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Hemodynamic and catecholamine response to tracheal intubation: direct laryngoscopy compared with fiberoptic intubation
Original Contributions Hemodynamic and Catecholamine Response to Tracheal Intubation: Direct Laryngoscopy Compared with Fiberoptic Intubation Michal Barak, MD,* Avishai Ziser, MD,† Avital Greenberg, MSc,‡ Sophie Lischinsky, MSc,‡ Beno Rosenberg, MD† Department of Anesthesiology, Rambam Medical Center, Haifa, Israel
*Staff Anesthesiologist, Rambam Medical Center, Haifa †Chairman of Department of Anesthesiology, Technion Faculty of Medicine, Haifa ‡Biochemist, Department of Clinical Biochemistry, Rambam Medical Center, Haifa Address correspondence to Dr. Barak at the Department of Anesthesiology, Rambam Medical Center, P.O. Box 9602, Haifa 31096, Israel. Received for publication August 27, 2002; revised manuscript accepted for publication September 4, 2002.
Study Objective: To compare the stress response following tracheal intubation using direct laryngoscopy to that using fiberoptic bronchoscopy technique. Design: Randomized, prospective study. Setting: Operating rooms in a teaching hospital. Patients: 51 ASA physical status I and II patients who were scheduled for an elective surgery with general anesthesia. Interventions: Patients were randomly assigned to receive either direct laryngoscopy or fiberoptic orotracheal intubation, as part of general anesthesia. A uniform protocol of anesthetic medications was used. Measurements: Blood pressure and heart rate were measured before induction, before endotracheal intubation, and 1, 2, 3, and 5 minutes afterwards. Catecholamine (epinephrine and norepinephrine) blood samples were drawn before the induction, and 1 and 5 minutes after intubation. Main Results : Duration of intubation was shorter in the direct laryngoscopy group (16.9 (16.9 ⫾ 7.0 sec, range 8 to 40) compared with the fiberoptic intubation group (55.0 ⫾ 22.5 sec, range 29 to 120), p ⬍ 0.0,001. In both groups, blood pressure and heart rate were significantly increased at 1, 2, and 3 minutes after intubation, but there was no significant difference between the two study groups. Catecholamine levels did not increase after intubation and did not correlate with the hemodynamic changes. Conclusions: The use of either direct laryngoscopy or fiberoptic bronchoscopy produces a comparable stress response to tracheal intubation. Catecholamine levels do not correlate with the hemodynamic changes. © 2003 by Elsevier Science Inc. Keywords: cardiovascular response; catecholamines; fiberoptic intubation; laryngoscopy.
Introduction The cardiovascular response to laryngoscopy and tracheal intubation has been extensively studied during the past three decades. Tracheal intubation causes a
Journal of Clinical Anesthesia 15:132–136, 2003 © 2003 Elsevier Science Inc. All rights reserved. 655 Avenue of the Americas, New York, NY 10010
0952-8180/03/$–see front matter doi:10.1016/S0952-8180(03)00514-7
Hemodynamic response to tracheal intubation: Barak et al.
Table 1. Patient Characteristics
Group
n
Age (yrs)
Weight (kg)
Gender (M:F)
Direct laryngoscopy Fiberoptic intubation
26 25
36.1 ⫾ 10.6 35.5 ⫾ 14.7
72.4 ⫾ 15.1 71.6 ⫾ 14.3
8:18 2:23
reflex increase in sympathetic activity that may result in hypertension, tachycardia, and arrhythmia.1–3 A change in plasma catecholamine concentrations also has been demonstrated to be a part of the stress response to tracheal intubation4,5. The extent of the reaction is affected by many factors: the technique of laryngoscopy6 – 8 and intubation,9 –11 and the use of various airway instruments, like flexible fiberoptic bronchoscope and the Laryngeal Mask Airway (LMA North America, Inc., San Diego, CA).12,13 Premedication and induction drugs may attenuate the circulatory response,14 –16 and different pharmacologic combinations were tested for that purpose.17,18 A patient’s medical condition affects his physiologic response,19,20 and even ethnic variations have been implicated.21 The cardiovascular response to tracheal intubation, although transient, may be harmful to some patients, mainly those with myocardial or cerebrovascular disease. In this study, cardiovascular parameters and plasma catecholamine levels were used to compare the stress response to direct laryngoscopy to that after fiberopticfacilitated oral intubation.
