GlideScope Video Laryngoscope Group Research Articles

Haemodynamic responses following orotracheal intubation in patients with hypertension---Macintosh direct laryngoscope versus Glidescope®videolaryngoscope.

Background and Aims:Glidescope®videolaryngoscope (GVL) is a video intubation system with 60° angle blade that provides excellent laryngeal view, does not require alignment of oral, pharyngeal, and laryngeal axes for visualisation of glottis, thus causing less stimulation of orolaryngopharynx. The aim of this study was to compare haemodynamic responses (blood pressure and heart rate) and airway morbidity using the Macintosh direct laryngoscope (MDL) and the Glidescope®videolaryngoscope (GVL) in hypertensive patients.Methods:Fifty patients with hypertension controlled on antihypertensive medications scheduled for elective surgery under general anaesthesia were randomly assigned to group GVL (n = 25) or group MDL (n = 25). Heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean blood pressure (MBP) were recorded at baseline, after induction, pre-intubation, at intubation, 1, 2, 3, 4, and 5 min after intubation. Time to intubation, number of attempts, complications during intubation, and postoperative airway complications (sore throat, hoarseness, dysphagia, and cough) were also recorded.Results:There was a statistically significant increase in SBP, DBP, and MBP at intubation [(P = 0.003, 0.013, 0.03), 1 min (P = 0.001, 0.012, 0.02), 2 min (P = 0.04, 0.02, 0.04), and 3 min (P = 0.02, 0.01)] in the MDL group as compared to GVL group. The time to intubate was significantly greater in the GVL group as compared to MDL group (P = 0.0006). There was no significant difference in the incidence of intraoperative and postoperative airway complications.Conclusion:In the hands of an experienced anaesthesiologist, the use of GVL in controlled hypertensive patients is associated with less haemodynamic response as compared to Macintosh Laryngoscope without any increase in airway complications.

Randomized Prospective Comparison of Glidescope Video Laryngoscope with Macintosh Laryngoscope in Adult who Underwent Thyroid or Parathyroid Surgery Using Neuromonitorization.

Objectives:The present study aims to compare the effects of Glidescope Video Laryngoscope (GVL) and Machintosh Laryngoscope (ML) on the hemodynamic response, intubation time and mucosal damage in adult patients who underwent thyroid or parathyroid surgery using neuromonitorization.Methods:In this study, 180 patients, aged between 22 and 65 classified as Class I-II in ASA (American Society of Anesthesiologists) and operated under elective conditions were included. Patients were assigned into two groups: Patients intubated with GVL Group G (n=90) and patients intubated with ML Group M (n=90). In both groups, intubation time and the number of trials were recorded. HR (Heart Rate), SpO2 (Peripheral Capillary Oxygen Saturation), SBP (Systolic Blood Pressure), DBP (Diastolic Blood Pressure) and MBP (Mean Blood Pressure) scores were recorded at preinduction, post-induction, post-intubation and three minutes after intubation. Post-operative intubation-associated complications were recorded.Results:Post intubation HR, DBP and MBP scores were found to be significantly higher in Group M than Group G (p=0,006, p=0.013, p=0.011). Intubation time was found to be significantly higher in Group G than in group M (35.3±10.3, 22.1±7.7 sec). There was no significant difference between the groups’ number of trials and intubation-associated complications.Conclusion:Despite its long intubation time, we believe that GVL may be the first choice laryngoscopy method in the thyroid or parathyroid cases that intubated with a low dose muscle relaxant for neuromonitoring since it has a slight effect than ML on hemodynamism it does not increase mucosal damage and has improved visibility.

GlideScope® cobalt video laryngoscope versus direct Miller laryngoscope for lateral position-tracheal intubation in neonates with myelodysplasia: A prospective randomized study.

