Assessing Trauma: The Shock Index

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Trauma

Trauma is a serious foe, but time is our mortal enemy. Time from injury until someone calls 911. Response time to the scene. On-scene time and transport time. They are all clock cycles; each part of the process that spells the difference between life and death. The longer you take, the less likely your patient is to survive. Minimal BLS to get the patient to the ambulance, ALS should be performed enroute to the hospital, don’t waste time on scene with getting IV access. This is especially true for patients with internal bleeding.1

Everything we do is within the context of time. Definitive care means we are working to get the patient to a trauma center, but the care we provide to the patient en route is meant to slow down the progression of shock, buying time until we get the patient to the trauma center.1 What we do is paramount to delivering a viable patient to the trauma center, remember that white lights and cold steel will save their lives.2

Look for those subtle signs of shock, when a unit arrives on scene they try and use a variety of metrics to gauge the status of our patients. Examine skin signs and mental status as the first two indicators of shock – skin signs because patients will shunt blood immediately from the skin to the brain, the heart, and the lungs; and even in that circumstance the brain is susceptible to even slight changes in perfusion and oxygenation. If a patient is anxious it may be an indicator of those small fluctuations in perfusion and oxygenation that are affecting the brain. Any patient who is anxious and pale, even though their pulse, respirations, and BP are within “normal” limits, may be the first harbingers of shock.1

If an EMS team encounters a patient with decreased or decreasing level of consciousness and a rapid, weak, radial pulse, they need to begin to think in terms of how fast they can get them to the trauma center. These patients are decompensating right before their eyes. If they have decreasing levels of consciousness or they are unconscious, and they are bradycardic start to think in terms of getting ready to perform CPR. Does this patient have a narrowing pulse pressure? This could be indicative of pericardial tamponade, but most likely it could be a warning sign of impending decompensated shock. As cardiac output decreases because of loss of blood volume, the body will increase peripheral vascular resistance in order to compensate for this loss. As the pulse rate increases and the body exploits Starlings Law through increased myocardial contractility this can be seen in a static or decreasing systolic BP and an increasing diastolic BP. For the EMT or paramedic this is reflected in a narrowing pulse pressure.1, 3-5 If the pulse pressure starts to narrow and you don’t have muffled heart tones think shock.

Related

If during your primary assessment (X-A-B-C-D-E)1 you have one or more of the following issues:

  • X – you have to stop to control external bleeding;
  • A – address an issue relevant to a patient’s airway;
  • B – assist or take over completely breathing for a patient;
  • C- identify other sites of bleeding (internal or external) or recognize and treat a patient who is in shock; or
  • D – your disability is, is that your patient has a decreased or decreasing level of consciousness or your patient is unconscious; you have a critical trauma patient until proven otherwise.

The same is true for the Alert, Voice, Pain, Unresponsive scale (AVPU).1 If you have a patient who is P or U on A-V-P-U you have a critical trauma patient.

A New Diagnostic Tool

Shock index (SI), is known as hemodynamic stability. If a patient has an SI between 0.5 and 0.7 (the accepted range), this is an indication that they have a pumping heart, adequate blood volume, and good circulation.1,5,7-9

Why is it important? In trauma this index is commonly used to assess the amount of blood loss and degree of hypovolemic shock, but it can be used it for any patient. In clinical practice it is used to assess hypovolemic shock or the severity of non-hypovolemic shock regardless of etiology. In trauma patients with a shock index equal to or greater than 0.9, these patients are at higher risk for exsanguinating hemorrhage and have a higher mortality.4-6, 8

How to determine the shock index? Divide the heart rate by the systolic blood pressure. A normal SI is equal to or less than 0.7. An SI equal to greater than 0.9 is the most specific predictor of mortality available to the resuscitation team.4-9 It is associated with profoundly poor outcomes in patients with acute circulatory failure. When we have a patient, who has an SI of 0.8 or greater we should attempt to resuscitate them more aggressively before attempting RSI. These patients have a greater chance of decompensating when we try to perform RSI, so resuscitate first then attempt RSI.10

Treatment

You cannot have good ALS care without good BLS care. Remember: external bleeding control; keep the patient supine; make sure they are kept warm; secure their airway, make sure they are oxygenated, support their breathing and ventilations.

