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Abstract |
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Endotracheal intubation has been performed during the administration of propofol anesthesia without neuromuscular blockade. In this study, we determined the propofol dose required for conventional nasotracheal or for fiberoptic nasotracheal intubation of all patients. Thirty-two patients undergoing maxillofacial surgery were randomly assigned to the conventional (n = 16) or to the fiberoptic (n = 16) intubation group. In both groups, anesthesia was induced by using IV fentanyl and IV titrated propofol according to clinical need (spontaneous respiration rate, verbal response). An endotracheal tube was placed nasally in the pharynx and the vocal cords visualized by using a fiberscope inserted via the tube. In the conventional group, the larynx was visualized additionally with a laryngoscope blade (Miller). In both groups propofol was titrated until the vocal cords opened. Patients were tracheally intubated, and the propofol dose was recorded. In all patients, the trachea could be intubated without the use of muscle relaxants. Considerable interindividual differences of dose requirements were observed. The amount of propofol required in the conventional group was significantly (P < 0.0001) larger (median ± SD: 2.74 ± 1.59 mg/kg; range 1.95–7.07 mg/kg) than in the fiberoptic group (1.37 ± 0.59 mg/kg; 0.72–2.86 mg/kg). Hemodynamics remained stable in all patients. Postintubational hoarseness occurred in three patients of each group. Fiberoptic nasal intubation without a muscle relaxant can be facilitated with significantly smaller and more predictable dosages of propofol than conventional nasal endotracheal intubation. The possibility of titrating the propofol dose under assisted ventilation until the vocal cords open during fiberoptic nasotracheal intubation and the better predictability of the required dose favors the fiberoptic approach.
Implications: In this study, contrary to all preceding studies using predefined doses of propofol and opioids, we determined the minimal required propofol dose in combination with fentanyl for conventional or fiberoptic nasotracheal intubation without muscle relaxants.
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Introduction |
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Induction of anesthesia is commonly facilitated by the administration of a combination of short-acting hypnotic drugs, opioids, and depolarizing or nondepolarizing muscle relaxants. The use of succinylcholine is controversial because of its complications (1). Because the use of nondepolarizing relaxants may also have undesirable effects (2), it may be preferable in some instances to provide good endotracheal intubating conditions without neuromuscular blockade. Surgeons often request nasotracheal intubation in maxillofacial patients. Airway pathology is common in these patients, and thus, nasotracheal intubation without muscle relaxation is preferable because spontaneous breathing can be maintained.
Successful tracheal intubation during propofol anesthesia without muscle relaxants has often been reported (2,4–9).1 In all of these studies, propofol was combined with opioids. Either alfentanil (2,4,6,7,9),1 remifentanil (8), or fentanyl (5) was used. Intubating conditions and the doses of opioids and propofol varied. Preset propofol dosage according to the various protocols ranged from 2 to 3.5 mg/kg (9). Conditions sufficient for tracheal intubation were reported in 20% to more than 90% of the patients.
In this study, we determined the required propofol dose in combination with fentanyl for conventional and fiberoptic nasotracheal intubation of all patients. Hemodynamic responses to anesthetic induction and endotracheal intubation, as well as postintubational complications, were recorded.
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Methods |
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After we received approval from our institutional review board and written, informed consent, 32 patients undergoing maxillofacial surgery were enrolled in this study. All patients were scheduled for nasotracheal intubation. All were ASA physical status I or II ranging in age from 19 to 72 yr. Exclusion criteria were: a history of IV drug use, alcohol addiction, gastroesophageal reflux, obesity > 30% above ideal body weight (10), any airway pathology, or a reactive airway disease. On arrival of the patients in the operating room, IV access was established, and both nostrils were anesthetized with lidocaine jelly. Approximately 5 mL/kg of lactated Ringer’s solution was administered before the induction of anesthesia. During this time, patients were asked to breathe oxygen via a face mask. Usual monitoring was established (electrocardiogram, mean arterial pressure [MAP], transcutaneous pulse oximeter, ETCO2), and baseline vital signs were recorded ("preinduction" values). The respiration rate was monitored continuously via impedance measurement together with the electrocardiogram.
