How reliable are capillary refill and blood pressure in determination of hemodynamic compromise?

How reliable are capillary refill and blood pressure in determination of hemodynamic compromise?

When I think back to my early days as a medical student, one of the first lessons on the physical exam involves checking central and peripheral perfusion as part of the cardiac exam.  In the newborn to assess the hemodynamic status I have often taught that while the blood pressure is a nice number to have it is important to remember that it is a number that is the product of two important factors; resistance and flow.  It is possible then that a newborn with a low blood pressure could have good flow but poor vascular tone (warm shock) or poor flow and increased vascular tone (cardiogenic shock or hypovolemia).  Similarly, the baby with good perfusion could be in septic shock and be vasodilated with good flow.  In other words the use of capillary and blood pressure may not tell you what you really want to know.

Is there a better way?

As I have written about previously, point of care ultrasound is on the rise in Neonatology.  As more trainees are being taught the skill and equipment more readily available opportunities abound for testing various hypotheses about the benefit of such technology.  In addition to my role as a clinical Neonatologist I am also the Medical Director of the Child Health Transport Team and have pondered about a future where ultrasound is taken on retrievals to enhance patient assessment.  I was delighted therefore to see a small but interesting study published on this very topic this past month. Browning Carmo KB and colleagues shared their experience in retrieving 44 infants in their paper Feasibility and utility of portable ultrasound during retrieval of sick preterm infants.  The study amounted to a proof of concept and took 7 years to complete in large part due to the rare availability of staff who were trained in ultrasound to retrieve patients.   These were mostly small higher risk patients (median birthweight, 1130 g (680–1960 g) and median gestation, 27 weeks (23–30)).  Availability of a laptop based ultrasound device made this study possible now that there are nearly palm sized and tablet based ultrasound units this study would be even more feasible now (sometimes they were unable to send a three person team due to weight reasons when factoring in the ultrasound equipment).  Without going into great detail the measurements included cardiac (structural and hemodynamic) & head ultrasounds.  Bringing things full circle it is the hemodynamic assessment that I found the most interesting.

Can we rely on capillary refill?

From previous work normal values for SVC flow are >50 ml/kg/min and for Right ventricular output > 150 ml/kg/min. These thresholds if not met have been correlated with adverse long term outcomes and in the short term need for inotropic support.  In the absence of these ultrasound measurements one would use capillary refill and blood pressure to determine the clinical status but how accurate is it?

First of all out of the 44 patients retrieved, assessment in the field demonstrated 27 (61%) had evidence using these parameters of low systemic blood flow. After admission to the NICU 8 had persistent low systemic blood flow with the patients shown below in the table.  The striking finding (at least to me) is that 6 out of 8 had capillary refill times < 2 seconds.  With respect to blood pressure 5/8 had mean blood pressures that would be considered normal or even elevated despite clearly compromised systemic blood flow.  To answer the question I have posed in this section I think the answer is that capillary refill and I would also add blood pressure are not telling you the whole story.  I suspect in these patients the numbers were masking the true status of the patient.

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How safe is transport?

One other aspect of the study which I hope would provide some relief to those of us who transport patients long distance is that the head ultrasound findings before and after transport were unchanged.  Transport with all of it’s movement to and fro and vibrations would not seem to put babies at risk of intracranial bleeding.

 

Where do we go from here?

Before we all jump on the bandwagon and spend a great deal of money buying such equipment it needs to be said “larger studies are needed” looking at such things as IVH.  Although it is reassuring that patients with IVH did not have extension of such bleeding after transport, it needs to be recognized that with such a small study I am not comfortable saying that the case is closed. What I am concerned about though is the lack of correlation between SVC and RVO measurements and the findings we have used for ages to estimate hemodynamic status in patients.

There will be those who resist such change as it does require effort to acquire a new set of skills.  I do see this happening though as we move forward if we want to have the most accurate assessment of clinical status in our patients.  As equipment with high resolution becomes increasingly available at lower price points, how long can we afford not to adapt?