Materials and Methods The Ethics Committee of Rambam Medical Center Institution approved the study, and written informed consent was obtained from all the patients. Fifty-three adult ASA I and II patients who were scheduled for elective surgery requiring general anesthesia, tracheal intubation, and mechanical ventilation, were studied prospectively. We excluded patients with known cardiovascular disease, diabetes, those taking any medication on a scheduled basis, and whenever a difficult intubation was anticipated. Patients were randomly assigned into two groups: direct laryngoscopy group (DLG) and fiberoptic intubation group (FOBG). Male and female patients were intubated with 8.5- and 8.0-mm ID endotracheal tubes, respectively. All intubations were performed by the same anesthesiologist. All patients were premedicated 1 hour before surgery with oral diazepam and metoclopramide 10 mg each. On arrival at the operating room, two intravenous (IV) catheters were placed under local anesthesia, one in each arm. One IV catheter was for fluid and drug administration and the other for drawing blood samples. Continuous monitoring included electrocardiogram, pulse oximetry, and capnography. Blood pressure (BP) was measured at 1-minute intervals using a noninvasive BP monitor (Datex AS3; Datex-Ohmeda, Milwaukee, WI). Preinduction medications included midazolam 0.03 mg/kg and fentanyl 0.001 mg/kg given 5 minutes before
endotracheal intubation. Anesthesia was induced with 4 to 5 mg/kg thiopental sodium, followed by vecuronium 0.1 mg/kg. Patients were ventilated with 100% oxygen by facemask until the neuromuscular block was complete. A Guedel oropharyngeal airway was used if it seemed necessary by the anesthesia provider. Tracheal intubation was facilitated by direct laryngoscopy and was carried out with a standard Macintosh laryngoscope blade. Fiberoptic intubation was accomplished with a 5-mm flexible fiberoptic bronchoscope (Pentax FB-15P; Pentax, Lake Success, NY). The fiberoptic bronchoscope (FOB), on which was mounted the tracheal tube, was passed into the trachea, through a William’s oropharyngeal airway, until the carina was visualized. Than the tracheal tube was carefully advanced into the trachea and the FOB was withdrawn. The time between introduction of the laryngoscope or FOB until the endotracheal tube was in place and an end-tidal carbon dioxide (ETCO2) waveform was seen on the monitor, was recorded. After tracheal intubation was accomplished, patients from both groups were ventilated with a 50% mixture of nitrous oxide in oxygen and isoflurane 0.6%. Heart rate (HR), BP, and oxygen saturation (SpO2) were recorded before the induction, 1 minute before intubation, and then 1, 2, 3, and 5 minutes after intubation. Plasma catecholamine levels were drawn before the induction of anesthesia, and then 1 and 5 minutes after intubation.
Catecholamine Measurement Blood samples for epinephrine (E) and norepinephrine (NE) were collected into ethylenediaminetetraacetic acid (EDTA) tubes. Plasma catecholamines were determined by high-performance liquid chromatography (HPLC) with electrochemical detection, using methods that were previously described.22 The reference blood levels were up to 0.45 nmol · L–1 for E and up to 2.40 nmol · L–1 for NE.
