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Revista Brasileira de Anestesiologia

Print version ISSN 0034-7094

Rev. Bras. Anestesiol. vol.51 no.4 Campinas  2001 



Evaluation of orbicularis oculi, adductor pollicis and flexor hallux muscles responses to train of four stimulation*


Avaliação das respostas dos músculos orbicular ocular, adutor do polegar e flexor do hálux à estimulação com a seqüência de quatro estímulos


Evaluación de las respuestas de los músculos orbicular ocular, aductor del pulgar y flexor del hálux a la estimulación con la secuencia de cuatro estímulos



Rogean Rodrigues Nunes, TSA, M.D.

Diretor Clínico e Chefe do Serviço de Anestesiologia do Hospital São Lucas de Cirurgia e Anestesia





BACKGROUND AND OBJECTIVES: Neuromuscular blockers (NMB) were a landmark in the practice of anesthesiology. However, one of the problems related to the use of NMBs is postoperative residual curarization. This study aimed at comparing responses of three different muscles to the train of four stimulation during induction and regression of rocuronium-induced neuromuscular blockade.
METHODS: Participated in this study 30 women physical status ASA I, aged 20 to 40 years submitted to general anesthesia. In the operating room patients were sedated with intravenous 10 alfentanil and supramaximal responses of orbicularis oculi, adductor pollicis and adductor hallucis were obtained. Anesthesia was then induced with intravenous propofol (3.5 and alfentanil (50 All patients received intravenous rocuronium (0.6 and sevoflurane for the maintenance of anesthesia. Train of four responses of different muscles were evaluated at every 14 seconds during installation and recovery T4/T1 of 0.25, 0.50, 0.75 and 0.90. Intubation was performed at the fastest relaxation moment of studied muscles and was evaluated by the proposed scale.
RESULTS: Mean onset of action for orbicularis oculi, adductor pollicis and adductor hallucis was 64.8, 131.3 and 196.1 seconds, respectively. Mean recovery time of T4/T1 0.9 was 59.1, 96.4 and 65.4, respectively. Tracheal intubation conditions were considered excellent in all cases.
CONCLUSIONS: Our results showed that satisfactory conditions for tracheal intubation can be achieved based the orbicularis oculi response to the train of four stimulation. However, during recovery, the highest safety margin was obtained with the adductor pollicis monitoring.

Key words: MEASUREMENT TECHNIQUES: acceleromyography; MONITORING: neuromuscular function; TRACHEAL INTUBATION; NEUROMUSCULAR BLOCKERS, Nondepolarizing: rocuronium


JUSTIFICATIVA E OBJETIVOS: O advento de drogas bloqueadoras neuromusculares foi um grande marco na Anestesiologia. Entretanto, um dos problemas do uso desses fármacos é a possibilidade de curarização residual no pós-operatório. O objetivo deste estudo foi avaliar as respostas de três músculos à estimulação com seqüência de quatro estímulos durante a instalação e a regressão do relaxamento muscular induzido pelo rocurônio.
MÉTODO: Participaram do estudo 30 pacientes do sexo feminino, com idades entre 20 e 40 anos, estado físico ASA I, submetidos à anestesia geral. Na sala de operação, todas receberam alfentanil 10 i.v. e, em seguida, foram determinadas as respostas supramaximais dos músculos orbicular ocular, adutor do polegar e flexor do hálux com acelerometria. A indução constou de propofol 3,5 i.v. e alfentanil 50 i.v. Todas receberam rocurônio 0,6 i.v. e sevoflurano para a manutenção da anestesia. Foram avaliadas as respostas musculares à estimulação com a seqüência de quatro estímulos a cada 14 segundos, durante instalação e na recuperação T4/T1 de 0,25, 0,50, 0,75 e 0,90. A intubação foi realizada no momento de relaxamento mais rápido nos músculos estudados e avaliada por escala proposta.
RESULTADOS: O início de ação nos músculos orbicular ocular, adutor do polegar e flexor do hálux foi respectivamente 64,8, 131,3 e 196,1 segundos (média). A recuperação até T4/T1 0,9 foi de 59,1, 96,4, 65,4 minutos (média) para os mesmos músculos respectivamente. As condições de intubação traqueal foram consideradas como clinicamente excelentes.
CONCLUSÕES: Os resultados mostram que se pode conseguir condições satisfatórias de intubação traqueal com início de ação baseado na resposta à neuroestimulação do músculo orbicular ocular. Entretanto, durante a recuperação do bloqueio, o que proporciona maior margem de segurança é a monitorização do músculo adutor do polegar.

