i-STAT® analysis of intraosseous aspirate

March 6, 2014 by  
Filed under All Updates, EMS, ICU, Kids, Resus

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In the absence of vascular access we may resort to sending intraosseous aspirates for analysis, but in some laboratories there is concern that the samples can block autoanalysers.

A study on haematology/oncology patients undergoing diagnostic bone marrow aspiration showed clinically acceptable agreement between venous and intraosseous measurements for pH, base excess, sodium, ionised calcium and glucose using an an i-STAT® point-of-care analyser.

Key points are:

  • The first 1-2 ml should be discarded (as in this study)
  • Lactate hasn’t been assessed
  • These patients weren’t critically ill

Analysis of bloodgas, electrolytes and glucose from intraosseous samples using an i-STAT® point-of-care analyser
Resuscitation. 2014 Mar;85(3):359-63


BACKGROUND: Intraosseous access is used in emergency medicine as an alternative when intravenous access is difficult to obtain. Intraosseous samples can be used for laboratory testing to guide treatment. Many laboratories are reluctant to analyse intraosseous samples, as they frequently block conventional laboratory equipment. We aimed to evaluate the feasibility and accuracy of analysis of intraosseous samples using an i-STAT(®) point-of-care analyser.

METHODS: Intravenous and intraosseous samples of twenty children presenting for scheduled diagnostic bone marrow aspiration were analysed using an i-STAT(®) point-of-care analyser. Sample types were compared using Bland Altman plots and by calculating intraclass correlation coefficients and coefficients of variance.

RESULTS: The handheld i-STAT(®)point-of-care analyser proved suitable for analysing intraosseous samples without technical difficulties. Differences between venous and intraosseous samples were clinically acceptable for pH, base excess, sodium, ionised calcium and glucose in these haemodynamically stable patients. The intraclass correlation coefficient was excellent (>0.8) for comparison of intraosseous and intravenous base excess, and moderate (around 0.6) for bicarbonate, sodium and glucose. The coefficient of variance of intraosseous samples was smaller than that of venous samples for most variables.

CONCLUSION: Analysis of intraosseous samples with a bedside, single-use cartridge-based analyser is feasible and avoids the problem of bone marrow contents damaging conventional laboratory equipment. In an emergency situation point-of-care analysis of intraosseous aspirates may be a useful guide to treatment.

Awake intubation

May 14, 2013 by  
Filed under All Updates, EMS, ICU, Resus

I had some fun today getting intubated.

We used the Ambu aScope 2 and the Greater Sydney Area HEMS equipment and approach to airway management. I didn’t receive an antisialogogue or any analgesia or sedation.

The big learning point for me was how hard it was to anaesthetise the posterior part of my nasal cavity and nasopharynx. I thought the worst part would be any stimulation of my vocal cords or trachea with lidocaine or instrumentation, but this really was fine. Nebulised 2% lidocaine (the strongest concentration we have), atomised lidocaine (using a mucosal atomiser), and co-phenylcaine spray weren’t sufficient. I can see why people use pastes or gel to maintain mucosal contact while the lidocaine takes effect, but we don’t have those (yet). The best solution came from hooking up oxygen tubing to an iv cannula via a three way tap. Oxygen was run through at 2 l/min and lidocaine injected via the the three way tap. This enabled an atomised spray to be directed right onto the area concerned, and made the insertion of the nasotracheal tube more tolerable – although still unpleasant.

crazed-nutter-sm

The fact I could be intubated awake with reasonable topicalisation suggests most patients should tolerate it perhaps after even an analgesic dose of ketamine, eg. 30-40 mg in an adult. I suspect full dissocation would not be required, which is good for cooperation (“stick your tongue out sir”). I appreciate there are better agents, such as remifentanil or dexmedetomidine, but my area of interest is the retrieval setting – where I have neither the luxury of using these agents nor that of calling for anaesthetic back up.

