I’ve been too busy to blog literature updates for a couple of weeks since I and my colleagues have been flat out running a two week training course in prehospital and retrieval medicine.
Our Helicopter Emergency Medical Service physicians and paramedics care for a wide range of adult and paediatric trauma and critical care patients in some challenging environments. We therefore need to provide a fairly comprehensive induction course for new recruits.
The new guys did us proud. They just need to stay this awesome.
Category Archives: PHARM
Prehospital and Retrieval Medicine
FIRST: Fluids in Resuscitation of Severe Trauma
This is the first randomized, controlled, double-blind study comparing crystalloids with isotonic colloids in trauma. 0.9% saline was compared with hydroxyethyl starch, HES 130/0.4, as a resuscitation fluid in pre-defined subgroups of penetrating and blunt trauma. While a primary outcome measure of gastrointestinal recovery might not seem an obvious choice to some of us, previous research has indicated this to be an issue with crystalloid and the authors clearly defined this as a predefined outcome when registering the trial here.
Colloids tend to require smaller volumes than crystalloid to achieve the same degree of plasma expansion. An interesting finding in this study is that the volume of saline administered was 1.5 times that of hydroxyethyl starch – a very similar ratio to that seen in the SAFE study which compared saline with 4% albumin in intensive care patients.
The authors assert: “..the better lactate clearance in the P-HES group indicated superior tissue resuscitation with the colloid.” There are a number of reasons why this might be a bit of stretch, including the use of epinephrine in some patients which is known to be a cause of hyperlactataemia.
This is a small study whose conclusions should be treated with caution, but which provides an important contribution to the pool of fluid resuscitation literature. If you have full text access to the British Journal of Anaesthesia, the letters pages provide excellent critiques and responses regarding potential flaws in this paper. Nevertheless, it’s one to know about – I’m sure the FIRST trial is going to be quoted for some time to come, including, I suspect, by the manufacturers of certain colloids.
Background The role of fluids in trauma resuscitation is controversial. We compared resuscitation with 0.9% saline vs hydroxyethyl starch, HES 130/0.4, in severe trauma with respect to resuscitation, fluid volume, gastrointestinal recovery, renal function, and blood product requirements.
Methods Randomized, controlled, double-blind study of severely injured patients requiring>3 litres of fluid resuscitation. Blunt and penetrating trauma were randomized separately. Patients were followed up for 30 days.
Results A total of 115 patients were randomized; of which, 109 were studied. For patients with penetrating trauma (n=67), the mean (sd) fluid requirements were 5.1 (2.7) litres in the HES group and 7.4 (4.3) litres in the saline group (P<0.001). In blunt trauma (n=42), there was no difference in study fluid requirements, but the HES group required significantly more blood products [packed red blood cell volumes 2943 (1628) vs 1473 (1071) ml, P=0.005] and was more severely injured than the saline group (median injury severity score 29.5 vs 18; P=0.01). Haemodynamic data were similar, but, in the penetrating group, plasma lactate concentrations were lower over the first 4 h (P=0.029) and on day 1 with HES than with saline [2.1 (1.4) vs 3.2 (2.2) mmol litre−1; P=0.017]. There was no difference between any groups in time to recovery of bowel function or mortality. In penetrating trauma, renal injury occurred more frequently in the saline group than the HES group (16% vs 0%; P=0.018). In penetrating trauma, maximum sequential organ function scores were lower with HES than with saline (median 2.4 vs 4.5, P=0.012). No differences were seen in safety measures in the blunt trauma patients.
Conclusions In penetrating trauma, HES provided significantly better lactate clearance and less renal injury than saline. No firm conclusions could be drawn for blunt trauma.
Resuscitation with hydroxyethyl starch improves renal function and lactate clearance in penetrating trauma in a randomized controlled study: the FIRST trial (Fluids in Resuscitation of Severe Trauma)
Br J Anaesth. 2011 Nov;107(5):693-702
A big brain saves a little one
Something I’ve been teaching for years – but never actually done – has been described in a case report from Oman.
