Anesth Analg 2002;95:233-237
© 2002 International Anesthesia Research Society
GENERAL ARTICLES
Fentanyl Attenuates the Hemodynamic Response to Endotracheal Intubation More Than the Response to Laryngoscopy
Yushi U. Adachi, MD*,
Maiko Satomoto, MD
,
Hideyuki Higuchi, MD, PhD
, and
Kazuhiko Watanabe, MD, PhD
*Medical Clinic of Kumagaya Base; Medical Corps of 1st Wings, Japan Air Self Defense Force; and Departments of Anesthesia, Self Defense Force Hanshin Hospital and National Defense Medical College, Saitama, Japan
Address correspondence and reprint requests to Yushi Adachi, Department of Anesthesiology, National Defense Medical College, 3-2 Namiki, Tokorozawa City, Saitama, Japan 359-8513. Address e-mail to grd1117{at}gr.ndmc.ac.jp
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Abstract
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We examined the effectiveness of avoiding laryngoscopy in reducing the hemodynamic responses to orotracheal intubation during the induction of anesthesia. One hundred surgical patients who required orotracheal intubation were randomly allocated into four groups. The first and third groups underwent fiberoptic intubation, in which an anesthesiologist inserted the endotracheal tube into the trachea under TV monitoring through a bronchoscope, and the second and fourth groups underwent conventional orotracheal intubation using a rigid laryngoscope. The third and fourth groups were pretreated with 2 µg/kg fentanyl IV immediately before the induction of anesthesia. Blood pressure and heart rate were measured noninvasively. A significant reduction in hemodynamic response was seen in only the group treated with fentanyl and intubated using the fiberoptic technique. Without fentanyl, there was no significant difference in hemodynamic changes between the groups. We conclude that the administration of fentanyl suppresses the hemodynamic responses to endotracheal intubation more than it does to laryngoscopy. There was no significant difference in the hemodynamic responses to orotracheal intubation by fiberscopy and laryngoscopy without fentanyl pretreatment, whereas 2 µg/kg fentanyl significantly reduced the hemodynamic responses in the group intubated by fiberscopy.
IMPLICATIONS: We assessed the effectiveness of avoiding laryngoscopy for orotracheal intubation. There was no significant difference in the hemodynamic responses to orotracheal intubation by fiberscopy and laryngoscopy without fentanyl pretreatment, whereas 2 µg/kg fentanyl significantly reduced the hemodynamic responses in the group intubated by fiberscopy. Pretreatment of fentanyl and fiberoptic intubation might be recommended for avoiding hyperdynamic responses.
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Introduction
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Many drugs and techniques have been used to prevent the hyperdynamic responses induced by laryngoscopy and endotracheal intubation (1–6). We studied the effectiveness of fiberoptic intubation without laryngoscopy and found no benefit in avoiding the use of laryngoscopy during the induction of anesthesia (7). Our results were consistent with those of Hirabayashi et al. (8); however, many other investigators have reported that avoiding the use of laryngoscopy for intubation was effective in preventing hemodynamic responses (2,4,9–12). Unlike our study, the patients in other studies were coadministered narcotics with induction drugs. Thus, we hypothesized that the narcotics used might have determined the advantage of avoiding the use of laryngoscopy. We investigated the effect of fentanyl on hemodynamic responses to orotracheal intubation with or without laryngoscopy.
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Materials and Methods
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After the study protocol was approved by the Division Ethics Committee of our institute, each of 100 patients gave informed consent to participate in this study. These patients were ASA physical status I or II, aged 19–70 yr, and scheduled for elective surgery with general anesthesia and orotracheal intubation; no difficulties with their airway or intubation were predicted during preoperative visits (Table 1). We excluded patients with any significant cardiovascular disease, including coronary artery disease or hypertension, and those who were receiving medications known to affect blood pressure and heart rate.
