Andrew Weatherall

Feasibility of cerebral near-infrared spectroscopy monitoring in the pre-hospital environment.

Traumatic brain injury (TBI) is a significant cause of death and severe disability from trauma. Pre‐hospital care of patients with TBI may be aided by non‐invasive monitoring of cerebral tissue oxygenation. This pilot observational study was designed to assess if cerebral tissue oximetry using near‐infrared spectroscopy (NIRS) is feasible in the pre‐hospital and transport environment.

Physician staffed helicopter emergency medical service dispatch via centralised control or directly by crew – case identification rates and effect on the Sydney paediatric trauma system

BackgroundSevere paediatric trauma patients benefit from direct transport to dedicated Paediatric Trauma Centres (PTC). Parallel case identification systems utilising paramedics from a centralised dispatch centre versus the crew of a physician staffed Helicopter Emergency Medical Service (HEMS) allowed comparison of the two systems for case identification rates and subsequent timeliness of direct transfer to a PTC.MethodsPaediatric trauma patients over a two year period from the Sydney region with an Injury Severity Score (ISS) > 15 were retrospectively identified from a state wide trauma registry. Overall paediatric trauma system performance was assessed by comparisons of the availability of the physician staffed HEMS for patient characteristics, transport mode (direct versus indirect) and the times required for the patient to arrive at the paediatric trauma centre. The proportion of patients transported directly to a PTC was compared between the times that the HEMS service was available versus the time that it was unavailable to determine if the HEMS system altered the rate of direct transport to a PTC. Analysis of variance was used to compare the identifying systems for various patient characteristics when the HEMS was available.ResultsNinety nine cases met the inclusion criteria, 44 when the HEMS system was operational. Patients identified for physician response by the HEMS system were significantly different to those that were not identified with higher median ISS (25 vs 18, p = 0.011), and shorter times to PTC (67 vs 261mins, p = 0.015) and length of intensive care unit stays (2 vs 0 days, p = 0.045). Of the 44 cases, 21 were not identified, 3 were identified by the paramedic system and 20 were identified by the HEMS system, (P < 0.001). Direct transport to a PTC was more likely to occur when the HEMS dispatch system was available (RR 1.81, 95% CI 1.20-2.73). The median time (minutes) to arrival at the PTC was shorter when HEMS available (HEMS available 92, IQR 50-261 versus HEMS unavailable 296, IQR 84-583, P < 0.01).ConclusionsPhysician staffed HEMS crew dispatch is significantly more likely to identify cases of severe paediatric trauma and is associated with a greater proportion of transports directly to a PTC and with faster times to arrival.

Prehospital paediatric emergencies treated by an Australian helicopter emergency medical service

Objectives The aim of this study was to describe the mechanism and severity of injuries in the paediatric population treated by an Australian helicopter emergency medical service and to examine the frequency and nature of interventions performed. This information is important for planning education and continuing professional development in prehospital medicine. Methods The study is a retrospective cohort analysis of 349 patients under the age of 16 treated by CareFlight in Sydney, Australia, between April 2007 and April 2012. Data collected included age, type of incident, medication and fluid administered, procedures performed, receiving hospital, 24 h and 30-day mortality and injuries sustained. Results Falls (33%), motor vehicle incidents (30%), sport injury (14%) and immersion injury (12%) were the most common mechanisms. A total of 27 children died within 30 days; nontrauma cases were proportionally overrepresented in the deaths. With respect to tasking, 59% cases involved a severely or significantly injured child. Among the children, 97% with a traumatic mechanism were transferred directly to a paediatric trauma centre. In addition, 81% of children had at least one intervention by the helicopter emergency medical services team at the incident scene, most commonly intravenous cannulation (61%), crystalloid bolus (29%), intubation (21%) and intravenous analgesia administration (15%). Conclusion Paediatric prehospital patients can be of high dependency, requiring urgent critical care procedures. Training in prehospital medicine should include paediatrics. It is essential that practitioners maintain skills in venous access, airway management and provision of adequate analgesia in children.

