Anesthesia

Anesthesia

Anesthesia is a medical procedure employed to control pain during surgery or other operations. Typically it consists of the administration of medication to the patient, and sometime requires monitoring of his or her condition. Also, it may be employed for the control of the heart rhythm and rate, blood flow and pressure, and breathing. In short, it is employed to block pain, to induce relaxation, sleepiness or forgetfulness or to make the patient unconscious during surgery. It is administered and its action on the organism is monitored by a nurse anesthetist or an anesthesiologist.

There may appear complications related to the use of anesthetics in some patients. Generally, Anesthesia is a safe procedure and in modern medicine, these adverse reactions are infrequent and easy to prevent. However, in a number of cases, they may still occur and require immediate medical attention.

Local Anesthetic Toxicity effects include localized and systemic reactions. Local anesthetic medication may be toxic to the brain, which may lead to the onset of seizures and unconsciousness, and to the heart, causing arrhythmia. Arrhythmia resulted as an adverse reaction to anesthetics may prove to be resistant to defibrillation or other regular treatments, and in such cases the patient has a high risk of heart function loss and even death. Most commonly, the symptoms of anesthetic toxicity include nervous system disorders such as confusion, agitation, blurred vision, dizziness, metallic taste, tinnitus and nausea which may rapidly escalate into seizures and cardiac failure.

In the case of Anesthesia performed with muscle relaxant medication, side effects such as hyperkalaemia (elevation of the potassium levels, in some cases severe – especially in patients that have suffered severe burns, neuromuscular disorders or paralysis) may appear. This may cause arrhythmia, which may become life threatening, muscle aches – most common in young patients who resume physical activity soon after the surgical operation, bradycardia (more common in patients who are administered repeat doses), malignant hyperthermia with possible lethal complications in susceptible patients. Also, in patients that suffer from a rare genetic condition called Suxamethonium Apnoea, the neuromuscular blockade can be prolonged for extended periods of time, sometimes even several hours.

Anesthesia Description

There are several types of Anesthesia, which are described in this chapter, along with the situations during which they are employed.

Local Anesthesia is used to cause numbness in a small part of the patient’s body. Typically it is administered through an injection directly into the target area in order to block pain. The patient remains awake for the duration of the procedure, or in some cases he or she is also administered medication that will induce relaxation or sleep. This is generally used in the case of minor medical procedures.

Regional Anesthesia is employed in order to block pain in larger parts of the patient’s body. The anesthetic medicine is injected in key areas such as the spinal cord or major nerves, and the patient may receive additional medication to allow them to sleep or to relax. There are two subtypes in this category: peripheral nerve blocks and epidural and spinal procedures. The peripheral nerve blocks are anesthetic injections near a specific group of nerves or, in some cases, near single specific nerves. These are used to block pain locally, in the part of the body that is supplied by that nerve or nerve group. These are often encountered during medical procedures performed on the arms, hands, legs, feet or face. The epidural and spinal procedures involve administration of anesthetic in the proximity of the spinal cord and the nerves that connect directly to it, and they block pain from entire regions of the body. Such procedures are encountered in the case of medical operations on the legs, hips or belly.

General Anesthesia is a procedure that affects the entire body as well as the patient’s brain. It can be administered through an intravenous injection or through a face mask (the patient breathes the anesthetic in). In such cases, the patient does not feel anything and is completely unaware for the duration. Also, it is common that the patient does not remember the operation and the period of time immediately after it at all.

Anesthesia Related Medication

The most common medicines employed as part of local Anesthesia are Procaine, Amethocaine, Cocaine, Lidocaine, Bupivacaine, Prilocaine, Ropivacaine, Levobupivacaine and Dibucaine. These are agents that block the transmission of nervous impulses while at the same time not causing unconsciousness. They bind to fast sodium channels in an open state, from within.

Among the inhaled agents for Anesthesia, the most common are Desflurane, Halothane, Enflurane, Isoflurane, Sevoflurane and Nitrous Oxide. Also, Xenon is used under certain circumstances, but generally it is a much less common option. The most commonly employed of these are organic liquids with a special formula that rapidly evaporate and thus are easily administered through inhalation, while Xenon and Nitrous Oxide are in a gaseous state at room temperature (and are not included in the gaseous agents category). Ideally, the anesthetic gas or vapor should be bob-explosive and non-flammable, lipid soluble while possessing low solubility in blood gas, with no end organ side effects or toxicity, impossible to metabolize and non-irritant; however at this time no agent possesses all these properties.

Intravenous agents are divided into two groups, opioid and non-opioid. The first category contains a very large number of drugs, the most common of them being barbiturate class medication (Methohexital, Thiopental), benzodiazepines (Midazolam, Lorazepam, Diazepam), Etomidate, Propofol or Ketamine. Opioid anesthetic agents for intravenous use include Fentanyl, Alfentanil, Remifentanil and Sufentanil; other opioid agents have a longer duration of action as well as a longer onset, and are commonly used as part of the post-operative pain relief treatment: Butophanol, Buprenorphine, Hydromorphone, Diamorphine, Levorphanol, Meperidine, Morphine, Methadone, Nalbuphine, Oxymorphone, Oxycodone, Pentazocine.

The muscle relaxant medicines employed during Anesthesia are not directed at relieving pain or inducing unconsciousness. They are generally used after the main anesthetic has taken effect in order to facilitate surgery or intubation by inducing paralysis of the skeletal muscle. Examples of such agents are Succinylcholine, Rapacuronium and Mivacuronium, Cisatracurium, Atracurium, Rocuronium, Vecuronium, Doxacurium, Alcuronium, Gallamine, Pancuronium, Metocurine, Pipecuronium and d-Tubocurarine.