Thanks to HEMS physicians Emily Stimson, Nirosha De Zoysa, Felicity Day, Chloe Tetlow, and Fergal McCourt for making it fun and safe.

Here’s the video:

Twitter has been helpful in gathering some advice, particularly from @DocJohnHinds:

Point of care analysis of intraosseous samples

January 2, 2013 by  
Filed under All Updates, EMS, Resus

Some good news for remote, rural, prehospital, and retrieval medicine clinicians who rely on point of care testing with the i-STAT® device. An animal study confirmed the reliability of testing aspirates from intraosseous samples taken from the tibia(1).

This is also good news for hospital practitioners when it comes to the acquisition of blood gas results, since there are concerns over the potential damage to blood gas analysers by bone marrow contents in the samples.

The researchers tested blood gases, acid–base status, lactate, haemoglobin, and electrolytes, and compared these with results from an arterial sample.

There was no malfunction of the equipment. Most of the acid–base parameters showed discrepancies between arterial and osseous samples: the average pH and base excess were consistently lower whilst pCO2 and lactate were higher in the intraosseous samples compared to the arterial. However the overall small degree and predictable direction of discrepancy in these values should preserve the clinical usefulness of intraosseous gases if these findings can be replicated in human subjects. pO2 was obviously very different between osseous and arterial samples.

They noted that aspiration of intraosseous samples was generally straightforward, especially immediately after placement of the cannulae, but on a few occasions more forceful aspiration was needed. They point out that this could possibly cause cellular lysis and affect the potassium analysis.

The authors consider the issue of how much aspirate should be discarded before taking a sample after intraosseous cannula insertion, and refer to a prior study which suggested that 2mL is adequate.

Summary
  • Intraosseous aspirate can be tested on an i-STAT® point-of-care analyser
  • Haemoglobin and electrolytes show good correlation with arterial samples
  • Acid-base, pCO2, and lactate differ slightly from arterial results but in a predictable direction and results are still likely to be clinically useful in an emergency
  • It may be worth discarding the first 2 ml of aspirate
  • These results require validation in human subjects

Analysis of intraosseous samples using point of care technology–an experimental study in the anaesthetised pig
Resuscitation. 2012 Nov;83(11):1381-5


BACKGROUND: Intraosseous access is an essential method in emergency medicine when other forms of vascular access are unavailable and there is an urgent need for fluid or drug therapy. A number of publications have discussed the suitability of using intraosseous access for laboratory testing. We aimed to further evaluate this issue and to study the accuracy and precision of intraosseous measurements.

METHODS: Five healthy, anaesthetised pigs were instrumented with bilateral tibial intraosseous cannulae and an arterial catheter. Samples were collected hourly for 6h and analysed for blood gases, acid base status, haemoglobin and electrolytes using an I-Stat point of care analyser.

RESULTS: There was no clinically relevant difference between results from left and right intraosseous sites. The variability of the intraosseous sample values, measured as the coefficient of variance (CV), was maximally 11%, and smaller than for the arterial sample values for all variables except SO2. For most variables, there seems to be some degree of systematic difference between intraosseous and arterial results. However, the direction of this difference seems to be predictable.

CONCLUSION: Based on our findings in this animal model, cartridge based point of care instruments appear suitable for the analysis of intraosseous samples. The agreement between intraosseous and arterial analysis seems to be good enough for the method to be clinically useful. The precision, quantified in terms of CV, is at least as good for intraosseous as for arterial analysis. There is no clinically important difference between samples from left and right tibia, indicating a good reproducibility.

Speeding things up through equipment design

December 31, 2012 by  
Filed under All Updates, ICU, Resus, Trauma

Ever been at a cardiac arrest resuscitation where someone’s opening and closing drawers at great speed but failing to retrieve the drugs or equipment you’ve asked for urgently?

What if your resus trolley were designed by team of clinicians, engineers, and designers? Such a project was achieved through a collaboration between Imperial College London and the Helen Hamlyn Centre for Design, and the award-winning result was called the ‘Resus:Station’.

