ResUS in the Literature: Serial FEEL and Termination of Resuscitation

Journal: Resuscitation

Date:April 2016

Format: Prospective Observational Study

Method: A prospective observational study of non-consecutive non-trauma adult patients with out of hospital cardiac arrest (OHCA) using the ResUS FEEL protocol. ResUS was performed every two minutes during pulse check for <10s throughout resuscitation and findings were recorded as video clips.

Results: 

• 48 patients enrolled
• ROSC patients had standstill for 2.86 ± 2.07min
• Non-ROSC patients had standstill for 20.30 ± 8.42min
• Standstill ≥10min predicts non-ROSC with a sensitivity of 90.0% and specificity of 100%.
• The presence of cardiac activity on initial FEEL was not identified in 40 patients, but 21 had ROSC. 

Figure: A receiver operating characteristic (ROC) curve determining the accuracy of serial echocardiographic cardiac standstill duration for predicting non-return of spontaneous circulation. The area under the receiver operating characteristic curve is 0.991 (p < 0.001).


Commentary: We have seen previously that loss of cardiac activity on ResUS is a strong negative predictor of ROSC. Current study authors note cardiac standstill on initial ResUS could not predict non-ROSC and cannot be used as a TOR rule, arguing that serial ResUS can better determine ROSC.

Of note in this study:
-clinicians were not blinded to the echocardiography findings (bias). 
-patients were committed to the same 30 min duration of resuscitation
-efforts were terminated early in no patients.
-unlike other studies, videos were recorded and reviewed

Question:
What was the duration of cardiopulmonary resuscitation prior to ED arrival?

References:

Kim HB, Suh JY, Choi JH, Cho YS. Can serial focussed echocardiographic evaluation in life support (FEEL) predict resuscitation outcome or termination of resuscitation (TOR)? A pilot study. Resuscitation. 2016 Apr;101:21-6.

ResUS in the Literature: Finally!! A Fluid ResUS Protocol

Journal: Journal of Critical Care

Date: Feb 2016

Format: Review 

The authors review and present an "evidence-informed protocol" of fluid resuscitation strategies using ResUS. 

In particular:

• The role of IVC  ResUS for estimating fluid responsiveness, with particular attention to:
• IVC distensibility
• IVC diameter
• IVC collapsability
• Lung ResUS guided fluid resuscitation with particular attention to
• Identifying pulmonary edema
• Step-wise approach to performing their IVC + Lung integrated ResUSprotocol for fluid resuscitation, fluid testing, and fluid restriction. 

Commentary: Its about time someone has suggested a clean, simple, and elegant method for integrating ResUS into the fluid resuscitationstrategy beyond looking at the IVC. Most impressive is that cardiac ResUS not included in this protocol, opening the possibility of non-expert (and even non-MD) use in patient care. The proposed protocol has not been validated. Looking forward to the prospective trails.

Reference:  
Lee CW, Kory PD, Arntfield RT. Development of a fluid resuscitation protocol using inferior vena cava and lung ultrasound.J Crit Care. 2016 Feb;31(1):96-100. 

ResUS in the Literature: Technological Requirements

Journal: Anesthesiology Intensive Therapy

Date: November 2015

Format: Review

The authors put forth technological and machine requirements needed to perform ResUS using the SESAME protocol. 

In the article, the authors review:

• The role of ResUS in cardiac arrest
• Ideal equipment specifications including: 
• size
• "boot up" time 
• transducer selection(s)
• imaging filters
• presets 
• keyboard specs, 
• gain, depth and B-Mode functionality.
• Step-wise approach to performing the SESAME protocol along with regionally specific technical considerations
• Common sense strategies to fine-tune the SESAME protocol, such as have an AED or percardiocentesis kit integrated onto the machine cart.

