What is the relationship between the Glasgow coma scale and airway protective reflexes in the Chinese population?

Resuscitation 83 (2012) 86–89 Contents lists available at ScienceDirect Resuscitation journal homepage: www.elsevier.com/locate/resuscitation Clinical paper What is the relationship between the Glasgow coma scale and airway protective reflexes in the Chinese population?夽,夽夽 K.R. Rotheray, P.S.Y. Cheung, C.S.K. Cheung, A.K.C. Wai, D.Y.S. Chan, T.H. Rainer, C.A. Graham ∗ Accident and Emergency Medicine Academic Unit, Chinese University of Hong Kong, Hong Kong a r t i c l e i n f o Article history: Received 19 January 2011 Received in revised form 20 June 2011 Accepted 16 July 2011 Keywords: Glasgow coma scale Reflex Pharyngeal Chinese Unconsciousness a b s t r a c t Aim: To describe the relationship of gag and cough reflexes to Glasgow coma score (GCS) in Chinese adults requiring critical care. Method: Prospective observational study of adult patients requiring treatment in the trauma or resuscitation rooms of the Emergency Department, Prince of Wales Hospital, Hong Kong. A long cotton bud to stimulate the posterior pharyngeal wall (gag reflex) and a soft tracheal suction catheter were introduced through the mouth to stimulate the laryngopharynx and elicit the cough reflex. Reflexes were classified as normal, attenuated or absent. Results: A total of 208 patients were recruited. Reduced gag and cough reflexes were found to be significantly related to reduced GCS (p = 0.014 and 0.002, respectively). Of 33 patients with a GCS ≤ 8, 12 (36.4%) had normal gag reflexes and 8 (24.2%) had normal cough reflexes. 23/62 (37.1%) patients with a GCS of 9–14 had absent gag reflexes, and 27 (43.5%) had absent cough reflexes. In patients with a normal GCS, 22.1% (25/113) had absent gag reflexes and 25.7% (29) had absent cough reflexes. Conclusions: Our study has shown that in a Chinese population with a wide range of critical illness (but little trauma or intoxication), reduced GCS is significantly related to gag and cough reflexes. However, a considerable proportion of patients with a GCS ≤ 8 have intact airway reflexes and may be capable of maintaining their own airway, whilst many patients with a GCS > 8 have impaired airway reflexes and may be at risk of aspiration. This has important implications for airway management decisions. © 2011 Elsevier Ireland Ltd. All rights reserved. 1. Introduction The Glasgow coma scale (GCS) was originally described in trauma patients and is a tool which allows standardized recording of a patient’s level of consciousness.1 This has led to recommendations being made that in the setting of trauma, patients with a GCS of ≤8 should undergo tracheal intubation in order to prevent possible airway obstruction, aspiration or respiratory compromise leading to secondary brain injury.2,3 In the emergency setting clear guidelines are helpful for decision making, and a GCS of ≤8 has come to be commonly used as an indication for intubation in patients with reduced conscious level for any reason. The underlying assumption is that any patient who has a GCS of ≤8 is unable to protect their 夽 A Spanish translated version of the summary of this article appears as Appendix in the final online version at doi:10.1016/j.resuscitation.2011.07.017. 夽夽 Work was performed at: Accident and Emergency Department, Prince of Wales Hospital, Shatin, New Territories, Hong Kong SAR, China. ∗ Corresponding author at: Accident and Emergency Medicine Academic Unit, Chinese University of Hong Kong, Trauma and Emergency Centre, Prince of Wales Hospital, Shatin, New Territories, Hong Kong SAR, China. Tel.: +852 2632 1033; fax: +852 2648 1469. E-mail address: cagraham@cuhk.edu.hk (C.A. Graham). 0300-9572/$ – see front matter © 2011 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.resuscitation.2011.07.017 own airway and so is at risk of aspiration, whereas any patient with a GCS of >8 has intact airway reflexes and so is able to protect their own airway. Whilst there is little doubt that inability to protect the airway is an indication for intubation in the setting of critical illness or injury, there is currently a dearth of evidence verifying the relationship of the GCS, and in particular a cut-off of GCS ≤ 8, to a patient’s ability to protect their own airway. In a UK study conducted in 1992, Moulton and Pennycook examined the relationship of the GCS to airway reflexes in a population that mainly comprised patients with poisoning and head injury.4 They found that whilst GCS was strongly related to gag reflex, a number of patients with a GCS > 8 had a reduced or absent gag reflex, whilst a number with a GCS ≤ 8 had an intact gag reflex. They also examined the relationship between GCS and cough reflex and found that even at the lowest coma scores some patients had intact cough reflexes.5 Based on these