In some circles, ‘wuntwuntwun’ is in danger of becoming the new dogma of trauma fluid replacement (ie. 1 unit of plasma and 1 unit of platelets for every unit of red cells). Since it takes longer to thaw some plasma than it does to throw in some O negative packed red cells, some really sick patients may be dead before they get the plasma, biasing comparisons that show a reduced mortality in patients who were still alive to receive plasma. This ‘survivor bias’ has been suggested as a reason that high plasma:red cell ratios are associated with mortality reduction, although this has been challenged.
The survivor bias explanation receives some new support by the following (small) study from Journal of Trauma:
BACKGROUND: In light of recent data, controversy surrounds the apparent 30-day survival benefit of patients achieving a fresh frozen plasma (FFP) to packed red blood cell (PRBC) ratio of at least 1:2 in the face of massive transfusions (MT) (≥10 units of PRBC within 24 hours of admission). We hypothesized that initial studies suffer from survival bias because they do not consider early deaths secondary to uncontrolled exsanguinating hemorrhage. To help resolve this controversy, we evaluated the temporal relationship between blood product administration and mortality in civilian trauma patients receiving MT.
METHODS: Patients requiring MT over a 22-month period were identified from the resuscitation registry of a Level I trauma center. Shock severity at admission and timing of shock-trauma admission, blood product administration, and death were determined. Patients were divided into high- and low-ratio groups (≥1:2 and<1:2 FFP:PRBC, respectively) and compared. Kaplan-Meier analysis and log-rank test was used to examine 24-hour survival.
RESULTS: One hundred three patients (63% blunt) were identified (66 high-ratio and 37 low-ratio). Those patients who achieved a high-ratio in 24 hours had improved survival. However, severity of shock was less in the high-group (base excess: -8.0 vs. -11.2, p=0.028; lactate: 6.3 vs. 8.4, p=0.03). Seventy-five patients received MT within 6 hours. Of these, 29 received a high-ratio in 6 hours. Again, severity of shock was less in the high-ratio group (base excess: -7.6 vs. -12.7, p=0.008; lactate: 6.7 vs. 9.4, p=0.02). For these patients, 6-hour mortality was less in the high-group (10% vs. 48%, p<0.002). After accounting for early deaths, groups were similar from 6 hours to 24 hours.
CONCLUSIONS: Improved survival was observed in patients receiving a higher plasma ratio over the first 24 hours. However, temporal analysis of mortality using shorter time periods revealed those who achieve early high-ratio are in less shock and less likely to die early from uncontrolled hemorrhage compared with those who never achieve a high-ratio. Thus, the proposed survival advantage of a high-ratio may be because of selection of those not likely to die in the first place; that is, patients die with a low-ratio not because of a low-ratio.
The authors state “The current study underscores the need for well-designed prospective studies to address the important question of which ratio results in improved survival and stresses the importance of timing of blood product administration as this may impact survival.”
Improved survival after hemostatic resuscitation: does the emperor have no clothes?
J Trauma. 2011 Jan;70(1):97-102
Tag Archives: outcome
Helicopters between hospitals
More National Trauma Databank analysis coming out in favour of helicopter transport: this time looking at interhospital transfer:
Background: Helicopter transport (HT) is frequently used for interfacility transfer of injured patients to a trauma center. The benefits of HT over ground transport (GT) in this setting are unclear. By using a national sample, the objective of this study was to assess whether HT impacted outcomes following interfacility transfer of trauma patients.
Methods: Patients transferred by HT or GT in 2007 were identified using the National Trauma Databank (version 8). Injury severity, resource utilization, and survival to discharge were compared. Stepwise logistic regression was used to determine whether transport modality was a predictor of survival after adjusting for covariates. Regression analysis was repeated in subgroups with Injury Severity Score (ISS) ≤15 and ISS >15.
