Monthly Archives: April 2012

Helicopters and improved trauma survival

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Helicopters and improved trauma survival

April 18, 2012 by  
Filed under All Updates, EMS, Trauma

A large retrospective study has shown increased trauma survival associated with helicopter transport. The reason is unclear and may be multifactorial: faster speed, greater access to trauma centres, higher exposure of crews to trauma, different crew skill mix and so on are all possibilities.

An interview of less than five minutes with one of the authors describes the study:

Context Helicopter emergency medical services and their possible effect on outcomes for traumatically injured patients remain a subject of debate. Because helicopter services are a limited and expensive resource, a methodologically rigorous investigation of its effectiveness compared with ground emergency medical services is warranted.

Objective To assess the association between the use of helicopter vs ground services and survival among adults with serious traumatic injuries.

Design, Setting, and Participants Retrospective cohort study involving 223 475 patients older than 15 years, having an injury severity score higher than 15, and sustaining blunt or penetrating trauma that required transport to US level I or II trauma centers and whose data were recorded in the 2007-2009 versions of the American College of Surgeons National Trauma Data Bank.

Interventions Transport by helicopter or ground emergency services to level I or level II trauma centres.

Main Outcome Measures Survival to hospital discharge and discharge disposition.

Results A total of 61 909 patients were transported by helicopter and 161 566 patients were transported by ground. Overall, 7813 patients (12.6%) transported by helicopter died compared with 17 775 patients (11%) transported by ground services. Before propensity score matching, patients transported by helicopter to level I and level II trauma centers had higher Injury Severity Scores. In the propensity score–matched multivariable regression model, for patients transported to level I trauma centers, helicopter transport was associated with an improved odds of survival compared with ground transport (odds ratio [OR], 1.16; 95% CI, 1.14-1.17; P < .001; absolute risk reduction [ARR], 1.5%). For patients transported to level II trauma centers, helicopter transport was associated with an improved odds of survival (OR, 1.15; 95% CI, 1.13-1.17; P < .001; ARR, 1.4%). A greater proportion (18.2%) of those transported to level I trauma centers by helicopter were discharged to rehabilitation compared with 12.7% transported by ground services (P < .001), and 9.3% transported by helicopter were discharged to intermediate facilities compared with 6.5% by ground services (P < .001). Fewer patients transported by helicopter left level II trauma centers against medical advice (0.5% vs 1.0%, P < .001).

Conclusion Among patients with major trauma admitted to level I or level II trauma centers, transport by helicopter compared with ground services was associated with improved survival to hospital discharge after controlling for multiple known confounders.


Association Between Helicopter vs Ground Emergency Medical Services and Survival for Adults With Major Trauma
JAMA, April 18, 2012—Vol 307, No. 15 1602-10

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Non-invasive BP in shock

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Non-invasive BP in shock

April 27, 2012 by  
Filed under All Updates, ICU, Resus

In the management of the shocked patient, we sometimes get a little fixated on the need for an arterial line. This is in part due to previous studies suggesting non-invasive blood pressure (NIBP) measurements were inaccurate in the critically ill. This appears no longer to be the case with modern oscillometric devices and carefully chosen cuff sizes. This recent study showed mean arterial pressure (MAP) measured non-invasively from the arm closely correlated with invasive measurements. NIBP was effective at identifying hypotension and recording the response to therapy. Although patients with severe occlusive arterial disease were excluded, the study did include a number of shocked patients on vasoactive therapies.

Systolic and diastolic pressures were not accurate. This should not be surprising since, as the authors explain:

“oscillometric devices directly measure the MAP and only extrapolate systolic arterial pressure and diastolic arterial pressure, using proprietary algorithms”

Thia study suggests that NIBP measurement of MAP from the arm is accurate but, if contraindicated, the ankle (or even the thigh in older sedated patients) may be a suitable alternative site permitting a reliable detection of hypotensive and therapy-responding patients.