Statistical Analysis Data are expressed as means ⫾ standard deviation (SD). Statistical analysis consisted of multivariate analysis of variance (MANOVA) of differences among the groups at specific times. Repeated measures MANOVA test was used to evaluate changes in HR, BP and catecholamine blood levels compared with preintubation values for each intubation technique. A p-value less than 0.05 was considered statistically significant. J. Clin. Anesth., vol. 15, March 2003
133
Original Contributions
Table 2. Changes in Systolic (SBP) and Diastolic (DBP) Blood Pressures, and Heart Rate (HR), in the Direct Laryngoscopy and Fiberoptic Intubation Groups Before Induction
Group
Direct laryngoscopy n ⫽ 26 SBP (mmHg) 132 ⫾ 17 DBP 80 ⫾ 10 (mmHg) HR (bpm) 74 ⫾ 13 Fiberoptic intubation n ⫽ 25 SBP (mmHg) 134 ⫾ 18 DBP 81 ⫾ 9 (mmHg) HR (bpm) 77 ⫾ 11
Minutes after intubation
Before Intubation
1
2
3
110 ⫾ 9* 67 ⫾ 7*
140 ⫾ 23† 92 ⫾ 15†
126 ⫾ 16† 80 ⫾ 10†
119 ⫾ 12† 73 ⫾ 11†
75 ⫾ 10
92 ⫾ 13†
88 ⫾ 12†
85 ⫾ 11†
81 ⫾ 12
115 ⫾ 14* 73 ⫾ 13*
139 ⫾ 22† 90 ⫾ 14†
131 ⫾ 23† 85 ⫾ 17†
121 ⫾ 17† 80 ⫾ 13†
114 ⫾ 13 72 ⫾ 10
82 ⫾ 15
95 ⫾ 13†
90 ⫾ 14†
89 ⫾ 14†
84 ⫾ 13
5 109 ⫾ 9 67 ⫾ 8
*p ⬍ 0.05, compared with values before the induction. †p ⬍ 0.05, compared with values before intubation.
Results A total of 53 patients were enrolled in the study. Two patients were excluded, one because of premature ventricular contractions during intubation and the other because of a difficult intubation that was not anticipated. There were 26 patients in the DLG and 25 in the FOBG groups. The two groups were matched in age, weight, and gender (Table 1). The mean length of time for successful endotracheal intubation was shorter in the DLG group compared with the FOBG group, 16.9 ⫾ 7.0 (range 8 to 40) versus 55.0 ⫾ 22.5 (range 29 to 120) seconds, respectively (p ⬍ 0.001). Oxygen saturation was maintained above 95% at all times in all patients. Changes in hemodynamic parameters: systolic, diastolic arterial blood pressure, and HR are listed in Table 2. A significant reduction in HR and BP was evident after the induction of general anesthesia in both groups. One minute following tracheal intubation, there was an increase in those parameters. A gradual decline was inspected between 2 and 5 minutes post intubation. Analysis of variance showed no significant difference at each time point between the two groups.
Figure 1. Epinephrine concentrations (nmol · L–1), mean ⫾ SD. Group 1 ⫽ direct laryngoscopy, Group 2 ⫽ fiberoptic intubation. 134
J. Clin. Anesth., vol. 15, March 2003
Catecholamine plasma levels are shown in Figures 1 and 2. Preinduction catecholamine concentrations decreased significantly after the induction of anesthesia. There was no significant difference in epinephrine levels between the groups, in matched time points. Plasma norepinephrine level before the induction was significantly higher in the FOBG group, but no significant difference was found between the groups after intubation.
Discussion During the induction of general anesthesia, laryngoscopy and tracheal intubation are frequently performed. While securing the patient airway, hemodynamic changes may occur. The anesthesiologist, trying to make the induction as smooth as possible, learned to appreciate the importance of that sequence of events. Some patients more than others may experience substantial hemodynamic changes during the induction and intubation phase. Therefore, meticulous preparation before endotracheal intubation is warranted. Our study demonstrated that orotracheal intubation, facilitated by FOB, required more time, compared with direct laryngoscopy orotracheal intubation. This was previously reported, both during the learning curve and also in experienced hands.1,2 However, the increased duration of the fiberoptic procedure did not affect the hemodynamic response or catecholamine levels, as compared with the direct laryngoscopy method. It brings us to the question, what is the most important factor that cause the stress response during intubation? Researchers have tried to separate the effect of laryngoscopy from that of tracheal intubation. The effect of intubation alone was studied by Shribman et al.23 who compared the cardiovascular response to direct laryngoscopy, with and without tracheal intubation. They found no difference between the two, and concluded that the laryngoscopy itself is the major contributor to the stress response. Adachi et al.24 studied the cardiovascular response to a fiberoptic-guided
Hemodynamic response to tracheal intubation: Barak et al.
