Admission S100B fails as neuro-marker but is a good predictor for intrahospital mortality in major trauma patients

BACKGROUND

S100 B is an extensively studied neuro-trauma marker, but its specificity and subsequently interpretation in major trauma patients might be limited, since extracerebral injuries are known to increase serum levels. Thus, we evaluated the potential role of S100B in the assessment of severe traumatic brain injury (TBI) in multiple injured patients upon emergency room (ER) admission and the first days of intensive care unit (ICU) stay.

METHODS

Retrospective study employing trauma registry data derived from a level 1 trauma center. Four cohorts of patients were grouped: isolated TBI (iTBI), polytrauma patients with TBI (PT + TBI), polytrauma patients without TBI (PT-TBI) and patients without polytrauma or TBI (control). S100B-serum levels were assessed immediately after admission in the emergency room and during the subsequent ICU stay. Values were correlated with injury severity score (ISS), Glasgow Coma Score (GCS) and in-hospital mortality.

RESULTS

780 predominantly male patients (76 %) with a median age of 48 (30-63) and a median ISS of 24 (17-30) were enrolled in the study. Admission S100B correlated with ISS and TBI severity defined by the GCS (both p < 0.0001) but not with head abbreviated injury score (AIS) (p = 0.38). Compared with survivors, non-survivors had significantly higher median S100B levels in the ER (6.14 μg/L vs. 2.06 μg/L; p < 0.0001) and at ICU-day 1 (0.69 μg/L vs. 0.17 μg/L; p < 0.0001). S100B in the ER predicted mortality with an area under curve (AUC) of 0.77 (95 % CI 0,70-0,83, p < 0.0001), vs. 0.86 at ICU-day 1 (95 % CI 0,80-0,91, p < 0.0001).

CONCLUSION

In conclusion, S100B is a valid biomarker for prediction of mortality in major trauma patients with a higher accuracy when assessed at the first day of ICU stay vs. immediately after ER admission. Since S100B did not correlate with pathologic TBI findings in multiple injured patients, it failed as predictive neuro-marker because extracerebral injuries demonstrated a higher influence on admission levels than neurotrauma. Although S100B levels are indicative for injury severity they should be interpreted with caution in polytrauma patients.

Usability and effectiveness of inhaled methoxyflurane for prehospital analgesia - a prospective, observational study

Background

Pain relief in the prehospital setting is often insufficient, as the administration of potent intravenous analgesic drugs is mostly reserved to physicians. In Australia, inhaled methoxyflurane has been in routine use by paramedics for decades, but experience in Central European countries is lacking. Thus, we aimed to assess whether user friendliness and effectiveness of inhaled methoxyflurane as sole analgesic match the specific capabilities of local ground and air-based EMS systems in Austria.

Methods

Observational study in adult trauma patients (e.g. dislocations, fracture or low back pain following minor trauma) with moderate to severe pain (numeric rating scale [NRS] ≥4). Included patients received a Penthrop® inhaler containing 3 mL of methoxyflurane (maximum use 30 min). When pain relief was considered insufficient (NRS reduction < 3 after 10 min), intravenous analgesics were administered by an emergency physician. The primary endpoint was effectiveness of methoxyflurane as sole analgesic for transport of patients. Secondary endpoints were user friendliness (EMS personell), time to pain relief, vital parameters, side effects, and satisfaction of patients.

Results

Median numeric pain rating was 8.0 (7.0–8.0) in 109 patients. Sufficient analgesia (reduction of NRS ≥3) was achieved by inhaled methoxyflurane alone in 67 patients (61%). The analgesic effect was progressively better with increasing age. Side effects were frequent (n = 58, 53%) but mild. User satisfaction was scored as very good when pain relief was sufficient, but fair in patients without benefit. Technical problems were observed in 16 cases (14.7%), mainly related to filling of the inhaler. In every fifth use, the fruity smell of methoxyflurane was experienced as unpleasant. No negative effects on vital signs were observed.

Conclusion

In prehospital use, inhaled methoxyflurane as sole analgesic is effective for transport of trauma patients (62%) with moderate to severe pain. Older patients benefit especially from inhaled methoxyflurane. Side effects are mild and vital parameters unaffected. Thus, inhaled methoxyflurane could be a valuable device for non-physician EMS personnel rescue services also in the central Europe region.

Computer tomographic assessment of gastric volume in major trauma patients: impact of pre-hospital airway management on gastric air

Background

Gastric dilation is frequently observed in trauma patients. However, little is known about average gastric volumes comprising food, fluids and air. Although literature suggests a relevant risk of gastric insufflation when endotracheal intubation (ETI) is required in the pre-hospital setting, this assumption is still unproven.

Methods

Primary whole body computed tomographic (CT) studies of 315 major trauma patients admitted to our Level 1 Trauma Centre Salzburg during a 7-year period were retrospectively assessed. Gastric volumes were calculated employing a CT volume rendering software. Patients intubated in the pre-hospital setting by emergency physicians (PHI, N = 245) were compared with spontaneously breathing patients requiring ETI immediately after arrival in the emergency room (ERI, N = 70).

Results

The median (range) total gastric content and air volume was 402 (26–2401) and 94 (0–1902) mL in PHI vs. 466 (59–1915) and 120 (1–997) mL in ERI patients (p = .59 and p = .35). PHI patients were more severely injured when compared with the ERI group (injury severity score (ISS) 33 (9–75) vs. 25 (9–75); p = .004). Mortality was higher in the PHI vs. ERI group (26.8% vs. 8.6%, p = .001). When PHI and ERI patients were matched for sex, age, body mass index and ISS (N = 50 per group), total gastric content and air volume was 496 (59–1915) and 119 (0–997) mL in the PHI vs. 429 (36–1726) and 121 (4–1191) mL in the ERI group (p = .85 and p = .98). Radiologic findings indicative for aspiration were observed in 8.1% of PHI vs. 4.3% of ERI patients (p = .31). Gastric air volume in patients who showed signs of aspiration was 194 (0–1355) mL vs. 98 (1–1902) mL in those without pulmonary CT findings (p = .08).

Conclusion

In major trauma patients, overall stomach volume deriving from food, fluids and air must be expected to be around 400–500 mL. Gastric dilation caused by air is common but not typically associated with pre-hospital airway management. The amount of air in the stomach seems to be associated with the risk of aspiration. Further studies, specifically addressing patients after difficult airway management situations are warranted.

Postponing intubation in spontaneously breathing major trauma patients upon emergency room admission does not impair outcome

Background

Pre-hospital emergency anaesthesia and tracheal intubation are life-saving interventions in trauma patients. However, there is evidence suggesting that the risks associated with both procedures outweigh the benefits. Thus, we assessed whether induction of anaesthesia and tracheal intubation of trauma patients can be postponed in spontaneously breathing patients until emergency room (ER) admission without increasing mortality.

Methods

Retrospective analysis of major trauma patients either intubated on-scene by an emergency medical service (EMS) physician (pre-hospital intubation, PHI) or within the first 10 min after admission at a level 1 trauma centre (emergency room intubation, ERI). Data was extracted from the German Trauma Registry, hospital patient data management and electronic clinical information system.

Results

From a total of 946 major trauma cases documented between 2010 and 2017, 294 patients matched the study inclusion criteria. Mortality rate of PHI (N = 258) vs. ERI (N = 36) patients was 26.4% vs. 16.7% (p = 0.3). After exclusion of patients with severe traumatic brain injury and/or pre-hospital cardiac arrest, mortality rate of PHI (N = 100) vs. ERI patients (N = 29) was 6% vs. 17.2%, (p = 0.07). Median on-scene time was significantly (p < 0.01) longer in PHI (30 min; IQR: 21–40) vs. ERI patients (20 min; IQR: 15–28).

Conclusions

There was no statistical difference in mortality rates of spontaneously breathing trauma patients intubated on-scene when compared with patients intubated immediately after hospital admission. Due to the retrospective study design and small case number, further studies evaluating the impact of airway management timing in sufficiently breathing trauma patients are warranted.

[Intensive care treatment of traumatic brain injury in multiple trauma patients : Decision making for complex pathophysiology]

Traumatic brain injury (TBI) and hemorrhagic shock due to uncontrolled bleeding are the major causes of death after severe trauma. Mortality rates are threefold higher in patients suffering from multiple injuries and additionally TBI. Factors known to impair outcome after TBI, namely hypotension, hypoxia, hypercapnia, acidosis, coagulopathy and hypothermia are aggravated by the extent and severity of extracerebral injuries. The mainstays of TBI intensive care may be, at least temporarily, contradictory to the trauma care concept for multiple trauma patients. In particular, achieving normotension in uncontrolled bleeding situations, maintenance of normocapnia in traumatic lung injury and thromboembolic prophylaxis are prone to discussion. Due to an ongoing uncertainty about the definition of normotensive blood pressure values, a cerebral perfusion pressure-guided cardiovascular management is of key importance. In contrast, there is no doubt that early goal directed coagulation management improves outcome in patients with TBI and multiple trauma. The timing of subsequent surgical interventions must be based on the development of TBI pathology; therefore, intensive care of multiple trauma patients with TBI requires an ongoing and close cooperation between intensivists and trauma surgeons in order to individualize patient care.

