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There has always been a big question if it is possible to intubate the trachea without neuromuscular blocking agents. Tracheal intubation with deep inhalational induction is done in children and in special conditions where neuromuscular blockers cannot be used like hyperkalemia, plasma cholinesterase deficiency, penetrating eye injury, burns, recent spinal cord injury and known allergic reactions.
Some neuromuscular disorders for example myasthenia gravis alter the clinical pharmacology of neuromuscular blocking agents and may cause alterations in the choice, dosage, and reversal of the neuromuscular blocker. Hence in these scenarios, tracheal intubation free of neuromuscular blocking agent-free facilitation of tracheal intubation is frequently used.1
This technique is also useful where neuromuscular blockade is not needed to facilitate surgical access like ambulatory surgery.2,3 Neurosurgical procedures which needs evoked potential monitoring and some surgical procedures such as certain ENT like facial nerve exploration and some thyroid surgery which needs the use of a nerve stimulator to identify nerves or to confirm their integrity, a neuromuscular block free based intubation is required.
Various techniques of induction can be used to achieve tracheal intubation free of neuromuscular blockade. Intravenous or inhalational induction can be used. Single-dose propofol without concomitant narcotic has been used in the past for tracheal intubation but because of inferior intubating conditions, it was used with concomitant fentanyl which lead to better intubating conditions.4
Pharyngeal and laryngeal reflexes during laryngoscopy was more depressed with propofol than thiopental when given in an equipotent dose which is the reason for its use for facilitating laryngeal mask airway placement. Propofol was found to have better intubating conditions compared to thiopentone when combined with remifentanil.5,6
High concentrations of sevoflurane is usually used in children for intubation without neuromuscular blockade.7 Sevoflurane has been shown to be suitable for anesthetic induction in adults and it can be used alone or with nitrous oxide.8 Both sevoflurane and propofol induction has been used in management of difficult airway.9 But sevoflurane has its advantage in the maintenance of spontaneous ventilation. Sevoflurane mask induction with adjuvants such as midazolam or fentanyl significantly reduce the time to achieve acceptable tracheal intubating conditions in adults.10
The purpose of this study was to determine if sevoflurane - fentanyl combination would offer equivalent intubating conditions when compared with propofol - fentanyl combination.
REVIEW OF LITERATURE
The literature was searched and the studies which was conducted comparing inhalational induction with sevoflurane and intravenous induction with propofol in elective patients undergoing general anesthesia was reviewed.
Karaaslan et al. compared whether propofol and sevoflurane with remifentanil without muscle relaxant would yield equivalent intubation conditions.
Methodology: A total of 80 patients of ASA I,II posted for elective surgery were randomly allocated into 2 groups. Patients were induced with sevoflurane 8 % in group 1 and propofol 1 mg/kg/min in group 2 was done until BIS was < 60. Intubation was done when BIS was
< 60. All patients received remifentanil infusion at a dose of
1 mcg/kg/min. Intubating conditions were assessed as optimal, good, marginal, poor using vocal cord opening, jaw relaxation and limb movement. The heart rate and mean arterial pressure were recorded before induction, during induction, and 1, 2 and 5 minutes following intubation. The duration of time for BIS to become <60 was recorded.
Results: Optimal intubating conditions were better in group II than in group I (90% versus 45%, p=0.002). The ratio of patients showing optimal or good intubating conditions was 80% in group I and 100% in group II (p=0.035). Time required for BIS to be <60 was shorter in group II than in group I (47.1±27.2 sec vs. 111.9±60.6 sec, p<0.001). There was a decrease in heart rate and mean arterial pressure when compared to baseline in both the groups.
Conclusion: They concluded that under BIS monitoring, propofol-remifentanil combination offered better intubation conditions and shorter induction period compared with sevoflurane-remifentanil.
(J Clin Exp Invest Vol 2, No 2, June 2011.)
Scheller et al. compared propofol at a dose of 2 mg/kg with different doses of alfentanil 30, 40, 50, or 60 µg/kg for tracheal intubation without muscle relaxant to evaluate airway and the intubating conditions.