The patients were subsequently divided into four groups after a random-number sequence using a table. Patients in the first and third groups underwent orotracheal intubation using our method (7). For each patient in these groups, a bite block wound with gauze was inserted into the mouth to create space for inserting a fiberscope and an endotracheal tube; then, the anesthesiologist tilted up the patient’s jaw with the left hand, and slid an endotracheal tube into the middle of the retropharyngeal space through the mouth with the right hand. An assistant inserted a bronchoscope into the middle larynx through the bite block. Because the relationship between the endotracheal tube and the pharynx could be observed on a TV monitor through the bronchoscope (7), the anesthesiologist alone could insert the endotracheal tube into the trachea assisted by TV monitoring (7). The second and fourth groups of patients underwent conventional orotracheal intubation using a rigid Macintosh 3 laryngoscope.
Once the endotracheal tube was inserted, our planned investigation was completed, and general anesthesia for the subsequent surgical operation was maintained routinely.
Before the induction of anesthesia, all patients were premedicated with hydroxyzine (1 mg/kg, IM) and atropine sulfate (10 µg/kg, IM) 30 min before entering the operating room. Then, the electrocardiogram, noninvasive blood pressure, and arterial oxygen saturation by pulse oximetry were monitored, and propofol (250 µg · kg-1 · min-1, IV) was infused for 8 min. The third and fourth groups were administered 2 µg/kg fentanyl immediately before the propofol infusion, whereas the patients in the first and second groups were administrated saline as a placebo. After achieving hypnosis, determined as a loss of any response to verbal command, vecuronium (0.12 mg/kg) was given, and the propofol infusion was continued up to a total dose of 2 mg/kg. Procedures were then started according to the study protocol.
Noninvasive blood pressure, heart rate, and arterial oxygen saturation were recorded at the beginning of anesthesia induction and before and after orotracheal intubation every 2.5 min until 10 min from intubation. Immediately before intubation, a 3-mL blood sample was withdrawn from the femoral artery to determine the plasma propofol concentration (13).
The results were shown as means (SD). The age, weight, height, and cardiovascular variables, including blood pressure and heart rate, were statistically compared by analysis of variance among groups as appropriate. A probability of <5% was considered statistically significant, and significant differences were subsequently analyzed by using Newman-Keuls post hoc multiple comparisons tests.
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Results
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There were no significant differences among the four groups in the patients’ age, weight, height, or ASA physical status. Complete data sets were obtained from all 100 patients.
In each group, the blood pressure and heart rate decreased from baseline when general anesthesia was induced, and increased during orotracheal intubation (Table 2). After the induction of anesthesia, the blood pressure and heart rate decreased in the groups pretreated with fentanyl. There was no significant difference within the pairs of groups with or without fentanyl pretreatment, except the arterial blood pressure after intubation. A significant difference was found in arterial blood pressure changes after intubation between the groups intubated by fiberscopy and laryngoscopy with fentanyl pretreatment (124.0 [25.5] versus 146.8 [34.6] mm Hg in systolic pressure and 77.4 [17.8] versus 92.0 [19.8] mm Hg in diastolic pressure, P < 0.05). There were no significant differences in the changes in blood pressure or heart rate from before intubation to immediately after intubation (
P) between the Fiberscopy and Laryngoscopy Intubation groups without fentanyl pretreatment, whereas with fentanyl pretreatment, the P blood pressure was significantly smaller in the Fiberoptic Intubation group than in the Laryngoscopy group (P < 0.05, Fig. 1). At 5 min or more after intubation, no significant difference was observed between the groups with fentanyl pretreatment. The time required for intubation was significantly longer for the fiberoptic method compared with conventional intubation throughout the study (31 ± 15 versus 21 ± 10 s, P < 0.05). The plasma concentration of propofol did not differ among the groups. No patient in the study had an arterial oxygen saturation <95%.
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Figure 1. A comparison of the changes from before intubation to immediately after intubation (P) in systolic blood pressure, diastolic blood pressure, and heart rate in patients with or without pretreatment of fentanyl. All values are expressed as mean (SD). *P < 0.05 compared with other groups.
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Discussion
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We examined whether fiberoptic intubation attenuated hemodynamic responses to orotracheal intubation, compared with those that occurred with laryngoscopy, under two conditions: the patients either were or were not pretreated with fentanyl. The results of this investigation suggest that avoiding laryngoscopy had an effect on the hemodynamic responses to orotracheal intubation only when the ASA physical status I and II patients were pretreated with fentanyl.
