An interesting MRI-based study of adult volunteers takes a further look at whether cricoid pressure effectively occludes the digestive tract. The authors assert that the part of the digestive tract at the level of the cricoid is the distal hypopharynx, that it is fixed in relation to the airway (making the previously demonstrated lateral oesophageal displacement irrelevant), and that the lumen may be obliterated during Sellick’s manouevre.
Accompanying pro and con editorials reaffirm the need for further clinical evidence on the effectiveness of the technique.
Cricoid pressure results in compression of the postcricoid hypopharynx: the esophageal position is irrelevant
Of 203 patients attending a US Level 1 trauma centre who had pre-hospital airway management, 25 (12%) had unrecognised oesophageal intubations.
Patients were treated in the field by fire rescue personnel of various municipalities and with different experience levels. Patients transported by air were significantly more likely to be successfully intubated than those transported by ground, perhaps due to both increased experience and the use by air crews of succinylcholine. The authors in their discussion contrast these results with those of European studies which report higher success rates with pre-hospital systems that employ emergency physicians and anaesthetists.
After intubation it is critical to securely fasten the tracheal tube so it does not dislodge during transfer. Dedicated devices are available for this although mostly cloth tape is used.
Different knots have been compared although not found be significantly different in terms of security1. One favoured knot, which is easy to learn and to teach, is the lark’s head (also called cow’s hitch)2.
The tape is folded in half so there is a loop at one end and two free ends at the other. The loop is wrapped around the tube and the two free ends are fed through the loop, and then taped around the patient’s head. It has been suggested that this results in the tape gripping the tube over the widest possible area, thereby reducing the potential for slippage and displacement.
Finally a well designed blinded randomised controlled trial on this subject. 0.3 mg/kg etomidate was compared with 2mg/kg ketamine for RSI in 655 patients requiring emergency intubation in the pre-hospital, emergency department, or intensive care unit environments. No difference was observed in intubation conditions or the primary endpoint of maximum SOFA score in the first three days, although the etomidate group had a higher rate of adrenal insufficiency as defined by response to an ACTH test.
Prehospital airway management on rescue helicopters in the United Kingdom
26 of 27 identified UK rescue helicopter bases responded to a questionnaire sent by German anaesthesiologists on the airway equipment they carried. The take home message is that there were some important gaps: not all carried equipment for establishing a surgical airway and not all had a means of capnometry. Pull your socks up guys the Germans are watching.
In contrast to literature showing high intubation failure rates by ground paramedics, a review over eight years of 369 intubations by flight paramedics and nurses showed successful tracheal intubation in 92.1% cases. Of the 369 intubation encounters, rapid sequence medications were given in 345. The authors ascribe their success to both initial training and mandatory ongoing practice and demonstration of competencies.
Paramedics intubated simulated patients positioned supine on the floor by direct laryngoscopy (DL) and by using the Airtraq device. Ventilation was achieved more quickly with the Airtraq in a difficult airway scenario (tongue oedema), and after a short training period the Airtraq was faster at intubating a ‘normal’ airway.
The risk of apnoea in neonates requiring prostaglandin E1 infusions for duct-dependent congenital heart disease is well described and often results in the recommendation to intubate prior to transfer. An American study of 202 transported infants on PGE1 shows a higher rate of transport-related complications in those that had been intubated. None of the 73 (36%) unintubated patients required intubation for apneoa during transport. These data are in keeping with a previous Australian study of 300 infants receiving PGE1 in which only 2 of 78 unintubated patients experienced apnoea. To intubate or not to intubate? Transporting infants on prostaglandin E1 Pediatrics. 2009 Jan;123(1):e25-30
Careflight Queensland report a 9 month series of intubations by their doctor-paramedic HEMS teams who performed 39 intubations (and assisted hospital doctors in an additonal 4), of which less than half were pre-hospital. There was one failed intubation, successfully ventilated with a laryngeal mask airway. Emergency intubation: a prospective multicentre descriptive audit in an Australian helicopter emergency medical service. Emerg Med J. 2009 Jan;26(1):65-9
A review of 1954 out-of-hospital tracheal intubation (ETI) attempts by EMS crews revealed 444 (22.7%) patients experienced one or more ETI errors, including tube misplacement or dislodgement in 61 (3%), multiple ETI attempts in 62 (3%) and failed ETI in 359 (15%). Pneumonitis was associated with failed ETI (n=20, 19%; univariable OR 2.54; 95% CI 1.24-5.25). The authors conclude that out-of-hospital ETI errors are not associated with mortality, but failed out-of-hospital ETI increases the odds of pneumonitis. http://www.ncbi.nlm.nih.gov/pubmed/18952357