Unitermos: BLOQUEADORES NEUROMUSCULARES, Não despolarizante: rocurônio; INTUBAÇÃO TRAQUEAL; MONITORIZAÇÃO: função neuromuscular; TÉCNICAS DE MEDIÇÃO: aceleromiografia


JUSTIFICATIVA Y OBJETIVOS: El adviento de drogas bloqueadoras neuromusculares fue un grande marco en la Anestesiologia. Entretanto, uno de los problemas del uso de eses fármacos es la posibilidad de curarización residual en el pós-operatório. El objetivo de este estudio fue evaluar las respuestas de tres músculos a la estimulación con secuencia de cuatro estímulos durante la instalación y la regresión del relajamiento muscular inducido por el rocuronio.
MÉTODO: Participaron del estudio 30 pacientes del sexo femenino, con edades entre 20 y 40 años, estado físico ASA I, sometidas a anestesia general. En la sala de operación todas recibieron alfentanil 10 i.v. y, en seguida fueron determinadas las respuestas supramaximales de los músculos orbicular ocular, aductor del pulgar y flexor del hálux con acelerometria. La inducción constó de propofol 3,5 i.v. y alfentanil 50 i.v. Todas recibieron rocuronio 0,6 i.v. y sevoflurano para la manutención de la anestesia. Fueron evaluadas las respuestas musculares a la estimulación con la secuencia de cuatro estímulos a cada 14 segundos, durante instalación y en la recuperación T4/T1 de 0,25, 0,50, 0,75 y 0,90. La intubación fue realizada en el momento de relajamiento más rápido en los músculos estudiados y evaluada por escala propuesta.
RESULTADOS: El inicio de acción en los músculos orbicular ocular, aductor del pulgar y flexor del hálux fue respectivamente 64,8, 131,3 y 196,1 segundos (media). La recuperación hasta T4/T1 0,9 fue de 59,1, 96,4, 65,4 minutos (media) para los mismos músculos respectivamente. Las condiciones de intubación traqueal fueron consideradas como clínicamente excelentes.
CONCLUSIONES: Los resultados muestran que se puede conseguir condiciones satisfactorias de intubación traqueal con inicio de acción teniendo como base la respuesta a la neuroestimulación del músculo orbicular ocular. Entretanto, durante la recuperación del bloqueo, lo que proporciona mayor margen de seguridad es la monitorización del músculo aductor del pulgar.




The advent of neuromuscular blockers (NMB) were a landmark in the practice of anesthesiology. However, one of the problems related to the use of NMBs is postoperative residual curarization. In addition, the right time for performing tracheal intubation with the best relaxation of laryngeal and pharyngeal muscles should be measured to make easier such maneuver. Harrison 1 has reported several respiratory failure cases due to inadequate recovery of neuromuscular blocks, and afterwards other authors have shown that 65 anesthesia-related deaths were due to postoperative respiratory complications 2. Neuromuscular transmission monitoring, in addition to suggesting the best tracheal intubation time, is the only safe method to evaluate NMBs residual action.

This study aimed at evaluating neuromuscular transmission through the Train of Four Stimulation (TOF) using acceleromyography 3,4 to monitor three different muscles: orbicularis oculi (facial nerve stimulation); adductor pollicis (ulnar nerve stimulation) and flexor hallux (posterior tibial nerve stimulation). Tracheal intubation performed at the fastest muscle relaxation time among studied muscles and their recovery profile with the use of rocuronium were evaluated.



After the Hospital’s Ethics Committee approval and their formal consent, participated in this study 30 female patients, aged 20 to 40 years, biomass index between 22 and 28, physical status ASA I, all of them Mallampati I and with normal extension of the head, submitted to elective surgeries under general anesthesia. Patients with neuromuscular, liver and renal diseases and those using drugs interfering with neuromuscular transmission were excluded from the study. No patient was premedicated.

Monitoring was performed in the operating room with cardio- scope in DII and V5, pulse oximetry, capnography, anesthetic gases analyzer, non invasive blood pressure, 95% spectral margin frequency (maintained between 8 and 12) and BIS (between 40 and 50). A venous puncture was obtained and maintained with lactated Ringer’s (500 ml) and intravenous alfentanil was injected (10 µ Then, supramaximal and baseline TOF responses of orbicularis oculi, adductor pollicis and flexor hallux were simultaneously obtained by applying stimulating electrodes on facial, ulnar and posterior tibial nerve paths (Figure 1, Figure 2 and Figure 3).

After a five-minute preoxygenation, intravenous propofol (3.5, alfentanil (50 µ and rocuronium (0.6 were injected in five seconds 5. At the same time, the three nerves were stimulated. Anesthesia was maintained with sevoflurane and expired concentration was adjusted to obtain a bispectral index (BIS) between 40 and 50. All patients were ventilated with a tidal volume of 8, through a ventilator with compliance loss compensation in a circular respiratory system with CO2 reabsorber and an I/E ratio of 1:2. Body temperature (naso-pharyngeal) was maintained between 36 and 37 ºC with the aid of a forced convective air thermal blanket.