The triad of death is a sign that the body is in shock and is using anerobic metabolism in an attempt to oxygenate the cells. These patients will become acidotic (this is why supporting the airway and ventilations are so important), their blood won’t clot (this is why external bleeding control, direct pressure, tourniquets, hemostatic agents, etc. are critical), and because patients are going into shock they have lost the ability to produce energy so they become hypothermic. Each one of these feeds into the other, for example as the patient becomes more hypothermic they will experience escalating acidosis and bleeding will increase. Keep your patient warm because cold blood doesn’t clot.1

Intraosseous (IO) infusions have provided us a method to gain rapid vascular access. We have a variety of sites to choose from, but is one site better than any other? Thoracic and abdominal pressures may impede gravitational flow of a tibial IO.11-13 Pelvic injury may cause fluid infused through the tibia to collect in the quadrants of the abdomen. Humoral IO generally overcomes the issues associated with thoracic and abdominal pressures and will place the fluid into the central circulation via the proximal superior vena cava as opposed to the lower abdomen/pelvis in patients with a pelvic injury. Remember we are trying to maintain perfusion to the heart, the brain, and the lungs – humoral IO helps us do that.11-13

Intravenous fluids, in particular crystalloids are bad. Normal saline increases acidosis, which increases mortality (think of the trauma triad of death) and it does not stay in the vascular space. Ringers lactate is better than saline1,14 because it does not cause the acidosis that saline causes and it stays in the vascular space a little bit longer, so you don’t have to infuse as much. Both saline and ringers do not help with blood clotting or with the transport of oxygen unfortunately. Infusion of too much of either one will dilute the clotting factor and oxygen carrying capacity of the blood.1,14

Whole blood on the other hand is best. It stays in the vascular space much longer, so we need to infuse less fluid to achieve the same effect. It assists with clotting and will carry oxygen and remove CO2 and nitrogenous wastes. Whole blood will not cause the acidosis we see with normal saline. It does have a few logistical hurdles to overcome regarding storage and management.1

Remember: If you are infusing whole blood you still need to follow the precepts of damage control resuscitation in particular permissive hypotension.1 We do not want our patient normotensive. Even though we are infusing blood we can still blow out the clots which would cause the patient to hemorrhage.

An alternative to blood is lyophilized plasma.16 Lyophilized or freeze dried plasma can be stored on a shelf for two-to-five years (depending on manufacturer). Originally developed just before World War II, it could be carried in the field directly to a patient’s side. It didn’t need to be refrigerated, unlike frozen plasma once it was re-constituted it could be administered immediately. It lost favor after the Korean war because of concerns related to reactions. The German, French, and Israeli militaries were able to overcome these challenges and have deployed lyophilized plasma successfully. In the beginning of the war in Afghanistan the U.S. adopted the French and Israeli product for use by our forces.

More from the Author

Lyophilized plasma does not carry oxygen, but it does promote clotting. It stays in the vascular space as long as blood, and like blood you will not have to infuse as much plasma to achieve the same effect you do with crystalloids. If you cannot overcome the logistical issues surrounding whole blood, lyophilized plasma is an excellent option.

When we have a major trauma patient, remember catheters with a wider diameter and shorter length will allow fluids to flow faster and works best during major resuscitations. That is why when we are obtaining IV access if you have a major trauma patient when selecting an IV catheter go big or go home. A 16-gauge catheter will flow twice as much fluid in the same time frame as an 18-gauge.17 You can hang blood with an 18-gauge catheter, but if we are trying to volume infuse a patient in profound shock, in this instance bigger (and shorter) is better.

A best practice to adopt is if you must hang crystalloids use blood tubing to connect to your IV or IO catheter. When you arrive at the hospital, they will then be able to hang blood instantaneously. Plug directly into the catheter, as this will decrease the distance and reduce the friction to flow. If you must use an extension set, use a wide bore anesthesia extension set. A wide bore anesthesia extension set will have a much wider diameter and will have better flow rate than small or normal bore extensions. Smaller and even normal diameter extension sets will significantly slow IV flow rates, so they must be avoided at all costs.

If you have IO access avoid using the right-angle IV tubing extension sets that come with your IO needle. The right angle of the extension set will significantly reduce flow rates18 and will slow down administration of blood, so remember to plug directly into your IO catheter. Make this part of your protocol.

Summary

Time is our mortal enemy. The patient has none to spare. If this is a major trauma patient with internal bleeding, white lights and cold steel will save this patient. If you see pale skin in someone who is anxious, even if they are warm and dry with good vital signs, think shock. Narrowing pulse pressure without muffled heart tones? Your patient may be getting ready to decompensate.