Emergency management of patients with ST-segment elevation myocardial infarction in Eastern Austria: a descriptive quality control study

Background

Myocardial infarction is a time-critical condition and its outcome is determined by appropriate emergency care. Thus we assessed the efficacy of a supra-regional ST-segment elevation myocardial infarction (STEMI) network in Easternern Austria.

Methods

The Eastern Austrian STEMI network serves a population of approx. 766.000 inhabitants within a region of 4186 km². Established in 2007, it now comprises 20 pre-hospital emergency medical service (EMS) units (10 of these physician-staffed), 4 hospitals and 3 cardiac intervention centres. Treatment guidelines were updated in 2012 and documentation within a web-based STEMI registry became mandatory. For this retrospective qualitative control study, data from February 2012–April 2015 was assessed.

Results

A total of 416 STEMI cases were documented, and 99% were identified by EMS within 6 (4.0–8.0) minutes after arrival. Median time loss between onset of pain and EMS call was 54 (20–135) minutes; response, pre-hospital and door-to-balloon times were 14 (10–20), 46 (37–59) and 45 (32–66) minutes, respectively. When general practitioners were involved, time between onset of pain and balloon inflation significantly increased from 180 (135–254) to 218 (155–348) minutes (p < .001). A pre-hospital time < 30 min was achieved in 25.8% of all patients during the day vs. 11.6% during the night (p < .001). Three hundred forty-five patients (83%) were subjected to primary percutaneous coronary intervention (PPCI), and 6.5% were thrombolysed by EMS. Pre-hospital complication rate was 18% (witnessed cardiac arrest 7%, threatening arrhythmias 6%, cardiogenic shock 5%). Twenty-four hours and hospital mortality rate were 1.2 and 2.8%, respectively.

Discussion

Optimal patient care and subsequently outcome of STEMI is strongly determined by a short patient-decision time to call EMS and by the first medical contact to balloon time (FMCBT). Supra-regional networks are key in order to increase the efficacy and efficiency of health care. The goal of 120 min FMCBT was achieved in 78% of our patients immediately managed by EMS, thus indicating room for improvement.

Conclusion

In conclusion, results from the Eastern Austrian STEMI network shed light on the necessity of increasing patient awareness in order to minimize any time loss derived by delayed EMS calls. Involvement of family physicians resulted in prolonged FMCBT. A stronger utilization of rescue helicopters could further improve the efficacy of this supra-regional network. Nevertheless PPCI rates, time intervals and outcome rates compare well with international benchmarks.

Success rates of pre-hospital difficult airway management: a quality control study evaluating an in-hospital training program

BACKGROUND

Competence in emergency airway management is key in order to improve patient safety and outcome. The scope of compulsory training for emergency physicians or paramedics is quite limited, especially in Austria. The purpose of this study was to review the difficult airway management performance of an emergency medical service (EMS) in a region that has implemented a more thorough training program than current regulations require, comprising 3 months of initial training and supervised emergency practice and 3 days/month of on-going in-hospital training as previously reported.

METHODS

This is a subgroup analysis of pre-hospital airway interventions performed by non-anesthesiologist EMS physicians between 2006 and 2016. The dataset is part of a retrospective quality control study performed in the ground EMS system of Wiener Neustadt, Austria. Difficult airway missions recorded in the electronic database were matched with the hospital information system and analyzed.

RESULTS

Nine hundred thirty-three of 23060 ground EMS patients (4%) required an airway intervention. In 48 cases, transient bag-mask-valve ventilation was sufficient, and 5 patients needed repositioning of a pre-existing tracheostomy cannula. Eight hundred thirty-six of 877 patients (95.3%) were successfully intubated within two attempts; in 3 patients, a supraglottic airway device was employed first line. Management of 41 patients with failed tracheal intubation comprised laryngeal tubes (n = 21), intubating laryngeal mask (n = 11), ongoing bag-mask-valve ventilation (n = 8), and crico-thyrotomy (n = 1). There was no cannot intubate/cannot ventilate situation. Blood gas analysis at admission revealed hypoxemia in 2 and/or hypercapnia in 11 cases.

CONCLUSION

During the 11-year study period, difficult airways were encountered in 5% but sufficiently managed in all patients. Thus, the training regime presented might be a feasible and beneficial model for training of non-anesthesiologist emergency physicians as well as paramedics.

Analgosedation of adult patients with elevated intracranial pressure : Survey of current clinical practice in Austria

BACKGROUND

Analgesia and sedation are key items in intensive care. Recently published S3 guidelines specifically address treatment of patients with elevated intracranial pressure.

METHODS

The Austrian Society of Anesthesiology, Resuscitation and Intensive Care Medicine carried out an online survey of neurointensive care units in Austria in order to evaluate the current state of practice in the areas of analgosedation and delirium management in this high-risk patient group.

RESULTS

The response rate was 88%. Induction of anesthesia in patients with elevated intracranial pressure is carried out with propofol/fentanyl/rocuronium in >80% of the intensive care units (ICU), 60% use midazolam, 33.3% use esketamine, 13.3% use barbiturates and 6.7% use etomidate. For maintenance of analgosedation up to 72 h, propofol is used by 80% of the ICUs, followed by remifentanil (46.7%), sufentanil (40%) and fentanyl (6.7%). For long-term sedation, 86.7% of ICUs use midazolam, 73.3% sufentanil and 73.3% esketamine. For sedation periods longer than 7 days, 21.4% of ICUs use propofol. Reasons for discontinuing propofol are signs of rhabdomyolysis (92.9%), green urine, elevated liver enzymes (71.4% each) and elevated triglycerides (57.1%). Muscle relaxants are only used during invasive procedures. Inducing a barbiturate coma is rated as a last resort by 53.3% of respondents. The monitoring methods used are bispectral index (BIS™, 61.5% of ICUs), somatosensory-evoked potentials (SSEP, 53.8%), processed electroencephalography (EEG, 38.5%), intraparenchymal partial pressure of oxygen (pO₂, 38.5%) and microdialysis (23.1%). Sedation and analgesia are scored using the Richmond agitation and sedation score (RASS, 86.7%), sedation agitation scale (SAS, 6.7%) or numeric rating scale (NRS, 50%) and behavioral pain scale (BPS, 42.9%), visual analogue scale (VAS), critical care pain observation tool (CCPOT, each 14.3%) and verbal rating scale (VRS, 7.1%). Delirium monitoring is done using the confusion assessment method for intensive care units (CAM-ICU, 46.2%) and intensive care delirium screening checklist (ICDSC, 7.7%). Of the ICUs 46.2% do not carry out delirium monitoring.

CONCLUSION

We found good general compliance with the recommendations of the current S3 guidelines. Room for improvement exists in monitoring and the use of scores to detect delirium.

In-hospital airway management training for non-anesthesiologist EMS physicians: a descriptive quality control study

Background

Pre-hospital airway management is a major challenge for emergency medical service (EMS) personnel. Despite convincing evidence that the rescuer’s qualifications determine efficacy of tracheal intubation, in-hospital airway management training is not mandatory in Austria, and often neglected. Thus we sought to prove that airway management competence of EMS physicians can be established and maintained by a tailored training program.

Methods

In this descriptive quality control study we retrospectively evaluated all in- and pre-hospital airway cases managed by EMS physicians who underwent a structured in-hospital training program in anesthesia at General Hospital Wiener Neustadt. Data was obtained from electronic anesthesia and EMS documentation systems.

Results

From 2006 to 2016, 32 EMS physicians with 3-year post-graduate education, but without any prior experience in anesthesia were trained. Airway management proficiency was imparted in three steps: initial training, followed by an ongoing practice schedule in the operating room (OR). Median and interquartile range of number of in-hospital tracheal intubations (TIs) vs. use of supra-glottic airway devices (SGA) were 33.5 (27.5–42.5) vs. 19.0 (15.0–27.0) during initial training; 62.0 (41.8–86.5) vs. 33.5 (18.0–54.5) during the first, and 64.0 (34.5–93.8) vs. 27 (12.5–56.0) during the second year. Pre-hospitaly, every physician performed 9.0 (5.0–14.8) TIs vs. 0.0 (0.0–0.0) SGA cases during the first, and 9.0 (7.0–13.8) TIs vs. 0.0 (0.0–0.3) SGA during the second year. Use of an SGA was mandatory when TI failed after the second attempt, thus accounting for a total of 33 cases. In 8 cases, both TI and SGA failed, but bag mask ventilation was successfully performed. No critical events related to airway management were noted and overall success rate for TI with a max of 2 attempts was 95.3%.

Discussion

Number of TIs per EMS physician is low in the pre-hospital setting. A training concept that assures an additional 60+ TIs per year appears to minimize failure rates. Thus, a fixed amount of working days in anesthesia seems crucial to maintain proficiency.

Conclusions

In-hospital training programs are mandatory for non-anesthetist EMS physicians to gain competence in airway management and emergency anesthesia.Our results might be helpful when discussing the need for regulation and financing with the authorities.

