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Anesthesia Q & A

Common questions on anesthesia answered by Dr. Alan Lisbon, Executive Vice Chair of Anesthesia at Beth Israel Deaconess Medical Center, and Dr. Todd Sarge, Department of Anesthesia, Critical Care and Pain Medicine at BIDMC.

How does general anesthesia work?

The exact mechanism in which general anesthetics induce unconsciousness and amnesia is unknown. General anesthetics induce unconsciousness by the disruption of normal neuronal pathways in the brain via complex receptor interactions on a cellular level. Recent studies to help elucidate these mechanisms have focused on specific receptors in the brain, including "GABA" and "NMDA" receptors. Recent research has shown that inhaled anesthetics have the ability to disrupt the normally synchronized oscillations of the cortical neuronal pathways.

How do doctors decide how much anesthesia to give you?

Although general dosage guidelines exist for anesthesia medications, the exact dose administered will vary according to the patient's medical history and condition. Patients meet with their anesthesiologist prior to surgery for a thorough history and physical exam. Once in the operating room, the medications are titrated based on the patient's vital signs, such as blood pressure, heart rate, temperature and oxygen level to assess and maintain the appropriate level of anesthesia.

Will I need a breathing tube during surgery?

Not all surgeries require a breathing tube. A breathing tube, or "endotracheal" tube, is a tube that extends from the mouth or nose as well as the larynx (or voice box) and into the trachea. It allows for both the protection of the airway and lungs from secretions as well as providing a conduit to control breathing on a ventilator and the administration of inhaled anesthetic drugs. A breathing tube is generally inserted for surgeries that require complete control of the airway for patient safety and surgical technique. For example, surgery on the hand, foot, arm or leg may not need general anesthesia and airway control with a breathing tube. Rather, such surgery can often be performed safely via sedation with or without local anesthesia while the patient breathes unassisted via their own natural airway. However, surgery on the abdomen, chest or head often requires general anesthesia with complete protection and control of the patient's airway. The need for a breathing tube during surgery should be discussed with your anesthesiologist while discussing the plan of care prior to entering the operating room.

Will the anesthesiologist stay in the operating room during my surgery?

Yes, trained anesthesia personnel are always present with the patient from the time a patient enters the operating room until completion of the surgery, which includes safe transition to the recovery room.

How common is it to be allergic to anesthesia?

"Allergy" or "allergic reactions" denote the body's adverse reaction to a foreign substance, referred to as "allergens". Allergic reactions can range from a simple rash without any significant symptoms to the classic "anaphylaxis". In general, it is extremely uncommon to have a true allergy to anesthesia, with rates quoted anywhere from 1 in 5,000 to 1 in 25,000 patients undergoing anesthesia. It should be noted, however, that the best place to discover an allergy may be under the care of an anesthesiologist in the operating room, where a patient's airway and breathing is often controlled and the drugs required to treat anaphylaxis are readily available.

Another life-threatening reaction to anesthesia is "malignant hyperthermia", which is an adverse hyper-metabolic reaction to specific triggering anesthesia drugs that involves muscle rigidity and severe hyperthermia leading to circulatory collapse if not treated urgently. This reaction is often hereditary and the incidence is quoted as 1 in 5,000 to 1 in 60,000 patients undergoing anesthesia. Medical treatment for malignant hyperthermia now exists and is readily available in all standard anesthetizing locations.

Does anesthesia cause any side effects?

Yes, the most common side effects to the anesthetic drugs are nausea and vomiting. However, patients may experience other unpleasant symptoms, such as sore throat or muscle aches. These effects are often treatable and typically transient, lasting less than 24 hours.

Is it possible that I could wake up in the middle of my surgery?

Awareness under anesthesia is an extremely rare event. Awareness typically happens while the patient is thought to be fully anesthetized and the patient has been administered “muscle relaxants”, which are a type of drug that induce deliberate weakness or paralysis of skeletal muscles throughout the body, including the arms and legs. Several risk factors have been identified that can now be recognized during the history and physical to alter the anesthetic plan and thus reduce the risk of a patient forming memories while under anesthesia.

Several companies have attempted to monitor the depth of anesthesia via “processed EEG” signals from the brain, however, according to the American Society of Anesthesia literature, “At the present time, none of these new technologies has been perfected.” Therefore, no monitor at the present time can replace the presence and vigilance of well-trained anesthesia professionals in the operating room throughout the surgical procedure.

Discussions and education between patients and their anesthesiologists are crucial prior to all elective surgery. More information is available on the ASA website.

Could my medications react with the anesthesia?

Yes, many medications can either interact with the anesthetic drugs that are commonly administered or affect the dose of anesthesia medications that your anesthesiologist would administer. For this reason and others, your anesthesiologist will take a careful history and physical prior to your surgery, including all medications that you are currently taking, and give instructions on which medications should be continued or held around the time of your surgery.

Above content provided by Beth Israel Deaconess Medical Center. For advice about your medical care, consult your doctor.

Posted March 2013

Contact Information

Department of Surgery
Beth Israel Deaconess Medical Center
West Campus, Lowry Medical Office Building
110 Francis St.
Boston, MA 02215
617-632-9581

Contact Information

Department of Anesthesia, Critical Care and Pain Medicine
Beth Israel Deaconess Medical Center
330 Brookline Avenue
Boston, MA 02215
617-667-3112
617-667-7849

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