If your SI is equal to or greater than 0.8, resuscitate before you intubate. You have a major trauma patient so be aggressive, everything from basic management FIRST (you cannot have good ALS without good BLS) then progressing to your advanced treatment.

Location, location, location: If you start an IO use the humoral site if you don’t have any contraindications. Remember: Blood is best, lyophilized plasma next best, avoid crystalloids, but if you must use them ringers lactate stays in vascular space longer than normal saline and causes less acidosis.

References

  1. PHTLS: Prehospital Trauma Life Support course manual National Association of Emergency Medical Technicians (US). 9th edition. Burlington, Massachusetts: Jones & Bartlett Learning, [2020]
  1. Collins, M. J. (2006). Hot Lights, Cold Steel: Life, Death and Sleepless Nights in a Surgeon’s First Years. Macmillan.
  1. Homan TD, Bordes SJ, Cichowski E. Physiology, Pulse Pressure. [Updated 2022 Jul 12]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK482408/
  1. Singh A, Ali S, Agarwal A, Srivastava RN. Correlation of shock index and modified shock index with the outcome of adult trauma patients: a prospective study of 9860 patients. N Am J Med Sci. 2014 Sep;6(9):450-2. doi: 10.4103/1947-2714.141632. PMID: 25317389; PMCID: PMC4193151.
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  1. Koch E, Lovett S, Nghiem T, Riggs RA, Rech MA. Shock index in the emergency department: utility and limitations. Open Access Emerg Med. 2019 Aug 14;11:179-199. doi: 10.2147/OAEM.S178358. PMID: 31616192; PMCID: PMC6698590.
  1. R. Norton, O. Kobusingye Injuries N Engl J Med, 368 (18) (2013), pp. 1723-1730
  1. G. Gutierrez, H.D. Reines, M.E. Wulf-Gutierrez Clinical review: hemorrhagic shock Crit Care, 8 (2004), pp. 373-381
  1. Olaussen, E.L. Peterson, B. Mitra, G. O’Reilly, P.A. Jennings, M. Fitzgerald Massive transfusion prediction with inclusion of the pre-hospital shock index Injury, 46 (5) (2015), pp. 822-826
  1. Althunayyan SM. Shock Index as a Predictor of Post-Intubation Hypotension and Cardiac Arrest; A Review of the Current Evidence. Bull Emerg Trauma. 2019 Jan;7(1):21-27. doi: 10.29252/beat-070103. PMID: 30719462; PMCID: PMC6360014.
  1. Lewis P, Wright C: Saving the critically injured trauma patient: A retrospective analysis of 1000 uses of intraosseous access. Emerg Med J. 2014; 31: 784.
  1. Miller L, Philbeck T, Montez D, et al: A two-phase study of fluid administration measurement during intraosseous infusion. Ann Emerg Med. 2010; 56(3): S151.
  1. Lairet J, Bebarta V, Lariret K: A comparison of proximal tibia, distal femur, and proximal humerus infusion rates using the EZ-IO intraosseous device on the adult swine (Sus scrofa) model. Prehosp Emerg Care. 2013; 17 (2): 280-284.
  1. Cherkas, D. (2011). Traumatic hemorrhagic shock: advances in fluid management. Emerg Med Pract, 13(11), 1-19.
  1. Mok G, Hoang R, Khan MW, et al. Freeze-dried plasma for major trauma – Systematic review and meta-analysis. The Journal of Trauma and Acute Care Surgery. 2021 Mar;90(3):589-602. DOI: 10.1097/ta.0000000000003012. PMID: 33507025; PMCID: PMC7899224.
  1. Zaza M, Kalkwarf KJ, Holcomb JB. Dried Plasma. Damage Control Resuscitation. 2019 May 6:145–62. doi: 10.1007/978-3-030-20820-2_8. PMCID: PMC7123378.
  1. Reddick AD, Ronald J, Morrison WG. Intravenous fluid resuscitation: was Poiseuille right? Emerg Med J. 2011 Mar;28(3):201-2. doi: 10.1136/emj.2009.083485. Epub 2010 Jun 26. PMID: 20581377.
  1. Reddick A, Ronald J, Morrison W. Intravenous fluid resuscitation: was Poiseuille right? Emerg Med J. 2011;28(3):201-202.

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