Current practice in neurocritical care of patients with subarachnoid haemorrhage and severe traumatic brain injury : Results of the Austrian Neurosurvey Study

OBJECTIVES

The task force Neuroanaesthesia of the Austrian Society of Anaesthesiology, Resuscitation and Intensive Care Medicine (ÖGARI) is aiming to develop and provide recommendations in order to improve neurocritical care in Austria. Thus, a survey on neurocritical care concepts in Austria regarding intensive care of subarachnoid haemorrhage (SAH) and severe traumatic brain injury (TBI) was performed to assess the current status.

METHODS

An online internet questionnaire comprising 59 items on current concepts of SAH and TBI critical care was sent to 117 anaesthesiology departments.

RESULTS

The survey was answered by 30 (25.6 %) of the hospitals, 24 (80 %) of them treating patients with SAH and/or TBI. Data from ten SAH centres reveal that definitive care was achieved within 24 h in all hospitals; a case load >50 per year is noted in 70 % of intensive care units (ICU). In all, 50 % of departments employ written protocols for treatment. Regarding the treatment of TBI patients, 14 answers were received, indicating that 42.9 % of departments provide care for >50 patients per year. Time between arrival and CT scan is <30 min in all hospitals, and 28.6 % of departments rely on written protocols. Only 14.3 % of hospitals report about routine morbidity and mortality rounds. While the neurologic status is assessed at discharge from the ICU, there is no evaluation of 1‑year outcome.

CONCLUSIONS

Definitive care of SAH and TBI patients is achieved timely in Austria. When compared with SAH, more hospitals with lower case loads take care of TBI patients. Written guidelines and protocols at institutional level are often missing. Since routine morbidity and mortality conferences are sparse, and long-term outcome is not assessed, there is room for improvement.

Airplane transport isolators may loose leak tightness after rapid cabin decompression

Air medical transport of patients suffering of highly infectious diseases is typically performed employing portable isolation chambers. Although the likelihood of decompression flight emergencies is low, sustainability of the devices used is crucial. When a standard isolation unit was subjected to an explosive cabin decompression of 493 hPa, simulating a 32808 ft flight level accident, leak tightness of the unit was lost due to rupture of the bag caused by over expansion. When the pressure chamber experiment was repeated with a modified unit, distension was minimized by an additional compensation air bag, thus ensuring leak tightness.

Pediatric trauma in the Austrian Alps: the epidemiology of sport-related injuries in helicopter emergency medical service

BACKGROUND/PURPOSE

We aimed to examine the epidemiological characteristics and injury patterns of pediatric trauma in helicopter emergency medical service (HEMS) caused by sports/outdoor activities in alpine environment.

METHODS

This retrospective cohort study analyzed 912 primary HEMS missions for pediatric trauma (0-14 years of age) in Austrian Alps between 1 January 2006 and 30 June 2007. Children were stratified by age into toddlers (3-5 years), children in early (6-9 years), and late school age (10-14 years).

RESULTS

The majority of pediatric sports-related trauma in alpine environment was caused by skiing (82.1%; n=749). Pediatric patients were predominately in late school age and boys (72.8%, n=664 and 61.0%, n=556, respectively) and a minority (16.0%, n=146) was severely injured. Overall, fracture (47.0%, n=429), contusion (17.9%, n=163), and traumatic brain injury (17.0%, n=155) were the most common prehospital diagnoses. The most frequent pattern of injury was related to the head/face and spine (36.3%, n=331).

CONCLUSIONS

The knowledge about epidemiological characteristics of HEMS use for injured children in alpine environment may be essential for training requirements of HEMS crews and operational considerations of HEMS providers. The incidence of head and spinal injuries requires support for initiatives to promote helmet wear and appropriate risk behavior amongst skiers and snowboarders.

The epidemiology of amputation injuries in the Austrian helicopter emergency medical service: a retrospective, nationwide cohort study

PURPOSE

Data on the epidemiological characteristics of traumatic amputations in prehospital emergency care, especially in the context of air rescue, are scarce. Therefore, we aimed to describe the epidemiology of total and subtotal amputation injuries encountered by the OEAMTC helicopter emergency medical service (HEMS) in Austria, based on an almost nationwide sample.

METHODS

We retrospectively reviewed all HEMS rescue missions flown for amputation injuries in 2009. Only primary missions were analyzed.

RESULTS

In total, 149 out of 16,100 (0.9 %) primary HEMS rescue missions were for patients suffering from amputation injuries. Among these, HEMS physicians diagnosed 63.3 % (n = 94) total and 36.9 % (n = 55) subtotal amputations, with both groups showing a predominance of male victims (male:female ratios were 8:1 and 6:1, respectively).The highest rate occurred among adults between 45 and 64 years of age (35.6 %, n = 53). The most common causes were working with a circular saw (28.9 %, n = 43) and processing wood (16.8 %, n = 25). The majority of the cases included digital amputation injuries (77.2 %, n = 115) that were mainly related to the index finger (36.2 %, n = 54). One hundred forty patients (94.0 %) showed a total GCS of more than 12. Amputations were most prevalent in rural areas (84.6 %, n = 126) and between Thursday and Saturday (55.0 %, n = 82). The replantation rate after primary air transport was low (28 %).

CONCLUSIONS

In the HEMS, amputation injuries are infrequent and mostly not life-threatening. However, HEMS crews need to maintain their focus on providing sufficient and fast primary care while facilitating rapid transport to a specialized hospital. The knowledge of the epidemiological characteristics of amputation injuries encountered in the HEMS gained in this study may be useful for educational and operational purposes.

Prehospital pediatric emergencies in Austrian helicopter emergency medical service - a nationwide, population-based cohort study

INTRODUCTION

Arguably, the most challenging emergencies encountered by emergency medical service crews involve children. Because only scant data exist about the epidemiology of pediatric emergencies in helicopter emergency medical service (HEMS) on a population level, we sought to determine the epidemiological characteristics stratified by responding area in a large nationwide sample.

METHODS

This was a retrospective cohort study including all pediatric patients (0-14 years of age) who were treated by HEMS in Austria from January 2006 to June 2007 (18 months).

RESULTS

Pediatric emergencies accounted for 2207 (8.2%) of a total of 26.850 helicopter rescue missions. Of those, 69.9% (n = 1543) were not involved in life-threatening emergencies. The rate of critical pediatric emergencies was higher in urban than in rural or alpine environment (45.2%, 38.2% and 20.3%, respectively). The most common chief complaint was trauma; the frequency of injuries ranged from 54.2% (582/1074) in rural area and 60.3% (44/73) in urban area to 91.4% (969/1060) in alpine environment. Fracture and head trauma (34.9%; 557/1595 and 26.3%; 419/1595, respectively) were the most common injuries. Advanced life support measures like tracheal intubation, cardiopulmonary resuscitation and intraosseous access were rarely performed (3.7%; n = 82, 1.9%; n = 42 and 0.9%; n = 19, respectively).

CONCLUSIONS

Pediatric emergencies in Austrian HEMS show different epidemiological characteristics in alpine, urban and rural operational environments. Because of challenges and infrequency of prehospital pediatric emergencies, HEMS crews need to maintain their skills in pediatric advanced life support and trauma care.

The mouth-to-bag resuscitator during standard anaesthesia induction in apnoeic patients

AIM

Ventilation of a non-intubated emergency patient by inexperienced rescuers with a standard bag-valve device may result in high inspiratory flow rates and subsequently high airway pressures with stomach inflation. Therefore, a self-inflating bag has been developed that requires lay rescuers to blow up a single-use balloon inside an adult bag-valve device, which, in turn, displaces air within the bag towards the patient. This concept has been compared to standard adult bag-valve devices earlier in bench models but not in patients.

METHODS

An anaesthetist who was blinded to all monitor tracings ventilated the lungs of 40 apnoeic patients during routine anaesthesia induction either with a standard bag-valve device or with the mouth-to-bag resuscitator in a random order. Study endpoints were peak inspiratory flow rates, peak airway pressure, tidal volumes and inspiratory time.

RESULTS

Peak inspiratory flow was 40+/-10lmin(-1) for the standard bag-valve device versus 33+/-13lmin(-1) for the mouth-to-bag resuscitator (P<0.0001); peak airway pressure was 17+/-5cmH(2)O versus 14+/-5cmH(2)O (P<0.0001); inspiratory tidal volume was 477+/-133ml versus 644+/-248ml (P<0.001) and inspiratory time was 1.1+/-0.3s versus 1.9+/-0.6s (P<0.0001).

CONCLUSION

Employing the mouth-to-bag resuscitator during simulated ventilation of a non-intubated patient in respiratory arrest significantly decreased peak inspiratory flow and peak airway pressure and increased inspiratory tidal volume and inspiratory times compared to a standard bag-valve device.

Inspiratory impedance threshold device effects on hypotension in heat-stroked swine

INTRODUCTION

Heat stroke is still an epidemiologically relevant disease with overall mortality rates as high as 15-33%. In heat stroke, hypotension is caused by relative central hypovolemia. We performed a feasibility study to determine if an inspiratory impedance threshold valve (ITDTM) set to open at -12 cm H2O would reverse systemic hypotension by enhancing venous return in hyperthermic, hypotensive, but spontaneously breathing animals.