Delayed sequence intubation for management of respiratory failure in a 6-year-old child in a paediatric emergency department.

Dear Editor, Delayed sequence intubation (DSI) has been reported as a new concept to improve peri-intubation safety. Procedural sedation is used to optimise preoxygenation before intubation in agitated or combative patients intolerant of preoxygenation by traditional means. Little published evidence exists of the use of DSI in children. A 6-year-old boy with rapid-onset obesity (73 kg, body mass index >40), hypothalamic dysfunction (adrenal insufficiency), hypoventilation and autonomic dysregulation syndrome presented to our paediatric ED (PED) with severe respiratory failure, with hypoxaemia (SpO2 55% on pulse oximetry on room air), hypercarbia and respiratory acidosis (pH 7.26, pCO2 79 mmHg on venous blood gas analysis). Respiratory rate was 21/ min. He was tachycardic (142/min), hypertensive (134/68 mmHg) and pyrexial (38.6°C); GCS was E2M4V4, but the patient was agitated and combative, not tolerating oxygenation via non-rebreather face mask or noninvasive ventilation (NIV) via face or nasal mask; we decided to intubate. As our severely hypoxaemic patient was at high risk for reduced safe apnoea phase and peri-intubation arrest, the need for sedation to provide adequate preoxygenation was evident. We proceeded with DSI; 0.2 mg/kg of ketamine i.v. produced rapid dissociation, allowing application of face mask NIV via LTV® 1200 Series ventilator (CareFusion, Seven Hills, NSW, Australia). SpO2 improved within 3 min to 95% in 90% FiO2. Further ketamine boluses (0.15–0.2 mg/kg), totalling 0.7 mg/kg, maintained sedation until senior anaesthetic staff were present. Despite 21 min of appropriately applied NIV, respiratory acidosis had deteriorated (pH 7.15, CO2 106 mmHg). For intubation, thiopentone 2 mg/kg and suxamethonium 2 mg/kg was given. A CMAC® size 3 videolaryngoscope (Karl Storz, Tuttlingen, Germany) provided a grade I Cormac/Lehane view with external laryngeal manipulation; the trachea was intubated with a bougie and 6.0 cuffed ETT on first pass. Desaturation to 68% occurred immediately post-intubation, requiring bag-valve-mask ventilation, positive end-expiratory pressure and 90% O2 with prompt normalisation of SpO2 to 100%. No bradycardia or hypotension occurred throughout. Postintubation sedation was maintained with morphine and midazolam infusions with vecuronium as further muscle relaxation before transfer to the paediatric ICU. We illustrate the successful use of DSI in a child. Ketamine has been described as the initial induction agent of choice to maintain haemodynamics, airway reflexes and respiratory drive. In the present case, small doses provided sufficient sedation, haemodynamic stability and maintenance of respiratory drive during preoxygenation. Other suggested induction agents, including dexmedetomidine and remifentanil, are not routinely available in many PEDs. We chose suxamethonium as the traditional muscle relaxant, whereas rocuronium, not causing additional oxygen consumption by fasciculations, has been suggested by some authors. We utilised gentle NIV up to, during and beyond the phase of muscle paralysis until immediately before ETT insertion and no adverse events occurred. Traditional RSI teaching (to stop bagging as soon as apnoea occurs, to avoid pulmonary aspiration of gastric contents) might be erroneous. Gentle bagging throughout the RSI process might optimise oxygenation. We did not employ ‘apnoeic oxygenation’, continuous nasal prong oxygenation at 15 L/min, also espoused by Weingart and Levitan before intubation, as this has only recently been introduced in our ED. It would have been an ideal adjunct for extending the safe apnoeic phase in our patient and should be routinely performed in all ED tracheal intubations, especially in children. Our case demonstrates the benefits of video laryngoscopy for initial high-grade laryngeal visualisation, effective external laryngeal manipulation and increased confidence of all team members that the ETT has passed through the cords. Further studies need to examine the benefits and safety of DSI in children, who are at greater risk for apnoea-associated desaturation during emergent intubation, the role of passive apnoeic oxygenation and different muscle relaxants in DSI.