A 2 year old child suffered a respiratory arrest due to an inhaled foreign body, which led to a bradyasystolic cardiac arrest. She was intubated by the resuscitation team who could not achieve any ventilation through the tube. The tube was removed and reinserted by an ‘expert’ (there is no mention of capnometry, for what it’s worth) and the same problem persisted.
The life-saving manouevre was to insert the tracheal tube further down into the right main bronchus and then withdraw to the trachea. This forced the obstructing object distally so that one-lung ventilation was then possible, resulting in return of spontaneous circulation and oxygen saturations in the mid-80’s. The object – a broken piece of plastic – was removed bronchoscopically and happily the child made an uneventful recovery.
Is this technique in your list of life-saving tricks? Hopefully, it is now.
A child is alive because a doctor was able to ‘think outside the guidelines’ in an incredibly high pressure situation. Rigid adherence to ACLS procedures here would have been futile. The guidelines save lives, but a few more can be saved when care can be individualised to the clinical situation by a thinking clinician.
Well done Dr Mishra and colleagues.
Sudden near-fatal tracheal aspiration of an undiagnosed nasal foreign body in a small child
Emerg Med Australas. 2011 Dec;23(6):776-8
[And here’s something else to consider if you have no airway equipment with you and your basic choking algorithm isn’t working]
Emergency percutaneous airway
An excellent thorough review of emergency needle and surgical cricothyroidotomy – collectively described as ’emergency percutaneous airway’ – reveals a number of pearls.
Regarding anatomy:
- The cricothyroid menbrane has an average height of 10 mm and a width of 11 mm
- Transverse incision in the lower half of the cricothyroid membrane is recommended to avoid the cricothyroid arteries and the vocal cords
Regarding oxygenation / ventilation via a cricothyroid needle:
- High pressure source ventilation via a needle (eg. by Sanders injector or Manujet) may cause laryngospasm, so a neuromuscular blocking agent should be considered
- Barotrauma may result from an obstructed upper airway, so efforts should be made to maintain upper airway patency where possible (eg. with a supraglottic airway)
- A device has been manufactured that provides suction-generated expiratory ventilation assistance (using oxygen flow and the Bernoulli principle) – the Ventrain
- The Fourth National Audit Project reported a much lower success rate and described several complications of attempted re-oxygenation via a narrow-bore cricothyroidotomy
- Where there is no kink-resistant cannula or suitable high-pressure source ventilation device readily available, it is probably safer to perform a wide-bore cannula puncture or surgical cricothyroidotomy.
Wide-bore cannula-over trocar devices:
- Include the Quicktrach II and Portex cricothyroidotomy kit
- Sometimes require considerable force to push the device through the cricothyroid membrane, risking compression of the airway and damage or perforation of the posterior tracheal wall.
Seldinger cricothyroidotomy kits:
- Separate the puncture and dilatation steps, minimising the risk of trauma
- Include the Melker emergency cricothyroidotomy set, available in sizes 3.0–6.0 mm ID
- Tend to be preferred by anaesthetists over the surgical and wide-bore cannula-over-trocar techniques
- Seldinger technique in human cadavers and manikin studies by those well trained, inexperienced operators have low success rates and a long performance time
What about after?
- High-pressure source ventilation may aid subsequent intubation by direct laryngoscopy as bubbles may be seen emerging from the glottis.
- The Seldinger technique has been recommended to convert a narrow-bore cannula into a cuffed wide-bore cricothyroidotomy
- While conversion of cricothyroidotomy to tracheostomy within 72 h has been advocated because of the increased risk of developing subglottic stenosis with prolonged intubation through the cricothyroid membrane, this risk may be much lower than previously believed
- The risk of conversion, although less well examined, may also be appreciable
Which technique is best?
- The recent NAP4 audit reported a success rate of only 37% for narrow-bore cannula-over-needle cricothyroidotomy, 57% for wide-bore cannula techniques and 100% for surgical cricothyroidotomy
- Simulation studies show conflicting results about whether seldinger or surgical technique is faster.