METHODS

Seven anesthetized pigs weighing 30 +/- 2 kg were warmed with a heating device until a mean rectal temperature of 44 degrees C was reached, and mean arterial blood pressure (MAP) was < or = 60 mmHg. The animals were then treated with the ITD. An intravenous bolus of 200 cc of 4 degrees C normal saline was delivered 20 min after the ITD was placed, and external cooling was started.

RESULTS

Heat stroke criteria were achieved within 105 +/- 15 min. MAP had decreased from 105 +/- 5 to 57 +/- 5 mmHg, and respiratory rates had increased from 33 +/- 2 to 101 +/- 13 breaths/min. Addition of the ITD significantly improved MAP to 85 +/- 4 mmHg, and reduced respiratory rate to 54 +/- 6 breaths/min within 2 min. The effect was sustained until fluid replacement and external cooling were delivered 20 min later. At that point, MAP returned to baseline within 30 min, and 6/7 animals survived for an additional 30 min.

CONCLUSIONS

Use of an inspiratory impedance threshold device resulted in an immediate rise in blood pressure in animals in heat stroke and preserved blood pressure for at least 20 min prior to cooling and fluid replacement.

Vasopressin improves survival in a porcine model of abdominal vascular injury

Introduction

We sought to determine and compare the effects of vasopressin, fluid resuscitation and saline placebo on haemodynamic variables and short-term survival in an abdominal vascular injury model with uncontrolled haemorrhagic shock in pigs.

Methods

During general anaesthesia, a midline laparotomy was performed on 19 domestic pigs, followed by an incision (width about 5 cm and depth 0.5 cm) across the mesenterial shaft. When mean arterial blood pressure was below 20 mmHg, and heart rate had declined progressively, experimental therapy was initiated. At that point, animals were randomly assigned to receive vasopressin (0.4 U/kg; n = 7), fluid resuscitation (25 ml/kg lactated Ringer's and 25 ml/kg 3% gelatine solution; n = 7), or a single injection of saline placebo (n = 5). Vasopressin-treated animals were then given a continuous infusion of 0.08 U/kg per min vasopressin, whereas the remaining two groups received saline placebo at an equal rate of infusion. After 30 min of experimental therapy bleeding was controlled by surgical intervention, and further fluid resuscitation was performed. Thereafter, the animals were observed for an additional hour.

Results

After 68 ± 19 min (mean ± standard deviation) of uncontrolled bleeding, experimental therapy was initiated; at that time total blood loss and mean arterial blood pressure were similar between groups (not significant). Mean arterial blood pressure increased in both vasopressin-treated and fluid-resuscitated animals from about 15 mmHg to about 55 mmHg within 5 min, but afterward it decreased more rapidly in the fluid resuscitation group; mean arterial blood pressure in the placebo group never increased. Seven out of seven vasopressin-treated animals survived, whereas six out of seven fluid-resuscitated and five out of five placebo pigs died before surgical intervention was initiated (P < 0.0001).

Conclusion

Vasopressin, but not fluid resuscitation or saline placebo, ensured short-term survival in this vascular injury model with uncontrolled haemorrhagic shock in sedated pigs.

[AnaConDa as last resort treatment. Case report of a chronic obstructive pulmonary disease]

Treatment of patients suffering from decompensated chronic pulmonary disease (COPD) not responding to pharmacological therapy is still a major challenge in intensive care medicine. Administration of volatile anaesthetics may be a therapy of last resort in these cases. We report on a 65-year-old woman suffering from exacerbated COPD, who could not be sufficiently ventilated despite comprehensive pharmacological therapy. In order to administer a volatile anaesthetic in the ICU, we employed the "Anaesthetic Conserving Device" (AnaConDa) consisting of a vaporizer chamber embedded in a charcoal filter system. With this device, every standard intensive care ventilator can be used to deliver volatile anaesthetics in a safe and economic manner. The AnaConDa converts the open breathing system of the intensive care ventilator into a de facto half-closed system. The very low pulmonary compliance of the patient increased dramatically after administration of 0.75 vol% halothane for 48 h (27 vs. 150 ml/mbar). Elimination of CO(2) was improved and weaning from controlled ventilation was achieved. After surgical removal of a pulmonary abscess and a total of 78 days of intensive care therapy, the patient was discharged in good health.

[Vasopressin for therapy of persistent traumatic hemorrhagic shock: The VITRIS.at study]

While fluid management is established in controlled hemorrhagic shock, its use in uncontrolled hemorrhagic shock is being controversially discussed, because it may worsen bleeding. In the irreversible phase of hemorrhagic shock that was unresponsive to volume replacement, airway management and catecholamines, vasopressin was beneficial due to an increase in arterial blood pressure, shift of blood away from a subdiaphragmatic bleeding site towards the heart and brain and decrease of fluid resuscitation requirements. The purpose of this multicenter, randomized, controlled, international trial is to assess the effects of vasopressin (10 IU IV) vs. saline placebo IV (up to 3 injections at least 5 min apart) in patients with prehospital traumatic hemorrhagic shock that persists despite standard shock treatment. The study will be carried out by helicopter emergency medical service teams in Austria, Germany, Czech Republic, Portugal, the Netherlands and Switzerland. Inclusion criteria are adult trauma patients with presumed traumatic hemorrhagic shock (systolic arterial blood pressure <90 mmHg) that does not respond to the first 10 min of standard shock treatment (endotracheal intubation, fluid resuscitation and use of vasopressors) after arrival of the first emergency physician at the scene. The time window for randomization will close after 30 min of shock treatment. Exclusion criteria are terminal illness, no intravenous access, age <18 years, injury >60 min before randomization, cardiac arrest before randomization, presence of a do-not-resuscitate order, untreated tension pneumothorax, untreated cardiac tamponade, or known pregnancy. Primary study end-point is the hospital admission rate, secondary end-points are hemodynamic variables, fluid resuscitation requirements and hospital discharge rate.

[The new 2005 resuscitation guidelines of the European Resuscitation Council: comments and supplements]

The new CPR guidelines are based on a scientific consensus which was reached by 281 international experts. Chest compressions (100/min, 4-5 cm deep) should be performed in a ratio of 30:2 with ventilation (tidal volume 500 ml, Ti 1 s, FIO2 if possible 1.0). After a single defibrillation attempt (initially biphasic 150-200 J, monophasic 360 J, subsequently with the respective highest energy), chest compressions are initiated again immediately for 2 min. Endotracheal intubation is the gold standard; other airway devices may be employed as well depending on individual skills. Drug administration routes for adults and children: first choice IV, second choice intraosseous, third choice endobronchial [epinephrine dose 2-3x (adults) or 10x (pediatric patients) higher than IV]. Vasopressors: 1 mg epinephrine every 3-5 min IV. After the third unsuccessful defibrillation attempt amiodarone IV (300 mg); repetition (150 mg) possible. Sodium bicarbonate (1 ml/kg 8.4%) only in excessive hyperkalemia, metabolic acidosis, or intoxication with tricyclic antidepressants. Consider atropine (3 mg) and aminophylline (5 mg/kg). Thrombolysis during spontaneous circulation only in myocardial infarction or massive pulmonary embolism; during CPR only during massive pulmonary embolism. Cardiopulmonary bypass only after cardiac surgery, hypothermia or intoxication. Pediatrics: best improvement in outcome by preventing cardiocirculatory collapse. Alternate chest thumps and chest compression (infants), or abdominal compressions (>1-year-old) in foreign body airway obstruction. Initially five breaths, followed by chest compressions (100/min; approximately 1/3 of chest diameter): ventilation ratio 15:2. Treatment of potentially reversible causes (4 "Hs", "HITS": hypoxia, hypovolemia, hypo- and hyperkaliemia, hypothermia, cardiac tamponade, intoxication, thrombo-embolism, tension pneumothorax). Epinephrine 10 microg/kg IV or intraosseously, or 100 microg (endobronchially) every 3-5 min. Defibrillation (4 J/kg; monophasic oder biphasic) followed by 2 min CPR, then ECG and pulse check. Newborns: inflate the lungs with bag-valve mask ventilation. If heart rate<60/min chest compressions:ventilation ratio 3:1 (120 chest compressions/min). Postresuscitation phase: initiate mild hypothermia [32-34 degrees C for 12-24 h; slow rewarming (<0.5 degrees C/h)]. Prediction of CPR outcome is not possible at the scene; determining neurological outcome within 72 h after cardiac arrest with evoked potentials, biochemical tests and physical examination. Even during low suspicion for an acute coronary syndrome, record a prehospital 12-lead ECG. In parallel to pain therapy, aspirin (160-325 mg PO or IV) and in addition clopidogrel (300 mg PO). As antithrombin, heparin (60 IU/kg, max. 4000 IU) or enoxaparine. In ST-segment elevation myocardial infarction, define reperfusion strategy depending on duration of symptoms until PCI (prevent delay>90 min until PCI). Stroke is an emergency and needs to be treated in a stroke unit. A CT scan is the most important evaluation, MRT may replace a CT scan. After hemorrhage exclusion, thrombolysis within 3 h of symptom onset (0.9 mg/kg rt-PA IV; max 90 mg within 60 min, 10% of the entire dosage as initial bolus, no aspirin, no heparin within the first 24 h). In severe hemorrhagic shock, definite control of bleeding is the most important goal. For successful CPR of trauma patients, a minimal intravascular volume status and management of hypoxia are essential. Aggressive fluid resuscitation, hyperventilation, and excessive ventilation pressure may impair outcome in severe hemorrhagic shock. Despite bad prognosis, CPR in trauma patients may be successful in select cases. Any CPR training is better than nothing; simplification of contents and processes remains important.