Background and Objective:Anesthesiologists encounter difficulties during laryngoscopy and tracheal intubation of neonates with myelodysplasia. Tracheal intubation in lateral position in such cases deemed profitable but not easy because of the compromised laryngeal view. We compared GlideScope video laryngoscope (GVL) versus conventional Miller direct laryngoscope (DL) for tracheal intubation in laterally positioned neonates with myelodysplasia.Materials and Methods:Sixty neonates scheduled for elective surgical repair of meningeocele or meningeomyelocele under general anesthesia were allocated randomly for endotracheal intubation using GVL or DL. Percentage of glottis opening (POGO) scores, time to best glottis view (TBGV), endotracheal tube passage time (TPT), intubation time (IT), intubation attempts, and overall success rate of intubation were recorded.Results:TBGV was significantly shorter in GVL group (median = 6.8 s, range = 3.5–28.2 s) in comparison with DL group (median = 8.4 s, range = 4.8–32.7 s) (P = 0.01); however, TPT and IT were comparable. POGO scores were significantly higher with GVL group than DL group (median = 93.8, range = 45–100 and median = 82.4, range 10–100, respectively) (P = 0.001). Overall success of intubation was the same; however, three patients in GVL group required a second attempt for intubation in comparison with five patients in DL group. One patient in DL group required a third attempt.Conclusion:In laterally positioned neonates, GVL is easier than DL with a similar intubation time, comparable time required for tube passage, better views of the glottis, shorter times to obtain the best glottic view, and high success rate as compared with DL. GlideScope seems to be an effective approach for endotracheal intubation of laterally positioned neonates with myelodysplasia.

Hemodynamic changes following endotracheal intubation in patients undergoing cesarean section with general anesthesia: application of glidescope® videolaryngoscope versus direct laryngoscope.

BackgroundEndotracheal intubation is usually associated with hemodynamic changes, especially in patients undergoing cesarean section by general anesthesia. GlideScope® videolaryngoscope (GVL) is a novel video laryngoscope, which does not need direct exposure of vocal cords and produces lesser hemodynamic changes due to lower degrees of trauma and stimuli to oropharynx than the Macintosh direct laryngoscope (MDL).ObjectivesThe aim of this study was to compare hemodynamic changes following endotracheal intubation with GVL and MDL in patients undergoing cesarean section by general anesthesia.Materials and MethodsSeventy patients undergoing elective cesarean section by general anesthesia requiring endotracheal intubation were randomly allocated to be intubated with either GVL (n = 35) or MDL (n = 35). Systolic, diastolic and mean arterial blood pressure (MAP), as well as pulse rates, and rate pressure product (RPP) were compared at baseline, after induction of anesthesia, and after intubation at one-minute interval for five minutes between the two groups. The patients were also compared for Mallampati score, sore throat, intubation time and neonates’ Apgar scores.ResultsThe patients were similar regarding systolic, diastolic and mean arterial blood pressure. Pulse rate changes were significantly lower only at 1 and 3 minutes in the GVL group. The intubation times were 9.3 ± 1.4 and 10.6 ± 1.7 seconds in the MDL and GVL groups, respectively (P > 0.05). RPP was also lower in the GVL group at 1 and 2 minutes (P < 0.05) and returned to baseline afterwards. There was no significant difference between the groups for Mallampati score, sore throat and Apgar scores.ConclusionsOur study revealed that hemodynamic parameters with GVL are only better preserved in the first three minutes after intubation in patients undergoing elective cesarean section and patients are similar regarding intubation time, sore throat and Apgar score.

Hemodynamic changes following endotracheal intubation with glidescope(®) video-laryngoscope in patients with untreated hypertension.

Background:Tracheal intubation can be associated with considerable hemodynamic changes, particularly in patients with uncontrolled hypertension. The GlideScope® video-laryngoscope (GVL) is a novel video laryngoscope that does not need direct exposure of the vocal cords, and it can also produce lower hemodynamic changes due to lower degrees of trauma and stimuli to the oropharynx than a Macintosh direct laryngoscope (MDL).Objectives:The aim of this clinical trial was to compare hemodynamic alterations following tracheal intubation with a GVL and MDL in patients with uncontrolled hypertension.Patients and Methods:Sixty patients who had uncontrolled hypertension and scheduled for elective surgery requiring tracheal intubation, were randomly assigned to receive intubated with either a GVL (n = 30) or a MDL (n = 30). Intubation time, heart rate, rate pressure product (RPP), and mean arterial blood pressure (MAP), were compared between the two groups at; baseline, following induction of anesthesia, after intubation, and at one minute intervals for 5 minutes.Results:A total of 59 patients finished the study. Intubation time was longer in the GVL group (9.80 ± 1.27 s) than in the MDL group (8.20 ± 1.17 s) (P < 0.05). MAP, pulse rate, and RPP were lower in the GVL than the MDL group after endotracheal intubation (P < 0.05). MAP, heart rate, and RPP returned to pre-intubation values at 3 and 4 minutes after intubation in the GVL and MDL groups, respectively (P < 0.05).Conclusions:Hemodynamic fluctuations in patients with uncontrolled hypertension after endotracheal intubation were lower with the GVL than the MDL technique.

