Abstract
Risk factors for reintubation in post-anaesthetic care units related to anaesthetic processes have not previously been reported. Our goal was to identify risk factors for reintubation in general surgical patients.
A time-matched, case–control study was conducted on anaesthetic patients between 2001 and 2011. One hundred and sixty-four reintubated patients were compared with 656 randomly selected controls.
Independent risk factors for reintubation were age <1 yr vs age 30–49 yr [odds ratio (OR)=16.4, 95% confidence interval (CI)=5.7–47.7], chronic pulmonary disease (OR=2.1, CI=1.1–4.0), preoperative hypoalbuminaemia (OR=4.9, CI=2.4–10), creatinine clearance <24 vs >60 (OR=4.1, CI=1.2–13.4), emergency case (OR=1.8, CI=1.0–3.1), operative time >3 vs <1 h (OR=3.0, CI=1.5–6.2), airway surgery (OR=32.2, CI=13.6–76), head and neck surgery (OR=3.4, CI=1.8–6.2), cardiac surgery (OR=3.8, CI=1.1–13.4), thoracic surgery (OR=6.3, CI=1.9–21.2), cardiac catheterization (OR=2.5, CI=1.1–5.5), ASA physical status III (OR=3.8, CI=1.4–10), and the use of certain types of neuromuscular blocking agent (P<0.001).
Age <1 yr, chronic pulmonary disease, preoperative hypoalbuminaemia, and renal insufficiency were patient factors for reintubation. Emergency case, head and neck, cardiothoracic and airway surgery, and operative time >3 h were operative factors, while certain neuromuscular blocking agents and ASA physical status III were anaesthetic factors for reintubation.
This study investigates the risk factors for reintubation in post-anaesthetic care units related to anaesthetic processes.
Risk factors were age <1 yr, chronic pulmonary disease, preoperative hypoalbuminaemia and renal insufficiency, head and neck surgery, airway surgery, cardiothoracic surgery, cardiac catheterization, emergency case, duration of operation more than 3 h, ASA physical status III, and the use of certain neuromuscular blocking agents.
Reintubation is a serious adverse respiratory event.1–4 Despite using the standard criteria of extubation after anaesthesia, reintubation still occurs in the post-anaesthetic care unit (PACU). The consequences of reintubation are important, and include increased cardiac and respiratory complications, prolonged length of stay at the PACU, intensive care unit (ICU) and hospital, prolonged mechanical ventilator support, higher costs, and increased mortality.5–13
From previous studies, risk factors for extubation failure have been identified in both medical and surgical ICU (SICU).6,13–16 However, independent risk factors for reintubation in the PACU related to anaesthesia have never been reported. If risk factors can be identified, they may be used to improve the anaesthetic process.
Our hypothesis was that risk factors for reintubation in the PACU are similar to those for reintubation in the ICU, especially SICU because the patient characteristics and operations from PACU and SICU are very similar. The objective of the study was to determine the risk factors for reintubation in the PACU among general surgical patients.
Methods
This was a record-based, time-matched, case–control study performed at Songklanagarind Hospital, Prince of Songkla University, an 853-bed tertiary care hospital in southern Thailand. After obtaining Institutional Ethics Committee approval, the anaesthetic database was used to identify all patients who required reintubation after planned extubation between January 1, 2001, and October 31, 2011.The requirement for written informed consent was waived by the Institutional Ethics Committee.
Participants
The anaesthetic database included all patients who were serviced by anaesthetists either inside or outside the operating theatres. The database consisted of two parts. The first part contained preoperative data and intraoperative data which were entered into the database upon admission to the PACU by the anaesthetists involved in the patient's intraoperative care. The second part consisted of postoperative data which were recorded by the nurse anaesthetists. When performing retrieval from the database, potential cases of reintubation were identified. The researcher collected monthly morbidity and mortality reports from the Department of Anaesthesiology. These reports included all reintubation in the PACU; thus, reintubated cases were not missed. Patients with preoperative mechanical ventilator, those who remained intubated after operation, and those who were after operation admitted directly to an ICU were excluded.
The anaesthetic records of potential reintubated cases were subsequently reviewed by an anaesthesiologist to confirm the diagnosis of reintubation. For each case, four controls that were not in the exclusion criteria were randomly selected from the remaining pool of anaesthetic patients admitted in the same year as the case. The anaesthetic and medical records of the cases and controls were reviewed, and potential risk factors for reintubation were recorded.
The potential risk factors for reintubation were classified as patient-, operation-, or anaesthetic-specific. Patient-specific factors included sex, age, weight, height, BMI, smoking status, recent preoperative upper and lower respiratory tract infection, history of cardiovascular and pulmonary diseases, and preoperative laboratory results [haematocrit levels, potassium levels, albumin levels, blood urea nitrogen (BUN) levels, and creatinine clearance]. Operation-specific factors included operative site, case type (elective or emergency), and duration of operation. Anaesthetic-specific factors included ASA physical status, the use of neuromuscular blocking agents, and the use of opioids.
Definition of variables
Reintubation was defined as intubation after extubation of a patient who had been initially tracheal intubated under general anaesthesia or combined general and regional anaesthesia. Current smoker was defined as continuing to smoke to within <6 weeks before surgery. Ex-smoker was defined as having stopped smoking for at least 6 weeks before surgery. Recent upper respiratory tract infection (URI) was defined as having URI symptoms (cough, fever, sore throat, or rhinorrhoea) within 2 weeks before surgery. Lower respiratory tract infection was defined as bronchitis or pneumonia within 1 month before surgery. A history of chronic pulmonary disease was defined as chronic obstructive pulmonary disease (COPD), asthma, or interstitial lung disease. A history of cardiovascular disease was defined as hypertension, myocardial infarction, coronary artery disease, or congestive heart failure. The presence or absence of underlying diseases such as pulmonary disease and cardiovascular disease was defined from the patient's clinical history as noted in the preoperative evaluation. Anaemia was defined as a haematocrit lower than 39% in men and 36% in women. Hypoalbuminaemia was defined as an albumin level lower than 4.0 mg%. Airway surgery was defined as direct laryngoscope, bronchoscope, or carbon dioxide laser surgery. Cardiac surgery included closed heart surgery, except for cardiopulmonary bypass circuit surgery. Other surgery included spine, laparoscopic, urologic, breast, and eye surgery. Non-depolarizing neuromuscular blocking agents were divided into two groups: aminosteroid derivatives (pancuronium, vecuronium, and rocuronium) and benzylisoquinolines (atracurium and cisatracurium).
