Anaesthetics Study Guide

1. Anaesthetics Study Guide UNSW School of Medicine Liverpool Clinical School Year VI Critical Care Rotation Blair Munford, BMedSc, MB,ChB, FFARACS, FANZCA Senior Specialist Anaesthetist, Liverpool Hospital

2. Aims of Anaesthetic Attachment • To understand the scope of the practice of anaesthesia. • To understand the role of the anaesthetist as part of the surgical or procedural team. • To gain exposure to airway management and other procedural skills • To understand the importance of the perioperative process including pre-anaesthetic assessment, investigations, and optimisation. • To understand post anaesthetic care including pain management, and the indications for specialised postanaesthetic monitoring & support. • To revise/enhance key concepts & simple competencies in emergency assessment and resuscitation, including CPR/BLS/ALS. • For those interested, to acquire insight into anaesthetics as a medical career option.

3. Introductory Case Study “Don’t play with that!” … A simple paediatric case - NOT

4. My first ever weekend on duty as an anaesthetics registrar . . . Case transferred from country hospital for theatre: • 3 year old girl, previously well • Mixed total/partial toe amputation (From playing with grandfather’s axe!) • 18 hours ago, fasted since • IV in situ, IV fluids running. • Has had antibiotics/narcotic analgesics. No problem, even for a junior registrar, right?

5. What happened next . . . • To OT as scheduled. • Rapid sequence induction, uneventful anaesthesia. • Extubated near awake at end (in hindsight, too soon) • Vomited undigested food, developed laryngospasm, desaturated. • Re-paralysed, intubated, pharynx sucked out, suction down ET tube – no evidence aspiration • Awoken & re-extubated uneventfully.

6. The lessons from this: • Specific: Beware occult delayed gastric emptying – predictable in hindsight. • General: • There is minor surgery but there is no minor anaesthesia! • Anaesthetic practice is more than just being able to give an anaesthetic – just like being a 747 captain is more than just holding the controls!

7. Part I:Scope & Development of Anaesthetic Practice

8. Imagine a world without anaesthesia . . .

9. What medicine was like prior to the invention of anaesthesia: • Surgical operations performed rarely & only as a last resort. Death was the expected and usual outcome, from shock, haemorrhage, or infection. • When surgery unavoidable, patient was held down by assistants & surgeons operated as fast as possible. The first incision was often deliberately brutal in the hope that the patient would faint, allowing less haste. • No analgesia in labour & interventional/operative obstetrics essentially unknown – except post mortem (original meaning of Caesarean Section)

10. Without anaesthesia . . . • Surgical advances would have been minimal. • Childbirth would remain a major risk for baby and/or mother. • Concepts of intensive care & resuscitation would not have developed. • Pain - acute and chronic - would have remained an inevitable part of life.

11. Without doubt the development of anaesthesia has been one of the top ten medical advances of all time. Some have even ranked it as the most important medical invention ever. Others rank it amongst greatest discoveries of any type in human history.

12. But what is anaesthesia? A state that encompasses (1)analgesia plus (2) arreflexia (muscle relaxation or lack of movement) and (in the case of general anaesthesia) (3) hypnosis; enabling painful or distressing procedures to be performed humanely. This is the “Triad of Anaesthesia”

13. The other triad of anaesthesia THE MISSION IS (in order of importance): • Preserve life • Relieve suffering • Provide optimum conditions for procedure (Any fool can do the third by ignoring the first. Doing the second by ignoring the first is called euthanasia. The art is in being able to provide all three.)

14. Anaesthesia can be: • Cerebral • Sedation/analgesia • General • Inhalational/spontaneous ventilating • Balanced/controlled ventilation • Neuro-interruptive • Local • Regional • Neuraxial (Or some combination of two or more of these)

15. Dissociative Auditory Electrical Hypnosis Acupuncture Classification of Anaesthetics Anaesthesia Alternative General Regional Surface/topical Spontaneous ventilation infiltration Controlled ventilation Nerve/plexus block Intubated Intubated Spinal blocks LMA Epidural: cervical, thoracic, lumbar, caudal Subarachnoid Manual Mask Mechanical Single shot, intermittent, continuous Local anaesthetic, narcotic/adjuvant, combination

16. But wait . . . there’s more:

17. Scope of Anaesthetic Practice • Anaesthesia for surgery • Sedation/anaesthesia for other procedures • Obstetric analgesia/anaesthesia services • Pre-anaesthetic assessment & perioperative medicine • Acute & Chronic Pain Services • Vascular access services: Central venous lines, et al. • Resuscitation: Trauma team/MET/Prehospital • Teaching: Procedural skills/resuscitation/analgesia • Intensive Care practice/cover/support • Operating theatre management/coordination • Critical care transport (It’s a broad church!)