Results: There were 74,779 patients transported by helicopter (20%) or ground (80%). Mean ISS was higher in patients transported by helicopter (17 ± 11 vs. 12 ± 9; p < 0.01) as was the proportion with ISS >15 (49% vs. 28%; odds ratio [OR], 2.53; 95% confidence interval [CI], 2.43-2.63). Patients transported by helicopter had higher rates of intensive care unit admission (54% vs. 29%; OR, 2.86; 95% CI, 2.75-2.96), had shorter transport time (61 ± 55 minutes vs. 98 ± 71 minutes; p < 0.01), and had shorter overall prehospital time (135 ± 86 minutes vs. 202 ± 132 minutes; p < 0.01). HT was not a predictor of survival overall or in patients with ISS ≤15. In patients with ISS >15, HT was a predictor of survival (OR, 1.09; 95% CI, 1.02-1.17; p = 0.01).
Conclusions: Patients transported by helicopter were more severely injured and required more hospital resources than patients transported by ground. HT offered shorter transport and overall prehospital times. For patients with ISS >15, HT was a predictor of survival. These findings should be considered when developing interfacility transfer policies for patients with severe injuries.
Helicopters Improve Survival in Seriously Injured Patients Requiring Interfacility Transfer for Definitive Care
J Trauma. 2011 Feb;70(2):310-4.
End tidal CO2 in cardiac arrest
Measuring end-tidal CO2 in cardiac arrest patients is helpful for
- confirming tracheal tube placement
- assessing the effectiveness of chest compressions
- predicting likelihood of return of spontaneous circulation (ROSC), in that a persistently low ETCO2 tends to predict death, whereas a high or rising ETCO2 is associated with a higher chance of ROSC.
It may be however that its predictive ability depends on the type of cardiac arrest, and how far into the resuscitation you’ve got when you measure the ETCO2. Consider this new study from Slovenian pre-hospital emergency physicians:
Methods: The study included two cohorts of patients: cardiac arrest due to asphyxia with initial rhythm asystole or pulseless electrical activity (PEA), and cardiac arrest due to arrhythmia with initial rhythm VF or pulseless VT. The causes of asphyxia were: asthma, severe acute respiratory failure, tumor of the airway, suicide by hanging, acute intoxication, pneumonia and a foreign body in the airway.PetCO2 was measured for both groups immediately after intubation and repeatedly every minute, both for patients with or without return of spontaneous circulation (ROSC). We compared the dynamic pattern of PetCO2 between groups. Resuscitation procedures were performed by an emergency medical team (emergency medical physician and two emergency medical technicians or registered nurses) in accordance with 2005 ERC Guideline
Results: Between June 2006 and June 2009 resuscitation was attempted in 325 patients and in this study we included 51 patients with asphyxial cardiac arrest and 63 patients with VF/VT cardiac arrest. The initial values of PetCO2 were significantly higher in the group with asphyxial cardiac arrest (6.74 ± 4.22 kilopascals (kPa) versus 4.51 ± 2.47 kPa; P = 0.004). In the group with asphyxial cardiac arrest, the initial values of PetCO2 did not show a significant difference when we compared patients with and without ROSC (6.96 ± 3.63 kPa versus 5.77 ± 4.64 kPa; P = 0.313). We confirmed significantly higher initial PetCO2 values for those with ROSC in the group with primary cardiac arrest (4.62 ± 2.46 kPa versus 3.29 ± 1.76 kPa; P = 0.041).
A significant difference in PetCO2 values for those with and without ROSC was achieved after five minutes of CPR in both groups (asphyxial arrest: 6.09 ± 2.63 kPa versus 4.47 ± 3.35 kPa; P = 0.006; primary arrest: 5.63 ± 2.01 kPa versus 4.26 ± 1.86; P = 0.015)
In mmHg, the PetCO2 values for those with and without ROSC after five minutes of CPR was: asphyxial arrest: 42.3 ± 20 mmHg versus 34 ± 25.5 mmHg; P = 0.006; primary arrest: 42.8 ± 15.3 mmHg versus 32.3 ± 14.1 mmHg; P = 0.015
Graphically, this difference in ROSC vs non-ROSC PetCO2 for both groups appeared to be even greater at ten minutes, with higher statistically significance (p<0.001), although the values of PetCO2 are not given in the paper.