Figure 2. Norepinephrine concentrations (nmol · L–1), mean ⫾ SD. Group 1 ⫽ direct laryngoscopy, Group 2 ⫽ fiberoptic intubation. *p ⬍ 0.05 compared with Group 1.
intubation with television monitoring. They hypothesized that since that technique is minimally invasive, it causes a relatively low cardiovascular response. Their results failed to demonstrate the superiority of that method over classical laryngoscopy, and they concluded that endotracheal intubation itself is the major stimulus to cardiovascular response. In that study,24 however, the FOB remained in the pharynx and did not cross the vocal cords. In addition, catecholamine levels were not measured. Our results show similar hemodynamic response and catecholamine levels to both intubation techniques. We therefore cannot conclude whether the airway instrumentation or orotracheal intubation was the main cause for the hemodynamic changes. In our study, we examined catecholamine blood levels and attempted to determine whether they correlated with cardiovascular parameters. Plasma catecholamine levels did not increase after the induction of general anesthesia in either group. One minute following tracheal intubation, HR and BP increased whereas catecholamine levels decreased. Similar results were previously reported in studies that failed to demonstrate an increase in epinephrine level following intubation.5,6 In these reports, the norepinephrine level was only mildly elevated after intubation, and only in one of the two intubation techniques that were evaluated.5,6 Although a correlation between BP and HR and catecholamine might be expected, only one study has demonstrated this.4 Therefore, this concept may deserve further evaluation. In conclusion, we found that the stress response to fiberoptic orotracheal intubation is similar to orotracheal intubation facilitated by the Macintosh laryngoscopy blade. No significant differences in hemodynamic parameters, or in catecholamine blood levels were found between the groups. Fiberoptic intubation is an important adjunct in airway management. Because it creates a similar stress response to regular laryngoscopy intubation, it should be safely applied whenever indicated.
References 1. Smith JE: HR and arterial pressure changes during fiberoptic tracheal intubation under general anaesthesia. Anaesthesia 1988; 43:629 –32. 2. Finfer SR, MacKenzie SI, Saddler JM, Watkins TJ: Cardiovascular responses to tracheal intubation: a comparison of direct laryngoscopy and fibreoptic intubation. Anaesth Intensive Care 1989;17: 44 –8. 3. Smith JE, Mackenzie AA, Sanghera SS, Scott-Knight VC: Cardiovascular effects of fibrescope-guided nasotracheal intubation. Anaesthesia 1989;44:907–10. 4. Fujii Y, Tanaka H, Toyooka H: Circulatory responses to laryngeal mask airway insertion or tracheal intubation in normotensive and hypertensive patients. Can J Anaesth 1995;42:32–6. 5. Pernerstorfer T, Krafft P, Fitzgerald RD, et al: Stress response to tracheal intubation: direct laryngoscopy compared with blind oral intubation. Anaesthesia 1995;50:17–22. 6. McCoy EP, Mirakhur RK, McCloskey BV: A comparison of the stress response to laryngoscopy. The Macintosh versus the McCoy blade. Anaesthesia 1995;50:943–6. 7. Ovassapian A, Yelich SJ, Dykes MH, Brunner EE: BP and HR changes during awake fiberoptic nasotracheal intubation. Anesth Analg 1983;62:951–4. 8. Smith M, Calder I, Crockard A, Isert P, Nicol ME: Oxygen saturation and cardiovascular changes during fibreoptic intubation under general anaesthesia. Anaesthesia 1992;47:158 –61. 