The Use of Quantitative End-Tidal Capnometry to Avoid Inadvertent Severe Hyperventilation in Patients With Head Injury After Paramedic Rapid Sequence Intubation

End tidal carbon dioxide monitoring in prehospital and retrieval medicine: a review

End tidal carbon dioxide (ETCO2) monitoring is the non-invasive measurement of exhaled CO2. The Intensive Care Society guidelines include (ETCO2) monitoring as one of the objective standards required for monitoring patients in transport, and the American Heart Association recommends that all intubations must be confirmed by some form of ETCO2 measurement. The physiological principles and technology underlying ETCO2 measurement and the clinical indication for its use in the prehospital environment are reviewed. ETCO2 monitoring has been widely established in the prehospital environment and is of particular use for verification of endotracheal tube placement. It is non-invasive and easy to apply to breathing circuits. The units now available are compact and rugged, with extended battery operating times, which are ideally suited for prehospital use and should be considered as an essential item for advanced airway management.

The impact of prehospital ventilation on outcome after severe traumatic brain injury

BACKGROUND

Prehospital intubation has been challenged on the grounds that it predisposes to hyperventilation, which is detrimental after traumatic brain injury (TBI), and impairs venous return in patients with hypovolemia. We sought to determine the incidence of hyperventilation among a cohort of trauma patients undergoing prehospital intubation and the impact of ventilation on outcome after severe TBI.

METHODS

Data were prospectively collected for all intubated trauma patients transported directly from the field for a period of 14 months (n = 574). An arrival Pco2 <30 mm Hg was termed severe hypocapnea and considered a marker of hyperventilation. Patients with a Pco2 >45 mm Hg were considered severely hypercapneic. Targeted ventilation was defined as a Pco2 between 30 and 35 mm Hg based on the Brain Trauma Foundation guidelines.

RESULTS

The rate of severe hypocapnea was 18% and women were more likely to be hyperventilated (p < 0.05). Patients with severe hypercapnia had higher Injury Severity Scores and were more likely hypotensive, hypoxic, and acidodic (p < 0.05). Patients in the targeted ventilation range were less likely to die than were those outside the range even after excluding the severe hypercapnea group (odds ratio, 0.57; 95% confidence interval, 0.33-0.99). This effect was even greater among patients with isolated TBI (odds ratio, 0.31; 95% confidence interval, 0.10-0.96).

CONCLUSION

Targeted prehospital ventilation is associated with lower mortality after severe TBI.

Hyperventilation following aero-medical rapid sequence intubation may be a deliberate response to hypoxemia

BACKGROUND

Recent studies document a high incidence of hyperventilation by prehospital providers, with a potentially detrimental effect on outcome in traumatic brain injury (TBI).

PURPOSE

To document the incidence of hyperventilation by aero-medical providers and explore a possible relationship between hyperventilation episodes and desaturations or impending hypoxemia.

METHODS

This was a prospective, descriptive study using TBI patients undergoing prehospital RSI by aero-medical crews. Continuous data regarding end-tidal CO2 (EtCO2), ventilatory rate, and oxygen saturation (SpO2) were downloaded from hand-held oximeter-capnometer devices. Two investigators independently assessed oximetry/capnometry data to identify the following occurrences: desaturation during RSI (SpO2 < 90%), impending hypoxemia (SpO2 decrease by >or=3% to a value <95%) following intubation, loss of SpO2 signal, hyperventilation (EtCO2<30 mm Hg), and severe hyperventilation (EtCO2 < 25 mm Hg). Covariate analysis was used to explore the possible association between hyperventilation episodes and either desaturation, impending hypoxemia, or loss of SpO2 signal.