- Reported success rates of the different techniques (in simulations) also vary widely and range for surgical cricothyroidotomy from 55% to 100%, for wide-bore cannula-over-trocar from 30% to 100%, and for Seldinger technique from 60% to 100%.
The one area of some consensus is that conventional (low-pressure source) ventilation should not be used with a narrow-bore cannula; a high-pressure oxygen source and a secure pathway for the egress of gas are both mandatory to achieve adequate ventilation.
Complications may be related to technique:
- Complications of narrow-bore cannula techniques are ventilation-related and include barotrauma, subcutaneous emphysema, pneumothorax, pneumomediastinum and circulatory arrest due to impaired venous return; Cannula obstruction due to kinking also occurs.
- Seldinger technique may be complicated by kinking of the guidewire, which increases the risk of tube misplacement
- Bleeding and laryngeal fracture may complicate the surgical method, and long-term complications include subglottic stenosis, scarring and voice changes.
Equipment and strategies for emergency tracheal access in the adult patient
Anaesthesia. 2011 Dec;66 Suppl 2:65-80
Two new anaphylaxis guidelines
Many local and national guidelines for the management of anaphylaxis exist, but did you know there was a World Allergy Organization, and it has a very detailed guideline on this important life threatening condition?
Some interesting snippets from the guideline are included here
Anaphylaxis and cardiac disease
- Anaphylaxis can precipitate acute myocardial infarction in susceptible individuals: in patients with ischemic heart disease, the number and density of cardiac mast cells is increased, including in the atherosclerotic plaques. Mediators released during anaphylaxis contribute to vasoconstriction and coronary artery spasm.
- Epinephrine is not contraindicated in the treatment of anaphylaxis in patients with known or suspected cardiovascular disease, or in middle-aged or elderly patients without any history of coronary artery disease who are at increased risk of ACS only because of their age. Through its beta-1 adrenergic effects, epinephrine actually increases coronary artery blood flow because of an increase in myocardial contractility and in the duration of diastole relative to systole.
- Glucagon has noncatecholamine-dependent inotropic and chronotropic cardiac effects, and is sometimes needed in patients taking a beta-adrenergic blocker who have hypotension and bradycardia and who do not respond optimally to epinephrine.
- Anticholinergic agents are sometimes needed in beta-blocked patients, for example, atropine in those with persistent bradycardia or ipratropium in those with epinephrine-resistant bronchospasm.
How quickly can untreated anaphylaxis kill you?
Studies show median times to cardiorespiratory arrest after exposure to the offending stimulus were 5 minutes after administration of contrast media or drugs, 15 minutes after an insect sting, and 30 minutes after food ingestion.
What about confirming the diagnosis with serum tryptase measurements?
- Blood samples for measurement of tryptase levels are optimally obtained 15 minutes to 3 hours after symptom onset.
- Blood samples for measurement of histamine levels are optimally obtained 15–60 minutes after symptom onset. These tests are not specific for anaphylaxis.
- Increased serum tryptase levels are often found in patients with anaphylaxis from insect stings or injected medications, and in those who are hypotensive
- However, levels are often within normal limits in patients with anaphylaxis triggered by food and in those who are normotensive
- Serial measurement of tryptase levels during an anaphylactic episode, and measurement of a baseline level after recovery are reported to be more useful than measurement at only one point in time.
- Normal levels of either tryptase or histamine do not rule out the clinical diagnosis of anaphylaxis
How does epinephrine help?
- Epinephrine is life-saving because of its alpha-1 adrenergic vasoconstrictor effects in most body organ systems (skeletal muscle is an important exception) and its ability to prevent and relieve airway obstruction caused by mucosal edema, and to prevent and relieve hypotension and shock.
- Other relevant properties in anaphylaxis include its beta-1 adrenergic agonist inotropic and chronotropic properties leading to an increase in the force and rate of cardiac contractions, and its beta-2 adrenergic agonist properties such as decreased mediator release, bronchodilation and relief of urticaria
- Epinephrine in a dose of 0.01 mg/kg of a 1:1,000 (1 mg/mL) solution injected promptly by the intramuscular route is effective and safe in the initial treatment of anaphylaxis. In other anaphylaxis scenarios, this low first-aid dose is unlikely to be effective. For example, if shock is imminent or has already developed, epinephrine needs to be given by slow intravenous infusion, ideally with the dose titrated according to noninvasive continuous cardiac monitoring.