9. Schaefer HG, Marsch SC: Comparison of orthodox with fibreoptic orotracheal intubation under total I. V. anaesthesia. Br J Anaesth 1991;66:608 –10. 10. Smith JE, Mackenzie AA, Scott-Knight VC: Comparison of two methods of fibrescope-guided tracheal intubation. Br J Anaesth 1991;66:546 –50. 11. Schaefer HG, Marsch SC, Keller HL, Strebel S, Anselmi L, Drewe J: Teaching fibreoptic intubation in anaesthetised patients. Anaesthesia 1994;49:331–4. 12. Imai M, Matsumura C, Hanaoka Y, Kemmotsu O: Comparison of cardiovascular responses to airway management: fiberoptic intubation using a new adapter, laryngeal mask insertion, or conventional laryngoscopic intubation. J Clin Anesth 1995;7:14 –8. 13. Dyer RA, Llewellyn RL, James MF: Total i. v. anaesthesia with propofol and laryngeal mask for orthopaedic surgery. Br J Anaesth 1995;74:123–8. 14. Schaefer HG, Marsch SC, Strebel SP, Drewe J: Cardiovascular J. Clin. Anesth., vol. 15, March 2003
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effects of fibreoptic oral intubation. A comparison of a total intravenous and a balanced volatile technique. Anaesthesia 1992; 47:1034 –6. Mustola ST, Baer GA, Metsa-Ketela T, Laippala P: Haemodynamic and plasma catecholamine responses during total intravenous anaesthesia for laryngomicroscopy. Thiopentone compared with propofol. Anaesthesia 1995;50:108 –13. Brossy MJ, James MF, Janicki PK: Haemodynamic and catecholamine changes after induction of anaesthesia with either thiopentone or propofol with suxamethonium. Br J Anaesth 1994;72: 596 –8. Mikawa K, Nishina K, Maekawa N, Obara H: Comparison of nicardipine, diltiazem and verapamil for controlling the cardiovascular responses to tracheal intubation. Br J Anaesth 1996;76: 221–6. Mikawa K, Maekawa N, Hasegawa M, et al: Attenuation of the cardiovascular and catecholamine responses to tracheal intubation with oral guanabenz. Anesth Analg 1993;76:585–91. Kirvela M, Scheinin M, Lindgren L: Haemodynamic and catecholamine responses to induction of anaesthesia and tracheal intubation in diabetic and non-diabetic uraemic patients. Br J
J. Clin. Anesth., vol. 15, March 2003
Anaesth 1995;74:60 –5. 20. Neidhart PP, Champion P, Vogel J, Zsigmond EK, Tassonyi E: A comparison of pipecuronium with pancuronium on haemodynamic variables and plasma catecholamines in coronary artery bypass patients. Can J Anaesth 1994;41:469 –74. 21. Houghton IT, Low JM, Lau JTF, Oh TE: An ethnic comparison of the sympathetic response to tracheal intubation. Anaesthesia 1993;48:965–8. 22. Goldstein DS, Feuerstein G, Izzo JL, Jr, Kopin IJ, Keiser HR: Validity and reliability of liquid chromatography with electrochemical detection of measuring plasma levels of norepinephrine and epinephrine in man. Life Sci 1981;28:467–75. 23. Shribman AJ, Smith G, Achola KJ: Cardiovascular and catecholamine responses to laryngoscopy with and without tracheal intubation. Br J Aneasth 1987;59:295–9. 24. Adachi YU, Takamatsu I, Watanabe K, Uchihushi Y, Higuchi H, Satoh T: Evaluation of the cardiovascular responses to fiberoptic orotracheal intubation with television monitoring: comparison with conventional direct laryngoscopy. J Clin Anesth 2000;12: 503–8.
*Staff Anesthesiologist, Rambam Medical Center, Haifa †Chairman of Department of Anesthesiology, Technion Faculty of Medicine, Haifa ‡Biochemist, Department of Clinical Biochemistry, Rambam Medical Center, Haifa Address correspondence to Dr. Barak at the Department of Anesthesiology, Rambam Medical Center, P.O. Box 9602, Haifa 31096, Israel. Received for publication August 27, 2002; revised manuscript accepted for publication September 4, 2002.