Methodology: 75 patients with ASA physical status I or II with Mallampati grade I airway were chosen. Patients were randomized into 5 groups. There were 15 patients in each group.Patients in group I received d-tubocurare 3 mg,thiamylal 4 mg/kg and succinylcholine 1 mg/kg. Patients in groups II-V received propofol at a dose of 2 mg/kg with different doses of alfentanil 30, 40, 50, or 60 µg/kg. Muscle relaxant was avoided in groups II-V. jaw mobility,ease of ventilation were recorded. 90 seconds after induction, laryngoscopy was done and the glottic exposure and the vocal cord position were recorded. Patient response was noted after intubation. Heart rate and arterial blood pressure were recorded before and after induction, and after intubation of the trachea.
Results: Ease of ventilation was good and jaw was relaxed in all the patients. 5 patients in group II(30 µg/kg) couldn't be intubated because of poor exposure or closure of vocal cords. In all other groups, position of vocal cord was significantly favorable for intubation compared with group II. Heart rate and arterial blood pressure had a significant decrease after induction compared with preinduction values. But there were no difference between the alfentanil groups. Patients in group I had significant increase in heart rate after induction compared with preinduction values. Patients in group I had significant rise in mean arterial pressure after laryngoscopy and intubation compared with postinduction values.
Conclusion: They concluded that patients receiving propofol for induction and alfentanil(>30 µg/kg),mask ventilation,jaw mobility, vocal cord position and exposure during laryngoscopy and patient response to intubation differs minimally compared with thiamylal and succinylcholine.( Anesth Analg 1992; 75; 788-793.)
Grant et al. assessed the intubating conditions in adults after induction with propofol and varying doses of remifentanil.
Methodology: 60 patients of ASA physical status I or II were randomized into 3 groups. They assessed the intubating conditions in three groups after induction of anaesthesia with propofol 2 mg/kg and remifentanil 0.5, 1.0 or 2.0 µg/kg. Ease of laryngoscopy, jaw relaxation, coughing, position of vocal cords and limb movement were assessed.
Results: Success rate of intubation was 80%, 90% and 100% with remifentanil 0.5, 1.0 or 2.0 µg/kg respectively. Acceptable intubating conditions was present in 20%, 50% and 80% of patients. All three groups had a decrease in arterial blood pressure after induction but there was no difference between groups. They concluded that the intubating conditions were best after induction with propofol 2 mg/kg and remifentanil 2 µg/kg. (Br. J. Anaesth. (1998) 81(4): 540-543 )
Sivalingam et al. compared the intubating conditions and the hemodynamic changes following sevoflurane nitrous oxide induction in 3 different doses of alfentanil with low-dose alfentanil and suxamethonium.
Methodology: Patients were randomly allocated into 4 groups. They assessed the intubating conditions after inducing the patient with vital capacity breaths of sevoflurane 8% and 60 % nitrous oxide in 4 groups receiving alfentanil of 20, 25, 30 µg/kg and alfentanil 10 µg/kg and succinylcholine 1 mg/kg.
Results : Intubating conditions were satisfactory or excellent in 83%, 80%, 92% and 96% of patients in groups with alfentanil 20, 25, 30 µg/kg and alfentanil 10 µg/kg and succinylcholine 1 mg/kg respectively. Laryngoscopy and tracheal intubation induced increase in heart rate significantly decreased in all groups. Mean arterial pressure decreased significantly after induction in all groups. Mean arterial pressure increased significantly after 2 minutes after intubation compared with post induction value in alfentanil with succinylcholine group. They concluded that the intubating conditions obtained with sevoflurane plus alfentanil 30 µg/kg were comparable to those provided by the sevoflurane, alfentanil 10 µg/kg and suxamethonium combination. (Anaesth Intensive Care. 2001 Aug;29(4):383-7)
Katoh et al. aimed at determining the effect of fentanyl administration before tracheal intubation on the MAC-TI of sevoflurane.