An observational study of vasopressin infusion during uncontrolled haemorrhagic shock in a porcine trauma model: Effects on bowel function

The effects of vasopressin on the gut in a porcine uncontrolled haemorrhagic shock model are described. In eight anaesthetised pigs, a liver laceration was performed; when haemorrhagic shock was decompensated, all animals received 0.4 IU/kg vasopressin, followed by 0.08 IU/kg min over 30 min, which maintained a mean arterial blood pressure >40 mmHg. Subsequent surgical intervention, infusion of whole blood and fluids resulted in a stable cardiocirculatory status. Three hours after stabilisation, all pigs developed non-bloody diarrhoea which converted into normal bowel movements within 24 h. All histological samples retained 7 days after the experiment revealed no histopathological changes. In conclusion, in this small observational study of uncontrolled porcine haemorrhagic shock, a resuscitation strategy that included high dose vasopressin was associated with transient diarrhoea and good long term survival.

Effects of face mask ventilation in apneic patients with a resuscitation ventilator in comparison with a bag-valve-mask

Bag-valve-mask ventilation in an unprotected airway is often applied with a high flow rate or a short inflation time and, therefore, a high peak airway pressure, which may increase the risk of stomach inflation and subsequent pulmonary aspiration. Strategies to provide more patient safety may be a reduction in inspiratory flow and, therefore, peak airway pressure. The purpose of this study was to evaluate the effects of bag-valve-mask ventilation vs. a resuscitation ventilator on tidal volume, peak airway pressure, and peak inspiratory flow rate in apneic patients. In a crossover design, 40 adults were ventilated during induction of anesthesia with either a bag-valve-mask device with room air, or an oxygen-powered, flow-limited resuscitation ventilator. The study endpoints of expired tidal volume, minute volume, respiratory rate, peak airway pressure, delta airway pressure, peak inspiratory flow rate and inspiratory time fraction were measured using a pulmonary monitor. When compared with the resuscitation ventilator, the bag-valve-mask resulted in significantly higher (mean+/-SD) peak airway pressure (15.3+/-3 vs. 14.1+/-3 cm H2O, respectively; p=0.001) and delta airway pressure (14+/-3 vs. 12+/-3 cm H2O, respectively; p<0.001), but significantly lower oxygen saturation (95+/-3 vs. 98+/-1%, respectively; p<0.001). No patient in either group had clinically detectable stomach inflation. We conclude that the resuscitation ventilator is at least as effective as traditional bag-valve-mask or face mask resuscitation in this population of very controlled elective surgery patients.

Beatmung eines ungeschützten Atemwegs

BACKGROUND

Currently 30 chest compressions and 2 ventilations with an inspiratory time of 1 s are recommended during cardiopulmonary resuscitation with an unprotected airway, thus spending about 15% instead of 40% of resuscitation time on ventilation. Time could be gained for chest compressions when reducing inspiratory time from 2 s to 1 s, however, stomach inflation may increase as well.

METHODS

In an established bench model we evaluated the effect of reducing inspiratory time from 2 s to 1 s at different lower oesophageal sphincter pressure (LOSP) levels using a novel peak inspiratory-flow and peak airway-pressure-limiting bag-valve-mask device (Smart-Bag).

RESULTS

A reduction of inspiratory time from 2 s to 1 s resulted in significantly lower peak airway pressure with LOSP of 0.49 kPa (5 cm H2O), 0.98 kPa (10 cm H2O) and 1.47 kPa (15 cm H2O) and an increase with 1.96 kPa (20 cm H2O). Lung tidal volume was reduced with 1 s compared to 2 s. When reducing inspiratory time from 2 s to 1 s, stomach inflation occurred only at a LOSP of 0.49 kPa (5 cm H2O).

CONCLUSIONS

In this model of a simulated unprotected airway, a reduction of inspiratory time from 2 s to 1 s using the Smart-Bag resulted in comparable inspiratory peak airway pressure and lower, but clinically comparable, lung tidal volume. Stomach inflation occurred only at a LOSP of 0.49 kPa (5 cm H2O), and was higher with an inspiratory time of 2 s vs 1 s.

Maskenbeatmung als Rückzugsstrategie zur endotrachealen Intubation

The goal of ventilation in an unprotected airway is to optimize oxygenation and carbon dioxide elimination of the patient. This can be achieved with techniques such as mouth-to-mouth ventilation, but preferably with bag-valve-mask ventilation. Securing the airway with an endotracheal tube is the gold standard, but excellent success in emergency airway management depends on initial training, retraining, and actual frequency of a given procedure in the routine. "Patients do not die from failure to intubate; they die from failure to stop trying to intubate or from undiagnosed oesophageal intubation" (Scott 1986). Therefore, adequate face mask ventilation has absolute priority in airway management by an unexperienced rescuer. During ventilation of an unprotected airway, stomach inflation and subsequent severe complications may result. Careful ventilation can be performed with low inspiratory pressure and flow, and subsequently with a low tidal volume at a high inspiratory fraction of oxygen. This could be a strategy to achieve more patient safety.

Signs of Inflammation After Sciatic Nerve Block in Pigs

Nerve stimulators are widely used to assist with peripheral nerve blocks but do not eliminate the risk of nerve injury. We evaluated the histologic findings 6 h after sciatic nerve block with bupivacaine in pigs. When a motor response was still obtained with a current <0.2 mA (n = 10), the postmortem microscopic evaluation revealed lymphocytes and granulocytes sub-, peri-, and intraneurally in 5 (50%) of 10 pigs. No signs of inflammation were observed when the muscle contraction was achieved with a current between 0.3 and 0.5 mA (P = 0.03). In conclusion, the current required to elicit a motor response, the position of the needle tip, and the subsequent likelihood of nerve damage merit further evaluation.

Employing vasopressin as an adjunct vasopressor in uncontrolled traumatic hemorrhagic shock. Three cases and a brief analysis of the literature

Resuscitation of patients in hemorrhagic shock remains one of the most challenging aspects of trauma care. We showed in experimental studies that vasopressin, but not fluid resuscitation, enabled short-term and long-term survival in a porcine model of uncontrolled hemorrhagic shock after penetrating liver trauma. In this case report, we present two cases with temporarily successful cardiopulmonary resuscitation (CPR) using vasopressin and catecholamines in uncontrolled hemorrhagic shock with subsequent cardiac arrest that was refractory to catecholamines and fluid replacement. In a third patient, an infusion of vasopressin was started before cardiac arrest occurred; in this case, we were able to stabilize blood pressure thus allowing further therapy. The patient underwent multiple surgical procedures, developed multi-organ failure, but was finally discharged from the critical care unit without neurological damage.

Frühdefibrillation im Gletscherskigebiet: übertrieben oder Überleben? 3 Fallberichte und eine Standortbestimmung

In the months of winter 2002-2004, three cases of non-traumatic cardiac arrest occurred in the skiing area of the Stubaier Gletscher in Tyrol, Austria. All patients were initially resuscitated by ski patrol members, including the use of an automated external defibrillator (AED). Two of the patients were alive at hospital admission, one patient was discharged from hospital without neurological damage. The article describes the chain of survival in a high-alpine area, the installation of a modified public-access-defibrillation (PAD) system in a skiing area, and the prerequisites necessary for a successful PAD-program far away from an organized emergency medical system.

Verkürzte Inspirationszeit während der Beatmung eines ungeschützten Atemweges

BACKGROUND

In an unprotected airway during cardiopulmonary resuscitation, two ventilations with an inspiratory time of 2 s after 15 chest compressions are recommended. Therefore, approximately 30% of the resuscitation attempt is spent on ventilation. Since survival rates did not decrease sharply when minute ventilation levels were relatively low, and uninterrupted chest compressions with a constant rate of approximately 100/min have been shown to be lifesaving, it may be beneficial to decrease the time spent on ventilation and instead, increase the time for chest compressions.

METHODS

In an established bench model of a simulated, unprotected airway with increased airway resistance, we evaluated if inspiratory time can be decreased from 2 to 1 s at different lower oesophageal sphincter pressure (LOSP) levels during ventilation with a bag-valve-mask device.

RESULTS

An inspiratory time of 2 vs. 1 s resulted in significantly lower peak airway pressure, while lung tidal volume was significantly higher at an inspiratory time of 2 s and a LOSP of 5 cm H(2)O (480+/-20 vs. 380+/-30 ml) and 10 cm H(2)O (630+/-50 vs. 440+/-20 ml) and significantly lower at a LOSP of 15 cm H(2)O (470+/-70 vs. 540+/-20 ml). While neither ventilation strategy produced stomach inflation at 20 cm H(2)O LOSP, 1 vs. 2 s inspiratory time produced significantly higher stomach inflation at 15 cm H(2)O LOSP (8+/-11 vs. 0 ml) and significantly lower stomach inflation at a LOSP of 5 cm H(2)O (359+/-31 vs. 375+/-29 ml) and 10 cm H(2)O (28+/-13 vs. 36+/-12 ml) per breath.