Study Objective: To compare the stress response following tracheal intubation using direct laryngoscopy to that using fiberoptic bronchoscopy technique. Design: Randomized, prospective study. Setting: Operating rooms in a teaching hospital. Patients: 51 ASA physical status I and II patients who were scheduled for an elective surgery with general anesthesia. Interventions: Patients were randomly assigned to receive either direct laryngoscopy or fiberoptic orotracheal intubation, as part of general anesthesia. A uniform protocol of anesthetic medications was used. Measurements: Blood pressure and heart rate were measured before induction, before endotracheal intubation, and 1, 2, 3, and 5 minutes afterwards. Catecholamine (epinephrine and norepinephrine) blood samples were drawn before the induction, and 1 and 5 minutes after intubation. Main Results : Duration of intubation was shorter in the direct laryngoscopy group (16.9 (16.9 ⫾ 7.0 sec, range 8 to 40) compared with the fiberoptic intubation group (55.0 ⫾ 22.5 sec, range 29 to 120), p ⬍ 0.0,001. In both groups, blood pressure and heart rate were significantly increased at 1, 2, and 3 minutes after intubation, but there was no significant difference between the two study groups. Catecholamine levels did not increase after intubation and did not correlate with the hemodynamic changes. Conclusions: The use of either direct laryngoscopy or fiberoptic bronchoscopy produces a comparable stress response to tracheal intubation. Catecholamine levels do not correlate with the hemodynamic changes. © 2003 by Elsevier Science Inc. Keywords: cardiovascular response; catecholamines; fiberoptic intubation; laryngoscopy.
Introduction The cardiovascular response to laryngoscopy and tracheal intubation has been extensively studied during the past three decades. Tracheal intubation causes a
Journal of Clinical Anesthesia 15:132–136, 2003 © 2003 Elsevier Science Inc. All rights reserved. 655 Avenue of the Americas, New York, NY 10010
0952-8180/03/$–see front matter doi:10.1016/S0952-8180(03)00514-7
Hemodynamic response to tracheal intubation: Barak et al.
Table 1. Patient Characteristics
Group
n
Age (yrs)
Weight (kg)
Gender (M:F)
Direct laryngoscopy Fiberoptic intubation
26 25
36.1 ⫾ 10.6 35.5 ⫾ 14.7
72.4 ⫾ 15.1 71.6 ⫾ 14.3
8:18 2:23
reflex increase in sympathetic activity that may result in hypertension, tachycardia, and arrhythmia.1–3 A change in plasma catecholamine concentrations also has been demonstrated to be a part of the stress response to tracheal intubation4,5. The extent of the reaction is affected by many factors: the technique of laryngoscopy6 – 8 and intubation,9 –11 and the use of various airway instruments, like flexible fiberoptic bronchoscope and the Laryngeal Mask Airway (LMA North America, Inc., San Diego, CA).12,13 Premedication and induction drugs may attenuate the circulatory response,14 –16 and different pharmacologic combinations were tested for that purpose.17,18 A patient’s medical condition affects his physiologic response,19,20 and even ethnic variations have been implicated.21 The cardiovascular response to tracheal intubation, although transient, may be harmful to some patients, mainly those with myocardial or cerebrovascular disease. In this study, cardiovascular parameters and plasma catecholamine levels were used to compare the stress response to direct laryngoscopy to that after fiberopticfacilitated oral intubation.
Materials and Methods The Ethics Committee of Rambam Medical Center Institution approved the study, and written informed consent was obtained from all the patients. Fifty-three adult ASA I and II patients who were scheduled for elective surgery requiring general anesthesia, tracheal intubation, and mechanical ventilation, were studied prospectively. We excluded patients with known cardiovascular disease, diabetes, those taking any medication on a scheduled basis, and whenever a difficult intubation was anticipated. Patients were randomly assigned into two groups: direct laryngoscopy group (DLG) and fiberoptic intubation group (FOBG). Male and female patients were intubated with 8.5- and 8.0-mm ID endotracheal tubes, respectively. All intubations were performed by the same anesthesiologist. All patients were premedicated 1 hour before surgery with oral diazepam and metoclopramide 10 mg each. On arrival at the operating room, two intravenous (IV) catheters were placed under local anesthesia, one in each arm. One IV catheter was for fluid and drug administration and the other for drawing blood samples. Continuous monitoring included electrocardiogram, pulse oximetry, and capnography. Blood pressure (BP) was measured at 1-minute intervals using a noninvasive BP monitor (Datex AS3; Datex-Ohmeda, Milwaukee, WI). Preinduction medications included midazolam 0.03 mg/kg and fentanyl 0.001 mg/kg given 5 minutes before
endotracheal intubation. Anesthesia was induced with 4 to 5 mg/kg thiopental sodium, followed by vecuronium 0.1 mg/kg. Patients were ventilated with 100% oxygen by facemask until the neuromuscular block was complete. A Guedel oropharyngeal airway was used if it seemed necessary by the anesthesia provider. Tracheal intubation was facilitated by direct laryngoscopy and was carried out with a standard Macintosh laryngoscope blade. Fiberoptic intubation was accomplished with a 5-mm flexible fiberoptic bronchoscope (Pentax FB-15P; Pentax, Lake Success, NY). The fiberoptic bronchoscope (FOB), on which was mounted the tracheal tube, was passed into the trachea, through a William’s oropharyngeal airway, until the carina was visualized. Than the tracheal tube was carefully advanced into the trachea and the FOB was withdrawn. The time between introduction of the laryngoscope or FOB until the endotracheal tube was in place and an end-tidal carbon dioxide (ETCO2) waveform was seen on the monitor, was recorded. After tracheal intubation was accomplished, patients from both groups were ventilated with a 50% mixture of nitrous oxide in oxygen and isoflurane 0.6%. Heart rate (HR), BP, and oxygen saturation (SpO2) were recorded before the induction, 1 minute before intubation, and then 1, 2, 3, and 5 minutes after intubation. Plasma catecholamine levels were drawn before the induction of anesthesia, and then 1 and 5 minutes after intubation.