Laryngoscopy itself is one of the most invasive stimuli during orotracheal intubation (1,14). Many anesthesiologists agree that a skilled anesthesiologist applies only a small force to the patient’s larynx when using a laryngoscope, and that reducing the force on the larynx might prevent excessive hyperdynamic responses to orotracheal intubation (3,14–17). The hemodynamic responses to orotracheal intubation have two components (14). The first is the response to laryngoscopy and the second is the response to endotracheal intubation. It is not known which component is more responsible for the reduction of the hyperdynamic response to orotracheal intubation with the administration of narcotics. Although we attempted to reduce the hyperdynamic responses to intubation by using fiber bronchoscopy without deep insertion in the trachea, there was no statistical significance in the cardiovascular variables between the Fiber-Bronchoscopy and Laryngoscopy groups (7), whereas other investigators demonstrated the effectiveness of avoiding laryngoscopy using new devices (9–12).
We focused on one of the differences in the methods used in those investigations; many patients who participated in other studies were administered narcotics immediately before intubation (9–12). Narcotic pretreatment attenuates the hemodynamic responses to orotracheal intubation (1,18–20). It is also possible that fentanyl administration affects the plasma concentrations of anesthetics during induction by changing circulatory variables (13,21). Thus, we applied the slow induction protocol for avoiding the determined plasma concentration of propofol and found no significant differences in the propofol concentration among the four groups. Therefore, the differences in the hemodynamic responses were likely derived from the effect of fentanyl.
The results of this investigation suggest that fentanyl suppresses the hemodynamic response to endotracheal intubation more than the response to laryngoscopy. It is also possible that the administration of narcotics might affect pharmacokinetics of anesthetics (22,23) during induction by changing the hemodynamics (13,21). The plasma concentration of propofol did not differ among the groups in the present investigation. Thus, the reason for the apparent effectiveness of avoiding laryngoscopy may be that fentanyl attenuates the sensitivity of the trachea to intubation. Our results are consistent with those of Kitamura et al. (9) and Nishikawa et al. (10,11). The stimulus produced by laryngoscopy might add to that of endotracheal intubation, but it is a relatively small stimulus compared with endotracheal intubation. In the investigation in which neither narcotics nor other treatments to reduce the stimulus of endotracheal intubation were used, avoiding laryngoscopy was ineffective in reducing the hemodynamic changes during the induction of anesthesia. Nishikawa et al. (10,11) demonstrated that using TrachelightTM was only effective in attenuating the response to orotracheal intubation in normotensive patients, and not hypertensive patients. These results support our hypothesis. In hypertensive patients, there may be an excessive hemodynamic response, as evaluated by circulatory variables, and the changes in blood pressure and heart rate with intubation might not differ between the two techniques.
Several limitations must be addressed concerning the design of this investigation. We studied 100 scheduled ASA physical status I and II surgical patients allocated into 4 groups, and the sample size might have been insufficient for exploring statistical significance, especially in the comparison of the groups without fentanyl pretreatment. However, we found no significant difference between groups consisting of 86 patients (7), which suggests that endotracheal intubation itself was the most invasive stimulus to laryngeal or pharyngeal tissues without fentanyl pretreatment. We focused on hemodynamic change only immediately after intubation. For details of the changes in hemodynamic variables, the influence of patient’s characteristics, and the effect of other drugs on the results, further investigations are required.
In summary, our results suggest that fentanyl suppresses the hemodynamic response to endotracheal intubation more than it suppresses the response to laryngoscopy. When an anesthesiologist attempts to reduce hemodynamic responses to orotracheal intubation by avoiding laryngoscopy, the coadministration of a small dose of fentanyl is recommended before the induction of anesthesia.
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Acknowledgments
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We express sincere thanks to Harue Kuge, Shizuko Kaneda, Kaai Mishima, Mikiko Ohbayashi, and Sachiyo Tamura for their assistance to this investigation in the operating room. We also thank Tetsuo Satoh, Professor of Anesthesiology, National Defense Medical College.
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Accepted for publication February 5, 2002.
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Abstract
Introduction
