Flat IVC on CT associated with deterioration

BACKGROUND: : We aimed to investigate the value of the diameter of the inferior vena cava (IVC) on initial computed tomography (CT) to predict hemodynamic deterioration in patients with blunt torso trauma.

METHODS: : We reviewed the initial CT scans, taken after admission to emergency room (ER), of 114 patients with blunt torso trauma who were consecutively admitted during a 24-month period. We measured the maximal anteroposterior and transverse diameters of the IVC at the level of the renal vein. Flat vena cava (FVC) was defined as a maximal transverse to anteroposterior ratio of less than 4:1. According to the hemodynamic status, the patients were categorized into three groups. Patients with hemodynamic deterioration after the CT scans were defined as group D (n = 37). The other patients who remained hemodynamically stable after the CT scans were divided into two groups: patients who were hemodynamically stable on ER arrival were defined as group S (n = 60) and those who were in shock on ER arrival and responded to the fluid resuscitation were defined as group R (n = 17).

RESULTS: : The anteroposterior diameter of the IVC in group D was significantly smaller than those in groups R and S (7.6 mm ± 4.4 mm, 15.8 mm ± 5.5 mm, and 15.3 mm ± 4.2 mm, respectively; p < 0.05). Of the 93 patients without FVC, 16 (17%) were in group D, 14 (15%) required blood transfusion, and 8 (9%) required intervention. However, of the 21 patients with FVC, all patients were in group D, 20 (95%) required blood transfusion, and 17 (80%) required intervention. The patients with FVC had higher mortality (52%) than the other patients (2%).

CONCLUSION: : In cases of blunt torso trauma, patients with FVC on initial CT may exhibit hemodynamic deterioration, necessitating early blood transfusion and therapeutic intervention.

Predictive Value of a Flat Inferior Vena Cava on Initial Computed Tomography for Hemodynamic Deterioration in Patients With Blunt Torso Trauma
J Trauma. 2010 Dec;69(6):1398-402

H1N1 Update from UK Intensive Care

H1N1 Update 16 December 2010 sent from the UK Intensive Care Society

As many of you will already be aware, the predicted second wave of swine flu seems to becoming a reality. The HPA have received information that there has been a rise in the number of confirmed H1N1 cases and has restarted regular teleconferences to discuss the current situation and to disseminate the latest advice and information. The initial teleconference was held last Friday and the first question asked was how many cases have units seen. Although the total numbers were not high, the fact that there are confirmed cases throughout the UK gave support to the decision that hospitals should prepare for an increase in the numbers.

Subsequent updates have confirmed that the case numbers are rising and although not all patients admitted to ICUs with a suspected diagnosis of H1N1 have required mechanical ventilation or had H1N1 confirmed. As of Wednesday this week the numbers of H1N1 related ICU cases had risen to 140.  An additional concern is that the number of cases with probable H1N1 referred for ECMO is now 13 and this has resulted in a policy that there should be support for all the centers in the UK who can provide ECMO.

It is still too early to predict what the level escalation is going to be required, but there are real concerns that the combination of adverse weather conditions, the current financial restrictions in the NHS, and an H1N1 peak could place ICUs in a more seriously challenging situation than occurred in the previous outbreak.

For this reason, it is recommended that clinicians should once again have a low threshold for considering the possibility of H1N1 in patients who are referred to intensive care. Trusts should reconvene regular meetings to plan for any necessary expansion of critical care services. It is important that staff have up to date training in the use of personal protection equipment.  One of the most important points learned from the first outbreak was that early antiviral therapy can reduce the need for mechanical ventilation and it is recommended that any patients admitted to hospital with a history and symptoms suggestive of an influenza-like illness should be given antiviral therapy.

The following points were made in the HPA–led teleconference on 10 December:

  • be vigilant: have a low threshold for considering the diagnosis.
  • start antivirals whenever there is a suspicion of flu (oseltamivir 75or 150 mg bd po).
  • In patients with resistance or not tolerating NG medication, there is an IV preparation which is currently undergoing clinical trial. GSK produces it (zanamavir) and may provide it on patient-name compassionate grounds.
  • Use ARDSnet ventilation especially for those with normal lung compliance.
  • Consider HFO for those with poor compliance
  • Fluid restrict patients
  • Consider referral for ECMO early if conventional ventilation is failing. ECMO beds are occupied almost all occupied by ‘flu patients and elective surgery has been curtailed to accomodate them. Surge funding has been agreed for extra ECMO. In cases where conventional ventilation is failing and there are no other options, patients should be referred to Glenfield before seven days of MV.
  • HPA adviced has not changed with respect to infection control measures; these can be found here:http://www.dh.gov.uk/prod_consum_dh/groups/dh_digitalassets/@dh/@en/@ps/documents/digitalasset/dh_110899.pdf
  • The RCoA site still has an adult practice note from last year which will be updated
  • The HPA link to seasonal flu can be found here:http://www.hpa.org.uk/Topics/InfectiousDiseases/InfectionsAZ/SeasonalInfluenza/Guidelines/
  • There will be advice re pregnant women after discussion with the RCOG
  • In some cases, URT specimens may be negative in severe cases and LRT samples may be needed for the diagnosis.
  • Point of care testing may have inadequate  sensitivity for this strain of H1N1

The current rate is 21.5/100,000.