The trolley separates into three trolleys for airway, drugs and defibrillation, and circulation. The contents are visible from the outside.

Image from Pubmed Free Full Text Article

As well as improving access to equipment, the trolley can log the team’s actions during each resuscitation attempt. It can also provide an instant display of its readiness for use by recording the removal and replacement of each item.

In a randomised comparison with a standard resus trolley, a number of measures of efficiency and team performance were significantly better using the Resus:Station during simulated cardiac arrest resuscitations.

It appears to be specifically designed for cardiac arrest situations rather than ‘resus’ in its wider context. The most recent article (cited below) reports that a newer prototype is being developed prior to the manufacture of the final product.

For an in depth discussion of how resus room layout can optimise efficiency, check out Minh Le Cong’s PHARM blog and podcast with James French and Scott Weingart on Clinical Logistics

The “Resus:Station”: the use of clinical simulations in a randomised crossover study to evaluate a novel resuscitation trolley.
Resuscitation. 2012 Nov;83(11):1374-80 Free full text

BACKGROUND AND AIM: Inadequately designed equipment has been implicated in poor efficiency and critical incidents associated with resuscitation. A novel resuscitation trolley (Resus:Station) was designed and evaluated for impact on team efficiency, user opinion, and teamwork, compared with the standard trolley, in simulated cardiac arrest scenarios.

METHODS: Fifteen experienced cardiac arrest teams were recruited (45 participants). Teams performed recorded resuscitation simulations using new and conventional trolleys, with order of use randomised. After each simulation, efficiency (“time to drugs”, un-locatable equipment, unnecessary drawer opening) and team performance (OSCAR) were assessed from the video recordings and participants were asked to complete questionnaires scoring various aspects of the trolley on a Likert scale.

RESULTS: Time to locate the drugs was significantly faster (p=0.001) when using the Resus:Station (mean 5.19s (SD 3.34)) than when using the standard trolley (26.81s (SD16.05)). There were no reports of missing equipment when using the Resus:Station. However, during four of the fifteen study sessions using the standard trolley participants were unable to find equipment, with an average of 6.75 unnecessary drawer openings per simulation. User feedback results clearly indicated a highly significant preference for the newly designed Resus:Station for all aspects. Teams performed equally well for all dimensions of team performance using both trolleys, despite it being their first exposure to the Resus:Station.

CONCLUSION: We conclude that in this simulated environment, the new design of trolley is safe to use, and has the potential to improve efficiency at a resuscitation attempt.

Which pelvic compression device is best?

December 16, 2012 by  
Filed under All Updates, EMS, ICU, Kids, Resus, Trauma

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Two popular pelvic compression devices are the SAM Pelvic Sling II and the T-POD®.

In a direct comparison 50 health care volunteers secured both devices correctly 100% of the time.

The SAM Pelvic Sling II was quicker to apply, but participants preferred the T-POD®.

The authors conclude that very little separates the devices.

Pelvic circumferential compression devices (PCCDs): a best evidence equipment review
Eur J Trauma Emerg Surg (2012) 38:439–442


Purpose Traumatic disruption of the pelvis can lead to significant morbidity and mortality. ATLS® guidance advocates temporary stabilisation or ‘closure’ of the disrupted pelvis with a compression device or sheet. We undertook a best evidence equipment review to assess the ease and efficacy of the application of two leading commercially available devices, the T-POD® and the SAM Pelvic Sling™ II.

Methods Fifty health care professionals and medical students participated in pelvic circumferential compression device (PCCD) education and assessment. Participants received a 10-min lecture on the epidemiology and aetiology of pelvic fractures and the principles of circumferential compression, followed by a practical demonstration. Three volunteers acted as trauma victims. Assessment included the time taken to secure the devices and whether this was achieved correctly. All participants completed a post-assessment survey.

