For Those who are curious about this speciality, or if you’re starting clinical rotations in anaesthesia, this will be the best anaesthesia overview for you to get the bigger picture of anaesthesiology. In this article, we will address all the questions you may have about this field, and more.

What is the purpose of Anaesthesia?

The purpose of anaesthesia is to optimize the patient’s conditions for successful outcome of surgery. Anaesthesia does this by achieving the following states.

• Absence of pain
• Absence of anxiety
• Absence of awareness
• Muscle relaxation
• Maintain homeostasis
  • Haemodynamic stability
  • Oxygenation
  • Ventilation
  • Temperature

The type of anaesthesia chosen will determine how many of the above conditions can be achieved.

Where does anaesthesia team work?

• Operating theatre
• Endoscopy unit
• Interventional radiology unit
• Interventional cardiology laboratory (Cath lab)
  

What are the types of anaesthesia?

General Anesthesia (GA)

Ideal for major surgeries, GA induces a reversible state of surgical anaesthesia with stages ranging from analgesia to medullary depression.

• Major surgeries like open-heart surgery
• Neurosurgery involving intricate procedures
• Abdominal surgeries requiring extensive exploration

Neuraxial Anesthesia

Techniques like spinal or epidural anaesthesia target specific areas, providing localized numbing for surgeries such as lower abdominal procedures.

• Lower abdominal procedures such as hernia repair or appendectomy
• Orthopaedic surgeries like hip or knee replacements
• Labour and delivery for pain management during childbirth

Peripheral Nerve Blocks

Widely used for extremity surgeries, these blocks offer targeted anaesthesia with ultrasound guidance.

• Upper extremity surgeries like carpal tunnel release
• Lower extremity procedures such as knee arthroscopy
• Plastic surgery involving specific nerve territories

Intravenous Regional Anaesthesia (IVRA)

Also known as Bier block, IVRA is an alternative to peripheral nerve blocks for short procedures on the hand and forearm.

• Hand surgery procedures like carpal tunnel release
• Forearm procedures such as fracture reduction
• Minor hand or wrist surgeries like trigger finger release

What are the stages of anaesthesia

Stage	Description
Stage I	Analgesia state: Patient is conscious and rational, with decreased perception of pain.
Stage II	Delirium stage: Patient is unconscious; body responds reflexively; irregular breathing pattern with breath holding.
Stage III	Surgical anaesthesia: Increasing degrees of muscle relaxation; unable to protect airway.
Stage IV	Medullary depression: There is depression of cardiovascular and respiratory centres.

Phase	Description
Induction	Achieved with intravenous or inhalation agents, inducing hypnosis and muscle relaxation.
Maintenance	Continuation of anaesthesia with inhalation or intravenous techniques, often combined to minimize doses.
Emergence	Gradual return to consciousness post-surgery, with careful monitoring until stable for transport.

Level of Sedation/Anesthesia	Responsiveness	Airway	Spontaneous Ventilation	Cardiovascular Function	Clinical Implications
Minimal Sedation (Anxiolysis)	Normal response to verbal stimulation	Unaffected	Unaffected	Unaffected	Provides anxiolysis and minimal sedation for patients undergoing minor procedures
Moderate Sedation/Analgesia	Purposeful response to verbal or tactile stimulation	No intervention required	Adequate	Usually maintained	Induces a state of consciousness where patients can respond to stimuli comfortably
Deep Sedation/Analgesia	Purposeful response following repeated or painful stimulation	Intervention may be required	May be inadequate	Usually maintained	Produces a decreased level of consciousness for more invasive procedures
General Anesthesia	Unarousable even with painful stimulus	Intervention often required	Frequently inadequate	May be impaired	Induces a state of unconsciousness for major surgical procedures

Risk Assessment

Morbidity and mortality risk in the perioperative setting are crucial considerations for patient safety. The American Society of Anesthesiologists (ASA) physical status classification system serves as a valuable tool in assessing these risks. This system categorizes patients based on their overall health and the extent to which underlying medical conditions affect their daily functioning.

The ASA classification system ranges from I to VI, with higher numbers indicating greater health risks. Patients with higher ASA classifications are more likely to experience complications, unexpected hospital admissions following ambulatory surgeries, ICU admissions postoperatively, prolonged hospital stays, increased healthcare costs, and mortality.

ASA PS classification	Definition	Adult examples	Pediatric examples	Obstetric examples
ASA I	Normal healthy patient	Healthy, non-smoking	Healthy, normal BMI	Healthy, normal pregnancy
ASA II	Patient with mild systemic disease	Mild diseases, controlled conditions	Asymptomatic congenital cardiac disease, well-controlled dysrhythmias,	Normal pregnancy*, well controlled gestational HTN, controlled preeclampsia without severe features,
ASA III	Patient with severe systemic disease	Moderate to severe diseases, limitations	Uncorrected stable congenital cardiac abnormality, asthma with exacerbation, poorly controlled epilepsy, insulin dependent diabetes mellitus, morbid obesity, malnutrition, oncologic state, renal failure,	Severe systemic issues, controlled conditions
ASA IV	Patient with severe systemic disease threatening life	Recent heart issues, severe conditions	acute hypoxic-ischemic encephalopathy, shock, sepsis, disseminated intravascular coagulation,	Preeclampsia with severe features, gestational DM with complications or high insulin requirements,
ASA V	Moribund patient not expected to survive without operation	Ruptured aneurysm, multiple traumas	Massive trauma, intracranial hemorrhage with mass effect, patient requiring ECMO, respiratory failure or arrest, malignant hypertension,	Uterine rupture
ASA VI	Declared brain-dead patient undergoing organ donation	–	–	–