An early invasive strategy is recommended for high risk non-ST elevation acute coronary syndrome (ST/T wave changes, ongoing symptoms, or troponin rise) but how early is early? The French ABOARD study randomised 352 patients to an early (median time of randomisation to sheath insertion 70 mins) or delayed (21 hours) strategy. No difference in the primary outome measure of troponin elevation was observed. Good news for busy cardiologists who won’t have to get up at night for this type of patient.
JAMA. 2009 Sep 2;302(9):947-54
PPIs such as omeprazole affect the pharmacodynamics of thienopyridines such as clopidogrel, but this does not seem to affect clinical outcomes for most patients. Pantoprazole and esomeprazole have less of an effect on the platelet response to clopidogrel.
Pharmacodynamic eﬀect and clinical eﬃcacy of clopidogrel and prasugrel with or without a proton-pump inhibitor: an analysis of two randomised trials
Lancet editorial (Lancet subscription required)
Newer sensitive troponin assays (detecting 0.04 ng/ml troponin I) showed better senstivity at detecting acute myocardial infarction at 0 amp; 3 hours compared with standard assays. Specificity was however slightly lower than standard assays, suggesting non-AMI pathologies that produce a degree of cardiomyocyte injury will also be detected. Senstivity and specificity for AMI at baseline were both around 90%. Troponin I 0.04 ng/ml was an independent risk factor for adverse events at 30 days.br /br /a href=”http://content.nejm.org/cgi/content/short/361/9/868″http://content.nejm.org/cgi/content/short/361/9/868/a
During simulated cardiac arrest resuscitations, a comparision was made between those run by teams that had had time to form before the arrest, and those that had to be assembled ad hoc after the arrest occurred. 99 teams of three doctors, including GPs and hospital physicians were studied. ACLS algorithms were less closely followed in the ad hoc formed teams, with more delays to therapies such as defibrillation. Analysis of voice recordings revealed the ad hoc teams to make fewer leadership utterances (eg. ‘we should defibrillate’ or ‘the next countershock will be 360J’) and more reflective utterances (eg. ‘what should we do next?’). The authors suggest that team building is therefore to be regarded as an additional task imposed on teams formed ad hoc during CPR that may substantially impact on outcome. No surprise to those of us who banned ‘cardiac arrest teams’ from our emergency department resuscitation rooms many years ago!
Hands-on time during cardiopulmonary resuscitation is affected by the process of teambuilding: a prospective randomised simulator-based trial
BMC Emerg Med. 2009 Feb 14;9:3
Full text at http://www.biomedcentral.com/1471-227X/9/3
Use of non-invasive ventilation to wean critically ill adults off invasive ventilation: meta-analysis and systematic review
The growing evidence base in support of liberating patients from invasive mechanical ventilation by means of non-invasive weaning is summarised in this systematic review of 12 randomised trials. Non-invasive weaning was associated with decreased mortality, ventilator associated pneumonia, length of stay in intensive care and hospital, total duration of mechanical ventilation, and duration of invasive ventilation. It should be noted that most of the trials exclusively enrolled patients with exacerbation of chronic obstructive pulmonary disease; benefits in other types of ventilated patients remain to be firmly proven.
BMJ. 2009 May 21;338:b157
An observational, prospective study comparing tibial and humeral intraosseous access using the EZ-IO
Emergency physicians at Singapore General Hospital found flow rates to be similar when comparing the tibia with the humerus as sites for adult IO access. The EZ-IO had a very high insertion success rate. It took about 12 minutes to infuse a litre of saline, which drops to about 6 minutes if a pressure bag is used.
Am J Emerg Med. 2009 Jan;27(1):8-15
Published flow rates for cannulae are derived from a test in which fluid runs through a perfectly straight cannula into an open receptacle. Laminar flow is expected in such a model in which the Hagen-Poisseuille formula tells us that flow is proportional to the fourth power of the radius. In this study manufacturers’ published flow rates were compared with an artifical vein model. Hartmann’s flowed faster than Gelofusine. For all cannulas flow was less than the manufacturers’ published rates. Although the radius was the biggest determinant of flow rate, the fourth power could not be used, suggesting a mixture of laminar and turbulent flow. The addition of pressurised infusions increased the flow rate with increasing pressure. Although the vein model used has limitations, and many other factors may influence flow rate in the clinical setting, the authors’ conclusions are helpful:
While the effect of radius is less than commonly believed, it is still important. However, clinicians should be aware of the limitations of increasing radius and use other strategies to increase flow when needed. These could include use of pressure, choice of fluid to be infused, and using multiple cannulae in parallel.
Fluid flow through intravenous cannulae in a clinical model
Anesth Analg. 2009 Apr;108(4):1198-202
No rescuer or bystander has ever been seriously harmed by receiving an inadvertent shock while in direct or indirect contact with a patient during deﬁbrillation. New evidence suggests that it might even be electrically safe for the rescuer to continue chest compressions during deﬁbrillation if self-adhesive deﬁbrillation electrodes are used and examination gloves are worn. This paper reviews the existing evidence, but warns more deﬁnite data are needed to make absolutely sure that there is no risk before deﬁbrillation safety recommendations are changed.
Is external defibrillation an electric threat for bystanders?
Resuscitation. 2009 Apr;80(4):395-401
Hyperoxia may reduce coronary artery blood flow, increase systemic vascular resistance, and decrease cardiac output. This paper argues that if the baseline arterial oxygen saturations are >90%, high concentration oxygen does not increase oxygen transport, as the reductions in cardiac output are in excess of the increase in oxygen content. The balance of the limited evidence that exists suggests that the routine use of oxygen in uncomplicated MI (no failure or shock) may increase infarct size and possibly increase the risk of mortality, owing to its haemodynamic effects, including a reduction in coronary blood flow.
Routine use of oxygen in the treatment of myocardial infarction: systematic review
Heart. 2009 Mar;95(3):198-202