Measurement of carbon dioxide levels during use of ELSA and the effect of venting on these levels.

DESIGN: A prospective, objective assessment of ELSA use, in order to determine whether venting of the ELSA influences carbon dioxide (CO2) levels. PRIMARY ENDPOINT: Inspired and expired CO2 levels. SETTING: On board RFA ARGUS during Operation TELIC. METHODS: 10 volunteers had a baseline of inspired and expired CO2 levels taken. These levels were measured at one minute intervals during use of an ELSA in 3 conditions--sitting, jogging and jogging with venting. RESULTS: There was no difference in expired CO2 levels between baseline and use of ELSA whilst sitting. Periodic venting of the ELSA made no difference to inspired and expired CO2 levels. CONCLUSIONS: Venting of the ELSA during use makes no difference to CO2 levels whether inspired or expired. Therefore, venting is unnecessary and potentially wastes vital time during escape from a smoke-filled compartment and adds additional stress to the escapee.

Non-invasive cardiac output monitoring.

Outcomes in the management of critically ill patients may be improved using goal-directed peri-operative haemodynamic monitoring. A conservative approach may no longer be acceptable but in view of the significant morbidity associated with balloon tipped flow directed pulmonary artery catheters a non-invasive approach would be preferable. In this review we consider the different non-invasive techniques available and discuss the advantages and disadvantages of each technique.

Off-pump coronary artery surgery.

Cardiopulmonary bypass has several associated deleterious effects that include a systemic inflammatory response, coagulopathy, central nervous system complications and a variable degree of end-organ damage. The recent upsurge in interest in "beating-heart" surgery attempts to avoid these deleterious effects. Advances in surgical technique, such as the use of intracoronary shunts and the Octopus retractor, have made beating-heart surgery a reality. The challenges for the anaesthetist are greater than for coronary artery surgery using cardiopulmonary bypass, and whilst some advantages are proven, such as the lack of the inflammatory response and the decreased need for blood or blood products, others have yet to be proved and there is a need for further research. The advantages and disadvantages need to be evaluated in randomised studies in order to confirm the safety and efficacy of these new techniques in terms of long-term graft patency and decreased morbidity.

A comparison of intercuff and single cuff techniques of intravenous regional anaesthesia using 0.5% prilocaine mixed with technetium 99m-labelled BRIDA.

Intravenous regional anaesthesia of the upper limb is a widely used technique first described by Bier in 1908. The exact site of action of injected local anaesthetic has not been determined. We have performed intravenous regional anaesthesia on volunteers using prilocaine mixed with technetium 99m-labelled 2,4,6 trimethyl-3-bromo iminodiacetic acid. Two different techniques of intravenous regional anaesthesia (the 'normal' cuff and the intercuff techniques) were combined with gamma camera tracking of the radiolabel to determine the site of local anaesthetic action. The onset of action was similar for both techniques. The local anaesthetic was mainly retained in the antecubital fossa in both techniques but in the 'normal' technique, the local anaesthetic subsequently showed some retrograde spread. This would suggest that the main site of action of local anaesthetic used for intravenous regional anaesthesia is the larger nerves in the vicinity of the antecubital fossa.

Sonoclot analysis.

Assessment of perioperative bleeding disorders, especially those related to platelet dysfunction, remains a clinical challenge. The management of the bleeding patient in the operating theatre or on the postoperative ward is often empirical with little scientific basis. Much of the reason for this is that conventional clotting studies are not immediately available and there is a perceived urgency, particularly among trainee doctors, to treat bleeding disorders without first establishing the exact nature of the coagulopathy. SCT provides useful information on platelet function, particularly in patients after cardiopulmonary bypass, and has enabled practitioners to rationalize the management of bleeding disorders and not expose their patients to the risks of unnecessary transfusion of blood products. Undoubtedly further studies are required before this instrument can be used reliably in the clinical setting but it may prove to be a useful addition to the available techniques for monitoring perioperative bleeding disorders.

Effect of temperature and cardiopulmonary bypass on the auditory evoked response.

We have recorded auditory evoked potentials before and during cardiopulmonary bypass in 10 adult patients undergoing cardiac surgery under moderate hypothermia to 27-28 degrees C. The immediate effect of bypass was a small decrease in latency and increase in amplitude of the early cortical response. We also studied two adults and two children during profound hypothermia with circulatory arrest during cardiopulmonary bypass. Reduction in core temperature to 25 degrees C resulted in an increase in latency and amplitude of the brain stem responses; below this temperature the amplitude decreased but latency continued to increase until the auditory evoked response trace became completely flat between 21 and 19 degrees C. These changes were reversible on rewarming.

Auditory evoked responses and near infrared spectroscopy during cardiac arrest.

We describe a patient who had a cardiac arrest during anaesthesia, in whom regional cerebral oxygen saturation was being measured by near infrared spectroscopy and the auditory evoked responses (AER) were being recorded. Both of these monitors provided useful information on cerebral oxygenation during cardiac arrest. Changes in the AER as the result of either reduced circulation or hypothermia are similar, and should these two situations occur simultaneously there could be difficulty in the interpretation of the AER.

Lansoprazole in the prophylaxis of acid aspiration during elective surgery.

