How to cite this article: León-Gutiérrez MA, Tanus-Hajj J, Sánchez-Hurtado LA. [Predictors of extubation failure in neurosurgical patients]. Rev Med Inst Mex Seguro Soc. 2016;54 Suppl 2:S196-201.
Received: November 2nd 2015
Judged: May 2nd 2015
Marco Antonio León-Gutiérrez,a Janet Tanus-Hajj,b Luis Alejandro Sánchez-Hurtadoc
aUnidad de Cuidados Intensivos
bDivisión de Servicios Centrales
cUnidad de Cuidados Intensivos, Hospital de Especialidades, Centro Médico Nacional La Raza
a,bHospital de Especialidades, Centro Médico Nacional Siglo XXI
Instituto Mexicano del Seguro Social, Ciudad de México, México
Communication with: Marco Antonio León Gutiérrez
Telephone: (55) 5627 6900, extensions 21054 and 21445
Background: The information regarding the factors that affect the success of extubation in neurosurgical patients is limited; thus, it is necessary to determine the prevalence, and the associated factors, of extubation failure in neurosurgical patients.
Methods: It was performed a prospective, longitudinal, observational and comparative study in neurosurgical patients with criteria for extubation. In those who the number of endotracheal aspirations had failed 24 hours before extubation, it was analyzed the presence of cough reflex, length of stay and mechanical ventilation days.
Results: 70 patients were included in the study, of whom 11.4 % patients failed extubation and the associated factors were performing 6 events or more of endotracheal tube suction 24 hours prior to weaning (relative risk [RR] = 1.88, 95 % confidence interval [CI] = 1.14-3.09, p 0.01), 7 days of mechanical ventilation (RR = 1.31, 95 % CI = 1.08-1.57, p 0.005) and a length of hospital stay of 7.5 days (RR = 1.24, 95 % CI = 1.05-1.47, p 0.01).
Conclusions: performing 6 or more endotracheal tube suction events during the 24 hours before extubation is a risk factor for extubation failure in neurosurgical patients.
Keywords: Airway extubation; Mechanical ventilation; Neurosurgical procedures
When the condition that caused the need for mechanical ventilatory support in neurosurgical patients has been controlled or eradicated, it is essential to plan the withdrawal of mechanical ventilation, because doing so prematurely or late may increase morbidity and mortality.1-4
In order to maintain adequate oxygenation and ventilation, and because of their condition,5 patients need protection of the airway with endotracheal intubation and mechanical ventilatory support.
Most studies on the withdrawal of mechanical ventilation and extubation have focused mainly on general medical or surgical patients. The information available on factors affecting the success of extubation in patients with neurosurgical pathologies is very limited.6-8
Neurosurgical patients with compromised consciousness are more predisposed to complications related to mechanical ventilation, such as prolonged mechanical ventilation, pneumonia associated with mechanical ventilation, and a higher percentage of reintubation and tracheotomy.6-8 The interaction of lung mechanics and the ability to keep the airway clean for successful withdrawal of mechanical ventilation and extubation has been partially evaluated.7,9
The guidelines recommend testing spontaneous ventilation to identify patients who might have successful extubation. This involves testing spontaneous ventilation when the patient has control of the causes that led to mechanical ventilatory support, adequate oxygenation with FiO2 < 0.4, positive end-expiratory pressure (PEEP) < 8, hemodynamic stability, and adequate respiratory effort.1,2
Whether or not this type of patients meets the protocol for removal of mechanical ventilation and extubation, they have a high rate of failure, ranging from 17.6 to 38.8%.6-11
Information is limited on the predictors of success or failure in the removal of mechanical ventilation in neurocritical patients, so, given the need to find strategies to improve success in the withdrawal of mechanical ventilation in this group of patients, this study aimed to establish the frequency of failure of extubation in neurosurgical patients and to determine the association between the number of aspirations of secretions from the orotracheal cannula in the 24 hours before extubation, the presence of cough reflex, days of stay, and days of mechanical ventilation in patients with extubation failure in an intensive care unit.
A prospective, longitudinal, observational and comparative study was made in neurosurgical patients admitted in the immediate postoperative period, who required continued endotracheal intubation and ventilatory mechanical support, and who had failure of extubation (defined as reintubation within 48 hours of starting the attempted withdrawal)1,2 in the Intensive Care Unit (ICU) of the Hospital de Especialidades “Bernardo Sepúlveda” of Centro Médico Nacional Siglo XXI of IMSS, during the period from July to December 2014.
