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DR ROWAN MOLNAR PART II: PERIOPERATIVE MEDICINE“THE WAY OF THE FUTURE”
WHAT IS PERIOPERATIVE MEDICINE?
“Integrated multidisciplinary management of the surgical or procedural patient’s hospital admission & stay.”
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
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
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.
PRE-OPERATIVE PREPARATION MAY INCLUDE PREMEDICATION
Use if required, not “one size fits all”Aims:
1. Ameliorate anxiety Usually with a benzodiazepine such as
temazepam2. Relieve pain – predominantly in the acute setting –
usually with narcotics. 3. 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.
4. Treat other medical conditionse.g. asthma prophylaxis.
MOST REGULAR MEDICATIONS ARE CONTINUED, INCLUDING ON THE DAY OF SURGERY
Exceptions include:(a) Oral hypoglycaemics(b) Antithrombotic agents (mostly)
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
RELEVANCE OF THIS? Risk stratification
Workload/resource utilisation planning
Remuneration aspects
PERIOPERATIVE (PREANAESTHETIC) CLINIC
Surgical clinic
Nurse Clinic
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
Satisfied with it; decides to send it back to her
for mx
Not quite satisfied; takes over review & mx
Decides to further investigate. May cancel, postpone, refer case or
decide to do it
Surgeon refers case
Preanaesthetic Clinic
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
Preanaesthetic ClinicBased on: HistoryExamination, Investigation . . .Decision:
To do the planned
procedure
To postpone the procedure till fully
investigated optimised
To cancel the procedure
CASE STUDY II
Perioperative management
DIABETIC PATIENT FOR VASCULAR SURGERY
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
What are the issues and risks here?
1.What are the issues and risks here?
2. How can we optimise him preoperatively?
1. What are the issues and risks here?
2. How can we optimise him preoperatively?
3. What are our anaesthetic options & problems?
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?
PART III: SAFETY & MONITORINGIN ANAESTHESIA
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!
SAFETY INITIATIVES IN ANAESTHESIAAnaesthetists 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.
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.
“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.
MONITORING IN ANAESTHESIABasic (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
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.
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 pressureRemember: it is entirely possible to
die with a relatively normal ECG!
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.
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
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.
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.
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
Airway manometry
Usually analogue gauge on circle circuit
Monitors inflation pressure
With IPPV can help identify:Airway obstructionBronchospasmCircuit leaks/faults
Ventilator monitor
Mandatory when mechanical IPPV employed.
Usually integrated into ventilator w/automatic activation.
High (overpressure) & low (disconnect) functions
Precordial stethescope
“Traditional” monitor Still used in some
paediatric cases Can monitors:
Heart & respiratory rateBreath sounds presence
& quality.Only as good as the
person listening to it!
Direct arterial pressure
monitoringInvasive procedure,
but: Gold standard for real
time haemodynamic assessment
Accurate, reliable. Immediate warning
of hypo/hypertension of any aetiology.
Nerve stimulator
Used with muscle relaxants (neuromuscular blockers):
Electrical stimulus to nerve then observation of innervated muscle.
Commonest site: Ulnar nerve Nondepolarising block
characterised by “fade” – weakening of contraction with (4) successive impulses “train of four.”
Assesses: - Density of block
- Return of function- Point of safe reversal
Depth of Anaesthesia monitoring
Uses simplified EEG recording & algorithm to produce number related to level of conciousness (lower no=deeper anaesthesia)
Two methods: bispectral edge (“BIS”) and entropy.
Role/value still controversial Probably indicated for:
TIVA (as no MAC to monitor)
Patient with a history of awareness
Where lightest possible plane of anesthesia essential
OTHER MONITORS Central venous line.
- Mostly used for drug infusions but can also measure CVP as a (not very accurate) guide to volume status.
Pulmonary artery (Swann Ganz) catheter- Can estimate LV filling
pressure (preload) – a better guide to functional volume status than CVP
- Also can measure cardiac output by thermodilution.
Trans-Oesphageal Echo-cardiography (TOE)Has become the gold standard
cardiac function monitor. Able to estimate:
- Ejection fraction/stroke volume/cardiac output
- LV & RV Preload/pressures- Diastolic dysfunction (early
index of ischaemia) Spirometry
Measurement of pressure volume loops & hence work of breathing in controlled, spont. & ass’t’d ventilation