Sample size calculation
The sample size was calculated based on having 80% power to detect an odds ratio of at least 2.0 as significant at α=0.05 for risk factors with a prevalence among controls of between 15% and 70%, with a ratio of controls to cases of 4:1. The calculated numbers of cases and controls were 133 and 532, respectively. Allowance was made for 10% unusable data, thereby requiring 148 cases and 592 controls.
Statistical analysis
Descriptive results are presented as the mean and standard deviation (sd), median and inter-quartile range (IQR), or proportion, as appropriate. Crude associations of categorical variables with reintubation were assessed using the χ2 and Fisher's exact tests. Continuous variables were assessed using Student's t-test or Mann–Whitney test for non-normally distributed variables. Collinearity diagnostics and bivariate correlation matrix were evaluated for all variables. If any variables showed multi-collinearity, only one of them was chosen to put in the multivariate analysis. Multivariate analysis was performed by fitting a logistic regression model including all variables that had P-values of <0.2 in the univariate analysis. A backward selection procedure was used to develop the final regression model, which was determined by selecting the model which had the lowest value of Akaike's information criterion at each step. From the final model, an optimum cut-point was calculated using the Youden index.17P-values of <0.05 were considered statistically significant. The data were analysed using R software version 2.13.0.
Results
Information on 147382 patients was contained in the anaesthetic database for patients serviced from the Department of Anaesthesiology between January 1, 2001, and October 31, 2011. Of these, 120210 patients were admitted to the PACU. We excluded 1303 planned ICU admission patients, 154 unplanned ICU admission patients, 765 patients who remained intubated, and 486 patients who used mechanical ventilators. Among the remaining 117502 patients, 164 reintubated patients were identified. The incidence of reintubation in the PACU was 0.14% (95% confidence interval: 0.12–0.16).
Univariate analysis revealed that for patient-specific factors, sex, age, weight, smoking status, recent respiratory tract infection (both upper and lower), previous cardiac disease, chronic pulmonary disease, preoperative anaemia and hypoabluminaemia, creatinine clearance level, and BUN level were highly associated with reintubation (Table 1). Other operative and anaesthetic-specific factors associated with reintubation were type of surgery, emergency or elective case, in-patient or out-patient, duration of operation, ASA physical status, the use of neuromuscular blocking agent, and the use of opioids (Table 2).
Patient-specific potential risk factors for reintubation. BMI, body mass index; URI, upper respiratory tract infection; BUN, blood urea nitrogen
| Variables | Reintubation (n=164) | No reintubation (n=656) | P-value |
|---|---|---|---|
| Sex [n (%)] | <0.001 | ||
| Female | 67 (40.9) | 371 (56.6) | |
| Male | 97 (59.1) | 285 (43.3) | |
| Age (yr) [n (%)] | <0.001 | ||
| <1 | 18 (11.0) | 18 (2.7) | |
| 1–10 | 16 (9.8) | 82 (12.5) | |
| 11–29 | 28 (17.1) | 158 (24.1) | |
| 30–49 | 29 (17.7) | 206 (31.4) | |
| 50–65 | 38 (23.2) | 112 (17.1) | |
| >65 | 35 (21.3) | 80 (12.2) | |
| Median weight (kg) (IQR) | 52 (37.8, 61.1) | 54.5 (45.0, 63.0) | 0.037 |
| Median height (cm) (IQR) | 155.5 (145.8, 163.2) | 157 (150.0 162.0) | 0.39 |
| BMI (kg m−2) [n (%)] | 0.638 | ||
| <28 | 149 (90.9) | 587 (89.5) | |
| 28–35 | 11 (6.7) | 57 (8.7) | |
| >35 | 4 (2.4) | 12 (1.8) | |
