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Maxillo-mandibular fixation (MMF) is a procedure still routinely practiced in developing countries.
To determine the variations in pulmonary functions readings between cases treated under general anesthesia (GA) and those treated under local anesthesia (LA).
A descriptive hospital-based study of 106 patients was carried out from January 2011- December 2012. Information was obtained using a questionnaire and all study subjects had their baseline lung functions and their post-operative daily lung function parameters measured for the first week and then weekly for the next five weeks. The data obtained were analyzed using SPSS version 16 and a P-value of ≤0.05 was considered significant.
A total of 85 males and 21 females participated in the study. The means for age was 30.62±8.06, weight 63.92± 9.96 and BMI 23.21± 3.14 while the means for the pre-operative FVC, FEV1, and PEFR were 3.71 ± 0.70, 3.14± 0.51 and 8.18± 1.61 respectively. There was a statistically significant drop (p< 0.05) in the FVC, FEV1 and PEFR in the first post operative week. The drop in the lung function parameters were similar between the GA group and the LA group.
Maxillo-mandibular fixation causes a significant fall in pulmonary function parameters especially in the first 48 hours post-operatively irrespective of whether general or local anaesthesia was used at surgery. The pulmonary functions should be further monitored for more than 48 hours after surgery.
Ventilatory pulmonary function tests are useful to detect, differentiate and measure the degree of functional impairment of an individual1. Anesthesia on its own is known to affect respiration by changing arterial oxygenation in either spontaneous or controlled breathing patients2. General anaesthesia, if not properly managed with or without the use of neuromuscular blocking drugs, results in the reduction of airway patency due to the relaxation of the pharyngeal muscles and posterior displacement of the tongue. The ability to manage secretions is also lost, and saliva and mucous can obstruct the oropharynx. The loss of the cough reflex also allows secretions (or refluxed gastric contents) onto the vocal cords causing laryngospasm; It can also allow the secretions to enter the trachea and lungs causing symptoms which extend into the postoperative period3.
Maxillo-mandibular fixation (MMF) as part of the treatment protocol for jaw fractures, is still quite common in Nigeria due to the relative affordability of the treatment procedure by patients and the fact that bone plates are scarce, expensive and difficult to afford by the patients4,5. However, MMF itself would cause obstruction of the airway and an increase in airway resistance of the mouth when compared with the nose with MMF in place6.
This study was therefore carried out to determine if there was any difference in the degree of functional lung impairment in patients treated under GA and LA.
The study was a descriptive cross-sectional study from January 2011 to December 2012. The study was approved by the Hospital Ethics Committee. All the patients also gave written informed consent. Information collected included socio-demographic and anthropometric variables such as sex, age, height, weight and body mass index (BMI).
All consecutive patients aged 18 - 65 years that had radiologic and/or clinical evidence requiring Maxillo-mandibular fixation (MMF) and were free of other respiratory symptoms were recruited into the study. However, for the purpose of this study, individuals that were obese7 (Body mass index (BMI) ≥30kg/m2), calculated as weight in kilogrammes/ height in (meters)2, smokers or had evidence of previous pulmonary diseases like asthma, allergic bronchitis and chronic obstructive pulmonary disease, among others were excluded. A total of 106 subjects who presented at the maxillofacial surgery outpatient clinic as well as the Accident and emergency who met the inclusion criteria during the 2 years period were purposively recruited into the study. The patients were given the option to opt for general anesthesia or local anesthesia. All the subjects had their pulmonary function parameters (Forced vital capacity -FVC, Forced expiratory flow rate in one second- FEV1 and Peak expiratory flow rate -PEFR) measured.
All the subjects standing heights were measured in meters without shoes and their body weights in kilograms (with clothes on) using the measuring scale (Height and Weight) manufactured by Health O Meter, Inc. Bridgeview, Illinois USA. The equipment used to measure the lung function parameters was the Spirometer (Spiro lab III TM diagnostic Spirometer series MIR009 with a color liquid crystal display (LCD) and Winspiro Pro PC Software-enhanced. The equipment was in compliance with the American Thoracic Society and European Thoracic Society 2005 statement on spirometry8. All the lung function readings were taken with the patient in the sitting position9. Patients had their readings taken from a day pre-operatively and then daily post operatively for the 1st week. These were followed by serial weekly readings for the next 6 weeks (6th week being the day the MMF was removed). The patients did not receive steroids either pre-operatively or post operatively.
Statistical analyses were performed using the statistical package for social science (SPSS version 16; SPSS inc. Chicago, Illinois. The means and standard deviations of physical characteristics and ventilatory functions were determined in both men and women, these mean values were compared using students t-test. Statistical significance was inferred at p ≤0.05.
