458 GENERAL ANESTHESIA The bispectral index response to tracheal intuba- tion is similar in normotensive and hypertensive patients [La réponse de l’index bispectral à l’intubation endotrachéale est similaire chez les patients normotendus et hypertendus] Masayasu Nakayama MD,* Hiromichi Ichinose MD,† Shuji Yamamoto MD,† Noriaki Kanaya MD,* Akiyoshi Namiki MD PhD* Purpose: To compare the hemodynamic and bispectral index (BIS) Conclusion : Les patients hypertendus ou non réagissent par la même responses to tracheal intubation in normotensive and hypertensive réaction d’éveil (mesurée par le BIS) à l’intubation endotrachéale mal- patients. gré l’augmentation de la réponse vasopressive chez les hypertendus. Method: Three minutes after induction of anesthesia with thiamy- lal and fentanyl, tracheal intubation was performed in 24 nor- motensive and 22 hypertensive patients. Heart rate (HR), mean arterial pressure (MAP), and BIS were measured every minute. HE bispectral index (BIS), obtained from Results: Tracheal intubation increased HR, MAP, and BIS in both bispectral analysis of the electroencephalo- normotensive and hypertensive patients. The increase in MAP was gram (EEG), reflects the hypnotic compo- significantly greater in hypertensive patients than in normotensive nent of anesthesia.1–3 Previous studies have patients, but there were no differences in HR or BIS in the two T shown that tracheal intubation is associated with groups of patients. increases in BIS as well as heart rate (HR) and blood Conclusion: Patients with and without hypertension exhibit the pressure.4–6 Therefore, intubation is likely to affect same arousal response (as measured by BIS) to tracheal intubation both the hypnotic and antinociceptive components of despite the enhanced vasopressor response in hypertensive anesthesia. Although the enhanced hemodynamic patients. response to intubation in patients with hypertension is well documented,7,8 the degree of the arousal response has not been studied. The objective of the Objectif : Comparer les réponses hémodynamiques et de l’index bis- present study was to compare the changes in hemody- pectral (BIS) à l’intubation endotrachéale chez des patients normo- namic responses and BIS induced by tracheal intuba- tendus et hypertendus. tion in normotensive and hypertensive patients. Méthode : Trois minutes après l’induction de l’anesthésie avec du thia- mylal et du fentanyl, l’intubation endotrachéale a été réalisée chez 24 Methods patients normotendus et 22 hypertendus. La fréquence cardiaque The study was approved by our local Ethics Committee, (FC), la tension artérielle moyenne (TAM) et le BIS ont été mesurés à and informed consent for participation in the study was toutes les minutes. obtained from each patient. Twenty-four normotensive Résultats : L’intubation endotrachéale a fait augmenter la FC, la patients (Group N) and 22 hypertensive patients TAM et le BIS chez les patients des deux groupes. L’accroissement de (Group H) scheduled for elective surgery with general la TAM a été significativement plus élevé chez les hypertendus, mais il anesthesia were enrolled. All hypertensive patients had n’y a pas eu de différence intergroupe pour la FC ou le BIS. a diagnosis of essential hypertension. They were already receiving oral medication consisting of a calcium antag- From the Department of Anesthesiology,* Sapporo Medical University School of Medicine, Sapporo; and the Division of Anesthesia,† Obihiro Kosei Hospital, Obihiro, Japan. Address correspondence to: Dr. Masayasu Nakayama, Department of Anesthesiology, Sapporo Medical University School of Medicine, South 1, West 16, Chuoku, Sapporo 060-8543, Japan. Phone: +011 611-2111; Fax: +011 631-9683; E-mail: [email protected] Accepted for publication December 11, 2001. Revision accepted January 18, 2002. CAN J ANESTH 2002 / 49: 5 / pp 458–460 Nakayama et al.: BIS AND INTUBATION 459 onist (nifedipine or nicardipine) and received their med- period. All data are expressed as means ± SD. Statistical ication on the day of surgery. None of the patients had analysis was performed using two-way analysis of vari- an abnormal electrocardiogram (ECG) or neurological ance (between the groups) followed by post hoc analy- disorders on admission. ses with Fisher’s protected least significant difference No premedication was given before surgery. ECG test. The chi-squared test was used to compare gender (lead II) and hemoglobin oxygen saturation (SpO2) differences between the two groups. A P value < 0.05 were monitored continuously throughout the proce- was considered statistically significant. dure. HR and mean arterial pressure (MAP) were measured by an automatic oscillographic method. BIS Results (version 3.4) was measured continuously on an EEG Patients’ characteristics, baseline hemodynamics and monitor (Model A1050; Aspect Medical System, BIS in the two groups were similar (Tables I and II). Natick, MA, USA) using BisSensor strips (Aspect MAP and BIS decreased significantly after induction