Strength of Recommendations: Weak.
Quality of Evidence: Low, primarily from Class III studies.

Adult

1. In ground transported patients in urban environments, the routine use of paralytics to assist endotracheal intubation in patients who are spontaneously breathing, and maintaining an SpO2 above 90% on supplemental oxygen, is not recommended.

Adult and Pediatrics

1. Hypoxemia (oxygen saturation [SpO2] < 90%) should be avoided, and corrected immediately upon identification.
2. An airway should be established, by the most appropriate means available, in patients who have severe traumatic brain injury (TBI) (Glasgow Coma Scale [GCS] < 9), the inability to maintain an adequate airway, or hypoxemia not corrected by supplemental oxygen.
3. Emergency Medical Service (EMS) systems implementing endotracheal intubation protocols including the use of rapid sequence intubation (RSI) protocols should monitor blood pressure, oxygenation, and when feasible, EtCO₂.
4. When endotracheal intubation is used to establish an airway, confirmation of placement of the tube in the trachea should include lung auscultation and end-tidal CO2 (EtCO₂) determination
5. Patients should be maintained with normal breathing rates (EtCO₂ 35-40 mmHg), and hyperventilation (EtCO₂ < 35 mmHg) should be avoided unless the patient shows signs of cerebral herniation.1

Airway management and normal oxygenation in the patient with traumatic brain injury (TBI) are two of the most important management issues in the prehospital period, and have been an important research focus in prehospital care since the Guidelines47 were originally written. Key issues are management of oxygenation and ventilation, including the identification of patients who will benefit from endotracheal intubation.

Hypoxemia is a strong predictor of outcome in the TBI patient.8,25 Consequently, the primary goal in field management is assessing the airway and ensuring adequate oxygenation. Class III evidence suggests that comatoses patient with persistently low oxygen saturation despite O2 therapy benefit from intubation.40

Prehospital airway management studies relate to assessment, technique, and performance skills. These include whether endotracheal intubation skills can be taught and safely maintained by prehospital providers with minimal complications. Corollaries to this question include recognition of an esophageal intubation in the field, and the degree to which prehospital providers are able to manage difficult or failed airways. Additionally, medication adjuncts to prehospital airway intubation have been studied, as have methods of oversight, monitoring, and quality improvement processes.

These management issues are dependent upon the properly identifying the patients who need intubation. Ultimately, the goal of these studies is to ascertain the conditions in which field endotracheal intubation results in improved neurologic outcomes and decreased mortality.

For this update Medline was searched from 1996 through July 2006 using the search strategy for this question (see Appendix B), and results were supplemented with literature recommended by peers or identified from reference lists. For adult studies, of 55 potentially relevant publications, 18 were added to the existing table and used as evidence for this question. For pediatric studies, of 62 potentially relevant publications, 4 were used as evidence for this question (see Evidence Tables).

Adult

1. In ground transported patients in urban environments, the routine use of paralytics to assist endotracheal intubation in patients who are spontaneously breathing and maintaining an SpO2 >90% on supplemental oxygen is not recommended.

Foundation. Recent studies suggest that pre-hospital intubation of TBI patients may not be beneficial in patients able to maintain a SpO2 > 90% with supplemental oxygen alone.10,11,13 Studies which reported worse or equivocal outcomes in patients intubated in the field must be viewed with caution since intubated patients were usually more severely injured.3,28,37

Rapid sequence intubation (RSI), has been used in the pre-hospital setting. The use of lidocaine, fentanyl, and/or esmolol as premedication has not been demonstrated to decrease morbidity or mortality.23 There is insufficient evidence to advocate for or against the use of premedications in the field. In addition, there is little focused research on the best induction agents to employ for prehospital RSI.