Results Both devices were applied correctly 100% of the time. The average time taken to secure the SAM Pelvic Sling™ II was 18 s and for the T-POD®, it was 31 s (p ≤ 0.0001). Forty-four participants (88%) agreed or strongly agreed that the SAM Pelvic Sling™ II was easy to use compared to 84% (n = 42) for the T-POD®. Thirty-nine participants (78%) reported that they preferred and, given the choice in the future, would select the T-POD® over the SAM Pelvic Sling™ II (n = 11, 22%).

Conclusions The results of this study indicate that both PCCDs are easy and acceptable to use and, once learned, can be applied easily and rapidly. Participants applied both devices correctly 100% of the time, with successful application taking, on average, less than 60 s.

What happened to HIFU?

December 13, 2012 by  
Filed under All Updates, EMS, ICU, Resus, Trauma, Ultrasound

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High intensity focused ultrasound (HIFU) was hailed as the ‘surgery of the future’ a few years ago(1). As it’s now the future, where is it?

HIFU uses ultrasound to increase the heat within tissues at a specific area, causing local necrosis and cautery without injuring surrounding tissues. It is used to treat some cancers, but has shown promise in haemorrhage control. In animal studies it reduced or stopped bleeding in liver(2), spleen(3), and vascular injuries(4).

It has been proposed to offer a promising method for hemorrhage control in both civilivan and miltary trauma(5). Automated systems have been developed and tested that identify bleeding using Doppler ultrasound techniques that then allow targeting of the HIFU beam to the bleeding tissue(6). The United States Army has identified the need for a such systems and has designed a remotely operated robotic haemostatic system to save lives of soldiers. This was presented in 2006(7).

I would love to know where we are with this technology, and why nothing seems to have appeared about it in the literature for the last few years. If you have any information, please fill us in via the comments box.

1. High intensity focused ultrasound: surgery of the future?
Br J Radiol. 2003 Sep;76(909):590-9 Full text

2. Liver hemostasis using high-intensity focused ultrasound
Ultrasound Med Biol. 1997;23(9):1413-20

3. Control of splenic bleeding by using high intensity ultrasound
J Trauma. 1999 Sep;47(3):521-5

4. Hemostasis of punctured blood vessels using high-intensity focused ultrasound
Ultrasound Med Biol. 1998 Jul;24(6):903-10

5. Hemorrhage control using high intensity focused ultrasound
Int J Hyperthermia. 2007 Mar;23(2):203-11

6. Focused ultrasound: concept for automated transcutaneous control of hemorrhage in austere settings.
Aviat Space Environ Med. 2009 Apr;80(4):391-4

7. Remotely Operated Robotic High Intensity Focused Ultrasound (HIFU) Manipulator System for Critical Systems for Trauma and Transport (CSTAT)
Presented at the IEEE Ultrasonics Symposium, October 3-6, 2006, Vancouver, Canada – Full Text Here

Needle decompression: it’s still not going to work

October 28, 2012 by  
Filed under All Updates, EMS, ICU, Resus, Trauma

A pet topic that keeps coming up here is management of tension pneumothorax. Plenty of studies demonstrate that traditionally taught needle thoracostomy may fail, and open, or ‘finger’ thoracostomy is recommended for the emergency management of tension pneumothorax in a patient who is being ventilated with positive pressure (including those patients in cardiac arrest).

A recent CT scan-based study of adult trauma patients makes the case that needle decompression with a standard iv cannula would be expected to fail in 42.5% of cases at the second intercostal space (ICS) compared with 16.7% at the fifth ICS at the anterior axillary line (AAL).

The authors add an important point: “As BMI increases, there is a stepwise increase in chest wall thickness, further compounding the difficulty of needle placement in all but the lowest BMI quartile for the second ICS.”

An accompanying editorial cautions that the proximity of the heart may confer a safety issue if a needle is inserted blindly into the left 5th ICS at the AAL.


Objective To compare the distance to be traversed during needle thoracostomy decompression performed at the second intercostal space (ICS) in the midclavicular line (MCL) with the fifth ICS in the anterior axillary line (AAL).

