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Medtronic symposium

Anaesthetic issues in bariatric surgery

If general anaesthesia is used, then from the anaesthetist’s viewpoint they should remember the importance of rapid airway control, rapid reversal, avoiding sedation, avoiding respiratory compromise and awareness (NAP5)

At the recent European Obesity Summit in Gothenburg, Sweden, Medtronic hosted a symposium, which included presentations on how to improve outcomes from a sleeve gastrectomy and anaesthetic issues in bariatric surgery.

Jonathan Cousins

Dr Jonathan Cousins, Consultant Anaesthetist, St Marys’ Hospital, London, UK, addressed some of the anaesthetic issues in bariatric surgery, when treating patients with a high BMI with a specific emphasis on maintaining patient safety and reducing morbidity. He said that the best outcomes are the result of optimal pre-, peri- and post-operative planning.

He began by stating that studies, such as the 4th National (UK) Audit Project (NAP4), have shown that obese patients are more likely to experience complications of airway management during general anaesthesia, so regional anaesthesia should also be considered as a suitable alternative.

If general anaesthesia is used, then from the anaesthetist’s viewpoint they should remember the importance of rapid airway control, rapid reversal, avoiding sedation, avoiding respiratory compromise and awareness (NAP5). The Difficult Airways Society (UK) has produced guidance on how best to treat patients when intubation is proving particularly troublesome (See Figure 1).

Figure 1: DAS Difficult intubation guidelines – over (source: https://www.das.uk.com/guidelines/das_intubation_guidelines)

Dr Cousins explained that a laryngoscopy may be required to facilitate tracheal intubation during general anaesthesia, and an enhanced direct laryngoscope (EDL) is useful as it merges direct and video laryngoscopy (VL) into one handheld device. The McGRATH MAC EDL (Medtronic) handheld device helps clinicians be prepared to respond to unanticipated difficult airways faster.

He said that several papers have reported on the usefulness of VL when managing difficult airways. A paper by Yumul et al (Journal of Clinical Anaesthesia 2016) has reported that VL improves the operators view of the glottis, whilst a meta-analysis paper by Yung-Cheng Su (Eur J Anaesthesiol 2011) concluded that VLs are quicker in difficult airways, and a final paper by AM Taylor (Anaesthesia 2013 – Canada) said that the McGrath device improves the view by 1-3 grades of vision.

Another important consideration when anaesthetising obese patients was to change the traditional position to a ‘ramped up’ position. He explained that during induction of anaesthesia, the patient should be positioned in a ramped position with the tragus of the ear level with the sternum, and the arms away from the chest.

“This will improve lung mechanics, thereby assisting oxygenation and ventilation and as a result, maximise the safe apnoea time. Not only does the ‘ramping up’ improve the view at laryngoscopy in the obese patient, but there is some evidence that the addition of positive end-expiratory pressure (PEEP) may further facilitate pre-oxygenation and minimise the time from induction to intubation reducing the risk of oxygen desaturation, should bag-mask ventilation prove difficult,” explained Dr Cousins.

He then addressed the issue of accidental awareness among obese patients and said that NAP5 has reported location, poor dose planning, incorrect use of drugs, airway distraction and the experience of the anaesthetist to be contributing factors. In order to prevent such events, operators should consider theatre induction, video scope airway, total intravenous anaesthesia (TIVA) and depth of anaesthesia (DOA) monitors from the start. One such device is the Bispectral Index (Medtronic) or BIS, that can distinguish brain waves and patterns and turn them into simple numbers that reflect the depth of sedation/anaesthesia.

In discussing drug dosing, he said that it should generally be based upon lean body weight and titrated to effect, rather than dosed to total body weight as much of the excess weight is fat, which has a relatively low blood flow.

With regards to neuromuscular block he cited a study by Lemmens et al (BMC Anesthesiol. 2010 Sep 1;10:15) that assessed the efficacy of sugammadex compared with neostigmine in reversal of profound vecuronium-induced neuromuscular block (NMB) under sevoflurane anaesthesia. The study found that recovery from profound vecuronium-induced block is significantly faster with sugammadex, compared with neostigmine, and neostigmine did not rapidly reverse profound neuromuscular block.

However, additional studies by Martini et al (Br J Anaesth. 2014 Mar;112(3):498-505) and Bloom (Surg Endosc. 2015 Mar;29(3):627-36) showed that deep NMB results in an improved quality of surgical conditions compared with moderate block in retroperitoneal laparoscopies, and deep NMB ameliorates surgical conditions for laparoscopic cholecystectomy by improved visibility and reduction of involuntary movements, respectively.

“My anaesthetic is a balancing act and we do not always get it right, so what I really want to do is to reduce the opioid load I give,” said Dr Cousins. “Therefore, it is important to consider alternatives such as Ketamine, NSAIDs and high dose paracetamol.”

“In conclusion, it is important that the anaesthetist plans carefully with patient safety and reducing post-operative morbidity of paramount importance. It is also vital that we listen to the specific advice when treating obese patients and utilise technologies such as the video laryngoscopy (McGrath) and BIS, as well as adhering to guidelines (‘ramping up’) that can make a significant difference when accessing difficult airways and improving outcomes.”

To read the article, 'Delivering consistent outcomes in sleeve gastrectomy', please click here

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