STH Consultant CPD Updates: Obstetric Anaesthesia

This is the summary of the PowerPoint presentations from April’s consultant CPD teaching programme.

This month’s session provided an update on obstetric anaesthesia  in line with the Royal College of Anaesthetists Matrix.

The following topic was covered by Dr Phil Bonnett (Consultant Anaesthetist, Sheffield Teaching Hospitals NHS Foundation Trust). The aim was to give an overview of obstetric anaesthesia for the non-obstetric anaesthetist. Please click the link for a copy of the presentation.

Obstetric Anaesthesia Update [2B02, 2B05, 2B06]



DAS ASM Ascot 2013: Key Points

A colleague (Dr Bisanth  Batuwitage) recently attended the Difficult Airway Society Annual Scientific Meeting, in Ascot, November 2013.

In order to allow those who were unable to attend the meeting to gain a flavour of the topics covered by the speakers he has kindly created a summary of the key points of each talk.

The RCOA Matrix Codes for each talk are shown along with the details of the speaker.

How we cause and treat airway stenosis (2A01, 3A02): Mr Guri Sandhu, Imperial College/UCL

  • More than 50% of cases of adult laryngotracheal stenosis are due to a period of ventilation on ICU.
  • Incidence is unknown, risk factors: size of tube, cuff pressures, immunity, infection and natures of patients healing biology.
  • The remainder of cases is due to disorders such as Wegener’s granulomatosis, idiopathic subglottic stenosis and sarcoidosis.
  • Nearly two thirds of tracheal reconstructions can be managed endoscopically, the surgeon and anaesthetist need to work closely and utilize shared airway techniques.
  • They usually perform IV induction, give muscle relaxant and ventilate with positive pressure down an LMA.
  • They use a technique of suspension laryngoscopy and supraglottic jet ventilation at high frequency (100 breaths per minute) delivered by an automated device (Mistral/Monsoon, Acutronic systems). This device alarms if the delivered jet or return of gas is obstructed.
  • They prefer this technique as it employs an open breathing system, so there is no need for an airtight connection between the airway and the breathing system. Thus, the trachea can be open with good surgical access and ventilation still maintained

Gas induction for critical airways in adults is pointless (2A01, 2A06): Dr Anil Patel, Royal National Ear, Nose and Throat Hospital

  • When an inhalational induction is commenced in a patient with a severely obstructed airway, despite the application of CPAP and PEEP, induction is slow there are apnoeic periods and the patient often becomes hypoxic and hypercarbic, there are long periods of instability, arrhythmias and episodes of total airway obstruction.
  • Following airway obstruction the patient often does not awaken and relieve the obstruction, apnoea continues and the hypoxia worsens.
  • If this continues in clinical practice the use of positive pressure is required to relieve the hypoxia. Positive pressure ventilation following IV induction and muscle paralysis is physiologically superior to spontaneous respiration in adult stridulous patients with airway compromise due to laryngotracheal stenosis.

Physiological problems with inhalational induction and maintenance of spontaneous ventilation:

  1. Reduction in airflow
  2. Reduction in respiratory drive as anaesthetic depth is increased
  3. Increased collapsibility of the airway
  4. Increased work of breathing
  5. Critical instability at points of narrowing leading to further airway collapse
  6. Reduction in FRC
  • The only mechanisms to counteract these changes in a gas induction are to provide CPAP and PEEP.
  • For non-obstructed adult airways and children this is often enough but for critically obstructed adults airways the application of CPAP and PEEP is not enough to counteract the physiological principles that impair inspiratory airflow and ultimately obstruct the airway.
  • Positive pressure ventilation however produces positive pressure during both phases of ventilation by positive pressure of the bag during inspiration and elastic recoil of the lungs on expiration.

Ultrasound in Airway management (1A03, 2A12): Dr Michael Seltz Kristensen, Righospitalet University Hospital, Copenhagen, Denmark.

Ultrasound hardly penetrates air: as soon as the beam reaches air a strong echo appears, this is seen as a bright white line, this line delineates the border between tissue and air; everything beyond it is artifact. The airway can be visualised with US from the tip of the chin until the mid-trachea and pleura.