RESULTS

A total of 32 aero-medical patients were enrolled with a mean duration of ventilation monitoring of 14.8 min. The incidence of hyperventilation or severe hyperventilation was substantially lower than previously documented with ground paramedics. A total of 28 hyperventilation episodes were identified in 16 patients; 13 of these were associated with impending hypoxemia following intubation, five were associated with desaturation during RSI, and seven were associated with loss of SpO2 signal. The remaining three occurred immediately following intubation without desaturation during RSI. Desaturation was observed in 62% of patients; of note, desaturation was recorded on the quality improvement document in only 23% of these. Covariate analysis revealed an association between hyperventilation episodes and either desaturatios during RSI, impending hypoxemia following intubation, or loss of SpO2 signal.

CONCLUSIONS

The incidence of hyperventilation by aeromedical crews was lower than reported for ground paramedics and appears to occur in response to desaturation, impending hypoxemia, or loss of SpO2 signal.

Traumatic brain injury: assessment, resuscitation and early management

This review examines the evidence base for the early management of head-injured patients. Traumatic brain injury (TBI) is common, carries a high morbidity and mortality, and has no specific treatment. The pathology of head injury is increasingly well understood. Mechanical forces result in shearing and compression of neuronal and vascular tissue at the time of impact. A series of pathological events may then ensue leading to further brain injury. This secondary injury may be amenable to intervention and is worsened by secondary physiological insults. Various risk factors for poor outcome after TBI have been identified. Most of these are fixed at the time of injury such as age, gender, mechanism of injury, and presenting signs (Glasgow Coma Scale and pupillary signs), but some such as hypotension and hypoxia are potential areas for medical intervention. There is very little evidence positively in favour of any treatments or packages of early care; however, prompt, specialist neurocritical care is associated with improved outcome. Various drugs that target specific pathways in the pathophysiology of brain injury have been the subject of animal and human research, but, to date, none has been proved to be successful in improving outcome.

Adherence to resuscitation guidelines during prehospital care of cardiac arrest patients

OBJECTIVE

The impact of prehospital care after the return of spontaneous circulation in out-of-hospital cardiac arrest patients is not known. This study describes adherence to the resuscitation guidelines, factors associated with poor adherence and possible impact of prehospital postresuscitation care on the outcome of out-of-hospital cardiac arrest.

METHODS

One hundred and fifty-seven Finnish out-of-hospital cardiac arrest patients hospitalized during 1 year, were analyzed retrospectively. Patient and arrest characteristics, prehospital postresuscitation care and survival to hospital discharge were analyzed using multivariate logistic regression.

RESULTS

Forty percent of the patients received care accordant with the guidelines. Male sex (P=0.045), witnessed arrest (P=0.031), initial ventricular fibrillation/ventricular tachycardia rhythm (P=0.007) and the presence of an emergency physician (P=0.017) were associated with care in line with the current guidelines. In multivariate logistic regression analysis, age over median (odds ratio=3.6, 95% confidence interval 1.5-8.6), nonventricular fibrillation/ventricular tachycardia initial rhythm (odds ratio=4.0, 95% confidence interval 1.6-9.8), administration of adrenaline (odds ratio=7.0, 95% confidence interval 2.3-21.4) and unsatisfactory prehospital postresuscitation care (odds ratio=2.5, 95% confidence interval 1.1-6.3) were associated with a failure to survive up to hospital discharge.

CONCLUSIONS

Less than 50% of out-of-hospital cardiac arrest patients received prehospital postresuscitation care compatible with the current guidelines. Markers of poor prognosis were associated with unsatisfactory care, which in turn was more frequent among the patients who did not survive to hospital discharge. The importance of the guidelines should be highlighted in the future.

The Out-of-Hospital Esophageal and Endobronchial Intubations Performed by Emergency Physicians

BACKGROUND

Rapid establishment of a patent airway in ill or injured patients is a priority for prehospital rescue personnel. Out-of-hospital tracheal intubation can be challenging. Unrecognized esophageal intubation is a clinical disaster.

METHODS

We performed an observational, prospective study of consecutive patients requiring transport by air and out-of-hospital tracheal intubation, performed by primary emergency physicians to quantify the number of unrecognized esophageal and endobronchial intubations. Tracheal tube placement was verified on scene by a study physician using a combination of direct visualization, end-tidal carbon dioxide detection, esophageal detection device, and physical examination.

