B lines be gone!

Vicki Noble’s Emergency Ultrasound team describe the resolution of Songraphic B lines on the lung ultrasound of a patient with end stage renal disease who presented with dyspnoea due to pumonary oedema which was treated with CPAP.
B-lines are hyperechoic vertical lines that originate at and slide with the pleura and extend radially to the edge of the screen without fading. Isolated B-lines may be seen in normal lungs, but diffuse B-lines in multiple zones indicate interstitial thickening, most commonly seen in congestive heart failure (CHF).

Image from cardiovascularultrasound.com

This case is interesting because it describes real-time resolution of B-lines during therapy in the ED demonstrating that in CHF, B-lines reflect acute rather than chronic changes within lung parenchyma.
Real-time resolution of sonographic B-lines in a patient with pulmonary edema on continuous positive airway pressure
Am J Emerg Med. 2010 May;28(4):541.e5-8

Hydrocarbon lakes on Titan

It’s a stretch – but Saturn’s largest moon Titan could support methane-based life forms. It is the only other place in the Solar System than Earth that is known to have liquid on its surface. Not liquid water though – which would freeze at Titan’s temperature of minus 283 degrees Celsius, but liquid hydrocarbons.

acetylene - food for alien bugs?

An interesting finding shows hydrogen molecules flowing down through Titan’s atmosphere and disappearing at the surface. Another is that maps of hydrocarbons on the surface show a lack of acetylene, (used on Earth as welding gas). One explanation is that methane-based life forms are eating it. Sensibly, Mark Allen, principal investigator with the NASA Astrobiology Institute Titan team, said: “Scientific conservatism suggests that a biological explanation should be the last choice after all non-biological explanations are addressed.”

Nevertheless, the thought of cool science like this keeps me warm at night. Nature keeps coming up with stuff far more exotic and wondrous than our own ancient magical myths ever imagined.

Saturn's Moon Titan

More information at Spaceinfo.com.au

Stroke thrombolysis benefit decays with time

Pooled results of several trials comparing recombinant tissue plasminogen activator with placebo in ischaemic stroke quantify the profile of benefit and harm for alteplase in broadly selected patients. Generally, alteplase appears to improve the outcome of one in three patients treated between 1 and 3 h from onset and of one in six patients treated in the 3–4·5 h window, but confers no net benefit beyond that time. Benefit may decrease exponentially (according to an accompanying editorial), so if you are a believer then get in there early.
Time to treatment with intravenous alteplase and outcome in stroke: an updated pooled analysis of ECASS, ATLANTIS, NINDS, and EPITHET trials
Lancet. 2010 May 15;375(9727):1695-703

Misoprostol for PPH

Misoprostol is a prostaglandin analogue with uterotonic activity. It was compared with placebo in its sublingual form in a randomised trial in 1422 women with postpartum haemorrhage and uterine atony. It was given with other uterotonic agents (mostly oxytocin 10IU im or slow iv). The primary outcome was blood loss of 500 mL or more within 60 min after randomisation, and this was similar in both groups.
Misoprostol as an adjunct to standard uterotonics for treatment of post-partum haemorrhage: a multicentre, double-blind randomised trial
Lancet. 2010 May 22;375(9728):1808-13

HFOV in preterms – no clear benefit

Pre-term infants lacking surfactant often require mechanical ventilation, but the consequent barotrauma and volutrauma may contribute to chronic lung disease, or bronchopulmonary dysplasia. Consequently high frequency oscillatory ventilation (HFOV) has been tried, but results from trials are mixed. A new systematic review of 3229 preterm newborns of less than 35 weeks’ gestation in 10 randomised trials fails to show a benefit of HFOV over conventional ventilation.

Elective high-frequency oscillatory versus conventional ventilation in preterm infants: a systematic review and meta-analysis of individual patients’ data
The Lancet, Volume 375, Issue 9731, Pages 2082 – 2091, 12 June 201o

Exsanguinating pelvis – occlude the aorta

Some patients with life-threatening arterial haemorrhage from a pelvic fracture may be peri-arrest prior to transfer to the angiography suite. French authors describe their use of a balloon catheter to occlude the infrarenal aorta to allow resuscitation to achieve sufficient stability for the transfer. As well as exsanguinating pelvic haemorrhage, intra-aortic balloon occlusion has already been described for the treatment of hemorrhagic shock in the case of ruptured abdominal aortic aneurysm, in abdominal trauma, in gastrointestinal bleeding, and in postpartum hemorrhage.

Features of note regarding the technique include:

  • it can be done blind (without radiological guidance)
  • it can be done prior to transfer to a centre with interventional radiology
  • it can be done in cardiac arrest (and has resulted in ROSC and subsequent survival)

The authors are at pains to point out that the intra-aortic balloon occlusion method described in the study ‘should be reserved to patients in critically uncontrollable hemorrhagic shock (CUHS) and is not a first-line treatment of pelvic fractures in hemorrhagic shock.’

