Learning from Experience – Intra Operative, Chapters 21 and 22

INTRA-OPERATIVE

Chapter 21

LMA in Obese – Hypo ventilation – Hypercarbia – Arrthymias

Dr. Vasanthi Vidyasagaran*

Department of Anaesthesiology, Kauvery Hospital, Chennai, Tamilnadu, India

A 28-year-old man was admitted for Webster’s procedure for bilateral gynaecomastia. He was obese, weighing 130 kg; BMI=36. No history of comorbid illness. All investigations were within normal limits. He was taken up for surgery under general anaesthesia after overnight starvation, premedicated with Glycopyrrolate 0.2 mg, and Fentanyl 100 micrograms.

Plan was to maintain general anaesthesia with LMA, controlled ventilation, and volatile anaesthesia, as it was superficial surgery and patient would remain supine throughout. Anaesthesia was induced with Propofol. Atracurium 60 mg was given, and size 4 LMA was introduced without any difficulty. Cuff was inflated and patient was connected to ventilator with 850 ml TV, 12/min respiratory rate, and anaesthesia was being maintained with nitrous oxide, isoflurane and oxygen.

Oxygen saturations were maintained between 94-96% on FiO2 40%. EtCO2 monitor was not functional. Since anaesthesia had already commenced, and the saturation was maintained, it was decided to go ahead with the procedure. Surgery proceeded uneventfully for about one and a half hours, after which there was a gradual increase in his heart rate which went up to 120/min, and the patient started sweating. ECG showed premature ventricular ectopics and then supra ventricular tachyarrhythmia. Blood pressure went up to 180/110.

Inj. Lignocaine with Adrenalin was being used as infiltration during the procedure and this response was initially attributed to it. Further injections were avoided. Plane of anaesthesia was deepened with another 50-mic fentanyl and increasing percentage of isoflurane. Arrhythmias persisted, and a senior anaesthetist was called for help since the cause of this arrhythmia was not clear. It was made sure that patient was adequately anaesthetized and paralysed. Adenosin and Amiadarone were kept ready. Oxygen was increased to 50%

On auscultation, breath sounds could not be heard at both the lung bases. The LMA was replaced with an 8-size cuffed endo tracheal tube. In the meantime, EtCO2 monitor was brought in and connected.

End tidal CO2 measured 70 mmHg. Ventilation with intermittent alveolar recruitment was done. Rhythm on ECG reverted to sinus, and the rate came down to 100/min, after about 15 min of ventilation.

Surgery was completed. He did not require any anti-arrhythmic, as he responded to good ventilation and wash out of carbon dioxide. He was monitored in the HDU for four hours and did not exhibit any further changes in the cardiac rhythm. Patient recovered without serious sequelae.

Discussion

This could be a case of hypoventilation-induced hypercarbia that had stimulated arrhythmias in an obese young patient, probably precipitated with the injection of lignocaine with adrenalin. There was no hypoxia, because anaesthesiologist had steadily increased FiO2 to 50%.

Controlled ventilation with laryngeal mask is not without complications, particularly in obese individuals even if the patient is in supine position. Hypo ventilation is possible and should be recognised and managed without any delay. Recognition of the cause and treating the complication early is essential. Use of end tidal CO2 monitor is mandatory in all cases. When there is a cardiac event during anaesthesia, the cause must be identified and treated cardiac drugs alone will not solve the issue. This patient responded well to ventilation, and did not require any cardiac drugs.

References

Cheon G, Siddiqui S, Lim T, et al. Thinking twice before using the LMA for obese and older patients: A prospective observational study. J Anesth Clin Res. 2013;4:283.

Maltby JR, Beriault MT, Watson NC, et al. Gastric distension and ventilation during laparoscopic cholecystectomy: LMA-Classic vs. tracheal intubation. Can J Anaesth. 2000;47:622-6.

Hernandez MR, Klock Jr. PA, Ovassapian A. Evolution of extraglottic airway: a review of its history, applications, and practical tips for success. Anesth Analg. 2012;114(2):349-68.

Chapter 22

LMA in Obese – Displacement During Positioning

A 55-year-old woman was posted for a diagnostic hysteroscopy, as a day care procedure. She had no significant comorbidities like diabetes or hypertension. However, she was obese, weighing 120 kilograms, with BMI=36. Her mouth opening was adequate, she had a short neck. Moderate degree of airway difficulty was anticipated.

All other investigations were within normal limits. She was starved overnight and taken up for the procedure under GA at 7am the following day. She received injection Pantoprazole 40 mg IV, injection Ondansetron 4 mg and injection Glycopyrrolate 0.2 mg in preoperative area. She was induced with Propofol and fentanyl.

