Point of Care Ultrasound

Thanks to Sheila and Ron Bonaguro for the early Thanksgiving feast!!  Outstanding presentations by Ari, Patrick, Natalie, Kennedy and Stephen. 


Pushing the depth of field for point of care ultrasound?  Use of US to predict futility of resuscitation after medical and traumatic cardiac arrest, and as a potential alternative to the trauma pan-scan CT.

Article 1:  Flato UA, et al:  Echocardiography for prognostication during the resuscitation of intensive care unit patients with non-shockable rhythm cardiac arrest. Resuscitation  2015  Jul; 92:1-6. 

This was a Brazilian prospective, observational cohort study of 49 ICU patients with in hospital asystole or PEA cardiac arrest. Of 88 eligible patients, 39 were excluded. PEA without contractility was classified as electromechanical dissociation (EMD), and PEA with contractility as pseudo-EMD.  Two echo trained intensivists performed transthoracic echos. Rates of ROSC were 70% for pseudo-EMD, 20% EMD, and 24% for asystole.  Good ROSC percentages for all groups, but survival to hospital discharge was only seen in pseudo-EMD patients, and discharge is what counts.  Four patients survived to 180 days, all in the pseudo-EMD group, with CPC of 1, 1, 1, 2.  Echo was feasible, with maximum duration of 10 seconds, so non-disruptive to the ongoing code.  Echo also helped identify underlying etiology of arrest in selected patients, eg unexpected tamponade.  This was a very small study, and conducted in an ICU with a large number of DNR patients who were never entered into study, so different from our ED population.   

This study reinforces our usual practice of using echo to verify presence/absence of cardiac contractility and guide futility of resuscitation.  Blaivas and Fox (go ACMC!!) published a larger study in 2001 demonstrating 100% mortality in patients with asystole or PEA cardiac arrest and no cardiac contractility on bedside echo. This modality helps conserve resources (time and personnel), and may identify the underlying reason for code.  In the future, in young otherwise healthy patients with arrest, an echo demonstrating contractility may help risk stratify for ECMO.

Bottom Line:  Rather than pulse check, consider echo as the more reliable marker for viability.  Also remember end tidal CO2 to guide prognostication.  

(AHA 2015 ACLS guidelines:  “In intubated patients, failure to achieve an ETCO2 of greater than 10 mm Hg by waveform capnography after 20 minutes of CPR may be considered as one component of a multimodal approach to decide when to end resuscitative efforts but should not be used in isolation.”)

Article 2:  Inaba K et al:  FAST ultrasound examination as a predictor of outcomes after resuscitative thoracotomy: a prospective evaluation. Ann Surg  2015  Sept;262(3):512-8. 

Prospective study between 10/2010 to 5/2014 of 187 trauma patients undergoing resuscitative thoracotomy  (RT) at LAC-USC, and who received FAST before or concurrent with RT.  Thirty-six other patients (16%) received RT but no FAST; these all died.  Median transport time was 33 minutes.  Mechanism was half blunt, half penetrating.  Half lost vital signs at the scene.  FAST was adequate if able to determine presence/absence of cardiac contractility and pericardial fluid.  Seven FAST exams (4%) were inadequate.   Sustained cardiac activity was regained in 48%, but overall survival was only 3.2%, with an additional 1.6% proceeding to organ donation.  Unclear how long FAST took to perform.  Primary outcome measure was survival to discharge or organ donation.  Cardiac motion on FAST was 100% sensitive and 74% specific for the identification of survivors to discharge and organ donors.  The likelihood of survival if pericardial fluid and cardiac motion were both absent was zero. The thought at JC was that authors were trying to stress the importance of pericardial fluid being associated with potentially higher survival, but in reality, the bright line was presence or absence of cardiac contractility:  no contractility =  no survival.  Not entirely similar to our population, as at USC-LAC stab wounds to the box go immediately to the OR, regardless of initial blood pressure, and therefore these patients were not included in the study.  Additionally, we rarely perform RT on blunt trauma.  Interestingly, 4 blunt trauma patients “survived” (did not specify discharge or donor). Four of the six discharged patients were cognitively intact. 

Authors conclude that FAST represents an effective method of determining those patients who do not warrant the risk/resource burden of RT from those who may survive.  It’s a modality to tell you when to stop (NPV), not a modality to tell you when to start (PPV).

Bottom line:  In this study, if FAST had been used to select patients for resuscitative thoracotomy, all survivors would have been identified and RT rate would have been more than cut in half. 

Article 3.  Dehganzada ZA et al:  Complete ultrasonography of trauma in screening blunt abdominal trauma patients is equivalent to computed tomographic scanning while reducing radiation exposure and cost. J Trauma Acute Care Surg 2015  Aug;79(2):199-205. 

It’s tempting, right? No radiation, portable, quick, relatively inexpensive, and repeatable....there have been numerous efforts to reduce CTs by using physical examination algorithms + US in blunt torso trauma. But as a 2015 Cochrane review discussed, the overall sensitivity for FAST in blunt trauma is low. Trying to incorporate observation periods is challenging too-it’s easy for a busy trauma service to be overwhelmed.   

This study really released the fury of Stephen Jamieson.  Statistical back-fists, jabs at the inconsistent definitions, and an eventual throw-down of all the conclusions-a sight to behold.

In this 11 year retrospective single center study of 19,128 blunt abdominal trauma patients, 66% initially underwent ultrasound, and 34% CT scan.  A “Complete US of Trauma” (CUST) included 7 abdominal regions:  CUST does not equal FAST.  In the CUST group, initially 4% were “positive”, meaning injury confirmed by exploratory laparotomy or CT.  In the CT group, 7.6% positive.  The study defined false negative US as requiring a laparotomy, except when it defined false negative as having an abnormal CT.   Confusing and suspect. Overnight patients received CT.  However, there were also patients who received CT rather than CUST at surgeon discretion regardless of time of day (especially if CUST was poor quality, patient obese, seat belt injury, if hematuria, if significant abdominal pain without operative indications, or if spinal and/or pelvic fractures were suspected-hmmm, higher risk patients shuttled to CT rather than US?  This will change the test characteristics!)  Sensitivity = TP/TP + FN, or for CUST 199/199 + 86 = 70% using abnormal CT following normal US as the definition of FN.  

Mortality was higher in the U/S group (1.8% vs. 1.2%, p = 0.03, NN2Kill=166).  Mortality differences became insignificant when results were conveniently adjusted for age > 65 years or head injury.  Not clear why they felt this was justified, especially as CT group was sicker and with a higher percentage of head injuries-would expect CT group to have higher mortality.

The authors acknowledged that US is lower sensitivity/higher specificity, but then tried to justify US as a rule-out test.  As Kennedy stressed, it should instead be used as a rule-in test:  useful only if abnormal.

UCSD was averaging 4 trauma activations/day (we get about 10), with overall relatively low injury severity scores and <2% laparotomy rate.  As Harwood said, there may be a low risk population where US would be useful as a screening exam, but this study doesn’t help us figure it out.   Conclusions touting cost and radiation savings are also suspect:  no idea if CT is being used appropriately, and as UCSD now has dedicated ultrasonographers for this protocol 24/7, difficult to assess true costs.

Bottom line:  CT is still the winning modality for serious blunt abdominal trauma.  And don’t mess with Jamo.