Anesthesia was first successfully demonstrated by William Morton who was an American dentist and he administered ether to a patient for his neck. That also gave the surgeons enough time to improve their surgical expertise which wasn’t possible previously. Earlier, patients were anesthetized using opium and alcohol. But the incomplete numbness allowed only a limited number of operations to be carried out. It is a field of medicine and surgery which ensures pain relief during surgical procedure as it renders patient unconscious. Save surgical procedure is achieved by teamwork between surgeon and anesthetist. But before anesthesia induction, fitness of patient for anesthesia is checked. There are different types of anesthesia which General anesthesia, local anesthesia and Regional anesthesia. Commonly used agents for anesthesia are given through intra venous routes and include propofol, thiopentone and ketamine.

General Anesthesia

General anesthesia is commonly defined as an amalgam of temporary muscle paralysis, loss of memory and relief from pain. Its cardinal features are analgesia, amnesia, immobility and skeletal muscles relaxation. The patient is asked about BMI, medical history and general lifestyle that include smoking and alcohol intake. Its induction is mainly initiated through agents injected into veins and most commonly used agent is propofol. It is also induced through inhalation induction especially in children because these have a higher risk of developing airway obstruction. Maintenance of anesthesia, on the other hand, can be done using continuous administration of intravenous agents like propofol. General anesthesia results in loss of tone and paralysis of muscles so the patient cannot maintain his airway. Therefore, artificial ways are used to keep airway obvious for breathing e.g. endotracheal tube and oxygen masks. Muscle relaxation is achieved by blocking transmission of signals from neurons to muscles. The agents used for this purpose are muscle relaxants, most commonly used agent is Suxamethonium. General anesthesia requires following monitoring before and during surgery: ECG, blood pressure and oxygen saturation by pulse oxymeter. It is essential to note that general anesthesia may not always be the best option, depending upon the condition of patient, local or regional anesthesia may be a better alternative.

Local Anesthesia

Local anesthesia is a combination of anesthesia and analgesia (pain relief) as sole agents or as an addition to general anesthesia. Cocaine was the first anesthetic used in the category. Nowadays, lidocaine is commonly used agent. Available options under this category are topical anesthesia, local anesthesia, nerve block of a particular region and central block like spinal anesthesia. Complications attributed to this are also local like infection, accumulation o blood at injection site but they may be systemic like due to drug over dose. It is a common practice to use adrenaline along with local anesthesia solutions. Its advantages are hastening of onset of action of local anesthesia, prolonged duration of action and a low dose of anesthesia. However its use is contraindicated in patients with heart diseases. Dental surgery, removal of a mole, cataract surgery and biopsies are common examples where local anesthesia is administered.

Regional anesthesia

Regional anesthesia is the use of local anesthetics to block pain from a relatively larger area of the body usually arm or leg. Types of regional anesthesia include spinal anesthesia (also called subarachnoid block), epidural anesthesia, and nerve blocks. Epidural anesthesia is mainly used for pain relief during labor. Spinal block is preferred in lower abdominal surgeries including C sections. Local nerve block is used for local minor procedures like cautery of warts. An interesting use of local anesthesia is chronic pain relief in which agents is injected around inflamed nerve to reduce pain.

General Anesthesia VS Local Anesthesia

Site of action:

General anesthesia acts around central nervous system.

Local anesthesia acts around nerves only.

Area affected:

General anesthesia takes control of whole body.

Local anesthesia is used to numb a specific area.

Conscious status:

General anesthesia renders patient unconscious.

In local anesthesia, patient is fully awake.

Classification:

GA

Inhalation: Nitric oxide

Volatile liquid: Halothane

IV:  Benzodiazepam

LA

Injectable:
  • Short duration: Procaine
  • Intermediate duration: Lidocaine
  • Longer duration: Tetracaine
Topical:
  • Soluble: Cocaine
  • Insoluble: Benzocaine

Mechanism of action:

General anesthesia suppresses the CNS directly.

Local anesthesia inhibits conduction and generation of nerve impulses.

Uses:

General anesthesia is used for major surgical procedures.

Local anesthesia is used for minor procedures.

Preanesthetic medications:

Required in GA and not in LA.

Risk factors:

General anesthesia is usually safe but carries high risk in elderly patient and emergency operation. It includes vomiting, cold and shivers, confusion and memory loss, dizziness and bladder issues.

Local anesthesia has minimum side effect that are blurred vision, dizziness, vomiting, headache and muscle twitching.

Complications:

General anesthesia may cause

  • anaphylaxis
  • laryngeal damage
  • cardiovascular collapse
  • respiratory distress
  • brain damage

Local anesthesia may rarely cause:

  • CNS suppression which may lead to cardiac arrest
  • Seizures due to overdose

Conclusion

Anesthesia is a great invention in field of medicine which has ensured major surgical procedures safely without any trouble or discomfort.

http://www.anzca.edu.au/about-anzca/history-and-heritage/history-of-anaesthesia

https://www.asahq.org/whensecondscount/anesthesia-101/types-of-anesthesia/general-anesthesia/

https://www.medicalnewstoday.com/articles/265592

https://www.medicalnewstoday.com/articles/265689

https://jamanetwork.com/journals/jama/fullarticle/1104234