Patients were randomly allocated to the conventional group or to the fiberoptic intubation group. Anesthesia was induced with a slow IV administration of 3 µg/kg fentanyl IV. If within the next 3 min, spontaneous respiration rate decreased to 10 breaths/min, the fentanyl dose was considered to be adequate; otherwise, an additional IV dose of fentanyl 1.5 µg/kg was administered. If necessary, spontaneous breathing was assisted manually. Vital signs recorded at this time were registered as "postfentanyl" values. Propofol was then titrated IV until loss of verbal response. Thereafter, an endotracheal tube, size 7.0–7.5, and a nasopharyngeal airway for oxygenation on the contralateral side were placed transnasally. The vocal cords were visualized by using a fiberscope inserted via the endotracheal tube. Propofol was then titrated until relaxation of the vocal cords. Until this moment, the endoscopist was blinded to the group assignment. In all the patients allocated to the fiberoptic group, the fiberscope was now passed through the larynx, and the endotracheal tube was placed into the trachea with a 90° counterclockwise rotation (11).
In the conventional group, a laryngoscope (Miller) was introduced after primary opening of the vocal cords and the larynx was visualized. If necessary, an additional dose of propofol was titrated until the vocal cords reopened. Patients were tracheally intubated, and the additional propofol doses recorded. In both groups, ventilation was assisted manually via the nasopharyngeal airway. The amount of propofol given, the degree of jaw relaxation (complete, moderate, none) at the time of intubation, as well as patient coughing (vigorous, slight, none) were recorded. After the propofol administration, and before endotracheal intubation, vital signs were registered as "postinduction" values. The vital signs after endotracheal placement of the tube were registered as "postintubation" values. Thereafter, anesthesia was maintained with a propofol drip (6 mg · kg-1 · h-1) and repeated doses of fentanyl given according to clinical need, avoiding the use of nitrous oxide. Patients were evaluated on the first postoperative day for incidence of hoarseness or sore throat.
Comparison of baseline values of heart rate (HR), MAP, necessary propofol dosages, and demographic data between the two groups was performed by using the Mann-Whitney-Wilcoxon-test. A value of P < 0.05 was considered to be statistically significant. Nonparametric analysis of variance (Friedman test) was performed for MAP and HR development followed by multiple comparison by using the Wilcoxon-Wilcox test if the Friedman test showed significance. Results were considered statistically significant at P < 0.05.
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Results |
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All 32 patients (median age 33 yr; range: 19–72 yr) could be tracheally intubated by using fentanyl and propofol without neuromuscular blockade. Patients were comparable with respect to their demographic data as well as the tube size (12) used for endotracheal intubation. Six (37.5%) patients in the fiberoptic and four (25%) patients in the conventional group required an additional dose of fentanyl. The mean dosage of fentanyl administered in the fiberoptic group was 3.56 µg/kg and in the conventional Group 3.47 µg/kg. None of the patients needed more than one additional dose of fentanyl. The propofol dosage required for achieving satisfactory opening of the vocal cords was significantly larger in the conventional group than in the fiberoptic group (Figure 1). In every patient of the conventional group, the opening of the vocal cords reversed after direct laryngoscopy. An additional propofol dose (0.63–3.62 mg/kg) was necessary to achieve a reopening of the vocal cords in these patients. When the tube was placed in the trachea, slight coughing occurred in the fiberoptic group in eight patients (50%) and in the conventional group in six patients (37.5%). In one patient (6.25%) in the fiberoptic group, vigorous coughing occurred, which was successfully treated by an additional bolus of 30 mg propofol.
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At the time of intubation (postinduction), jaw relaxation in the fiberoptic group was complete in seven (43.75%) and moderate in nine patients (56.25%). In the conventional group, jaw relaxation was judged moderate in one patient (6.25%) and complete in all of the others (93.75%). The incidence of hoarseness or sore throat on the first postoperative day was three patients (18,75%) in each group.
