Tag Archives: shock

Complications

Vasopressin In Hemorrhagic Shock?

Leave a comment

Since almost forever, the use of pressors in hemorrhagic shock has been frowned upon. One of my mentors used to ask me, “Is your trauma patient losing norepinephrine?” My opinion was that the bag of vasopressor was only valuable for the crystalloid it was dissolved in. Even the ATLS course recommended against the use of these drugs in hemorrhagic shock.

While visiting a trauma center earlier this year, I encountered a case in which vasopressin was used in the treatment of one of these patients. When I questioned the program leadership, they provided a research paper and a white paper promoting its use.  As I always do when shown something I disagree with, I asked for the source material so I could review it myself. This is the only way to learn new tricks, and I want to share with my readers what I found.

The group at the University of Pennsylvania performed a randomized, double-blind, placebo-controlled clinical trial (in 2019) on the use of arginine vasopressin (AGP) to determine if it decreased the number of blood products transfused during resuscitation. The study took five years and included adults who received at least six units of any blood product within 12 hours of injury. Moribund patients (CPR, resuscitative thoracotomy) were excluded, as were patients with renal or coronary artery disease, and those with TBI requiring neurosurgical intervention.

A total of 100 patients were randomized, 49 to the AVP group and 51 to the placebo group. AVP dosing consisted of a bolus of 4 IU followed by an infusion of 0.04 IU/min until hemorrhage was controlled. Once this occurred, the infusion was titrated from 0 to 0.04 IU/min to maintain MAP > 65 torr. The primary outcome was the total volume of transfused blood, and secondary outcomes included the volume of crystalloid administered, vasopressor requirements, complications, and 30-day mortality.

Here are the factoids:

  • Patients were young (27 years) and typically male (93%), with 79% penetrating trauma
  • At 48 hours, patients who were given AVP received significantly less blood products (1.4L vs 2.9L), but the same amount of crystalloid (9.9L vs 11L)
  • Mortality (12% for both groups) and complications were similar between the groups (55% AVP vs 64% placebo)
  • Strangely, venous thrombosis was lower in the AVP group (11% vs 34%)

The authors concluded that the use of AVP in hemorrhagic shock resulted in a decrease in the volume of transfused blood products. They recommended further studies to determine if there were survival or complication avoidance benefits.

Bottom line: Surprise! This is a very high-quality study, and I’m surprised I missed it five years ago. It provides compelling evidence to support the use of vasopressin in patients with hemorrhagic shock. The authors speculate that this pressor may overcome the vasoplegia that may occur in late-stage shock. Although this is more common in septic shock, it can also occur with massive hemorrhage.

There have been further studies, mainly meta-analyses, that provide additional support for this work. To date, no studies have been powered to show improvements in survival or complications. 

This work is strong enough on its own that it should be okay to modify your practice based on it. The State of Arkansas has generated a white paper that promotes the use of AVP in any patient who requires MTP activation. Although this indication differs from the six-unit requirement in this research paper review, it is more likely to be remembered if implemented at the start of the MTP. This is very similar to the administration of TXA, which should also be considered at the beginning of the MTP.

However you choose to do it, here is the algorithm:

  • Give a 4 IU bolus of AVP
  • Immediately begin a 0.04 IU/min infusion
  • Once hemorrhage has been definitively controlled, titrate to a mean arterial pressure > 65 using 0-0.04 IU/min
  • Stop after 48 hours

References:

  • Effect of Low-Dose Supplementation of Arginine Vasopressin on Need for Blood Product Transfusions in Patients With Trauma and Hemorrhagic Shock: A Randomized Clinical Trial. JAMA Surg. 2019 Nov 1;154(11):994-1003. doi: 10.1001/jamasurg.2019.2884. PMID: 31461138; PMCID: PMC6714462.
  • Arkansas White Paper: Arkansas Trauma System Evidence-Based Guidelines for Use of Vasopressin in Shock (click to download)
  • Effects of Vasopressin Receptor Agonists during the Resuscitation of Hemorrhagic Shock: A Systematic Review and Meta-Analysis of Experimental and Clinical Studies. J Pers Med. 2023 Jul 16;13(7):1143. doi: 10.3390/jpm13071143. PMID: 37511756; PMCID: PMC10381354.

Shout-out to Lindsay Graves, the TPM at Baptist Hospital in Little Rock, who shared this work with me.

Imaging, Resuscitation

ACS Trauma Abstract #6: Scanning Unstable Trauma Patients???

Leave a comment

If you’ve read my stuff for very long, you know I frown on sending unstable patients anywhere but to the OR. Instability tends to get worse, and that always happens at inopportune locations like hallways, elevators, and CT scanners. Imagine my surprise when I noticed an abstract being presented at the Clinical Congress of the American College of Surgeons this week suggesting that it was okay to scan hemodynamically unstable patients before “definitive therapy.”

Here’s the title:

“Computed tomography in hemodynamically abnormal thoracoabdominal trauma safely enhances surgical triage”

The devil is in the details and the language. This group from USC included all patients who were hemodynamically abnormal on arrival to the trauma bay but who normalized to SBP > 90 during the resuscitation were included.  A total of 253 of these patients were reviewed over a 9 year period, and the usual variables were analyzed (mortality, complications, hospital, ICU, and vent days, etc).

