Comparison of preoxygenation using a tight facemask, humidified high-flow nasal oxygen and a standard nasal cannula - a volunteer, randomised, crossover study.

BACKGROUND: Preoxygenation before anaesthesia induction is routinely performed via a tight-fitting facemask or humidified high-flow nasal oxygen. We hypothesised that effective preoxygenation, assessed by end-tidal oxygen (EtO 2 ) levels, can also be performed via a standard nasal cannula. OBJECTIVE: This study compared the efficacy of preoxygenation between a traditional facemask, humidified high-flow nasal oxygen and a standard nasal cannula. DESIGN: A volunteer, randomised, crossover study. SETTING: Karolinska University Hospital, Stockholm. The study was conducted between 2 May and 31 May 2023. PARTICIPANTS: Twenty cardiopulmonary healthy volunteers aged 25-65 years with a BMI <30. INTERVENTIONS: Preoxygenation using a traditional facemask, humidified high-flow nasal oxygen and standard nasal cannula. Volunteers were preoxygenated with all three methods, at various flow rates (10-50 l min -1 ), with open and closed mouths and during vital capacity manoeuvres. MAIN OUTCOME MEASURES: The study's primary outcome compared the efficacy after 3 min of preoxygenation, assessed by EtO 2 levels, between the three methods and various flow rates of preoxygenation. RESULTS: Three methods generated higher EtO 2 levels than others: (i) facemask preoxygenation using normal breathing, (ii) humidified high-flow nasal oxygen, closed-mouth breathing, at 50 l min -1 and (iii) standard nasal cannula, closed-mouth breathing, at 50 l min -1 , and expressed as means (SD): 90% (3), 90% (6) and 88% (5), respectively. Preoxygenation efficacy was greater via the bi-nasal cannulae using closed vs. open mouth breathing as well as with 3 min of normal breathing vs. eight vital capacity breaths. Preoxygenation with a facemask and humidified high-flow nasal oxygen was more comfortable than a standard nasal cannula. CONCLUSION: The efficacy of preoxygenation using a standard nasal cannula at high flow rates is no different to clinically used methods today. The standard nasal cannula provides less comfort but is highly effective and could be an option when alternative methods are unavailable. TRIAL REGISTRATION: Clinicaltrials.gov, NCT05839665.

Implementation of an extracorporeal resuscitation (ECPR) program for out-of-hospital cardiac arrest in Stockholm, Sweden: Feasibility, safety, and outcome.

Background: The aim of this study was to evaluate the implementation of a novel extra corporeal cardiopulmonary (ECPR) program in the greater Stockholm area with focus on feasibility, safety aspects and clinical outcomes. Methods: Prospective observational study of ECPR program including patients with OHCA from January 2020 to December 2022, fulfilling ECPR criteria: age 18-65 years, initial shockable rhythm or pulseless electrical activity, witnessed arrest, bystander cardiopulmonary resuscitation and refractory arrest after three cycles of advance cardiac life support. The predefined time threshold from collapse to extracorporeal membrane oxygenation (ECMO) initiation was set at 60 min. Results: We included 95 patients. Of these, 22/95 (23%) had return of spontaneous circulation before ECMO initiation, 39/95 (41%) were excluded for ECMO and 34/95 (36%) had ECMO initiated out of which 23 patients were admitted alive to the ICU. ECMO-initiation within 60 min was met in 9%. In 6 patients vascular access was complicated, 2 patients had severe bleeding at access site requiring intervention. Survival to discharge among all cases was 25% (24/95). Among patients admitted to ICU on ECMO 39% (9/23) survived to discharge, of these 78% had cerebral performance category scale score 1-2 within 12 months. 8 out of 9 survivors had time from OHCA to ECMO-initiation >60 min. Conclusion: The implementation of an ECPR protocol was feasible without any major, unexpected safety aspects but did not meet the intended target time intervals. Despite this, survival rates were similar to previous studies although most survivors had >60 min to ECMO-initiation.

Pre-oxygenation using high-flow nasal oxygen versus tight facemask in trauma patients undergoing emergency anaesthesia.

