Two different mammalian genes for the catalytic subunit (C) of cAMP-dependent protein kinase have previously been characterized (C alpha, C beta). In the present study, we report the molecular cloning of a third isoform of C, from a human testis cDNA library, as well as the isolation of human cDNAs for C alpha and C beta. This third form of C, which we will designate C gamma, is clearly derived from a distinct gene and shows a tissue-specific expression. A close evolutionary relation between C gamma and C alpha was suggested by nucleotide homologies (86% inside the open reading frame, 81% in the 3'-untranslated region). Thus, the C gamma cDNA cross-hybridized with the 2.8 kilobase (kb) C alpha mRNA, present at high levels in most human tissues, as well as with a 1.8 kb C gamma-specific mRNA, which was only found at detectable levels in human testis. However, at the amino acid level, C alpha and C beta showed a close relationship (93% homology), whereas C gamma diverged significantly from both C alpha (83%) and C beta (79%). Taken together with the tissue-specific expression of C gamma, this suggests a pressure on C gamma during evolution, acting to modulate it in a functionally specific way. Certain amino acid substitutions make C gamma a distinct member of the cAMP-dependent subfamily of protein kinases, and suggest that C gamma may be distinct in its protein substrate specificity or its interaction with the different regulatory subunits.

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BackgroundAn emergency cricothyrotomy is the last-resort in most airway management protocols and is performed when it is not possible to intubate or ventilate a patient. This situation can rapidly prove fatal, making it important to identify the best method to establish a secure airway. We conducted a systematic review to identify whether there exists superiority between available commercial kits versus traditional surgical and needle techniques.MethodsMedline, EMBASE and other databases were searched for pertinent studies. The inclusion criteria included manikin, animal and human studies and there were no restrictions regarding the professional background of the person performing the procedure.ResultsIn total, 1,405 unique references were identified; 108 full text articles were retrieved; and 24 studies were included in the review. Studies comparing kits with one another or with various surgical and needle techniques were identified. The outcome measures included in this systematic review were success rate and time consumption. The investigators performing the studies had chosen unique combinations of starting and stopping points for time measurements, making comparisons between studies difficult and leading to many conflicting results. No single method was shown to be better than the others, but the size of the studies makes it impossible to draw firm conclusions.ConclusionsThe large majority of the studies were too small to demonstrate statistically significant differences, and the limited available evidence was of low or very low quality. That none of the techniques in these studies demonstrated better results than the others does not necessarily indicate that each is equally good, and these conclusions will likely change as new evidence becomes available.

This article is intended as a generic guide to evidencebased airway management for all categories of pre-hospital personnel. It is based on a review of relevant literature but the majority of the studies have not been performed under realistic, pre-hospital conditions and the recommendations are therefore based on a low level of evidence (D). The advice given depends on the qualifications of the personnel available in a given emergency medical service (EMS). Anaesthetic training and routine in anaesthesia and neuromuscular blockade is necessary for the use of most techniques in the treatment of patients with airway reflexes. For anaesthesiologists, the Task Force commissioned by the Scandinavian Society of Anaesthesia and Intensive Care Medicine recommends endotracheal intubation (ETI) following rapid sequence induction when securing the pre-hospital airway, although repeated unsuccessful intubation attempts should be avoided independent of formal qualifications. Other physicians, as well as paramedics and other EMS personnel, are recommended the lateral trauma recovery position as a basic intervention combined with assisted mask-ventilation in trauma patients. When performing advanced cardiopulmonary resuscitation, we recommend that non-anaesthesiologists primarily use a supraglottic airway device. A supraglottic device such as the laryngeal tube or the intubation laryngeal mask should also be available as a backup device for anaesthesiologists in failed ETI. Accepted for publication 25 February 2008Key words: Pre-hospital; airway management; endotracheal intubation; laryngeal mask airway; laryngeal tube airway; combitube; emergency medical systems. Purpose T HIS article is intended as a guide to evidencebased pre-hospital airway management. The available litterature on pre-hospital airway management reflects vast differences in pre-hospital emergency medicine service (EMS) organisation, qualification levels, training programmes and even terminology. These differences make comparisons between systems and treatment protocols difficult at best. The conduct of clinical trials in pre-hospital airway management is hampered by the 2001/20/ EC directive of the European Parliament concerning informed consent. This paper describes selected equipment and techniques available for pre-hospital airway management. Advice given differs, depending on which category of personnel is available in a given EMS. Our baseline assumption is that a certain level of education and training is necessary for the safe use of a specific technique. Distinction must be made between personnel trained and experienced in providing and monitoring anaesthesia and other groups of personnel with limited or no anaesthetic skills. This distinction dictates which drugs and equipment that should be available in the prehospital setting. Differences between regions and systemsParamedic-based systems are the rule in the United States, whereas physician-based pre-hospital systems are common in Europe. Ideally, the best person to manage the pre-hospital airwa...