RESULTS

During the 5-yr study period 149 consecutive out-of-hospital tracheal intubations were performed by primary emergency physicians and subsequently evaluated by the study physicians. The mean patient age was 57.0 (+/-22.7) yr and 99 patients (66.4%) were men. The tracheal tube was determined by the study physician to have been placed in the right mainstem bronchus or esophagus in 16 (10.7%) and 10 (6.7%) patients, respectively. All esophageal intubations were detected and corrected by the study physician at the scene, but 7 of these 10 patients died within the first 24 h of treatment.

CONCLUSION

The incidence of unrecognized esophageal intubation is frequent and is associated with a high mortality rate. Esophageal intubation can be detected with end-tidal carbon dioxide monitoring and an esophageal detection device. Out-of-hospital care providers should receive continuing training in airway management, and should be provided additional confirmatory adjuncts to aid in the determination of tracheal tube placement.

Prehospital care of the injured: what's new

Emergency medical services (EMS) play a critical role in the trauma system as the point of initial patient care and stabilization and in determining the regional flow of patients and the commitment of resources to the critically injured. Trauma surgeons and emergency physicians need to be involved in the organizational planning of EMS systems to ensure that uniform patient care protocols are developed for triage and treatment. Ongoing efforts should focus on addressing national variability in care provided after injury to ensure optimal outcome for patients in all regions. Through additional research, the best practice and optimal EMS system design will continue to be defined.

Avoiding prolonged waiting time during busy periods in the emergency department: Is there a role for the senior emergency physician in triage?

STUDY OBJECTIVE

Patient satisfaction at emergency departments can be improved by reductions in waiting time. Traditional methods require registration and triage before seeing the doctor with senior emergency physicians mainly engaged in treating serious cases. We examine a radical change in workflow pattern on waiting time by placing a senior emergency physician with the triage nurse and examining the impact of treating simple cases upfront with discharge on the waiting times for stretcher cases.

METHODS

A senior emergency physician was placed with the triage nurse in the Department of Emergency Medicine at Alexandra Hospital during peak busy periods of patient attendance over a period of 2 months. Measures were made of waiting time (registration to doctor consult) of PACS 3 and PACS 2 (Patient Acvity Score) cases accordingly.

RESULTS

Ten days were chosen for the changed workflow practice and 10 days for controls in which normal traditional working practice followed. On all days, there was the same number of medical staff. The average waiting time for walk-in patients (PACS 3) was 19 min on experimental days as compared with 35.5 min on control days, with 78% being seen within 30 min in the experimental group compared with 48% on control days (P < 0.05). The PACS 2 waiting time was also significantly decreased on experimental days (P < 0.05).

CONCLUSIONS

Placing a senior emergency physician with the triage nurse reduced waiting times for walk-in cases. One third of attendances were treated and discharged quickly, allowing the consulting room and PACS 1/PACS 2 doctors to act more efficiently.

Sidestream end-tidal carbon dioxide monitoring during helicopter transport

INTRODUCTION

End-tidal carbon dioxide (EtCO(2)) monitoring is standard of care for intubated patients. Sidestream technology also allows EtCO(2) monitoring in non-intubated patients. This is the first study to evaluate the feasibility of monitoring sidestream EtCO(2) on intubated and non-intubated patients during helicopter transport.

SETTING

An air medical transport program serving two level 1 trauma centers.

METHODS

In this prospective observational study, sidestream EtCO2 was monitored in 100 consecutive patients transported by helicopter. Flight nurses rated the difficulty posed by various factors of sidestream monitoring. An experienced flight nurse and a clinical engineer evaluated waveforms and EtCO(2) values.