We have assessed the efficacy of a single dose of lansoprazole in increasing the pH and decreasing the volume of gastric residue at induction of anaesthesia in adult patients undergoing elective orthopaedic surgery. We studied 66 ASAI-II patients, allocated to one of three groups to receive either placebo (group 1), lansoprazole 30 mg (group 2) or lansoprazole 60 mg (group 3), 8-12 h before induction of anaesthesia. Volume and pH of gastric contents were measured after induction of anaesthesia by aspiration via a 16-French gauge gastric tube. Patients who received lansoprazole had a significantly higher pH than the placebo group (P < 0.01) but there was no difference between the two lansoprazole groups. The volume of gastric residue was significantly smaller (P < 0.01) in both lansoprazole groups compared with the placebo group: 28% of those in group 3 had a pH of gastric residue < 2.5 and volume > 25 ml compared with 30% in group 2 and 63% in group 1, respectively.

The laryngeal mask airway in resuscitation.

Previous work has shown that insertion of the laryngeal mask airway is a skill that is easily taught to inexperienced operators. In this study we have assessed the ability of non-anaesthetists to maintain an airway in a paralysed, anaesthetised patient in the controlled setting of an anaesthetic room. The methods used to maintain the airway included a tightly fitting facemask, using a one-handed and two-handed technique, and a laryngeal mask airway. The inspired volume delivered to the patients was standardised using a Penlon Nuffield ventilator attached to the breathing system. Our results showed no difference in success in maintaining the airway between the three techniques or in the mean expired volumes achieved during successful ventilation.

Routine pre-oxygenation using a Hudson mask. A comparison with a conventional pre-oxygenation technique.

Two techniques of pre-oxygenation were studied by continuous analysis of respired gases using a mass spectrometer in 10 healthy volunteers. The first was a conventional technique as commonly used in anaesthesia with a Bain system and tightly-fitting anaesthetic face-mask and an oxygen flow of 8 l.min-1. The second technique also used a Bain system with an oxygen flow of 8 l.min-1, but with a Hudson mask attached. The mean fractional end-tidal oxygen concentrations after 3 min were 0.812 and 0.46 respectively for each of the pre-oxygenation techniques against 0.16 for subjects breathing air. This represents a considerable increase in pulmonary oxygen reserve for both techniques. The second technique is not an alternative to conventional pre-oxygenation for emergency anaesthesia, but is a useful and simple method that is acceptable to both patient and anaesthetist in routine cases.

A survey of priming solutions used for cardiopulmonary bypass.

We conducted a postal survey of all National Health Service centres where cardiac surgery is performed. We requested information about the priming solutions and additives used in the cardiopulmonary bypass circuit, and specifically asked whether changes were made in priming solutions for diabetic patients. Hartmann's solution was used by 63% of respondents, either alone or mixed with colloid. Heparin was added to the prime by 89% of respondents. Only two centres and one anaesthetist at a third centre altered the prime for diabetic patients.

Operating at sea in an aircraft carrier.

The policy of the Medical Officers serving in HMS Ark Royal between January 1988 and June 1989 with regard to surgery and anaesthesia at sea is described. The skills and equipment available, techniques used, operations performed and complications that resulted are outlined. The advantages and disadvantages of an active operating policy are discussed and the postulate ventured that in order to achieve maximum efficiency within the medical department of an aircraft carrier such a policy is justified. Finally, in the light of present day litigious trends, the question of the propriety of the policy is posed.

NBCI--another threat to operational effectiveness?

Battle casualties are well recognised as a threat to Operational Effectiveness (OE) at times of conflict. Less well appreciated is that naturally occurring illnesses and injuries--Non-Battle Casualties and Injuries (NBCI)--continue to present at such times and will add to the problems of fighting the ship. This prospective study showed that NBCI resulted in a total of 1369 man days of lost personnel effectiveness among some 1738 RN servicemen during a 180 day deployment. That is just 0.42% of the possible man working days. This represents a loss of 4.3 man days per 1000 at risk per day in terms of fitness for Full Duties or 2.74/1000/day excluding those able to perform Light Duties. It is unlikely that such rates would affect the OE of the fighting units but they do represent a significant challenge to the Royal Naval Medical Service to continue to maintain the rates at such low levels, so that when aggregated to the numbers of battle casualties, OE is maintained as far as possible.

The Royal Naval Medical Stores for Service Afloat: a prospective quantitative study.

The contents of the scale of Medical Stores for Service Afloat must provide adequate quantities of drugs to allow proper patient care in a variety of situations often remote from specialist support. The overall make up of the scale is difficult to envisage outside the context for which it was conceived. This study was designed to assess the accuracy of the make up of the scale in three RN ships over a six-month period during a detached deployment. During this time the usage of all consumable items was specifically recorded and the outcome subjected to rigorous analysis in relation to the present scale. The results of the study indicate that in the case of both HMS Ark Royal (AR) and the two smaller ships HMS Edinburgh and HMS Sirius (ES) the quantities of drugs in the majority of cases are in excess of requirements. Of the 290 (AR) and 266 (ES) individual drugs 68% and 40% respectively could safely be reduced by varying amounts, whereas only 7.6% and 4.9% respectively needed to be increased. Furthermore, when these changes are costed the savings that result are 7806 pounds for the AR scale and 1532 pounds for the ES scale. Extrapolation of these figures across the surface fleet produces an overall saving on the costs of drugs of over 87,000 pounds.

von Recklinghausen's disease of nerves: a modern day social response.

We describe a patient with von Recklinghausen's Disease of Nerves whose appearance provoked an emotive reaction in the close community of an RN ship akin to that reported in the case of Sir Frederick Treves' "Elephant Man". The RN divisional system provided a valuable contribution to the resolution of the problems created.