| Smoking status [n (%)] | <0.001 | ||
| Never | 113 (68.9) | 536 (81.7) | |
| Current | 17 (10.4) | 57 (8.7) | |
| Ex-smoker | 16 (9.8) | 37 (5.6) | |
| Not specified | 18 (11.0) | 26 (4.0) | |
| Recent URI [n (%)] | 0.195 | ||
| Yes | 7 (4.3) | 16 (2.4) | |
| No | 157 (95.7) | 640 (97.6) | |
| Lower respiratory tract infection [n (%)] | <0.001 | ||
| Yes | 11 (6.7) | 8 (1.2) | |
| No | 153 (93.3) | 648 (98.8) | |
| Underlying disease | |||
| Chronic pulmonary disease [n (%)] | <0.001 | ||
| Yes | 36 (22.0) | 42 (14.6) | |
| No | 128 (78.0) | 614 (93.6) | |
| Cardiovascular disease [n (%)] | <0.001 | ||
| Yes | 55 (33.5) | 96 (14.6) | |
| No | 109 (66.5) | 560 (85.4) | |
| Preoperative laboratory | |||
| Anaemia [n (%)] | <0.001 | ||
| Yes | 95 (57.9) | 272 (41.5) | |
| No | 68 (41.5) | 379 (57.8) | |
| No data | 1 (0.6) | 5 (0.8) | |
| Hypoalbuminaemia [n (%)] | <0.001 | ||
| Yes | 65 (39.6) | 61 (9.3) | |
| No | 25 (15.2) | 98 (14.9) | |
| No data | 74 (45.1) | 497 (75.8) | |
| BUN (mg%) [n (%)] | <0.001 | ||
| <20 | 112 (68.3) | 358 (54.6) | |
| 20–30 | 10 (6.1) | 34 (5.2) | |
| 31–40 | 8 (4.9) | 3 (0.5) | |
| >40 | 6 (3.7) | 6 (0.9) | |
| No data | 28 (17.1) | 255 (38.9) | |
| Creatinine clearance [n (%)] | <0.001 | ||
| <24 | 9 (5.5) | 11 (1.7) | |
| 25–60 | 54 (32.9) | 120 (18.3) | |
| >60 | 76 (46.3) | 278 (42.4) | |
| No data | 25 (15.2) | 247 (37.7) |
| Variables | Reintubation (n=164) | No reintubation (n=656) | P-value |
|---|---|---|---|
| Sex [n (%)] | <0.001 | ||
| Female | 67 (40.9) | 371 (56.6) | |
| Male | 97 (59.1) | 285 (43.3) | |
| Age (yr) [n (%)] | <0.001 | ||
| <1 | 18 (11.0) | 18 (2.7) | |
| 1–10 | 16 (9.8) | 82 (12.5) | |
| 11–29 | 28 (17.1) | 158 (24.1) | |
| 30–49 | 29 (17.7) | 206 (31.4) | |
| 50–65 | 38 (23.2) | 112 (17.1) | |
| >65 | 35 (21.3) | 80 (12.2) | |
| Median weight (kg) (IQR) | 52 (37.8, 61.1) | 54.5 (45.0, 63.0) | 0.037 |
| Median height (cm) (IQR) | 155.5 (145.8, 163.2) | 157 (150.0 162.0) | 0.39 |
| BMI (kg m−2) [n (%)] | 0.638 | ||
| <28 | 149 (90.9) | 587 (89.5) | |
| 28–35 | 11 (6.7) | 57 (8.7) | |
| >35 | 4 (2.4) | 12 (1.8) | |
| Smoking status [n (%)] | <0.001 | ||
| Never | 113 (68.9) | 536 (81.7) | |
| Current | 17 (10.4) | 57 (8.7) | |
| Ex-smoker | 16 (9.8) | 37 (5.6) | |
| Not specified | 18 (11.0) | 26 (4.0) | |
| Recent URI [n (%)] | 0.195 | ||
| Yes | 7 (4.3) | 16 (2.4) | |
| No | 157 (95.7) | 640 (97.6) | |
| Lower respiratory tract infection [n (%)] | <0.001 | ||
| Yes | 11 (6.7) | 8 (1.2) | |
| No | 153 (93.3) | 648 (98.8) | |
| Underlying disease | |||
| Chronic pulmonary disease [n (%)] | <0.001 | ||
| Yes | 36 (22.0) | 42 (14.6) | |
| No | 128 (78.0) | 614 (93.6) | |
| Cardiovascular disease [n (%)] | <0.001 | ||
| Yes | 55 (33.5) | 96 (14.6) | |
| No | 109 (66.5) | 560 (85.4) | |
| Preoperative laboratory | |||
| Anaemia [n (%)] | <0.001 | ||
| Yes | 95 (57.9) | 272 (41.5) | |
| No | 68 (41.5) | 379 (57.8) | |
| No data | 1 (0.6) | 5 (0.8) | |
| Hypoalbuminaemia [n (%)] | <0.001 | ||
| Yes | 65 (39.6) | 61 (9.3) | |
| No | 25 (15.2) | 98 (14.9) | |
| No data | 74 (45.1) | 497 (75.8) | |
| BUN (mg%) [n (%)] | <0.001 | ||
| <20 | 112 (68.3) | 358 (54.6) | |
| 20–30 | 10 (6.1) | 34 (5.2) | |
| 31–40 | 8 (4.9) | 3 (0.5) | |
| >40 | 6 (3.7) | 6 (0.9) | |
| No data | 28 (17.1) | 255 (38.9) | |
| Creatinine clearance [n (%)] | <0.001 | ||
| <24 | 9 (5.5) | 11 (1.7) | |
| 25–60 | 54 (32.9) | 120 (18.3) | |
| >60 | 76 (46.3) | 278 (42.4) | |
| No data | 25 (15.2) | 247 (37.7) |
Patient-specific potential risk factors for reintubation. BMI, body mass index; URI, upper respiratory tract infection; BUN, blood urea nitrogen