RESULTS

Only 1 of the 100 transported patients required a change from sidestream to mainstream EtCO(2) monitoring. Moisture was noted in the tubing of two patients, and one was changed to mainstream. Eleven patients had occluded nares but were not changed to mainstream monitoring. On a 5-point Likert scale, responses to statements regarding difficulty with length of tubing, patient tolerance, and interference with patient care produced mean scores of 0.5 (range, 0-3). Responses regarding difficulty securing the cannula yielded a mean score of 0.7 (range, 0-3). Of 1,685 (99%) recorded EtCO(2) values, 1,668 met pre-established criteria for "consistent." Alveolar plateaus were identified in 81 of 94 (86%) patient waveforms by the flight nurse and 73 of 94 (78%) patient waveforms by the clinical engineer.

CONCLUSION

Sidestream EtCO(2) monitoring is feasible during air medical transport of both intubated and non-intubated patients. The mechanism was easy to use, and consistent numeric values and waveforms with alveolar plateaus were obtained in a large majority of readings.

Prehospital Hypoxia Affects Outcome in Patients With Traumatic Brain Injury: A Prospective Multicenter Study

BACKGROUND

The goals of this study were to determine the incidence and duration of hypotension and hypoxia in the prehospital setting in patients with potentially survivable brain injuries, and to prospectively examine the association of these secondary insults with mortality and disability at hospital discharge.

METHODS

Trauma patients with suspected brain injuries underwent continuous blood pressure and pulse oximetry monitoring during helicopter transport. Postadmission inclusion criteria were (1) diagnosis of acute traumatic brain injury (TBI) confirmed by computed tomography (CT) scan, operative findings, or autopsy findings; and (2) Head Abbreviated Injury Scale (AIS) score of > or = 3 or Glasgow Coma Scale (GCS) score of < or = 12 within the first 24 hours of admission. Patients were excluded with (1) no abnormal intracranial findings on the patient's CT scan; (2) determination of a nonsurvivable injury (based on an AIS score of 6 for any body region; or, (3) death in less than 12 hours after injury. Primary outcome measures included mortality and Disability Rating Scale score at discharge.

RESULTS

We enrolled 150 patients into the study. Fifty-seven patients had at least one secondary insult; 37 had only hypoxic episodes, 14 had only hypotensive episodes, and 6 patients had both. Demographics and injury characteristics did not differ between those with and those without secondary insults. The mortality for patients without secondary insults was 20%, compared with 37% for patients with hypoxic episodes, 8% for patients with hypotensive episodes, and 24% for patients with both. The Disability Rating Scale score at discharge was significantly higher in patients with secondary insults. Using multivariate analysis, the calculated odds ratio of mortality caused by prehospital hypoxia after head injury was 2.66 (p < 0.05).

CONCLUSIONS

Secondary insults after TBI are common, and these insults are associated with disability. Hypoxia in the prehospital setting significantly increases the odds of mortality after brain injury controlled for multiple variables.

The Impact of Aeromedical Response to Patients With Moderate to Severe Traumatic Brain Injury

STUDY OBJECTIVE

Aeromedical crews offer an advanced level of practice and rapid transport to definitive care; however, their efficacy remains unproven. Previous studies have used relatively small sample sizes or have been unable to adequately control for the effect of other potentially influential variables. Here we explore the impact of aeromedical response in patients with moderate to severe traumatic brain injury.

METHODS

This was a retrospective analysis using our county trauma registry. All patients with head Abbreviated Injury Score of 3 or greater were included; interfacility transfers were excluded. The impact of aeromedical response was determined using logistic regression, adjusting for age, sex, mechanism, preadmission Glasgow Coma Scale score, head Abbreviated Injury Score, Injury Severity Score, and the presence of preadmission hypotension. Propensity scores were used to account for variability in selection of patients to undergo air versus ground transport. Patients with moderate and severe traumatic brain injury, as defined by head Abbreviated Injury Score and Glasgow Coma Scale score, were compared. Finally, aeromedical patients undergoing field intubation were compared with ground patients undergoing emergency department (ED) intubation.