Medical System). The impedance of each electrode of anesthesia, but there was no significant change in was maintained at less than 2 kilohms. HR in either group. The decreases in MAP and BIS General anesthesia was induced with 5 mg·kg–1 of with anesthetic induction (preintubation) were similar thiamylal and 2 µg·kg–1 of fentanyl iv. After loss of con- in the two groups. sciousness, 0.1 mg·kg–1 of vecuronium iv was given, In both groups, intubation caused significant and the patient’s lungs were ventilated by mask with 6 increases in HR, MAP and BIS. The increases in MAP L·min–1 of oxygen via a semiclosed circle system. Three after intubation were sustained for three minutes in minutes after induction, direct laryngoscopy for orotra- Group N and for four minutes in Group H. The great- cheal intubation was initiated by one of the authors est increases in hemodynamic variables occurred at (M.N.) and was accomplished within 30 sec. After intu- one minute after intubation. The significant increases bation, ventilation was controlled with 1% sevoflurane in BIS were seen only at two minutes after intubation in oxygen for five minutes. in both groups. The increase in MAP after intubation HR, MAP, and BIS were recorded before the induc- was significantly greater in Group H than in Group N, tion of anesthesia and every minute during the study but there were no inter-group differences at any time in increases in HR and BIS due to intubation. Abnormal ECG or SpO2 less than 98% was not TABLE I Demographic data observed throughout the study period. None of the Normotensive Hypertensive patients complained of awareness during anesthesia. Sex (female / male) (n) 13/11 11/11 Age (yr) 41 ± 10 45 ± 11 Discussion Weight (kg) 67 ± 12 70 ± 10 The present study shows that the hypertensive Height (cm) 166 ± 14 165 ± 8 response to tracheal intubation was greater in patients Duration of 22 ± 7 20 ± 9 with hypertension than in normotensive patients, laryngoscopy (sec) whereas the increases in BIS in these two groups of Values are means ± SD. No statistically significant differences patients were not different. between groups. Although a reflex response to a noxious stimulus TABLE II Changes in mean arterial pressure (MAP), heart rate (HR), and bispectral index (BIS) Baseline Preintubation After intubation 1 min 2 min 3 min 4 min 5 min Normotension MAP (mmHg) 92 ± 9 85 ± 14 109 ± 18* 103 ± 21* 98 ± 19* 90 ± 15 85 ± 13 HR (beats·min–1) 71 ± 8 75 ± 12 91 ± 15* 88 ± 15* 85 ± 13* 76 ± 11 66 ± 13 BIS 97 ± 3 54 ± 7 56 ± 8 62 ± 8* 55 ± 7 53 ± 8 50 ± 6 Hypertension MAP (mmHg) 95 ± 10 82 ± 11 126 ± 25*† 122 ± 25*† 111 ± 22*† 99 ± 19* 92 ± 20 HR (beats·min–1) 75 ± 11 72 ± 14 106 ± 16*† 98 ± 16* 88 ± 16* 77 ± 13 65 ± 9 BIS 96 ± 2 56 ± 9 58 ± 9 64 ± 8* 60 ± 6 58 ± 8 52 ± 12 Values are means ± SD; *P < 0.05 vs preintubation; †P < 0.05 vs normotension; Preintubation = after induction of anesthesia – prior to intubation. 460 CANADIAN JOURNAL OF ANESTHESIA due to tracheal intubation is mediated at the subcorti- tanil in healthy volunteers. Anesthesiology 1997; 86: cal level,4 peripheral stimuli reach the brain through 836–47. the ascending reticular activating systems of the brain 4 Mi W-D, Sakai T, Takahashi S, Matsuki A. stem and may affect the state of consciousness.9 Mi et Haemodynamic and electroencephalograph responses al.4 reported that BIS was significantly increased by to intubation during induction with propofol or laryngoscopy and intubation during infusion of propofol/fentanyl. Can J Anaesth 1998; 45: 19–22. propofol with or without fentanyl pretreatment. 5 Guignard B, Menigaux C, Dupont X, Fletcher D, Guignard et al.5 demonstrated that laryngoscopy and Chauvin M. The effect of remifentanil on the bispectral intubation were associated with an increase in BIS index change and hemodynamic responses after orotra- during target-controlled infusion of propofol. In cheal intubation. Anesth Analg 2000; 90: 161–7. agreement with these reports, we found that tracheal 6 Coste C, Guignard B, Menigaux C, Chauvin M. intubation after anesthetic induction with thiamylal Nitrous oxide prevents movement during orotracheal and fentanyl also significantly increased BIS. intubation without affecting BIS value. Anesth Analg It is well known that patients with hypertension 2000; 91: 130–5. show greater pressor responses to tracheal intubation 7 Prys-Roberts C, Greene LT, Meloche R, Foëx P. Studies than do normotensive patients.7,8 Arteriolar luminal of anaesthesia in relation to hypertension. II: haemody- narrowing, blunted baroreflex responses, and namic consequences of induction and endotracheal increased sympathetic activity in hypertensive patients intubation. Br J Anaesth 1971; 43: 531–45. have been proposed to be factors responsible for the 8 Omote K, Kirita A, Namiki A, Iwasaki H. Effects of exaggerated hemodynamic changes.10,11 These nicardipine on the circulatory responses to tracheal responses should increase the risk of perioperative intubation in normotensive and hypertensive patients.