General anesthesia is an irreplaceable adjunct to modern surgery. General anesthesia ensures that patients are unconscious, feel no pain, have no memory of the surgery, remain still during the operation and have adequate autonomic nervous system, respiratory and cardiac responses to keep them alive. Achieving this would be impossible without a variety of drugs. Paralyzing drugs, induction drugs to put a person to sleep quickly, pain medications and inhaled medications to keep patients asleep are all part of surgery in the 21st century.
Intravenous Pain or Amnesia Medications
Intravenous (IV) medications are given directly into a vein. IV medications are used for induction, to sedate people right before surgery and to aid in rapid induction of general anesthesia. Some intravenous agents are administered continuously during surgery along with inhaled gasses. Propofol is often used for induction because it has rapid onset and recovery times and causes little nausea or vomiting. Ketamine produces an amnesia affect that makes the patient appear alert but unable to respond to sensory stimuli, Healthline explains. Ketamine can cause vivid dreams and hallucinations during the postoperative period in adults, the Encyclopedia of Surgery warns. Thiopentol, or pentothal, a barbiturate, works rapidly but accumulates in the liver and can be toxic, so long term infusion isn't used. Pentothal also causes postoperative nausea and vomiting. Sedatives such as fentanyl, sufentanil or alfentanil are used during the induction phase and as a continuous infusion during surgery.
Muscle Relaxants
Muscle relaxants, administered intravenously, are used to keep people still during induction anesthesia and during the surgical procedure itself. Muscle relaxant medications currently used in general surgery block the effects of acetylcholine, which blocks muscle contraction. Succinycholine is quickly metabolized in the body, so its effects last only a short time. Other short acting muscle relaxants include mivacurium and rapacuronium. Pancuroium and d-tubocurarine are longer lasting drugs, while rocuronium, vecuronium and atracurium have an intermediate action time.
Inhaled Vapors
Inhaled anesthetics are usually used in conjunction with intravenous medications, the Encyclopedia of Surgery states. Most inhaled anesthetics are administered via an endotracheal tube that goes down to the throat and delivers the drugs directly to the lungs; this is done because most inhaled anesthetics are irritating to the airway. One type of inhaled anesthetic, sevoflurine, can be given by mask because it doesn't cause irritation. Enflurane produces rapid anesthesia and possibly more rapid recovery than other drugs, but is less potent, and can't be used in patients with kidney failure. Halothane is less effective against pain but has a pleasant odor and may be used for induction anesthesia in children; halothane may cause liver problems in adults. Isoflurane may cause heart arrhythmias and kidney problems. Desflurine, a drug developed from isoflurine, can cause tachycardia, or rapid heartbeat, and shouldn't be used for people with heart problems. Desflurine has a rapid induction and recovery time.
