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Anaesthesia Overview

Anaesthesia Overview

Department of Anaesthesia University of Cape Town Anaesthesia Overview

Anaesthetists are responsible for the peri-operative care of a surgical patient. This implies that they should be involved in the pre-, intra- and post- operative management of patients; in consultation with other clinicians, e.g. surgeons, physicians, intensivists, the primary care physician etc.

Outline of an anaesthetic

Each anaesthetic is divided into 3 distinct periods. First is the pre-operative visit where you meet the patient and make a plan and prepare for the anaesthetic. Second is the anaesthetic itself, which is further subdivided into induction, maintenance and reversal of anaesthesia. Last, and never least, is the postoperative or recovery period where the patient returns to full physiological functioning.

Anaesthesia does no good to anybody! Anaesthesia facilitates , i.e. renders the patient and movement free, allowing the surgeon to operate. Anaesthesia may severely effect normal physiological functioning. Anaesthetists are the patient’s guardian during this period, and must endeavour to maintain normal physiological functioning whilst administering the anaesthetic.

1. Pre-operative visit The pre-operative assessment is the subject of a separate tutorial. However, it is important to note that following a pertinent history, examination and perusal of the special investigations; the patient must be fully informed of the attendant anaesthetic risks and given an outline of the journey through the surgical period. This visit includes the orders.

2. Anaesthetic period

A) Pre-induction This comprises the machine, and equipment check, identifying the presence of emergency equipment and drugs and drawing-up the drugs to be used. The patient is prepared for anaesthesia, e.g. by establishing venous access and administering pre-induction drugs.

B) Induction There are many methods to take a patient from wakefulness to anaesthesia, and the technique used is dependent on patient-, medical- or surgical- factors; as well as the knowledge and technical skills of the anaesthetic team. This is a high-risk period. The risks of induction come from equipment and monitor malfunctions, failure to recognise airway problems and untoward reactions to administered drugs; emphasising the importance of the pre-operative visit, meticulous preparation and the equipment check.

C) Maintenance Once the patient has the chosen anaesthetic, be it regional (local) or general anaesthesia; it must be administered adequately to the appropriate level, and maintained until the surgery is complete. The anaesthetist must pay careful attention to the patient and monitor the patient on: (i) Clinical grounds - colour, feel, temperature, pulse volume, auscultation (ii) Non-invasive and invasive monitoring devices and (iii) “Point-of-Care” blood tests. Problems that may arise include peri-operative fluid shifts, blood loss and aggravation of pre- existing medical or surgical conditions.

D) Emergence or reversal The patient is allowed to “lighten”, regain spontaneous ventilation and the ability to maintain their own airway and protective . This may simply mean removing the maintenance drugs, or administering antidotes. Postoperative placement of the patient is important and this may be to: (i) A recovery area or post anaesthesia care unit prior to returning to the ward (or home)

(ii) A high care unit for more intensive monitoring or pain / fluid management or (iii) the intensive care unit (ICU) for further invasive monitoring and organ support.

3. Postoperative period No anaesthetic is complete until the patient is fully recovered from the effects of the anaesthetic drugs. Patients must be monitored until able to cope with all basic physiological functions. is crucial for relieving the patient from discomfort, both physical and psychological. Anaesthesia overview

Aims of anaesthesia

In order to render safe anaesthesia to patients, anaesthetists have developed drugs and techniques to the extent that there are few areas of the human body to which surgeons cannot have access. For general anaesthesia there are three main objectives, and treating each angle of this triad with specific drugs allows a lower total dose of each drug due to synergism and therefore less chance of severe side effects. This is called the TRIAD of ANAESTHESIA. Each point represents a separate issue as follows: HYPNOSIS

ANALGESIA MUSCLE RELAXATION

The TRIAD of ANAESTHESIA

1) Patients want to be awareness free = HYPNOSIS 2) Surgeons want patients to be movement free = MUSCLE RELAXATION 3) Anaesthetist wants the patient to be free = ANALGESIA

1) Hypnosis (a) Psychological Hypnosis Time-consuming Unreliable (only 10 - 30 % of patients can tolerate surgery) Expertise not available (b) Chemical Hypnosis General anaesthesia:  Intravenous anaesthesia - One dose – Induction agent - Continuous – Total intravenous anaesthesia (TIVA)  Inhalational anaesthesia :  Non-anaesthetic agents - All general CNS depressants may cause - , alcohol, phenothiazines,  Neuroleptic anaesthesia - Partial sedation whereby is altered enough to lose comprehension or resistance to procedure Butyrophenones ( or haloperidol)

2) Muscle relaxation (a) Restraints Some patients, once rendered unconscious, are physically restrained to assist the surgeon's view. Be aware of patients' neurovascular bundles to prevent injury. (b) Deep general anaesthesia This can be used alone to prevent movement, but this may result in high doses of drugs causing side effects. (c) Neuromuscular blocking drugs These drugs work on the and are divided into two groups: (a) Depolarising (b) Non-depolarising (d) Local anaesthetics In the correct place and at the correct strength, local anaesthetics are sufficient to cause motor nerve blockade with adequate muscle relaxation for surgery. 2 Anaesthesia overview

3) Analgesia It is preferable to use a multimodal approach to analgesia, combining several methods of pain relief: (a) Simple , e.g. per os, per or intra-venous (Perfalgan®) (b) Non-steroidal anti-inflammatories (NSAIDs) for surgical inflammatory pain, e.g. diclofenac (c) Opiates reduce pain inputs, i.e. inhibit the nociceptive pathway, e.g. . Many routes of delivery, e.g. oral, intramuscular, subcutaneous, transcutaneous, epidural or spinal (d) Local anaesthetics block pain pathways