What is the empty ventricle syndrome?
- Patients with anaphylaxis should not suddenly sit, stand, or be placed in the upright position.
- Instead, they should be placed on the back with their lower extremities elevated or, if they are experiencing respiratory distress or vomiting, they should be placed in a position of comfort with their lower extremities elevated.
- This accomplishes 2 therapeutic goals: 1) preservation of fluid in the circulation (the central vascular compartment), an important step in managing distributive shock; and 2) prevention of the empty vena cava/empty ventricle syndrome, which can occur within seconds when patients with anaphylaxis suddenly assume or are placed in an upright position.
- Patients with this syndrome are at high risk for sudden death. They are unlikely to respond to epinephrine regardless of route of administration, because it does not reach the heart and therefore cannot be circulated throughout the body
Should we give antihistamines, beta 2 agonists, and steroids?
The evidence base for use of these second line medications in the initial management of anaphylaxis, is extrapolated mainly from their use in treatment of other diseases such as urticaria (antihistamines) or acute asthma (beta-2 adrenergic agonists and glucocorticoids). Concerns have been raised that administering one or more second-line medications potentially delays prompt injection of epinephrine, the first-line treatment
Is ‘biphasic anaphylaxis’ a real phenomenon we should be concerned about?
- Biphasic anaphylaxis occurs when symptoms recur within 1–72 hours (usually within 8–10 hours) after the initial symptoms have resolved, despite no further exposure to the trigger.
- It occurs in up to 23% of adults and up to 11% of children.
- After apparent resolution of symptoms, duration of monitoring in a medically supervised setting should be individualized. For example, patients with moderate respiratory or cardiovascular compromise should be monitored for at least 4 hours, and if indicated, for 8–10 hours or longer.
- Protracted uniphasic anaphylaxis is uncommon, but can last for days.
World Allergy Organization Guidelines for the Assessment and Management of Anaphylaxis
World Allergy Organization Journal 2011;4(2):13-37 Full Text
[EXPAND click for abstract]
The illustrated World Allergy Organization (WAO) Anaphylaxis Guidelines were created in response to absence of global guidelines for anaphylaxis. Uniquely, before they were developed, lack of worldwide availability of essentials for the diagnosis and treatment of anaphylaxis was documented. They incorporate contributions from more than 100 allergy/immunology specialists on 6 continents. Recommendations are based on the best evidence available, supported by references published to the end of December 2010. The Guidelines review patient risk factors for severe or fatal anaphylaxis, co-factors that amplify anaphylaxis, and anaphylaxis in vulnerable patients, including pregnant women, infants, the elderly, and those with cardiovascular disease. They focus on the supreme importance of making a prompt clinical diagnosis and on the basic initial treatment that is urgently needed and should be possible even in a low resource environment. This involves having a written emergency protocol and rehearsing it regularly; then, as soon as anaphylaxis is diagnosed, promptly and simultaneously calling for help, injecting epinephrine (adrenaline) intramuscularly, and placing the patient on the back or in a position of comfort with the lower extremities elevated. When indicated, additional critically important steps include administering supplemental oxygen and maintaining the airway, establishing intravenous access and giving fluid resuscitation, and initiating cardiopulmonary resuscitation with continuous chest compressions. Vital signs and cardiorespiratory status should be monitored frequently and regularly (preferably, continuously). The Guidelines briefly review management of anaphylaxis refractory to basic initial treatment. They also emphasize preparation of the patient for self-treatment of anaphylaxis recurrences in the community, confirmation of anaphylaxis triggers, and prevention of recurrences through trigger avoidance and immunomodulation. Novel strategies for dissemination and implementation are summarized. A global agenda for anaphylaxis research is proposed.