In all patients with ROSC the initial PetCO2 was again higher than 1.33 kPa (10.1 mmHg).
Conclusions: The dynamic pattern of PetCO2 values during out-of-hospital CPR showed higher values of PetCO2 in the first two minutes of CPR in asphyxia, and a prognostic value of initial PetCO2 only in primary VF/VT cardiac arrest. A prognostic value of PetCO2 for ROSC was achieved after the fifth minute of CPR in both groups and remained present until final values. This difference seems to be a useful criterion in pre-hospital diagnostic procedures and attendance of cardiac arrest.
The authors summarise with the following key messages:
- Initial values of PetCO2 are higher in asphyxial cardiac arrest than in primary cardiac arrest.
- Initial values of PetCO2 in asphyxial cardiac arrest do not have a prognostic value for resuscitation outcome.
- The prognostic value of PetCO2 for ROSC was achieved after the fifth minute of CPR in both groups and remained present until the final values.
- The values of PetCO2 seem to be useful in differentiating the causes of cardiac arrest in a pre-hospital setting.
I think that last one’s a bit of a stretch. For me, this paper confirms that the longer you are into a cardiac arrest resuscitation, the worse news a low PetCO2 is. The lack of predictive value of initial PetCO2, particularly in the asphyxia group, is interesting but not surprising.
The dynamic pattern of end-tidal carbon dioxide during cardiopulmonary resuscitation: difference between asphyxial cardiac arrest and ventricular fibrillation/pulseless ventricular tachycardia cardiac arrest
Critical Care 2011, 15:R13
Prone ventilation in ARDS
Prone ventilation can improve refractory hypoxaemia in ARDS but its effects on mortality have not been impressive in some studies which may be underpowered or include patients with less severe hypoxaemia. An updated meta-analysis showed significantly reduced ICU mortality in the four recent studies that enrolled only patients with ARDS, as opposed to ARDS/ALI (odds ratio = 0.71; 95% confidence interval = 0.5 to 0.99; P = 0.048; number needed to treat = 11). There may also be benefit from a greater duration of prone positioning.
An updated study-level meta-analysis of randomised controlled trials on proning in ARDS and acute lung injury
Critical Care 2011, 15:R6 Full text
Extracorporeal CPR
Extracorporeal cardiopulmonary resuscitation (E-CPR) using extracorporeal membrane oxygenation (ECMO) support during inhospital cardiac arrest has been attempted to improve the outcome of cardiopulmonary resuscitation (CPR). A retrospective, single-center, observational study from Korea analysed a total of 406 adult patients with witnessed inhospital cardiac arrest receiving cardiopulmonary resuscitation for >10 mins.
How their system works: An ECMO cart was transported to the CPR site within 5–10 mins during the day and within 10–20 mins during the night shift. The decision to use E-CPR was dependent on the CPR team leader. Application of ECMO was usually considered under conditions of prolonged arrest (when there was no ROSC after 10–20 mins of CPR), recurrent arrest (when ROSC could not be maintained), or when the patient could not be expected to recover as a result of underlying severe left ventricular dysfunction or coronary artery disease despite a short CPR duration (end-stage heart failure requiring transplantation, left main coronary artery occlusion, etc)
The primary end point was a survival discharge with minimal neurologic impairment.