A series of studies from San Diego shows an overall improvement in intubation success rate, from 39% in historical controls (non-RSI group) to approximately 85% in the study groups using RSI.12,15,29 Entry criteria in these studies were a GCS < 9 with suspected TBI, transport time from the scene to the receiving hospital > 10 minutes, and inability to intubate without RSI due to either a clenched jaw, active gag or combativeness obviating easy intubation. Study patients were then matched to historical controls who did not undergo endotracheal intubation. In this series of studies, it is not clear what fraction of patients were unable to oxygenate and/or ventilate, compared to those who were intubated out for airway protection. Thirty two percent of the patients who were intubated did not have a TBI. These studies report a higher mortality rate in the RSI group: 41% compared to 30% for those patients not intubated (O.R. 1.6; 95% C.I. 1.1-2.3) and a lower incidence of good neurologic outcome in the RSI group, 37% vs. 49% (O.R. 1.6; 95% C.I. 1.1-2.3).10,13,16 On arrival to the hospital, patients in the RSI group had severe hyperventilation (PaCO₂ < 25 mmHg) in 15% of cases compared with 8% of nonintubated controls. Patients who were not hyperventilated (PaCO₂ > 32 mmHg) had a predicted mortality of 23% and an actual mortality of 26% whereas patients with a pCO2 < 32mmHg had a predicted mortality of 27% but an actual mortality of 39%. Patients with a single intubation attempt had a higher mortality rate than patients requiring multiple attempts, as did those needing intubation en route or those whose airway was managed with a Combitube because of a failed endotracheal intubation.

Challenging the findings from San Diego is a retrospective analysis of 2,012 TBI patients from the Seattle, Washington EMS system.5 This system ensures that each paramedic performs at least 12 intubations per year or returns to the operating room for additional training. The authors of this study concluded that paralytic use improved outcome for TBI patients.However, the retrospective design of the study limits its strength. A second study also supported the prehospital use of paralytics.33 However, physicians or flight nurses performed the intubation in this study.

Thus, the safety and efficacy of RSI in the prehospital setting remains undetermined. The above studies suggest that even though RSI may improve intubation success per se, it might actually contribute to worse outcomes. Potential reasons for this include an increased incidence of inadvertent hypoxia and bradycardia, prolonged scene time, and inadvertent hyperventilation after successful intubation. However, all provided Class III evidence, rendering the findings questionable.

In summary, these studies suggest the need for aggressive airway management in hypoventilated or hypoxemic TBI patients, either by endotracheal intubation or by bag mask ventilation. However, in those patients with a SpO2 > 90% with supplemental oxygen, paramedic use of RSI in ground transport units in urban settings does not appear to be of benefit and may be detrimental.

Adult and Pediatrics

A. Hypoxemia (oxygen saturation [SpO2] < 90%) should be avoided and corrected immediately upon identification.

Foundation. The detrimental effect of hypoxemia on the outcome of patients with TBI has been demonstrated in several studies.8,34 The largest study, involving 717 patients admitted to 4 centers, showed that hypoxemia (an apneic or cyanotic episode in patients in the field, and SpO2 < 60 mmHg on arterial blood gas in patients in the emergency department) has a detrimental effect on patient outcome, particularly when associated with hypotension.8 Mortality was 26.9% if neither hypoxemia nor hypotension occurred, 28% for hypoxemia alone, and 57.2% if both were noted (p = 0.013).

In a second study of 50 patients with TBI who were transported by helicopter, 55% had oxygen saturation less than 90% measured at the scene prior to intubation.34 That study indicated that both hypoxemia and hypotension had a negative impact on outcome. Of the 28 patients who were hypoxemic, 13 had no associated hypotension (see Table A). There was a significant association between arterial desaturation and poor outcome (p < 0.005).