Commentary: Technical innovation has occurred rapidly in the field of point of care ultrasound, and yet there are few studies on the minimum requirements of ultrasound equipment in the setting of cardiac arrest. The authors suggest some minimum machine requirements for performing the SESAME protocol, although there is little empiric data to support their recommendations. A discussion regarding the pros and cons of the various machine functions and technical requisites seems long overdue.The SESAME protocol itself has not been validated.

Reference:
Lichtenstein D, Malbrain ML.Critical care ultrasound in cardiac arrest. Technological requirements for performing the SESAME-protocol - a holistic approach. Anaesthesiol Intensive Ther. 2015;47(5):471-81.

Posted by: A Adedipe, MD

ResUS in the Literature: RUSH VTI Protocol

Journal:  Journal of Ultrasound

Title: Rapid Ultrasound in Shock (RUSH) Velocity-Time Integral

Authors: Blanco P, Aguiar FM, Blaivas M

Date: 2015

Format: Technical Innovation (Correspondence)

The authors propose adding the calculation of velocity-time integral (VTI) from the left ventricular outflow tract (LVOT) in patients undergoing ResUS with the RUSH protocol.

In the article, the authors review:

• How VTI is measured
• How to interpret VTI in various physiologic states
• Feasibility of integrating VTI measures into RUSH protocol
• Anatomic considerations of VTI (LVOT pathology, measures from different sites)

Commentary: Few studies have demonstrated the validity of the  RUSH exam (less than 5 studies to date?) let alone VTI in critically ill patients.  While likely not time consuming or inaccurate in the hands of experts, is the VTI truly generalizable? Key question remains whether either of these measures (RUSH and VTI) effects patients outcomes.

Reference:
Blanco P, Aguiar FM, Blaivas M. Rapid Ultrasound in Shock (RUSH) Velocity-Time Integral: A Proposal to Expand the RUSH Protocol. J Ultrasound Med. 2015 Sep;34(9):1691-700.

Posted by: A Adedipe, MD

ResUS Pearl: IVC Ultrasound & Volume Assessment

                 

Background:
Determining when to give intravascular volume to hypotensive patients is an imperfect science. Commonly used methods to assess volume status include urine output, passive leg raise, arterial pulse pressure variation, jugular venous pressure, fluid challenge as well as IVC collapsibility.  US-guided assessment of the IVC is an attractive option because it is rapid, reproducible, noninvasive and does not require specialized monitoring equipment. Of note, studies have varying results about the accuracy of IVC ultrasound to predict fluid responsiveness.

Key Physiology:
The IVC serves as a high-capacity intravascular reservoir for the circulatory system.
In spontaneous ventilation the ambient pressure in the thoracic cavity is slightly negative, becoming more negative during inspiration.  With inspiration blood is driven from the IVC into the right heart, which reduces IVC volume and can result in collapse.With positive pressure mechanical ventilation the ambient pressure is positive (i.e., PEEP) and becomes more positive during inspiration. During expiration this pressure is reduced and the IVC can collapse.
The theory behind IVC ultrasound is that if the IVC collapses more or if its baseline diameter is smaller, this represents lower intravascular volume and may predict volume responsiveness. There are several conditions that will enlarge the IVC diameter, confounding such measurements, including:

Cardiac: tamponade, right heart failure
Pulmonary: tension pneumothorax, pulmonary embolism, pulmonary hypertension, status asthmaticus

The bottom line:
Despite the sweet sweet physiology behind IVC ultrasound, the myriad studies don’t give us reason to rely on it to titrate resuscitation of our hypotensive patients, although the data is promising at the extremes of the IVC diameter. LifeInTheFastLane has a great summary.

A very collapsible or very small IVC is likely fluid responsive
Spontaneously breathing patients: IVC diameter <0.9cm
Ventilated patients: IVC diameter <1.2 cm or 18%+ collapse

A very large or non-collapsible IVC isn’t fluid responsive
Ventilated patients: IVC diameter >2.5cm

References

Submitted by: K Tiemeier, MD