Epidemiology and survival outcomes of out-of-hospital cardiac arrest following volatile substance use in Queensland, Australia.

INTRODUCTION: The deliberate inhalation of volatile substances for their psychotropic properties is a recognised public health issue that can precipitate sudden death. This study aimed to describe the epidemiological characteristics and survival outcomes of patients with out-of-hospital cardiac arrests following volatile substance use. METHODS: We conducted a retrospective cohort analysis of all out-of-hospital cardiac arrest attended by the Queensland Ambulance Service over a ten-year period (2012-2021). Incidents were extracted from the Queensland Ambulance Service cardiac arrest registry, which collects clinical information using the Utstein-style guidelines and linked hospital data. RESULTS: During the study period, 52,102 out-of-hospital cardiac arrests were attended, with 22 (0.04%) occurring following volatile substance use. The incidence rate was 0.04 per 100,000 population, with no temporal trends identified. The most commonly used product was deodorant cans (19/22), followed by butane canisters (2/22), and nitrous oxide canisters (1/22). The median age of patients was 15 years (interquartile range 13-23), with 14/22 male and 8/22 Indigenous Australians. Overall, 16/22 patients received a resuscitation attempt by paramedics. Of these, 12/16 were bystander witnessed, 10/16 presented in an initial shockable rhythm, and 9/16 received bystander chest compressions. The rates of event survival, survival to hospital discharge, and survival with good neurological outcome (Cerebral Performance Category 1-2) were 69% (11/16, 95% CI 41-89%), 38% (6/16, 95% CI 15-65%) and 31% (5/16, 11-59%), respectively. Eight patients in the paramedic-treated cohort that used hydrocarbon-based products were administered epinephrine during resuscitation. Of these, none subsequently survived to hospital discharge. In contrast, all six patients that did not receive epinephrine survived to hospital discharge, with 5/6 having a good neurological outcome. CONCLUSION: Out-of-hospital cardiac arrest following volatile substance use is rare and associated with relatively favourable survival rates. Patients were predominately aged in their adolescence with Indigenous Australians disproportionately represented.

Epidemiology of open limb fractures attended by ambulance clinicians in the out-of-hospital setting: A retrospective analysis.

BACKGROUND: Open limb fractures are a time-critical orthopaedic emergency that present to jurisdictional ambulance services. This study describes the demographic characteristics and epidemiological profile of these patients METHODS: We undertook a retrospective analysis of all patients that presented to Queensland Ambulance Service with an open limb fracture (fracture to the humerus, radius/ulna, tibia/fibula or femur) over a two-year period (January 2018 - December 2019). RESULTS: Overall, 1020 patients were included. Patients were mainly male (65.9%) and middle-aged (age 41 years, IQR 22-59). Fractures predominately occurred in the lower extremities (64.9%) with transport crashes the primary mechanism of injury (47.8%). The location of the fracture varied depending on the cause of injury, with femur fractures associated with motorcycle crashes, and fractures to the radius/ulna attributed to falls of greater than one metre (p = 0.001). The median prehospital episode of care was 83 min (IQR 62-144) with aeromedical air ambulance involvement and the attendance of a critical care paramedic or emergency physician, both independent factors that increased this time interval. CONCLUSION: Open limb fractures are a relatively infrequent injury presentation encountered by ambulance clinicians. The characteristics of these patients is consistent with previously described national and international out-of-hospital trauma cohorts.

Epidemiology of out-of-hospital cardiac arrests that occur secondary to chemical asphyxiants: A retrospective series.

AIM: To determine the epidemiological characteristics, temporal trends and survival outcomes of OHCAs precipitated by chemical asphyxiation. METHODS: We conducted a retrospective cohort analysis of OHCAs attended by paramedics in Queensland, Australia between 2011 and 2020. Patients were classified into two groups depending on the asphyxiating agent involved; simple (argon, carbon dioxide, helium, liquified petroleum gas, nitrogen) and systemic (carbon monoxide, cyanides, hydrogen sulfide, methemoglobin-inducing substances, smoke inhalation). Incidence rates, characteristics and outcomes were described for the entire cohort and independently for each group, with the groups then compared. Temporal trends of asphyxiant utilisation were also described. RESULTS: During the study period, 50,669 OHCAs were attended, with 551 (1.1%) attributable to chemical asphyxiation. The incidence rate was 1.1 per 100,000 population with no significant temporal changes. Suspected suicide was the primary cause of exposure (-95.8%), with systemic asphyixants the dominant agent reported in comparison to simple agents (66.4% vs 33.6%). Over the 10-year period, events precipitated by carbon monoxide decreased by 26.2% (p for trend < 0.001), helium remained unchanged (p for trend = 0.302) and incidents involving nitrogen increased by 28.7% (p for trend < 0.001). Overall, 14.2% (78/551) of the study cohort received a resuscitation attempt by paramedics with 6.4% of these incidents witnessed and 2.6% involving patients presenting in a shockable rhythm. Survival rates were low, with 6.4% surviving the index event, and 1.3% surviving to hospital discharge with a normal neurocognitive function. CONCLUSION: OHCA precipitated by chemical asphyxiation is relatively infrequent and associated with poor survival outcomes.