Hypoxemia can be corrected using supplemental oxygen and varying combinations of bag mask ventilation, endotracheal intubation, and other airway adjuncts including Combitubes and laryngeal mask airways. Consequently, studies have evaluated the ability of prehospital providers to perform endotracheal intubation, and whether endotracheal intubation impacts outcome.13 Only one study has looked at whether bag mask ventilation is comparable to endotracheal intubation in the prehospital environment.31

B. Hypoxemia (oxygen saturation [SpO2] < 90%) should be avoided and corrected immediately upon identification.

Foundation. In studies of general trauma patients, establishment of an artificial airway is recommended in patients unable to oxygenate or ventilate normally, unable to protect their airway, or in patients whose predicted clinical course is such that the benefit of securing the airway is thought to outweigh its risks.36 Failure of oxygenation, ventilation, and airway protection can be assessed by physical exam and by physiologic monitoring. The clinical course may be difficult to predict and so a low threshold for securing the airway has been practiced. However, this practice of securing an airway in an adequately oxygenated patient may not be beneficial when transport times are short.

A low GCS score in the pre-hospital environment has been correlated with an increased incidence of an acute intracranial lesion on head CT in the trauma center.22 One retrospective case-control study of 1,092 patients with severe TBI (GCS < 9 and a head or neck Abbreviated Injury Score [AIS] equal to or greater than 4) compared those patients who underwent prehospital endotracheal intubation with those who did not.40 EMS providers intubated patients only if they were apneic, unconscious with ineffective ventilation, and without a gag reflex. The study protocol required that no medications be used for intubation and a maximum of three intubation attempts were permitted. Prehospital endotracheal intubation was associated with significantly improved survival with an overall survival rate of 74% for intubated patients versus 64% for those not intubated. Patients with isolated TBI had a survival rate of 50% in the non-intubated group compared to a 77% survival rate in the intubated group.

C. EMS systems implementing endotracheal intubation protocols, including the use of RSI protocols, should monitor blood pressure, oxygenation, and, when feasible, EtCO₂.

Foundation. Because both hypoxia and hypotension have been associated with poor outcomes in TBI patients, careful monitoring of both blood pressure and oxygen saturation, and the correction of abnormalities when identified, are indicated. There are limitations to SpO2 monitoring. In non-TBI studies, nail polish, hypotension, severe anemia, and vasoconstriction have all been reported to give false low oxygen saturation readings.2 Despite these limitations, oxygen saturation monitors have been reported to provide a reliable measurement of hemoglobin oxygen saturation in the field, with both TBI and non-TBI patients.16,31

In one observational study, 54 patients with suspected TBI were monitored during RSI for SpO2 and effect on heart rate.16 Fifty-seven percent of RSI patients had a period of oxygen desaturation, 61% of whom had a pulse decrease of >20 beats per minute including 19% with bradycardia less than 50 beats per minute. Twenty six of the 31 events of desaturation occurred in patients whose initial SpO2 was greater than or equal to 90%, i.e., only 5 patients had uncorrectable hypoxia before intubation. One of the concerns raised by this study is why so many patients desaturated, especially in light of the report that 26/31 (85%) of the intubations were described as "easy".

Hyperventilation with hypocapnia may worsen outcome in TBI patients.10,13 Therefore, monitoring of EtCO₂ is emerging as a fundamental component of TBI management not only in the hospital but also in the pre-hospital arena. After TBI, there may be a period of prolonged hypoperfusion with cerebral blood flow (CBF) reduced by as much as two thirds of normal. Hyperventilation can further decrease the CBF, potentially causing cerebral ischemia or infarction. Evidence from hospital-based studies indicates that prophylactic early hyperventilation can seriously compromise cerebral perfusion and worsen patient outcome.27,30 Inadvertent hyperventilation during pre-hospital transport is associated with increased mortality.11

The EtCO₂ level has been shown in hospital-based studies to be well correlated with the PaCO₂ levels in healthy patients.7,17,38,39,41 However, EtCO₂ technology has limitations. A significant difference in PaCO₂ and EtCO₂ measurements has been reported in patients with multiple trauma, severe chest trauma, hypotension, and heavy blood loss.20 This difference is due to increased dead space secondary to decreased alveolar perfusion or disruptions in pulmonary blood flow.21

