anesthesia research

Clinical Topic: Effects of Cervical Collar on LMA seal

Supraglottic airway devices have proven to be an acceptable alternative to endotracheal intubation and easier to insert by the less experienced provider. As a result, paramedics and other first line responders are using the laryngeal mask airway more frequently to ensure an open airway while en route to definitive care. In addition to inserting the LMA, a cervical collar is commonly placed on the injured person. It is known that movement of the head and neck can affect the cuff pressure of the LMA, however, the effect of a cervical collar on the cuff pressure is unknown.

In a study by Mann, V et al published in Anaesthesia, 2012 (The effect of a cervical collar on the seal pressure of the LMA Supreme™: a prospective, crossover trial.) the authors examined the effect of a cervical collar on the cuff pressures within the LMA. Fifty patients were included in the study. After successful placement of the LMA was confirmed, cuff pressure measurements were made with the head neutral and extended both with and without the cervical collar.

The authors found that placing the cervical collar does not reduce the LMA cuff pressure during extension of the head and, in fact, found that the cervical collar improved the LMA seal. The authors concluded that the application of the cervical collar prevents the LMA from losing seal pressure if the head is extended and recommend the use of the cervical collar after placement of the LMA in all pre-hospital patients.

Click here to review an abstract of the original work.

Research: Optical Fibers for Nerve Block placement

The application of technology to practice has enabled the CRNA to deliver patient care that is safer and more reliable than at any other time in history. The placement of nerve blocks has always been challenging. Thirty years ago, soliciting paresthesia or trans arterial needle placement were common methods for administering an axillary block. The Ultra sound guided nerve block has increased not only the success rate but also safety to the patient. What can be done to improve on Ultra Sound?

Desjardins AE et al recognized that the success of a nerve block depends upon the proper placement of the needle. They developed a stylet with optical fibers that could collect light for analysis of optical reflectance spectrometry. The theory was that different tissues reflect a different wavelength of light and the stylet could be used to differentiate between nerve and vascular tissues. Click here to read an abstract of their work.

Taking the concept one step further, Balthasar A, et al used the technique on human subjects. They reported that the stylet with optical fibers was able to differentiate between nerve and vascular tissue an on 2 cases detected actual vascular penetration by the needle. Click here to read an abstract of their study.

Will the optical stylet replace ultra sound for nerve block placement? Probably not. However, the addition of the optical stylet which detects penetration of the needle into either vascular or nerve structures could add another element of safety to nerve block placement.

Clinical Topic: Glucose Control in the OR

The intra-operative management of the Diabetic patient poses many challenges to the anesthetist. Theories abound related to the advantages of “tight control” using an insulin infusion versus a less strict approach using bolus dosing. Regardless of your beliefs regarding blood sugar control, being informed and having a plan is essential for the safety of your patient.

An excellent review article by Joseph F. Answine, M.D. titled Peri-operative Diabetes Management for Dummies: Just Check the Sugar! and published by the Pennsylvania Society of Anesthesiologists discusses the foundational points to be considered when administering anesthesia to the diabetic patient.

From Dr Answine: “What do we know about peri-operative glucose control? We know that infection rate, length of hospital stay, overall cost for the hospitalization, and morbidity and mortality are directly proportional to peri-operative blood glucose levels. We also know that there are numerous studies demonstrating improved overall outcomes with improved glucose control.”

The article goes on to advise the anesthetist to know the patient’s normal and work to keep the intraoperative blood sugar as close to the patient’s normal as possible. The use of the glucometer intraoperatively is essential as is documentation. When the patient comes with an insulin pump it is best to leave it on and check glucose levels frequently.

Other basics of managing the diabetic patient:

Do diabetics first case of the day
If outpatient, discuss post op glucosecontrol both pre op and again before discharge
Test glucose pre-op
Know when patient last took diabetic medications
Know your patient’s history for self-control of diabetes
Intraop….infusions are better than a bolus
If the patient tells you how to manage their diabetes…..listen carefully

The bottom line is to know your patient’s history and glucose level. With that knowledge, treat the patient appropriately.

The Full article continues with a chart showing the types of insulin, peak, and duration of action. Click here to read the full article and return to www.procrna.com with your comments.

Research: Anesthesia causes jet-lag

A press release from the University of Aickland dated April 17th, 2012 described a recent study done there that linked anesthesia to a feeling of jet-lag following surgery.

The researcher, Dr. Guy Warman, noted, “Our work shows that general anesthesia effectivly shifts you to a different time zone, producing chemically-induced jet-lag. It provides scientific explanation for why people wake up from surgery feel as though very little time has passed.”

Dr. Warman goes on to state, “It’s been known for sometime that after anesthesia, people’s biological clocks are disrupted and this can compromise their sleep pattern and mood as well as wound healing and immune function.”

This interesting work was done on honey bees which are known to have a keen sense of time.

Click here to read the original press release

Anesthesia Awareness and the Bispectral Index

To BIS or not to BIS. That is a common topic for discussion in the anesthesia community. Unanticipated intraoperative awareness is a traumatic event for the patient with many developing post traumatic stress disorder. Anesthetists are challenged with providing safe anesthesia which includes the absence of recall by the patient.

The Bispectral Index was developed from technology related to the processed electroencephalogram. Claims are made that when the BIS value remains below 60 the risk of awareness under anesthesia is greatly reduced.

A study by Avidan et al published in the New Engl J Med studied the effectiveness of the BIS monitor compared to strict monitoring of the end tidal anesthetic gas concentration. Target values of 40-60 were used for the BIS group and 0.7-1.3 MAC for the end tidal anesthetic group. Alarms were set to warn the anesthetist when patient values were outside the prescribed limits.

The authors concluded that use of the BIS monitor did not reduce awareness as compared to strict monitoring of the end tidal anesthetic gas concentration. The study suggests that using the end tidal gas concentration protocol in patients at high risk for awareness could be of benefit. Setting alarms for monitoring end tidal gas concentration is essential.

Click here to read the full article. Please use the “comments” prompt at the top of this page to share your thoughts and experiences.