Time to amiodarone administration and survival outcomes in refractory ventricular fibrillation.

OBJECTIVE: International guidelines recommend amiodarone for out-of-hospital cardiac arrest (OHCA) in refractory ventricular fibrillation (VF). While early appropriate interventions have been shown to improve OHCA survival, the association between time to amiodarone and survival remains to be established. METHODS: Included were adult OHCA in refractory VF, between January 2015 and December 2019, who received a resuscitation attempt with amiodarone from Queensland Ambulance Service paramedics. Patient characteristics and survival outcomes were described. Factors associated with survival were investigated, with a focus on time from arrest to amiodarone administration. Optimal time window for amiodarone administration was determined, and factors influencing whether amiodarone was given within the optimal time window were examined. RESULTS: A total of 502 patients were included. The average (range) time from arrest to amiodarone was 25 (4-83) min. Time to amiodarone was negatively associated with survival (adjusted odds ratio 0.93 for event survival; 95% confidence interval 0.89-0.97). The optimal time window for amiodarone was within 23 min following arrest. Patients receiving amiodarone within the optimal time had significantly better survival than those receiving it outside this window (event survival 38.3% vs 20.6%, P < 0.001; discharge survival 25.5% vs 9.7%, P < 0.001; 30-day survival 25.1% vs 9.7%, P < 0.001). Paramedic response time (adjusted odds ratio 0.96; 95% confidence interval 0.92-0.99) and time from arrest to intravenous access (0.71; 0.67-0.76) were independent factors determining whether patients received amiodarone within the optimal time. CONCLUSIONS: Earlier amiodarone administration was associated with improved survival. Strategies aimed at reducing delay to amiodarone administration have the potential to improve outcome.

Epidemiology of Oxytocin Administration in Out-of-Hospital Births Attended by Paramedics.

AIM: Primary postpartum hemorrhage (PPH) is a life-threatening obstetric emergency that can be mitigated through the administration of a uterotonic to actively manage the third stage of labor. This study describes the prehospital administration of oxytocin by paramedics following attendance of out-of-hospital (OOH) births. METHODS: A retrospective analysis was undertaken of all OOH births between the 1st January 2018 and 31st December 2018 attended by the Queensland Ambulance Service. The demographic and epidemiological characteristics of patients that were administered oxytocin and the occurrence of adverse side effects were described. RESULTS: In total, 350 OOH births were included in this study with the majority involving multigravidas women (94.3%) and all but two involving singleton pregnancies. Oxytocin was administered following 222 births (63.4%), while 67 patients (19.1%) declined administration preferring a physiological third stage of labor, and in 61 cases (17.4%) oxytocin was withheld by the attending paramedic. There were no documented adverse events or side effects following administration. Oxytocin administration occurred on average 14 minutes (interquartile range 9-25) following the time of birth. The median time from oxytocin administration to placenta delivery was 10 minutes (interquartile range 5-22). CONCLUSION: Oxytocin is well accepted and safe treatment adjunct for the management of the third stage of labor in OOH births and should be considered for routine practice by other emergency medical services.

Survival in Patients with Paramedic-Identified ST-Segment Elevation Myocardial Infarction.

BACKGROUND: Field identification and treatment of ST-segment elevation myocardial infarction (STEMI) by paramedics is an important component of care for these patients. There is a paucity of studies in the setting of paramedic-identified STEMI. This study investigated mortality and factors associated with mortality in a large state-wide prehospital STEMI sample. Methods: Included were adult STEMI patients identified and treated with reperfusion therapy by paramedics in the field between January 2016 and December 2018 in Queensland, Australia. 30-day and one-year all-cause mortality was compared between two prehospital reperfusion pathways: prehospital fibrinolysis versus direct referral to a hospital for primary percutaneous coronary intervention (direct percutaneous coronary intervention [PCI] referral). For prehospital fibrinolysis patients, factors associated with failed fibrinolysis were investigated. For direct PCI referral patients, factors associated with mortality were examined. Results: The 30-day mortality was 2.2% for prehospital fibrinolysis group and 1.8% for direct PCI referral group (p = 0.661). One-year mortality for the two groups was 2.7% and 3.2%, respectively (p = 0.732). Failed prehospital fibrinolysis was observed in 20.1% of patients receiving this therapy, with male gender and history of heart failure being predictors. For direct PCI referral group, low left ventricular ejection fraction (LVEF) on admission and cardiogenic shock prior to PCI were predictors of both 30-day and one-year mortality. Aboriginal and Torres Strait Islander status, and impaired kidney function on admission, were associated with one-year but not 30-day mortality. Being overweight was associated with lower 30-day mortality. Conclusions: Mortality in STEMI patients identified and treated by paramedics was low, and the prehospital fibrinolysis treatment pathway was effective with a mortality rate comparable to that of patients undergoing primary PCI. Key words: prehospital; Queensland; cardiac reperfusion; STEMI.