Onset of action in all stimulated points was evaluated and this was considered the time elapsed between the beginning of rocuronium injection and 95% decrease in T1 (T1 = 5%) 5, as well as recovery time for T4/T1 in 0.25, 0.50, 0.75 and 0.90 for the three muscles. The value of T4/T1 from the last point to recover as compared to the one before last when it reached 0.9 was also evaluated. Laryngoscopy and tracheal intubation were performed when the first muscle showed T1 = 5%, based on the fastest decay point of neuromuscular transmission. Tracheal intubation conditions were analyzed through the scale shown in chart I.

Tracheal intubation conditions were evaluated as:

· Excellent: all qualifications excellent;

· Good: qualifications excellent or good;

· Poor: presence of one qualification listed as poor.

Laryngoscopies were evaluated as:

· Easy: relaxed mandible, lack of resistance to the laryngoscope blade;

· Regular: incomplete mandible relaxation, mild resistance to the laryngoscope blade;

· Difficult: insufficient mandible relaxation, patient’s active resistance to laryngoscopy.

Data were statistically analyzed by analysis of variance followed by Tukey’s test, considering significant p < 5%.



Table I shows demographic data. As to onset of action (T1 = 5%), there has been a statistically significant difference among the three evaluated muscles, as shown in table II, being T1 = 5% for the orbicularis oculi the fastest in all measurements (p < 0.05). Orbicularis oculi neuromuscular block recovery time was the shortest as compared to all times with a statistically significant difference as compared to the second shortest (thumb or toe). As to T4/T1 ratio, as from 0.50, flexor hallux had the fastest spontaneous recovery as compared to adductor pollicis (Table III and Figure 4). When flexor hallux showed a T1/T4 of 0.9, the value of this ratio for the adductor pollicis was 0.55 ± 0.03 (p < 0.001). All tracheal intubations were considered excellent.



Neuromuscular blockers are widely used in anesthesia and intensive care units for helping tracheal intubation, promoting a better surgical field relaxation and allowing for an adequate handling of patients under mechanical ventilation. However, they may promote major postoperative complications due to residual neuromuscular blockade 6,7.

For more than 20 years, the concept of a satisfactory neuromuscular block recovery when the patient had a T1/T4 around 0.70 has been considered adequate. However, it has been recently shown that a T1/T4 around such value does not represent a total recovery and may lead to ventilatory response depression to hypoxia 8-10. Viby-Mogensen et al. 11 have shown that 25% of patients with no monitoring of perioperative neuromuscular functions were admitted to the recovery room unable to keep their heads up for 5 seconds and 42% presented with a T4/T1 lower than 0.7. A recent study 12 evaluating and correlating T4/T1 with signs and symptoms in awaken patients has shown that there is no ability to maintain the head up for 5 seconds until such value reaches 0.60, and that when T4/T1 is lower than 0.9 there are clear signs of residual paralysis, such as diplopia and difficulty to follow moving objects. So, today it is accepted that there is a satisfactory neuromuscular function recovery when T4/T1 is equal to or higher than 0.90.

Our results have shown that it is possible to attain satisfactory tracheal intubation conditions based on the monitoring of the orbicularis oculi (mean - 64.8 seconds), since such conditions were already excellent when T1 = 5%, reflecting a better correlation with the diaphragmatic response. Studies 13,14 have shown that orbicularis oculi relaxation is established in a time similar to the relaxation of the larynx muscles; since monitoring larynx muscles is technically more difficult, orbicularis oculi is in general used as a guide for the best moment for tracheal intubation. Our clinical results confirm such experimental observations.

Our study has shown a muscle recovery consistently faster for the orbicularis oculi, which is in line with the literature 15.

Time for T4/T1 to reach 0.25 was similar for adductor pollicis and flexor hallux (around 45 minutes). Reports in the literature with the use of vecuronium are different and show an early recovery of the adductor pollicis 16.

With the evolution of spontaneous recovery, we observed that the adductor pollicis took longer for T4/T1 to reach 0.9. Such data are in line with other observations which have also shown a slower regression for the adductor pollicis.

Our conclusion is that tracheal intubation based on orbicularis oculi relaxation time has been successful and with satisfactory conditions for all patients, and that the adductor pollicis should be the muscle of choice to check muscle relaxation regression.



This study was made possible by the continuous support and encouragement of the President Director of Hospital São Lucas de Cirurgia e Anestesia, Dr. Salustiano Gomes de Pinho Pessoa.



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Mail to:
Dr. Rogean Rodrigues Nunes
Address: Av. Santos Dumont, 7797/1201 Bloco Dunas, Papicu
ZIP: 60190-800 City: Fortaleza, Brazil

Submitted for publication September 14, 2000
Accepted for publication February 1, 2001



* Received from Serviço de Anestesiologia do Hospital São Lucas de Cirurgia e Anestesia, Fortaleza, CE; Trabalho vencedor do Prêmio Heli Vieira, 2000

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