Session 06S2: Common issues in neuroanaesthesia

Session 06S2: Common issues in neuroanaesthesia

Sunday 3 June, 0900-1030H, Green Room

This session will address common themes encountered in neuroanaesthesia, with the first part on the ‘prone position’ delivered by Dr Basil Matta, Divisional Director of Emergency and Perioperative Care at Addenbrookes Hospital, Cambridge, and Consultant in Anaesthesia and Neuro-Intensive Care Associate Lecturer, University of Cambridge Clinical School, Cambridge, UK.

The word ‘prone’ means ‘lying face-down’. First recorded in 1578, is derived from the Latin pronus: ‘bent forward’” explains Dr Matta. “Prone positioning of a patient under anaesthetic ensures optimum surgical access for a number of procedures, but is not without its risks, which if not fully appreciated have the potential to cause serious harm to patients.”

He will say that an understanding of the changes in physiology and the particular risks associated with the prone position are vital. Common procedures requiring prone positioning include neurosurgery, spinal surgery, pilonidal sinus surgery and other similar colorectal procedures, as well as some types of ankle surgery, for example Achilles tendon repair.

“I will discuss the common types of operation that require prone positioning, and how that position affects patient physiology including neurologic, respiratory, and cardiovascular functions. The specific problems that are often encountered are highlighted and how these should be managed to ensure patient safety,” says Dr Matta. “Practical considerations to comorbidities that increase the difficulty as well as the risks of prone positioning will also be addressed. Particular attention will be paid to complications arising from the prone position such as nerve injuries, pressure related injuries, as well as indirect complications such as ventilation perfusion mismatch and ocular symptoms.”

“Can we truly monitor awareness under anaesthesia?” will be the subject of the second talk by Dr Dana Baron Shahaf, Residency Program Director in the Department of Anaesthesia, Rambam Health Care Campus, Haifa, Israel. Dr Shafaf will say: “Awareness under anaesthesia is a major complication of general anaesthesia. Several EEG-based monitors tried to deal with this outcome. However, when neuromuscular blockers and various anaesthetic agents are used, the indices might be inaccurate.”

She will explain how, due to its low prevalence, it is difficult to study awareness under general anaesthesia. She will discuss a study by her team in which they evaluated recall of awareness of patients under sedation using the Brice questionnaire. Most prevailing indices are based on anterior activity so they evaluated also a new anteriorisation index – termed global index, based on both anterior and posterior activity. Dr Shafaf says: “This global index, contrary to BIS, could separate between patients with or without recall. It was further found that BIS, but not the global index was highly affected by frontal EMG/EOG.”

Possibly due to the above limitations, EEG-based monitors seem to focus on post-operative cognitive deterioration (POCD). Evidence shows efficacy in predicting post-operative delirium (POD), but not POCD. The limitations imposed upon anterior indices by neuromuscular blockers, various anaesthetic agents and furthermore by underlying pathophysiology of cognitive deterioration might impact these results. Thus, Dr Shafaf’s team developed another index based on interhemispheric synchronisation for POCD.  She concludes that “Our interim results suggest that patients undergoing orthopaedic surgery, with a decrease in synchronisation, experience POCD.” More detailed results will be discussed in her lecture.

The final talk on how to evaluate neuronal function during anaesthesia will be given by Dr Michael Malcharek, Head of the Division of Neuroanaesthesia and Intraoperative Neuromonitoring, Klinikum St. Georg, Leipzig, Germany.

Dr Malcharek will explain that the assessment of neuronal function during anaesthesia in the operating room may include a large variety of monitoring procedures (continuous tests) as well as punctual evaluations (mapping).

He says: “This lecture will give an overview about common techniques of neuromonitoring that can be used during anaesthesia – general and regional anaesthesia. Three major issues will be discussed. First, what neuromonitoring methods are required during anaesthesia, and specifically in neuroanaesthesia? The experience from national and international educational programs suggests that there is a need for anaesthesiologists to understand that neuromonitoring is much more than ‘BIS-monitoring’. Whether or not anaesthesiologists are involved in the monitoring performance, it is important to face intraoperative neuromonitoring as multimodal division-extending issue from awake neurologic evaluation to differentiated neurophysiologic assessments.”

He continues: “Secondly, I will look at what techniques in this field anaesthesiologists themselves are able to perform?  Is neuromonitoring an additional exhausting responsibility, or a chance to better understand our target organ?  The third issue will be about experiences from our own division serving specific neuromonitoring for neurosurgical, vascular and orthopaedic procedures.”

Dr Malcharek’s lecture also addresses the great opportunities of neuromonitoring procedures to anaesthesiologists and the need of continuous development and education in anaesthesia routines.