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On-line version ISSN 1806-907X
Rev. Bras. Anestesiol. vol.54 no.2 Campinas Mar./Apr. 2004
Tracheal intubation conditions at 60 seconds in children, adults and elderly patients*
Evaluación de las condiciones de intubación traqueal con rocuronio a los 60 segundos en niños, adultos y ancianos
Maria Cristina Simões de Almeida, TSA, M.D.I; Rogério Silveira Martins, TSA, M.D.II; Ana Lúcia Costa Martins, M.D.II
IDoutora em Medicina pela Universidade
Johannes Gutenberg-Alemanha, Professora Adjunta da UFSC
IIAnestesiologista do Hospital de Clínicas de Porto Alegre
BACKGROUND AND OBJECTIVES:
Rocuronium has the fastest onset as compared to all other available nondepolarizing
neuromuscular blockers, allowing tracheal intubation time similar to succinylcholine's.
In addition to vocal cords relaxation, it is also important that there is no
tube reactions (bucking) or coughing after its placement, in order to achieve
fast and safe tracheal intubation. This study aimed at comparing intubation
conditions after 0.6 mg.kg-1 rocuronium at 60 seconds in children,
adults and elderly patients.
METHODS: Following premedication with midazolam, routine monitoring and induction with fentanyl and propofol, intubation conditions at 60s were evaluated according to clinical criteria in 60 ASA I-III patients aged 1 to 88 years who received 0.6 mg.kg-1 rocuronium in 5 seconds. Patients were divided in three groups according to age: Group 1 (G1) children up to 12 years of age; Group 2 (G2), adults aged 18 to 65 years; Group 3 (G3) patients above 65 years of age. The following parameters were evaluated: tracheal intubation conditions by clinical criteria, blood pressure and pulse measured before induction (control), after induction, after rocuronium injection, 3 and 5 minutes after tracheal intubation.
RESULTS: All patients were successfully intubated in 60s, but clinically acceptable conditions in 100% of cases were only achieved in adults and elderly patients. Three children were classified as having unacceptable conditions due to sustained cough for more than 10 seconds. There were no significant changes in blood pressure or pulse during the study.
CONCLUSIONS: In the conditions of our study, 0.6 mg.kg-1 rocuronium was sufficient for tracheal intubation in 60 seconds in adult and elderly patients. It was, however, insufficient for clinically acceptable tracheal intubation conditions in 60 seconds in 100% of children.
Key Words: NEUROMUSCULAR BLOCKERS, Nondepolarizing: rocuronium; TRACHEAL INTUBATION
JUSTIFICATIVA Y OBJETIVOS:
El rocuronio presenta un inicio de acción mas rápido que todos los
otros bloqueadores neuromusculares adespolarizantes disponibles comercialmente,
permitiendo la intubación traqueal en tiempo similar al de la succinilcolina.
Además del relajamiento de las cuerdas vocales, también es importante,
para una intubación rápida y segura, que no haya reacción al
tubo traqueal o tos después de su colocación. Ese trabajo tiene por
objetivo comparar las condiciones de intubación traqueal con rocuronio
(0,6 mg.kg-1) con escala clínica en niños, adultos
MÉTODO: Después de pre-medicación con midazolam, monitorización de rutina e inducción de la anestesia con propofol y fentanil, fueron evaluadas, por escala clínica, las condiciones de intubación traqueal después de 60 segundos, en 60 pacientes con edades entre 1 y 88 años, estado físico ASA I a III, que recibieron rocuronio (0,6 mg.kg-1) en 5 segundos. Los pacientes fueron divididos en tres grupos de acuerdo con la faja de edad: Grupo 1 (G1) niños de hasta 12 años, Grupo 2 (G2), adultos de 18 a 65 años y Grupo 3 (G3), pacientes mayores de 65 años. Fueron analizados los siguientes parámetros: las condiciones de intubación traqueal por escala clínica , y la presión arterial y el pulso, aferidos antes (control), después de la inducción, después de la inyección de rocuronio, 3 y 5 minutos después de la intubación traqueal.
