Wilderness Medical Society Clinical Practice Guidelines for the Treatment of Acute Pain in Austere Environments: 2024 Update

The Wilderness Medical Society (WMS) convened an expert panel to develop evidence-based guidelines for the management of pain in austere environments. Recommendations are graded based on the quality of supporting evidence as defined by criteria put forth by the American College of Chest Physicians. This is an update of the 2014 version of the "WMS Practice Guidelines for the Treatment of Acute Pain in Remote Environments" published in Wilderness & Environmental Medicine 2014; 25:41-49.

Effects of the Lubo cervical collar on airway patency in awake adults - A magnetic resonance imaging study

Introduction: Intended for use by prehospital first responders, the Lubo ^TM cervical collar is an adjustable, radiolucent, single-use device that incorporates a mechanical jaw thrust mechanism. The combination enables non-invasive airway management in cases of trauma where cervical motion restriction is necessary. The potential benefits include use as an airway adjuvant maintaining upper airway patency, reducing provider task loading. The limited research on the device efficacy and safety requires further investigation.

Methods: A randomized, crossover, interventional study was performed to compare mean differences in airway patency at the level of the uvula, epiglottis, tongue and soft palate with and without the Lubo collar in awake volunteers using magnetic resonance imaging (MRI). Fourteen participants each underwent two MRI scans of the upper airway: A control scan with no Lubo collar, and an intervention scan with the Lubo collar applied and jaw thrust mechanism activated. Two independent radiologists measured anterior-posterior diameter of the airway at four anatomical levels on the resulting MRI images.

Results: There was no significant difference in mean airway diameter between the control and intervention measurements at any level. Mean (SD; 95% CI: p-value) differences were 0.9 mm (-2.38; 2.3 to 0.5; p=0.17) at the epiglottis, 0.5 mm (1.6; -0.5 to 1.4; p=0.29) at the soft palate, 0.2 mm (2.86; -1.4 to 1.9; p = 0.78) at the tongue, 0.4 mm (4.04; -1.9 to 2.7; p = 0.72) at the uvula.

Conclusion: The Lubo ^TM airway collar did not show a significant change in upper airway patency at four anatomical levels measured in awake adult participants. Further research is required to investigate its clinical use in patients that are unable to maintain upper airway tone. Groups of interest would include trauma, obstructive sleep apnoea, obesity and patients under general anaesthesia.

Intubation during spinal motion restriction using the LuboTM cervical collar - a manikin simulation study

Introduction

The Lubo^TM collar is a cervical motion restriction device featuring a unique external jaw-thrust mechanism designed to provide non-invasive airway patency. In addition, tracheal intubation is facilitated by releasing an anterior chin strap; this allows better mouth opening than the previous generation of semi-rigid cervical collars. This study aimed to compare tracheal intubation using the Lubo^TM collar combined with manual in-line stabilization (MILS) to intubation with MILS alone. The primary outcome was the time to successful intubation. Secondary outcomes compared intubation success rate, Cormack-Lehane grade, ease of intubation and dental trauma.

Methods

A randomized, cross-over, equivalence study was performed. Eighty full-time physician anaesthesia providers were recruited. Participants performed tracheal intubation using direct laryngoscopy on a manikin under two different scenarios: with the Lubo^TM collar and MILS applied, and with MILS and no cervical collar. The time to successful intubation was measured and compared using two-one-sided and paired t-tests.

Results

Intubation times fell well within the a priori equivalence limits of 10 seconds, with a mean difference (95% CI) of 0.52 seconds (-1.30 to 2.56). There was no significant difference in intubation time with the Lubo^TM collar (mean [SD] 19.2 [4.5] seconds) compared to the MILS alone group (19.7 [5.2] seconds). The overall success rate was 98.7% in the Lubo group and 100% in the MILS group. Adequate laryngoscopy views (Cormack-Lehane grades I to IIb) were equivalent between groups (Lubo 92.5% versus MILS alone 93.7%).

Conclusion

In this manikin-based study, the time to intubation with the Lubo^TM collar and MILS applied was equivalent to time to intubation with MILS alone, with similar intubating conditions. Thus, the Lubo^TM collar and MILS may simplify airway management by reducing the number of steps required to perform intubation in patients requiring cervical motion restriction.