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This month has also seen the publication guidelines from the UK’s National Institute for Health & Clinical Excellence, entitled ‘Anaphylaxis: assessment to confirm an anaphylactic episode and the decision to refer after emergency treatment for a suspected anaphylactic episode’
Their guideline summary is as follows:
After a suspected anaphylactic reaction in adults or young people aged 16 years or older, take timed blood samples for mast cell tryptase testing as follows:
- a sample as soon as possible after emergency treatment has started
- a second sample ideally within 1–2 hours (but no later than 4 hours) from the onset of symptoms.
After a suspected anaphylactic reaction in children younger than 16 years, consider taking blood samples for mast cell tryptase testing as follows if the cause is thought to be venom-related, drug-related or idiopathic:
- a sample as soon as possible after emergency treatment has started
- a second sample ideally within 1–2 hours (but no later than 4 hours) from the onset of symptoms.
Patients who have had emergency treatment for suspected anaphylaxis should be observed for 6–12 hours from the onset of symptoms, depending on their response to emergency treatment
After emergency treatment for suspected anaphylaxis, offer people a referral to a specialist allergy service (age-appropriate where possible) consisting of healthcare professionals with the skills and competencies necessary to accurately investigate, diagnose, monitor and provide ongoing management of, and patient education about, suspected anaphylaxis.
After emergency treatment for suspected anaphylaxis, offer people (or, as appropriate, their parent and/or carer) an appropriate adrenaline injector as an interim measure before the specialist allergy service appointment.
Before discharge a healthcare professional with the appropriate skills and competencies should offer people (or, as appropriate, their parent and/or carer) the following:
- information about anaphylaxis, including the signs and symptoms of an anaphylactic reaction
- information about the risk of a biphasic reaction
- information on what to do if an anaphylactic reaction occurs (use the adrenaline injector and call emergency services)
Anaphylaxis: assessment to confirm an anaphylactic episode and the decision to refer after emergency treatment for a suspected anaphylactic episode
CG134 Anaphylaxis: NICE guideline
Listen over the neck when inflating ETT cuff
This interesting study introduces a novel technique for guiding the inflation of tracheal tube cuffs to avoid excessive cuff pressures: listening with a stethoscope over the thyroid cartilage and inflating the cuff until breath sounds change from harsh to soft.
Tracheal tube cuffs are commonly inflated to pressures exceeding the recommended upper limit of 30 cmH2O. We evaluated whether a stethoscope-guided method of cuff inflation results in pressures within the recommended range. Patients were randomly assigned to receive one of two methods of cuff inflation. In the standard ‘just seal’ group, air was introduced into the tracheal cuff until the audible leak at the mouth disappeared. In the stethoscope-guided group, air was introduced into the cuff until a change from harsh to soft breath sounds occurred, whilst listening with a stethoscope bell placed over the thyroid cartilage. Twenty-five patients were recruited
to each group. The median (IQR [range]) cuff pressure in the ‘just seal’ group was 34 (28–40 [18–49]) cmH2O, and in the stethoscope-guided group was 20 (20–26 [16–28]) cmH2O,
p < 0.0001. The stethoscope-guided method of tracheal tube cuff inflation is a novel, simple technique that reliably results in acceptable tracheal cuff pressures.
Clinical evaluation of stethoscope-guided inflation of tracheal tube cuffs
Anaesthesia. 2011 Nov;66(11):1012-6
Make space for pre-hospital intubation
“Control your environment – don’t let it control you” is a reliable adage for pre-hospital providers, and its adherence can assist in in-hospital resuscitation too. Commanding control of ones space is a skill demonstrated by more seasoned paramedics compared with novices and the requirement, where possible, for 360 degrees of access around a patient is included in some Standard Operating Procedures for pre-hospital rapid sequence intubation.
Evidence for this approach is now further supported by a study demonstrating that limited surrounding space on scene was a significant risk factor for difficult pre-hospital intubation by European EMS physicians.
Other predisposing factors for difficult prehospital intubation included obesity and a short neck.