| Variables | Reintubation (n=164) | No reintubation (n=656) | P-value |
|---|---|---|---|
| Sex [n (%)] | <0.001 | ||
| Female | 67 (40.9) | 371 (56.6) | |
| Male | 97 (59.1) | 285 (43.3) | |
| Age (yr) [n (%)] | <0.001 | ||
| <1 | 18 (11.0) | 18 (2.7) | |
| 1–10 | 16 (9.8) | 82 (12.5) | |
| 11–29 | 28 (17.1) | 158 (24.1) | |
| 30–49 | 29 (17.7) | 206 (31.4) | |
| 50–65 | 38 (23.2) | 112 (17.1) | |
| >65 | 35 (21.3) | 80 (12.2) | |
| Median weight (kg) (IQR) | 52 (37.8, 61.1) | 54.5 (45.0, 63.0) | 0.037 |
| Median height (cm) (IQR) | 155.5 (145.8, 163.2) | 157 (150.0 162.0) | 0.39 |
| BMI (kg m−2) [n (%)] | 0.638 | ||
| <28 | 149 (90.9) | 587 (89.5) | |
| 28–35 | 11 (6.7) | 57 (8.7) | |
| >35 | 4 (2.4) | 12 (1.8) | |
| Smoking status [n (%)] | <0.001 | ||
| Never | 113 (68.9) | 536 (81.7) | |
| Current | 17 (10.4) | 57 (8.7) | |
| Ex-smoker | 16 (9.8) | 37 (5.6) | |
| Not specified | 18 (11.0) | 26 (4.0) | |
| Recent URI [n (%)] | 0.195 | ||
| Yes | 7 (4.3) | 16 (2.4) | |
| No | 157 (95.7) | 640 (97.6) | |
| Lower respiratory tract infection [n (%)] | <0.001 | ||
| Yes | 11 (6.7) | 8 (1.2) | |
| No | 153 (93.3) | 648 (98.8) | |
| Underlying disease | |||
| Chronic pulmonary disease [n (%)] | <0.001 | ||
| Yes | 36 (22.0) | 42 (14.6) | |
| No | 128 (78.0) | 614 (93.6) | |
| Cardiovascular disease [n (%)] | <0.001 | ||
| Yes | 55 (33.5) | 96 (14.6) | |
| No | 109 (66.5) | 560 (85.4) | |
| Preoperative laboratory | |||
| Anaemia [n (%)] | <0.001 | ||
| Yes | 95 (57.9) | 272 (41.5) | |
| No | 68 (41.5) | 379 (57.8) | |
| No data | 1 (0.6) | 5 (0.8) | |
| Hypoalbuminaemia [n (%)] | <0.001 | ||
| Yes | 65 (39.6) | 61 (9.3) | |
| No | 25 (15.2) | 98 (14.9) | |
| No data | 74 (45.1) | 497 (75.8) | |
| BUN (mg%) [n (%)] | <0.001 | ||
| <20 | 112 (68.3) | 358 (54.6) | |
| 20–30 | 10 (6.1) | 34 (5.2) | |
| 31–40 | 8 (4.9) | 3 (0.5) | |
| >40 | 6 (3.7) | 6 (0.9) | |
| No data | 28 (17.1) | 255 (38.9) | |
| Creatinine clearance [n (%)] | <0.001 | ||
| <24 | 9 (5.5) | 11 (1.7) | |
| 25–60 | 54 (32.9) | 120 (18.3) | |
| >60 | 76 (46.3) | 278 (42.4) | |
| No data | 25 (15.2) | 247 (37.7) |
| Variables | Reintubation (n=164) | No reintubation (n=656) | P-value |
|---|---|---|---|
| Sex [n (%)] | <0.001 | ||
| Female | 67 (40.9) | 371 (56.6) | |
| Male | 97 (59.1) | 285 (43.3) | |
| Age (yr) [n (%)] | <0.001 | ||
| <1 | 18 (11.0) | 18 (2.7) | |
| 1–10 | 16 (9.8) | 82 (12.5) | |
| 11–29 | 28 (17.1) | 158 (24.1) | |
| 30–49 | 29 (17.7) | 206 (31.4) | |
| 50–65 | 38 (23.2) | 112 (17.1) | |
| >65 | 35 (21.3) | 80 (12.2) | |
| Median weight (kg) (IQR) | 52 (37.8, 61.1) | 54.5 (45.0, 63.0) | 0.037 |
| Median height (cm) (IQR) | 155.5 (145.8, 163.2) | 157 (150.0 162.0) | 0.39 |
| BMI (kg m−2) [n (%)] | 0.638 | ||
| <28 | 149 (90.9) | 587 (89.5) | |
| 28–35 | 11 (6.7) | 57 (8.7) | |
| >35 | 4 (2.4) | 12 (1.8) | |
| Smoking status [n (%)] | <0.001 | ||
| Never | 113 (68.9) | 536 (81.7) | |
| Current | 17 (10.4) | 57 (8.7) | |
| Ex-smoker | 16 (9.8) | 37 (5.6) | |
| Not specified | 18 (11.0) | 26 (4.0) | |
| Recent URI [n (%)] | 0.195 | ||
| Yes | 7 (4.3) | 16 (2.4) | |
| No | 157 (95.7) | 640 (97.6) | |
| Lower respiratory tract infection [n (%)] | <0.001 | ||
| Yes | 11 (6.7) | 8 (1.2) | |
| No | 153 (93.3) | 648 (98.8) | |
| Underlying disease | |||
| Chronic pulmonary disease [n (%)] | <0.001 | ||
| Yes | 36 (22.0) | 42 (14.6) | |
| No | 128 (78.0) | 614 (93.6) | |
| Cardiovascular disease [n (%)] | <0.001 | ||
| Yes | 55 (33.5) | 96 (14.6) | |
| No | 109 (66.5) | 560 (85.4) | |
| Preoperative laboratory | |||
| Anaemia [n (%)] | <0.001 | ||
| Yes | 95 (57.9) | 272 (41.5) | |
| No | 68 (41.5) | 379 (57.8) | |