Integrated Evaluation of Neonatal Hemodynamics: To Boldly Go Where No One Has Gone Before

Integrated Evaluation of Neonatal Hemodynamics: To Boldly Go Where No One Has Gone Before

Thank you to Dr El-Sayed for providing slides and a great deal of guidance in developing this post!

I am too young a Neonatologist to recall some of the changes in practice that would be considered giant leaps in my field.  Provision of antenatal steroids to accelerate lung maturity, development of ventilators and provision of surfactant to premature infants have saved millions of lives the world over and reduced morbidities from the conditions they were designed to treat.

I believe we are embarking on another such tidal wave of change that is beginning to take shape and will come crashing into the shores of our practices globally before long.  What makes it all the more exciting is that I have a front row seat to view the birth of this development.  The story begins over a decade ago with the understanding that traditional echocardiograms as performed by a Cardiologist in some instances could not provide us as Neonatologists with enough information to guide clinical decision making.  Let me state up front that the program I will be discussing would not be possible without the participation of our colleagues in Cardiology and moreover the information that they provide for many infants with congenital heart disease is critical to our practice.  What I am referring to though are those instances where we are more interested in the flow of blood or the function of the heart in the presence of a structurally normal heart.

In Canada there is no doubt that Dr. Patrick McNamara has been a pioneer in the field of Targeted Neonatal Echocardiography (TNE) and has published extensively in the field.  One such paper from 2009 highlights how TNE can be of use in the treatment of a PDA.  TNE though has expanded in use to guide treatment of such conditions as PPHN with or without BPD, heart failure, shock and also point of care functions such as determination of line placements or intravascular clots.  Additional work has been done by pioneers in Australia such as Nick Evans.  We were very fortunate to have Dr. Yasser El-Sayed train under Dr. McNamara and then return to Winnipeg to develop our own clinical program for TNE in consultation with our colleagues in Pediatric Cardiology.

Since it’s inception here the program has been utilized extensively with clinical management in many cases influenced by the findings.  We believe though that our program may be unique in the sense that the philosophy of using this technology is only as part of a larger framework as outlined in this figure. 6 stepsThe program is known as Integrated Evaluation of Neonatal Hemodynamics (INEH).  The concept is that we cannot rely on only one measure of cardiac performance or blood flow patterns.  Rather it is through consideration of six separate streams of data that we can come to an accurate conclusion. For example a patient who is hypotensive as defined by a mean blood pressure lower than their gestational age but who has adequate cerebral blood flow as measured by Near Infrared Spectroscopy, normal SVC flow and contractility, as a measure of cardiac performance with a normal lactate and urine output, may need simple observation.  Why treat with an inotrope if the end organs are not impaired in the least?

How do we accomplish this is practice? parameters usedThe integration is done by using data as shown in the next figure. Markers such as NIRS, lactate, BNP, indwelling arterial access, urine output all provide useful markers which are integrated to determine the best course of action.

I would like to provide an illustrative case.  The patient in this presentation is one who developed hypoxic ischemic encephalopathy.  If you read through the slides you will clearly see how the use of INEH brought about a significant change in the approach to the care of the infant.  Without this information we would have continued to go down a treatment path which was not addressing the issues at hand appropriately.  Please click on the link to view this presentation.

An infant with HIE and hypotension

I am proud to say that Dr. El-Sayed is spreading this message and approach globally outreach having recently given workshops in Turkey and Egypt.  TurkeyWe are also very excited that in the Fall from October 29th – 31st we will be hosting tEgypthe 10th Annual Bowman Symposium featuring Neonatal Hemodynamics.  For more information please click here.

The importance of this approach to Neonatal Care can not be emphasized enough.  With so many needs in our Health Region it is difficult to always obtain enough funds to purchase all the equipment that one needs for a service.  As such I was grateful to Dr. El-Sayed for presenting such need at a recent charitable event as shown below!

If you or someone you know is interested in this emerging field we would love to hear from you.  If you would like to attend the Bowman Symposium please contact us at:

http://chrim.ca/events/event/10th-annual-dr-jm-bowman-symposium-on-neonatal-research-2/

or email to:

[email protected]