findings they argued that some patients with high levels of consciousness may not be capable of protecting their own airways and be at risk of aspiration, whilst conversely, some patients might retain their airway reflexes even at low levels of consciousness and so require drugs for safe intubation. Two recent studies of clinical outcomes in poisoned patients with reduced conscious levels have suggested that many patients K.R. Rotheray et al. / Resuscitation 83 (2012) 86–89 Table 2 Relationship of cough reflex to GCS. Table 1 Relationship of gag reflex to GCS. GCS 15 Gag reflex Normal Attenuated Absent Total 73 (64.6%) 15 (13.3%) 25 (22.1%) 113 (100%) 87 GCS 9–14 33 (53.2%) 6 (9.7%) 23 (37.1%) 62 (100%) GCS ≤ 8 12 (36.4%) 7 (21.2%) 14 (42.4%) 33 (100%) Pearson 2 for relationship of reduced GCS to impaired gag reflex p = 0.01. Cough reflex Normal Attenuated Absent Total GCS 15 GCS 9–14 GCS ≤ 8 69 (61.1%) 15 (13.3%) 29 (25.7%) 113 (100%) 27 (43.5%) 8 (12.9%) 27 (43.5%) 62 (100%) 8 (24.2%) 9 (27.3%) 16 (48.5%) 33 (100%) Pearson 2 for relationship of reduced GCS to impaired cough reflex p = 0.002. 3. Statistics with a GCS ≤ 8 can be safely managed without intubation.6,7 In contrast to this, two studies of aspiration pneumonitis in poisoned patients found that increased risk of aspiration was associated not only with GCS ≤ 8 but also with GCS < 15.8,9 These studies add to the weight of evidence that the current common practise of using GCS ≤ 8 as a marker of a patient’s ability to protect their own airway may be inappropriate and detrimental to some patients. Most of the research into the relationship of airway reflexes with GCS has concentrated on patients with alcohol intoxication, poisoning and head injury.4,5,10 In addition, most previous studies have been in predominantly young, Caucasian populations. We aimed to examine the relationship of airway reflexes to GCS in an older, Chinese population where alcohol intoxication is rare and other causes of reduced conscious level, such as stroke, are more common. 2. Methods We conducted a prospective observational study recruiting a convenience sample of adult Chinese patients admitted to the trauma and resuscitation rooms of the Prince of Wales Hospital, Shatin, Hong Kong for any reason. Stimulation of the posterior pharyngeal wall in eligible patients was performed atraumatically using a long cotton bud to stimulate the posterior pharyngeal wall (gag reflex). Responses were classified as: (1) normal presence of gag reflex; (2) attenuated (diminished) presence of gag reflex; and (3) total absence of gag reflex. Secondly, a soft tracheal suction catheter was introduced through the mouth to stimulate the laryngopharynx and elicit the cough reflex. Again, responses were classified as: (1) normal presence of cough reflex (i.e. vigorous cough on stimulation); (2) attenuated (diminished) presence of cough reflex; and (3) total absence of cough reflex. All tests were performed in an atraumatic manner, once only, to elicit the reflexes. Suction apparatus were immediately available for all patients should they vomit. Patients found to be in cardiac arrest on arrival in the department were excluded from the study. We chose to divide GCS into 3 groups: coma (using the traditional definition of GCS ≤ 8), impaired consciousness without coma (GCS 9–14) and normal conscious level (GCS 15). A standardized record form was completed by the attending medical officer or specialist after they performed the tests. No specific training was given to the examining doctors in addition to their normal practice. Emergency department doctors were informed of the study at regular intervals and reminded about details of the study protocol. Admission diagnoses and the need for emergency department intubation were also recorded. Ethical approval was obtained from the CUHK-NTEC Clinical Research Ethics Committee. Patients with GCS 15 gave verbal consent. Since the testing of airway reflexes may be considered a part of the normal assessment of patients with a reduced conscious level, a consent waiver was granted for patients not capable of giving valid informed consent, with patients who subsequently recovered being asked for retrospective verbal consent. Data was entered into Excel® (Microsoft Corp, WA, USA) and analysed using SPSS v17.0 (SPSS Inc., IL, USA). Pearson’s Chi-squared test was used to analyse the relationship of impaired/absent gag and cough reflexes with a reduced GCS. Logistic regression analysis was performed to produce odds ratios with 95% confidence intervals (CI) to identify predictors of the presence of normal gag and cough reflexes. Gag and cough reflexes were taken as independent variables and age (in single year groups), gender and GCS (by single points) were used as dependent variables. 