Effect of video laryngoscopy on trauma patient survival

Many resuscitation scenarios include the use of emergency intubation to support injured patients. New video-guided airway management technology is available, which may minimize the risk to patients from this procedure. This was a controlled clinical trial conducted in the trauma receiving unit in a university-affiliated urban hospital in which 623 consecutive adult patients requiring emergency airway management were prospectively randomized to intubation with either the direct laryngoscope (DL) or the GlideScope video laryngoscope (GVL) device. The primary outcome was survival to hospital discharge. There was no significant difference in mortality between the GVL group (28 [9%] of 303) and the DL group (24 [8%] of 320) (p = 0.43) for all patients. Within a smaller cohort identified retrospectively, there was a higher mortality rate seen in the subgroup of patients with severe head injuries (head Abbreviated Injury Scale [AIS] score > 3) who were randomized to intubation with GVL (22 [30%] of 73) versus DL (16 [14%] of 112) (p = 0.047). Among all patients, median intubation duration in seconds was significantly higher for the GVL group (median, 56; interquartile range, 40-81) than for the DL group (median, 40; interquartile range, 24-68) (p < 0.001). Among those with severe head injuries, median intubation duration in seconds was also significantly higher for the GVL group (median, 74) than for the DL group (median, 65) (p < 0.003). Correspondingly, this group also experienced a greater incidence of low oxygen saturations of 80% or less (27 [50%] of 54 for the GVL group and 15 [24%] of 63 for the DL group; p = 0.004). There were no significant differences between the two groups in first-pass success (80% for GVL and 81% for DL, p = 0.46). Use of the GlideScope did not influence survival to hospital discharge among all patients and was associated with longer intubation times than direct laryngoscopy. Among the video laryngoscope cohort, a smaller subgroup of severe head injury trauma patients identified retrospectively seemed to be associated with a greater incidence of hypoxia of 80% or less and mortality.

Comparison of GlideScope video-laryngoscope and Macintosh laryngoscope for double-lumen tube intubation

Objective To compare the GlideScope video-laryngoscope and Macintosh laryngoscope for double-lumen tube (DLT) intubation.Methods Seventy ASA Ⅰ-Ⅲ patients,aged 18-75 yr,scheduled for thoracic surgery and requiring one-lung ventilation,were randomly divided into 2 groups (n =35 each):Macintosh laryngoscope group (group M) and GlideScope video-laryngoscope group (group G).Anesthesia was induced with propofol,fentanyl and rocuronium.The exposure of glottis obtained with Macintosh laryngoscope and GlideScope video-laryngoscope was assessed using Cormack-Lehane grade.DLT intubation was assisted with Macintosh laryngoscope or GlideScope video-laryngoscope.The Cormack-Lehane grade,difficulty of DLT placement,and reverse DLT placement were recorded.The success rate of DLT placement at first attempt and intubation time were also recorded.Blood pressure and heart rate were recorded before intubation and at 0 and 3 min after intubation.The postoperative side effects were recorded.Results Compared with M group,the intubation time was significantly prolonged,the difficulty of DLT placement and blood pressure at 0 and 3 min after intubation were increased in G group (P ＜ 0.05).There was no significant difference in the success rate of DLT placement at first attempt,rate of reverse DLT placement,Comark-Lehene grade and heart rate at each time point between the two groups (P ＞0.05).The Comark-Lehene grade obtained with GlideScope video-laryngoscope was superior to that obtained with Macintosh laryngoscope in G group (P ＜ 0.05).Conclusion GlideScope video-laryngoscope can provide a better exposure of glottis and improvement in the intubating conditions,but the method is more complex and the response to intubation is stronger than Macintosh laryngoscope for DLT intubation. Key words: Laryngoscopes; Intubation,intratracheal

Abstract 93: GlideScope Video Laryngoscopic vs Macintosh Laryngoscopic Intubation During Cardiopulmonary Resuscitation: An Observational Study and Propensity Score Matching Analysis