Several studies have demonstrated the incidence of induced hypocapnia during the field management of adult10,11 and pediatric26 TBI patients. In a retrospective study from San Diego, 59 adult severe TBI patients who were unable to be intubated without RSI were matched to 177 historical non-intubated controls.11 The study utilized EtCO₂ monitoring and found an association between hypocapnia and mortality and a statistically significant association between ventilatory rate and EtCO₂. Both the lowest and final EtCO₂ readings were associated with increased mortality vs. matched controls.

In another analysis of the same registry, EtCO₂ monitoring was used in 144 patients (compared to 149 patients without monitoring), to assess whether closer monitoring would result in a lower rate of inadvertent severe hyperventilation (defined as EtCO₂ <25 mmHg).10 Patients withEtCO₂ monitoring had a lower incidence of severe hyperventilation (5.6% vs. 13.4%; p = 0.035). There was no significant difference in mortality between these groups. A sub-analysis showed that patients who were severely hyperventilated had a higher mortality rate than those who were not (56% vs. 30%; p = 0.016).

D. When endotracheal intubation is used to establish an airway, confirmation of placement of the tube in the trachea should include lung auscultation and end-tidal CO2(EtCO₂) determination.

Foundation. The discussion of endotracheal intubation includes both whether prehospital providers can be taught the skill, and also if they can identify and correct an error when it occurs. From studies conducted in general trauma patients, the success rate of intubation by prehospital providers ranged from 50% to 100%.4,24 Major complication rates ranged from 2-17% in pediatric groups4 and as high as 25% in adults.24 Thus, confirmation of correct endotracheal tube placement is critical.

In studies cited previously, paramedics intubated successfully 84% of the time; 16% of these patients required a rescue device to secure the airway.13,14 These studies stress both the critical importance of CO2 detection protocols in any prehospital system using endotracheal intubation and the imperative for these systems to have airway rescue devices available in case of a failed intubation.

In a study from the Orlando Florida EMS system, Katz and Falk reported 28/107 (25%) patients who had a prehospital intubation arrived in the ED with an unrecognized misplaced endotracheal tube, 18 in the esophagus and 9 above the vocal cords.24 In a follow-up study, Silvestri et al. reported that the missed esophageal rate dropped to zero with the utilization of EtCO₂ monitoring in the field.32 Likewise, Grmec et al. studied 81 patients (58 with severe TBI) who underwent prehospital intubation by emergency physicians, comparing auscultation to capnometry with capnography for confirmation of proper endotracheal tube placement.19 Successful intubation was observed in 73 patients, however, 8 patients were intubated into the esophagus as shown by capnometry. Of those, four were incorrectly thought to be in the trachea based upon auscultation. In a prospective study from San Diego, with the use of auscultation, pulse oximetry, colorimetric capnometry, and syringe aspiration there were 96 endotracheal intubations with no unrecognized esophageal intubations.29

E. Patients should be maintained with normal breathing rates (EtCO₂ 35-40 mmHg), and hyperventilation (EtCO₂ < 35 mmHg) should be avoided unless the patient shows signs of cerebral herniation.2

Foundation. There is a growing body of evidence that hyperventilation with an associated hypocapnia (PaCO₂ < 35 mmHg) is associated with worse outcomes in TBI patients.10,11 Consequently there is an increased emphasis on ensuring that the ventilation promotes eucapnia during transport, i.e., EtCO₂ of 35-40. Adequacy of ventilation is dependent not only on the ventilation rate, but also on the tidal volume of oxygen delivered, and the pressure under which the tidal volume is delivered. Continuous capnometry is the best way to monitor ventilation. In the absence of capnometry, adequacy of ventilation is promoted by monitoring the airway seal and chest rise. The 2005 CRR/ECC Guidelines recommend 10-12 breaths per minute (6-7 mL/kg) delivered over 1 sec in order to minimize gastric inflation.1