CONCLUSION

In this model of a simulated, unprotected airway, a reduction of inspiratory time from 2 to 1 s resulted in a significant increase of peak airway pressure, while lung tidal volumes and stomach inflation volumes were statistically different but clinically comparable.

Die Behandlung des hämorrhagischen Schocks

The future of shock treatment depends on the importance of scientific results, and the willingness of physicians to optimize, and to reconsider established treatment protocols. There are four major potentially promising approaches to advanced trauma life support. First, control of hemorrhage by administration of local hemostatic agents, and a better, target-controlled management of the coagulation system. Second, improving intravascular volume by recruiting blood from the venous vasculature by preventing mistakes during mechanical ventilation, and by employing alternative spontaneous (i.e. use of the inspiratory threshold valve) or artificial ventilation strategies. In addition, artificial oxygen carriers may improve intravascular volume and oxygen delivery. Third, pharmacologic support of physiologic, endogenous mechanisms involved in the compensation phase of shock, and blockade of pathomechanisms that are known to cause irreversible vasoplegia (arginine vasopressin and K(ATP) channel blockers for hemodynamic stabilization). Fourth, employing potentially protective strategies such as mild or moderate hypothermia. Finally, the ultimate vision of trauma resuscitation is the concept of "suspended animation" as a form of delayed resuscitation after protection of vital organ systems.

Developing a Strategy to Improve Ventilation in an Unprotected Airway with a Modified Mouth-to-Bag Resuscitator in Apneic Patients

The strategies to ensure safety during ventilation of an unprotected airway are limiting airway pressure and/or inspiratory flow. In this prospective, randomized study we assessed the effect of face mask ventilation with small tidal volumes in the modified mouth-to-bag resuscitator (maximal volume, 500 mL) versus a pediatric self-inflatable bag versus automatic pressure-controlled ventilation in 40 adult apneic patients during induction of anesthesia. The mouth-to-bag resuscitator requires the rescuer to blow up a balloon inside the self-inflating bag that subsequently displaces air which then flows into the patient's airway. Respiratory variables were measured with a pulmonary monitor (CP-100). Mouth-to-bag resuscitator and pressure-controlled ventilation resulted in significantly lower (mean +/- sd) peak airway pressure (8 +/- 2 and 8 +/- 1 cm H(2)O), peak inspiratory flow rate (0.7 +/- 0.1 and 0.7 +/- 0.1 L/s), and larger inspiratory time fraction (33% +/- 5% and 47% +/- 2%) in comparison to pediatric self-inflating bag ventilation (12 +/- 3 cm H(2)O; 1 +/- 0.2 L/s; 27% +/- 4%; all P < 0.001). The tidal volumes were similar between groups. No stomach inflation occurred in either group. We conclude that using a modified mouth-to-bag resuscitator or automatic pressure-controlled ventilation with similar small tidal volumes during face mask ventilation resulted in an approximately 25% reduction in peak airway pressure when compared with a standard pediatric self-inflating bag.

Treatment of hypotension in pigs with an inspiratory impedance threshold device: a feasibility study

OBJECTIVE

An inspiratory impedance threshold device was evaluated in spontaneously breathing animals with hypotension to determine whether it could help improve systemic arterial pressures when fluid replacement was not immediately available.

DESIGN

Prospective, randomized.

SETTING

Animal laboratory.

SUBJECTS

Thirty-nine female farm pigs (weight, 28-33 kg).

INTERVENTIONS

A total of 39 anesthetized spontaneously breathing pigs were treated with an impedance threshold device, with cracking pressures from 0 to -20 cm H2O. Four separate experimental protocols were performed: protocol A, in which the hemodynamics of seven pigs were examined during application of an impedance threshold device at various levels of inspiratory impedance (-5, -10, -15, and -20 cm H(2)O), both before and after a severe, controlled hemorrhage to a systolic blood pressure of 50 - 55 mm Hg; protocol B, in which nine pigs bled to systolic blood pressure of 50 -55 mm Hg were treated with an impedance threshold device set at -12 cm H2O and were compared with nine others treated with a sham device; protocol C, in which the effects of the impedance threshold device on mixed venous gases were measured in seven hemorrhaged pigs; and protocol D, in which the effects of the impedance threshold device on cardiac output in seven hemorrhaged pigs were measured.

METHODS AND MAIN RESULTS

During initial studies with both normovolemic and hypovolemic pigs, sequential increases in inspiratory impedance resulted in a significant increase in systolic blood pressure, whereas diastolic left ventricular and right atrial pressures decreased significantly and proportionally to the level of impedance. When comparing the sham vs. active impedance threshold device (-12 cm H(2)O) in hypotensive pigs, systolic blood pressure (mean +/- sem) with active impedance threshold device treatment increased from 70 +/- 2 mm Hg to 105 +/- 4 mm Hg (p <.01). Pressures in the control group remained at 70 +/- 4 mm Hg (p <.01). Cardiac output increased by nearly 25% (p <.01) with the active impedance threshold device when calculated using the mixed gas equation and when determined by thermodilution.

CONCLUSIONS

These studies demonstrate that it is feasible to use a device that creates inspiratory impedance in spontaneously breathing normotensive and hypotensive pigs to increase blood pressure and enhance cardiopulmonary circulation in the absence of immediate fluid resuscitation. Further studies are needed to evaluate the potential long-term effects and limitations of this new approach to treat hypovolemic hypotension.

Treatment of uncontrolled hemorrhagic shock after liver trauma: fatal effects of fluid resuscitation versus improved outcome after vasopressin

In a porcine model of uncontrolled hemorrhagic shock, we evaluated the effects of vasopressin versus an equal volume of saline placebo versus fluid resuscitation on hemodynamic variables and short-term survival. Twenty-one anesthetized pigs were subjected to severe liver injury. When mean arterial blood pressure was <20 mm Hg and heart rate decreased, pigs randomly received either vasopressin IV (0.4 U/kg; n = 7), an equal volume of saline placebo (n = 7), or fluid resuscitation (1000 mL each of lactated Ringer's solution and hetastarch; n = 7). Thirty minutes after intervention, surviving pigs were fluid resuscitated while bleeding was surgically controlled. Mean (+/- SEM) arterial blood pressure 5 min after the intervention was significantly (P < 0.05) higher after vasopressin than with saline placebo or fluid resuscitation (58 +/- 9 versus 7 +/- 3 versus 32 +/- 6 mm Hg, respectively). Vasopressin improved abdominal organ blood flow but did not cause further blood loss (vasopressin versus saline placebo versus fluid resuscitation 10 min after intervention, 1343 +/- 60 versus 1350 +/- 22 versus 2536 +/- 93 mL, respectively; P < 0.01). Seven of 7 vasopressin pigs survived until bleeding was controlled and 60 min thereafter, whereas 7 of 7 saline placebo and 7 of 7 fluid resuscitation pigs died (P < 0.01). We conclude that vasopressin, but not saline placebo or fluid resuscitation, significantly improves short-term survival during uncontrolled hemorrhagic shock.

IMPLICATIONS

Although IV fluid administration is the mainstay of nonsurgical management of trauma patients with uncontrolled hemorrhagic shock, the efficacy of this strategy has been discussed controversially. In this animal model of severe liver trauma with uncontrolled hemorrhagic shock, vasopressin, but not saline placebo or fluid resuscitation, improved short-term survival.

Mechanical versus manual ventilation via a face mask during the induction of anesthesia: a prospective, randomized, crossover study

One approach to make ventilation safer in an unprotected airway has been to limit tidal volumes; another one might be to limit peak airway pressure, although it is unknown whether adequate tidal volumes can be delivered. Accordingly, the purpose of this study was to evaluate the quality of automatic pressure-controlled ventilation versus manual circle system face-mask ventilation regarding ventilatory variables in an unprotected airway. We studied 41 adults (ASA status I-II) in a prospective, randomized, crossover design with both devices during the induction of anesthesia. Respiratory variables were measured with a pulmonary monitor (CP-100). Pressure-controlled mask ventilation versus circle system ventilation resulted in lower (mean +/- SD) peak airway pressures (10.6 +/- 1.5 cm H(2)O versus 14.4 +/- 2.4 cm H(2)O; P < 0.001), delta airway pressures (8.5 +/- 1.5 cm H(2)O versus 11.9 +/- 2.3 cm H(2)O; P < 0.001), expiratory tidal volume (650 +/- 100 mL versus 680 +/- 100 mL; P = 0.001), minute ventilation (10.4 +/- 1.8 L/min versus 11.6 +/- 1.8 L/min; P < 0.001), and peak inspiratory flow rates (0.81 +/- 0.06 L/s versus 1.06 +/- 0.26 L/s; P < 0.001) but higher inspiratory time fraction (48% +/- 0.8% versus 33% +/- 7.7%; P < 0.001) and end-tidal carbon dioxide (34 +/- 3 mm Hg versus 33 +/- 4 mm Hg; not significant). We conclude that in this model of apneic patients with an unprotected airway, pressure-controlled ventilation resulted in reduced inspiratory peak flow rates and peak airway pressures when compared with circle system ventilation, thus providing an additional patient safety effect during mask ventilation.

