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
OBJECTIVE: During mechanical ventilation, inspiration cyclically decreases the left cardiac preload. Thus, an end-expiratory occlusion may prevent the cyclic impediment in left cardiac preload and may act like a fluid challenge. We tested whether this could serve as a functional test for fluid responsiveness in patients with circulatory failure.
DESIGN: Prospective study.
SETTING: Medical intensive care unit.
PATIENTS: Thirty-four mechanically ventilated patients with shock in whom volume expansion was planned.
INTERVENTION: A 15-second end-expiratory occlusion followed by a 500 mL saline infusion.
MEASUREMENTS: Arterial pressure and pulse contour-derived cardiac index (PiCCOplus) at baseline, during passive leg raising (PLR), during the 5-last seconds of the end-expiratory occlusion, and after volume expansion.
MAIN RESULTS: Volume expansion increased cardiac index by >15% (2.4 +/- 1.0 to 3.3 +/- 1.2 L/min/m, p < 0.05) in 23 patients ("responders"). Before volume expansion, the end-expiratory occlusion significantly increased arterial pulse pressure by 15% +/- 15% and cardiac index by 12% +/- 11% in responders whereas arterial pulse pressure and cardiac index did not change significantly in nonresponders. Fluid responsiveness was predicted by an increase in pulse pressure >or=5% during the end-expiratory occlusion with a sensitivity and a specificity of 87% and 100%, respectively, and by an increase in cardiac index >or=5% during the end-expiratory occlusion with a sensitivity and a specificity of 91% and 100%, respectively. The response of pulse pressure and cardiac index to the end-expiratory occlusion predicted fluid responsiveness with an accuracy that was similar to the response of cardiac index to PLR and that was significantly better than the response of pulse pressure to PLR (receiver operating characteristic curves area 0.957 [95% confidence interval [CI:] 0.825-0.994], 0.972 [95% CI: 0.849-0.995], 0.937 [95% CI: 0.797-0.990], and 0.675 [95% CI: 0.497-0.829], respectively).
CONCLUSIONS:The hemodynamic response to an end-expiratory occlusion can predict volume responsiveness in mechanically ventilated patients.
Predicting volume responsiveness by using the end-expiratory occlusion in mechanically ventilated intensive care unit patients.
Crit Care Med. 2009 Mar;37(3):951-6
An industry-sponsored double-blind randomised controlled trial comparing midazolam with the central alpha-2 agonist dexmedetomidine showed the newer drug to provide similar levels of sedation with less delirium and a shorter time to extubation. It was associated with more episodes of bradycardia not requiring intervention.
This new sedative drug, related to clonidine, provides some analgesia and anxiolysis, and is noted for its lack of respiratory depression. An accompanying editorial points out the known association between benzodiazepines and delirium, and asks whether a comparison with propofol would have shown the same improved outcomes.
Dexmedetomidine vs midazolam for sedation of critically ill patients: a randomized trial
JAMA. 2009 Feb 4;301(5):542-4
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
Two English HEMS services covering the same geographical area, one physican / paramedic crewed and one double paramedic crewed, were compared. There were no differences in scene times. As well as predictably providing more rapid sequence induction, nerve blocks, and ketamine use, the physician-paramedic team discharged more people at scene and were more likely to cease resuscitation attempts in GCS 3 patients.
Influence of air ambulance doctors on on-scene times, clinical interventions, decision-making and independent paramedic practice.
Emerg Med J. 2009 Feb;26(2):128-34
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
171 rural Australian HEMS missions were retrospectively analysed. Some of the data contrast starkly with the more limelight-occupying urban services: average time from dispatch to scene was 48 minutes, average scene time was 50 mins, and average total distance flown was 160 nautical miles (297 km!) – the longest reported in the literature. There was no difference in injury severity between physician-staffed and paramedic-staffed missions, and no difference in mortality. When transport times for distances less than 50km from the hospital were compared, road responses were significantly faster than helicopter dispatch, whereas helicopter use created significant time savings at distances over 100km. The authors suggest that in the absence of special circumstances, a helicopter response within 100 km from base does not improve time to definitive care. They also recommend caution in mandating physician staffing of HEMS, particularly in environments with a limited pool of critical care doctors.
Helicopter use in rural trauma
Emerg Med Australas. 2008 Dec;20(6):494-9
London HEMS doctors describe their use of ketamine for pre-hospital analgesia and sedation in 1030 retrospectively reviewed cases, concluding its prehospital use is safe.
Pre-hospital use of ketamine for analgesia and procedural sedation
Emerg Med J. 2009 Jan;26(1):62-4
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.
A nurse-based pre-hospital care system in Holland describes its experience with pre-hospital CPAP for acute cardiogenic pulmonary oedema. It appears that the simple Boussignac apparatus is straightforward to apply in the ambulance environment. Arguments about lack of outcome studies aside, if it’s necessary to undertake an interhospital transfer of a patient established on CPAP then this might be a relatively straightforward means of doing so.