General Anesthesia for Cesarean Delivery for Thrombocytopenia in Hypertensive Disorders of Pregnancy: Findings From the Obstetric Airway Management Registry

BACKGROUND

In resource-limited environments, spinal anesthesia (SA) is preferred for cesarean delivery. In women at risk of spinal epidural hematoma, particularly those with hypertensive disorders of pregnancy, thrombocytopenia should be excluded before neuraxial blockade. In the context of emergency surgery for fetal distress, this investigation may be hampered by laboratory services being unavailable or off-site.

METHODS

The Obstetric Airway Management Registry (ObAMR) is currently active across all anesthesia training institutions affiliated with the University of Cape Town. This multicenter observational study aimed to estimate the proportion of patients receiving general anesthesia (GA) for either confirmed or suspected thrombocytopenia, which was not excluded due to unavailability of laboratory results. To establish the number of GA uses that may have been avoided if platelet counts were available, we retrospectively searched for subsequent platelet counts in patients for whom thrombocytopenia was suspected. An algorithm was proposed, including a simple decision aid for estimating risk versus benefit of SA versus GA, to be followed in the setting of hypertensive disorders of pregnancy and thrombocytopenia.

RESULTS

Thrombocytopenia was the indication for GA in 100 of 591 patients (16.9%) captured in the registry. In total, 48 of 591 (8.1%) had confirmed thrombocytopenia, and 52 of 591 (8.8%) had suspected thrombocytopenia. Of these patients, 91 of 100 had a hypertensive disorder of pregnancy. In the confirmed thrombocytopenia group, the indication for GA was a platelet count <75 × 109/L. In the suspected thrombocytopenia group, 46 of 52 (88.5%) platelet counts could be retrospectively traced. The median (interquartile range) platelet count was 178 × 109/L (93 - 233 × 109/L), and platelets exceeded 75 × 109/L in 41 of 46 patients (89.1%). In the 5 of 46 patients with retrospectively confirmed thrombocytopenia, 2 had hemolysis, elevated liver enzymes, and low platelets (HELLP) syndrome, 2 had antepartum hemorrhage with preeclampsia, and 1 had isolated thrombocytopenia with preeclampsia.

CONCLUSIONS

In 17% of patients, the indication for GA was thrombocytopenia. Of these, 52 of 100, or nearly 9% of the total of 591, received GA because a platelet count was unavailable at the time of surgery. The importance of early laboratory assessment, when available, should be emphasized. Overall, 41 of 591 (6.9%) had a platelet count >75 × 109/L and would not have needed GA if their platelet count had been known. After following the constructed algorithm and applying the decision aid to assess risk and benefit, there may be circumstances in which the clinician justifiably opts for SA when a platelet count is indicated but unavailable.

Prospective Observational Trial of a Nonocclusive Dilatation Balloon in the Management of Tracheal Stenosis

OBJECTIVES

Tracheal stenosis is a debilitating condition that often presents as an emergency and is challenging to treat. Dilatation may avoid tracheostomy or costly tracheal resection and reconstruction. Traditional dilators cause complete occlusion, preventing oxygenation and ventilation, limiting the safe duration of dilatation, and increasing the risk of hypoxic injury or barotrauma. The study authors here assessed an innovative nonocclusive tracheal dilatation balloon, which may improve patient safety by allowing continuous gas exchange.

DESIGN

A prospective observational study of 20 discrete dilatation procedures performed in 13 patients under general anesthesia. The primary outcomes were the ability to ventilate during dilatation and the preservation of peripheral oxygen saturation. Secondary outcomes included a measured reduction in stenosis, improvement in Cotton-Myer grading, and procedure-related adverse events.

SETTING

At a single university (academic) hospital.

PARTICIPANTS

Consenting adult patients with acquired tracheal stenosis.

INTERVENTIONS

Access to the airway was maintained by a rigid bronchoscope or supraglottic airway device, as deemed appropriate. Continuous conventional ventilation was provided during 3-minute balloon dilatations.

MEASUREMENTS AND MAIN RESULTS

Heart rate, airway pressure, end-tidal carbon dioxide partial pressure, and peripheral oxygen saturation were measured, and adverse events were recorded. Ventilation was satisfactory in all patients. Peripheral saturation remained greater than 94% in 19 of the 20 (95%) procedures. Stenosis internal diameter and grading were improved. Two patients had minor reversible adverse events (coughing and laryngospasm), which did not prevent completion of the procedure.

CONCLUSIONS

The authors report the first human trial of the device, in which continuous conventional ventilation could be provided during all tracheal balloon dilatation procedures. Larger trials are needed to confirm improved patient safety and comparative efficacy.