| No data | 1 (0.6) | 5 (0.8) | |
| Hypoalbuminaemia [n (%)] | <0.001 | ||
| Yes | 65 (39.6) | 61 (9.3) | |
| No | 25 (15.2) | 98 (14.9) | |
| No data | 74 (45.1) | 497 (75.8) | |
| BUN (mg%) [n (%)] | <0.001 | ||
| <20 | 112 (68.3) | 358 (54.6) | |
| 20–30 | 10 (6.1) | 34 (5.2) | |
| 31–40 | 8 (4.9) | 3 (0.5) | |
| >40 | 6 (3.7) | 6 (0.9) | |
| No data | 28 (17.1) | 255 (38.9) | |
| Creatinine clearance [n (%)] | <0.001 | ||
| <24 | 9 (5.5) | 11 (1.7) | |
| 25–60 | 54 (32.9) | 120 (18.3) | |
| >60 | 76 (46.3) | 278 (42.4) | |
| No data | 25 (15.2) | 247 (37.7) |
Anaesthetic and operative-specific potential risk factors for reintubation. OPD, out-patient department; IPD, in-patient department
| Variables | Reintubation (n=164) | No reintubation (n=656) | P-value |
|---|---|---|---|
| ASA physical status [n (%)] | <0.001 | ||
| I | 11 (6.7) | 163 (24.8) | |
| II | 90 (54.9) | 430 (65.5) | |
| III | 59 (36.0) | 62 (9.5) | |
| IV | 4 (2.4) | 1 (0.2) | |
| Case [n (%)] | 0.003 | ||
| OPD | 1 (0.6) | 45 (6.9) | |
| IPD | 163 (99.4) | 611 (93.1) | |
| Type [n (%)] | 0.104 | ||
| Elective | 114 (69.5) | 499 (76.1) | |
| Emergency | 50 (30.5) | 157 (23.9) | |
| Operative site [n (%)] | <0.001 | ||
| Intra-cranial | 4 (2.4) | 13 (2.0) | |
| Head and neck | 30 (18.3) | 86 (13.1) | |
| Airway | 31 (18.9) | 19 (2.9) | |
| Cardiac | 9 (5.5) | 6 (0.9) | |
| Thoracic | 11 (6.7) | 7 (1.1) | |
| Intra-abdomen | 41 (25.0) | 187 (28.5) | |
| Extremities | 9 (5.5) | 81 (12.3) | |
| Cardiac catheterization | 15 (9.1) | 86 (13.1) | |
| Other | 14 (8.5) | 171 (26.1) | |
| Duration of operation (h) [n (%)] | 0.026 | ||
| <1 | 51 (31.1) | 258 (39.3) | |
| 1–3 | 81 (49.4) | 317 (48.3) | |
| >3 | 32 (19.5) | 81 (12.3) | |
| Neuromuscular blocking agent used [n (%)] | <0.001 | ||
| None | 8 (4.9) | 193 (29.4) | |
| Succinyl choline | 6 (3.7) | 21 (3.2) | |
| Aminosteroid derivatives | 76 (46.3) | 264 (40.2) | |
| Benzylisoquinolines | 74 (45.1) | 178 (27.1) | |
| Opioid used [n (%)] | <0.001 | ||
| None | 2 (1.2) | 68 (10.4) | |
| Morphine/meperidine | 54 (32.9) | 293 (44.7) | |
| Fentanyl | 108 (65.9) | 295 (45.0) |
| Variables | Reintubation (n=164) | No reintubation (n=656) | P-value |
|---|---|---|---|
| ASA physical status [n (%)] | <0.001 | ||
| I | 11 (6.7) | 163 (24.8) | |
| II | 90 (54.9) | 430 (65.5) | |
| III | 59 (36.0) | 62 (9.5) | |
| IV | 4 (2.4) | 1 (0.2) | |
| Case [n (%)] | 0.003 | ||
| OPD | 1 (0.6) | 45 (6.9) | |
| IPD | 163 (99.4) | 611 (93.1) | |
| Type [n (%)] | 0.104 | ||
| Elective | 114 (69.5) | 499 (76.1) | |
| Emergency | 50 (30.5) | 157 (23.9) | |
| Operative site [n (%)] | <0.001 | ||
| Intra-cranial | 4 (2.4) | 13 (2.0) | |
| Head and neck | 30 (18.3) | 86 (13.1) | |
| Airway | 31 (18.9) | 19 (2.9) | |
| Cardiac | 9 (5.5) | 6 (0.9) | |
| Thoracic | 11 (6.7) | 7 (1.1) | |
| Intra-abdomen | 41 (25.0) | 187 (28.5) | |
| Extremities | 9 (5.5) | 81 (12.3) | |
| Cardiac catheterization | 15 (9.1) | 86 (13.1) | |
| Other | 14 (8.5) | 171 (26.1) | |
| Duration of operation (h) [n (%)] | 0.026 | ||
| <1 | 51 (31.1) | 258 (39.3) | |
| 1–3 | 81 (49.4) | 317 (48.3) | |
| >3 | 32 (19.5) | 81 (12.3) | |
| Neuromuscular blocking agent used [n (%)] | <0.001 | ||
| None | 8 (4.9) | 193 (29.4) | |
| Succinyl choline | 6 (3.7) | 21 (3.2) | |
| Aminosteroid derivatives | 76 (46.3) | 264 (40.2) | |
| Benzylisoquinolines | 74 (45.1) | 178 (27.1) | |
| Opioid used [n (%)] | <0.001 | ||
| None | 2 (1.2) | 68 (10.4) | |
| Morphine/meperidine | 54 (32.9) | 293 (44.7) | |
| Fentanyl | 108 (65.9) | 295 (45.0) |
Anaesthetic and operative-specific potential risk factors for reintubation. OPD, out-patient department; IPD, in-patient department