Clinical applications of airway ultrasonography:

  1. Screening of difficult airway management
  2. Diagnosing pathology that can affect airway management
  3. Identification of the cricothyroid membrane
  4. Measuring gastric content prior to airway management
  5. Airway related nerve blocks
  6. Prediction of appropriate diameter of ET tube or tracheostomy tube
  7. Differentiating between tracheal and oesophageal intubation
  8. Differentiating between tracheal and endobronchial intubation
  9. Confirmation of gastric tube placement
  10. Diagnosis of pneumothorax
  11. Differentiating between different causes of dyspnoea/hypoxia and pulmonary oedema
  12. Prediction of successful weaning from ventilator
  13. Localisation of trachea and tracheal ring interspaces for tracheostomy and percutaneous dilatational tracheostomy

Dr Kristensen admits that a lot of these techniques are research based although the two that he thought had real potential to have an impact on clinical practice are localising the trachea/cricothyroid membrane when it cannot be identified easily and the detection of a pneumothorax.

His group’s website is

Every Obstetric GA does not have to be a Rapid Sequence Induction (2B05, 3B00): Dr Wendy Teoh, KK Women and Children’s Hospital, Singapore

  • Mallampati score has been shown to increase in pregnancy and labour.
  • In obstetric patients Mallampati class 3 and 4 strongly associate with difficult laryngoscopy, with increased relative risks of 7.6 and 11.3 respectively.
  • The use of “Macintosh-like” videolaryngoscopes (eg C-MAC, McGrath) are being used as a first line device for securing the maternal airway on a routine basis in some units.
  • Increasing reports of supraglottic airways not only used as a rescue device but also for elective cesarean sections (may want to avoid intubating e.g Pre-eclampsia).

Declining use of general anaesthesia in obstetrics: implications for training and strategies for improvement (2B02, 3B00): Dr Ashutosh Wali, College of Medicine, Texas, USA

  • The use of general anaesthesia for cesarean section has decreased from 45% in 1981 to 0.7% in 2005 in the United States. A similar decline over the same period has been seen in the UK, 79% to less than 10%.
  • Lack of exposure of GA for caesarean section resulted in a severe lack of exposure amongst US trainees and many residents graduated without having performed a GA in an obstetric patient.
  • Solutions to the decline include use of a structured advanced airway management rotation, formal repetitive training of difficult airway algorithms on manikins and in the operating room on non-obstetric healthy patients and use of simulation based training.

DAS/OAA Obstetric difficult airway guidelines (1H02, 2B05): Dr Mary Mushambi, Leicester Royal Infirmary

  • Update on the DAS/OAA national obstetric difficult airway guidelines. The project is expected to take around 2 years to complete.
  • Needs to be different to standard DAS guideline due to physiological/anatomical changes of pregnancy, presence of foetus and remoteness of delivery suite theatres in many hospitals.
  • There is currently no national airway guideline in the UK and wide variation in practice.
  • The guidelines working party of the OAA published six example guidelines on their website having invited hospitals to submit their local guidelines.

STH Consultant CPD Updates: Obstetrics

This is the summary of the PowerPoint presentation from the new consultant CPD teaching programme.

This month’s session provided an update on obstetric anaesthesia (for the non-obstetric anaesthetist) in line with the Royal College of Anaesthetists Matrix.

The following areas were covered by Dr Ian Wrench (Consultant Obstetric Anaesthetist, Sheffield Teaching Hospitals NHS Foundation Trust). Please click the link for a copy of the presentation. Obstetric Anaesthesia for Non-obstetric Anaesthetists

  • Assessment of the critically ill parturient (2B06)
  • Analgesia for labour (2B01)
  • Regional anaesthesia complications in the pregnant patient (2B04)
  • Regional & general anaesthesia for emergency & elective LSCS (2B02, 2B03)

Antacids for LSCS

Roberts RB, & Shirley MA. Reducing the risk of acid aspiration during cesarean section. Anesthesia & Analgesia 1974; 53: 859-868.

RHH Journal Club. June 6th, 2013. Dr Susan Yeung

Full-text article (if available)

This paper from 1974 highlights the increased risk of aspiration in pregnant women undergoing caesarean section (CS). This has led to a change in practice whereby all women prior to elective or emergency section are given antacid prophylaxis.

Read more…

Bad news for rabbits & pregnant ladies…

Mendelson CL. The aspiration of stomach contents into the lungs during obstetric anesthesia. Anesthesiology 1946; 7: 694-695.

RHH Journal Club. May 31st, 2012. Dr Sireesha Aluri 

No free full-text available

To describe the presentation, pathology, diagnosis, prevention and management of aspiration pneumonia.

Read more…

A tale of IVC, CO & the magical 15 degrees…

Lees MM, Taylor SH, Scott D & Kerr MG. A study of cardiac output at rest throughout pregnancy. BJOG: An International Journal of Obstetrics & Gynaecology 1967; 74: 319-328.

RHH Journal Club. December 22nd, 2012. Dr Maneka Braganza

No free full-text available

To describe the overall pattern of change in cardiac output during pregnancy .

Read more…