BACKGROUND: Patients suffering from major traumatic injuries frequently require emergency anaesthesia. Due to often compromised physiology and the time-sensitive management, trauma patients may be more prone to desaturate during induction of anaesthesia. We hypothesised that pre-oxygenation using high-flow nasal oxygen would decrease the risk of desaturation during induction of anaesthesia in trauma patients and the study therefore aimed to compare the frequency of desaturation when pre-oxygenation was performed with high-flow nasal oxygen or a traditional facemask. METHODS: This exploratory, prospective, before-and-after study was conducted at the Karolinska University Hospital, Sweden. Adult (≥18 years of age) patients suffering major traumatic injuries needing emergency anaesthesia were included around the clock. Patients were pre-oxygenated using a tight-fitting facemask during the first nine months of enrollment. High-flow nasal oxygen was then introduced as a method for pre-oxygenation of trauma patients. The primary outcome was the proportion of patients desaturating <93% during induction of anaesthesia, assessed from the start of pre-oxygenation until one minute after intubation. Secondary outcomes included perceived difficulty of pre-oxygenation among anaesthetists (assessed on a scale between 1 and 10) and safety outcomes, such as incidence of regurgitations and intracranial gas (assessed radiologically). RESULTS: Data from 96 patients were analysed. Facemask pre-oxygenation was performed in 66 patients, while 30 patients were pre-oxygenated with high-flow nasal oxygen. The most frequent trauma mechanisms were stabbing injuries (n = 34 (35%)) and fall injuries (n = 21 (22%)). There were no differences in patient characteristics between the groups. Eight (12%) versus three (10%) patients desaturated <93% in the facemask and high-flow nasal oxygen group respectively, OR 0.81 (95% CI 0.20-3.28), p = .76. Anaesthetists assessed pre-oxygenation using high-flow nasal oxygen as easier compared to facemask pre-oxygenation. No patient in any group showed signs of regurgitation. Among patients with facial or skull fractures requiring anaesthesia before radiology was performed, intracranial gas was seen in four (40%) patients pre-oxygenated with a facemask and in no patient pre-oxygenated with HFNO (p = .23). CONCLUSION: In this prospective study investigating trauma patients undergoing emergency anaesthesia, we could not see any difference in the number of patients desaturating when pre-oxygenation was performed with high-flow nasal oxygen compared to a tight-fitting facemask. Pre-oxygenation using high-flow nasal oxygen was assessed as easier compared to facemask pre-oxygenation.

Pre-oxygenation using high-flow nasal oxygen in parturients undergoing caesarean section in general anaesthesia: A prospective, multi-centre, pilot study.

BACKGROUND: Parturients undergoing caesarean section in general anaesthesia have an increased risk of desaturating during anaesthesia induction. Pre- and peri-oxygenation with high-flow nasal oxygen prolong the safe apnoea time but data on parturients undergoing caesarean section under general anaesthesia are limited. This pilot study aimed to investigate the clinical effects and frequency of desaturation in parturients undergoing caesarean section in general anaesthesia pre- and peri-oxygenated with high-flow nasal oxygen and compare this to traditional pre-oxygenation using a facemask. METHODS: In this prospective, non-randomised, multi-centre study we included pregnant women with a gestational age ≥30 weeks undergoing caesarean section under general anaesthesia. All parturients were asked to participate in the intervention group consisting of pre-oxygenation using high-flow nasal oxygen. Parturients declining participation were pre-oxygenated with a traditional facemask. Primary outcome was the proportion of parturients desaturating below 93% from start of pre-oxygenation until 1 min after tracheal intubation. Secondary outcomes investigated end-tidal oxygen concentrations after tracheal intubation and the proportion of parturients with signs of regurgitation. RESULTS: A total of 34 parturients were included, 25 pre- and peri-oxygenated with high-flow nasal oxygen and 9 pre-oxygenated with facemask. No difference in patient or airway characteristics could be seen except for a higher BMI in the high-flow nasal oxygen group (31.4 kg m-2 [4.7] vs. 27.7 kg m-2 [3.1]; p = .034). No woman in any of the two groups desaturated below 93%. The lowest peripheral oxygen saturation observed, in any parturient, was 97%. There was no difference detected in end-tidal oxygen concentration after tracheal intubation, 87% (6) in the high-flow nasal oxygen group vs 80% (15) in the facemask group (p = .308). No signs of regurgitation, in any parturient, were seen. CONCLUSION: Pre- and peri-oxygenation with high-flow nasal oxygen maintain adequate oxygen saturation levels during induction of anaesthesia also in parturients. Regurgitation of gastric content did not occur in any parturient and no other safety concerns were observed in this pilot study.

Characteristics and outcome of traumatic cardiac arrest at a level 1 trauma centre over 10 years in Sweden.