We aim to provide updates on the ICS website and copy of this document is available to download via http://www.ics.ac.uk/ under ‘Latest News – H1N1 Latest News’.
Update by the Executive Committee of the Intensive Care Society.

Sent from the email of:

Pauline Kemp

Head of Secretariat

Passive leg raising during CPR

Measuring end-tidal carbon dioxide (ET CO2 ) is a practical non-invasive method for detecting pulmonary blood flow, reflecting cardiac output and thereby the quality of CPR. It has also been shown to rise before clinically detectable return of spontaneous circulation (ROSC).

Passive leg raising (PLR) increases venous return and may therefore augment cardiac output and in a cardiac arrest this may be reflected by an elevation in ETCO2.

A Swedish observational study of 126 patients with out of hospital cardiac arrest due to a likely cardiac aetiology underwent tracheal intubation with standardised ventilation and chest compressions (either manually or using the LUCAS device, as part of larger study of mechanical chest compressions according to a cluster design). Patients were stratified to receive either PLR to 20 degrees or no PLR. ETCO2 was measured during CPR, either for 15min, or until the detection of ROSC.

Hang on I think that's overdoing it a bit

During PLR, an increase in ETCO2 was found in all 44 patients who received PLR within 15s (p=0.003), 45s (p = 0.002) and 75 s (p = 0.0001). Survival to hospital discharge was 7% among patients with PLR and 1% among those without PLR (p = 0.12). Among patients experiencing ROSC (60 of 126), there was a marked increase in ETCO2 1 min before the detection of a palpable pulse.

Passive leg raising during cardiopulmonary resuscitation in out-of-hospital cardiac arrest—Does it improve circulation and outcome?
Resuscitation. 2010 Dec;81(12):1615-20

UK Military Clinical Guidelines

In the United Kingdom, The Academic Department of Military Emergency Medicine at the Royal Centre for Defence Medicine produces Clinical Guidelines for Operations on behalf of Surgeon General under the direction of Defence Professor of Emergency Medicine.

These guidelines, last updated in May 2010, are available on line here:

**UPDATE JUNE 2011** I have received correspondence that this document is now out of date. The link is however still active and the document makes for interesting reading.

Brain chain

Therapeutic hypothermia (TH) has been associated with improved outcomes in term infants who present with moderate hypoxic-ischaemic encephalopathy (HIE). However, in the three major studies the time to initiate cooling was at approximately 4.5 postnatal hours. Many newborns are referred to specialist centres where cooling takes place from outlying hospitals (‘outborn’). It may be the case that earlier initiation of TH could improve outcomes, leading Takenouchi and colleagues to propose a ‘Chain of Brain Preservation’.

Given that most infants are outborn, a time sensitive education metaphor termed Chain of Brain Preservation may facilitate early recognition of high risk infants and thus earlier treatment.

Chain of Brain Preservation—A concept to facilitate early identification and initiation of hypothermia to infants at high risk for brain injury
Resuscitation. 2010 Dec;81(12):1637-41

The four-stage approach to teaching skills

Instructors and graduates of certain Life Support courses will be familiar with the ‘four stage’ approach to teaching procedural skills (demonstration, deconstruction, formulation, performance):

  1. Silent run through in which teacher performs without commentary;
  2. teacher then performs while commentating;
  3. teacher then performs with commentary from student(s);
  4. finally student performs and commentates.

Two randomised studies published this month showed no improvement in skills performance with this teaching method compared with simpler approaches. One involved needle cricothyroidotomy1 and another laryngeal mask insertion2.

An accompanying editorial3 acknowledges that this might put an end to this educational dogma, but one should consider that the procedures taught in these studies were simple to perform, and the results might not be extendable to more complex procedures.

The editorial points out there are some interesting data describing the neurophysiological basis of learning. Observing actions made by others activates the cortical circuits responsible for the planning and execution of those same actions; this visual-motor coupling happens through a neuronal matching network called the Mirror Neuron System (MNS). Listening to a verbal description of a skill can activate the same visual-motor circuit as those activated by the hand or the leg when completing the skill. Even during new motor pattern formation there is significant NMS activation, supporting the concept that the building of motor memories is based on the combination of observation and execution.

The ingredients of the complex mechanism of motor learning are observation, listening and immediate execution. The priority that should be given to each of the individual components of motor skills teaching is difficult to quantify and should be the subject of future research.