The patients’ demographics; the days of stay in the ICU; the days of mechanical ventilation; and APACHE II (Acute Physiology And Cronic Health Evaluation) values were all recorded; researchers also recorded:
Kirby index value prior to extubation, i.e., arterial oxygen pressure (PaO2) over the fraction of inspired oxygen (FiO2).
The oxygenation index, which is the product of arterial oxygen pressure (PaO2) times the fraction of inspired oxygen (FiO2) over mean airway pressure (Paw).
The ventilation index, which is the volume exhaled per minute (VE) over the pressure of carbon dioxide (PaCO2).
Static compliance, i.e. the exhaled tidal volume (Vte) over the difference of plateau pressure of the airway or plateau pressure (Ppl) with PEEP.
The number of times secretions were aspirated through the orotracheal cannula in the 24 hours before extubation, and the presence of cough reflex after exogenous stimulus, which was listed as present or absent, were also quantified. Patients were then followed for 48 hours after extubation to quantify the proportion of success or failure in the removal of mechanical ventilation.
As for statistical analysis, quantitative variables were expressed as medians with interquartile range, qualitative variables were expressed as percentages. The Mann-Whitney U and Chi-squared or Fisher's exact test were used as nonparametric tests.
The association of variables with extubation failure was determined by logistic regression and multivariate analysis; the relative risk and 95% confidence interval were estimated, and p-values ≤ 0.05 were established as statistically significant. The analysis was done using SPSS version 16.
In a period of six months, a total of 96 patients were included. Of those patients, only 70 met the inclusion criteria.
22 patients were excluded: three because mechanical ventilation withdrawal testing was not done during their stay in the ICU, 16 because they underwent tracheostomy, three because they were extubated by clinical judgment, and four for incidental extubation. The median age was 48.5 years, ranging from 20 to 89 years. 64.3% were women and 35.7% men.
Successful extubation was achieved in 88.6% of cases, with a failure rate of 11.4%. The general characteristics of the study population are presented in Table I.
|Table I Demographic characteristics of patients in the study (n = 70)|
|PO of anterior fossa tumor||21||33.87||3||37.5|
|PO due to cerebral aneurysm clipping||19||30.63||2||25|
|Drainage of hematoma||5||8.06||3||37.5|
|PO of arteriovenous malformation||5||8.06||0||0|
|PO of posterior fossa tumor||4||6.45||0||0|
|PO due to ventricular shunt||1||12.5||0||0|
|Mean ± IR||Mean ± IR||p|
|Age (in years)||48||35.75-60||58.5||41.5-65.75||0.13|
|Days in the ICU||3||2-4.25||7.5||3.75-11.75||0.003†|
|Days on mechanical ventilation||2||1-3||7||3.25-10.5||0.001†|
|*Chi-squared was used
†Mann-Whitney U was used
PO: postoperative; IR = interquartile range; APACHE = Acute Physiology And Chronic Health Evaluation; ICU = intensive care unit
The variables studied as risk factors were the number of times endotracheal secretions were aspirated in the 24 hours before extubation, and the presence of cough reflex upon withdrawal of mechanical ventilation. The analysis of all the variables studied is shown in Table II.
|Table II Analysis of study variables as predictive in extubation|
|Cough reflex present||62||100||7||87.5||0.11 *|
|Mean ± IR||Mean ± IR||p|
|Number of aspirations of secretions||3||2-5||6||4.25-6||0.13†|
|Rapid shallow breathing index||40.5||36-67.25||46||29.25-83.75||0.40†|
|* Chi-squared was used
† Mann-Whitney U was used
Variables that showed difference in the bivariate analysis were included in the multivariate analysis model to identify those that were associated with failed removal of mechanical ventilation, so their results are shown in Table III.