Adapted full-face snorkel masks as an alternative for COVID-19 personal protection during aerosol generating procedures in South Africa: A multi-centre, non-blinded in-situ simulation study

INTRODUCTION

SARS-CoV-2 has resulted in increased worldwide demand for personal protective equipment (PPE). With pressure from ongoing epidemic and endemic episodes, we assessed an adapted snorkel mask that provides full-face protection for healthcare workers (HCWs), particularly during aerosol-generating procedures. These masks have a custom-made adaptor which allows the fitment of standard medical respiratory filters. The aim of this study was to evaluate the fit, seal and clinical usability of these masks.

METHODS

This multicentre, non-blinded in-situ simulation study recruited fifty-two HCWs to don and doff the adapted snorkel mask. Negative pressure seal checks and a qualitative fit test were performed. The HCWs completed intubation and extubation of a manikin in a university skills training laboratory, followed by a web-based questionnaire on the clinical usability of the masks.

RESULTS

Whilst fit and usability data were generally satisfactory, two of the 52 participants (3.8%) felt that the mask did not span the correct distance from the nose to the chin, and 3 of 34 participants (8.8%) who underwent qualitative testing with a Bitrex test failed. The majority of users reported no fogging, humidity or irritation. It was reportedly easy to speak while wearing the mask, although some participants perceived that they were not always understood. Twenty-one participants (40%) experienced a subjective physiological effect from wearing the mask; most commonly a sensation of shortness of breath.

DISCUSSION

A fit-tested modified full-face snorkel mask may offer benefit as a substitute for N95 respirators and face shields. It is, however, important to properly select the correct mask based on size, fit testing, quality of the three-dimensional (3D) printed parts and respiratory filter to be used. Additionally, HCWs should be trained in the use of the mask, and each mask should be used by a single HCW and not shared.

Endoscopic airway equipment part 2: equipment overview

Endoscopic devices designed for intubation include indirect optical and video laryngoscopes, rigid fibreoptic and video stylets, flexible and rigid bronchoscopes, and optic-enabled intubating supraglottic airways. Various types of surgical operating telescopes can also be used in specific circumstances. It is crucial to understand the strengths and weaknesses of different devices and blade types in order to match the device to the clinical challenge.

Endoscopic airway equipment part 1: physical principles

The use of advanced endoscopic airway equipment has become increasingly important to the provision of safe anaesthesia for patients with complex anatomical and pathological conditions. Fundamental to the correct selection and use of the equipment is an understanding of the physical properties underlying its construction and function. This relies primarily on conventional optics, fibreoptics, video sensors and light-emitting diode technology.

Hypoxaemia during tracheal intubation in patients with hypertensive disorders of pregnancy: analysis of data from an obstetric airway management registry

BACKGROUND

In South Africa, hypertensive disorders of pregnancy are the leading cause of maternal mortality. More than 50% of anaesthesia-related maternal deaths are attributed to complications of airway management. We compared the prevalence and risk factors for hypoxaemia during induction of general anaesthesia in parturients with and without hypertensive disorders of pregnancy. We hypothesised that hypertensive disorders of pregnancy are associated with desaturation during tracheal intubation.

METHODS

Data from 402 cases in a multicentre obstetric airway management registry were analysed. The prevalence of peri-induction hypoxaemia (SpO₂ <90%) was compared in patients with and without hypertensive disorders of pregnancy. Quantile regression of SpO₂ nadir was performed to identify confounding variables associated with, and mediators of, hypoxaemia.

RESULTS

In the cohort of 402 cases, hypoxaemia occurred in 19% with and 9% without hypertension (estimated risk difference, 10%; 95% CI 2% to 17%; P=0.005). Quantile regression demonstrated a lower SpO₂ nadir associated with hypertensive disorders of pregnancy as body mass index increased. Room-air oxygen saturation, Mallampati grade, and number of intubation attempts were associated with the relationship.

CONCLUSIONS

Clinically significant oxygen desaturation during airway management occurred twice as often in patients with hypertensive disorders of pregnancy, compounded by increasing body mass index. Intermediary factors in the pathway from hypertension to hypoxaemia were also identified.

