Is I-gel airway a better option to endotracheal tube airway for sevoflurane-fentanyl anesthesia during cardiac surgery?

BACKGROUND: Anesthetists used lower doses of fentanyl, successfully with hemodynamic control by titrating volatile anesthetic agents or vasodilators for fast-tracking in cardiac surgery. HYPOTHESIS: Lower total doses of anesthetics and fentanyl could be required with hemodynamic control by use of supraglottic devices than endotracheal tube (ETT) and helps in fast-tracking.
DESIGN: A prospective randomized observational clinical trial study. AIMS: The authors compared the utility of I-gel airway with a conventional ETT during the induction and maintenance of anesthesia with sevoflurane and fentanyl in adults undergoing cardiac surgery. PATIENTS AND METHODS: A total of 49 adult patients underwent cardiac surgery were randomized into two groups according to the airway management: I-gel group (n = 23) and ETT group (n = 26). Doses of fentanyl and hemodynamic parameters (heart rate [HR], mean arterial pressure [MAP] central venous pressure [CVP], pulmonary artery pressure [PAP], and pulmonary capillary wedge pressure [PCWP]) were recorded preoperative, 5 min following tracheal intubation or I-gel airway insertion, after skin incision, after stenotomy, and after weaning off bypass.
RESULTS: None of the patients in the I-gel group required additional doses of fentanyl during the I-gel insertion, compared with 74% of the patients during laryngoscopy and endotracheal insertion in the ETT group, for an average total dose of 22.6 ± 0.6 μg/kg. The MAP and HR did not significantly differ from the baseline values at any point of measurement in either group. Furthermore, CVP, PAP, and PCWP measured during the procedure were significantly lower in I-gel group than ETT group. Extubation required more amount of time in ETT than I- gel group.
CONCLUSION: The I-gel airway is well-tolerated by adult patients undergoing cardiac surgery, and requires lower total doses of anesthetics than endotracheal intubation with hemodynamic control and helps in fast-tracking.

RCT Entities:   Population Interventions Outcomes

INTRODUCTION

Laryngoscopy and endotracheal intubation produce reflex sympathetic stimulation and are associated with raised levels of plasma catecholamines, hypertension, tachycardia, myocardial ischemia, depression of myocardial contractility, ventricular arrhythmias, and intracranial hypertension.[12] However, recently developed airway devices may ensure hemodynamic stability, which is an essential requirement for patients undergoing cardiac surgery. The wide variety of airway devices available today may broadly be classified as intraglottic and extraglottic airway devices, which are employed to protect the airway in both elective as well as emergency situations.[3] I-gel is a single-use supraglottic airway device from Intersurgical, UK (Intersurgical Ltd., Wokingham, Berkshire, UK), anatomically designed to facilitate insertion, minimize tissue compression, maintain stability of position after placement and separate the gastrointestinal and respiratory tracts. An airway channel connected to a 15 mm port for ventilation and a gastric channel enabling access to and from the upper gastrointestinal tract and through which a gastric tube may be passed.[24]

Now-a-days cardiac surgery has faced a growing interest for fast extubation and early discharge from the intensive care unit (ICU) after the operation. While large doses of fentanyl (50-150 μg/kg) have been used to assure hemodynamic stability during cardiac surgery, they invariably tend to prolong mechanical ventilation in the ICU. Early extubation was first achieved with a propofol-based technique in 1996,[56] while in 1998, a combination of fentanyl and isoflurane was successfully used to achieve the same.[789] There are limited studies comparing differences in the circulatory responses to endotracheal intubation comparing to other supraglottic devices in cardiac patients and[1011] we cannot find previously published study on patients who undergoing coronary artery bypass graft (CABG) surgery with I-gel insertion.

In this randomized observational trial, we compared the efficacies of the I-gel airway and the endotracheal tube (ETT) at a fixed inspired concentration of sevoflurane (1.0-1.5 MAC) in order to reduce the induction dose of fentanyl, provide hemodynamic stability, and allow fast-tracking and early extubation or airway removal in adult patients undergoing cardiac surgery.

PATIENTS AND METHODS

This study was approved by the Ethics and Research Committee of the Department of Anesthesia, and written informed consent was obtained from all the study participants attending the Cardiothoracic Surgery Department.

