This study focuses on emergency patients > 15 years of age, nearly half of whom received analgesic therapy in a potentially life-threatening condition (NACA > 3). Injuries were predominantly fractures, with the upper or lower extremities most often affected. Main substances administered were opioids (fentanyl > piritramide > morphine) followed by esketamine, metamizole and NSAIDs. With analgesic monotherapy being the most common regimen, males proportionally received opioids more often than did females. Following opioids or esketamine only, opioids with esketamine or opioids with metamizole were the most common combination therapies. As shown by the development of MEES, respiratory rates, oxygen saturation and the non-necessity of mechanical ventilation during transport, application of potent analgesics was very safe in the described setting. A total of 10% of the analysed HEMS operations were performed without technical monitoring which could be due to various reasons like short transportation time, cold weather and winter clothes, technical rescue operations or even patient’s medical condition. Regarding pain relief, a higher fraction of females still had moderate to severe pain on hospital arrival. In total, pain levels decreased significantly, and administration seemed safe, thus justifying the liberal use of potent analgesics in HEMS.
This study presents a large retrospective analysis of a nationwide registry covering 14 physician-staffed helicopter bases in Austria over a 12-year timeframe. To date, only few studies of this size have been published on prehospital analgesia in HEMS.
Demographics and general emergency characteristics
Current publications on analgesia in HEMS originate in the combat setting, in particular with the U.S. armed forces in Afghanistan [11,12,13,14]. Affected patients were primarily young male soldiers who suffered acute trauma due to blast or penetrating injuries. Civilian HEMS operations report data from Europe [3,4,5,6, 15, 16] and also Australia . The data analysed show that 34.3% of patients received analgesic therapy. This compares with the figures reported for HEMS operations in Victoria, Australia (89%) , Germany (79%) , Switzerland (57–84%) [15, 17]. Regarding ground-based EMS, two studies from Europe reported a percentage of 48% of all patients [2, 3], whereas merely 3% of all trauma patients in a South African study received any kind of analgesic medication . As shown in other studies conducted in Austria, a high density of HEMS in combination with a mountainous landscape often prompts airborne rescue of merely mildly or even non-injured patients [19, 20]. This can also be seen from our data, where a total of 44.6% of all HEMS operations were classified as NACA ≤ 3. This may explain the rather small percentage of patients receiving analgesia in this study.
Analgesics commonly used
Analgesia administered during EMS may vary depending on type (HEMS/ EMS) and staffing (e.g. paramedic vs. physician) including the training level of the providers (anaesthesiologist vs. general practitioner, specialist vs. trainee, BLS vs. ALS provider, clinical experience). In systems with a large volume of emergency operations staffed at most with BLS/ILS providers, administration of i.v. analgesics is limited . Nitrous oxide can be an option, but is mainly used in some English-speaking countries . Another inhalational analgesic is low-dose methoxyflurane [21, 22]. Despite its undeniable advantages, as in quick, easy and safe administration also by non-physicians, its distribution seems very limited up to date (e.g. Australia, Italy). Moreover, as also confirmed in this study, opioids and ketamine/ esketamine predominate in the prehospital management of moderate to severe pain [2,3,4,5, 11,12,13,14]. Whether racemic ketamine or its S-enantiomer esketamine is preferred depends mainly on country-specific regulations. When comparing the two, consideration of different dosing requirements is important. As shown in a study on analgesia in HEMS in Switzerland, ketamine was preferably used by anaesthetists . The high proportion of Austrian emergency physicians also being anaesthetists also explains the rather high rate of esketamine use in this study. In detail, the presented data were able to show high use of opioids over all injury localizations and the predominant use of esketamine in injuries affecting the upper and lower limbs including the pelvis. Fortunately, the administration of these potent analgesics is not limited to physicians, at least in some countries. Albeit median doses are somewhat higher in this physician-staffed service, paramedics can effectively and safely administer opioids and ketamine [8, 23,24,25,26,27]. Furthermore, dose differences are not only present inter- but also intra-professionally as demonstrated by a study from a physician-staffed EMS in Germany, which showed differences in pain treatment between surgeons and anaesthesiologists, particularly regarding opioids . Ketamine has been described as being safe and effective alone – even as effective as an alternative opioid – and also as being able to reduce opioid requirements when used in combination with opioids [26, 29, 30]. After opioids or esketamine administered alone, the by far most commonly administered combination therapy in the presented study was an opioid with esketamine, followed by a combination of an opioid with metamizole.
