Incidence, indication and complications of postoperative reintubation after elective intracranial surgery

ABSTRACT CONTEXT AND OBJECTIVE: There are no reports on reintubation incidence and its causes and consequences during the postoperative period following elective intracranial surgery. The objective here was to evaluate the incidence of reintubation and its causes and complications in this situation. DESIGN AND SETTING: Prospective cohort study, using data obtained at a tertiary university hospital between 2003 and 2006. METHODS: 169 patients who underwent elective intracranial surgery were studied. Preoperative assessment was performed and the patients were followed up until hospital discharge or death. The rate of reintubation with its causes and complications was ascertained. RESULTS: The incidence of reintubation was 12.4%, and the principal cause was lowered level of consciousness (71.5%). There was greater incidence of reintubation among females (P = 0.028), and greater occurrence of altered level of consciousness at the time of extubation (P < 0.0001). Reintubated patients presented longer duration of mechanical ventilation (P < 0.0001), longer stays in the intensive care unit (ICU) and in the hospital (P < 0.0001), greater incidence of pulmonary complications (P < 0.0001), greater need for reoperation and tracheostomy, and higher mortality (P < 0.0001). CONCLUSION: The incidence of reintubation in these patients was 12.4%. The main cause was lowering of the level of consciousness. Female gender and altered level of consciousness at the time of extubation correlated with higher incidence of reintubation. Reintubation was associated with pulmonary complications, longer durations of mechanical ventilation, hospitalization and stay in the ICU, greater incidence of tracheostomy and mortality.


INTRODUCTION
[12] Neurosurgical procedures such as intracranial operations have been reported to be a significant risk factor for the development of pulmonary complications. 4 However, these complications have not been correlated with patient reintubation, nor are there any reports on patient reintubation during the postoperative period following elective intracranial neurosurgery.
Therefore, this lack of information justified the present prospective study to determine the incidence, causes and complications among patients under postoperative care following elective intracranial neurosurgery.

OBJECTIVE
The objective was to evaluate the incidence of reintubation and its causes and complications during the postoperative period following elective intracranial surgery.

Preoperative evaluation
During the preoperative period, all the patients answered a questionnaire that included questions asking for information on dyspnea, coughing, bronchospasm and smoking.The physical examination included observation of the type of cough and sputum; pulmonary auscultation; chest assessment; measurement of the level of consciousness using the Glasgow Coma Scale (GCS); identification of any presence of prior pneumopathy; presence of any preexisting diseases such as arterial hypertension, cardiopathy and diabetes mellitus; existence of any prior intracranial surgery; identification of the diagnosis and site affected; and risk classification by means of the appraisal of selfcare agency (ASA) scale.
After the surgical procedure, the patients were sent to the ICU and those who were still intubated remained on mechanical ventilation.Postoperatively, the patients were followed up every day by the same team as in the preoperative period, until they were discharged or died.

Assessment of the possibility of discontinuation of mechanical ventilation
The patients underwent daily clinical and respiratory assessments to determine the possibility of discontinuation of mechanical ventilation, and those who presented satisfactory evaluations underwent the spontaneous breathing trial (SBT).

Spontaneous breathing trial
The SBT lasted for between 30 and 120 min and was performed with a T tube or pressure support of less than 8 cmH

Criteria for extubation failure
Failure in extubation was considered to exist when the patients needed to be reintubated within 48 hours.The decision to reintubate the patient was based on clinical deterioration, as shown by at least one of the following criteria: decreased level of consciousness (GCS < 8); significant worsening of pH or arterial PaCO 2 ; SaO 2 lower than 90%, with inspired oxygen fraction over 0.5; and signs of increased respiratory work (tachypnea, use of accessory breathing muscles and paradoxical pattern).

Level of consciousness at the time of extubation
The patients were divided into two groups based on their consciousness level at the time of extubation: GCS of 10-11 T and 8-9 T, in which the letter T shows that the patient had an orotracheal tube at the time of the evaluation.The normal group was considered to be those with GCS of 10-11 T, since they were capable of responding to simple commands, and the altered group was considered to be those with GCS of 8-9 T, since they did not show any logical response to simple commands.

Causes of reintubation
The causes of reintubation were classified as respiratory insufficiency, upper airway obstruction, hemodynamic instability or lowered level of consciousness.