OBJECTIVE: In the critically ill, blood pressure measurements mostly rely on automated oscillometric devices pending the intra-arterial catheter insertion or after its removal. If the arms are inaccessible, the cuff is placed at the ankle or the thigh, but this common practice has never been assessed. We evaluated the reliability of noninvasive blood pressure readings at these anatomic sites.

DESIGN: Prospective observational study.

SETTING: Medical-surgical intensive care unit.

PATIENTS: Patients carrying an arterial line with no severe occlusive arterial disease.

INTERVENTION: Each patient underwent a set of three pairs of noninvasive and intra-arterial measurements at each site (arm, ankle, thigh [if Ramsay sedation scale >4]) and, in case of circulatory failure, a second set of measurements after a cardiovascular intervention (volume expansion, change in catecholamine dosage).

MEASUREMENTS AND MAIN RESULTS: In 150 patients, whatever the cuff site, the agreement between invasive and noninvasive readings was markedly higher for mean arterial pressure than for systolic or diastolic pressure. For mean arterial pressure measurement, arm noninvasive blood pressure was reliable (mean bias of 3.4 ± 5.0 mm Hg, lower/upper limit of agreement of -6.3/13.1 mm Hg) contrary to ankle or thigh noninvasive blood pressure (mean bias of 3.1 ± 7.7 mm Hg and 5.7 ± 6.8 mm Hg and lower/upper limits of agreement of -12.1/18.3 mm Hg and -7.7/19.2 mm Hg, respectively). During acute circulatory failure (n = 83), arm noninvasive blood pressure but also ankle and thigh noninvasive blood pressure allowed a reliable detection of 1) invasive mean arterial pressure 10%) increase in invasive mean arterial pressure after a cardiovascular intervention (area under the receiver operating characteristic curve of 0.99 [0.92-1], 0.90 [0.80-0.97], and 0.96 [0.87-0.99], respectively).

CONCLUSION: In our population, arm noninvasive mean arterial pressure readings were accurate. Either the ankle or the thigh may be reliable alternatives, only to detect hypotensive and therapy-responding patients.

Noninvasive monitoring of blood pressure in the critically ill: Reliability according to the cuff site (arm, thigh, or ankle)
Crit Care Med. 2012 Apr;40(4):1207-13

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In CPR depth is good, but how deep to compress?

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In CPR depth is good, but how deep to compress?

April 26, 2012 by  
Filed under Acute Med, All Updates, EMS, ICU, Resus

Some defibrillators have accelerometers capable of measuring chest compression depth during CPR. This allowed a study correlating compression depth with survival in out of hospital cardiac arrest.
More than half of patients received less than the 2005 recommended chest compression depth of 38–51 mm and >90% received less than the 2010 recommended depth of >50 mm. There was an inverse relationship between rate and depth, ie. rescuers had a tendency to ‘push hard, push slow’ or ‘push soft, push fast’.

The authors state:
We found an association between adequate compression depth and good outcomes but could not demonstrate that the 2010 recommendations are better than those from 2005. Although we believe that compression depth is an important component of CPR and should be measured routinely during cardiac arrest resuscitation, we believe that the optimal depth is currently unknown.

BACKGROUND: The 2010 international guidelines for cardiopulmonary resuscitation recently recommended an increase in the minimum compression depth from 38 to 50 mm, although there are limited human data to support this. We sought to study patterns of cardiopulmonary resuscitation compression depth and their associations with patient outcomes in out-of-hospital cardiac arrest cases treated by the 2005 guideline standards.

DESIGN: Prospective cohort.

SETTING: Seven U.S. and Canadian urban regions.

PATIENTS: We studied emergency medical services treated out-of-hospital cardiac arrest patients from the Resuscitation Outcomes Consortium Epistry-Cardiac Arrest for whom electronic cardiopulmonary resuscitation compression depth data were available, from May 2006 to June 2009.