IMPLICATIONS

In this model of apneic patients with an unprotected airway, pressure-controlled ventilation resulted in reduced inspiratory peak flow rates and lower peak airway pressures when compared with circle system ventilation, thus providing an additional patient safety effect during face-mask ventilation.

A Pilot Study to Evaluate the SMART BAG®: A New Pressure-Responsive, Gas-Flow Limiting Bag-Valve-Mask Device

Reducing inspiratory flow rate and peak airway pressure may be important to minimize the risk of stomach inflation when ventilating an unprotected airway with positive pressure ventilation. In this study, we assessed the effects of a standard self-inflating bag compared with a new pressure-responsive, inspiratory gas flow-limiting device (SMART BAG) on respiratory mechanics in 60 adult patients undergoing routine induction of anesthesia. Respiratory variables were measured using a pulmonary monitor. The SMART BAG resulted in significantly decreased inspiratory flow rate and peak airway pressure while providing adequate tidal volume delivery.

IMPLICATIONS

The SMART BAG, a new pressure-responsive, peak inspiratory gas flow-limiting bag-valve mask device, limits inspiratory gas flow from up to 120 L/min in a standard self-inflating bag to approximately 40 L/min. It is designed for use by all levels of health care professionals and has been proven in a clinical pilot study to effectively ventilate patients in respiratory arrest.

The effects of nifedipine on ventricular fibrillation mean frequency in a porcine model of prolonged cardiopulmonary resuscitation

We assessed the effects of a calcium channel blocker versus saline placebo on ventricular fibrillation mean frequency and hemodynamic variables during prolonged cardiopulmonary resuscitation (CPR). Before cardiac arrest, 10 animals were randomly assigned to receive either nifedipine (0.64 mg/kg; n = 5) or saline placebo (n = 5) over 10 min. Immediately after drug administration, ventricular fibrillation was induced. After 4 min of cardiac arrest and 18 min of basic life support CPR, defibrillation was attempted. Ninety seconds after the induction of cardiac arrest, ventricular fibrillation mean frequency was significantly (P < 0.01) increased in nifedipine versus placebo pigs (mean +/- SD: 12.4 +/- 2.1 Hz versus 8 +/- 0.7 Hz). From 2 to 18.5 min after the induction of cardiac arrest, no differences in ventricular fibrillation mean frequency were detected between groups. Before defibrillation, ventricular fibrillation mean frequency was significantly (P < 0.05) increased in nifedipine versus placebo animals (9.7 +/- 1.2 Hz versus 7.1 +/- 1.3 Hz). Coronary perfusion pressure was significantly lower in the nifedipine than in the placebo group from the induction of ventricular fibrillation to 11.5 min of cardiac arrest; no animal had a return of spontaneous circulation after defibrillation. In conclusion, nifedipine, but not saline placebo, prevented a rapid decrease of ventricular fibrillation mean frequency after the induction of cardiac arrest and maintained ventricular fibrillation mean frequency at approximately 10 Hz during prolonged CPR; this was nevertheless associated with no defibrillation success.

IMPLICATIONS

This study evaluates the effects of a calcium channel blocker on ventricular fibrillation mean frequency, hemodynamic variables, and resuscitability during prolonged cardiopulmonary resuscitation (CPR) in pigs. Nifedipine, but not saline placebo, prevented a rapid decrease of ventricular fibrillation mean frequency after the induction of cardiac arrest and maintained ventricular fibrillation mean frequency at approximately 10 Hz during prolonged CPR but did not improve resuscitability.

Revisiting the cardiac versus thoracic pump mechanism during cardiopulmonary resuscitation

The mechanism of forward blood flow due to external chest compressions during cardiopulmonary resuscitation (CPR) remains controversial, with the main theories being based on either a cardiac, or thoracic pump mechanism. Both potential mechanisms are well investigated by echocardiographic assessment. In the present case, a postoperative complication of cardiac tamponade that was detected by a thoracoabdominal CT-scan, led to cardiac arrest with subsequent successful CPR over 15 min until definitive surgical management was performed. This observation suggests that the thoracic pump mechanism may have been the predominant mechanism of forward blood flow in the present case of a pericardial tamponade.

Survival with full neurologic recovery after prolonged cardiopulmonary resuscitation with a combination of vasopressin and epinephrine in pigs

We sought to determine the effects of a combination of vasopressin and epinephrine on neurologic recovery in comparison with epinephrine alone and saline placebo alone in an established porcine model of prolonged cardiopulmonary resuscitation (CPR). After 4 min of cardiac arrest, followed by 3 min of basic life support CPR, 17 animals were randomly assigned to receive, every 5 min, either a combination of vasopressin and epinephrine (vasopressin [IU/kg]/epinephrine [ micro g/kg]: 0.4/45, 0.4/45, and 0.8/45; n = 6), epinephrine alone (45, 45, and 200 micro g/kg; n = 6), or saline placebo alone (n = 5). After 22 min of cardiac arrest, including 18 min of CPR, defibrillation was attempted to achieve the return of spontaneous circulation. Aortic diastolic pressure was significantly (P < 0.01) increased 90 s after each of 3 vasopressin/epinephrine injections versus epinephrine alone versus saline placebo alone (mean +/- SEM: 69 +/- 3 mm Hg versus 45 +/- 3 mm Hg versus 29 +/- 2 mm Hg, 63 +/- 4 mm Hg versus 27 +/- 3 mm Hg versus 23 +/- 1 mm Hg, and 52 +/- 4 mm Hg versus 21 +/- 3 mm Hg versus 16 +/- 3 mm Hg, respectively). Spontaneous circulation was restored in six of six vasopressin/epinephrine pigs, whereas six of six epinephrine and five of five saline placebo pigs died (P < 0.01). Neurologic evaluation 24 h after successful resuscitation revealed only an unsteady gait and was normal 5 days after the experiment in all vasopressin/epinephrine-treated animals. In conclusion, in this porcine model of prolonged CPR, repeated vasopressin/epinephrine administration, but not epinephrine or saline placebo alone, ensured long-term survival with full neurologic recovery.

IMPLICATIONS

We present a study to evaluate the effects of a combination of vasopressin and epinephrine during prolonged cardiopulmonary resuscitation on neurological outcome in pigs. We found that all pigs treated with a combination of vasopressin and epinephrine could be resuscitated and had full neurologic recovery observed over an entire period of 5 days.

Decreasing peak flow rate with a new bag-valve-mask device: effects on respiratory mechanics, and gas distribution in a bench model of an unprotected airway

Reducing inspiratory flow rate and peak airway pressure may be important in order to minimise the risk of stomach inflation when ventilating an unprotected airway with positive pressure ventilation. The purpose of this study was to assess the effects of a newly developed bag-valve-mask device (SMART BAG), O-Two Systems International, Ont., Canada) that limits peak inspiratory flow. A bench model simulating a patient with an unintubated airway was used consisting of a face mask, manikin head, training lung (lung compliance, 100 ml/cm H(2)O, airway resistance 4 cm H(2)O/l/s, lower oesophageal sphincter pressure 20 cm H(2)O and simulated stomach). Twenty nurses were randomised to each ventilate the manikin using a standard single person technique for 1 min (respiratory rate, 12/min) with either a standard adult self-inflating bag, or the SMART BAG. The volunteers were blinded to the experimental design of the model until completion of the experimental protocol. The SMART BAG vs. standard self-inflating bag resulted in significantly (P<0.05) lower mean+/-S.D. peak inspiratory flow rates (32+/-2 vs. 61+/-13 l/min), peak inspiratory pressure (12+/-2 vs. 17+/-2 cm H(2)O), lung tidal volumes (525+/-111 vs. 680+/-154 ml) and stomach tidal volumes (0+/-0 vs. 17+/-36 ml), longer inspiratory times (1.9+/-0.3 vs. 1.5+/-0.3 s), but significantly higher mask leakage (26+/-13 vs. 14+/-8%); mask tidal volumes (700+/-104 vs. 785+/-172 ml) were comparable. The mask leakage observed is not an uncommon factor in bag-valve-mask ventilation with leakage fractions of 25-40% having been previously reported. The differences observed between the standard BVM and the SMART BAG are due more to the anatomical design of the mask and the non-anatomical shape of the manikin face than the function of the device. Future studies should remove the mask to manikin interface and should introduce a standardized mask leakage fraction. The use of a two-person technique may have removed the problem of mask leakage. In conclusion, using the SMART BAG during simulated ventilation of an unintubated patient in respiratory arrest significantly decreased inspiratory flow rate, peak inspiratory pressure, stomach tidal volume, and resulted in a significantly longer inspiratory time when compared to a standard self-inflating bag.

Arginine vasopressin, but not epinephrine, improves survival in uncontrolled hemorrhagic shock after liver trauma in pigs

OBJECTIVE

Epinephrine is widely used for treatment of life-threatening hypotension, although new vasopressor drugs may merit evaluation. The purpose of this study was to determine the effects of vasopressin vs. epinephrine vs. saline placebo on hemodynamic variables, regional blood flow, and short-term survival in an animal model of uncontrolled hemorrhagic shock and delayed fluid resuscitation.