Introduction: The use of video laryngoscope during cardiopulmonary resuscitation (CPR) has not been extensively studied. A randomized controlled trial comparing the efficacy between video and direct laryngoscopy during CPR is logistically difficult. The objective of this study was to determine whether the first-attempt success rate of intubation using GlideScope video laryngoscope (GVL) is different to Macintosh laryngoscope (MAC) during CPR. Hypothesis: We hypothesized that the first-attempt success rate of intubation using GVL would be higher than MAC during CPR. Methods: This was an observational study using a multicenter airway registry data of six emergency departments (EDs) following current CPR guidelines - minimize interruptions in chest compressions. Adults of out-of-hospital cardiac arrest intubated in the EDs from March 2006 to December 2010 were enrolled. The primary outcome was success with first attempt. Secondary outcome was intubation failure. An attempt was defined as the introduction of the laryngoscope into the mouth. Failure was defined as an esophageal intubation, changing to a different device or intubator, or more than three attempts. To reduce the effect of selection bias and potential confounding, we performed rigorous adjustment for significant differences in patient and intubator factors using a propensity-score (PS) matching analysis. The adjusted odds ratio (OR) and its 95% confidence interval (CI) for the outcomes between the laryngoscopes were calculated. Results: A total of 1867 eligible patients were enrolled in this study. Of those patients, GVL was used for initial attempt in 180 (9.6%). Overall first-attempt success rate were 86.1% in GVL group and 80.9% in MAC group ( p =0.090), but failure rate was significantly different between two groups (GVL vs. MAC; 7.2% vs. 14.9%, p =0.006) in crude analysis. Using PS matching, 177 patients were equally assigned to each group. The adjusted OR for the first-attempt success and failure rate in GVL group compared to MAC group was 1.37 (95% CI 0.76-2.45) and 0.46 (95% CI 0.23-0.93), respectively. Conclusions: The first-attempt success rates of intubation during CPR were not significantly different between GVL and MAC. However, intubation failure rate of GVL was lower than MAC.

A comparative study on the usefulness of the Glidescope or Macintosh laryngoscope when intubating normal airways

BackgroundThe Glidescope Videolaryngoscope (GVL) is a newly developed video laryngoscope. It offers a significantly improved laryngeal view and facilitates endotracheal intubation in difficult airways, but it is controversial in that it offers an improved laryngeal view in normal airways as well. And the price of GVL is expensive. We hypothesized that intubation carried out by fully experienced anesthesiologists using the GVL with appropriate pre-anesthetic preparations offers an improved laryngeal view and shortened intubation time in normal airways. Therefore, the aim of this study was to compare the GVL with the Macintosh laryngoscope in normal airways and to determine whether GVL can substitute the Macintosh laryngoscope.MethodsThis study included 60 patients with an ASA physical status of class 1 or 2 requiring tracheal intubation for elective surgery. All patients were randomly allocated into two groups, GVL (group G) or Macintosh (group M). ADS (airway difficulty score) was recorded before induction of anesthesia. The anesthesiologist scored vocal cord visualization using the percentage of glottic opening (POGO) visible and the subjective ease of intubation on a visual analogue scale (VAS). The time required to intubate was recorded by an assistant.ResultsThere was a significant increase in POGO when using the GVL (P < 0.05). However, there was no difference in the time required for a successful tracheal intubation using the GVL compared with the Macintosh laryngoscope. The VAS score on the ease of intubation was significantly lower for the GVL than for the Macintosh laryngoscope (P < 0.05).ConclusionsGVL could be a first-line tool in normal airways.