OBJECTIVES:For experienced personnel endotracheal intubation (ETI) is the gold standard to secure the airway in prehospital emergency medicine. Nevertheless, substantial procedural difficulties have been reported with a significant potential to compromise patients’ outcomes. Systematic evaluation of ETI in paramedic operated emergency medical systems (EMS) and in a mixed physician/anaesthetic nurse EMS showed divergent results. In our study we systematically assessed factors associated with difficult ETI in an EMS exclusively operating with physicians.
METHODS:Over a 1-year period we prospectively collected data on the specific conditions of all ETIs of two physician staffed EMS vehicles. Difficult ETI was defined by more than 3 attempts or a difficult visualisation of the larynx (Cormack and Lehane grade 3, or worse). For each patient ETI conditions, biophysical characteristics and factors of the surrounding scene were assessed. Additionally, physicians were asked whether they had expected difficult ETI in advance.
RESULTS:Out of 3979 treated patients 305 (7.7%) received ETI. For 276 patients complete data sets were available. The incidence of difficult ETI was 13.0%. In 4 cases (1.4%) ETI was impossible, but no patient was unable to be ventilated sufficiently. Predicting conditions for difficult intubation were limited surrounding space on scene (p<0.01), short neck (p<0.01), obesity (p<0.01), face and neck injuries (p<0.01), mouth opening<3cm (p<0.01) and known ankylosing spondylitis (p<0.01). ETI on the floor or with C-spine immobilisation in situ were of no significant influence. The incidence of unexpected difficult ETI was 5.0%.
CONCLUSIONS: In a physician staffed EMS difficult prehospital ETI occurred in 13% of cases. Predisposing factors were limited surrounding space on scene and certain biophysical conditions of the patient (short neck, obesity, face and neck injuries, and anatomical restrictions). Unexpected difficult ETI occurred in 5% of the cases.
Difficult prehospital endotracheal intubation – predisposing factors in a physician based EMS
Resuscitation. 2011 Dec;82(12):1519-24
More on needle thoracostomy for tension pneumothorax
Thanks to Dr. Matthew Oliver for highlighting these articles to me.
The standard teaching of placing a handy iv catheter in the 2nd intercostal space, midclavicular line for tension pneumothorax has been challenged by previous studies suggesting about a third of adults have a chest wall that is too thick for a standard 4.5 to 5 cm needle.
Some have therefore suggested that a lateral approach may be more appropriate.
Three studies this month provide more, although not entirely consistent, information.
An ultrasound study differed from previous CT studies by suggesting that most patients will have chest wall thickness (CWT) less than 4.5 cm, and found that the CW was thicker in the lateral area (4th intercostal space, midaxillary line)1.
In a cadaveric model, needle thoracostomy was successfully placed (confirmed by thoracotomy) in all attempts at the fifth intercostal space at the midaxillary line but in only just over half of insertions at the traditional second intercostal position2.
In a further study of trauma CT scans, measured CWT suggests that the lateral approach is less likely to be successful than the anterior approach, and the anterior approach may fail in many patients as well3.
The take home message for us must therefore remain that needle thoracostomy for tension pneumothorax might not be successful with a standard iv catheter, regardless of which approach is used. If tension pneumothorax is a possibility in the deteriorating patient and needle decompression has been unsuccessful, an alternative means of decompression (or ruling out pneumothorax) must be employed.
1. Ultrasound determination of chest wall thickness: implications for needle thoracostomy
Am J Emerg Med. 2011 Nov;29(9):1173-7
[EXPAND Abstract]
Objective: Computed tomography measurements of chest wall thickness (CWT) suggest that standard- length angiocatheters (4.5 cm) may fail to decompress tension pneumothoraces. We used an alternative modality, ultrasound, to measure CWT. We correlated CWT with body mass index (BMI) and used national data to estimate the percentage of patients with CWT greater than 4.5 cm.