Catecholamine Measurement Blood samples for epinephrine (E) and norepinephrine (NE) were collected into ethylenediaminetetraacetic acid (EDTA) tubes. Plasma catecholamines were determined by high-performance liquid chromatography (HPLC) with electrochemical detection, using methods that were previously described.22 The reference blood levels were up to 0.45 nmol · L–1 for E and up to 2.40 nmol · L–1 for NE.
Statistical Analysis Data are expressed as means ⫾ standard deviation (SD). Statistical analysis consisted of multivariate analysis of variance (MANOVA) of differences among the groups at specific times. Repeated measures MANOVA test was used to evaluate changes in HR, BP and catecholamine blood levels compared with preintubation values for each intubation technique. A p-value less than 0.05 was considered statistically significant. J. Clin. Anesth., vol. 15, March 2003
133
Original Contributions
Table 2. Changes in Systolic (SBP) and Diastolic (DBP) Blood Pressures, and Heart Rate (HR), in the Direct Laryngoscopy and Fiberoptic Intubation Groups Before Induction
Group
Direct laryngoscopy n ⫽ 26 SBP (mmHg) 132 ⫾ 17 DBP 80 ⫾ 10 (mmHg) HR (bpm) 74 ⫾ 13 Fiberoptic intubation n ⫽ 25 SBP (mmHg) 134 ⫾ 18 DBP 81 ⫾ 9 (mmHg) HR (bpm) 77 ⫾ 11
Minutes after intubation
Before Intubation
1
2
3
110 ⫾ 9* 67 ⫾ 7*
140 ⫾ 23† 92 ⫾ 15†
126 ⫾ 16† 80 ⫾ 10†
119 ⫾ 12† 73 ⫾ 11†
75 ⫾ 10
92 ⫾ 13†
88 ⫾ 12†
85 ⫾ 11†
81 ⫾ 12
115 ⫾ 14* 73 ⫾ 13*
139 ⫾ 22† 90 ⫾ 14†
131 ⫾ 23† 85 ⫾ 17†
121 ⫾ 17† 80 ⫾ 13†
114 ⫾ 13 72 ⫾ 10
82 ⫾ 15
95 ⫾ 13†
90 ⫾ 14†
89 ⫾ 14†
84 ⫾ 13
5 109 ⫾ 9 67 ⫾ 8
*p ⬍ 0.05, compared with values before the induction. †p ⬍ 0.05, compared with values before intubation.
Results A total of 53 patients were enrolled in the study. Two patients were excluded, one because of premature ventricular contractions during intubation and the other because of a difficult intubation that was not anticipated. There were 26 patients in the DLG and 25 in the FOBG groups. The two groups were matched in age, weight, and gender (Table 1). The mean length of time for successful endotracheal intubation was shorter in the DLG group compared with the FOBG group, 16.9 ⫾ 7.0 (range 8 to 40) versus 55.0 ⫾ 22.5 (range 29 to 120) seconds, respectively (p ⬍ 0.001). Oxygen saturation was maintained above 95% at all times in all patients. Changes in hemodynamic parameters: systolic, diastolic arterial blood pressure, and HR are listed in Table 2. A significant reduction in HR and BP was evident after the induction of general anesthesia in both groups. One minute following tracheal intubation, there was an increase in those parameters. A gradual decline was inspected between 2 and 5 minutes post intubation. Analysis of variance showed no significant difference at each time point between the two groups.