85 patients underwent E-CPR and 321 underwent C- CPR. ECMO implantation was successful in 94.1% (80 of 85) in the E-CPR group, except for three cannulation failures and two ECMO flow failures. There was a signficantly greater proportion of patients with primary cardiac disease in the E-CPR group. Propensity score matching was used to balance the baseline characteristics and cardiopulmonary resuscitation variables that could potentially affect prognosis. In the matched population (n = 120), the survival discharge rate with minimal neurologic impairment in the extracorporeal cardiopulmonary resuscitation group was significantly higher than that in the conventional cardiopulmonary resuscitation group (odds ratio of mortality or significant neurologic deficit, 0.17; 95% confidence interval, 0.04-0.68; p = .012). In addition, there was a significant difference in the 6-month survival rates with minimal neurologic impairment (hazard ratio, 0.48; 95% confidence interval, 0.29-0.77; p = .003; p <.001 by stratified log-rank test). In the subgroup based on cardiac origin, extracorporeal cardiopulmonary resuscitation also showed benefits for survival discharge (odds ratio, 0.19; 95% confidence interval, 0.04-0.82; p = .026) and 6-month survival with minimal neurologic impairment (hazard ratio, 0.56; 95% confidence interval, 0.33-0.97; p = .038; p = .013 by stratified log-rank test).
The authors conclude that extracorporeal cardiopulmonary resuscitation showed a survival benefit over conventional cardiopulmonary resuscitation in patients who received cardiopulmonary resuscitation for >10 mins after witnessed inhospital arrest, especially in cases of cardiac origin. These results contrast with these recently published French findings in patients receiving ECMO after out-of-hospital cardiac arrest.
Extracorporeal cardiopulmonary resuscitation in patients with inhospital cardiac arrest: A comparison with conventional cardiopulmonary resuscitation
Crit Care Med. 2011 Jan;39(1):1-7
Better outcomes with conventional CPR
A very large nationwide Japanese observational study examined outcomes in out-of-hospital cardiac arrest patients who received CPR from lay rescuers. They compared conventional CPR (with mouth-to-mouth and chest compressions) with compression-only CPR. Over 40 000 patients were included.
Conventional CPR was associated with better outcomes than chest compression only CPR, for both one month survival (adjusted odds ratio 1.17, 95% confidence interval 1.06 to 1.29) and neurologically favourable one month survival (1.17, 1.01 to 1.35). Neurologically favourable one month survival decreased with increasing age and with delays of up to 10 minutes in starting CPR for both conventional and chest compression only CPR. The benefit of conventional CPR over chest compression only CPR was significantly greater in younger people in non-cardiac cases (P=0.025) and with a delay in start of CPR after the event was witnessed in non-cardiac cases (P=0.015) and all cases combined (P=0.037).
The authors conclude that conventional CPR is associated with better outcomes than chest compression only CPR for selected patients with out of hospital cardiopulmonary arrest, such as those with arrests of non-cardiac origin and younger people, and people in whom there was delay in the start of CPR.
Outcomes of chest compression only CPR versus conventional CPR conducted by lay people in patients with out of hospital cardiopulmonary arrest witnessed by bystanders: nationwide population based observational study
BMJ 2011; 2011; 342:c7106 Full Text
Helicopters and trauma: systematic review
In the midst of reconfiguring its trauma systems, the United Kingdom’s National Health Service needed to evaluate the cost effectiveness of helicopter emergency medical services (HEMS). A systematic literature review was undertaken of all population-based studies evaluating the impact on mortality of helicopter transfer of trauma patients from the scene of injury. The authors also attempted to analyse whether it is the helicopter as a transport platform or the standard of the emergency medical service that accounts for any differences seen.
A search of the literature revealed 23 eligible studies. 14 of these studies demonstrated a significant improvement in trauma patient mortality when transported by helicopter from the scene. 5 of the 23 studies were of level II evidence with the remainder being of level III evidence.
Only one eligible study assessed HEMS in the UK. The other papers reported data from the USA, Italy, Australia, the Netherlands, Germany and South Africa.
The majority of studies show a mortality benefit with HEMS: fourteen studies reported results that demonstrated a significant mortality rate improvement with HEMS, four reported data that did not reach significance and five did not report whether results reached significance.
The authors suggest this variation may be a result of any of the following factors, and provide a thorough discussion of the literature pertaining to each of them:
- Transport of a physician to the scene
- Transport of advanced airway skills to the scene
- Transporting a team experienced in managing trauma patients
- Triage to the definitive treatment facility
The full text of the review is available at the link below.
