthesia awareness, is extremely rare. Advanced monitoring and modern techniques have significantly reduced its incidence, which is estimated to occur in only 1 to 2 out of every 1,000 surgeries.

Yes, anaesthesiologists can often take preventative measures, especially for high-risk patients. These can include anti-nausea medications administered before, during, or after surgery. Following all pre-operative fasting rules is also critical.

You should provide a complete medical history, including all current health conditions, allergies, and medications you are taking. Mention any previous adverse reactions to anaesthesia or a family history of issues like malignant hyperthermia.

While short-term memory issues and temporary confusion are common, especially in older adults, long-term cognitive decline is generally not caused by a single instance of general anaesthesia. Factors like pre-existing conditions and the surgery itself play a larger role.