Figure 1. Epinephrine concentrations (nmol · L–1), mean ⫾ SD. Group 1 ⫽ direct laryngoscopy, Group 2 ⫽ fiberoptic intubation. 134
J. Clin. Anesth., vol. 15, March 2003
Catecholamine plasma levels are shown in Figures 1 and 2. Preinduction catecholamine concentrations decreased significantly after the induction of anesthesia. There was no significant difference in epinephrine levels between the groups, in matched time points. Plasma norepinephrine level before the induction was significantly higher in the FOBG group, but no significant difference was found between the groups after intubation.
Discussion During the induction of general anesthesia, laryngoscopy and tracheal intubation are frequently performed. While securing the patient airway, hemodynamic changes may occur. The anesthesiologist, trying to make the induction as smooth as possible, learned to appreciate the importance of that sequence of events. Some patients more than others may experience substantial hemodynamic changes during the induction and intubation phase. Therefore, meticulous preparation before endotracheal intubation is warranted. Our study demonstrated that orotracheal intubation, facilitated by FOB, required more time, compared with direct laryngoscopy orotracheal intubation. This was previously reported, both during the learning curve and also in experienced hands.1,2 However, the increased duration of the fiberoptic procedure did not affect the hemodynamic response or catecholamine levels, as compared with the direct laryngoscopy method. It brings us to the question, what is the most important factor that cause the stress response during intubation? Researchers have tried to separate the effect of laryngoscopy from that of tracheal intubation. The effect of intubation alone was studied by Shribman et al.23 who compared the cardiovascular response to direct laryngoscopy, with and without tracheal intubation. They found no difference between the two, and concluded that the laryngoscopy itself is the major contributor to the stress response. Adachi et al.24 studied the cardiovascular response to a fiberoptic-guided
Hemodynamic response to tracheal intubation: Barak et al.
Figure 2. Norepinephrine concentrations (nmol · L–1), mean ⫾ SD. Group 1 ⫽ direct laryngoscopy, Group 2 ⫽ fiberoptic intubation. *p ⬍ 0.05 compared with Group 1.
intubation with television monitoring. They hypothesized that since that technique is minimally invasive, it causes a relatively low cardiovascular response. Their results failed to demonstrate the superiority of that method over classical laryngoscopy, and they concluded that endotracheal intubation itself is the major stimulus to cardiovascular response. In that study,24 however, the FOB remained in the pharynx and did not cross the vocal cords. In addition, catecholamine levels were not measured. Our results show similar hemodynamic response and catecholamine levels to both intubation techniques. We therefore cannot conclude whether the airway instrumentation or orotracheal intubation was the main cause for the hemodynamic changes. In our study, we examined catecholamine blood levels and attempted to determine whether they correlated with cardiovascular parameters. Plasma catecholamine levels did not increase after the induction of general anesthesia in either group. One minute following tracheal intubation, HR and BP increased whereas catecholamine levels decreased. Similar results were previously reported in studies that failed to demonstrate an increase in epinephrine level following intubation.5,6 In these reports, the norepinephrine level was only mildly elevated after intubation, and only in one of the two intubation techniques that were evaluated.5,6 Although a correlation between BP and HR and catecholamine might be expected, only one study has demonstrated this.4 Therefore, this concept may deserve further evaluation. In conclusion, we found that the stress response to fiberoptic orotracheal intubation is similar to orotracheal intubation facilitated by the Macintosh laryngoscopy blade. No significant differences in hemodynamic parameters, or in catecholamine blood levels were found between the groups. Fiberoptic intubation is an important adjunct in airway management. Because it creates a similar stress response to regular laryngoscopy intubation, it should be safely applied whenever indicated.
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