4. Results A total of 208 patients were recruited to the study between November 2006 and January 2009. The average age was 64.8 (IQR 51–81) years and 57.2% (119) were male. All patients with capacity to consent did so and no patients were lost as a result of withholding consent. Patients presented with a wide range of illnesses including 54 patients (26%) with neurological problems (includes ischaemic stroke, seizure, intra-cerebral haemorrhage), 81 patients (38.9%) with cardiorespiratory problems (acute coronary syndrome, congestive cardiac failure, asthma, chronic obstructive pulmonary disease), 15 patients (7.2%) with poisoning, 9 patients (4.3%) with trauma and 27 patients (13%) whose illness did not fall into any of these groups. 113 (54.3%) of patients had a GCS of 15, 62 patients (29.8%) had a GCS of 9–14 and 33 patients (15.9%) had a GCS ≤ 8. No patient vomited during assessment of airway reflexes; aspiration was not assessed. During the study period, the ED was staffed by a mean of 10 specialists and 18 medical officers (trainees) who did the testing of the patients’ reflexes. GCS ≤ 8 was significantly related to the absence of both cough and gag reflex (Tables 1 and 2); however, regardless of age, gender or underlying illness the airway reflexes were found to be absent in some patients with GCS 15, and present in some patients with GCS ≤ 8. Around one third of patients with GCS ≤ 8 had an intact gag reflex, whilst a fifth of patients with GCS 15 had no gag reflex. The cough reflex followed a similar pattern with around a quarter of patients with GCS ≤ 8 having an intact cough reflex, and a quarter of patients with GCS 15 having no cough reflex. On logistic regression analysis, female gender, younger age and higher GCS were found to be significantly related to the presence of a gag reflex (Table 3). The Table 3 Logistic regression analysis for relationship of airway reflexes to GCS, age and sex. Normal gag reflex Younger agea Female gender Increased GCSb Normal cough reflex Younger agea Female gender Increased GCSb a b OR 95% CI p value 0.98 2.11 1.15 0.97–1.00 1.15–3.86 1.07–1.25 0.03 0.02 <0.001 0.99 1.47 1.21 0.98–1.01 0.82–2.66 1.11–1.32 0.26 0.20 <0.001 Age grouped by single year. GCS grouped by single point. 88 K.R. Rotheray et al. / Resuscitation 83 (2012) 86–89 presence of a cough reflex was significantly related to increased GCS but not to age or gender. Logistic regression analysis showed that the presence of normal gag and cough reflexes were associated with higher GCS verbal subscores (OR 1.30; 95% CI for OR 1.10–1.54; p = 0.002 for gag reflex; OR 1.46; 95% CI for OR 1.23–1.75; p < 0.001 for cough reflex). Neither the motor nor the eye subscores of the GCS were predictive of the presence of a normal gag or cough reflex. 5. Discussion In this the first study of its kind in an Asian population, we found a strong relationship of airway reflexes with GCS, but there were many patients with either normal reflexes at GCS ≤ 8 or absent/attenuated reflexes at GCS > 8. This was the case across a wide variety of conditions causing reduced conscious level. These findings are consistent with those found in Moulton and Pennycook’s UK study, although the proportion of patients with GCS ≤ 8 who had normal gag reflex was much higher in our study: 12/35 (34%) compared with 4/37 (11%) in their study.4 It is possible that this may be due to the different disease spectrum seen within our patient group, in particular the much smaller numbers of patients with drug or alcohol intoxication. Another possible explanation would be ethnic variation. The only other study looking at gag reflex and GCS in a non-western (Iranian) population10 found the gag reflex to be present in 90/155 (58.1%) of poisoned patients with GCS ≤ 12 which is considerably higher than the 23.7% (14/59) of patients with a GCS ≤ 12 who had a normal gag reflex in Moulton and Pennycook’s study.4 The higher proportion of men with impaired or absent gag reflex is also interesting in the light of findings in poisoned patients that rates of aspiration pneumonitis were significantly higher amongst men.8 It may be that men are more likely to have a decreased gag reflex, putting them at greater risk of airway compromise; further studies would be required to confirm this hypothesis. Our study confirms shows that absence of airway reflexes in patients with low GCS should not be assumed and use of drugs to prevent stimulation of these reflexes during intubation is appropriate. The use of drugs for intubation in unconscious patients with head injury is recommended in order to minimise the rise in intracranial pressure which occurs at intubation.12 In a study comparing emergency rapid sequence induction with and without paralysis, Li et al. showed that the use of neuromuscular blocking agents reduced aspiration, airway trauma and death.11 Another question raised by the finding that many patients with GCS ≤ 8 have intact