General Anesthetic Agents
GENERAL ANESTHETIC AGENTS
GENERAL ANESTHETIC AGENTS – INTRODUCTION
General anesthetics are drugs used either by the intravenous route or by inhalation that render the subject unconscious and incapable of perceiving pain such as might otherwise occur in surgery.
GENERAL ANESTHETIC AGENTS – INDICATION
General anaesthesia is essential for some surgical procedures where it may be safer or more comfortable for you to be unconscious. It’s usually used for long operations or those that would otherwise be very painful.
GENERAL ANESTHETIC AGENTS – INFORMATION
General anesthesia (GA) is the state produced when a patient receives medications for amnesia, analgesia, muscle paralysis, and sedation. An anesthetized patient can be thought of as being in a controlled, reversible state of unconsciousness. Anesthesia enables a patient to tolerate surgical procedures that would otherwise inflict unbearable pain, potentiate extreme physiologic exacerbations, and result in unpleasant memories.
The combination of anesthetic agents used for general anesthesia often leaves a patient with the following clinical constellation:
- Unarousable even secondary to painful stimuli
- Unable to remember what happened (amnesia)
- Unable to maintain adequate airway protection and/or spontaneous ventilation as a result of muscle paralysis
- Cardiovascular changes secondary to stimulant/depressant effects of anesthetic agents
General anesthesia uses intravenous and inhaled agents to allow adequate surgical access to the operative site. A point worth noting is that general anesthesia may not always be the best choice; depending on a patient’s clinical presentation, local or regional anesthesia may be more appropriate.
Anesthesia providers are responsible for assessing all factors that influence a patient’s medical condition and selecting the optimal anesthetic technique accordingly.
Advantages of general anesthesia include the following:
- Reduces intraoperative patient awareness and recall
- Allows proper muscle relaxation for prolonged periods of time
- Facilitates complete control of the airway, breathing, and circulation
- Can be used in cases of sensitivity to local anesthetic agent
- Can be administered without moving the patient from the supine position
- Can be adapted easily to procedures of unpredictable duration or extent
- Can be administered rapidly and is reversible
Disadvantages of general anesthesia include the following:
- Requires increased complexity of care and associated costs
- Requires some degree of preoperative patient preparation
- Can induce physiologic fluctuations that require active intervention
- Associated with less serious complications such as nausea or vomiting, sore throat, headache, shivering, and delayed return to normal mental functioning.
Associated with malignant hyperthermia, a rare, inherited muscular condition in which exposure to some (but not all) general anesthetic agents results in acute and potentially lethal temperature rise, hypercarbia, metabolic acidosis, and hyperkalemia.
With modern advances in medications, monitoring technology, and safety systems, as well as highly educated anesthesia providers, the risk caused by anesthesia to a patient undergoing routine surgery is very small. Mortality attributable to general anesthesia is said to occur at rates of less than 1:100,000. Minor complications occur at predicable rates, even in previously healthy patients. The frequency of anesthesia-related symptoms during the first 24 hours following ambulatory surgery is as follows:
- Vomiting – 10-20%
- Nausea – 10-40%
- Sore throat – 25%
- Incisional pain – 30%
How general anaesthetics are given
Before having an operation, you’ll meet a specialist doctor called an anaesthetist to discuss which anaesthetic is most suitable for you.
Your anaesthetist will look at your medical history and will ask whether anyone in your family has had problems with anaesthesia. They’ll also ask about your general health and lifestyle, including whether you:
- have any allergies
- smoke or drink alcohol
- are taking any other medication
Your anaesthetist can answer any questions you have. Let them know if you’re unsure about any part of the procedure or if you have any concerns. You should be given clear instructions to follow before the operation, including whether you can eat or drink anything in the hours leading up to it.