Design Patients were separated into body mass index (BMI) quartiles, with BMI calculated as weight in kilograms divided by height in meters squared. From each BMI quartile, 30 patients were randomly chosen for inclusion in the study on the basis of a priori power analysis (n = 120). Chest wall thickness on computed tomography at the second ICS in the MCL was compared with the fifth ICS in the AAL on both the right and left sides through all BMI quartiles.

Setting Level I trauma center.

Patients Injured patients aged 16 years or older evaluated from January 1, 2009, to January 1, 2010, undergoing computed tomography of the chest.

Results A total of 680 patients met the study inclusion criteria (81.5% were male and mean age was 41 years [range, 16-97 years]). Of the injuries sustained, 13.2% were penetrating, mean (SD) Injury Severity Score was 15.5 (10.3), and mean BMI was 27.9 (5.9) (range, 15.4-60.7). The mean difference in chest wall thickness between the second ICS at the MCL and the fifth ICS at the AAL was 12.9 mm (95% CI, 11.0-14.8; P < .001) on the right and 13.4 mm (95% CI, 11.4-15.3; P < .001) on the left. There was a stepwise increase in chest wall thickness across all BMI quartiles at each location of measurement. There was a significant difference in chest wall thickness between the second ICS at the MCL and the fifth ICS at the AAL in all quartiles on both the right and the left. The percentage of patients with chest wall thickness greater than the standard 5-cm decompression needle was 42.5% at the second ICS in the MCL and only 16.7% at the fifth ICS in the AAL.

Conclusions In this computed tomography–based analysis of chest wall thickness, needle thoracostomy decompression would be expected to fail in 42.5% of cases at the second ICS in the MCL compared with 16.7% at the fifth ICS in the AAL. The chest wall thickness at the fifth ICS AAL was 1.3 cm thinner on average and may be a preferred location for needle thoracostomy decompression.

Radiologic evaluation of alternative sites for needle decompression of tension pneumothorax
Arch Surg. 2012 Sep 1;147(9):813-8

Finally I understand ultrasound physics

October 20, 2012 by  
Filed under All Updates, ICU, Resus, Ultrasound

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Ever waste time trying to shake some ultrasound gel out the bottle, like a resistant blob of ketchup?
Sydney emergency medicine registrar Dr Steve Skinner demonstrates how to solve this. With physics.

This really does work, and has saved me a lot of time already. I now do a somewhat less ballistic version than the one demonstrated, so that patients don’t think I’m mad.



This video is for entertainment purposes only. We accept no responsibility for injuries sustained as a result of unaccustomed shoulder activity or inadvertently launched plastic projectiles.

Size matters when you’re sick

August 2, 2012 by  
Filed under All Updates, EMS, ICU, Resus

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A nice example of a difference between elective anaesthesia and critical care practice when it comes to airway management is the selection of appropriate tracheal tube size when intubating, which is highlighted in a recent Anaesthesia article.

In recent years progressively smaller tubes have been used in anaesthesia in pursuit of decreased tracheal injury, sore throat, and hoarseness and increased ease of placement.

Patients likely to remain intubated for some time due to critical illness, however, may benefit from larger diameter tubes for the following reasons:

  • Accumulation of biofilm debris, which increases with duration of intubation – this can significantly decrease the luminal internal diameter, but is less likely to be significant with larger tubes.
  • Work of breathing during weaning: spontaneous breathing trials prior to extubation require patients to breathe through tracheal tubes. Volunteer studies have demonstrated that work of breathing increases as tube diameter decreases.
  • Bronchoscopes and suction catheters: the standard adult ICU fibreoptic bronchoscope has a diameter of 5.7 mm with a 2-mm suction channel to enable adequate suction, which limits the tracheal tube to those larger than 7.5–8.0 mm, and even with an 8.0-mm tube, the bronchoscope occupies more than 50% of the tube diameter, which can lead to ventilation issues during bronchoscopy.