Respiratory complications of reintubation
Complications of reintubation such as tracheobronchitis and pneumonia were monitored.Pneumonia was defined as the presence of pulmonary infiltrate on the chest X-ray, associated with at least two of the following signs: purulent tracheobronchial sputum, increased body temperature (over 38.3 °C), and leukocytosis (more than 25% above the baseline count). 12

RESULTS
Four hundred and thirty-four patients who had undergone intracranial surgery were hospitalized in the neurosurgical ICU during the study period, and 169 patients were included in the study.
Among the 265 individuals who were excluded, 15 had their operations cancelled, 148 were extubated in the surgical center, 21 died before weaning off mechanical ventilation, 4 did not conclude the preoperative evaluation, 5 were ventilated before surgery, 33 did not have the operation proposed, 11 were tracheostomized and 28 were delivered to another ICU during the postoperative period (Figure 1).
The demographic characteristics of the patients included in the study are presented in Table 1.All of the 169 patients were weaned off mechanical ventilation and extubated, but 21 of these (12.4%) required reintubation within 48 hours.The causes of extubation failure were lowered level of consciousness in 71.5% of the cases, respiratory insufficiency in 19% and upper airway obstruction in 9.5%.
Univariate analysis found three variables before extubation that differed between the patients who required reintubation and those who were successfully extubated: female gender, GCS at the time of extubation and duration of mechanical ventilation (Table 2).After extubation, seven other variables were identified as differing between the patients who needed reintubation and those successfully extubated: duration of mechanical ventilation, length of stay in the ICU, length of hospital stay, pulmonary complications, reoperation, tracheostomy and mortality (Table 3).
However, most of these patients had undergone emergency surgery, and a minority had undergone elective intracranial operations. 19In the present study, during the postoperative period following elective intracranial surgery, the incidence of reintubation was 12.4%.This rate is high in comparison with general elective operations, but lower than the prevalence of reintubation among neurosurgical patients, including non-elective operations.
Compared with elective surgery, this incidence seems too high, and therefore, perhaps, other criteria besides those already described in weaning guidelines should be developed and analyzed at the time of extubation of patients who have undergone elective neurosurgery.Noninvasive monitoring of the cerebral flow may be one of these.[22][23] Nevertheless, we found that a lowered level of consciousness was the main cause of postoperative reintubation following elective intracranial surgery (71.5%).This may relate to the surgical procedure or to another factor relating to the respiratory center consequent to surgical manipulation, which would be likely to lead to hypoventilation and consequent CO 2 elevation, along with a drop in the level of consciousness.
In a population of neurosurgical patients, Namen et al. 19 studied the association between the level of consciousness and reintubation.They observed that a GCS score greater than or equal to eight was associated with successful extubation in 75% of the cases, whereas the proportion was only 33% among their patients with a GCS score lower than eight.Our study confirmed that patients with a low level of consciousness who had a GCS score less than or equal to nine at the time of extubation presented higher incidence of reintubation.In our study, we also noted that patients who had a longer duration of mechanical  ventilation during the postoperative period presented higher incidence of reintubation.
This may relate to the surgical complexity or, on the other hand, to the alteration in consciousness level, which would explain the longer duration of mechanical ventilation.
Mechanical ventilation for more than 48 hours may contribute towards pulmonary complications in patients who have undergone intracranial surgery, 24 and to worsening of gas exchanges. 25ese complications may also contribute towards reintubation.
Reintubation is associated with increased hospital mortality, longer hospital stay, higher incidence of pneumonia, high hospital costs and a greater incidence of tracheostomy. 5,11,21,23In the same way, we observed that in the postoperative phase following elective intracranial surgery, our patients who were reintubated spent longer times on of mechanical ventilation (P < 0.0001), remained in the ICU for longer times (P < 0.0001), had longer hospital stays (P < 0.0001) and presented higher incidence of respiratory complications (P < 0.0001).
Mortality is another consequence of reintubation.Demling et al. 6 observed a 40% mortality rate among surgical patients who were reintubated.Many studies have shown that the mortality rate associated with reintubation is 2.5 to 10 times higher than among patients who are not reintubated. 3,12,16,17In our study, we found a mortality rate of 51.4% among the patients who were reintubated, compared with 3.4% among patients who were not.
Various hypotheses have been put forward to explain the association between reintubation and the high mortality rate: complications from reintubation, clinical deterioration between extubation and reintubation, ventilator-associated pneumonia, or the adverse effects from longer durations of mechanical ventilation. 26Additionally, the mortality among our patients may have been associated with complications and changes in the central nervous system, particularly the brain, due to operative manipulation and its complications.
Another factor that might have contributed towards the high mortality rate among our patients was the need for a new surgical approach.In our study, we noted that there was an association between reintubation and the need for a new surgical procedure (58.8%).Since the primary cause of reintubation was a reduced level of consciousness, another hypothesis that may explain the reduced level of consciousness would probably be the increased intracranial pressure, which may often be a reflex of problems secondary to surgery, thus requiring a new operation.
In this study, we did not evaluate any predictive index for weaning off mechanical ventilation, which may have had some association with the outcomes among these patients.Perhaps through assessment of neuroventilatory decoupling and minute volume, other discussions inherent to the outcomes from extubation might be generated.If we had analyzed the cerebral flow and its metabolism continuously, 27 it would have been possible to have stronger support to explain the lowered level of consciousness, which was the primary cause of reintubation in these patients.
However, these resources have a high cost and are not available in all institutions.Our objective was to conduct a study that could reflect clinical practice.Through knowing the incidence This was a prospective cohort study in which all patients in the neurosurgical ICU of Hospital São Paulo, Universidade Federal de São Paulo (Unifesp), participated between July 2003 and July 2006.This study included: 1) candidates for elective surgery to treat intracranial tumors, aneurisms, arteriovenous malformations, Arnold-Chiari disease, intracranial hematomas and abscesses; 2) patients who maintained spontaneous ventilation at the preoperative evaluation; 3) patients who had undergone surgery under general anesthesia; and 4) patients in the neurosurgery ICU during the postoperative period who were on mechanical ventilation at admission.The exclusion criteria were 1) death before surgery; 2) tracheostomy performed before weaning from mechanical ventilation; and 3) unplanned extubation.This study was approved by the Research Ethics Committee of Hospital São Paulo, Universidade Federal de São Paulo, and an informed consent statement was obtained from all the patients.Continuous variables were analyzed using the independent Student t and Mann-Whitney tests.Categorical values were analyzed using the chi-square test and Fisher's exact test, with the level of significance set at 5% in all cases.