After confirming good bag mask ventilation, 40 mg Atracurium was given. A size 4 classic LMA was inserted and inflated with 30 ml of air, no leak was heard. Bilateral air entry was good. Mixture of Oxygen and Nitrous Oxide, with Sevoflurane 1-2% was used for maintenance.

After ensuring adequate ventilation, by auscultation, oxygen saturation and EtCO2, the patient was placed in lithotomy position for the procedure. Ten minutes into the procedure, as the cervix was being dilated, there was difficulty in ventilation and patient started bringing up gastric fluid and beginning to aspirate. Immediately the procedure was discontinued, patient was repositioned and thorough oropharyngeal suction applied.

She was intubated with a size 7 cuffed oral ETT. Her heart rate was 120 beats/min and BP = 140/80 mmHg. Oxygen saturations were maintained above 94 with 100% Oxygen. Bilateral air entry was heard, however there were few crepitations on right side and peak pressures remained above 35 mm Hg. Endotracheal toileting was done. Hydrocortisone 100 mg was given. The patient began to recover gradually in next few minutes and the bag compliance returned to normal. Single dose of IV prophylactic antibiotic was given.

Following confirmation of adequate spontaneous attempts, she was reversed with Neostigmine 2 mg and Glycopyrrolate 0.4 mg. Patient recovered without any serious sequelae.

Discussion

This was a case of ‘aspiration of vomit’ in an obese patient under general anaesthesia. It happened despite starving the patient for nearly 6 h, what we would normally assume as adequate time period of starvation before surgery.

Risk groups for this condition include obese individuals, diabetes, trauma, pregnancy, patients with loss of oesophageal tone aggravated by truncal obesity, and hiatus hernia. Surgeries that increase risk are ENT, gynaecological procedures, mobilization of ovary and uterus, and mobilization of bowels. Positioning like lithotomy and head down also increase risk. Dilatation of the cervix or anal dilatation as in fissure surgery, triggers quite a severe vagal response and one has to aware of this while administering general anaesthesia for such patients.

It has become common practice to use LMA for all patients without discretion in many centres. LMA definitely has its place in anaesthetic practice, however it cannot be used as definitive airway in all patients. We need to weigh the pros and cons before using it in a particular patient. If in doubt, securing the airway with endotracheal tube is the safest option.

Currently there is plenty of evidence in literature pointing towards specific complications in the older age group of patients or higher BMI patients. Complications include laryngospasm, inadequate insertion, suboptimal ventilation, bronchospasm, aspiration, desaturation, and conversion to intubation with endotracheal tube. These may be serious and life-threatening events.

Issues to consider regarding LMA

Technique of placing a laryngeal mask airway is important, not to force it in, ensure optimal cuff inflation, not exceeding the recommended limit. Airway must remain clear and not obstructed. Secure it in a way the black line is in line with nasal bridge and weight of the breathing circuit does not malposition it by dragging during change of position for a particular procedure. (eg. lithotomy for hysteroscopy)

LMAs for adults are available in sizes 3, 4, and 5. There are no intermediate sizes, like in paediatric LMA. These do not encompass all anatomical variations in airway observed in the real world. They certainly cannot be used in distorted airways.

LMAs are worthwhile using to tide over difficult airway situations. One must have clear understanding of the indications of using a LMA. It is not a definitive airway in patients during long procedures, or when there are haemodynamic alterations. Practitioners must understand that LMA is not a replacement for endotracheal tube, and should not be used because it is an easier way to secure the airway. Intubation skills are lifesaving and the pride of anaesthesiologists.

Anaesthesia is one of the most humane invention. Be proud to be one.

Skills must be learnt with precision.

References

Cheon G, Siddiqui S, Lim T, et al. Thinking twice before using the LMA for obese and older patients: a prospective observational study. J Anesth Clin Res. 2013;4:283.

Maltby JR, Beriault MT, Watson NC, et al. Gastric distension and ventilation during laparoscopic cholecystectomy: LMA-Classic vs. tracheal intubation. Can J Anaesth 2000;47:622-6.

Hernandez MR, Klock Jr. PA, Ovassapian A. Evolution of extraglottic airway: a review of its history, applications, and practical tips for success. Anesth Analg. 2012;114(2):349-68.

Learning from Experience – Intra Operative, Chapters 21 and 22

INTRA-OPERATIVE

Chapter 21

LMA in Obese – Hypo ventilation – Hypercarbia – Arrthymias

Discussion

References

Chapter 22

LMA in Obese – Displacement During Positioning

Discussion

Issues to consider regarding LMA

References

Journals