Prehospital study of survival outcomes from out-of-hospital cardiac arrest in ST-elevation myocardial infarction in Queensland, Australia (the PRAISE study).

AIM: Patients that experience an out-of-hospital cardiac arrest in the context of a paramedic-identified ST-segment elevation myocardial infarction are a unique cohort. This study identifies the survival outcomes and determinants of survival in these patients. METHODS: A retrospective analysis was undertaken of all patients, attended between 1 January 2013 and 31 December 2017 by the Queensland Ambulance Service, who had a ST-segment elevation myocardial infarction identified by the attending paramedic prior to deterioration into out-of-hospital cardiac arrest. We described the 'survived event' and 'survived to discharge' outcomes of patients and performed univariate analysis and multivariate logistic regression to identify factors associated with survival. RESULTS: In total, 287 patients were included. Overall, high rates of survival were reported, with 77% of patients surviving the initial out-of-hospital cardiac arrest event and 75% surviving to discharge. Predictors of event survival were the presence of an initial shockable rhythm (adjusted odds ratio 8.60, 95% confidence interval (CI) 4.16-17.76; P < 0.001) and the administration of prehospital medication for subsequent primary percutaneous coronary intervention (adjusted odds ratio 2.54, 95% CI 1.17-5.50; P = 0.020). These factors were also found to be associated with survival to hospital discharge, increasing the odds of survival by 13.74 (95% CI 6.02-31.32; P < 0.001) and 6.96 (95% CI 2.50-19.41; P < 0.001) times, respectively. The administration of prehospital fibrinolytic medication was also associated with survival in a subgroup analysis. CONCLUSION: This subset of out-of-hospital cardiac arrest patients was found to be highly salvageable and responsive to resuscitative measures, having arrested in the presence of paramedics and presented with an identified reversible cause.

Insights into the epidemiology of cardiopulmonary resuscitation-induced consciousness in out-of-hospital cardiac arrest.

OBJECTIVES: To describe the characteristics and outcomes of cardiopulmonary resuscitation (CPR)-induced consciousness patients from a large database of out-of-hospital cardiac arrest (OHCA). METHODS: Included were adult patients, attended between January 2007 and December 2018 by the Queensland Ambulance Service, where resuscitation was attempted by paramedics. Manual review of records was undertaken to identify CPR-induced consciousness cases. Patients exhibiting purposeful limb/body movement during CPR, with or without displaying other signs, were considered to be CPR-induced consciousness. Characteristics and outcomes of CPR-induced consciousness patients were compared to those without CPR-induced consciousness. RESULTS: A total of 23 011 OHCA patients were included; of these, 52 (0.23%) were CPR-induced consciousness. This translates into an incidence rate of 2.3 cases per 1000 adult resuscitation attempts over 12 years. Combativeness/agitation was the most common sign of CPR-induced consciousness, described in 34.6% (18/52) of patients. CPR-induced consciousness patients had numerically higher rates of return of spontaneous circulation on hospital arrival (51.9% vs 28.6%), discharge survival (46.2% vs 15.1%) and 30-day survival (46.2% vs 14.7%), than those without CPR-induced consciousness; however, CPR-induced consciousness was not found to be an independent predictor of survival. Higher proportions of CPR-induced consciousness patients had arrest witnessed by paramedics, occurring in public places, of cardiac aetiology and initial shockable rhythm, than patients without CPR-induced consciousness. CONCLUSIONS: CPR-induced consciousness in OHCA appears to be associated with higher survival rates. Standardised guidelines on recognition and management of CPR-induced consciousness remain to be established.

Surviving out-of-hospital cardiac arrest: The important role of bystander interventions.