A
satisfactory daily evaluation was considered to include the following: (a) consent from the neurosurgeon responsible; (b) GCS > 8 T; (c) body temperature less than 38 °C; (d) no treatment with vasoactive drugs (dobutamine or dopamine was allowed at doses less than 5 mg/kg of body weight per minute); and (e) adequate gas exchange, as indicated by an arterial oxygen pressure (PaO 2 ) of at least 60 mmHg, with an inspired oxygen fraction of less than 0.4 and positive endexpiratory pressure (PEEP) of no more than 5 cmH 2 O.
2 O and PEEP less than or equal to 5 cmH 2 O.The parameters used to define failure or unsuccessful SBT were the presence of two of the following criteria: (a) arterial oxygen saturation (SaO 2 ) under 90%; (b) breathing rate greater than 35 breaths/min over a 10-minute period; (c) 20% decrease or increase in systolic arterial pressure; (d) presence of signs of increased respiratory work for more than 15 min; (e) sudoresis and agitation; and (f) low consciousness level (GCS < 8 T).At this time, the SBT was stopped and mechanical ventilation was restored with the previous ventilator parameters.Otherwiser, after successful conclusion of the SBT, patients were extubated after medical consent had been obtained.
surgical risk assessed according to the ASA, respiratory symptoms, prior pulmonary disease, smoking, previous neurosurgery, length of hospital stay before surgery, diagnosis, anatomical encephalic site of the operation and duration of the operation.DISCUSSION Approximately 12.5% of the patients included in the study needed reintubation, and the causes of extubation failure were lowered level of consciousness (71.5%), respiratory insufficiency (19%) and upper airway obstruction (9.5%).There were associations with female gender, GCS at the time of extubation and duration of mechanical ventilation.Reintubated patients presented longer duration of mechanical ventilation, longer stays in the ICU and in the hospital, and greater incidence of pulmonary complications, reoperation, tracheostomy and mortality.

Figure 1 .
Figure 1.Organizational chart representing inclusion and exclusion of patients in the study.

Table 1 .
Demographic characteristics of the 169 patients included in the study MV = mechanical ventilation; ICU = intensive care unit; LOS = length of stay; SD = standard deviation.