| Variables | Reintubation (n=164) | No reintubation (n=656) | P-value |
|---|---|---|---|
| ASA physical status [n (%)] | <0.001 | ||
| I | 11 (6.7) | 163 (24.8) | |
| II | 90 (54.9) | 430 (65.5) | |
| III | 59 (36.0) | 62 (9.5) | |
| IV | 4 (2.4) | 1 (0.2) | |
| Case [n (%)] | 0.003 | ||
| OPD | 1 (0.6) | 45 (6.9) | |
| IPD | 163 (99.4) | 611 (93.1) | |
| Type [n (%)] | 0.104 | ||
| Elective | 114 (69.5) | 499 (76.1) | |
| Emergency | 50 (30.5) | 157 (23.9) | |
| Operative site [n (%)] | <0.001 | ||
| Intra-cranial | 4 (2.4) | 13 (2.0) | |
| Head and neck | 30 (18.3) | 86 (13.1) | |
| Airway | 31 (18.9) | 19 (2.9) | |
| Cardiac | 9 (5.5) | 6 (0.9) | |
| Thoracic | 11 (6.7) | 7 (1.1) | |
| Intra-abdomen | 41 (25.0) | 187 (28.5) | |
| Extremities | 9 (5.5) | 81 (12.3) | |
| Cardiac catheterization | 15 (9.1) | 86 (13.1) | |
| Other | 14 (8.5) | 171 (26.1) | |
| Duration of operation (h) [n (%)] | 0.026 | ||
| <1 | 51 (31.1) | 258 (39.3) | |
| 1–3 | 81 (49.4) | 317 (48.3) | |
| >3 | 32 (19.5) | 81 (12.3) | |
| Neuromuscular blocking agent used [n (%)] | <0.001 | ||
| None | 8 (4.9) | 193 (29.4) | |
| Succinyl choline | 6 (3.7) | 21 (3.2) | |
| Aminosteroid derivatives | 76 (46.3) | 264 (40.2) | |
| Benzylisoquinolines | 74 (45.1) | 178 (27.1) | |
| Opioid used [n (%)] | <0.001 | ||
| None | 2 (1.2) | 68 (10.4) | |
| Morphine/meperidine | 54 (32.9) | 293 (44.7) | |
| Fentanyl | 108 (65.9) | 295 (45.0) |
| Variables | Reintubation (n=164) | No reintubation (n=656) | P-value |
|---|---|---|---|
| ASA physical status [n (%)] | <0.001 | ||
| I | 11 (6.7) | 163 (24.8) | |
| II | 90 (54.9) | 430 (65.5) | |
| III | 59 (36.0) | 62 (9.5) | |
| IV | 4 (2.4) | 1 (0.2) | |
| Case [n (%)] | 0.003 | ||
| OPD | 1 (0.6) | 45 (6.9) | |
| IPD | 163 (99.4) | 611 (93.1) | |
| Type [n (%)] | 0.104 | ||
| Elective | 114 (69.5) | 499 (76.1) | |
| Emergency | 50 (30.5) | 157 (23.9) | |
| Operative site [n (%)] | <0.001 | ||
| Intra-cranial | 4 (2.4) | 13 (2.0) | |
| Head and neck | 30 (18.3) | 86 (13.1) | |
| Airway | 31 (18.9) | 19 (2.9) | |
| Cardiac | 9 (5.5) | 6 (0.9) | |
| Thoracic | 11 (6.7) | 7 (1.1) | |
| Intra-abdomen | 41 (25.0) | 187 (28.5) | |
| Extremities | 9 (5.5) | 81 (12.3) | |
| Cardiac catheterization | 15 (9.1) | 86 (13.1) | |
| Other | 14 (8.5) | 171 (26.1) | |
| Duration of operation (h) [n (%)] | 0.026 | ||
| <1 | 51 (31.1) | 258 (39.3) | |
| 1–3 | 81 (49.4) | 317 (48.3) | |
| >3 | 32 (19.5) | 81 (12.3) | |
| Neuromuscular blocking agent used [n (%)] | <0.001 | ||
| None | 8 (4.9) | 193 (29.4) | |
| Succinyl choline | 6 (3.7) | 21 (3.2) | |
| Aminosteroid derivatives | 76 (46.3) | 264 (40.2) | |
| Benzylisoquinolines | 74 (45.1) | 178 (27.1) | |
| Opioid used [n (%)] | <0.001 | ||
| None | 2 (1.2) | 68 (10.4) | |
| Morphine/meperidine | 54 (32.9) | 293 (44.7) | |
| Fentanyl | 108 (65.9) | 295 (45.0) |
Multivariate analysis identified eight variables as independent risk factors for reintubation in the PACU: age <1 yr compared with age 30–49 yr, chronic pulmonary disease, preoperative hypoalbuminaemia and renal insufficiency, airway surgery, head and neck surgery, cardiac surgery, thoracic surgery, cardiac catheterization, emergency case, operative time more than 3 h compared with <1 h, ASA physical status III compared with ASA physical status I, and the use of certain neuromuscular blocking agents, particularly aminosteroid derivatives (Table 3). Of the 164 reintubated patients, 130 were extubated within 48 h, 23 had respiratory failure, three had aspiration pneumonia, and eight died within 30 days after operation from non-respiratory causes.
