What Is Anaesthesia?

It is said that “anaesthesia induction is like a flight taking off”. Your anaesthetist  ensures that you have a smooth take-off, peaceful journey and a safe landing by adjusting the right medicines according to your individual needs. When you’re preparing for your surgery, it is important for you to understand the knowledge, training and role of your anaesthesiologist just like your surgeon.

Anaesthesia means the absence of pain or sensation. Anaesthesiologists also specialise in critical care medicine (caring for the seriously ill) and pain management. 

They ensure your optimal safety before, during and after your procedure working with your surgeon. 


Definition of anaesthesia

The word anaesthesia  is from Greek origin and  it means an absence of sensation, in today’s practice  it can also include a loss of pain (analgesia), muscle relaxation (paralysis), and loss of memory (amnesia). 

Importance of anaesthesia in medical procedures 

Surgical procedures are painful and involve considerable anxiety and distress to the individual . Good anaesthetic care ensures that the transition to and from surgery is smooth and pain-free.

Types of anaesthesia 

All types of anaesthesia keep you comfortable and pain-free during your surgery, medical procedure, or test. But the type you receive will depend on factors like the procedure, your health, and your preference. 

Local anaesthesia

When you are getting  a wound stitched or  undergoing a skin biopsy , a simpler, one-time small dose called local anaesthesia will be used. Possible side effects include allergies, but these are rare. This is often combined with a regional block.

Regional anaesthesia

This is usually done in procedures where it is better for you to be awake and only a part of the body is operated upon. In childbirth, epidurals and spinal anaesthesias are a form of regional blocks, where the mother can actively push the baby out without too much pain.

General anaesthesia

This is the most common form of anaesthesia given to keep you pain-free  and unconscious. The medications are given through an IV line, after which you will drift into sleep. Many regular bodily functions will slow down, so a tube may be put in your throat (intubation) to help you breathe easily.


When your body does not need full general anaesthesia but also requires you to be relaxed and pain-free during the procedure, sedation can be offered. This is usually done with colonoscopies or biopsy procedures. It is given through a vein and recovery is faster than general anaesthesia.

How does anaesthesia work?

Mechanism of action

Pain and other sensory signals are sent from the nerves in the body and perceived by the brain. Anaesthesia temporarily blocks these signals, thereby reducing or eliminating the sensation of pain.  The drugs used target specific receptors in the brain and spinal cord which are responsible for sendinging and receiving nerve signals related to pain perception and consciousness.1

Anaesthesia administration

Preoperative evaluation 

Before the procedure you will be evaluated by your anaesthesiologist to ensure you are fit for it. Since it will directly impact your care, be fully honest about your medical history during the evaluation. Let them know if any of the following applies: 

  • You take any regular medications (supplements or otherwise)
  • You smoke or use marijuana 
  • You drink alcohol
  • If you snore  
  • If you have suffered from  heat stroke 
  • Have any medication allergies
  • Have any chronic illness

Anaesthetic techniques

Depending on the type of block, the anaesthetic is usually given through a vein (at a specific nerve bundle), through inhalation of a gas or through a tube placed in your spine.2

Anaesthesia monitoring

Your anaesthesiologist will monitor your vital parameters (heart rate, blood pressure, oxygen levels, etc.)  as there can be fluctuations due to the surgery or the medication. 

Risks and complications

Common risks

Some common risk factors that will increase your chance of experiencing complications while taking anaesthesia include:

  • Heart disease
  • Allergies to medication
  • Diabetes
  • High blood pressure
  • Kidney problems
  • Lung problems
  • Overweight 
  • Obstructive sleep apnoea (OSA)
  • Substance abuse (smoking, alcohol, marijuana, etc.)

Potential complications

Some adverse effects  of anaesthesia are:

  • Problems with difficult airway and breathing- if you have OSA or snore during sleep, chances are your airway is narrow and you might face additional problems with anaesthesia- like difficulty breathing with a mask or tube, low oxygen levels and delay in discharge and recovery3 
  • Some individuals are prone to malignant hyperthermia- a condition where there  are strong muscle contractions and fever on administration of anaesthesia.4 Do let your doctor know if you have a family history of this  or if you have ever suffered from heat stroke
  • Elderly people or those with a history of brain-related illnesses are prone to postoperative delirium (memory and cognitive decline), which can be avoided with prompt recognition and management5   

Precautions to avoid risks

Take your pre-operative appointment with your anaesthesiologist seriously. Discuss all your past medical problems honestly and follow the pre-operative advice. 

Recovery and postoperative care

Recovery room

In the recovery room the anaesthesiologist  ensures pain relief, monitors your vitals and decides  when it is safe for you to go home.

Pain management

Various strengths of medications are given according to your weight and other criteria during recovery time and after going home to make a smooth transition to recovery.6 

Postoperative complications 

Different complications can occur depending on the type of anaesthesia administered.6  

General anaesthesia

  • Shivering
  • Nausea and vomiting
  • Confusion


  • Headache
  • Back pain
  • Hematoma formation (bleeding beneath the skin)

Local/ regional blocks

  • Local itching/pain
  • Allergic reaction


It is important  to understand the role your  anesthesiologist will have on your  surgical procedure. So work with them by providing your full medical history to the doctor, to ensure a safe procedure and a quick recovery. 

There are four types  of anaesthesia (local, regional and general anaesthesia and sedation) which are given based on the procedure and each have their own side effects and benefits.  Some common side effects are difficulty breathing, malignant hyperthermia and postoperative delirium.  However, your anesthesiologist will carefully monitor you during and after the procedure to ensure that these effects don’t occur.


  1. Son Y. Molecular mechanisms of general anesthesia. Korean J Anesthesiol [Internet]. 2010 Jul [cited 2023 Jul 13];59(1):3–8. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2908224/
  2. Eroglu A, Apan A, Erturk E, Ben-Shlomo I. Comparison of the anesthetic techniques. ScientificWorldJournal [Internet]. 2015 [cited 2023 Mar 27];2015:650684. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4461791/
  3. Rudra A, Chatterjee S, Das T, Sengupta S, Maitra G, Kumar P. Obstructive sleep apnoea and anaesthesia. Indian J Crit Care Med [Internet]. 2008 [cited 2023 Mar 27];12(3):116–23. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2738308/
  4. Rosenberg H, Davis M, James D, Pollock N, Stowell K. Malignant hyperthermia. Orphanet J Rare Dis [Internet]. 2007 Apr 24 [cited 2023 Mar 27];2:21. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1867813/
  5. Whitlock EL, Vannucci A, Avidan MS. Postoperative delirium. Minerva Anestesiol [Internet]. 2011 Apr [cited 2023 Mar 27];77(4):448–56. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3615670/
  6. Horn R, Kramer J. Postoperative pain control. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 [cited 2023 Mar 27]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK544298/
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Tejal Parmar

Dr. Tejal Parmar is a physician with a flair for medical writing working in the oncology emergency department. Having worked in both rural and urban clinical setting, as well as in the non-clinical role as a Medical Science Liaison, she can write while striking a delicate balance in scientific accuracy and plain language. She is currently working for her medical registration to practise in the UK.

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