GENERAL ANAESTHESIA AND FAILED INTUBATION

Transcription

1 GENERAL ANAESTHESIA AND FAILED INTUBATION INTRODUCTION The majority of caesarean sections in the UK are performed under regional anaesthesia. However, there are situations where general anaesthesia (GA) may be required PRE-OPERATIVE ASSESSMENT Risk of failed intubation in the obstetric population is approximately 10 times greater than in non-obstetric population Anaesthetist and obstetrician assess woman before surgery and devise management plan taking individual needs of mother and baby into account Risk factors for difficult intubation Previous surgery or injury to head and neck Previous radiotherapy Snoring suggestive of obstructive sleep apnoea Congenital craniofacial abnormalities History Routine history including complications of previous anaesthesia and surgery Obstetric history (pre-eclampsia, hypertension, diabetes) Smoking and drug allergies Time of last meal/drink Medications Examination A detailed pre-operative airway assessment may assist in predicting difficult intubation, include: dentition, neck movement Modified mallampati classification Increasing grade of mallampati co-relates with higher grade of difficulty at laryngoscopy With woman sitting upright, opening mouth as far as is possible and maximally protruding the tongue. Allocate a class based on what you see at the back of the mouth Class 1 Class 2 Class 3 Class 4 Faucial pillars, soft palate and uvula seen Faucial pillars and soft palate seen Base of tongue masks uvula Only soft palate visible Even soft palate not visible Consent Explain pre-oxygenation and rapid sequence induction including cricoid pressure Explain risks Obtain and record consent

2 PRE-INTUBATION PREPARATION If difficult intubation envisaged, call for senior help Equipment Tipping/tilting theatre table Appropriately checked anaesthetic machine Working suction 2 working laryngoscopes with different size blades Range of endotracheal tubes (ETT) Gum elastic bougie Oro-pharyngeal airways Laryngeal masks Other difficult airway adjuncts as per local protocol (McCoy blades/short handle laryngoscope/video-laryngoscopes/ilma/proseal LMA/Aintree catheter) Be familiar with local difficult airway equipment and check availability of Manujet kit Drugs Ensure the following are available: Thiopentone 500 mg in 20 ml (labelled and dated) Suxamethonium 100 mg in a 2 ml syringe (be aware that higher dose may be needed in obese women) Atracurium 25 mg Atropine 0.6 mg in 2 ml syringe Ephedrine 30 mg diluted to 10 ml Oxytocin 5 units diluted to 5 ml Analgesics, antibiotics and anti-emetics as per local protocol Antacid regimen High-risk (obese women, diabetic women) labouring women ranitidine 150 mg oral 6- hrly Elective lower segment caesarean section (LSCS) ranitidine 150 mg night before and on morning of surgery Emergency LSCS ranitidine 50 mg IV (if not already receiving orally) Sodium citrate: 30 ml of 0.3 M sodium citrate drink within 20 min of anaesthesia for all grade 1 3 GA caesarean section and, if local policy, grade 4 caesarean section INTUBATION Transfer woman to theatre in left lateral position, or with a lateral tilt Confirm sodium citrate and ranitidine have been given, if not, consider IV ranitidine 50 mg slowly after induction Establish free-running IV infusion (in non-dominant hand) compound sodium lactate (Hartmann s) solution with a 16 G (or larger) cannula Position woman supine on table with a 15º left lateral tilt Give appropriate antibiotics according to local practice Pre-oxygenation Pre-oxygenate for 3 min with 100% oxygen via a close-fitting face mask, ensuring sufficient flow to prevent re-breathing Use high flow oxygen (10 L/min) to improve speed of oxygenation of lungs