Is it the H or the EMS in HEMS that has an impact on trauma patient mortality? A systematic review of the evidence
EMJ 2010;27(9):692-701 (Free Full Text)
A French FIRST in pre-hospital medicine
A contribution has been made to the literature supporting physician intervention in some pre-hospital trauma patients, in the form of the FIRST study: French Intensive care Recorded in Severe Trauma. 
Not exactly the class 1 evidence we’d (well, I’d) like to see, but a prospective study from France comparing outcomes in patients treated by routine pre-hospital providers with those managed in the field by emergency physicians working for SMUR (Service Mobile d’Urgences et de Réanimation). Primary outcome was 30-day mortality. Only patients admitted to an ICU were included, and researchers were not blinded to which group (SMUR vs nonSMUR) patients belonged. A large group of SMUR patients (2513) was compared with a much smaller (190) nonSMUR group.
Patients were sicker in the SMUR group (lower GCS and SpO2, higher Injury Severity Score, higher frequency of abnormal pupils). Unadjusted mortality was not significantly different but when adjustment for ISS and physiological status was made (I don’t really understand how this was done), SMUR care was significantly associated with a reduced risk of 30-day mortality (OR: 0.55, 95% CI: 0.32-0.94, p = 0.03).
Lots of interesting points in this study, most of which ask more questions that they answer. The French pre-hospital physicians have an aggressive approach to trauma resuscitation, doing rapid sequence intubation in more than a half of their patients and even starting catecholamine infusions as a fluid-sparing strategy in shocked patients. The full text link is worth a read for those interested in this area of medicine.
Medical pre-hospital management reduces mortality in severe blunt trauma: a prospective epidemiological study
Critical Care 2011, 15:R34
Full text as provisional PDF
Improved survival with modified CPR
A large randomised controlled trial1 on out-of-hospital cardiac arrest patients compared standard CPR with CPR augmented by two modifications:
- active compression-decompression using a hand-held suction device to compress the chest. The device is attached to the chest of the patient during CPR and the rescuer actively lifts the chest upwards after each compression, which are done at a rate of 80/min
- augmented negative intrathoracic pressure using an impedance threshold device, which is a valve that limits passive air entry into the lungs during chest compressions, thereby reducing intrathoracic pressure and increasing blood flow to vital organs
The primary study endpoint was survival to hospital discharge with favourable neurological function.
Funding issues resulted in premature cessation of the study. 47 (6%) of 813 controls survived to hospital discharge with favourable neurological function compared with 75 (9%) of 840 patients in the intervention group (odds ratio 1·58, 95% CI 1·07–2·36; p=0·019]. 74 (9%) of 840 patients survived to 1 year in the intervention group compared with 48 (6%) of 813 controls (p=0·03), with equivalent cognitive skills, disability ratings, and emotional-psychological statuses in both groups. The overall major adverse event rate did not differ between groups, but more patients had pulmonary oedema in the intervention group (94 [11%] of 840) than did controls (62 [7%] of 813; p=0·015).
An accompanying editorial2 points out that previous studies in animal models of cardiac arrest gave reassuring results for both devices individually and when used together, but results from clinical trials in patients have been mixed for each device when used individually:
- For compression-decompression CPR, a systematic review pooled the existing data for such CPR versus standard CPR in 4162 patients and found no difference in short-term mortality (relative risk 0·98, 95% CI 0·94–1·03) or survival to hospital discharge (0·99, 0·98–1·01). The 2010 CPR guidelines for the USA and Europe do not recommend the use of compression–decompression CPR alone.
- The most current systematic review for the impedance-threshold device showed a significantly improved early survival (relative risk 1·45, 1·16–1·80), and a short-term improved neurological outcome (2·35, 1·30–4·24); however, improved long- term survival did not reach conventional statistical significance (1·48, 0·91–2·41).