Intra-Aortic Balloon Occlusion to Salvage Patients With Life-Threatening Hemorrhagic Shocks From Pelvic Fractures
J Trauma. 2010 Apr;68(4):942-8.

Tranexamic acid saves lives in trauma

A convincing, practice-changing trial is a rare thing in major trauma, but here comes a biggie:

The CRASH-2 trial recruited over 20 000 patients from 40 countries (sadly excluding the US because the trial investigators couldn’t afford the insurance – a sign that no large drug company was funding this trial of an inexpensive therapy).

The antifibrinolytic drug tranexamic acid was compared with placebo in adult trauma patients with, or thought to be at risk of, significant haemorrhage. Clinicians were blinded to the intervention and the primary outcome was death in hospital within 4 weeks of injury. Secondary outcomes were vascular occlusive events (myocardial infarction, stroke, pulmonary embolism, and deep vein thrombosis), surgical intervention (neurosurgery, thoracic, abdominal, and pelvic surgery), receipt of blood transfusion, and units of blood products transfused. Treatment groups were balanced with respect to all baseline patient characteristics.

All-cause mortality was significantly reduced with tranexamic acid and the risk of death due to bleeding was significantly reduced. Vascular occlusive events (fatal or non-fatal) did not differ significantly between the groups (and were fewer in the tranexamic acid group compared with the placebo group).

All cause mortality in the tranexamic acid group was (1463/10 060) = 14·5% and in the placebo group was (1613/10 067) = 16·0%. So absolute risk reduction is 1.5% and Number Needed to Treat = 67.

The same trials group is investigating the effect of tranexamic acid in post-partum haemorrhage, in a study known as the WOMAN Trial

Take Home Message: the early administration of tranexamic acid to trauma patients with, or at risk of, significant bleeding reduces the risk of death from haemorrhage with no apparent increase in fatal or non- fatal vascular occlusive events. All-cause mortality was significantly reduced with tranexamic acid.

Effects of tranexamic acid on death, vascular occlusive events, and blood transfusion in trauma patients with significant haemorrhage (CRASH-2): a randomised, placebo-controlled trial
The Lancet, Early Online Publication, 15 June 2010

Thoracic electrical bioimpedance in dyspnoea

Thoracic electrical bioimpedance (TEB) was used in ED patients presenting with dyspnoea to differentiate between cardiac and non-cardiac causes.
The fundamental principle behind TEB is based on Ohm’s law. If a constant electrical current is applied to the thorax, changes in impedance (ΔZ) to flow are equal to changes in voltage drop across the circuit. As a current will always seek the path of lowest resistivity, which in the human body is blood, ΔZ of the thorax will primarily reflect the dynamic changes of blood volume in the thoracic aorta. Changes in thoracic electrical impedance are continuously recorded and processed using a computer algorithm to calculate a number of cardiohaemodynamic parameters such as stroke volume, CO, CI, SVR and systemic vascular resistance index (SVRi).

A cardiac index cut-off of 3.2 l/m/m2 had a 86.7% sensitive (95% CI 59.5% to 98.0%) and 88.9% specific (95% CI 73.9% to 96.8%) for cardiac dyspnoea in the 52 patients studies, of which 15 had cardiac-related dyspnoea.

The study has several limitations including small numbers and using the gold standard of discharge diagnosis.

Thoracic electrical bioimpedance: a tool to determine cardiac versus non-cardiac causes of acute dyspnoea in the emergency department
Emerg Med J. 2010 May;27(5):359-63
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Traumatic Aortic Injury

Two recent papers expand our knowledge of blunt traumatic aortic injury.

UK crash data identified risk factors for low impact blunt traumatic aortic rupture, or ‘LIBTAR’ (crashes at relatively low speed): age >60, lateral impacts and being seated on the side that is struck are predictive of LIBTAR. This study should raise our index of suspicion of aortic injury in low-impact scenarios since low-impact collisions account for two thirds of fatal aortic injuries.

Low-impact scenarios may account for two-thirds of blunt traumatic aortic rupture
Emerg Med J. 2010 May;27(5):341-4

Data from the Victorian State Trauma Registry showed pre-hospital mortality from traumatic thoracic aortic transection was approximately 88.0%, whereas patients who survive to reach hospital have a much lower hospital mortality (33.3%, and once patients who arrived in extremis were removed hospital mortality was reduced to 5.9%). Repair was performed in 46 patients, with 22 receiving initial endovascular repair and 24 receiving initial open repair. Mortality rates following surgery were 9.1% and 16.7%, respectively.

The majority of patients arriving at hospital (57.1%) had an ISS of over 40 highlighting that these patients are unlikely to have only one serious injury and are likely to be more seriously injured than the normal trauma population. An ISS greater than 40 was a main predictor of mortality before repair.

Aortic transection: demographics, treatment and outcomes in Victoria, Australia
Emerg Med J. 2010 May;27(5):368-71