RESULTADOS: Todos los pacientes fueron intubados con suceso en 60 segundos, más las condiciones clínicamente aceptables en 100% de los casos solo fueron obtenidas en los adultos y ancianos. Tres niños fueron clasificados con malas condiciones debido a la presencia de tos sustentada por más de 10 segundos. No hubo alteraciones significativas de la presión arterial ni de la frecuencia del pulso durante el estudio.
CONCLUSIONES: En las condiciones de ese estudio, la dosis de 0,6 mg.kg-1 fue suficiente para intubación traqueal en 60 segundos en adultos y ancianos. No obstante, fue insuficiente para obtención de condiciones de intubación traqueal clínicamente aceptables en 60 segundos en 100% de los niños.
Rocuronium (ORG 9426) is a steroid nondepolarizing neuromuscular blocker with 1/5 the potency of its analog vecuronium 1. Its major characteristic is faster onset as compared to all other commercially available relaxants 2, allowing tracheal intubation time similar to succinylcholine's 3-5.
There are several studies in the literature on rocuronium for fast tracheal intubation and, in general, they have shown that children, adults and elderly patients may be easily intubated in 60 seconds or less 4,6-9. However, it is difficult to compare tracheal intubation conditions with 0.6 mg.kg-1 rocuronium among different age brackets since studies involved different methods.
Our study aimed at comparing tracheal intubation conditions with rocuronium at 60 seconds in children, adults and elderly patients using the scale recommended for pharmacokinetic studies with neuromuscular blockers 10.
After the protocol approval by the Ethics Committees of Hospitals involved in the study and the informed consent of patients or tutors, participated in this study 60 patients aged 1 to 88 years submitted to elective surgeries under general anesthesia. Patients were divided in three groups according to age: Group 1 (G1) children up to 12 years of age; Group 2 (G2), adults aged 18 to 65 years; Group 3 (G3) patients above 65 years of age. Exclusion criteria were: pregnant or breastfeeding patients, neuromuscular, liver or renal diseases, patients under medication knowingly interfering with neuromuscular transmission and those with history suggesting hypersensitivity reactions to agents scheduled for the protocol.
Patients were premedicated with oral 7.5 to 15 mg midazolam (adults and elderly), or 0.5 to 1 mg.kg-1 for children (maximum 15 mg orally). At operating room patients were monitored with ECG at DII lead, pulse oximetry and noninvasive blood pressure. After oxygen under facial mask for 3 minutes, anesthesia was induced with fentanyl (3 to 5 µg.kg-1) and 3 to 4 mg.kg-1 (children) or 2 to 3 mg (adults and elderly) propofol. All patients received rocuronium in the fixed dose of 0.6 mg.kg-1 in 5 seconds and tracheal intubation was performed in 60 seconds after rocuronium injection.
The following parameters were evaluated: tracheal intubation conditions by clinical criteria 10 and blood pressure and pulse measured before induction (control), after induction, after rocuronium injection, 3 and 5 minutes after tracheal intubation.
Descriptive measures and multiple correspondence analysis were used for statistical analysis and MANOVA was used for circulatory parameters. Significance level was p < 0.05.
Demographics data and physical status (ASA) are shown in table I. There has been a predominance of males in G1 and of ASA II and III in G2 and G3, respectively.
Laryngoscopy conditions according to age are shown in table II. There have been excellent or good laryngoscopy conditions with vocal cords abducted or in intermediary position in all cases. The highest reaction rate was in item "cuff". Children have reacted more vigorously than adults and elderly, with limbs movement and even sustained cough.
Figure 1 shows results according to multiple correspondence analysis. It is observed that less satisfactory intubation conditions are associated to tracheal tube reaction with limbs movement and/or cough. As to age, children had less favorable tracheal intubation conditions.
Results have shown that all patients were intubated in 60 seconds with the conventional 0.6 mg.kg-1 rocuronium dose, but tracheal intubation conditions were better in adult and elderly patients.
Clinical criteria, and not neuromuscular transmission monitors, have been indicated to evaluate tracheal intubation since masseter and diaphragm relaxation and anesthetic depth are better determinants of tracheal intubation conditions than adductor policis muscle relaxation 11,12.