Performance comparison of improvised prehospital blood warming techniques and a commercial blood warmer.

INTRODUCTION Prehospital transfusion of packed red blood cells (PRBC) may be life saving for hypovolaemic trauma patients. PRBCs should preferably be warmed prior to administration but practical prehospital devices have only recently become available. The effectiveness of purpose designed prehospital warmers compared with previously used improvised methods of warming has not previously been described. MATERIALS AND METHODS Expired units of PRBCs were randomly assigned to a warming method in a bench study. Warming methods were exposure to body heat of an investigator, leaving the blood in direct sunlight on a dark material, wrapping the giving set around gel heat pads or a commercial fluid warmer (Belmont Buddy Lite). Methods were compared with control units that were run through the fluid circuit with no active warming strategy. RESULTS The mean temperature was similar for all methods on removal from the fridge (4.5°C). The mean temperatures (degrees centigrade) for all methods were higher than the control group at the end of the circuit (all P≤0.001). For each method the mean (95% CI) temperature at the end of the circuit was; body heat 17.2 (16.4-18.0), exposure to sunlight 20.2 (19.4-21.0), gel heat pads 18.8 (18.0-19.6), Buddy Lite 35.2 (34.5-36.0) and control group 14.7 (13.9-15.5). CONCLUSIONS All of the warming methods significantly warmed the blood but only the Buddy Lite reliably warmed the blood to a near normal physiological level. Improvised warming methods therefore cannot be recommended.

Study protocol for the PHANTOM study: prehospital assessment of noninvasive tissue oximetry monitoring

BackgroundTraumatic brain injury is a major cause of mortality and morbidity worldwide. It can be worsened by secondary injury particularly with hypoxia or hypotension. Current prehospital guidelines emphasise regular measurement of peripheral oxygen saturation and blood pressure but there is no monitor in use to provide direct information relating to blood flow or oxygen delivery to the brain tissue. This prospective cohort study will assess the utility of near-infrared spectroscopy monitoring in prehospital medicine in demonstrating injury, pathophysiology and associations with long-term functional outcomes.Methods/designA prospective cohort study will be conducted in prehospital services where physician/paramedic teams respond rapidly to patients suffering significant traumatic injuries. A study observer accompanying the clinical team will apply non-invasive near-infrared spectroscopy tissue oximetry using a Nonin EQUANOX 7610 Regional Oximetry monitor (TM Nonin Medical, Inc.). This will be applied to patients with traumatic injuries less than 30 minutes old requiring transport. Measurements will be taken at two sites on the forehead and one on the forearm. Clinical teams will be blinded to all monitoring values. Near-infrared spectroscopy tissue oximetry parameters of oxyhaemoglobin%, deoxyhaemoglobin%, total tissue haemoglobin index and regional oxygen saturation will be recorded. Separate statistical analysis relating to time spent with cerebral regional oxygen saturation values < 45% and time series analysis will be performed to demonstrate associations with acute phase outcomes including injuries seen on cerebral imaging, and long-term functional outcomes measured by Glasgow Outcome Score and Extended Glasgow Outcome Score will then be undertaken.DiscussionThis prospective cohort study will demonstrate associations evident from the earliest stages of prehospital treatment between near-infrared spectroscopy tissue oximetry values and both acute and long-term outcomes of patients suffering traumatic injuries. This may provide the basis for future interventional studies utilising near-infrared spectroscopy tissue oximetry to guide prehospital trauma care.Trial registrationThis trial is registered with the Australian and New Zealand Clinical Trials Registry. The registration number is ACTRN12611001124921.

