Print version ISSN 0034-7094
Rev. Bras. Anestesiol. vol.57 no.5 Campinas Sept./Oct. 2007
Respiratory complications in patients with cerebral palsy undergoing general anesthesia*
Complicaciones respiratorias en pacientes con parálisis cerebral sometidos a la anestesia general
Sérgio Silva de Mello, TSAI; Ronaldo Soares Marques, TSAI; Renato Ângelo Saraiva, TSAII
da Rede Sarah de Hospitais do Aparelho Locomotor
IICoordenador de Anestesiologia da Rede Sarah de Hospitais do Aparelho Locomotor
BACKGROUND AND OBJETIVES: Anesthesia in patients with cerebral palsy
(CP) poses a challenge for the anesthesiologist. The objective of this prospective
study was to determine the prevalence and risk of respiratory complications
in children with CP undergoing general inhalational anesthesia for computed
METHODS: Patients with ages ranging from 1 to 17 years, physical status ASA I to III, undergoing general inhalational anesthesia with sevoflurane and laryngeal mask for a CT scan from June 2002 to June 2003, participated in this study. Patients were divided in 3 groups: quadriplegic CP (CPQ), other types of CP (CPO), and patients without CP (NCP). Parents or guardians answered a questionnaire that assessed the past medical history of the patient, upper respiratory infections (URI), asthma, seizures, oropharyngeal dysfunction, gastroesophageal reflux, etc. Data on the incidence and severity of respiratory complications were gathered prospectively (cough, bronchospasm, laryngeal spasm, hypoxemia, aspiration, etc). The size of the study group was calculated for an expected 5% incidence in the NCP group, with a 15% difference among groups (a = 0.05 and b = 0.1), using the Chi-square test, Fisher exact test, and test t Student.
RESULTS: Two hundred and ninety patients, divided in three groups, participated in this study. Groups were composed of: CPQ = 100 patients, CPO = 79 patients, and NCP = 111 patients. There were no differences on the prevalence of respiratory infections among the CPQ (4%), CPO (8.9%), and NCP (7.3%) groups. There was a correlation between the presence of URI and the development of complications (relative risk of 10.71).
CONCLUSIONS: Children with cerebral palsy with spastic quadriplegia do not seem to have an increased risk of respiratory complications during general inhalational anesthesia with sevoflurane and laryngeal mask. This study confirms URI as a risk factor for the development of those complications.
Key Words: ANESTHESIA, General: inhalation; COMPLICATION: respiratory; DISEASES, Neurologic: cerebral palsy.
JUSTIFICATIVA Y OBJETIVOS: La anestesia en pacientes con parálisis
cerebral (PC) puede representar un desafío para el anestesiólogo.
Este estudio prospectivo tuvo como objetivo determinar la prevalencia y el riesgo
de complicaciones respiratorias en niños con PC sometidos a anestesia
general inhalatoria para tomografía computadorizada.
MÉTODO: Participaron del estudio pacientes con edades entre 1 y 17 años, estado físico ASA I a III, sometidos a AGI con sevoflurano y máscara laríngea para TC en el período de junio/2002 a junio/2003, divididos en 3 grupos: PC tetraplégicos (PCT), Otros tipos de PC (PCO), y paciente sin PC (NPC). Los padres o responsables respondieron a un cuestionario con preguntas sobre el historial médico de los pacientes, infección de vías aéreas superiores (IVAS), asma, convulsión, no coordinación oro faríngea, reflujo gastroesofágico, etc. Datos sobre la incidencia y la gravedad de las complicaciones respiratorias fueron recolectados proscpectivamente (tos, bronco espasmo, laringo espasmo, hipoxemia, aspiración). La muestra fue calculada para una incidencia esperada de 5% en el grupo NPC, con una diferencia de 15% entre los grupos (a = 0,05 y b = 0,1), utilizando los tests del Chi-cuadrado, exacto de Fisher y t de Student.
RESULTADOS: Conformaron la muestra 290 pacientes divididos en los grupos de la siguiente forma: PCT 100, PCO 79 y NPC 111. No hubo diferencia en la prevalencia de complicaciones respiratorias entre los grupos PCT (4%), PCO (8,9%) y NPC (7,3%). Hubo una asociación entre la presencia de IVAS y la incidencia de complicaciones (riesgo relativo 10,71).