Tracheal intubation conditions depend on several factors, among them the induction agent, the use of opioids and neuromuscular blocker dose 13-15.
In experimental animals, induction agents do not interfere with rocuronium potency 16. In humans, although being mild with intravenous anesthetics 17, there have been better conditions when rocuronium was associated to propofol 9, which per se suppresses laryngeal muscles electromyographic effect 18. It is used for tracheal intubation even without neuromuscular blockers, although some authors do not indicate its single use for this objective 19,20. The simultaneous use of opioids, in addition to being associated to easier tracheal intubation, attenuates cardiovascular effects of laryngoscopy and tracheal intubation maneuvers 19.
The fact that all patients were successfully intubated in 60 seconds after 0.6 mg.kg-1 rocuronium confirms previous observations of safe relaxation in situations when airway has to be rapidly sealed 8,13,14. Major difference among groups was reaction to cuffs. Situations here defined as "clinically poor" in 3 pediatric patients suggest inadequate dose or time for diaphragm relaxation. Children with adequate mandible relaxation and open vocal cords, or with reactions, cough and diaphragmatic movements have already been observed by other authors 21, suggesting diaphragm relaxation time different than that observed for muscles implied in tracheal intubation.
The calculation of doses in mg.kg-1 for pediatric patients, although easy, may lead to prescription errors. It is not uncommon that subdoses are administered based on this calculation, varying minus 45% to minus 25% as compared to those calculated as from body surface. In order to correct this deviation, it has been suggested that in children with up to 30 kg, dose should be (weight x 2)% of adult doses, and that for children above 30 kg, this calculation should be (weight + 30)% of adult doses 22. In the three cases with sustained cough optimal doses then should have been approximately 14, 7.2 and 15 mg, instead of 10, 6 and 10 mg. So, although not being a consensus 23, it seems that the major advantage of doses above 2 times DE95 is early relaxation, which is even more evident in children 24.
A different explanation for poor conditions could have been insufficient time for relaxation. Hopkins et al. 25 have indicated that for 0.6 mg.kg-1 rocuronium, optimal time to obtain best conditions is approximately 70 seconds.
Differences in relaxation behavior in children and adults have already been identified 26, among them potency. It is higher in neonates and infants as compared to adults or older children 27.
Some cases were described in the literature of children with unexplained blockade installation delay with alcuronium 28. This seems to be related to decreased cardiac output, with consequent decrease in the balance rate of the relaxant between blood and muscle tissue 29. Invasive hemodynamic measurements were not used in this study, but studied children had no diseases followed by cardiac output decrease and, although not being able to state that this has not occurred, it seems unlikely that relaxation delay could have been caused by such clinical condition.
Fast tracheal intubation in all adults and elderly confirms data of pharmacodynamic studies that onset does not change with aging 30,31.
The lower incidence of tube reactions with diaphragm movements or cough in adult patients is in line with the literature, which has shown by electromyography similar relaxation installation rate in laryngeal muscles and diaphragm 32. Other authors, however, have emphasized that tracheal intubation conditions with 0.6 mg.kg-1 rocuronium are poorer than those obtained with 1 mg.kg-1 succinylcholine 33. So, there is a current trend to indicate 0.9 to 1.2 mg.kg-1 rocuronium when the aim is to replace succinylcholine 8,14,34-36.
Blood pressure and pulse changes, in general, had no clinical significance confirming previous circulatory stability observed with hypnotics and this neuromuscular blocker 35.
Rocuronium dose used in our study has allowed for tracheal intubation in 60 seconds in all patients. However, for a fast and safe induction, it is important that in addition to laryngeal muscles, diaphragm and intercostal muscles are also blocked to prevent tracheal tube or cuff reactions. So, our data suggest that 0.6 mg.kg-1 is insufficient to obtain clinically accepted conditions in children.
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Apresentado (Submitted) em 05 de
maio de 2003
Aceito (Accepted) para publicação em 05 de agosto de 2003
* Recebido do (Received from) do Hospital Universitário de Florianópolis e Hospital de Clínicas de Porto Alegre, RS