Adequacy and application safety of potent analgesics for injured patients during HEMS operations
Moderate to severe pain is a frequent finding in the prehospital care of emergency patients [8, 17, 31]. So is the rate of inadequate pain treatment, also described as oligoanalgesia (18–58%) [4,5,6, 24].
While the absence of analgesic administration as well as a higher NACA Score and NRS on site have unsurprisingly been described as risk factors for insufficient pain management, the same is unexpectedly also true of treatment by a female physician . Although perceived oligoanalgesia rates were the same, emergency physicians improved quality of analgesia by providing a substantially higher NRS reduction than did paramedics in a study from Switzerland . As higher doses of fentanyl administered in a paramedic setting have been shown to relieve pain better , the observed benefits might be due to deliberately increased dosages in physician-staffed settings, as also seen in this study. Ketamine has been shown to be safe, when administered alone or in combination with opioids, with no loss of consciousness, oxygen desaturation or clinically significant emergence reactions occurring [7, 27, 30]. Ketamine alone seems to have fewer side-effects than morphine alone, but the combination of both has more side-effects than morphine alone . Albeit a commonly used combination therapy, the administration of ketamine with morphine has also not been recommended because of uncertainties regarding safety [32, 33]. Adverse events due to analgesic medications are not easy to discriminate in an emergency and sometimes austere situation. With regard to potent analgesics as in opioids or esketamine, the most feared and clinically important side-effect is certainly a possible respiratory depression. Comparison of the need for additional mechanical ventilation during transport as well as clinical scores (MEES), surrogates for sufficient respiration (SpO2, respiratory rate) and levels of pain on arrival of the emergency physician and at the time of handover in hospital led us to conclude that the analgesics administered in this study were safe and adequate. The percentage of patients suffering from moderate to severe pain unmistakably decreased from over 87% to under 5%, further justifying liberal use of potent analgesics. Interestingly, while no gender differences were recorded with respect to initially moderate to severe pain, females more often still suffered from moderate to severe pain on arrival in hospital. Documented injury severity was lower in females and, while median analgesic dosages were comparable, decreased opioid but increased esketamine administration was recorded in female adults. Reasons for this difference cannot be derived from the presented data, but this finding stands in contrast to the existing literature, where largely no gender difference or even a female predominance in pain relief is described [2, 4,5,6, 18].
Not previously described is the fact that 10% of the described HEMS missions were conducted without any technical monitoring despite the overwhelming use of opioids and esketamine. These special cases were particularly young, orientated men involved in mountain accidents mainly in winter and suffering from severe pain from fractures to the upper or lower limbs. Obviously, this practice is not uncommon and emergency physicians were not discouraged from administering these potent analgesics in order to relieve severe pain despite the non-availability or cold-related failure of adequate technical monitoring equipment.
Although handwritten report forms were primarily documented prospectively and transferred to the digital database in a timely manner and by the emergency physician himself, poor documentation quality is not uncommon in emergency prehospital settings [23, 34]. Errors occurring during data transfer might have additionally contributed to this problem. Accurate documentation has been proposed as a quality indicator of physician staffed emergency medical service  but the mean proportion of completely documented cases often remains low, as seen in a recent Nordic study on HEMS . Comparing to proportions of 25–91% reported by them, merely 9–10% of all cases in this study were completely documented, including MEES, SpO2-values, respiratory rates and pain levels from initial on-site evaluation and hospital admission. A reporting bias can therefore not be excluded. Furthermore, pain levels were documented with an NRS-guided scale and not with exact numerical documentation. Detailed analysis of pain reduction (e.g. NRS reduction) was therefore not possible. Furthermore, data analysis in general was conducted retrospectively.