A total of 55 patients underwent cardiac surgery involving cardiopulmonary bypass (CPB), 45 (40-55) years were screened from January 2008 to December 2009 and 49 were enrolled in the study based on the following inclusion criteria: Patients were American Society of Anesthesiologists physical status II, ejection fraction (EF) ≥40% and scheduled for elective cardiac surgery under general anesthesia. No difficulties with their airway management or intubation were predicted during preoperative visits according to Mallampati score classification.

Exclusion criteria were patients undergoing emergency surgery or those allergic to any of the drugs in the protocol, a history of reactive airway disease, gastroesophageal reflux, morbid obesity, heavy smoker, alcohol or opium addiction, which could be increase fentanyl use during the study due to increase tolerance. A total of six such cases were excluded from the study.

The patients taking their medications before surgery had similar protocol. All of them were taking metoprolol,nitrocontin, and aspirin [Table 1]. The patients were randomly allocated into the following two groups by the sealed envelopes method, the I-gel group and ETT group, on the airway management.

Table 1

Patient characteristics and demographic data (mean±SEM) ratio or number of patients

Peripheral arterial and venous cannulae were placed in all patients before induction; the blood pressure (BP) and heart rate (HR) recorded served as baseline observations for subsequent comparison. A Swan-Ganz catheter was inserted in all patients immediately after tracheal intubation or I-gel insertion, and cardiac output (CO) measurements were taken as the mean of three readings. In addition, electrocardiographs, central venous pressure (CVP), pulmonary capillary wedge pressure (PCWP), pulmonary artery pressure (PAP), pulse oximetry, end-tidal carbon dioxide, hourly urine output, and skin and rectal temperatures were continuously monitored in all patients.

Anesthesia was induced with thiopental (2 mg/kg) and 10 μg/kg of fentanyl. Muscle relaxation was achieved with 0.15 mg/kg of pancuronium. To ensure full muscle relaxation sevoflurane was administered through a facemask and the patients were manually ventilated for 3 min and increased gradually to reach an inspired concentration of 1.5 MAC in oxygen: Air (70:30) gas mixture and maintained until tracheal intubation or I-gel insertion. Extra doses of fentanyl were administered to maintain HR and BP, when affected by laryngoscopy or I-gel insertion, within 20% of the baseline value. Following induction and intubation, all patients were maintained on the same anesthetic protocol. Surgery was performed through a standard median sternotomy, using CPB with mild hypothermia (>33°C). Myocardial protection was achieved using antegrade crystalloid cardioplegia and topical cooling.

Fentanyl (3 μg/kg) was given at skin incision, sternotomy, and at the commencement of rewarming. Hemodynamics were maintained within 20% of baseline values, first by manipulating the sevoflurane concentration between 1.0 and 1.5 MAC, and then by giving an extra bolus of fentanyl (2 μg/kg). If these measures failed, nitroglycerine (as a vasodilator), phenylephrine (as a vasoconstrictor) or metoprolol (to control HR) was used. During CPB, anesthesia was maintained with propofol (2 mg/kg/h), midazolam (0.05 mg/kg), and pancuronium (2 mg).

Patients were transferred to a surgical ICU (SICD) and placed on a Siemens 900C (Siemens, Germany) ventilator. They were weaned off the ventilator using synchronized intermittent mandatory ventilation (SIMV) + pressure support (PS) mode of ventilation. Extubation or I-gel airway removal was undertaken if the patient was awake, cooperative, with no residual neuromuscular blockade stable hemodynamic and metabolic parameters, with oxygen saturation maintained at more than 95%, the arterial oxygen tension was more than 80 mm Hg on FiO2 of 0.4, the SIMV rate was 5 breaths/min, and the PS was 5 cm H2O.

Extubation or I-gel airway removal was delayed if the patient bled in excess of 200 mL/h, and manifested hemodynamic instability or an obvious neurological deficit. If long-term postoperative or positive end expiratory pressure ventilation is required the I-gel will have to be replaced by ET tube. Intra-aortic balloon pump was not considered a contraindication for extubation or I-gel airway removal. Time to extubation or I-gel airway removal was calculated from arrival to the SICD until tracheal extubation or I-gel airway removal.