Methods: This was an observational, cross-sectional study of a convenience sample. We recorded standing height, weight, and sex. We measured CWT with ultrasound at the second intercostal space, midclavicular line and at the fourth intercostal space, midaxillary line on supine subjects. We correlated BMI (weight [in kilograms]/height2 [in square meters]) with CWT using linear regression. 95% Confidence intervals (CIs) assessed statistical significance. National Health and Nutrition Examination Survey results for 2007-2008 were combined to estimate national BMI adult measurements.
Results: Of 51 subjects, 33 (65%) were male and 18 (35%) were female. Mean anterior CWT (male, 2.1 cm; CI, 1.9-2.3; female, 2.3 cm; CI, 1.7-2.7), lateral CWT (male, 2.4 cm; CI, 2.1-2.6; female, 2.5 cm; CI 2.0-2.9), and BMI (male, 27.7; CI, 26.1-29.3; female, 30.0; CI, 25.8-34.2) did not differ by sex. Lateral CWT was greater than anterior CWT (0.2 cm; CI, 0.1-0.4; P < .01). Only one subject with a BMI of 48.2 had a CWT that exceeded 4.5 cm. Using national BMI estimates, less than 1% of the US population would be expected to have CWT greater than 4.5 cm.
Conclusions: Ultrasound measurements suggest that most patients will have CWT less than 4.5 cm and that CWT may not be the source of the high failure rate of needle decompression in tension pneumothorax.
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2. Anterior versus lateral needle decompression of tension pneumothorax: comparison by computed tomography chest wall measurement.
Acad Emerg Med. 2011 Oct;18(10):1022-6
[EXPAND Abstract]
Objectives: Recent research describes failed needle decompression in the anterior position. It has been hypothesized that a lateral approach may be more successful. The aim of this study was to identify the optimal site for needle decompression.
Methods: A retrospective study was conducted of emergency department (ED) patients who underwent computed tomography (CT) of the chest as part of their evaluation for blunt trauma. A convenience sample of 159 patients was formed by reviewing consecutive scans of eligible patients. Six measurements from the skin surface to the pleural surface were made for each patient: anterior second intercostal space, lateral fourth intercostal space, and lateral fifth intercostal space on the left and right sides.
Results: The distance from skin to pleura at the anterior second intercostal space averaged 46.3 mm on the right and 45.2 mm on the left. The distance at the midaxillary line in the fourth intercostal space was 63.7 mm on the right and 62.1 mm on the left. In the fifth intercostal space the distance was 53.8 mm on the right and 52.9 mm on the left. The distance of the anterior approach was statistically less when compared to both intercostal spaces (p < 0.01).
Conclusions: With commonly available angiocatheters, the lateral approach is less likely to be successful than the anterior approach. The anterior approach may fail in many patients as well. Longer angiocatheters may increase the chances of decompression, but would also carry a higher risk of damage to surrounding vital structures.
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3. Optimal Positioning for Emergent Needle Thoracostomy: A Cadaver-Based Study
J Trauma. 2011 Nov;71(5):1099-1103/a>
[EXPAND Abstract]
Background: Needle thoracostomy is an emergent procedure designed to relieve tension pneumothorax. High failure rates because of the needle not penetrating into the thoracic cavity have been reported. Advanced Trauma Life Support guidelines recommend placement in the second intercostal space, midclavicular line using a 5-cm needle. The purpose of this study was to evaluate placement in the fifth intercostal space, midaxillary line, where tube thoracostomy is routinely performed. We hypothesized that this would result in a higher successful placement rate.
Methods: Twenty randomly selected unpreserved adult cadavers were evaluated. A standard 14-gauge 5-cm needle was placed in both the fifth intercostal space at the midaxillary line and the traditional second intercostal space at the midclavicular line in both the right and left chest walls. The needles were secured and thoracotomy was then performed to assess penetration into the pleural cavity. The right and left sides were analyzed separately acting as their own controls for a total of 80 needles inserted into 20 cadavers. The thickness of the chest wall at the site of penetration was then measured for each entry position.
