General anesthetics

The term “general anesthesia” is likely familiar to you. There is a general understanding that anesthesia allows us to comfortably undergo surgical procedures that would be prohibitively painful and uncomfortable otherwise. In reality, anesthesiology is more complex. The anesthetic drug options and combinations are fairly extensive. This article will expand your knowledge of the general anesthetic drug category and the adjunctive medications used with them. Learn about the different varieties of general anesthetics, as well as their uses, side effects, and costs.

Other general anesthetics and adjuncts

• Isoflurane

• Desflurane

• Nitrous oxide

• Enflurane

• Fentanyl

What are general anesthetics?

While we think of general anesthetics as simply being able to put us to sleep for surgery, they actually have multiple roles to fulfill. In order to enable us to comfortably undergo major surgical procedures, general anesthetics must be able to:

• Induce an unconscious state

• Produce amnesia (loss of memory of events), analgesia (pain relief), and muscle relaxation

• Block our adrenal system response to pain and discomfort

Anesthesiologists are the healthcare specialists who administer these medications. Typically, they will use multiple different anesthetic drugs to accomplish the goals above, and in doing so, they will be able to reduce the dosage of each individual drug and consequently reduce the potential side effects. 

Adjunctive medications are commonly used along with general anesthetics. Some assist in pain relief, while others help with relaxation.

How do general anesthetics work?

Quieting central nervous system (CNS) activity is the basic aim of this drug class. To accomplish this, general anesthetics like the inhaled fluranes, Diprivan and Amidate, exert their effects by activating the natural inhibitors of brain action, such as gamma-aminobutyric acid (GABA). Ketalar works by inhibiting the simulators of brain action, such as N-methyl-D-aspartate (NMDA). They all exhibit a dose-response effect, meaning that the higher their dose, the more beneficial and adverse effects they have.

Anesthesiologists may choose one drug or set of drugs to induce anesthesia at the start of the surgery and utilize a different anesthetic agent or combination to maintain loss of consciousness during the surgery. Differences in side effects and patient characteristics guide the anesthesia team’s decision-making. 

What are general anesthetics used for?

• Surgical anesthesia

Types of general anesthetics

Inhalational anesthetics

The volatile gases or fluranes are capable of inducing anesthesia, but their forte is the maintenance of anesthesia throughout surgery. The harsh taste of some members of this category can often preclude their use when trying to initiate anesthesia. Fortunately, Ultane is not harsh, making it a good option for children undergoing surgery who may have fear of needles. One reason for the flurane’s utility in anesthetic maintenance is that their dosing can be monitored continuously by measuring the concentration of the gas in the patient’s exhaled air. Adding inhaled nitrous oxide to the mix can reduce the amount of flurane gas needed.

Intravenous anesthetics

The intravenous general anesthetics are a mixed bag of options. Diprivan is the most widely used. It works quickly, has few side effects, and can both induce and maintain anesthesia. Add in the fact that it reduces nausea after surgery, and it becomes clear why Diprivan is frequently chosen. Unfortunately, Diprivan can cause blood pressure reductions in some cases. 

When low blood pressure is a particular concern, Ultane and Ketalar can be used for the induction of anesthesia since they tend to increase blood pressure. Ketalar, but not Ultane, can be used for maintenance of anesthesia, too, but typically is not due to the potential for nightmares and hallucinations after it is stopped.

Adjunctive agents

While not general anesthetics themselves, the anesthetic adjuncts can be a critical element to success. In the case of opioids like fentanyl and Ultiva, they help to keep the doses of the general anesthetics lower, improve pain control, and reduce coughing during the insertion of a breathing tube. Xylocaine helps with reducing pain from medication infusions as well as reducing airway spasms during the insertion of a breathing tube. Midazolam, a fast-acting benzodiazepine, can provide relaxation in the minutes prior to general anesthesia.

RELATED: What are local anesthetics?

Who can take general anesthetics?

Can men and women take general anesthetics?

Adult men and women can both take general anesthetics, but an individual’s medical condition prior to surgery may increase the risk of some or all general anesthetic medications.

Can children take general anesthetics?

Children are able to be given inhaled and intravenous anesthetics. Oftentimes, an inhaled agent or an adjunctive medication such as oral midazolam is used to relax the child prior to the insertion of an intravenous catheter. The amount of inhaled flurane gas required for adequate anesthesia is called the minimum alveolar concentration (MAC), and the required maintenance MAC is typically higher for children than adults.

Can seniors take general anesthetics?

In general, seniors are able to use all the anesthetic options. The higher prevalence of coinciding health problems can have a significant effect on the choice of a particular medication for anesthesia.

Can you take general anesthetics while pregnant or breastfeeding?

General anesthetic use during pregnancy should include a risk and benefit discussion about the different medication options, and caution is typically advised before use during breastfeeding.

Are general anesthetics safe?

Black box warnings

None of the common general anesthetics that we have discussed carry the FDA’s highest warning. The adjunctive medications fentanyl, remifentanil, and midazolam carry black box warnings regarding the potential for addiction, profound sedation, and reduced drive for breathing, particularly when used concomitantly.

Recalls

• Ketamine (September 12, 2019)

• Fentanyl (September 12, 2019)

• Midazolam (June 18, 2019)

Restrictions

• Anyone with a history of allergic hypersensitivity reaction to an anesthetic medication should not take that drug or related drugs. 

• Diprivan should not be used if one has had an allergy to eggs, soy, or glycerol. 

• Individuals with a prior history of malignant hyperthermia should not use the inhaled fluranes.

• Caution is advised before using general anesthetics in the setting of heart, lung, kidney, liver disease, head injury, neuromuscular disease, seizure disorder, increased intracranial pressure, low blood pressure, dehydration, bowel or bladder blockage, or alcohol or substance abuse.

• Alternatives to general anesthesia are appropriate when they are able to achieve the anesthesia goal but do so with less risk. These alternatives include local anesthesia and regional anesthesia, both methods where analgesic meds are injected alongside nerves.

Are general anesthetics controlled substances?

Ketamine is a Schedule III controlled substance. The adjunctive medications fentanyl and Ultiva are Schedule II controlled substances, while midazolam is a Schedule IV controlled substance.

Common general anesthetics side effects

The following are common side effects of most general anesthetics. Side effects may vary based on the specific anesthetic or adjunct you receive.

• Heart rhythm problems or high or low heart rate

• Reduced respiratory drive

• Seizures

• Pancreas inflammation

• Kidney problems

• Liver problems

• Blood clots

• High or low blood pressure

• Rash or itching

• Spasm of the larynx or bronchial tubes, or sore throat

• Eye problems

• Nausea or vomiting

• Confusion or delirium

• Abnormal movements

• Shivering, salivating, or dizziness

How much do general anesthetics cost?

A vial of injectable general anesthetics can cost $200, and bottles of inhaled anesthetic can cost $2,000. Fortunately, patients can save on medications with their SingleCare discount card. Before surgery, ask your hospital if they can process your general anesthetics and other medications with your SingleCare card.