healthmedicinet

The results of this meta-analysis show that CPR guided by EMS physicians is associated
with improved rates of ROSC, hospital admission, and hospital discharge compared with
CPR guided by paramedics in OOHCA patients.

This meta-analysis included 14 international studies with a pooled sample size of
more than 126,000 patients. Two studies from Japan 10], 17] accounted for nearly 90 % of the total sample size and thus had the biggest weight
in the meta-analysis. Because the individual studies were largely consistent in the
effect size estimate, we did not perform sensitivity analyses excluding these two
studies.

This study excluded several studies that had excellent methodology but did not directly
compare EMS-physician-guided with paramedic-guided CPR, which may influence its generalizability.
In several studies, EMS physicians provided advanced life support whereas paramedics
were only allowed to perform basic life support without the administration of resuscitation
drugs or advanced airway management. On the other hand, most countries that have a
paramedic-only EMS system allow paramedics a nearly identical scope of prehospital
practice compared with EMS physicians. Therefore, it is unclear whether our results
show predominantly the superiority of advanced life support in OOHCA over basic life
support or a true superiority of EMS-physician-guided CPR. In the multicenter Ontario
Prehospital Advanced Life Support Study (OPLAS) study, Stiell et al. 21] directly compared advanced with basic life support for OOHCA and found no positive
effect of advanced life support by paramedics on survival after OOHCA. This observation
would argue against a predominant effect of advanced life support over basic life
support.

This meta-analysis has several limitations. First, meta-analyses pool existing evidence
and are thus dependent on the scientific quality of included studies. Typically, meta-analyses
of randomized controlled trials provide the strongest and most robust evidence. In
our study, no randomized controlled trials exist that compare EMS-physician-guided
with paramedic-guided CPR and probably never will, due to the fact that whole states
and countries operate one particular EMS system and switching systems is very costly.
Despite the nonrandomized nature of studies included in this meta-analysis 4], 5], 7], 10]–20], the evidence favoring EMS-physician-guided CPR for OOHCA appears to be robust since
almost all studies found a similarly positive survival effect. Second, selection bias
may have influenced individual study results. In some EMS systems, EMS-physician-staffed
ambulances may have not been dispatched to cases of OOHCA that were futile based on
the assessment of an ambulance crew on the scene. Alternatively, EMS physicians may
have determined on scene that initiation of CPR was not appropriate, which may have
influenced the denominator of “potential cardiac arrests”. This would have limited
EMS-physician-guided CPR to OOHCA cases with a higher likelihood of successful resuscitation.
Third, the geographic distribution of EMS systems is highly variable and is often
influenced by many historical factors that all may have confounded the results of
this meta-analysis.

If the results of this meta-analysis are true—that is, EMS-physician-guided CPR provides
survival benefit in OOHCA over paramedic-guided CPR—what may be the causes? What could
EMS physicians provide beyond what paramedics already contribute? First, it has been
demonstrated that because of the limited number of invasive procedures performed by
EMS crews (like airway management, tracheal intubation, etc.) in out-of-hospital patients,
it is very difficult to obtain or maintain life-saving skills 22]–25]. As an example, even after 150 attempts at intubating the trachea in elective surgical
patients under optimal conditions in the operating room the success rate is only 95 %
26]. In the out-of-hospital setting, however, conditions are generally more difficult,
leading to more challenging prehospital airway management 27], 28]. On the other hand, EMS physicians are often anesthesiologists who maintain airway
skills in the operating room while working only part-time in EMS medicine. Second,
physician presence during CPR has been reported to increase compliance with guidelines,
resulting in less hands-off time during CPR 11].

A randomized controlled trial comparing EMS-physician-guided versus paramedic-guided
CPR will not be possible due to many reasons. Therefore, despite the significant limitations
which are readily acknowledged, this systematic review provides the only available
evidence for the effectiveness of a paramedic versus EMS-physician-based emergency
response system for prehospital cardiac arrest. Perhaps there may be opportunities
for natural experiments when EMS systems change from paramedics to EMS physicians
or vice versa. Additional analyses using large-scale registry data may help to elucidate
this topic in the future.