Results: A total of 14 male and 6 female cadavers were studied. Overall, 100% (40 of 40) of needles placed in the fifth intercostal space and 57.5% (23 of 40) of the needles placed in the second intercostal space entered the chest cavity (p < 0.001); right chest: 100% versus 60.0% (p = 0.003) and left chest: 100% versus 55.0% (p = 0.001). Overall, the thickness of the chest wall was 3.5 cm ± 0.9 cm at the fifth intercostal space and 4.5 cm ± 1.1 cm at the second intercostal space (p < 0.001). Both right and left chest wall thicknesses were similar (right, 3.6 cm ± 1.0 cm vs. 4.5 cm ± 1.1 cm, p = 0.007; left, 3.5 ± 0.9 cm vs. 4.4 cm ± 1.1 cm, p = 0.008).
Conclusions:In a cadaveric model, needle thoracostomy was successfully placed in 100% of attempts at the fifth intercostal space but in only 58% at the traditional second intercostal position. On average, the chest wall was 1 cm thinner at this position and may improve successful needle placement. Live patient validation of these results is warranted.
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Update October 2012: See this post about a further CT-scan based study favouring the 5th ICS compared with the 2nd
Tension pneumo treatment and chest wall thickness
An interesting ultrasound-based study challenges the assertion that a significant proportion of adults have a chest wall that is too thick for a standard iv cannula to reach the pleural space when attempting to decompress a tension pneumothorax. Perhaps there are other factors that make this technique so frequently ineffective.
The authors postulate that ultrasound measurements of chest wall thickness might be less than those obtained by CT scan due to the downward pressure on the tissues caused when the ultrasound transducer is placed on the chest, something that may also occur when a cannula is being pushed in, but would not be maintained after insertion of a cannula, perhaps leading to subsequent misplacement as the tissues recoil.
My view is that needle decompression might buy you time as a holding measure, but the patient with a tension pneumothorax will need a thoracostomy sooner rather than later.
Objective: Computed tomography measurements of chest wall thickness (CWT) suggest that standard- length angiocatheters (4.5 cm) may fail to decompress tension pneumothoraces. We used an alternative modality, ultrasound, to measure CWT. We correlated CWT with body mass index (BMI) and used national data to estimate the percentage of patients with CWT greater than 4.5 cm.
Methods: This was an observational, cross-sectional study of a convenience sample. We recorded standing height, weight, and sex. We measured CWT with ultrasound at the second intercostal space, midclavicular line and at the fourth intercostal space, midaxillary line on supine subjects. We correlated BMI (weight [in kilograms]/height2 [in square meters]) with CWT using linear regression. 95% Confidence intervals (CIs) assessed statistical significance. National Health and Nutrition Examination Survey results for 2007-2008 were combined to estimate national BMI adult measurements.
Results: Of 51 subjects, 33 (65%) were male and 18 (35%) were female. Mean anterior CWT (male, 2.1 cm; CI, 1.9-2.3; female, 2.3 cm; CI, 1.7-2.7), lateral CWT (male, 2.4 cm; CI, 2.1-2.6; female, 2.5 cm; CI 2.0-2.9), and BMI (male, 27.7; CI, 26.1-29.3; female, 30.0; CI, 25.8-34.2) did not differ by sex. Lateral CWT was greater than anterior CWT (0.2 cm; CI, 0.1-0.4; P <.01). Only one subject with a BMI of 48.2 had a CWT that exceeded 4.5 cm. Using national BMI estimates, less than 1% of the US population would be expected to have CWT greater than 4.5 cm.
Conclusions: Ultrasound measurements suggest that most patients will have CWT less than 4.5 cm and that CWT may not be the source of the high failure rate of needle decompression in tension pneumothorax.
Ultrasound determination of chest wall thickness: implications for needle thoracostomy
Am J Emerg Med. 2011 Nov;29(9):1173-7
2011 Asthma Guidelines
The British Thoracic Society / SIGN Guidelines on asthma have been updated for 2011. There don’t seem to be any modificiations to the sections on acute severe asthma which were updated in 2009 and blogged here, although the treatment algorithms seem to be presented in a slightly different format and therefore are reproduced here:
Management of acute severe asthma in adults in hospital
Management of acute asthma in children in hospital