DESIGN

Prospective, randomized, laboratory investigation that used a porcine model for measurement of hemodynamic variables and regional abdominal organ blood flow.

SETTING

University hospital laboratory.

SUBJECTS

A total of 21 pigs weighing 32 +/- 3 kg.

INTERVENTIONS

The anesthetized pigs were subjected to a penetrating liver injury, which resulted in a mean +/- sem loss of 40% +/- 5% of estimated whole blood volume within 30 mins and mean arterial pressures of <20 mm Hg. When heart rate declined progressively, pigs randomly received a bolus dose and continuous infusion of either vasopressin (0.4 units/kg and 0.04 units.kg-1.min-1, n = 7), or epinephrine (45 microg/kg and 5 microg.kg(-1).min(-1), n = 7), or an equal volume of saline placebo (n = 7), respectively. At 30 mins after drug administration, all surviving animals were fluid resuscitated while bleeding was surgically controlled.

MEASUREMENTS AND MAIN RESULTS

Mean +/- sem arterial blood pressure at 2.5 and 10 mins was significantly (p <.001) higher after vasopressin vs. epinephrine vs. saline placebo (82 +/- 14 vs. 23 +/- 4 vs. 11 +/- 3 mm Hg, and 42 +/- 4 vs. 10 +/- 5 vs. 6 +/- 3 mm Hg, respectively). Although portal vein blood flow was temporarily impaired by vasopressin, it was subsequently restored and significantly (p <.01) higher when compared with epinephrine or saline placebo (9 +/- 5 vs. 121 +/- 3 vs. 54 +/- 22 mL/min and 150 +/- 20 vs. 31 +/- 17 vs. 0 +/- 0 mL/min, respectively). Hepatic and renal artery blood flow was significantly higher throughout the study in the vasopressin group; however, no further bleeding was observed. Despite a second bolus dose, all epinephrine- and saline placebo-treated animals died within 15 mins after drug administration. By contrast, seven of seven vasopressin-treated animals survived until fluid replacement, and 60 mins thereafter, without further vasopressor therapy (p <.01). Moreover, blood flow to liver, gut, and kidney returned to normal values in the postshock phase.

CONCLUSIONS

Vasopressin, but not epinephrine or saline placebo, improved short-term survival in a porcine model of uncontrolled hemorrhagic shock after liver injury when surgical intervention and fluid replacement was delayed.

Feasibility and effects of transcutaneous phrenic nerve stimulation combined with an inspiratory impedance threshold in a pig model of hemorrhagic shock

OBJECTIVE

Intrathoracic pressure changes are of particular importance under hypovolemic conditions, especially when central venous blood pressure is critically low. Accordingly, the purpose of this study was to assess the feasibility of transcutaneous phrenic nerve stimulation, used in conjunction with an inspiratory impedance threshold, on hemodynamic variables during hemorrhagic shock.

DESIGN

Prospective, randomized laboratory investigation using a porcine model for measurement of hemodynamic variables, left and right ventricular diameter, and transmitral, transpulmonary, and transaortic blood flow employing transesophageal echo-Doppler technique.

SETTING

University hospital laboratory.

SUBJECTS

Thirteen female pigs weighing 28-36 kg.

INTERVENTIONS

The anesthetized pigs were subjected to profound hemorrhagic shock by withdrawal of 55% of estimated blood volume over 20 mins. After a 10-min recovery period, the diaphragm was stimulated with a prototype transcutaneous phrenic nerve stimulator at a rate of ten per minute while the airway was intermittently occluded with an inspiratory threshold valve between positive pressure ventilations. Hemodynamic variables were monitored for 30 mins.

MEASUREMENTS AND MAIN RESULTS

Phrenic nerve stimulation in combination with the inspiratory threshold valve significantly (p <.001) improved right and left ventricular diameter compared with hypovolemic shock values by 34 +/- 2.5% and 20 +/- 2.5%, respectively. Moreover, phrenic nerve stimulation together with the inspiratory threshold valve also increased transaortic, transpulmonary, and transmitral valve blood flow by 48 +/- 6.6%, 67 +/- 13.3, and 43 +/- 8.2%, respectively (p <.001 for comparisons within group). Mean +/- sem coronary perfusion and systolic aortic blood pressures were also significantly (p <.001) higher compared with values before stimulation (30 +/- 2 vs. 20 +/- 2 mm Hg, and 37 +/- 2 vs. 32 +/- 3 mm Hg, respectively).

CONCLUSIONS

This feasibility study suggests that phrenic nerve stimulation with the inspiratory threshold valve may improve cardiac preload and, subsequently, key hemodynamic variables in porcine model of severe hemorrhagic shock.

Vasopressin, but not fluid resuscitation, enhances survival in a liver trauma model with uncontrolled and otherwise lethal hemorrhagic shock in pigs

BACKGROUND

The authors compared the effects of vasopressin fluid resuscitation on survival in a liver trauma model with uncontrolled and otherwise lethal hemorrhagic shock in pigs.

METHODS

A midline laparotomy was performed on 23 domestic pigs, followed by an incision, and subsequent finger fraction across the right medial liver lobe. During hemorrhagic shock, animals were randomly assigned to receive either 0.4 U/kg vasopressin (n = 9), or fluid resuscitation (n = 7), or saline placebo (n = 7), respectively. A continuous infusion of 0.08 U x kg(-1) x min(-1) vasopressin in the vasopressin group, or normal saline was subsequently administered in the fluid resuscitation and saline placebo group, respectively. After 30 min of experimental therapy, bleeding was controlled by surgical intervention, and blood transfusion and rapid fluid infusion were subsequently performed.

RESULTS

Maximum mean arterial blood pressure during experimental therapy in the vasopressin-treated animals was significantly higher than in the fluid resuscitation and saline placebo groups (mean +/- SD, 72 +/- 26 vs 38 +/- 16 vs 11 +/- 7 mmHg, respectively; P< 0.05). Subsequently, mean arterial blood pressure remained at approximately 40 mmHg in all vasopressin-treated animals, whereas mean arterial blood pressure in all fluid resuscitation and saline placebo pigs was close to aortic hydrostatic pressure (approximately 15 mmHg) within approximately 20 min of experimental therapy initiation. Total blood loss was significantly higher in the fluid resuscitation pigs compared with vasopressin or saline placebo after 10 min of experimental therapy (65 +/- 6 vs 42 +/- 4 vs 43 +/- 6 ml/kg, respectively; P< 0.05). Seven of seven fluid resuscitation, and seven of seven saline placebo pigs died within approximately 20 min of experimental therapy, while 8 of 9 vasopressin animals survived more than 7 days (P < 0.05).

CONCLUSIONS

Vasopressin, but not fluid resuscitation or saline placebo, ensured survival with full recovery in this liver trauma model with uncontrolled and otherwise lethal hemorrhagic shock in pigs.

Optimizing bag-valve-mask ventilation with a new mouth-to-bag resuscitator

When ventilating an unintubated patient with a self-inflating bag, high peak inspiratory flow rates may result in high peak airway pressure with subsequent stomach inflation; this may occur frequently when rescuers without daily experience in bag-valve-mask ventilation need to perform advanced airway management. The purpose of this study was to assess the effects of a newly developed self-inflating bag (mouth-to-bag resuscitator; Ambu, Glostrup, Denmark) that limits peak inspiratory flow. A bench model simulating a patient with an unintubated airway was used, consisting of a face mask, manikin head, training lung (lung compliance, 100 ml/0.098 kPa (100 ml/cm H(2)O)); airway resistance, 0.39 kPa/l per second (4 cm H(2)O/l/s), oesophagus (LESP, 1.96 kPa (20 cm H(2)O)) and simulated stomach. Twenty nurses were randomised to ventilate the manikin for 1 min (respiratory rate: 12 per minute) with either a standard self-inflating bag or the mouth-to-bag resuscitator, which requires the rescuer to blow up a single-use balloon inside the self-inflating bag, which in turns displaces air towards the patient. When supplemental oxygen is added, ventilation with up to 100% oxygen may be obtained, since expired air is only used as the driving gas. The mouth-to-bag resuscitator therefore allows two instead of one hand sealing the mask on the patient's face. The volunteers were blinded to the experimental design of the model until completion of the experimental protocol. The mouth-to-bag resuscitator versus standard self-inflating bag resulted in significantly (P<0.05) higher mean+/-S.D. mask tidal volumes (1048+/-161 vs. 785+/-174 ml) and lung tidal volumes (911+/-148 vs. 678+/-157 ml), longer inspiratory times (1.7+/-0.4 vs. 1.4+/-0.4 s), but significantly lower peak inspiratory flow rates (50+/-9 vs. 62+/-13 l/min) and mask leakage (10+/-4 vs. 15+/-9%); peak inspiratory pressure (17+/-2 vs. 17+/-2 cm H(2)O) and stomach tidal volumes (16+/-30 vs. 18+/-35 ml) were comparable. In conclusion, employing the mouth-to-bag resuscitator during simulated ventilation of an unintubated patient in respiratory arrest significantly decreased inspiratory flow rate and improved lung tidal volumes, while decreasing mask leakage.