Comparisons of the GlideScope and Macintosh Laryngoscope in Tracheal Intubation by Medical Students on Fresh Human Cadavers

Objective The GlideScope Video Laryngoscope (GS) is an intubating device that provides equal or better glottic views than conventional laryngoscopes, but correct tube placement is more time-consuming, even when performed by experienced operators. The aim of this study was to investigate the use of the GS compared with the more conventional Macintosh laryngoscope in easy and difficult tracheal intubation when performed by inexperienced medical students on fresh human cadavers Patients and Methods Forty-one medical students were assigned to perform tracheal intubation using the direct Macintosh laryngoscope (DL) and the GS. Each student was given four attempts, with a maximum of 180 seconds for each attempt, to successfully intubate the trachea with a 6.5-mm tracheal tube in each of two scenarios, one with an easy airway and the other with a difficult airway cadaver. Results The total time of intubation for the easy airway cadaver was significantly longer in the GS group (61.4 ± 4.8 seconds vs. 40.6 ± 5.3 seconds; p < 0.001) despite the modified Cormack-Lehane scores showing no difference between the two groups. In the difficult airway cadaver, total time of intubation was significant shorter in the GS group (64.3 ± 6.5 seconds vs. 98.7 ± 10.2 seconds; p < 0.001) Conclusion Most inexperienced operators found the GS to be more time-consuming for tracheal intubation than DL in the easy airway cadaver. However, an obvious advantage was demonstrated when the GS was used for the difficult airway.

Circulatory responses to nasotracheal intubation: comparison of GlideScope® videolaryngoscope and Macintosh direct laryngoscope

The GlideScope videolaryngoscope (GSVL) has been shown to have no special advantage over the Macintosh direct laryngoscope (MDL) in attenuating the circulatory responses to orotracheal intubation, but no study has compared the circulatory responses to nasotracheal intubation (NTI) using the two devices. This prospective randomized clinical study was designed to determine whether there was a clinically relevant difference between the circulatory responses to NTI with the GSVL and the MDL. Seventy-six adult patients were randomly allocated equally to the GSVL group and the MDL group. After induction of anesthesia, NTI was performed. Non-invasive blood pressure (BP) and heart rate (HR) were recorded before induction (baseline values) and immediately before intubation (post-induction values), at intubation and every minute for a further five minutes. During the observation, times required to reach the maximum values of systolic BP (SBP) and HR, times required for recovery of SBP and HR to postinduction values and incidence of SBP and HR percent changes > 30% of baseline values were also noted. The product of HR and systolic BP, i.e. rate pressure product (RPP), and the areas under SBP and HR vs. time curves (AUC(SBP) and AUC(HR)) were calculated. The NTI with the GSVL resulted in significant increases in BP, HR and RPP compared to postinduction values, but these circulatory changes did not exceed baseline values. BPs at all measuring points, AUC(SBP), maximum values of BP and incidence of SBP percent increase > 30% of baseline value during the observation did not differ significantly between groups. However, HR and RPP at intubation and their maximum values, AUC(HR) and incidence of HR percent increase > 30% of baseline value were significantly higher in the MDL group than in the GSVL group. Times required for recovery of SBP and HR to postinduction values were significantly longer in the MDL group than in the GSVL group. The pressor response to NTI with the GSVL and the MDL was similar, but the tachycardiac response to NTI was lesser and of a shorter duration when using a GSVL than when using an MDL.

A Comparison of GlideScope® Videolaryngoscopy to Direct Laryngoscopy for Nasotracheal Intubation

In this study, we compared the effectiveness of direct laryngoscopy (DL) and the GlideScope videolaryngoscope (GVL) for nasotracheal intubation, as judged by the time to intubation (TTI-the primary outcome) and the ease of intubation. Seventy patients requiring nasotracheal intubation for elective surgery were randomly allocated to intubation with the GVL or DL. TTI was assessed by a blinded observer. Operators were blinded until the start of laryngoscopy. A Visual Analog Scale assessed the ease of intubation. The number of intubation attempts, number of failures, glottic grades, amount of bleeding, usage of Magill forceps, and the severity of postoperative sore throat were recorded. The median TTI was 23.2 s faster with the GVL (43.5 s, interquartile range [IQR]: 39.8-67.3) than with DL (66.7 s, IQR: 53.8-89.9), P = 0.0023. Nasotracheal intubation was easier with the GVL than with DL (Visual Analog Scale 10 mm, IQR: 5.5-18, vs 20 mm, IQR: 10-32, P = 0.0041). The incidence of postoperative moderate or severe sore throat was significantly reduced in the GVL group (9% vs 34%, P = 0.018). Glottic exposure was significantly better with the GVL. Magill forceps were not used in the GVL group, but were used 49% of the time in the DL group, P < 0.0001. The incidence and severity of bleeding were similar between groups. Compared with DL, the GVL has superior performance characteristics when used for nasotracheal intubation and demonstrates an important reduction of postoperative sore throat. The GVL has a clear role in routine nasotracheal intubation.