Methodology : 80 patients of ASA physical status I were randomly allocated into 4 fentanyl groups - 0, 1, 2 ,4 µg/kg. This study was done to determine whether fentanyl would affect sevoflurane requirement for achieving 50% probability of nil movement in response to laryngoscopy and intubation (MAC-TI). All the patients were induced with sevoflurane at a pre-selected end-tidal concentration according to dixon's up and down technique. Fentanyl was administered after steady state sevoflurane concentration had been maintained for at least 10 min and tracheal intubation was done
4 min after administration of fentanyl, and patients were assessed for movement. Heart rate (HR) and mean arterial pressure (MAP) were recorded before induction, fentanyl administration, laryngoscopy and after intubation.
Results: There was no significant difference in the sevoflurane requirement between fentanyl 2 and 4 µg/kg showing a ceiling effect. The MAC-TI of sevoflurane in this study was 3.55% (95% confidence intervals 3.32-3.78%), and this was reduced to 2.07%, 1.45% and 1.37% by addition of fentanyl 1, 2 and 4 µg/kg. Fentanyl attenuated heart rate and mean arterial pressure due to intubation in a dose dependent manner even with decreasing concomitant sevoflurane concentration. Fentanyl 4 µg/kg attenuated the hemodynamic changes(HR and MAP) more effectively than fentanyl 1 or 2 µg/kg at sevoflurane concentrations close to MAC-TI. (Br J Anaesth. 1999 Apr;82(4):561-5.)
Kimura et al. aimed at determining the concentration of sevoflurane required for tracheal intubation(MAC-EI) and MAC in adults.
Methodology: 86 elective patients of ASA physical status I and II were selected. After maintaining the pre-selected end tidal concentration of sevoflurane for 20 min, intubation was done without muscle relaxant for MAC-EI determination. Pre-determined concentration sevoflurane at which intubation was done was - 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%, and 7.0%. After maintaining the pre-selected end tidal concentration of sevoflurane for 20 min, skin incision was attempted. Pre-determined concentration sevoflurane at which skin incision was attempted was 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, and 3.0%.
Results: They determined the MAC-EI of sevoflurane to be 4.52% (95% confidence limits, 3.91%-5.21%), and the ED95 for tracheal intubation was 8.07%. The MAC of sevoflurane was 1.58% (95% confidence limits, 1.14%-1.98%), and the AD95 (anesthetic ED95) was 2.96%. The MACEI/MAC ratio was 2.86 (95% confidence limits, 2.63-3.43). They concluded that induction followed by tracheal intubation without muscle relaxant can be accomplished in adults when sevoflurane is given as a single anesthetic but in excess of 8% end-tidal concentration. (Anesth Analg August 1994 79:378-381.)
Van Twest et al. assessed the effectiveness of bispectral index monitoring as a guide to the time of intubation during sevoflurane induction without the use of neuromuscular blocking agents in adults, and if a target BIS value of 25 provides better intubating conditions than a target BIS of 40.
Methodology: 40 patients were randomized into two groups, a target BIS 25 or a target BIS 40. Patients were premedicated with midazolam 20 µg/kg, fentanyl 0.5 µg/kg. Induction with Sevoflurane was initiated and titrated to reach the target BIS value and maintained within the target range for two minutes. The trachea was intubated and the intubating conditions were assessed.
Results: The BIS 25 group had a superior median intubating score of 4 (range 3-9) compared with the BIS 40 group with a median of 7 (5-10, [6-9], P<0.001). The time to reach target BIS values was not statistically different (BIS 25 group - 6.6 min, BIS 40 group - 5.1 min, P=0.054). End-tidal sevoflurane concentration upon reaching the target BIS was higher in the BIS 25 group (5.3% +/- 1.2%) vs the BIS 40 group (3.5% +/- 0.95) (P<0.001). There was no statistical difference in the heart rate and arterial blood pressure between the 2 groups. They concluded that target BIS value of 25 provides better intubating conditions than target BIS of 40 during induction with sevoflurane without neuromuscular blocking agents. (Anaesth Intensive Care. 2006 Oct;34(5):606-12.)