BACKGROUND: Substantial variations exist in relation to the characteristics and outcomes of out-of-hospital cardiac arrest (OHCA). As such, an understanding of region-specific factors is essential for informing strategies to improve OHCA survival. METHODS: Analysis of a large state-wide OHCA database of the Queensland Ambulance Service, Australia. Adult patients, attended by paramedics between January 2000 and December 2018 for OHCA of medical origin, where the arrest was not witnessed by paramedics, and resuscitation was attempted, were included. Factors associated with survival were investigated. The number needed to treat (NNT) for bystander interventions was estimated. RESULTS: Across a total of 23,510 patients, event survival, survival to discharge and 30-day survival was 22.6%, 11.9% and 11.5%, respectively. The corresponding figures for the Utstein patient group (initial shockable rhythm, bystander-witnessed) were 38.9%, 27.2% and 26.3%, respectively. Bystander cardiopulmonary resuscitation (CPR) and defibrillation substantially improved the likelihood of survival. The NNT for bystander CPR was 41, 63 and 64 for event survival, survival to discharge, and 30-day survival, respectively. The NNT for bystander defibrillation for these survival outcomes was 10, 14 and 14, respectively. CONCLUSIONS: Bystander interventions are critical for OHCA survival. Effort should be invested in strategies to improve the uptake of these interventions.

Prehospital study of survival outcomes from out-of-hospital cardiac arrest in ST-elevation myocardial infarction in Queensland, Australia (the PRAISE study).

AIM: Patients that experience an out-of-hospital cardiac arrest in the context of a paramedic-identified ST-segment elevation myocardial infarction are a unique cohort. This study identifies the survival outcomes and determinants of survival in these patients. METHODS: A retrospective analysis was undertaken of all patients, attended between 1 January 2013 and 31 December 2017 by the Queensland Ambulance Service, who had a ST-segment elevation myocardial infarction identified by the attending paramedic prior to deterioration into out-of-hospital cardiac arrest. We described the 'survived event' and 'survived to discharge' outcomes of patients and performed univariate analysis and multivariate logistic regression to identify factors associated with survival. RESULTS: In total, 287 patients were included. Overall, high rates of survival were reported, with 77% of patients surviving the initial out-of-hospital cardiac arrest event and 75% surviving to discharge. Predictors of event survival were the presence of an initial shockable rhythm (adjusted odds ratio 8.60, 95% confidence interval (CI) 4.16-17.76; P < 0.001) and the administration of prehospital medication for subsequent primary percutaneous coronary intervention (adjusted odds ratio 2.54, 95% CI 1.17-5.50; P = 0.020). These factors were also found to be associated with survival to hospital discharge, increasing the odds of survival by 13.74 (95% CI 6.02-31.32; P < 0.001) and 6.96 (95% CI 2.50-19.41; P < 0.001) times, respectively. The administration of prehospital fibrinolytic medication was also associated with survival in a subgroup analysis. CONCLUSION: This subset of out-of-hospital cardiac arrest patients was found to be highly salvageable and responsive to resuscitative measures, having arrested in the presence of paramedics and presented with an identified reversible cause.

Prehospital ST-Segment Elevation Myocardial Infarction (STEMI) in Queensland, Australia: Findings from 11 Years of the Statewide Prehospital Reperfusion Strategy.

Background: Field identification and treatment of ST-segment elevation myocardial infarction (STEMI) by paramedics is an important component of the continuum of care for these patients. This study described real-world clinical practice in prehospital management of STEMI patients in Queensland, Australia. Methods: Retrospective analysis of data sourced from the STEMI database of the Queensland Ambulance Service, Australia. Adult STEMI patients identified by paramedics between February 2008 and December 2018 in Queensland were included. Key aspects of prehospital STEMI care were described. Clinically-important time intervals from symptom onset to reperfusion were reported. Results: A total of 8,388 patients were included. The proportion of patients receiving prehospital reperfusion treatment has improved markedly, increasing from 34% in 2008 to 65% in 2018 (p < 0.001). Direct referral of patients to a hospital for primary percutaneous coronary intervention (pPCI), and administration of preparatory antiplatelet and anticoagulant medications, was the main reperfusion treatment pathway, accounting for 75% of patients receiving reperfusion treatment. Time from paramedic arrival at scene to first 12-lead electrocardiogram has significantly reduced, from 11 minutes in 2008 to 6 minutes from 2012 onwards (p < 0.001). Median (interquartile range, IQR) time from prehospital STEMI identification to reperfusion was 88 (74-103) minutes for patients referred by paramedics to a hospital for pPCI. Fifty-five percent of patients who underwent pPCI achieved time from STEMI identification to reperfusion within 90 minutes. For patients receiving prehospital fibrinolysis, median (IQR) time from STEMI identification to administration of a fibrinolytic agent was 21 (12-33) minutes. Conclusion: The implementation of a statewide prehospital reperfusion strategy has markedly improved the rate of prehospital reperfusion treatment and key time metrics. Ongoing quality improvement efforts are required to further reduce delays in reperfusion.