DR ROWAN MOLNAR ANAESTHETICS STUDY GUIDE PART 3

Gynaecological laparoscopy

PATIENT WITH POLYCYSTIC OVARIES FOR LAPAROSCOPIC CYSTOTOMIES AS DAY CASE PROCEDURE

HISTORY 25 year old woman Height 165cm, weight 80kg BMI 29.5 Typical PCOS history/findings. Allergies nil Rx: Metformin 0.5G b.d. Previous GA – E/O wisdom teeth – OK O/Ex: Overweight, otherwise

unremarkable.

Common lies told by surgeons - number 2:

“Just a quick laparoscopy”!

What are the issues and risks here?

ANAESTHETIC ISSUES Medical condition Prolonged surgery Laparoscopy/pneumoperitoneum Trendellenberg Analgesia PONV

“QUIET VICTORY”

Largely uneventful anaesthesia/surgery Problems maintaining normocarbia without

excessive airway pressures when head down Mild permissive hypercapnoea, corrected at

end Polymodal antiemetic therapy – no PONV Comfortable on combined analgesia Home as day case. A typical “straightforward” case that was

expected to go well - & did - so is not memorable to anyone but the anaesthetist who worked hard to make it that way.

“THERE ARE A MILLION STORIES IN THE NAKED CITY, THIS IS ONE OF THEM.”

- THE NAKED CITY, US CRIME DRAMA SERIES

The practice, safety & reputation of anaesthesia is built on thousands of such cases – far more so than the glamorous emergency cases & heroic saves.

PART IV: ANAESTHETIC EQUIPMENT& AIRWAY MANAGEMENT

INTRODUCTION TO/OVERVIEW OF THE ANAESTHETIC MACHINE

Consists of three main parts:1. “A cocktail bar”

This is the backbar – which blends piped &/or bottle gasses: O2, N2O & air, and the vapour of (usually one only) volatile anaesthetic agent (liquid) to produce the desired blend.

2. “A delivery service”This is the breathing circuit – which delivers the fresh gas mixture to the patient and removes carbon dioxide. (There are three main classes of circuits – discussed later)

3. “A bunch of hangers on”These are all the ancillaries attached to the anaesthetic machine but not part of its core function: typically suction system, patient monitors, drawers/trays for airway equipment, and a mechanical ventilator for hands-free controlled ventilation.

A NOTE OF CAUTION: Modern anaesthetic machines are complex devices

that require special knowledge to operate. In particular, knowledge of the pharmacology of

inhaled anaesthetic agents is essential. Undetected mishaps can be rapidly fatal. A thorough check prior to use, appropriate for the

particular machine, by an experienced person, is vital.

Some parts of the circuit e.g. filters & hoses, need to be changed after every or certain cases, or a different type of circuit may be selected & attached. An abbreviated re-check must be carried out after any such change.

ANAESTHETIC CIRCUITS

Three principal types:1. Drawover or “semi-open” systems: where non-rebreathing valves

are used to ensure unidirectional flow of gas. Principally now used in resuscitation & field anaesthetic systems, because of the ability to use ambient air instead of (some or even all) pressurised gas supply.

2. Simple or “semi-closed” systems with pressurised fresh gas inflow, reservoir tube & bag in one of several different configurations. (Sometimes called Maplesen systems, after the man who classified & evaluated the different configurations). The patient breathes ‘to & fro’ through the reservoir tube & bag & the system relies on an adequate fresh gas flow to minimise rebreathing. Commonest example: the “Jackson-Rees T-piece (Maplesen “F”)” paediatric circuit.

3. Circle, or closed circuit systems which use one way valves to direct expired gas through a carbon dioxide absorber. This gas can then be supplemented with only enough fresh gas mix to replenish the oxygen and anaesthetic agents taken up, and then rebreathed. This is the commonest type of anaesthetic circuit in modern practice.

REMEMBER:The commonest anaesthetic circuit most medical & nursing staff will ever use is the non-rebreathing resuscitation bag (“Laerdal

bag” or similar) . . .

. . . to give the commonest anaesthetic and resuscitation drug of all: Oxygen

ANOTHER RULE OF THREE:THE TRIAD OF RESUSCITATION

A – AIRWAYB – BREATHING

C – CIRCULATION

Or . . . Alternatively:

(The triad of resuscitation – my own version)1. Air goes in & out2. Blood goes round & round3. Variations on the first two are a BAD

THING

Note that airway always comes first

Airway isn’t everything . . . . . . but without it everything else is nothing.