airway reflexes is whether intubation is necessary for all patients in this group. Intubation itself carries risk and some studies show that patients with low GCS can be safely managed without intubation6,7 ; it may therefore be inappropriate to perform intubation solely on the basis of ‘GCS ≤ 8’. Conversely, since more than 50% of patients with GCS 9–14 had absent or attenuated airway reflexes those with a higher GCS may not necessarily be able to protect their own airway, and failing to intubate them may expose them to unnecessary risk. This is consistent with studies showing that patients with GCS < 15 rather than just those with GCS ≤ 8 are at increased risk of aspiration.8,9 Adnet found that poisoned patients with GCS 9–14 had rates of aspiration of 14.7%, and Isbister found that once other confounders had been accounted for only GCS < 15, not GCS ≤ 8, was significant for risk of aspiration.8,9 These studies however were based on patients with reduced conscious level due to poisoning, and the level of risk amongst patients with reduced conscious level due to other causes is not clear.13 Airway protection is one of the foundations of managing critically ill patients, however there is currently little evidence to guide the practitioner in deciding which patients require tracheal intu- bation. This study adds to the growing body of evidence that GCS alone is not a good basis for making the decision to intubate; however, determining which factors might be best to guide decision making was beyond the scope of our study. Studies in poisoned populations have found that factors such as age,8,10 male gender8 seizures8 and type of poisoning8,10 appeared significant but further studies would be needed to determine what other factors are important and whether this applies to other populations. Further prospective studies are needed in this field. This study is not advocating the use of airway reflexes as a means to decide which patients require tracheal intubation and the routine testing of airway reflexes is to be discouraged. Our finding that an increased verbal subscore of the GCS was strongly associated with the presence of a normal gag and cough reflex suggests that patients who score lower than 5 on the verbal score of the GCS should have their airway reflexes carefully assessed. However, it must be remembered that of the patients with a verbal score of 5, 33.6% (44/131) had a non-normal gag reflex and 36.6% (48/131) had a non-normal cough reflex, which emphasises the fact that the GCS cannot be used in isolation to predict the presence or absence of airway reflexes. Limitations: This is a relatively small study and the patients within in it are heterogeneous, making it difficult to discern the reasons for differences between our findings and those elsewhere, which may raise uncertainties as to whether these findings are applicable in other populations. It remains possible that less sick patients may have been more likely to be enrolled into the study given the nature of resuscitation room practice; we cannot exclude this possibility although we think this is unlikely. The overall patterns are similar to previous studies, which were carried out populations with higher levels of alcohol intoxication and trauma, and the study group is reflective of the group of patients for whom the critical care physician needs to make a decision on the appropriateness of intubation. Measurement of gag and cough reflexes is somewhat subjective and no assessment of inter-rater reliability was made. The measurement of airway reflexes is only a proxy for whether or not a patient is able to manage their own secretions, which is the clinically important question. However impaired airway reflexes have been shown to be one factor which increases the risk of developing aspiration pneumonitis.10 6. Conclusion Our study has shown that in a Chinese population with a wide range of critical illness (but little trauma or intoxication), reduced GCS is significantly related to gag and cough reflexes. However, a considerable proportion of patients with a GCS ≤ 8 have intact airway reflexes and may be capable of maintaining their own airway, whilst many patients with a GCS > 8 have impaired airway reflexes and may be at risk of aspiration. It is important to question the evidence base for current practice and clarify further which patients need airway protection; this study further brings into question the use of a cut off of GCS ≤ 8 as the means to make this judgement. Conflicts of interest There were no conflicts of interest in undertaking this study. References 1. Teasdale G, Jennett B. Assessment of coma and impaired consciousness. Lancet 1974;ii:81–4. 2. Gentleman D, Dearden M, Midgely S, Maclean D. Guidelines for resuscitation and transfer of patients with serious head injury. 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