The Resuscitation Outcomes Consortium (ROC) PRIMED study3 showed no survival benefit in 8718 patients randomised to standard CPR with an active or sham impedance-threshold device (the Consortium includes the same investigators as the Lancet paper). This was published as an abstract in Circulation recently.
The editorialist has reservations regarding a change in clinical practice resulting from this new study, partly because the trial was stopped prematurely and enrolment of a larger cohort could have changed the findings, and partly because the open use of both devices might have unintentionally introduced bias into the study. Further validation is recommended.
1. Standard cardiopulmonary resuscitation versus active compression-decompression cardiopulmonary resuscitation with augmentation of negative intrathoracic pressure for out-of-hospital cardiac arrest: a randomised trial
Lancet 2011;377:301-11
2. Augmented CPR: rescue after the ResQ trial
Lancet. 2011 Jan 22;377:276-7
3. The Resuscitation Outcomes Consortium ROC) PRIMED Impedance Threshold Device (ITD) Cardiac Arrest Trial: A Prospective, Randomized, Double-Blind, Controlled Clinical Trial
Circulation 2010; 122: 2215–26 (abstr)
Pre-hospital iv and increased mortality
The US media seem to be making a big thing of a recent article published ahead of print which demonstrates an association between increased mortality from trauma and the insertion of an intravenous line with or without the administration of fluid.
This was a retrospective cohort study of over 770 000 patients from the National Trauma Data Bank. Approximately half (49.3%) received ‘prehospital IV’, which could mean fluids, or could just mean insertion of an intravenous cannula: ‘we could not definitively differentiate IV fluid administration versus IV catheter placement alone‘.
Unadjusted mortality was significantly higher in patients in the prehospital IV group, although the abstract inaccurately reports this to be ‘in patients receiving prehospital IV fluids‘ (4.8% vs. 4.5%, P < 0.001).
Multivariable logistic regression was used to examine the relationship between prehospital IV and mortality in the 311,071 patients with complete data. After adjustment, prehospital IV patients had significantly higher mortality than those without a prehospital IV. The odds ratio of death associated with prehospital IV placement was 1.11 (95% CI 1.06–1.17). When Dead-On-Arival patients were excluded from the group as a whole, the association persisted (OR 1.17, 95% CI 1.11–1.23).
On subgroup analyses, the association between IV placement and excess mortality was maintained in nearly all patient subsets; the effect was more exaggerated in penetrating trauma victims.
Media speculation as to the reason for this association abounds, like USA Today‘s ‘those who are given pre-hospital IV fluids are actually 11% more likely to die than those who aren’t, not only because of transport delays but also in part because of the increased risk for bleeding that can accompany a fluid-induced increase in blood pressure‘. However the study did not record any pre-hospital times and could not tell which patients received fluid, let alone what the effect of fluid on blood pressure was.
The authors are open about this and other limitations: ‘The NTDB did not report prehospital transport times or differentiate urban versus rural care. Thus, we could not examine whether excess mortality in patients treated with IVs was directly associated with delays in transport to definitive care. We were also not able to control for transport time within the multiple regression model or perform a stratified analysis by urban versus rural patients. Perhaps this analysis would have identified a subset of patients who may benefit from IV placement‘.
No doubt this will be added to the pile of mainly hypothesis-generating literature quoted by the scoop-and-run brigade whose black-and-white worldview includes paramedics who want to delay proper treatment and a homogeneous trauma population whose lives can only be saved by a trauma surgeon in a hospital. Those who have evolved colour vision find this an interesting, but hardly practice-changing study; caution regarding injudicious fluid administration has been the game plan for many civilian and military pre-hospital providers since early last decade, and it is clear that different patients with different injury patterns, different degrees of physiological derangement, and different distances from the right hospital will continue to have different clinical needs specific to their presentation, some of which are likely to be of benefit if provided in the field, through an intravenous line.
Prehospital Intravenous Fluid Administration is Associated With Higher Mortality in Trauma Patients: A National Trauma Data Bank Analysis
Ann Surg. 2010 Dec 20. [Epub ahead of print]