In one prehospital study, 38 intubated patients with isolated TBI were placed on a ventilator with a tidal volume of 10 mL/kg at a rate of 10 breaths per minute: 17 (45%) were found to have hypocapnia (PaCO₂ < 35 mm Hg) upon arrival to the hospital (an additional 2 patient were found to be hypercapnic (PaCO₂ > 45 mmHg) upon arrival.21 The challenge of achieving eucapnia is compounded in patients with polytrauma, especially with lung injury. In a second prehospital study by the same group of investigators, that included non-TBI patients, the use of capnography with ventilator adjustments during transport significantly decreased the incidence of hypocapnia upon arrival at the trauma center.20

Pediatrics - Additional Considerations

There is no evidence to support the superiority of out of hospital endotracheal intubation over bag valve mask ventilation in pediatric patients with TBI.

Foundation. One small retrospective study reported no statistically significant difference in survival in children with TBI who were intubated in the field compared with those who were not.35 Two large pediatric studies questioned the superiority of field intubation, with or without RSI, over bag mask ventilation.9,18 Cooper et al., in a retrospective study of the National Pediatric Trauma Registry compared children with severe TBI defined as an AIS score ≥4 who underwent intubation in the field with those treated with bag-valve-mask (BVM) ventilation.9 Of the 578 patients included in the study, 99 (17%) receivedBVMventilatory assistance while 479 (83%) were intubated. Both the overall mortality rate for the two groups (48%) and the functional outcome as measured by the Functional Independence Measure (score < 6) in children > 7 years were statistically similar (ETI 67%,BVM65%). The rate of other organ system complications was lower in children who were intubated (58%) when compared to those treated withBVM (71%, p < 0.05). Of note, children who underwent intubation were older than those receiving BVM and more often received intravenous fluids, medications, and helicopter transport.

In a prospective, randomized trial that provides Class II evidence, Gausche et al. compared survival and outcome after either prehospital intubation (ETI) or ventilation with bag-valve-mask (BVM) in children using an even-odd day randomization protocol.18 A total of 830 patients were entered; 420 received ETI, 410 received BVM. A small subset of patients had TBI (36 and 27 patients in the 2 groups, respectively). There was no significant difference in outcomes between groups. Survival for TBI patients who underwent ETI was 25% compared with 32% in the BVM group (O.R. 0.71; 95%C.I. 0.23-2.19). Good neurologic outcome, defined as no or mild disability, was 11% in the ETI patients and 8% in BVM treated group (O.R. 1.44; 95% C.I. 0.24-8.52). Although no difference in outcomes was found for the small subgroup of TBI patients, the findings from the larger group of general trauma patients indicated fewer complications with BVM.

1. How do other airway management devices available for field use by EMTs with basic training compare to each other, and to endotracheal intubation? In particular, studies should focus on maintaining adequate oxygen saturation,howthis would affect outcomes in TBI patients.
2. What is the effect on outcome of early shortterm hyperventilation after TBI, beginning in the prehospital setting? Studies need to consider extremely variable prehospital times, for example, the short prehospital time in urban areas that permit only a brief period of hyperventilation.
3. Objective measures of the degree and effectiveness of hyperventilation in the prehospital setting should be developed.
4. Does the hypotensive effect of various RSI medications affect outcomes of TBI patients?
5. Is there a subset of patients with TBI who benefit from RSI? Specifically, when RSI is performed under carefully monitored conditions that ensure oxygenation and prevent hypocapnia, are outcomes improved?
6. Does the use of capnometry improve outcomes by decreasing inadvertent hypo- or hypercapnia?
7. A large, well-designed trial is needed to compare no intubation, non-pharmacologically-assisted intubation, and RSI for maintaining adequate prehospital oxygenation.