Overview of Anaesthesia

M edical G as M oments. FALSE: MGM Strapped Leo the Lion to a Table.

Recorded Sound. Overview of Anaesthesia. A picture containing indoor, dog, small, sitting Description automatically generated.

Recorded Sound. What is an anaesthetist ?. Anaesthetists are perioperative physicians who care for patients before, during, and after their journey through surgery Peri = “around” Implies preoperative care , intraoperative care , and postoperative care Anaesthesiology also extends to pain management (both acute and chronic ) Requires meticulous applied knowledge of both basic and clinical sciences.

Recorded Sound. Constant vigilance. A coffee mug Description automatically generated.

Recorded Sound. Teamwork and Communication essential in theatre: Anaesthetist | Surgeon | Nursing Staff| Porters.

Recorded Sound. …and each member needs to be prepared for battle in differing circumstances and have the appropriate gear!.

Recorded Sound. ALWAYS be prepared!.

Recorded Sound. Types of anaesthesia. GENERAL ANAESTHESIA Unconscious patient: induced, reversible coma May be achieved with intravenous or inhalational drugs Depending on the surgery and/or drugs used, patients may breathe spontaneously or be ventilated artificially Analgesia usually needs to be administered separately LOCAL or REGIONAL ANAESTHESIA A part of the body is rendered insensitive to pain, sensation (and possibly movement) by blocking nerves with a local anaesthetic agent Patient is still fully conscious (although sedation may be given) Specific nerves may be blocked, or whole sections Includes the neuraxial blocks (spinal and epidural) which block the spinal cord.

Recorded Sound. The Triad of General Anaesthesia.

Recorded Sound. The Triad Explained: 1. Hypnosis.

Recorded Sound. The Triad Explained: 2. Analgesia.

Recorded Sound. The triad explained: 3. Immobility.

Recorded Sound. The perioperative journey. INDUCTION MAINTENANCE EMERGENCE.

Recorded Sound. PRE-INDUCTION. Prior to induction, the patient has been assessed, consent checked, the theatre prepared and equipment checked Intravenous access is always sited in adult patients Pre-induction drugs such as sedatives may be given for anxiolysis The patient is connected to monitors and pre-oxygenated Usually an opioid such as fentanyl is given to pre-emptively establish analgesia.

Recorded Sound. INDUCTION. Induction of anaesthesia proceeds either with intravenous or certain inhalational agents Loss of consciousness is confirmed The anaesthetist is now responsible for maintaining the patient’s airway A definitive airway strategy is implemented (mask ventilation or a supraglottic airway or an endotracheal tube) If intubation is required, a neuromuscular blocking agent needs to be administered first and requires time to start working (1-5 minutes depending on the drug used) The airway is secured and checked.

Recorded Sound. MAINTENANCE. Maintenance of anaesthesia is usually by inhalational agents Propofol can be given via infusion instead of inhalational agents Ventilator settings are adjusted (if used) Additional monitoring may be sited or techniques employed (regional anaesthetic blockade to augment analgesia) The surgical area is cleaned and prepared Surgical, nursing, and anaesthetic staff implement the WHO Surgical Safety Checklist and discuss their concerns for the case Surgery proceeds The patient is monitored throughout with the anaesthetist attending to analgesic, physiologic, and surgical requirements as needed.

Recorded Sound. EMERGENCE. Surgery must be concluded and the surgical and nursing teams satisfied Returning control of respiration to the patient is crucial prior to emergence Any muscle relaxant is checked to be reversed (reversal is given for non-depolarizing agents) Respiration and oxygenation must be assessed to be adequate (spontaneous, regular breathing with normal vital signs) The anaesthetic agent is discontinued Airway devices (e.g. ET tubes) are removed either deep or on awakening The patient is assessed on the table for a few moments before transfer onto the trolley.

Recorded Sound. The Depth of Anaesthesia. Too light a plane of anaesthesia can result in the patient becoming aware, or even emerging from anaesthesia Too deep a plane will worsen side-effects of anaesthetic agents Guedel described 4 stages of general anaesthesia : Stage 1: “Analgesia”  from induction to loss of consciousness Stage 2 : Excitatory phase  paradoxical disinhibition (excitement, hiccupping, swallowing, writhing about) Stage 3 : Surgical anaesthesia  eyeballs become fixed, diaphragmatic respiration Stage 4 : Overdose: diaphragmatic paralysis, loss of all reflexes  death The Guedel stages are not typically seen with rapid acting intravenous agents.

Recorded Sound. Progessive loss of reflexes. These occur as anaesthesia deepens: Voluntary control of eye movement Eyelash reflex Lid reflex Swallowing, retching and vomiting Conjuctival reflex Muscular tone Corneal reflex Glottic reflexes and control of respiration Pupillary light reflex.

Recorded Sound. Recovery from anaesthesia. Patients regain consciousness when the anaesthetic agents are discontinued and dissociate from their binding sites in the brain There is no specific antidote to either the inhalational or intravenous anaesthetic agents If muscle relaxation is still present the patient may be fully awake but unable to move  essential to check; some neuromuscular blocking agents require reversal (antidote) Opioid analgesics cause sedation and contribute to the depth of anaesthesia Opioid analgesics also suppress respiration.

Recorded Sound. POSTOPERATIVE PLACEMENT. MAJORITY Most patients will go to the recovery area where they will be monitored before transfer to the ward DAY CASES Some patients may be discharged home from recovery (minor day-case surgery) SPECIAL CARE REQUIRED Critically ill patients may are transferred directly from theatre to the high care or intensive care unit Some patients, though stable, may require extra monitoring or special pain control techniques  post- anaesthetic high care unit (PAHCU).