Continuing stories with discontinuity

When he broke the big news of anesthesia in the Ether Dome in 1846, William Morton probably did not think much about how you are supposed to tell a story. He did not start at the beginning with a carefully crafted tale including all of the characteristics of his miraculous lead character. He landed somewhere right in the middle with an agent that produced this amazing state of anesthesia and leaving others to try to work out the story in reverse. In this edition of the journal, we return to Boston as Cornelissen et al. report their work trying to provide some of the backstory by looking at the electroencephalogram (EEG) in infants undergoing anesthesia. More than 150 years later we are still firmly in the part of the story where there are more mysteries than certainties. In a follow-up analysis of data collected in an observational study (1) to explore age-dependent EEG patterns during sevoflurane anesthesia, the authors examined discontinuity events where there is a period of low amplitude activity lasting over 2 s across the cerebrum. Such discontinuity events are a background feature in the healthy premature infant during sleep–wake cycling but gradually leave the normal background of the EEG by term. Their presence in the awake sate by that age is abnormal and might be associated with critical illnesses like encephalopathy or complex heart disease. In this group of children between 0 and 40 months of age, they found that discontinuity events occurred during anesthesia in more than half of the patients studied. Such events were especially frequent in younger infants, in the first 30 min of anesthesia, and seemed to occur more often with higher concentrations of sevoflurane. These events may therefore be a marker of the ‘overanesthetized brain’. Discontinuity events are not a new finding in pediatric anesthesia. Davidson et al. have previously shown such events primarily during emergence rather than at higher volatile concentrations (2). However, Cornelissen et al. saw no cases of discontinuity during emergence. The reason for this discrepancy is not yet part of the story. Of course because anesthesia started with a demonstration aimed at producing a state where awareness and mobility during surgery were minimized, our practice was immediately influenced by these coupled goals even though they are separate things. Achieving immobility tends to require delivery of higher concentrations of volatile agent than those required for anesthesia. Now we have some new bits of information hinting at the possibility that we might be ‘overanesthetizing the brain’. What should the clinician do with this new knowledge? Are we looking at a biomarker of damage, a normal feature of anesthesia, or a complex mix of both? Discontinuity events may be associated with encephalopathy or adverse neurological outcomes in congenital heart disease. However, those are very distinct pathological states that produce their own disturbances when it comes to the brain. Is each unhappy cortex unhappy in its own way, or are they all alike? Could forms of discontinuity on the EEG be a different marker suggesting a risk of postoperative neurological issues after general anesthesia as has been suggested in some adult settings? That is a reasonable concern but in adult studies where some form of link has been suggested, the EEG did not just show discontinuity events but a distinctly different pattern of burst suppression (3). Maybe the EEG is trying to remind us that kids are not just little adults, particularly in neonates and infants, where the normal pattern of EEG activity is itself changing as the brain matures and develops. If a degree of discontinuity is part of normal brain maturation that resolves by term perhaps transient discontinuity events (as seen here and with use of barbiturates and some antiepileptics) are of minimal neurodevelopmental significance. So rigorous research such as this provides interesting new parts of the backstory of Morton’s miraculous character but there are many gaps to fill in. Some of those are not in the field of EEG monitoring, and may include areas such as cerebral perfusion, individual differences between anesthetic agents, and developmental neurology. The full story requires more information about the potential for neurodevelopmental impacts of anesthesia, although the most recent publications around neurotoxicity seem somewhat more reassuring than earlier animal work (4,5). We also need long-term follow-up of patients included in EEG research and work to establish if observed patterns are meaningfully associated with clinical outcomes for patients rather than being interesting monitoring artifacts. Then it might just be possible to start working out the link between the agents we use, the effects on the EEG with its suppressed bursts, pauses, waves, and oscillations, and the outcomes for the patient. William T. G. Morton may have introduced a very interesting character all that time ago but he did not