A total of 106 patients comprising 85 males and 21 females participated in the study. The means for age was 30.62±8.06, weight 63.92± 9.96 and BMI 23.21± 3.14. While the means for the Pre-operative FVC, FEV1, and PEFR were 3.71 ± 0.70, 3.14± 0.51 and 8.18± 1.61 respectively. Overall, there was a statistically significant drop especially in the first 48 hours in the FVC, FEV1 and PEFR. However, the difference in the lung function parameters was not significant (p > 0.05) between the GA and LA groups (Tables 1 & 2 and Figures 1, 2 &3). This fact was further buttressed by the overlapping in the error bars as shown in Figures 4, 5 and 6 depicting the error bars at each of the days for the first week and then weekly till the 6th week for the lung function parameters measured. It demonstrated the degree of variation from the mean at mean ± 1 SE of the values measured.
This study was a descriptive cross-sectional study, carried out to determine if there was any difference in the degree of functional lung impairment in patients with maxillo-mandibular fixation (MMF) treated under GA and LA. This is because conventional wire-based fixations using eyelets, or multiple ligatures in association with arch bars is known to create good quality MMF and is still being routinely practiced in the developing world10,11. In addition, a literature search revealed that so far only one author12 in our environment has attempted to study the pulmonary function in patients treated with MMF. However, the instrument used in measuring the pulmonary function was a vitalograph as against the Spirolab III we used in our study which is more efficient, and it did not measure the effect of the type of anesthesia used in the management of patients with MMF. Most patients with MMF have been known to complain of feeding and breathing difficulty among others in the immediate postoperative period13,14. Some authors13,14 had shown that respiratory function was severely affected by MMF in postoperative patients. This had been attributed to the reduction in the size of the airway caused by lingual or para-pharyngeal oedema or hematoma in addition to the effects of anesthesia on the airway3 although this is true for GA and not necessarily for LA.
Spirometry is the most commonly ordered lung function test and the most commonly measured lung function parameters on spirometry are the forced vital capacity (FVC), forced expiratory volume in one second (FEV1) and the peak expiratory flow rate (PEFR);15,16 these were the parameters measured in this study. The results of this study showed pulmonary function readings that showed moderate airway obstruction with a statistically significant fall in the FVC, FEV1 and PEFR from the pre-operative value especially in the first 48 hours as shown in Figs. 1, 2 and 3. The lowest pulmonary function readings were observed on the second postoperative day with a statistically significant fall in FVC, FEV1 and PEFR (P< 0.05). These observed differences in the pulmonary function readings from this study in the immediate postoperative period may be attributed to airway obstruction from edema of the respiratory tract and difficulty expectorating sputum, in addition to oozing from the intra-oral surgical wounds which sometimes irritates the patient's larynx thereby initiating laryngospasm17,18. The effect of pain was not considered as a factor that could affect the respiratory function in the patients as they were placed on adequate analgesia using non-steroidal analgesics which have been known to have no effect on pulmonary functions19. The fall in the pulmonary function values observed in the general anaesthesia (GA) group and the local anaesthesia (LA) group were comparable with both having their lowest values on the 2nd post operative day. However, there was a slightly faster recovery of pulmonary function in the LA group than the GA group (Figs. 1, 2 and 3). The reduction in the pulmonary function parameters seen in the patients that were treated under G.A could be attributed to the fact that general anaesthesia causes respiratory impairment affecting both oxygenation and elimination of carbon dioxide1,19. This, it does by its role in causing loss of consciousness with resultant relaxation of jaw and pharyngeal muscles thereby leading to the loss of cough reflex .The posture of patient under general anesthesia also leads to a reduction in the contribution of the rib cage and the diaphragm to the work of respiration20.
On the other hand it would have been expected that patients who were treated under LA should not have a comparable fall in their respiratory function parameters as those treated under GA but this was not the case in the present study. The fall in the pulmonary function parameters were comparable between the GA group and the LA group (Figs. 4, 5 and 6). Search of the literature have shown that local anesthesia on its own in normal doses does not affect pulmonary functions20,21. So suffice it to say that the decline in pulmonary functions observed in these patients treated under Local anesthesia, may be as a result of the problems of MMF as earlier discussed rather than the type of anesthetic agent used.
The limitation of this study was the small sample size of the patients treated under local anesthesia. We recommend in future that a comparative study with a larger number of patients treated under LA can be carried out to further validate these findings.
In conclusion, maxillo-mandibular fixation causes a significant fall in pulmonary function parameters especially in the first 48 hours post-operatively irrespective of whether general or local anaesthesia was used at surgery. The pulmonary functions should be further monitored for more than 48 hours after surgery.
Competing Interests: The authors have declared that no competing interests exist.
Grant support: None