CONCLUSIONES: Niños con parálisis cerebral tipo tetraplegia espástica no parecen correr riesgo aumentado de complicaciones respiratorias durante la anestesia general inhalatoria con sevoflurano y máscara laríngea. El estudio confirma IVAS como factor de riesgo para la incidencia de esas complicaciones.
Cerebral palsy (CP) represents a group of disorders in the development of movements and posture, secondary to non-progressive changes in the developing brain of fetuses and children, which limits activities. This motor disorder is frequently accompanied by changes in sensation, cognition, communication, perception, behavior, and seizures1. The incidence of children who survive organic aggressions endured in the pre-, peri-, or post-natal period has not changed in the last decades in developed countries2. During the course of their lives, a significant number of those patients undergoes anesthesia for propaedeutical or therapeutic purposes. The presence of diseases associated with the cerebral lesion, such as gastroesophageal reflux (GERD), oropharyngeal dysfunction, and accumulation of secretion, besides seizures and motor incoordination, can contribute to the increase in the incidence of respiratory complications during general anesthesia in those patients 3,4.
The goal of this study was to determine the prevalence of respiratory complications in children with CP undergoing general inhalational anesthesia (GIA) for CT scan compared to healthy children. Besides that, other risk factors related with the development of those complications were also evaluated.
This study was approved by the Ethics Committee of the Institution, and parents or legal guardians signed the informed consent. The study population was composed of 290 patients, with ages ranging from 1 to 17 years, scheduled for a CT scan of the brain under general anesthesia, from June 1st, 2001 to June 1st, 2002; patients were divided in 3 groups: patients with cerebral palsy with spastic quadriplegia (CPQ); patients with other forms of CP, i.e., spastic diplegia, spastic hemiplegia, and choreoathetosis (CPO); and children without CP (NCP). Patients with genetic syndromes, other diseases affecting the central nervous system (CNS), signs of upper respiratory infection (URI) with systemic repercussions, or bacterial infection of the lower airways, were excluded from the study.
Before the procedure, the legal guardians of the patients were asked to fill out a study form containing demographic information about the family, history of current or recent URI (< 3 weeks), asthma, prematurity (< 37 weeks), and smoking history of the parents. The presence of asthma, oropharyngeal dysfunction diagnosed by videofluoroscopy, severe GERD diagnosed by endoscopy, use of anti-reflux medication, seizures and the use of anti-seizure medications, and history of recurring pneumonia and allergies were also evaluated. The type of CP was classified based on the data in the charts of the patients and confirmed with the patient's attending.
Anesthesia Every patient underwent general inhalational anesthesia with sevoflurane associated with N2O, in a circuit without valves and without CO2 absorber, monitoring of cardiovascular and respiratory parameters, and the final expired concentration (alveolar) of the anesthetic was maintained at 0.5 CAM for the duration of the procedure. Maintenance of the airways was accomplished with a laryngeal mask, allowing spontaneous ventilation during the exam, with PETCO2 and SpO2 levels within normal limits. Eventual difficulties during insertion and adaptation of the laryngeal mask were recorded, as well as the duration of the anesthesia.
Characterization of respiratory events The following signs and symptoms were considered ventilatory problems and recorded as such in the anesthesia and other appropriate forms: hypoxemia, defined as SpO2 < 90% for more than 20 seconds, laryngeal spasm, bronchospasm, severe coughing for more than 15 seconds, and clinical evidence of pulmonary aspiration of gastric contents. The time and severity of the intercurrence were also recorded: induction, maintenance, awakening, and post-anesthetic (1-4); without intercurrence, mild, moderate or severe (1-4).
The degree of the intervention was also recorded: 1. Simple: oxygen (O2) by mask; 2. Moderate: O2 by mask + succinylcholine or atropine; 3. Complex: O2 + drugs + tracheal intubation; 4. Cardiopulmonary resuscitation (CPR).
The success of the measures was evaluated throughout the evolution period: 1. Favorable; 2. Unfavorable sequela or death. The following parameters were compared: frequency of complications, time of onset, type of intervention needed, and evolution.