Taha et al. compared the intubating conditions and hemodynamic changes following induction and tracheal intubation in patients receiving either propofol - lidocaine - remifentanil or thiopental-lidocaine-remifentanil.
Methodology : 76 healthy adult patients were assigned into two groups: group P received and propofol 2 mg/kg, lidocaine 1.5 mg/kg, remifentanil 2 μg/kg or group T received thiopental 5 mg/kg, lidocaine 1.5 mg/kg, remifentanil 2 μg/kg. Laryngoscopy and intubation was done 90 seconds after administration of the hypnotic agent. Intubating conditions were assessed as excellent, good or poor on the basis of jaw relaxation, ease of ventilation, position of the vocal cords, and patient's response to intubation and inflation of the tracheal cuff. Heart rate and mean arterial pressure was measured 45 seconds after induction, after intubation, 2 and 5 min after intubation.
Results: Intubating conditions were excellent in 84% of Group P patients and 50% of Group T patients which was statistically significant. The decrease in mean arterial pressure from baseline to post induction was significantly higher in group P than in group T (27.4% ± 11.6 vs 21.8% ± 10.0) and from baseline to post intubation in group P and group T were also statistically significant
(19.0% ± 16.7 vs 11.2% ± 14.9). The percentage change from baseline HR was significantly higher in Group P than in Group T after induction (13.8% ± 9.7 vs 0.5% ± 12.4), postintubation (8.7% ± 13.7 vs 2.1% ± 13.1), and two minutes after intubation (7.04% ± 14.3 vs
3.5% ± 14.3).
Conclusion: They concluded that propofol-Lidocaine-remifentanil was superior to thiopental- lidocaine- remifentanil for tracheal intubation without muscle relaxants. However, it induces more hypotension and bradycardia. (Can J Anaesth. 2005 Mar;52(3):249-53.)
Stevens et al. compared different doses of remifentanil with propofol induction for tracheal intubation without neuromuscular relaxants. Methodology: 80 premedicated outpatients belonging to ASA I and II were randomly assigned into four groups. Remifentanil 1, 2, 3, or 4 µg/kg was infused intravenously over 90 seconds in group I -IV. after 60 seconds after remifentanil infusion was started, Propofol at a dose of 2 mg/kg over 5 seconds was given. Laryngoscopy and tracheal intubation were assessed 90 seconds after administration of propofol. Clinically acceptable intubating conditions was defined when jaw was relaxed, vocal cords open, and fewer than two coughs in response to intubation were observed. This was seen in 35%, 75%, 100%, and 95% of patients in Groups I-IV, respectively. Clinically acceptable intubating conditions were significantly less in Group I compared with other groups. Excellent intubating conditions were observed in 30%, 50%, 80%, 80% of patients in Groups I-IV, respectively. Overall intubating conditions were significantly better in Groups III and IV compared with Groups I and II. The mean time for resuming to spontaneous ventilation after induction was < 5 min in all groups. The percentage of decrease in mean arterial pressure was 16%, 20%, 28%, 26% immediately before tracheal intubation in Groups I-IV, respectively. They concluded that premedicated healthy patients with favorable airway anatomy can be reliably intubated with good or excellent conditions 90 s after the administration of propofol 2 mg/kg and remifentanil 3-4 µg/kg. Remifentanil 3 µg/kg and propofol
2 mg/kg co-administered intravenously may provide adequate conditions for tracheal intubation without neuromuscular blocking agents. This combination allows the rapid return of spontaneous ventilation.(Anesth Analg 1998; 86: 45-9.)
Thwaites et al. compared sevoflurane versus propofol and succinylcholine for tracheal intubation in children. 64 healthy children aged 3-10 yr undergoing adenotonsillectomy were randomized. Induction was done using either 8% sevoflurane in nitrous oxide or propofol 3-4 mg/kg with succinylcholine 2 mg/kg and intubation was performed 150 seconds after induction. Intubating conditions were scored using Krieg and Copenhagen Consensus Conference (CCC) scores. The trachea was successfully intubated at the first attempt in all patients under clinically acceptable conditions but the scores were significantly better with propofol and succinylcholine. (Br J Anaesth. 1999 Sep;83(3):410-4.)