|Table III Variables associated with failure of extubation|
|Number of aspirations of secretions||1.88||1.14-3.09||0.01|
|Days of mechanical ventilation||1.31||1.08-1.57||0.005|
|Days in the ICU||1 24||1.05-1.47||0.01|
|APACHE II||1.15||0 97-1.35||0.11|
|Cough reflex present||0||1|
|RR = risk ratio; CI: confidence interval; ICU = intensive care unit; APACHE = Acute Physiology And Chronic Health Evaluation|
The withdrawal of mechanical ventilatory support is of paramount importance for patients who need such support for their pathological conditions at some point in their development. 88.6% of extubations were successful among the population studied, a figure much higher than previously reported in the literature for neurocritical patients.6,7,10,12 The failure rate obtained was 11.4%, which, unlike those reported by other authors (Namen  with 38.8%, Qureshi  with 34.4%, Vallverdu  35.7%, and Coplin  17.6%), is well below those records.7,10 However, there are some differences between these studies and the population we studied. Our study did not include patients with neurological impairment secondary to trauma; also, the Glasgow Coma Scale score with which T system testing was done and after ventilation withdrawal was higher than in other studies: 11 versus 8. This difference in neurological status could have an impact on the rate of withdrawal success in this group of patients; however, it is important to remember that, according to recommendations, patients must have a Glasgow score over 8 points for extubation.1,2,7
A sensitivity of 35% and a specificity of 79% have been described previously when extubation and withdrawal of mechanical ventilation are done with clinical judgment.1 The protocol for withdrawal of mechanical ventilation with proof of spontaneous ventilation has a sensitivity and specificity of 95% when performed correctly and when all the criteria are met.13
Regarding the factors that could determine success or failure in the withdrawal of mechanical ventilation, it was found that six or more aspirations of bronchial secretions in the 24 hours prior to removal of ventilation was associated with an increased risk of failure. This may be related to the patient's ability to keep their airway clean or free. This may be a factor to be added to the requirements that must be met when planning to withdraw the endotracheal tube and mechanical ventilatory support. It had previously been suggested that the frequency of bronchial aspirations could be a factor that determines success or failure,10 but our work established an absolute number, which is more practical in daily evaluation of patients, unlike other authors who suggest measurement scales.10,14
It is important to note that the characteristics of secretions could be important to guide the suspicion of complications associated with mechanical ventilation that will affect failure in extubation and the withdrawal of mechanical ventilatory support, such as pneumonic processes; however, so far it has not been possible to determine their real value in the process of mechanical ventilation withdrawal.11,13,15,16
As for the presence of coughing effort, it was not possible to establish or identify a difference between those who had success or failure in extubation, and the latter group had the only subject that without a cough reflex, unlike the rest of the population that did have this reflex. Coughing is an airway cleaning and defense mechanism; the absence of this reflex could compromise these functions,15-17 mainly in patients who have lesions in the central nervous system structures regulating this, or in the peripheral nerves. In our population, in most of the patients who lacked this received early tracheostomy or did not have mechanical ventilatory support removed without receiving T system testing, so therefore they were not considered in the final analysis.7,11
The duration of mechanical ventilation and length of stay also showed a strong association with the probability of failure according to the results obtained, which means that the longer the mechanical ventilation, the greater the risk of failure due to the possibility of associated complications, such as infectious diseases or neuromuscular disorders, among others.8
As for the parameters evaluating oxygenation and ventilation, as with the other authors,17-19 there was no difference between groups with success and failure, which means that this is not decisive to predict the failure or success of extubation and mechanical ventilation withdrawal for these patients, as indeed these must be controlled to consider withdrawal. However, a difference was observed in the static compliance between groups, which may be related to the patient's ability to maintain spontaneous ventilation at the time of withdrawal of mechanical ventilation.
Finally, previous studies that have attempted to assess the withdrawal of mechanical ventilation in neurocritical patients8,11,15 do not mention whether or not there was a difference in the severity of patients undergoing extubation testing.
As limitations of this study, we can point to its limited external validity, since it was conducted in a single tertiary care hospital, specialized in the management of neurocritical patients; it also has a small number of patients. Another important limitation is that we do not have information on pulmonary and neurological conditions prior to ICU admission, which could influence patients’ outcomes.
Knowledge and use of the protocol for mechanical ventilation withdrawal with spontaneous ventilation testing may be appropriate to reduce the rate of failure when withdrawing mechanical ventilation in neurosurgical patients.Considering the number of days of mechanical ventilation and the number of aspirations of secretions from the tracheal cannula in neurocritical patients during the process of withdrawal of mechanical ventilation could help identify patients at increased risk of failure in the mechanical ventilation withdrawal process, even if they have completed the full withdrawal protocol, so both the number of six or more aspirations of endotracheal secretions in the 24 hours before extubation, and the number ≥ 7 days of mechanical ventilation should be included in the routine evaluation of these patients in order to take these as risk factors for extubation failure.
Conflict of interest statement: The authors have completed and submitted the form translated into Spanish for the declaration of potential conflicts of interest of the International Committee of Medical Journal Editors, and none were reported in relation to this article.