Here are the factoids:

  • Of the 253 patients studied, 45 went to straight to OR and 208 were taken to CT
  • Injury severity was identical for the two groups
  • Lengths of stay and mortality were not different, but only p values were given
  • Patients taken to CT cleared their lactic acidosis faster (12 vs 5 hours), and used a bit less plasma and significantly less blood transfusions
  • The OR group underwent more procedures (31% vs 13%), although what these were and when they were performed is not listed

Bottom line: The title of this abstract is misleading, and may fool those who don’t read the rest of the abstract. It should read:

“Computed tomography in previously hemodynamically abnormal thoracoabdominal trauma safely enhances surgical triage”

Someone who just skims through this issue of the journal may get the idea that it’s okay to scan an unstable patient. The authors are not saying this at all. If you read the conclusion carefully, you can see that the patients had to be resuscitated to a SBP > 90 before they considered taking to scan. And they did that for the majority of these patients.

The real question is, why do the scanned patients clear their lactic acidosis faster, need less blood, and undergo fewer procedures? It appears that there is some bias or selection process in play. Otherwise, why not use the magic CT scanner to make them all better?

Reference: Computed tomography in hemodynamically abnormal thoracoabdominal trauma safely enhances surgical triage. JACS 225(4S2):e175-176, 2017.

General

EAST 2016: (F)utility of CPR In Hemorrhagic Shock

Leave a comment

Ahh, another (f)utility study. Does it work, or doesn’t it? And yes, I know. It’s another animal study. But it may give us a glimpse of where we are really going with this. 

A team at the University of Tennessee – Knoxville devised a dog experiment to study how well performing CPR works in critically hypovolemic animals. They used three groups of dogs that received a severe shock insult: hemorrhage until loss of pulse, then waiting for 30 minutes in that pulseless state. At that point, one of three interventions was performed for 20 minutes.

One group received CPR only, another group underwent CPR plus fluid administration, and the last group got fluids only. 

Here are the factoids:

  • The insult to all three groups was similar.
  • Vital signs and lab studies were similar in the CPR+fluid and fluid only groups.
  • The CPR only group had significantly lower mean arterial pressures and higher pulse rates than the other CPR+fluid and fluid only groups.
  • Ejection fraction was lower in the CPR only group, and it also had a higher incidence of end organ damage. 
  • Two of the six dogs in the CPR only group died before the end of the study.

Bottom line: Tread with caution here. It makes sense that pounding on an empty tank won’t do much. But this study doesn’t exactly prove this. Only the vital signs measurements were significantly different. All other results are just trends in this very small study. And finally, dogs are (obviously) different than people, in their physiology and their chest wall shape. This can certainly make a difference, and does not mean that we should abandon CPR in humans in hemorrhagic shock.

Reference: Utility of CPR in hemorrhagic shock, a dog model. EAST 2016 Oral abstract #8, resident research competition.

General
Gallery Leave a comment

Does Initial Hematocrit Predict Shock?

Everything you know is WRONG!

The classic textbook teaching is that trauma patients bleed whole blood. And that if you measure the hematocrit (or hemoglobin) on arrival, it will approximate their baseline value because not enough time has passed for equilibration and hemodilution. As I’ve said before, you’ve got to be willing to question dogma!

The trauma group at Ryder in Miami took a good look at this assumption. They drew initial labs on all patients requiring emergency surgery within 4 hours of presentation to the trauma center. They also estimated blood loss in the resuscitation room and OR and compared it to the initial hematocrit. They also compared the hematocrit to the amount of crystalloid and blood transfused in those areas.

Patients with lower initial hematocrits had significantly higher blood loss and fluid and blood replacement during the initial treatment period. Some of this effect may be due to the fact that blood loss was underestimated, or that prehospital IV fluids diluted the patient’s blood counts. However, this study appears sound and should prompt us to question the “facts” we hear every day.

Bottom line: Starling was right! Fluid shifts occur rapidly, and initial hematocrit or hemoglobin may very well reflect the volume status of patients who are bleeding rapidly. If the blood counts you obtain in the resuscitation room come back low, believe it! You must presume your patient is bleeding to death until proven otherwise.

Reference: Initial hematocrit in trauma: A paradigm shift? J Trauma 72(1):54-60, 2012.

General

Clinical Tip: The Flat Vena Cava in Blunt Trauma

Leave a comment

Trauma patients who are hypotensive in the Emergency Department can only be transported to one of two places: the operating room or the morgue. With rare exception, they should never be taken outside the department (e.g. CT scan) because of the fear that they may arrest in an area that is not conducive to efficient resuscitation.

Sometimes patients are initially stable but decompensate later. Since most stable blunt trauma patients end up in CT scan, perhaps there is some telltale sign that can predict later deterioration. A recent Japanese paper looked at the “flatness” of the inferior vena cava as seen on the abdominal CT scan as a predictor of hemodynamic decompensation in the first 24 hours.

A small cohort of 114 patients was used in this prospective study. The vena cava was evaluated at the level of the renal veins. The flatness of the IVC was determined by dividing the transverse diameter by the anteroposterior (AP) diameter. A flat IVC was defined as a transverse to AP diameter ratio of more than 4:1. The ratio in normal patients was about 2:1. See the figure for details.

Patients who had a flat IVC required significantly more blood transfusions, crystalloid infusions within 2 hours of admission, and were more likely to proceed to the OR within the first 24 hours of their hospital stay.

Bottom Line: Assuming that you are only taking stable blunt trauma patients to CT, the incidental finding of a flat vena cava should increase your paranoia levels and lower your threshold for ordering blood and getting the trauma surgeons involved. 

Reference: Predictive value of a flat inferior vena cava on initial computed tomography for hemodynamic deteroration in patients with blunt torso trauma. J Trauma 69(6):1398-1402, 2010.