Final multivariate regression model showing significant risk factors for reintubation in PACU. PACU, post-anaesthetic care unit; OR, odds ratio; CI, confidence interval; Ref, reference group. *Likelihood ratio test
| Variable | OR | 95% CI | P-value* |
|---|---|---|---|
| Age (yr) (Ref: 30–49 yr) | <0.001 | ||
| <1 | 16.4 | 5.66–47.7 | |
| 1–10 | 1.98 | 0.81–4.84 | |
| 11–29 | 1.83 | 0.91–3.66 | |
| 50–65 | 0.90 | 0.44–1.84 | |
| >65 | 0.98 | 0.42–2.27 | |
| Chronic pulmonary disease | 2.10 | 1.10–4.00 | 0.026 |
| Hypoalbuminaemia | 4.86 | 2.36–10.0 | <0.001 |
| Creatinine clearance (Ref: >60) | 0.016 | ||
| 25–60 | 2.49 | 1.30–4.79 | |
| <24 | 4.08 | 1.24–13.4 | |
| Emergency case | 1.79 | 1.02–3.14 | 0.042 |
| ASA physical status (Ref: I) | 0.007 | ||
| II | 1.59 | 0.71–3.55 | |
| III | 3.78 | 1.43–10.0 | |
| IV | 11.4 | 0.93–139 | |
| Airway surgery | 32.2 | 13.6–76.1 | <0.001 |
| Head and neck surgery | 3.36 | 1.83–6.17 | <0.001 |
| Cardiac surgery | 3.80 | 1.08–13.4 | 0.035 |
| Thoracic surgery | 6.26 | 1.85–21.2 | 0.003 |
| Cardiac catheterization | 2.46 | 1.10–5.50 | 0.033 |
| Duration of operation (h) (Ref: <1) | 0.008 | ||
| 1–3 | 1.30 | 0.75–2.28 | |
| >3 | 3.00 | 1.46–6.17 | |
| Neuromuscular blocking agent used (Ref: not used) | <0.001 | ||
| Succinyl choline | 3.70 | 0.83–16.6 | |
| Aminosteroid derivatives | 7.26 | 2.67–19.8 | |
| Benzylisoquinolines | 3.89 | 1.46–10.3 |
| Variable | OR | 95% CI | P-value* |
|---|---|---|---|
| Age (yr) (Ref: 30–49 yr) | <0.001 | ||
| <1 | 16.4 | 5.66–47.7 | |
| 1–10 | 1.98 | 0.81–4.84 | |
| 11–29 | 1.83 | 0.91–3.66 | |
| 50–65 | 0.90 | 0.44–1.84 | |
| >65 | 0.98 | 0.42–2.27 | |
| Chronic pulmonary disease | 2.10 | 1.10–4.00 | 0.026 |
| Hypoalbuminaemia | 4.86 | 2.36–10.0 | <0.001 |
| Creatinine clearance (Ref: >60) | 0.016 | ||
| 25–60 | 2.49 | 1.30–4.79 | |
| <24 | 4.08 | 1.24–13.4 | |
| Emergency case | 1.79 | 1.02–3.14 | 0.042 |
| ASA physical status (Ref: I) | 0.007 | ||
| II | 1.59 | 0.71–3.55 | |
| III | 3.78 | 1.43–10.0 | |
| IV | 11.4 | 0.93–139 | |
| Airway surgery | 32.2 | 13.6–76.1 | <0.001 |
| Head and neck surgery | 3.36 | 1.83–6.17 | <0.001 |
| Cardiac surgery | 3.80 | 1.08–13.4 | 0.035 |
| Thoracic surgery | 6.26 | 1.85–21.2 | 0.003 |
| Cardiac catheterization | 2.46 | 1.10–5.50 | 0.033 |
| Duration of operation (h) (Ref: <1) | 0.008 | ||
| 1–3 | 1.30 | 0.75–2.28 | |
| >3 | 3.00 | 1.46–6.17 | |
| Neuromuscular blocking agent used (Ref: not used) | <0.001 | ||
| Succinyl choline | 3.70 | 0.83–16.6 | |
| Aminosteroid derivatives | 7.26 | 2.67–19.8 | |
| Benzylisoquinolines | 3.89 | 1.46–10.3 |
Final multivariate regression model showing significant risk factors for reintubation in PACU. PACU, post-anaesthetic care unit; OR, odds ratio; CI, confidence interval; Ref, reference group. *Likelihood ratio test
| Variable | OR | 95% CI | P-value* |
|---|---|---|---|
| Age (yr) (Ref: 30–49 yr) | <0.001 | ||
| <1 | 16.4 | 5.66–47.7 | |
| 1–10 | 1.98 | 0.81–4.84 | |
| 11–29 | 1.83 | 0.91–3.66 | |
| 50–65 | 0.90 | 0.44–1.84 | |
| >65 | 0.98 | 0.42–2.27 | |
| Chronic pulmonary disease | 2.10 | 1.10–4.00 | 0.026 |
| Hypoalbuminaemia | 4.86 | 2.36–10.0 | <0.001 |
| Creatinine clearance (Ref: >60) | 0.016 | ||
| 25–60 | 2.49 | 1.30–4.79 | |
| <24 | 4.08 | 1.24–13.4 | |
| Emergency case | 1.79 | 1.02–3.14 | 0.042 |
| ASA physical status (Ref: I) | 0.007 | ||
| II | 1.59 | 0.71–3.55 | |
| III | 3.78 | 1.43–10.0 | |
| IV | 11.4 | 0.93–139 | |
| Airway surgery | 32.2 | 13.6–76.1 | <0.001 |
| Head and neck surgery | 3.36 | 1.83–6.17 | <0.001 |
| Cardiac surgery | 3.80 | 1.08–13.4 | 0.035 |
| Thoracic surgery | 6.26 | 1.85–21.2 | 0.003 |
| Cardiac catheterization | 2.46 | 1.10–5.50 | 0.033 |
| Duration of operation (h) (Ref: <1) | 0.008 | ||
| 1–3 | 1.30 | 0.75–2.28 | |
| >3 | 3.00 | 1.46–6.17 | |
| Neuromuscular blocking agent used (Ref: not used) | <0.001 | ||
| Succinyl choline | 3.70 | 0.83–16.6 | |
| Aminosteroid derivatives | 7.26 | 2.67–19.8 | |
| Benzylisoquinolines | 3.89 | 1.46–10.3 |
| Variable | OR | 95% CI | P-value* |
|---|---|---|---|
| Age (yr) (Ref: 30–49 yr) | <0.001 | ||
| <1 | 16.4 | 5.66–47.7 | |
| 1–10 | 1.98 | 0.81–4.84 | |
| 11–29 | 1.83 | 0.91–3.66 | |
| 50–65 | 0.90 | 0.44–1.84 | |
| >65 | 0.98 | 0.42–2.27 | |
| Chronic pulmonary disease | 2.10 | 1.10–4.00 | 0.026 |
| Hypoalbuminaemia | 4.86 | 2.36–10.0 | <0.001 |
| Creatinine clearance (Ref: >60) | 0.016 | ||
| 25–60 | 2.49 | 1.30–4.79 | |
| <24 | 4.08 | 1.24–13.4 | |
| Emergency case | 1.79 | 1.02–3.14 | 0.042 |
| ASA physical status (Ref: I) | 0.007 | ||
| II | 1.59 | 0.71–3.55 | |
| III | 3.78 | 1.43–10.0 | |
| IV | 11.4 | 0.93–139 | |
| Airway surgery | 32.2 | 13.6–76.1 | <0.001 |
| Head and neck surgery | 3.36 | 1.83–6.17 | <0.001 |
| Cardiac surgery | 3.80 | 1.08–13.4 | 0.035 |
| Thoracic surgery | 6.26 | 1.85–21.2 | 0.003 |
| Cardiac catheterization | 2.46 | 1.10–5.50 | 0.033 |
| Duration of operation (h) (Ref: <1) | 0.008 | ||
| 1–3 | 1.30 | 0.75–2.28 | |
| >3 | 3.00 | 1.46–6.17 | |
| Neuromuscular blocking agent used (Ref: not used) | <0.001 | ||
| Succinyl choline | 3.70 | 0.83–16.6 | |
| Aminosteroid derivatives | 7.26 | 2.67–19.8 | |
| Benzylisoquinolines | 3.89 | 1.46–10.3 |
Using the final regression model, the area under the receiver operating characteristic (ROC) curve was 0.881, which indicated good predictive ability (Fig. 1). The best cut-point for this model when applied to the patient mix in our samples was determined to correspond to a predicted probability of reintubation of 0.222, giving a specificity of 82% and a sensitivity of 79%.
