WANA (Washington Association of Nurse Anesthetists)


Cochrane Review: The Last Word on CRNA/MDA Outcomes


By Dan Simonson, CRNA, MHPA (WANA Secretary)

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I'd like to inform everyone about a new article that just came out (July 14, 2014) from the Cochrane Collaboration. I am very excited about it, but in order to understand its significance, you have to understand the role of the Cochrane Collaboration. Based in Great Britain, the Collaboration has become the "gold standard" of evidence based medicine (EBM).


The Collaboration does not do original research. Instead, they assemble panels of experts to systemically (meaning following a very specific algorithm and method) evaluate the research available to answer important clinical questions. These "Cochrane Reviews" as they are called, are tremendously important in that they review the state of the science available, and then the panel renders a judgment about the quality of the evidence and whether or not they feel the question has been answered sufficiently to guide medical care.


The question they asked in this particular Review was:

To assess the safety and effectiveness of different anaesthetic providers for patients undergoing surgical procedures under general, regional or epidural anaesthesia.

The fact that they even asked this question is of tremendous importance to CRNAs. And their conclusion?

As none of the data were of sufficiently high quality and the studies presented inconsistent findings, we concluded that it was not possible to say whether there were any differences in care between medically qualified anaesthetists and nurse anaesthetists from the available evidence.

I can hear you all out there groaning. "What is this, Dan? Why is this important? They didn't find any difference, in fact they said that the studies done so far were not of 'sufficiently high quality' to even show any difference!"


But let me put it to you in a different fashion, and I think you will see why I am so excited: The Cochrane Collaboration has examined the existing studies (and that would include the Silber study and any other study the mdas can come up with) and found that there is no evidence sufficient to show any difference between the two types of providers. In addition, they state in their final "Implications for Research":

A definitive answer to this question is unlikely. A randomized controlled trial is unlikely to be performed as it poses logistic difficulties in terms of allocation concealment and blinding of participants and personnel. Further, randomization may be unacceptable to health service providers, research ethics committees and patients, particularly for high-risk patients and procedures. In the meantime, hospital data could be collected or processed to better enable individual patient analyses.

In other words, any time an MDA asserts, as was done recently in an article that Jay referenced ". . . there is a significant difference, in education and training, between a physician anesthesiologist and an advanced practice nurse such as a nurse anesthetist," we can reply that despite any difference in training, the Cochrane Collaboration has found that there is no study out there that demonstrates any difference in outcomes between CRNAs and MDAs. Done. End of story.


While this isn't the type of answer, due to the subtleties involved, that we can put on billboards, it is of supreme importance in the halls of academia and amongst the health policy wonks of CMS and Congress. If the Cochrane Collaboration says it, then it is so.


I'm also excited about the Review for a more personal reason: one of the six articles chosen, amongst the thousands considered by the panel to address the question, was mine!

Simonson DC, Ahern MM, Hendryx MS. Anesthesia staffing and anesthetic complications during cesarean delivery: A retrospective analysis. Nursing Research 2007; Vol. 56, issue 1:917.

I can't tell you how much importance is assigned to articles cited for review by a Collaboration panel. In Health Care policy circles (I teach in the Master's program in Health Policy and Administration at Washington State University), it is equivalent to winning an Oscar. My Nursing and HPA colleagues are all very excited for me - and this despite the fact that the Review states that my paper was not "of sufficiently high quality." They understand the very high bar the Cochrane Collaboration sets for their reviews - to them, anything less than a Randomized Controlled Clinical Trial cannot be considered definitive.


So, to summarize: The Cochrane Collaboration has found that there is no available study demonstrating any difference between the quality of care provided by CRNAs vs. anesthesiologists, and in addition, they find that the question is unlikely ever to be answered. After fourteen years, our battle over Silber is done. Let no anesthesiologist ever try to state that the Silber study, or any other existing study, supports their claim that they have better outcomes than CRNAs.


Here is the citation:

Lewis SR,Nicholson A, SmithAF, Alderson P. Physician anaesthetists versus non-physician providers of anaesthesia for surgical patients. Cochrane Database of Systematic Reviews 2014, Issue 7.

And the "plain language summary":

Physician anaesthetists versus nurse anaesthetists for surgical patients



There is an increasing demand for surgery, pressure on healthcare providers to reduce costs, and a predicted shortfall in the number of medically qualified anaesthetists. This review aimed to consider whether anaesthesia can be provided equally effectively and safely by nurse anaesthetists (without medical qualifications) as by medically qualified anaesthetists with specialist training.


Study characteristics

The evidence was current up to 13 February 2013. We found six relevant studies, five of which were large observational studies from the US with a comparison group and with study durations from two to 11 years, and one was a much smaller twelve-week study from Haiti. There were over 1.5 million participants in the studies. Information for these studies was taken from American insurance databases (Medicare) and from hospital records. The small study was based on emergency medical care after the 2008 hurricanes in Haiti.


Key results

Most studies stated that there was no difference in the number of people who died when given anaesthetic by either a nurse anesthetist or a medically qualified anaesthetist. One study stated that there was a lower rate of death for nurse anaesthetists compared to medically qualified anaesthetists. One study stated that the risk of death was lower for nurse anaesthetists compared to those being supervised by an anaesthetist or working within an anaesthetic team, whilst another stated the risk of death was higher compared to a supervised or team approach. Other studies gave varied results. Similarly, there were variations between studies for the rates of complications for patients depending on their anaesthetic provider.


Quality of the evidence

Much of the data came from large databases, which may have contained inaccuracies in reporting. There may also be important differences between patients that might account for variation in study results, for example, whether patients who were more ill were treated by a medically qualified anaesthetist, or whether nurse anaesthetists worked in hospitals that had fewer resources. Several of the studies had allowed for these potential differences in their analysis, however it was unclear to us whether this had been done sufficiently well to allow us to be confident about the results. There was also potential confounding from the funding sources for some of these studies.



As none of the data were of sufficiently high quality and the studies presented inconsistent findings, we concluded that it was not possible to say whether there were any differences in care between medically qualified anaesthetists and nurse anaesthetists from the available evidence.

Dan Simonson




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