HR at postfentanyl and postinduction time was significantly slower than at baseline (preinduction) (Figure 2). MAP remained unchanged in both groups after fentanyl administration (postfentanyl) and decreased significantly after propofol was given (postinduction) without reaching critical values (MAP < 50 mm Hg; Figure 3).
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After intubation (postintubation), neither HR nor MAP exceeded preinduction values significantly either in the conventional group or in the fiberoptic group (Figures 2,3). During the study, transcutaneous pulse oximeter did not decrease to <94% in any patient. ETCO2 could not be measured during assisted ventilation via the nasopharyngeal airway, but postintubational values did not exceed 50 mm Hg in any patient.
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Discussion |
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TopAbstractIntroductionMethodsResultsDiscussionReferences |
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In this study, contrary to all previous studies using predefined doses of propofol, we determined the minimal required propofol dose in combination with fentanyl for conventional or fiberoptic nasotracheal intubation. Our data suggest, for the first time, that it is possible to intubate all patients without using muscle relaxants. In addition, hemodynamic responses to anesthetic induction and intubation, as well as postintubational complications, were recorded. HR decreased after the administration of fentanyl, but MAP did not. Propofol caused an additional decrease in MAP. In both groups, MAP and HR after intubation did not exceed the preinduction values. This hemodynamic response to fiberoptic and conventional intubation, using total IV anesthesia with fentanyl and propofol, has been described by Staender et al. (13). In both of our groups, the somatic response to intubation could be efficiently suppressed.
The incidence of postintubational sore throat or hoarseness (18.75%) was comparable to the results described by Stout et al. (12), who found an incidence of 18% in patients intubated by using small-sized tubes as in our study. The similar incidence of sore throat or hoarseness when intubation is performed without muscle relaxation suggests that this technique is not more traumatic than when intubating with muscle relaxants, even though postintubational coughing occurred in 37% to 56% of the patients.
Our results are similar to those of Scheller et al. (2), who, using a combination of alfentanil and propofol, found that jaw relaxation was at least moderate in all their patients. Thus, a combination of fentanyl and propofol for the induction of anesthesia provides acceptable jaw mobility even without the use of muscle relaxants, thereby avoiding the, albeit rare, side effects of muscle relaxants. An additional advantage, especially in maxillofacial patients, is the ability to maintain spontaneous breathing in case of intubation failure as a result of airway pathology.
Fiberoptic nasotracheal intubation required significantly smaller doses of propofol than conventional intubation. These findings are in contrast to those of Kazama et al. (14), who found that similar blood concentrations of propofol were required to suppress the somatic response to intubation with either a fiberscope or laryngoscope. Their findings may be the result of the oral fiberoptic intubation and the use of a MacIntosh laryngoscope. In contrast, we used the less stressful nasal route for the endotracheal tube after the administration of lidocaine jelly for local anesthesia of the nasopharyngeal mucosa (15) and the more invasive Miller laryngoscope (16). However, our results are consistent with those of Meiklejohn and Coley (17), who described significantly larger plasma concentrations of epinephrine and norepinephrine after laryngoscopy and intubation compared with a group undergoing blind nasal intubation.
Besides a significantly smaller dose of propofol necessary for fiberoptic intubation, the median interindividual range between minimal and maximal required dosage was smaller, 2.14 mg/kg, in comparison to the conventional group, in which the median interindividual propofol dose range was 5.12 mg/kg probably because of different forces necessary to obtain a clear view of the larynx. These findings are consistent with the study of Shribman et al. (18), who found a significant and similar increase of circulating catecholamine concentrations after laryngoscopy, with or without intubation. Therefore, the predictability of the propofol dose required for intubation without muscle relaxation and for sufficient depression of the hemodynamic response to intubation is much higher when using a fiberoptic, rather than a laryngoscopic, technique.
In conclusion, fiberoptic transnasal intubation without muscle relaxation is a valuable alternative to the conventional technique, with or without muscle relaxation, in the management of maxillofacial surgery patients. The value of the fiberoptic technique lies in its allowing the propofol dose to be titrated during assisted ventilation until the vocal cords open and better predictability of the dose required.