Aerosol boxes and barrier enclosures for airway management in COVID-19 patients: a scoping review and narrative synthesis

Exposure of healthcare providers to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a significant safety concern during the coronavirus disease 2019 (COVID-19) pandemic, requiring contact/droplet/airborne precautions. Because of global shortages, limited availability of personal protective equipment (PPE) has motivated the development of barrier-enclosure systems, such as aerosol boxes, plastic drapes, and similar protective systems. We examined the available evidence and scientific publications about barrier-enclosure systems for airway management in suspected/confirmed COVID-19 patients. MEDLINE/Embase/Google Scholar databases (from December 1, 2019 to May 27, 2020) were searched for all articles on barrier enclosures for airway management in COVID-19, including references and websites. All sources were reviewed by a panel of experts using a Delphi method with a modified nominal group technique. Fifty-two articles were reviewed for their results and level of evidence regarding barrier device feasibility, advantages, protection against droplets and aerosols, effectiveness, safety, ergonomics, and cleaning/disposal. The majority of analysed papers were expert opinions, small case series, technical descriptions, small-sample simulation studies, and pre-print proofs. The use of barrier-enclosure devices adds to the complexity of airway procedures with potential adverse consequences, especially during airway emergencies. Concerns include limitations on the ability to perform airway interventions and the aid that can be delivered by an assistant, patient injuries, compromise of PPE integrity, lack of evidence for added protection of healthcare providers (including secondary aerosolisation upon barrier removal), and lack of cleaning standards. Enclosure barriers for airway management are no substitute for adequate PPE, and their use should be avoided until adequate validation studies can be reported.

Risk factors and interventions associated with mortality or survival in adult COVID-19 patients admitted to critical care: a systematic review and meta-analysis

Background: Patients with confirmed COVID-19 admitted to intensive care units have a high mortality rate, which appears to be associated with increasing age, male sex, smoking history, hypertension and diabetes mellitus. Methods: A systematic review to determine risk factors and interventions associated with mortality/survival in adult patients admitted to an intensive care unit (ICU) with confirmed COVID-19/SARS-CoV-2 infection. The protocol was registered with PROSPERO (CRD42020181185). Results: The search identified 483 abstracts between 1 January and 7 April 2020, of which nine studies were included in the final review. Only one study was of low bias. Advanced age (odds ratio [OR] 11.99, 95% confidence interval [CI] 5.35–18.62) and a history of hypertension were associated with mortality (OR 4.17, 95% CI 2.90–5.99). Sex was not associated with mortality. There was insufficient data to assess the association between other comorbidities, laboratory results or critical care risk indices and mortality. The critical care interventions of mechanical ventilation (OR 6.25, 95% CI 0.75–51.93), prone positioning during ventilation (OR 2.06, 95% CI 0.20–21.72), and extracorporeal membrane oxygenation (ECMO) (OR 8.00, 95% CI 0.69, 92.33) were not associated with mortality. The sample size was insufficient to conclusively determine the association between these interventions and ICU mortality. The need for inotropes or vasopressors was associated with mortality (OR 6.36, 95% CI 1.89–21.36). Conclusion: The studies provided little granular data to inform risk stratification or prognostication of patients requiring intensive care admission. Larger collaborative research is needed to address this limitation.

Clinical Evaluation of Measuring the ACT during Elective Cardiac Surgery with Two Different Devices

Unfractionated heparin is the mainstay of anticoagulation during cardiac surgery on cardiopulmonary bypass (CPB) due to its low cost, quick onset, and ease of reversal. Since over 30 years, the activated clotting time (ACT) has been used to assess the level of heparin activity both before and after CPB. We compared two different methods of measuring the ACT: i-STAT, which uses amperometric detection of thrombin cleavage, and Hemochron Jr, which is based on detecting viscoelastic changes in blood. We included 402 patients from three institutions (Papworth Hospital, Cambridge, UK; Groote Schuur, Cape Town, South Africa; University Hospital Basel, Basel, Switzerland) undergoing elective cardiac surgery on CPB in our study. We analyzed duplicate samples on both devices at all standard measuring points during the procedure. The correlation coefficient between two Hemochron and two i-STAT devices was .9165 and .9857, respectively. The within-subject coefficient of variation (WSCV) ranged from 8.2 to 13.6% for the Hemochron and from 4.1 to 9.1% for the i-STAT. We found that the number of occasions where one of the duplicate readings was >1,000 seconds while the other was below or close to the clinically significant threshold of 400 seconds were higher for the Hemochron. We found the i-STAT to systematically return higher measurements. We conclude that the i-STAT provides a more reliable test for heparin activity and assesses safe anticoagulation during cardiac surgery on pump. The fact the that the i-STAT reads higher than the Hemochron leads to the recommendation to validate the methods against each other before changing devices.