(e) and / or Noradrenaline , e.g. tramadol

The final aspect, perhaps the fourth angle of an anaesthetic quadrad, is monitoring of the patient. HYPNOSIS

ANALGESIA MUSCLE RELAXATION

MONITORING

4) Monitoring of the anaesthetised patient Clinical Monitors

(1) Wakefulness / Verbal response (1) EEG and processed EEG (2) Pupil signs (i) BIS, Entropy (3) , if spontaneous (ii) Sensory evoked potentials (4) Autonomic activity, i.e. pulse and blood (2) Carotid blood flow pressure (BP) response to surgery (3) Jugular bulb blood flow (5) Motor response to surgery if not paralysed (4) Intracranial pressure Cardiovascular system Clinical Monitors (1) Pulse rate, rhythm, and character (1) ECG – s-T segment analysis (2) Capillary filling and colour (2) Pulse oximeter (O2 saturation and HR) (3) BP, jugular venous pressure. (3) (end-tidal CO2) (4) Auscultation (4) BP, invasive (intra-arterial) or non-invasive

(5) CVP and / or Swan-Ganz (CVP, PAP, PAWP, CO)

(6) Colour flow and / or 2-dimensional doppler (7) Trans-oesophageal echocardiography (TOE) Respiratory system Clinical Monitors (1) Respiratory rate, volume of breaths (1) Airway pressure (2) Inspection (2) Tidal volume (3) Auscultation (3) Respiratory rate (4) (4) Capnography (CO2 output) (5) Inspired concentration (6) () (7) Arterial blood gases

Metabolic / Renal Clinical Monitors (1) Hydration (1) Glucose (2) Temperature (2) Temperature (3) Urine output (3) Electrolytes (4) Arterial blood gases

(5) Haematocrit / haemoglobin Peri-operative fluids (1) Expected fluid deficit (2) Maintenance fluids (3) Unusual losses, i.e. gastro-intestinal (GIT), blood, sweat (4) Third space losses. That volume lost to evaporation and sequestration at site of surgery 3 Anaesthesia overview

Anaesthesia as a specialty

Anaesthetists are peri-operative physicians, who have the task of examining; optimising; conducting the anaesthesia; recovering, and finally managing the postoperative analgesia and monitoring of a surgical patient.

It must be re-emphasised that anaesthesia is not curative, has no inherent benefits (with some exceptions) and merely allows another clinician to perform the cure (the surgeon usually!). This, plus the fact that we remove all protective reflexes and substitute the normal oxygen supply for an artificial one, makes it particularly important that we do no harm. Safety of anaesthesia is paramount!

“Primum non nocere” – Firstly, do no harm

To perform this function, the anaesthetist needs to have certain skills and knowledge over and above the usual clinical and medical skills:  is an important subject, as no other clinician uses the number of potentially lethal drugs as quickly and via the intravenous route as does an anaesthetist  , particularly neurological-, cardiovascular-, respiratory-, renal- and hepatic- physiology are important; as we derange the normal homeostasis with the potent agents at our disposal  A knowledge of Physics is required to manage the increasingly sophisticated equipment  Finally, a detailed knowledge of anaesthesia and surgery for all measure of patients with a plethora of pathological conditions and the knowledge of how surgery may affect the patient, and what the surgeon may require to perform the operation

Scope of practice General anaesthesia is the obvious prime activity of an anaesthetist and dates back to 1846.

Local anaesthesia is commonly used, especially for pain relief, and dates from 1884 for .

Intensive care is a more recent activity of anaesthetists and stems from the 1952 - ‘54 polio pandemic when an anaesthetist used an endotracheal tube and bag ventilation to save a respiratory polio victim.

Pain management is a natural extension of the principles and skills that anaesthetists utilise during surgery; and is used in the post-operative period, the trauma room, the acute pain service and the chronic pain clinic.

Career options After your undergraduate studies you will need to satisfy the HPCSA that you have performed the required 2 months of anaesthesia as an intern, and you may also be expected to perform some anaesthesia during community service. Thereafter there are essentially 4 career options:

a) General practitioner (GP) / medical officer (MO) / other specialties with no anaesthesia.

b) GP / MO with anaesthesia, but no formal training. Currently a large proportion of anaesthesia

services (especially in rural areas) are provided by self-taught / trained GP / MOs. Most supply an adequate service and without them, anaesthesia services in rural areas would collapse; but they have the most problems with preventable anaesthesia-related mortality and morbidity.

c) GP / MO with anaesthesia and formal training. e.g. a Diploma in Anaesthesia – the DA (SA). An alternative to (b) that would improve anaesthesia services in rural areas and probably improve the rate. The DA (SA) is a postgraduate diploma offered by the College of Anaesthetists of the Colleges of Medicine of SA (CMSA). It requires a six-month attachment to an approved major provincial hospital as a MO in anaesthesia under the supervision of an experienced MO or specialist. We highly recommend doing this exam, even if you choose not to pursue a career in anaesthesia. The skills you will learn in 6 months in terms of , management of intravenous fluids and analgesia, etc., will be invaluable.

d) Anaesthesiologist. This requires the usual postgraduate study as a registrar at an academic hospital for a minimum of four years, and two exams – Primary and Final. This permits you to register as a specialist with the HPCSA as a Fellow of the College of Anaesthetists – FCA (SA). Anaesthesiologists may super-specialise in an anaesthesia sub-discipline, e.g. i. Intensive care (registrable sub-specialty – Cert. Critical Care (SA) (Anaes) ii. Paediatric anaesthesia iii. Cardiac anaesthesia iv. Obstetric anaesthesia v. Pain management 4

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