MEASUREMENTS: We calculated anterior chest wall depression in millimeters and the period of active cardiopulmonary resuscitation (chest compression fraction) for each minute of cardiopulmonary resuscitation. We controlled for covariates including compression rate and calculated adjusted odds ratios for any return of spontaneous circulation, 1-day survival, and hospital discharge.

MAIN RESULTS: We included 1029 adult patients from seven U.S. and Canadian cities with the following characteristics: Mean age 68 yrs; male 62%; bystander witnessed 40%; bystander cardiopulmonary resuscitation 37%; initial rhythms: Ventricular fibrillation/ventricular tachycardia 24%, pulseless electrical activity 16%, asystole 48%, other nonshockable 12%; outcomes: Return of spontaneous circulation 26%, 1-day survival 18%, discharge 5%. For all patients, median compression rate was 106 per minute, median compression fraction 0.65, and median compression depth 37.3 mm with 52.8% of cases having depth
CONCLUSIONS: We found suboptimal compression depth in half of patients by 2005 guideline standards and almost all by 2010 standards as well as an inverse association between compression depth and rate. We found a strong association between survival outcomes and increased compression depth but no clear evidence to support or refute the 2010 recommendations of >50 mm. Although compression depth is an important component of cardiopulmonary resuscitation and should be measured routinely, the most effective depth is currently unknown.

What is the role of chest compression depth during out-of-hospital cardiac arrest resuscitation?
Crit Care Med. 2012 Apr;40(4):1192-8

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You’re Doing It Wrong: New Study on BP Measurement

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wrongbp A new study1 published in the Journal of Clinical Hypertension has reached the conclusion that when it comes to proper blood pressure (BP) measurement technique, most clinicians just aren’t very good at it. According to the authors, Minor et al, the purpose of the study was to “assess BP measurement accuracy and the level of adherence to recommended techniques throughout a large academic health science center.” As it turns out, the results were poor on both fronts and their statistical analysis indicates that technique does indeed impact accuracy.

“…not one single patient had their arm circumference measured.”Clinic site personnel were observed measuring patient BP so that setting, technique and BP results were noted. Then a trained observer repeated the BP measurement, being sure to follow the American Heart Association (AHA) guidelines. A significant difference was apparent between measurements taken by site personnel and the trained observer with site personnel reporting an average increased systolic BP of nearly 6 mmHg and a decreased diastolic BP of -3 mmHg. While the differences observed are concerning, the degree to which proper technique was ignored is just as alarming.

Data collected for assessing technique included patient rest time, patient activity during BP measurement, use of bare vs covered arm, arm positioning and patient positioning. Cuff deflation rate, mentioned in a previous blog post as extremely important to manual BP measurement, was not considered since most of the BP measurements were taken with automated devices that control deflation. The table below details some of the observation data collected on technique.

 

Observations    Patients       Percent (%)   
Measured arm circumference    0 0%
Clothing/Sleeve interference 30 25%
Out of position/posture 18 15%
Conversation w/patient 48 40%
Bare Arm (no) 49 41%
Arm/cuff at heart level (no) 89 75%
Feet flat (no) 77 65%
Clinic rest time (no) 117 98%

 

After reviewing the table above, two statistics jumped out at us. First, was the fact that 98% of the patients were not given proper time to rest before a BP was taken. Second, was that not one single patient had their arm circumference measured. Now, we know from previous studies on BP technique that one of the most common issues affecting BP accuracy is using the incorrect cuff size. But when not a single member of the clinical staff bothers to measure a patient’s arm, this problem may be much worse than we realized. As the authors concluded, these findings probably reflect common problems throughout healthcare and highlight the need for increased vigilance and training to ensure accurate assessment of BP.

Inaccurate BP measurement can have significant effects, particularly for patients that are close to diagnostic threshold levels. Taking the time to make sure that we are doing it right helps to avoid unnecessary costs, inappropriate treatment and missed diagnoses.

1. Minor DS, Butler KR, Artman KL, et al. Evaluation of Blood Pressure Measurement and Agreement in an Academic Health Sciences Center. J Clin Hypertens. 2012;14:222-227.

 

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