RESULTS

A total of 10,314 patients meeting all inclusion and exclusion criteria and with complete data sets were identified and included 3,017 transported by aeromedical crews. Overall mortality was 25% in the air- and ground-transported cohorts, but outcomes were significantly better for the aeromedical patients when adjusted for age, sex, mechanism of injury, hypotension, Glasgow Coma Scale score, head Abbreviated Injury Score, and Injury Severity Score (adjusted odds ratio [OR] 1.90; 95% confidence interval [CI] 1.60 to 2.25; P<.0001). Good outcomes (discharge to home, jail, psychiatric facility, rehabilitation, or leaving against medical advice) were also higher in aeromedical patients (adjusted OR 1.36; 95% CI 1.18 to 1.58; P<.0001). The primary benefit appeared to be in more severely injured patients, as reflected by head Abbreviated Injury Score and Glasgow Coma Scale score. Improved survival was also observed for air-transported patients intubated in the field versus ground-transported patients given emergency intubation in the ED (adjusted OR 1.42; 95% CI 1.13 to 1.78; P<.001).

CONCLUSION

Here we analyze a large database of patients with moderate to severe traumatic brain injury. Aeromedical response appears to result in improved outcomes after adjustment for multiple influential factors in patients with moderate to severe traumatic brain injury. In addition, out-of-hospital intubation among air-transported patients resulted in better outcomes than ED intubation among ground-transported patients. Patients with more severe injuries appeared to derive the greatest benefit from aeromedical transport.

The detrimental effects of ventilation during low-blood-flow states

PURPOSE OF REVIEW

In recent years, it has become increasingly apparent that resuscitative ventilatory procedures, classically thought to be life saving, may have profound detrimental effects.

RECENT FINDINGS

Most assisted breathing techniques during resuscitation involve the provision of intermittent positive pressure ventilation to inflate lung zones for erythrocyte oxygenation and clearance of carbon dioxide. A growing number of studies involving low-flow states, however, have demonstrated that provision of overzealous (or even 'normal') ventilatory rates with intermittent positive pressure ventilation can significantly diminish both systemic and coronary circulation, most likely through inhibition of venous return. Recent laboratory studies of hemorrhage have shown not only a direct detrimental impact of each positive pressure ventilation breath on coronary perfusion, but also how dramatic improvements in blood flow can be achieved, without loss of oxygenation, by delivering breaths infrequently during such low-flow states. Likewise, in cardiac arrest models, studies have shown that interrupting chest compressions, even to provide breaths, can be extremely deleterious by abruptly (and continually) lowering the aortic pressure head to the coronary arteries, thus impairing restoration of spontaneous circulation. Even with endotracheal intubation and uninterrupted chest compressions, frequent positive pressure ventilation still inhibits circulation during cardiopulmonary resuscitation. Despite directed training, paramedics (and other rescuers) have been shown to still excessively ventilate during cardiac arrest resuscitations.

SUMMARY

Ventilation can have profound detrimental hemodynamic effects in low-flow states, exacerbating the circulatory compromise. This underappreciated confounding variable may be one of the reasons many clinical trials of resuscitative interventions have failed despite dramatic successes in the laboratory.

Capnometry in the spontaneously breathing patient

PURPOSE OF REVIEW

Capnography has been used in the operating room by anesthesiologists for over a decade. Along with pulse oximetry, it has reduced anesthesia-related morbidity and mortality. Traditionally, capnography has been used to confirm the placement of the endotracheal tube. This review looks into the literature for an update on the use of capnography in the spontaneously breathing patient.

RECENT FINDINGS

Several studies support the additional safety afforded by the use of capnography in patients undergoing sedation for procedures in various situations outside the operating room. Capnography has been used as an aid in the diagnosis of pulmonary embolism and sleep-related disorders, as a continuous monitor of metabolic status of pediatric patients with diabetic ketoacidosis and, along with pulse oximetry, in lung-function laboratories to estimate blood gases.

SUMMARY

Capnography has become a mandatory or recommended monitoring tool in the practice of anesthesiology. It is making inroads into other medical specialties as a monitoring and diagnostic tool. The use of this technology by non-anesthesiologists will continue to increase. In the opinion of the authors capnography should be used in all cases requiring sedation either in or out of the operating room.