18. Part II:Perioperative Medicine“The way of the future”

19. What is perioperative medicine? “Integrated multidisciplinary management of the surgical or procedural patient’s hospital admission & stay.”

20. Perioperative system includes: • Identification of patient requiring procedure • Referral to perioperative service • Screening for level of workup required • Pre-anaesthetic assessment/plan • Referral & investigations as required. • Admission at appropriate pre-op interval • Post-operative drug/fluid/other therapy • Appropriate post op level of care & stay • Discharge at earliest appropriate point

21. But why? • Minimize unnecessary pre-op bed days. • Minimize preoperative cancellations • Enable more predictable bed occupancy • Minimize pseudo-urgent blood tests & other investigations • Improve post operative care & shorten post operative stay

22. The Pre-anaesthetic Consultation • What? Targeted history & examination, & formulation of anaesthetic/perioperative plan. • Who? Ideally by the anaesthetist for the procedure (not always possible). • Whom? All patients should have some form of this. • When? At the earliest appropriate opportunity (Obviously this varies on a case by case basis) • Why? To enable optimimum pre-anaesthetic preparation, risk minimisation, informed consent, and allaying of anxiety.

23. Pre-operative preparation may include premedication Use if required, not “one size fits all” Aims: • Ameliorate anxiety Usually with a benzodiazepine such as temazepam • Relieve pain– predominantly in the acute setting – usually with narcotics. • Prevent reflux/aspiration - in at risk patient Usually (a) H2 blocker or PPI 6-8 hrs preop if possible, then (b) non particulate antacid immediately preop. • Treat other medical conditions e.g. asthma prophylaxis.

24. Most regular medications are continued, including on the day of surgery Exceptions include: Oral hypoglycaemics Antithrombotic agents (mostly)

25. ASA Physical Status • ASA 1 – Healthy patient • ASA 2 – Mild or controlled systemic disease • ASA 3 – Significant systemic disease • ASA 4 – Severe systemic disease – current or constant threat to life • ASA 5 – Moribund patient unlikely to survive with or without procedure • ASA 6 – Brain dead patient (organ donor) +/- E = Emergency procedure

26. Relevance of this? • Risk stratification • Workload/resource utilisation planning • Remuneration aspects

27. Perioperative (Preanaesthetic) Clinic Surgical clinic Surgeon refers case Nurse Clinic Satisfied with it; decides to send it back to her for mx Decides to further investigate. May cancel, postpone, refer case or decide to do it Checked up, satisfied as fit & suitable Decides to proceed with planned time, date & procedure Not certain;sends only case notes to anaesthetist to review it Not quite satisfied; takes over review & mx

28. The Doctor takes a quick history, leading questions are allowed as major diagnoses should already be known • Asks for hypertension, diabetes, asthma,epilepsy, previous anaesthetics, allergies, complications, medications being used • A quick examination is done, Ix like Xray, ECG, UES & Blood ix are done • ASA categorised, anaesthesia decided • Explained to patient about anaesthetics, risks, PCA & possible complications

29. To postpone the procedure till fully investigated optimised To cancel the procedure To do the planned procedure Based on:History Examination, Investigation . . . Decision:

30. CASE STUDY II Perioperative management

31. Diabetic patient for vascular surgery

32. History • 65 year old man, BMI 35 • Type II DM, 15 yrs, on OHGs, poor control • Smoker 60+ pack years • Hypertension • Hypercholesterolaemia • Ischaemic heart disease • Diabetic nephropathy, (eGFR ~ 30mls/min) For (R) femoro-popliteal bypass

33. What are the issues and risks here?

34. 1.What are the issues and risks here? 2. How can we optimise him preoperatively?

35. 1. What are the issues and risks here? 2. How can we optimise him preoperatively? 3. What are our anaesthetic options & problems?

36. 1. What are the issues and risks here? 2. How can we optimise him preoperatively? 3. What are our anaesthetic options & problems? 4. How do we manage him postoperatively?

37. Part III:Safety & Monitoringin Anaesthesia

38. Safety in anaesthesia is paramount “When it goes right, no-one remembers. . . When it goes wrong, no-one forgets” . . . So the aim is to make anaesthesia as forgettable as possible!