Tsuda et al. evaluated tracheal intubation without muscle relaxant with propofol and different doses of fentanyl. 55 adults posted for elective surgery were randomly assigned to one of four groups to receive fentanyl 0, 2, 3, or 4 µg/kg respectively. 3 minutes after fentanyl administration, propofol at a dose of 2 mg/kg was given for induction. After the loss of consciousness, supplementation with topical lidocaine at a dose of 2 mg/kg was done after which laryngoscopy and tracheal intubation were attempted. Patients without administration of fentanyl had poor intubating conditions. The incidence of movement and persistent coughing with laryngoscopy and intubation were reduced with increasing doses of fentanyl. Visualization of the vocal cord was more likely to be impossible in patients in fentanyl 4 µg/kg group (40%) compared with patients in fentanyl 2 µg/kg group (7%). There were no significant differences among groups receiving different doses of fentanyl with respect to position of vocal cords . The vocal cords were closed in 26% of patients receiving fentanyl and propofol for intubation. (Masui. 2001 Oct;50(10):1129-32.)
Bonnin et al. compared target controlled infusion of propofol and sevoflurane for fiberoptic intubation under spontaneous ventilation.
Methodology: 52 patients belonging to ASA I-II were randomly assigned to one of two groups. Patients were pre-oxygenated for 3 min and they received either sevoflurane 4% with tidal volume ventilation or propofol infusion with a plasma target concentration of 4 mg/l. After 2 min, sevoflurane was increased by 1% every 2 min and propofol infusion was increased by 1 mg/l until there was no reaction during mandibular movement. This concentration was maintained for 4 min before starting nasotracheal fiberoptic intubation. Pulse oximetry, heart rate, arterial blood pressure,bispectral index(BIS) were monitored during induction and fiberscopy. Intubation quality of and operator satisfaction were evaluated.
Results: There was no difference in BIS values or pulse oximetry during or at the end of induction. Desaturation under 90 % occurred 5 times during fibreoptic intubation in propofol group and none with sevoflurane group. They concluded that sevoflurane provides good intubating conditions in patients undergoing fiberoptic intubation in
spontaneously breathing patients without any hypoxemic episodes such as those observed with propofol. ( Acta Anaesthesiol Scand. 2007 Jan;51(1):54-9.)
Striebel et al. compared the intubation conditions using propofol and fentanyl without muscle relaxant with the combination of propofol, fentanyl ,succinylcholine and sodium thiopental/succinylcholine.
Methodology : 100 patients of ASA physical status I and II undergoing gynecological surgery were randomized into 4 groups - Group 1 received 100 µg/kg fentanyl, 1 mg vecuronium, sodium thiopental (demand-adapted) and succinylcholine 1 mg/kg; group 2 received 100 µg/kg fentanyl and propofol (demand-adapted); group 3 received 200 µg/kg fentanyl and propofol (demand-adapted); group 4 received 100 µg/kg fentanyl, 1 mg vecuronium, propofol (demand-adapted) and succinylcholine 1 mg/kg. Jaw relaxation, glottis visualization, position and movement of vocal cords and patient movement were assessed. The overall assessment of the intubation was graded (grade I-IV) by the anaesthetist. Postoperatively the patients were asked regarding muscle pain (grade I-IV). Before, during and after endotracheal intubation, heart rate, arterial blood pressure and arterial haemoglobin oxygen saturation were monitored. Results: Group 1 required an average of 5.5 ± 1.2 mg/kg sodium thiopental. There were no significant differences in group 2, 3 and 4 with respect to the dose of propofol (2.4, 2.2 and 2.2 mg/kg). There was no difference with regard to jaw relaxation, laryngoscopic visualization of the glottis and patients' movements during intubation between the groups. Statistically significant difference occurred with regard to the position and movement of vocal cords during intubation (group 3 was worse than groups 1, 2, 4) and the patient movement 1 min after intubation (group 2 was worse than group 3). Overall assessment of intubation was worse in group 3 than group 2,4 which was statistically significant and the postoperative muscle pain (group 1 worse than groups 2, 3). They concluded that the use of 100 µg/kg fentanyl, sodium thiopental, succinylcholine results in no better intubating conditions than 100 µg/kg fentanyl plus propofol.