BACKGROUND: Historically, resuscitation in traumatic cardiac arrest (TCA) has been deemed futile. However, recent literature reports improved but varying survival. Current European guidelines emphasise the addressing of reversible aetiologies in TCA and propose that a resuscitative thoracotomy may be performed within 15 min from last sign of life. To improve clinician understanding of which patients benefit from resuscitative efforts we aimed to describe the characteristics and 30-day survival for traumatic cardiac arrest at a Swedish trauma centre with a particular focus on resuscitative thoracotomy. METHODS: Retrospective cohort study of adult patients (≥ 15 years) with TCA managed at Karolinska University Hospital Solna between 2011 and 2020. Trauma demographics, intra-arrest factors, lab values and procedures were compared between survivors and non-survivors. RESULTS: Among the 284 included patients the median age was 38 years, 82.2% were male and 60.5% were previously healthy. Blunt trauma was the dominant injury in 64.8% and median Injury Severity Score (ISS) was 38. For patients with a documented arrest rhythm, asystole was recorded in 39.2%, pulseless electric activity in 24.8% and a shockable rhythm in 6.8%. Thirty patients (10.6%) survived to 30 days with a Glasgow Outcome Scale score of 3 (n = 23) or 4 (n = 7). The most common causes of death were haemorrhagic shock (50.0%) and traumatic brain injury (25.5%). Survivors had a lower ISS (P < 0.001), more often had reactive pupils (P < 0.001) and a shockable rhythm (P = 0.04). In the subset of prehospital TCA, survivors less frequently received adrenaline (epinephrine) (P < 0.001) and in lower amounts (P = 0.02). Of patients that underwent resuscitative thoracotomy (n = 101), survivors (n = 12) had a shorter median time from last sign of life to thoracotomy (P = 0.03), however in four of these survivors the time exceeded 15 min. CONCLUSION: Survival after TCA is possible. Determining futility in TCA is difficult and this study demonstrates survivors outside of recent guidelines.

Stroke after cardiac surgery--hemispheric distribution and survival.

OBJECTIVES: Stroke following cardiac surgery may occur either in association with surgery (early) or occur postoperatively (delayed). The hemispheric distribution of lesions may provide information about embolic routes, which was analyzed here. DESIGN: In 10,809 patients undergoing cardiac surgery, early (n = 223) and delayed stroke (n = 116) were explored. Symptoms and computed tomography findings were evaluated to categorize hemispheric distributions. This was compared with pre- and intra-operative characteristics and survival, using logistic regression and Kaplan-Meier statistics. RESULTS: Early stroke had preponderance for the right rather than the left hemisphere (P = 0.009), whereas delayed stroke had a uniform distribution. Several intraoperative variables predicted the development of bilateral stroke compared with its unilateral counterpart. At multivariable analysis, the use of tranexamic acid was associated with bilateral stroke (P = 0.017), but was also associated with right rather than left-hemispheric stroke (P = 0.001). Bilateral lesions dramatically impaired survival versus those with unilateral lesions (P < 0.001). There was no survival difference between left and right-hemispheric stroke. CONCLUSIONS: When stroke, after cardiac surgery, is subdivided into early and delayed forms, it becomes evident that early, but not delayed stroke, demonstrates a hemispheric side difference. The preponderance for right-hemispheric lesions may indicate embolic mechanisms routed via the brachiocephalic trunk.

Early and delayed stroke after coronary surgery - an analysis of risk factors and the impact on short- and long-term survival.

OBJECTIVE: Stroke is a serious complication to cardiac surgery, and is generally considered as a uniform disease regardless of its temporal relationship to surgery. Our hypothesis suggests that stroke, in association with surgery, reflects other characteristics than stroke occurring with a free interval. This issue was here explored for risk factors and survival effects. METHODS: Data were collected from 7839 procedures of isolated coronary artery bypass grafting (CABG), 297 off-pump CABG, and 986 combined CABG and valve procedures. Records of patients with any signs of neurological complications were reviewed to extract 149 subjects with stroke at extubation (early, 1.6%) versus 99 patients having a free interval (delayed, 1.1%). Survival data were complete, with a median follow-up time of 9.3 years (maximum 16.3 years). Independent risk factors were analyzed by logistic regression and survival by Cox regression. RESULTS: Risk factors for early stroke were advanced age, high preoperative creatinine level, extent of aortic atherosclerosis, and long cardiopulmonary bypass time (all P<0.001). Factors associated with delayed stroke were female gender (P<0.001), unstable angina (P=0.003), previous cerebrovascular disease (P=0.009), inotropic support requirement (P<0.001), and postoperative atrial fibrillation (P<0.001). Stroke explained mortality not only in the early postoperative period (P<0.001), but also at long-term follow-up (P<0.001). Early and delayed stroke were associated with mortality hazard ratios (HRs) of 1.44 and 1.85 (P=0.008, P<0.001), respectively. However, for patients surviving their first postoperative year, early stroke did not influence long-term mortality (HR 1.07, P=0.695). This was in contrast to delayed stroke (HR 1.71, P=0.001). CONCLUSIONS: Early and delayed stroke differed in their related risk factors. The influence of stroke on short-term mortality was obvious and devastating. Mortality in association with early stroke mainly presented itself in the acute period, whereas for delayed stroke survival continued to be impaired also in the long-term perspective. Our report emphasizes that early and delayed stroke should be considered as two separate entities.