The editorialists conclude: The four-stage approach has been used for years with no evidence of better skill acquisition and retention compared with traditional methods. Medical educators need high-quality data to address the knowledge gaps for this topic and the two studies in this issue have set a precedent for future research. In our opinion, we should continue to use the four-stage approach to skill teaching while waiting for more evidence of a superior approach.

I differ slightly in my conclusion: if I have a limited time to teach a skill station (like airway management in the APLS course), I know I’m a little more justified in ditching this time consuming ritual in favour of more hands-on time for the paying delegates.

1. Emergency skill training—A randomized controlled study on the effectiveness of the 4-stage approach compared to traditional clinical teaching
Resuscitation. 2010 Dec;81(12):1692-7

2. A randomised trial comparing a 4-stage to 2-stage teaching technique for laryngeal mask insertion
Resuscitation. 2010 Dec;81(12):1687-91

3. The four-stage approach to teaching skills: The end of a dogma?
Resuscitation. 2010 Dec;81(12):1607-8

Neurologist Vilayanur Ramachandran explains the mirror neuron system in this video from TED.com:

Needle crike: low rate and allow exhalation

Two dedicated devices for transtracheal oxygen delivery through a cricothyroidotomy needle are available, the ENK Oxygen Flow Modulator (ENK) and the Manujet. Both maintain oxygenation, but the ENK is thought to achieve better ventilation (as previously shown in a pig model) because of a continuous flow that provides CO2 washout between insufflations. Very little is known concerning the lung pressures generated with these 2 devices, so a study using a simulated trachea and artificial lung model sought to determine oxygen flow, tidal volumes, and airway pressures at different occlusion rates and during both simulated partial and complete upper airway obstruction.

Manujet

Gas flow and tidal volume were 3 times greater with the Manujet than the ENK (approximately 37 vs 14 L/min and 700 vs 250 mL, respectively) and were not dependent on the respiratory rate. In the absence of ventilation, the ENK delivered a 0.6+/-0.1 L/min constant gas flow. In the totally occluded airway, lung pressures increased to 136 cm H2O after 3 insufflations with the Manujet, whereas the ENK, which has a pressure release vent, generated acceptable pressures at a low respiratory rate (4 breaths/min) (peak pressure at 27.7 +/-0.7 and end-expiratory pressure at 18.8+/- 3.8 cm H2O). When used at a respiratory rate of 12 breaths/min, the ENK generated higher pressures (peak pressure at 95.9 +/- 21.2 and end-expiratory pressure at 51.4+/- 21.4 cm H2O). In the partially occluded airway, lung pressures were significantly greater with the Manujet compared with the ENK, and pressures increased with the respiratory rate with both devices. Finally, the gas flow and tidal volume generated by the Manujet varied proportionally with the driving pressure.

The authors asset that this study confirms:

  • the absolute necessity of allowing gas exhalation between 2 insufflations and
  • maintaining low respiratory rates during transtracheal oxygenation.

In the case of total airway obstruction, the ENK may be less deleterious because it has a pressure release vent. Using a Manujet at lower driving pressures may decrease the risk of barotrauma and allow the safe use of higher respiratory rates

ENK

Oxygen delivery during transtracheal oxygenation: a comparison of two manual devices
Anesth Analg. 2010 Oct;111(4):922-4

Isoflurane in refractory status epilepticus

One infrequently used option for refractory status epilepticus is isoflurane anaesthesia. A report of two cases demonstrates progressive MRI changes suggestive of neurotoxicity, that improved after discontinuation of isoflurane. Impossible to prove cause and effect here, since the both patients had status for weeks and were on multiple anticonvulsant medications, for example lorazepam, fosphenytoin, levetiracetam, valproate, and subsequent infusions of midazolam, pentobarbital, and ketamine. Neither patient recovered beyond a minimally conscious state. This article serves as a reminder that:

  1. Persistent status epilepticus may be associated with a poor neurologic outcome
  2. Some cases are extremely refractory to treatment
  3. Isoflurane is one of many options to try when standard anticonvulsant regimens are failing


Prolonged High-Dose Isoflurane for Refractory Status Epilepticus: Is It Safe?
Anesth Analg. 2010 Dec;111(6):1520-4

Magnesium in asthma limits tachycardia

Dr WFS Sellers and colleagues describe several cases that demonstrate convincingly a protective effect of intravenous magnesium sulphate against the tachycardia produced by intravenous salbutamol in patients with asthma. This effect was observed both when magnesium was given before and when given after the salbutamol. It was seen in critically ill asthmatic patients and in a volunteer with well-controlled asthma.

Intravenous magnesium sulphate increases atrial contraction time and refractory times. It is used to treat atrial tachyarrhythmias and has a negative chronotropic and dromotropic effect.

Intravenous magnesium sulphate prevents intravenous salbutamol tachycardia in asthma
Br J Anaesth. 2010 Dec;105(6):869-70