The software SPSS®, version 10.0.1, was used for the statistical analysis. Assuming that the risk of respiratory complications in children with CP would be approximately 5%, and that the prevalence in children with milder forms of CP would be similar, we expected the empirical prevalence to be at least four times greater in children with the most severe form of CP (spastic quadriplegia). Considering a power of 0.8 (1-b) and a = 0.05, the suggested study population would be composed by 227 children (76 per group) to identify possible differences in the rates of anesthetic complications among the three groups. The Chi-square test, Fisher exact test, and ANOVA were used. Results were evaluated considering significant a level of 5% (a = 0.05). The relative risk (RR) for the risk factors of interest was determined. Relative risk is the incidence of complication in a group of individuals divided by the incidence in the other group, and it is used to express the power of the association between two events, in this case the parameter versus the complication. It indicates how many times greater is the risk of an event in a group compared with another group. The farther this value is from one, the higher the correlation.
The study population was composed of 290 patients, with ages ranging from 1 to 17 years (4.2 ± 3.51), 100 in the CPQ group, 79 in the CPO, and 111 in the NCP. Demographic parameters in all three groups were similar, except age, which was greater in the CPQ group (Table I).
Table II shows the incidence of risk factors. Parents who smoked, asthma, and seizures were the most prevalent risk factors in this population.
Nineteen patients (6.6%) presented at least one of the following respiratory complications: cough, hypoxemia, laryngeal spasm, or aspiration. Some patients developed more than one complication. Patients did not develop bronchospasm. Cough was the most frequent complication. Table III shows the distribution of those complications among the three groups.
The majority of complications developed during the induction or awakening, as is demonstrated in Table IV. Some patients developed complications in more than one moment of the procedure.
There were no statistically significant differences in the risk of respiratory complications among patients with CP and those without CP (p = 0.912). The prevalence of complications among the groups was 4.0% (CPQ), 8.9% (CPO), and 7.2% (NCP). There were no differences in the risk of respiratory complications among the three groups (p = 0.401). All complications were handled properly and evolved without sequelae. Only one patient required tracheal intubation.
Among the risk factors, only URI demonstrated a statistical association with the development of respiratory complications (Table V). The prevalence of URI among the groups was 7% (CPQ), 19.0% (CPO), and 16.2% (NCP).
Only twelve of the 40 patients, i.e. 30%, who presented URI developed respiratory complications. The relative risk of patients with URI of developing a complication was estimated as 10.71. This datum suggests a strong correlation between the presence of URI and the development of respiratory complications; in this study population, patients with respiratory infection presented a risk 10 times greater of developing respiratory complications, when compared with patients without URI.
Although the incidence of CP has remained constant in developed countries, despite the advances in medicine, there are few prospective studies in the literature regarding anesthesia in those patients. Therefore, textbooks on the subject present a brief discussion, and very often present statements that have not been widely documented or that are based on weak evidence 5-7.
The effects of some of the drugs used in anesthesia in patients with CP, such as neuromuscular blockers 8,9 and halogenated compounds 10-12, have already been studied. There are also, in the medical literature, studies on the complications of specific surgical procedures in those patients 13. However, there are no studies demonstrating specific effects of CP and related disorders on the development of anesthetic complications, especially respiratory complications.
The classification of CP considers, mainly, the topography, motor deficit, and severity of clinical manifestations 14. Spastic quadriplegia is the most severe form of CP, and patients with this form of the disease have important cerebral lesions and more associated disorders.
Stasikelis et al. analyzed the factors related with the development of short term complications in patients with severe forms of CP undergoing osteotomies. Only complications related to the surgical procedure, such as fractures and decubitus ulcers, besides death, were analyzed. Of the 79 patients in the study, three died 5 months later of unknown causes and 17 (25%) developed some of the complications mentioned before. The mean age of the children who developed any complication was 105 months. The main factors considered risk factors were the presence of gastrostomy and being on a wheel chair, indicating patients with more severe neurologic damage. However, this study focused on orthopedic complications, and did not evaluate complications related with the anesthesia; therefore, their results cannot be extrapolated to the present study.
In our study, we tried to demonstrate whether the different types of CP could be considered risk factors for the development of respiratory complications during general anesthesia, not only due to the neurological damage, but also secondary to the problems associated with their baseline condition. Despite the recurring concern of revision papers regarding the influence of those problems in the possible increased rate of complications 15, the results of the present study did not confirm this suspicion.