Comparison of hemodynamic responses to orotracheal intubation with the GlideScope® videolaryngoscope and the Macintosh direct laryngoscope

Study Objectives To identify the hemodynamic responses to orotracheal intubation using a GlideScope® videolaryngoscope (GSVL) in healthy adults, and to determine whether the GSVL could attenuate the hemodynamic response to orotracheal intubation compared with the Macintosh direct laryngoscope (MDLS). Design Randomized study. Setting Operating room, Plastic Surgery Hospital of the Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, People's Republic of China. Patients 57 adult, ASA physical status I patients, scheduled for elective plastic surgery during general anesthesia requiring orotracheal intubation. Interventions Patients were randomly allocated to either the GSVL group (n = 30) or the MDLS group (n = 27). Anesthesia was induced with intravenous injection of fentanyl 2 μg/kg, propofol 2 mg/kg, and vecuronium 0.1 mg/kg. Orotracheal intubation was started two minutes after vecuronium injection. All intubation procedures were performed by a single anesthesiologist experienced in using an MDLS and a GSVL. After intubation, anesthesia was maintained with 1% isoflurane and 60% nitrous oxide in oxygen. Measurements and Main Results Noninvasive blood pressure (BP) and heart rate (HR) were recorded before (baseline values) and immediately after induction (postinduction values), at intubation, and for 5minutes at one-minute intervals. Maximal BP and HR values during the observation and intubation times were also noted. The product of HR and systolic BP (ie, the rate-pressure product [RPP]) was calculated. Intubation time was significantly longer in the GSVL group than in the MDLS group ( P < 0.01). Except for maximal value of diastolic BP in the GSVL group, increases in BPs during the observation in the two groups did not significantly exceed baseline values ( P > 0.05). In the GSVL group, HR and RPP at intubation were significantly higher than their baseline values, and HR increases lasted for 4 minutes. In the MDLS group, HR at intubation was also significantly higher than its baseline value, but the tachycardic response lasted only for 1 minute. During the observation, there were no significant differences between the two groups in BPs, HRs, or RPPs at any time points or in their maximal values. Conclusions The hemodynamic responses to orotracheal intubation using a GSVL and an MDLS were similar. The GSVL had no any special advantage over the MDLS in attenuating the hemodynamic responses to orotracheal intubation.

Double-lumen tube intubation using video laryngoscopy causes a milder cardiovascular response compared to classic direct laryngoscopy

Objective:To determine whether there is a clinically relevant difference between the circulatory responses to double-lumen tube intubation (DLTI) with the GlideScope video laryngoscope versus the Macintosh direct laryngoscope.Methods:Eighty adult patients requiring double-lumen tubes for thoracic surgery were randomly and equally allocated to either a Macintosh direct laryngoscope group (DL group, n = 40) or a Glide Scope video laryngoscope group (GS group, n = 40). DLTI was performed after airway evaluations and induction of anesthesia. Systolic blood pressure (SBP) and heart rate (HR) were recorded before induction (baseline values), immediately before intubation (post-induction values), at intubation and after intubation. Rate-pressure-product (RPP), and the areas under SBP- and HR-time curves were calculated. All data obtained by the two devices were compared.Results:After laryngoscope insertion, SBP of DL and GS groups changed significantly differently (13.1% vs. 4.6%, P< 0.001), while HR changed similarly (17.2% vs. 14.6%, P = 0.074). One minute after intubation, both SBP and HR significantly increased in both groups (SBP: 11.6% vs. 11.9%; HR: 18.4% vs. 10.8%), but there were no significant differences between the two groups. RPP significantly increased in both groups after laryngoscope insertion (32.6%, P=0.001; 18.2%, P=0.002), and there was a significant difference between the two groups (P =0.001). Throughout intubation, the areas under SBP-time curves had a significant difference between the two groups (P = 0.042), while those under HR-time curves did not differ significantly (P=0.06).Conclusion:The intubation response was most significant upon laryngoscope insertion during the whole intubation process. The GlideScope video laryngoscope induced milder circulatory fluctuations than the Macintosh direct laryngoscope did, suggesting that DLTI using video laryngoscopy can help reduce the cardiovascular response to intubation.