ROC curve of the final logistic regression model predicting reintubation in PACU. The curve is expressed as a solid line. AUC, area under the curve.
ROC curve of the final logistic regression model predicting reintubation in PACU. The curve is expressed as a solid line. AUC, area under the curve.
Discussion
The results from this study showed that age <1 yr, chronic pulmonary disease, preoperative hypoalbuminaemia and renal insufficiency, head and neck surgery, airway surgery, cardiothoracic surgery, cardiac catheterization, emergency case, duration of operation more than 3 h, ASA physical status III, and the use of certain neuromuscular blocking agents increased the risk of reintubation in the PACU. The risk factors for reintubation in the PACU from our study were similar to those of reintubation and extubation failure in the ICU. Only one previous study identified risk factors for reintubation in the operating theatre;18 therefore, risk factors for extubation failure or reintubation in ICU were used to compare with our results.
In this study, patient factors, namely age <1 yr, chronic pulmonary disease, and preoperative hypoalbuminaemia and renal insufficiency, were independent risk factors for reintubation in PACU. Patients aged <1 yr had a significantly higher risk for reintubation than those in other age groups, a finding similar to two other studies.13,19 Patients with chronic pulmonary disease had a significantly higher risk for reintubation, a result similarly found in three previous studies.18,20,21
Our results are comparable with previous studies in that preoperative renal insufficiency and hypoalbuminaemia are significant independent risk factors for reintubation.21,22 Renal insufficiency may result in impaired excretion of anaesthetic agents which would prolong the duration of the drugs, while hypoalbuminaemia reflects poor metabolic reserve.
Three operation-specific factors, emergency case, duration of surgery more than 3 h, and type of surgery, such as airway, head and neck, thoracic, cardiac surgery, and cardiac catheterization, were independent risk factors for reintubation. Two previous studies showed that a longer operative time was related to a higher risk of reintubation.20,22 In our study, we found that emergency case, airway surgery, head and neck surgery, and thoracic surgery increased the risk for reintubation compared with other sites, a finding similar to the other studies.18,19,21,22 Airway oedema, a cause of reintubation, is common after airway surgery.23 Cardiothoracic surgery disturbs the cardiopulmonary system leading to reintubation by impairing the respiratory muscle capacity and airway protection, and also by causing cardiac dysfunction.24 Unlike two other studies,19,22 intra-abdominal and intracranial surgery were not identified as independent risk factors for reintubation, possibly because of the small number of patients who had these types of surgery in this study.
The use of neuromuscular blocking agent and ASA physical status III were significant anaesthetic-specific risk factors for reintubation. Despite reverse neuromuscular blocking agent drugs and the standard criteria for extubation being used in every surgical patient, using an intraoperative neuromuscular blocking agent, either depolarizing or non-depolarizing, was a significant and independent risk factor for reintubation in the PACU, a finding similar to Rose and colleagues'22 study. Ting and colleagues18 also showed that patients with ASA physical status III had a significantly higher risk for reintubation than healthy patients.
The limitations of the study are that some confounding factors might not have been identified, although we collected many diagnostic laboratory tests, such as albumin level, potassium level, creatinine, and BUN level. The effects of unknown or unmeasured confounders on the observed association, however, cannot be excluded. Being a case–control study, a conclusion about causality cannot be made. Also, some variables, such as the preoperative laboratory tests, had missing values because they were not required in young, healthy patients, although no records were omitted from the modelling process since all laboratory-related variables were categorized. Finally, our sample size, although fairly large, was probably inadequate to test for differences in some subgroups.
The strengths of this study are that it included general surgical patients, cases and controls were selected from a large database, and multivariate analysis was used to adjust for potential confounding factors. The external validity should be high, allowing the findings to be applied in general surgical patients as a wide variety of operative procedures were included. Both cases and controls had the same quality of data because they were selected from the same source.
In conclusion, this study identifies patient factors, including age <1 yr, chronic pulmonary disease, preoperative hypoalbuminaemia, and renal insufficiency, as independent risk factors for reintubation. Emergency case, airway, head and neck, cardiothoracic surgery, and duration of operation more than 3 h were operation-specific risk factors of reintubation. Anaesthetic factors, such as ASA physical status III and the use of certain neuromuscular blocking agents, increased the risk for reintubation in the PACU.
Declaration of interest
None declared.
Funding
This study was supported by Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand.