In order to better evaluate those effects, children with spastic quadriplegia were in a group of their own, separated from patients with milder forms of CP and from children without CP. Analysis of the results did not demonstrate any differences in the rate of complications among the study groups. The results suggest that CP, regardless of the clinical type, is not a risk factor for the increased rate of respiratory complications during general anesthesia. The rate of complications in patients with the type of CP that presents more severe systemic involvement (spastic quadriplegia) was similar to those patients with milder types of CP or without CP. All three groups presented a rate of complication similar to that reported in the literature 16.
Some factors might have contributed to the results of this study. Patients were anesthetized with sevoflurane and laryngeal mask. Sevoflurane causes little irritation of the airways, and has a wide safety margin, allowing a trouble free induction and fast arousal 17. Tait et al. demonstrated that handling of the airways with the laryngeal mask also seems to reduce respiratory complications during general anesthesia when compared with tracheal intubation, especially in patients with URI 18.
Besides, all patients had a CT scan done, a short lasting procedure that has no painful stimuli. This uniformity related with the procedure and anesthesia allowed for better evaluation of the parameters studied, such as reduction of the factors that could cause any problems caused by the method used.
Other factors regarding the components of the cohort and CP that could have contributed to an increase in the number of complications were also evaluated. The presence of oropharyngeal dysfunction and gastroesophageal reflux, considered probable risk factors for the development of complications 3, were not responsible for an increase in the rate of complications.
Likewise, prematurity, parents who smoke, and asthma did not cause an increase in the rate of those complications. Although prior studies have identified prematurity as an isolated risk factor in patients with URI for an increase in complications, the true reasons of this result were not clear 16. Skolnick et al. reported an increase in the prevalence of respiratory complications during general anesthesia in children with passive exposure to cigarette smoke 19. In our study, passive exposure was not an additional risk factor for respiratory complications. However, one should take into account the lack of report of this variable by parents or legal guardians, who would be concerned about the negative impact of their smoking habit in the health of their children 16.
The only risk factor associated with an increase in the prevalence of respiratory complications in the present study was the presence of infection of the airways. The prevalence of respiratory complications was higher in patients with symptoms of URI, which corroborates the results of prior studies 16,20,21. The majority of complications occurred during induction or awakening but, similar to other studies, there were no severe complications, and all of them were properly managed, with a good evolution, and resolved without sequelae. The increased prevalence, in this study, of respiratory complications in patients with URI (patients without CP and with other forms of CP) strengthens the possible cause/effect relationship between those factors.
The present study has some limitations. Patients were not distributed at random and the evaluation was not double blind, what might have influenced the selection of the observer. However, the order of patient entry in the study was not dependent on the will of the observer, and the exams were consecutively performed during one year. Besides, the expressive number of quadriplegic CP patients, which is not found in any other prospective study on anesthesia in CP, suggests that, if there were a clinically significant difference among the groups regarding the rate of complications, this would be evident in the present study.
The diagnosis of CP can also raise some doubts regarding their classification, especially in less severe cases. However, we tried to use standard clinical definitions 1, and confirmed the diagnosis with the attending physicians. The information in the charts of the patients, including diagnostic imaging, was used to confirm the clinical picture. Besides, patients with spastic quadriplegia were not difficult to diagnose, due to the severity of the motor and neurologic deficit.
The results of this study suggest that, even in the most severe types, CP does not represent a risk factor for the development of respiratory complications during general anesthesia, especially in procedures of short duration, such as a CT scan. It confirmed that URI is an important risk factor for the development of those complications during general anesthesia. Future studies might demonstrate whether those results are valid for other anesthetic-surgical procedures in patients with CP.
We would like to acknowledge the help of the statistician Luiz Sérgio Vaz on the interpretation of the results.
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Dr. Sérgio Silva de Mello
Hospital Sarah Belo Horizonte Área de Anestesiologia
Av. Amazonas, 5.953 Gameleira
30510-000 Belo Horizonte, MG
Submitted em 27 de outubro de 2006
Accepted para publicação em 26 de junho de 2007
* Received from Rede Sarah de Hospitais do Aparelho Locomotor, Unidade Belo Horizonte, MG