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Footnotes |
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1 Kallar S. Propofol allows intubation without relaxants [abstract]. Anesthesiology 1990;73:A22.
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References |
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TopAbstractIntroductionMethodsResultsDiscussionReferences |
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- Lerman J, Berdock SE, Bissonette B, et al. Succinylcholine warning [letter]. Can J Anaesth 1994;41:165.[Web of Science][Medline]
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Scheller MS, Zornow MH, Saidman LJ. Tracheal intubation without use of muscle relaxants: a technique using propofol and varying doses of alfentanil Anesth Analg 1992;75:788–93.
[Abstract/Free Full Text] - Kallar S. Propofol allows intubation without relaxants. Anesthesiology 1990;73:A22.
- Stevens JB, Vescovo MV, Harris KC, et al. Tracheal intubation using alfentanil and no muscle relaxant: is the choice of hypnotic important? Anesth Analg 1997;84:1222–6.[Abstract]
- Striebel HW, Hölzl M, Rieger A, Brummer G. Endotracheale intubation unter propofol und fentanyl. Anaesthesist 1995;44:809–17.[Web of Science][Medline]
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Davidson JA, Gillespie JA. Tracheal intubation after induction of anaesthesia with propofol, alfentanil and i.v. lignocaine. Br J Anaesth 1993;70:163–6.
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Coghlan SF, McDonald PF, Csepregi G. Use of alfentanil with propofol for nasotracheal intubation without neuromuscular block. Br J Anaesth 1993;70:89–91.
[Abstract/Free Full Text] - Stevens JB, Wheatley L. Tracheal intubation in ambulatory surgery patients: using remifentanil and propofol without muscle relaxants. Anesth Analg 1998;86:45–9.[Abstract]
- Hiller A, Klemola UM, Saarnivaara L. Tracheal intubation after induction of anaesthesia with propofol, alfentanil and lidocaine without neuromuscular blocking drugs in children. Acta Anaesthesiol Scand 1993;37:725–9.[Web of Science][Medline]
- Viby-Mogensen J, Engbaeck J, Eriksson LI. Good clinical research practice (GCRP) in pharmacodynamic studies of neuromuscular blocking agents. Acta Anaesthesiol Scand 1996;40:59–74.[Web of Science][Medline]
- Hughes S, Smith JE. Nasotracheal tube placement over the fibreoptic laryngoscope. Anaesthesia 1996;11:1026–8.
- Stout DM, Bishop MJ, Dwersteg JF, Cullen BF. Correlation of endotracheal tube size with sore throat and hoarseness following general anesthesia. Anesthesiology 1987;67:419–21.[Web of Science][Medline]
- Staender S, Marsch SCU, Schuhmacher P, Schaefer HG. Haemodynamic response to fibreoptic versus laryngoscopic nasotracheal intubation under total intravenous anaesthesia. Eur J Anaesthesiol 1994;11:175–9.[Web of Science][Medline]
- Kazama T, Ikeda K, Morita K, et al. Propofol concentration required for endotracheal intubation with laryngoscope or fibrescope and its interaction with fentanyl. Anesth Analg 1998;86:872–9.[Abstract]
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Sutherland AD, Williams RD. Cardiovascular responses and lidocaine absorption in fiberoptic assisted awake intubation. Anesth Analg 1986;65:389–91.
[Abstract/Free Full Text] - Nishiyama T, Higashizawa T, Bito H, et al. Which laryngoscope is the most stressful in laryngoscopy: MacIntosh, Miller, or McCoy? Masui 1997;46:1519–24.[Medline]
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Meiklejohn BH, Coley S. Pressor and catecholamine response to nasal intubation of the trachea. Br J Anaesth 1989;63:283–6.
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Shribman AJ, Smith G, Achola KJ. Cardiovascular and catecholamine responses to laryngoscopy with and without tracheal intubation. Br J Anaesth 1987;59:295–9.
[Abstract/Free Full Text]
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