This is why anaesthetists are good people to have around at a resuscitation – and why a

grounding in anaesthesia is good training for emergencies.

AIRWAY CONTROL – WHY? Prevent obstruction

Anatomical/foreign body Protect against aspiration

Vomit/blood/secretions Permit controlled ventilation

With paralysis/deep anaesthesiaWhere ventilatory support required

Enable special manoeuvrese.g IPPV & PEEP for thoracotomy, laryngeal

surgery with microlaryngeal tube, single lung deflation with double lumen ET tube.

CLASSIFICATION OF AIRWAYS

SUPRAGLOTTIC TRANSGLOTTIC SUBGLOTTIC

Oropharyngeal airway

Orotracheal tube Cricothyrotomy

Nasopharyngeal airway

Nasotracheal tube Transtracheal jet catheter

Laryngeal Mask Airways (various)

Intubating LMA (w/ETT placed thru it)

Tracheostomy

Combitube/PTL * (85% of placements oesophageal)

(Combitube/PTL) - if one of the 15% placed tracheally

THE WINNER, AND STILL CHAMPION:Endotracheal intubation

(usually oral), remains the gold standard for airway management, . . . but . . .

It is also the most difficult to master and carries the highest risk.

Remember: An unrecognised

oesophageal intubation has a 100% mortality

EMERGENCY AIRWAY MANAGEMENT(IN ANAESTHESIA & RESUSCITATION)

Rapid sequence intubation

[or unmodified (“cold”)

intubation if apnoeic & arreflexic]

Other techniques:Fibreoptic intubationSupraglottic airwaySurgical airway

>90% <10%

RAPID SEQUENCE INTUBATION:HOW TO DO IT PROPERLY

Preoxygenation: 3mins or 5 VC breaths. IV induction agent – titrated to effectCricoid pressure – 30N.Suxamethonium 1.5mg/kg (IBW).

or Modified RSI: 0.9mg/kg rocuronium

No bag mask ventilation (unless hypoxic)

Intubation & confirmation of placement (then & only then) Cricoid pressure

released.

Remember (1) : every intubation attempt is a potential failed intubation.

You should always have a backup plan - i.e. a failed intubation drill.

Backup begins even before you start - with preoxygenation for every IV induction

Remember (2): People don’t die of failure to intubate, but of failure to oxygenate

Supraglottic rescue airway e.g. LMA

SUCCESSFUL?

Subglottic (surgical) airway

1. Bag mask ventilation2. Repeat attempt &/or

alternate technique to intubate

SUCCESSFUL?

FIRSTLY MAINTAIN OXYGENATION!

FAILED INTUBATION DRILLCAN YOU MASK VENTILATE? [With Geudels &/or nasopharyngeal

airway if necessary]

NO

NO

YES

NO

NON ENDOTRACHEAL AIRWAYS

There’s more to anaesthetic airways than just ET tubes!

Laryngeal masks (of various types) are the most widely used airways in modern anaesthetic practice:

Classic (original) & its various copies – reuseable or single use.

Reinforced – kink resistant & more flexible upper lumen to permit alternative positioning after insertion for oral/facial procedures.

Proseal - second lumen to communicate with oesophagus & allow drainage of gastric contents or placement of gastric tube.

Intubating – modified shape, more rigid, & lacking apeture bars – to enable passage of a special ET tube through it.

NON ENDOTRACHEAL AIRWAYS II

Advantages of laryngeal masks:

Hands free (compared to face mask/oral airway)

Easier to insert & become proficient at compared to ETT

Tolerated at lighter plane of anaesthesia than ETT.

Good protection against “top” aspiration - of saliva/mucus.

Pressure support & in some cases IPPV can be given.

Disadvantages of laryngeal masks

Less secure airway - more prone to dislodgement than ETT

No protection against laryngospasm

Poor protection against “bottom” aspiration – of gastric contents (Except “Proseal”)

Not guaranteed to permit satisfactory IPPV – especially where high pressures required.

Remember, the traditional facemask/chin lift +/- Geudel’s airway is still an acceptable – possibly even underutilised – technique for short simple cases.