Morbid obesity and anaesthesia

 

Scenario:

·         40 year old man

·         180kg 170cm BMI+++

·         Not known to any doctors

·         SBO requiring urgent laparotomy

 

Issues:

Overall

·      Major comorbidity + major surgery = risky adventure

·      Risky anaesthetic and surgery

·      Risky intra-op and post-op

Obesity itself

·      Airway: difficulty bag-mask ventilation due to obstruction; difficult intubation due to positioning

·      Breathing: difficulty ventilating due to restriction, difficulty oxygenating due to shunt

·      Circulation: difficult vascular access and BP monitoring

·      Logistics: difficulty positioning and transferring

Secondary pathology

·      Airway and breathing: sleep-disordered breathing

·      Circulation: AF, coronary artery disease, cardiomyopathy, cor pulmonale

·      Other: diabetes, GORD

 

Pre-op assessment:

Questions

·      How sick? (for optimization + planning)

·      How big? (for theatre planning)

·      What comorbidities? (for optimization + planning)

·      Expect difficult airway?

Hx

·      HOPC

·      Resp comorbidities (incl SDB)

·      CVS comorbidities (including PHTN, RV dysfx)

·      Prev anaesthetic (esp laryngoscopy grade)

Ex

·      Airway (usual tests)

·      Breathing (lung fields, SpO2)

·      Circulation (HR, BP, peripheral perfusion)

Ix

Blood tests:

·      FBE (polycythaemia? Leucocytosis?)

·      UEC (HCO3, baseline renal fx)

·      LFT (NAFLD?)

·      Blood gas if sick (lactate)

Cardioresp tests:

·      Sleep studies

·      TTE (?PHTN – consider possibility of failed investigation)

 

Intra-op:

Pre-induction

·      Nurse + second anaesthetist

·      Access: 2 x 18g IV and arterial line

·      Monitoring: standard + 5 lead ECG + arterial BP

Induction

Positioning:

·      Hover mat for transfer

·      Oxford ramp + head piecei

Airway:

·      HFNP throughout

1.       Hyperangulated video scope + size 8 ETT + stylet

2.       iGel size 4

3.       BMV with red guedel

4.       Scalpel bougie panic

Drugs:

·      Modified rapid sequence induction

·      Alfentanil 15mcg/kg LBW

·      Propofol 2g/kg LBW

·      Rocuronium 1.2mg/kg LBW

Maintenance

Drugs:

·      Hypnotic: desflurane (fast offset)

·      Reflex suppressant: modified mulimix + titrated fentanyl (and roc if necessary)

·      Other analgesic: paracetamol + parecoxib

Ventilation:

·      PEEP 10cmH2O

·      Delta P <15cmH2O

·      VT 4-8mL/kg IBW

Emergence

Pre-requisites:

·      Check ABC and ABG

·      Recruitment manoeuvre

·      Suction upper airway

·      Bite block

·      Reversal: sugammadex + TOF >0.9 confirmation

·      Eyes opening and obeying commands

Extubation:

·      Onto bed via hover mat

·      Sitting up

·      Pull tube after inspiration

·      Straight onto CPAP 10cmH2O

 

Post-op:

Disposition

·      HDU (risk of SDB)

Analgesia

·      Acute pain service

·      Multi-modal

·      Regional anaesthetic

·      Ketamine infusion

·      Fentanyl PCA