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OTTAWA, Ontario -- Paramedics trained in the use of endotracheal intubation and intravenous drugs for respiratory distress patients on the way to the hospital saved lives but fewer than predicted.
OTTAWA, Ontario, May 24 -- Paramedics trained in the use of endotracheal intubation and intravenous drugs for respiratory distress patients on the way to the hospital saved lives but fewer than predicted.
The pre-hospital advanced-life-support intervention, which was superimposed on the existing emergency medical system, was associated with a 1.9% absolute decrease in death rates among respiratory distress patients, according to a report in the May 24 issue of the New England Journal of Medicine.
But the investigational approach, a before-and-after controlled trial carried out with 8,138 patients in 15 Canadian cities, did not meet a prespecified, minimal, clinically important difference of 2%, found Ian G. Stiell, M.D, of the University of Ottawa here, and colleagues in the Ontario Prehospital Advanced Life Support (OPALS) Study Group.
Confounding factors made the results of the trial less than clear-cut. Among these factors was that although paramedics were trained in standard advanced life support, in practice they still often relied on older life-support techniques.
The study consisted of two six-month phases. The first phase provided an historical rather than a contemporary control group.
In the first six months, 3,920 patients received only basic-life-support. Patients with full cardiac arrest, a primary symptom of chest pain, or other nonrespiratory symptoms were excluded.
Basic life support included use of oxygen, bag-valve-mask ventilation, and in some cases nebulized bronchodilators, and sublingual nitroglycerin.
In the second six-month phase, 56.6% of 4,630 patients received advanced life support system, which included endotracheal intubation and the administration of intravenous drugs. However, successful endotracheal intubation occurred in only 1.4% of the patients, and intravenous drugs, mainly furosemide (Lasix) and morphine, were given to a 15.1% (furosemide 14.4%).
This part of the study was also marked by a substantial increase in the use of nebulized salbutamol [albuterol] (53% versus 14.9%) and sublingual nitroglycerin (9.4% vs. 0.7%) for the relief of symptoms. Both of these treatments were also part of standard basic care, the researcher noted.
From the basic-treatment-phase to the advanced-life-support phase, the death rates decreased significantly from 14.3% to 12.4% (absolute difference, 1.9%, 95% confidence interval, 0.4 to 3.4; P=0.01). The adjusted odds ratio was 1.3 (CI, 1.1 to 1.5).
Although there was a significant reduction in overall mortality, the small magnitude of the observed decrease did not exceed the prespecified, minimal, clinically important difference of 2%, the researchers said.
These improvements in outcome were achieved despite the fact that advanced treatment paramedics attended fewer than 60% of the patients in the second phase of the study. Furthermore, few patients had endotracheal intubation, while IV medication was used for only 15% of the patients, the researchers said.
Other factors may have muddied the results. A program to give medication for symptom relief (nebulized salbutamol) and sublingual nitroglycerin was introduced toward the end of the first phase of the study, and although not specifically related to advanced life support, these drugs may have played a role.
Also, the introduction of positive airway pressure in some ERs during the study period may have influenced outcomes, the researchers said.
"The implications of this study require careful consideration," the investigators wrote. The patients in the second phase had a significantly lower mortality than those in the first phase. According to an estimate, 53 is the number needed to treat for the entire cohort with shortness of breath. In the study regions with 2.5 million people, approximately 161 lives would be saved each year, they said.
However, it is less clear, they added, which interventions should be considered essential and how they should be implemented.
In this study, few patients underwent intubation, and of the IV medications, only furosemide was given to a large number of patients (14.4%).
Furthermore, the most substantial change was the marked increase in the use of medications for symptom relief, an intervention not part of advanced life support. Thus the benefit of the intervention in this trial may have been due primarily to the use of nebulized salbutamol and sublingual nitroglycerin, rather than advanced life support.
In addition, decision to dispatch an advanced support team cannot be made on the basis of a subsequently determined discharge diagnosis. There was more evidence of a survival benefit among patients with an EMS code of "not urgent" than among those with an "urgent" code, so it is unclear whether patients were more likely to benefit if they were less ill, they said.
It is also not clear, they said, whether other interventions occurring after the patients arrived at the hospital played a role in the improvement in outcome.
Finally, they added, the benefit of the advanced-support program must be balanced against its relatively high cost.
An important potential limitation of the study, the researchers said, is that it was designed as a before-and-after controlled trial rather than as a single randomized trial. Randomized withholding of potentially lifesaving procedures would have been unethical.
Although the OPALS respiratory distress study and interventions for symptom relief reduced mortality, it is unclear whether these data are sufficient to justify implementation of the entire program. Further research should target populations and evaluate the optimal treatment regimens for patients with out-of-hospital respiratory distress, Dr. Stiell's team said.