The authors conclude by recommending:


‘If admission to ICU is contemplated then the time-honoured ‘8.0 for females, 9.0 for males’ is a reasonable rule of thumb, unless circumstances dictate otherwise, e.g. in difficult airways or particularly small patients.’

Size matters: choosing the right tracheal tube
Anaesthesia. 2012 Aug;67(8):815-9

Simple emergency haemorrhage control

March 13, 2012 by  
Filed under All Updates, EMS, Resus, Trauma

I had the honour of attending trauma rounds with leading South African trauma surgeons today at Groote Schuur Hospital in Cape Town. This was the first day of an intense week-long trauma education tour that I have organised for myself and three of my Sydney HEMS colleagues.

A technique for haemorrhage control in penetrating trauma is to place a Foley catheter (FC) in the wound and inflate the balloon to try to achieve compression of bleeding vascular structures. This has been life-saving in many cases and buys time to get the patient to a trauma or vascular surgeon or in some cases an interventional radiologist.

Catheter is knotted (black arrow) to occlude lumen. The wound is sutured around the catheter (white arrow).

First described by Gilroy and colleagues from Baragwanath Hospital in Johannesburg1, another, larger case series was subsequently reported by Cape Town’s Navsaria2, the Professor who conducted today’s trauma round I attended. In his paper he describes:


An 18- or 20-G FC was introduced into the bleeding neck wound. An attempt was made to follow the wound tract. The balloon was inflated with 5 ml of water or until resistance was felt. The FC was either clamped or knotted on itself to prevent bleeding through the lumen. The neck wound was sutured in two layers around the catheter. Continued bleeding around the catheter was an indication to proceed to surgery.

There were no deaths attributable to the use of FC balloon tamponade.

Prof. Navsaria describes the following algorithm for the subsequent investigation and management of these patients:

 I’ve been teaching this technique as an option in penetrating trauma for a few years but have never actually done it for real. Nice to finally see examples of its successful implementation by people who do this all the time. I’ve seen four patients with Foleys sticking out of their necks in the first 24 hours of being here.

1. Control of life-threatening haemorrhage from the neck: a new indication for balloon tamponade.
Injury. 1992;23(8):557-9


We report the use of a Foley catheter, placed through the wound, to provide balloon tamponade of major bleeding from the neck and supraclavicular fossae. In 10 consecutive explorations for exsanguinating injury in these regions balloon tamponade was used eight times, and was judged to be fully effective in four patients, partly effective in one, and ineffective in three patients.

2. Foley catheter balloon tamponade for life-threatening hemorrhage in penetrating neck trauma
World J Surg. 2006 Jul;30(7):1265-8


BACKGROUND: Foley catheter (FC) balloon tamponade is a well-recognized technique employed to arrest hemorrhage from penetrating wounds. The aim of this study was to review our experience with this technique in penetrating neck wounds and to propose a management algorithm for patients with successful FC tamponade.

METHODS: A retrospective chart review (July 2004-June 2005 inclusive) was performed of patients identified from a prospectively collected penetrating neck injury computer database in whom FC balloon tamponade was used. The units’ policy for penetrating neck injuries is one of selective nonoperative management. All patients with successful FC tamponade underwent angiography. A venous injury was diagnosed if angiography was normal. Ancillary tests were performed as indicated. Removal of the FC was performed in the OR.

RESULTS: During the study period, 220 patients with penetrating neck injuries were admitted to our unit. Foley catheter balloon tamponade was used in 18 patients and was successful in 17 patients. Angiography was positive in 3 patients, all of whom underwent surgery. The FC was successfully removed in 13 patients at a mean of 72 (range 48-96) hours. One patient bled after removal of the catheter, mandating emergency surgery.

CONCLUSION: Foley catheter balloon tamponade remains a useful adjunct in the management of selective patients with penetrating, bleeding neck wounds.

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