Size distribution of embolic material produced at aortic cross-clamp manipulation.

OBJECTIVES: The association between aortic atherosclerosis and neurological damage during cardiac surgery is well recognized. The purpose was here to analyze the size distribution of particles produced at cross-clamp manipulation of the ascending aorta. DESIGN: A human cadaveric aortic perfusion model of retrograde design was applied (n=27). With this model, washout samples were collected from the pressurized ascending aorta during cross clamp manipulation. Before the experiment, the aorta was flushed to remove debris and with a baseline sample collected. The cross-clamp was opened to collect ten repeated aliquots with dislodged particles. Collected washout samples were evaluated by digital image analysis and microscopy. RESULTS: Cross-clamping produced a significant output of particles, which was seen for size intervals of 1 mm and smaller (p=0.002 to p=0.022). In all size intervals the particle output correlated with the degree of overall aortic calcification (p=0.002 to p=0.025). The model generated substantially more small-size particles than large debris (p<0.010). CONCLUSIONS: Aortic clamping was here verified to dislodge aortic debris which correlated with the degree of observed calcification. Macroscopic particles were few. In contrast, cross-clamping produced substantial numbers of small-size particles. These findings emphasize microembolic risks associated with cross-clamping of atherosclerotic vessels.

Cannulation of the noncalcified aorta generates particles of microembolic nature: an experimental study using pig aorta.

BACKGROUND AND AIM OF THE STUDY: Aortic cannulation during cardiac surgery is a potential etiological factor for perioperative stroke. Cannulae may dislodge aortic-wall calcifications. In addition, the sharp edge of the cannula-tip may shear off vessel-wall tissue, which can be expelled into the lumen. This hypothesis concerning source of emboli was tested in a noncalcified aortic perfusion model. METHODS: Pig aortas were pressurized and cannulated. Washout samples were collected before and after cannulation (n = 40). Particles were deposited onto a 10-microm filter and evaluated by microscopy and digital image analysis. RESULTS: A higher incidence of particles generated by cannulation was noted as compared to before the maneuver (p < 0.001). This increase included small (<0.1 mm, p < 0.001) and intermediate-size particles (0.1-0.5 mm, p < 0.001). Particles above 0.5 mm were few and were not associated with cannulation. CONCLUSIONS: Cannulation was a source of embolic material in the noncalcified aortic model. However, these particles were less than 0.5 mm in diameter and may contribute to neurocognitive decline after cardiac surgery.

Cerebrovascular accidents after cardiac surgery: an analysis of CT scans in relation to clinical symptoms.

There is a link between aortic manipulation, particle embolization, and cerebrovascular accidents (CVA) in cardiac surgery. The present aim was to study hemispheric side differences of CVA. Cardiac-surgery patients with CVA and with computer tomography (CT) performed (n = 77) were analyzed within a total group of 2641 consecutive cases. CT data were reviewed for hemispheric and vascular distribution, and compared with CVA-symptom data of immediate and delayed type. Of the included patients, 66% had positive CT. In the group of 'cardiac-type' operations (e.g., routine clamping and cannulation) and having immediate CVA, right-hemispheric lesions were more frequent than of the contra-lateral side (p = 0.005). Patients with aortic dissections had strong dominance of bilateral findings, which was different from the unilateral pattern of 'cardiac-type' operations (p = 0.001). The middle-cerebral artery territory dominated, and when involved showed a significant (p = 0.022) right-sided distribution. Both CT and clinical symptoms confirmed that CVA after cardiac surgery has a right-hemispheric predominance. These observations may imply that aortic manipulation directs embolic material towards the brachiocephalic trunk.