3 Monitoring ECG Non-invasive blood pressure (NIBP) SpO 2 End tidal CO 2 (ETCO 2 ) Ensure suction working and close to hand Preparation Position head in optimal intubating position If obese woman, use ramped up position When surgeon ready, instruct anaesthetic assistant to apply cricoid pressure Anaesthetic administration Ensure good IV flow and administer a rapid bolus dose of at least 5 mg/kg thiopentone follow with suxamethonium 1 mg/kg Intubate when fasciculation ceased and woman relaxed Inflate cuff check no audible leak around cuff confirm correct placement with auscultation and ETCO 2 release cricoid pressure Once suxamethonium has worn off, give atracurium 0.5 mg/kg Maintain anaesthesia with oxygen and air or oxygen and nitrous oxide with an inhalational agent (isoflurane/sevoflurane) Remember the possibility of patient awareness at all times Intubation hints If in doubt, take it out A smaller ETT may be required in the presence of respiratory tract infection (URTI) or preeclamptic toxaemia (PET) Careful readjustment of applied cricoid pressure can improve view of the larynx Consider using a McCoy laryngoscope Use a short handled laryngoscope to overcome obstruction caused by woman s breasts If resistance faced, use a gum-elastic bougie for an anterior larynx. Rotate 90º anti-clockwise If resistance still present, release cricoid pressure Remember patients do not die from failure to intubate. They can die from prolonged attempts to intubate in the face of hypoxia and from unrecognised oesophageal intubation AFTER DELIVERY Administer oxytocin 5 units IV slowly to mother immediately after delivery. Extra care required in high-risk women who may have cardiomyopathy or are hypovolaemic After cord clamped, give opioid (e.g. fentanyl 100 gm plus morphine 10 mg IV). Alternatively, if epidural in situ, top-up with local anaesthetic and epidural opioid At end of surgery, and if not contraindicated, give 100 mg diclofenac rectally Perform TAP blocks at the end of surgery for post-operative pain relief Prescribe post-operative analgesia as per local policy Extubate woman awake in left lateral position and transfer to recovery room with 4 L/min oxygen via face mask Obese women may benefit from waking up in the upright position Transfer to recovery room Transfer to recovery room for a minimum of 30 min See Recovery guideline

4 FAILED INTUBATION If laryngoscopy or intubation is deemed impossible, institute failed intubation procedure without delay Call for consultant anaesthetist help urgently Consider simple changes in technique (head position, laryngoscope blade, alteration of cricoid pressure) Do not waste time on repeated attempts at intubation, it can turn cannot intubate to cannot ventilate airway Repeated attempts at intubation are associated with increased airway and haemodynamic complications Do not give second dose of suxamethonium Attempt intubation only twice Consider use of oropharyngeal airway, LMA or Proseal LMA if ventilation impossible. Release cricoid pressure to place LMA If it does not compromise ventilation, maintain cricoid pressure once LMA in place Do not turn woman onto her side Ventilate with 100% oxygen with bag and mask If ventilation still impossible, perform cricothyroidotomy Wake woman and consider alternatives (spinal, awake intubation) Decision NOT to wake mother Will depend on the following factors Woman s life at risk: cardiac arrest massive haemorrhage Baby s life at risk: severe fetal distress Infiltration anaesthesia May be considered in severe fetal distress if mother consents and staff are familiar with this technique. Despite adequate ventilation, if you believe woman s life to be at risk, without a protected/definite airway, wake her until senior help arrives Anaesthesia with spontaneous respiration Deepen anaesthesia with sevoflurane (non-irritant) Do not manipulate airway in order to promote airway compromise or induce vomiting Do not attempt intubation through an LMA or fibre optic intubation under these circumstances, as this may result in an obstructed airway, oesophageal intubations, regurgitation, cardiac arrest Remember, cricothrotomy has poor results in inexperienced hands Extubation strategy Ensure senior help has arrived Evaluate general clinical factors that may have an adverse impact on ventilation before extubation Consider a strategy for reintubation if necessary Always perform an awake extubation

5 Follow-up care Document description of airway difficulties encountered (in ventilation and intubation). Include airway management techniques employed Council woman appropriately post-operatively Follow-up for potential complications: oedema, bleeding, tracheal and esophageal perforation, pneumothorax and aspiration ed intubation during rapid sequence induction (RSI) in an obstetric patient Call for help Can awaken Must proceed Maintenance of oxygenation, ventilation Maintenance of oxygenation, ventilation and anaesthesia Do not give 2 nd dose of suxamethonium LMA plma Maintain 30N cricoid force Use plma/ilma/lma/face mask and oral airway Wake woman Proceed to surgery Cannot intubate, cannot ventilate (CICV) situation with increasing hypoxaemia Spontaneous respiration, deepen anaesthesia Analgesia after delivery Rescue techniques for CICV situation