39. Safety Initiatives in Anaesthesia Anaesthetists have been the leaders in safety initiatives in medicine – e.g. : • Privileged reporting & investigation of deaths under or associated with anaesthesia in most states. • Systematic reporting of incidents and near misses • Collegial policies on minimum standards for facilities, equipment, monitoring, staffing, & training. • Publication of algorithms – e.g: difficult airway management; malignant hyperthermia • Simulation & contingency training e.g. difficult airway workshops, emergency management of anaesthetic crises (EMAC) course.

40. Principles of Safety • Recognise risk – pre anaesthetic consultation • Avoid risk if possible – e.g. can procedure be done under LA? • Mitigate risk – optimise patient condition, select safest technique/agents/resources – e.g “cardiac” anaesthetic & postop ventilation. • Plan & be prepared for emergencies – e.g. predrawn emergency drugs, backup airway plan. • Observe/monitor for deviations & crises. • Respond in a timely& appropriate fashion. • Call for help/backup if required.

41. “The price of safety is eternal vigilance” “Clinical observation is the cornerstone of patient monitoring” • ANZCA Policy statements (several) OR . . . “The best patient monitor is still the one between your ears – so make sure it’s switched on”– my take on the above.

42. Basic (all/most patients) Pulse oximetry ECG Noninvasive (cuff) BP Capnography Oxygen concentration Agent monitoring Airway pressures Temperature Others as indicated Invasive arterial BP Precordial stethescope Ventilator alarm(s) Nerve stimulator BIS/entropy Spirometry CVP “Swann Ganz” (PAP) Transoesophageal echo Monitoring in anaesthesia

43. Pulse oximetry • First monitor I put on most patients & first I usually look at. • If this is OK, then patient has a pulse, a survivable blood pressure (at least 60/) and is oxygenating their blood. • But if it’s not right, it’s not very specific – i.e. it may be as simple as a dislodged probe, or as serious as a cardiac arrest. • Doesn’t guarantee tissue oxygenation – may be relatively normal in extreme anaemia, carboxy- haemoglobinaemia, cyanide posoning, etc.

44. Electrocardiogram • Good monitor for: • Arrhythmias/ectopics • Some electrolyte abnormalities (K+ & Ca++) • Ischaemic/strain changes (Provided leads are placed correctly!) • Does not monitor: • Volume status • Cardiac output • Blood pressure Remember: it is entirely possible to die with a relatively normal ECG!

45. Noninvasive arterial blood pressure (NIBP) monitoring • Usually automated • Convenient but not reliable: • Dependant on correct cuff size & position • Not continuous • Usually under-estimates true hyper-& over-estimates true hypotensive values. • Interferes with IV infusions & pulse oximetry • Should not be placed on limb with AV fistula or lymphoedema.

46. Capnography “Gold standard” for verification of ETT placement. Can also give information on: • Dead space/V-Q mismatching • Adequacy of ventilation • Spontaneous respiratory effort during controlled vent’n. • Rebreathing: circuit problems or inadequate gas flow. • Venous return, RV function & pulmonary blood flow e.g. thrombotic, gas or fat embolism

47. Oxygen monitoring • Monitors machine rather than patient. • The only specific monitor of oxygen supply (Other safety features assume/depend on the gas from O2 outlets & cylinders actually being oxygen) N.B. Before adoption/mandating of oxygen monitoring, all reported (& thankfully very rare) “wrong gas” anaesthetic incidents (misconnected pipelines or incorrectly filled cylinders) resulted in the death of the first patient exposed in every case.

48. Anaesthetic agent monitoring • Identifies (hopefully confirms!) anaesthetic agent being used • Measures inspiratory & expiratory concentrations • Expiratory (alveolar) concentration enables calculation of MAC fraction or multiple – i.e. estimation of anaesthetic depth. • Now mandatory when inhalational anaesthetic agents are used.

49. Temperature monitoring • Anaesthesia promotes hypothermia by: • Decreased metabolic rate -> decreased heat production • Redistribution of blood flow -> increased heat loss • Patients may need temperature support • Passive (prevent heat loss) • Active warming: forced air/ heated IV fluids • What you support you must monitor • Ideally monitor core temperature: Nasopharyngeal/oesophageal/bladder/PV Better than Skin/axillary/oral/rectal

50. Airway manometry Usually analogue gauge on circle circuit Monitors inflation pressure With IPPV can help identify: Airway obstruction Bronchospasm Circuit leaks/faults Ventilator monitor Mandatory when mechanical IPPV employed. Usually integrated into ventilator w/automatic activation. High (overpressure) & low (disconnect) functions