( Anaesthesist. 1995 Dec;44(12):809-17.)
Gore et al. evaluated clinically acceptable intubating conditions with different doses of propofol without muscle relaxants.
Methodology: 90 patients of ASA grade I and II patients posted for elective surgery were randomly allocated into group I propofol
2 mg/kg, group II 2.5 mg/kg, group III 3mg/kg. After premedicating the patient with fentanyl and midazolam and 5 minutes thereafter, induction dose of propofol was given followed by inj.lignocaine 90 seconds prior to intubation. Intubating conditions were assessed and hemodynamic changes were recorded at various levels.
Results: Ideal intubating conditions were obtained in 96.7% of patients in propofol 2.5 mg/kg group and 100% in propofol 3 mg/kg group. They identified that clinically acceptable intubating conditions could be achieved with propofol at a dose of 2.5 mg/kg and 3 mg/kg without significant hemodynamic changes and 100% success could be obtained with 3 mg/kg of propofol. They concluded that ideal intubating conditions without neuromuscular blocking agents could be achieved with propofol 3 mg/kg, fentanyl 2 µg/kg and lignocaine 1.5 mg/kg without significant hemodynamic changes.( J Anaesth Clin Pharmacol 2011;27:27-30.)
Mansoor et al. evaluated different doses of fentanyl on intubating conditions with sevoflurane inhalation without neuromuscular blocking agents in adults. 56 adult patients of ASA physical status I and II were randomly assigned into 2 groups. After priming the breathing circuit with sevoflurane 8 % in 50 % nitrous oxide with total fresh gas flow of 8 L/min, anesthesia was induced using the three breath vital capacity technique. Patients in Group-I received 2 µg/kg and Group- II patients received 3 µg/kg of fentanyl 1 min after inhalational induction. Laryngoscopy was performed 4 minutes after start of inhalational induction. Jaw relaxation, vocal cord opening, coughing and patient movement were assessed. Heart rate, arterial blood pressure, Et- CO2, Et sevoflurane concentration, time to loss of consciousness and successful tracheal intubation were measured.
Results: Optimal intubation conditions were higher in Group-II (89% vs 54%) and both groups had a high incidence of good to optimal intubating conditions (Group-I 89% and Group-II 100%). Mean time to loss of consciousness was 47 sec in Group-I and 46 sec in Group-II and successful tracheal intubation was similar at 32 sec for Group-I and 31 sec for Group-II.None of the patient in either group coughed or moved during laryngoscopy. The incidence of hypotension during induction was 7% in each group. They concluded that 8% sevoflurane in 50% N2O - oxygen mixture with 3 µg/kg fentanyl provide optimal intubating condition in four minutes.
Ko et al. aimed at determining the optimal time of injection of fentanyl during induction of anesthesia to attenuate hemodynamic response to laryngoscopy and tracheal intubation.
Methodology: 150 patients were randomly allocated into 5 groups. group I was the control group in which the patient was not given fentanyl. Groups II - V received fentanyl at a dose of 2 µg/kg 1, 3, 5, or 10 min before tracheal intubation, respectively.
Results: Blood pressures were not increased in Groups III and IV, except for diastolic pressure in Group III, significantly after intubation compared with preinduction values. Groups I, II, V showed significant increase in arterial blood pressure. Systolic, diastolic, and mean arterial pressure 1 min after intubation in Groups III and IV were less than those in the control group. Heart rate increase in group IV was significantly less compared to the control group but there significant differences were not observed in Groups II, III, and V. The number of patients with dysrhythmia and tachycardia was significantly lesser in Group IV than in the control group. They concluded that the optimal time of injecting fentanyl to attenuate hemodynamic response to laryngoscopy and tracheal intubation is 5 min before tracheal intubation. (Anesth Analg 1998; 86: 658-61)