Statistical analysis

Data were analyzed using IBM SPSS statistics 20.0 software. Independent t-test was used for comparison of the continuous variable between the two groups. Variables expressed as mean ± standard deviation then converted to standard errors of the mean. For repeated or continuous measurements, analysis of variance was used. P < 0.05 was considered as statistically significant.

RESULTS

Of the 49 patients included in our study, 36 patients underwent CABG, while 13 required valve replacement, 12 underwent mitral valve replacement, while one patient with chronic aortic dissection underwent aortic root replacement with re-implantation of the coronaries. Twenty-four patients were diabetic, with 9 having insulin-dependent diabetes mellitus (DM), and 15, noninsulin-dependent DM. Seven patients had suffered a myocardial infarction (MI) <2 weeks before surgery. Nine patients were hypertensive, 3 in I-gel group and 6 in the ETT group. Statistical analysis was performed in the remaining 49 patients who were randomly allocated into two groups, the I-gel group (n = 23) and ETT group (n = 26), based on the airway management.

Patient characteristics and demographics are summarized in Table 1. There were no significant differences between the groups with regard to age, body weight, left ventricular EF, type of surgical procedure, or incidence of diabetes, hypertension, or recent MI. The time to extubation was not significantly different among the two groups (4.1 and 3.9 h for the ETT group and I-gel airway group, respectively).

The patients in the ETT group required significantly more fentanyl as compared to those in the I-gel group (P < 0.05) [Table 1]. About 17 (74%) patients in the ETT group required extra doses of fentanyl in response to laryngoscopy and after tracheal intubation, while none of the patients in the I-gel group required additional doses of fentanyl after I-gel insertion. Following the skin incision, however, only two patients (8%) in the ETT group required extra doses of fentanyl as compared to none in I-gel group. No patient from any group required extra analgesia at sternotomy. The MAP and HR did not significantly differ from the baseline values at any point of measurement in either group. There were no significant differences in CO, cardiac index (CI), systemic vascular resistance (SVR), and pulmonary vascular resistance between the two groups at any point of measurement. Following intubation or I-gel airway insertion, the filling pressures, namely CVP, PCWP, and mean PAP (mPAP), were significantly lower in the I-gel airway group than in the ETT group (P < 0.05). These differences gradually disappeared over the study period [Tables 2 and 3].

Table 2

Haemodynamic data (mean±SEM)

Table 3

Derived hemodynamic data (mean±SEM)

DISCUSSION

The cardiovascular response to laryngoscopy and tracheal intubation has been extensively studied during the past 3 decades. The magnitude of the response is affected by many factors: The technique of laryngoscopy tracheal intubation,[4512] and the use of various airway instruments, like flexible fiberoptic bronchoscope and light wand intubating device.[510] Premedication and induction drugs may attenuate the circulatory response,[9] many drugs and techniques have been tried in an effort to attenuate adverse hemodynamic responses to laryngoscopy and endotracheal intubation.[13141516] A patient's medical condition affects his physiologic response. Such hemodynamic changes can result in myocardial ischemia, but seem to cause little harm to most patients. However, they are undesirable in patients with cardiac disease.[91117] On the contrary, in our study and with I-gel airway group the required total dose of fentanyl was lower than the total required dose reported in the previously published study with endotracheal intubation[9] and this when using the same combination of fentanyl in an induction dose of 10 μg/kg and sevoflurane in a fixed inspired concentration of 1.0-1.5 MAC. The study demonstrated also, that combination successfully provided hemodynamic stability during induction of anesthesia and allowed early extubation in adult patients undergoing cardiac surgery.

Our findings revealed that I-gel airway insertion was well-tolerated and efficacious when used under anesthesia induced by fentanyl (10 μg/kg) and 1.0-1.5 MAC of sevoflurane, with good hemodynamic stability in adult patients undergoing cardiac surgery. Furthermore, this approach required lower doses of anesthetics than the traditional endotracheal intubation, and the inspired concentration of sevoflurane was well-tolerated during the maintenance of anesthesia allowed fast-tracking and decreased mechanical ventilation in the ICU.

In our study, we observed that sevoflurane and I-gel airway insertion when used in combination with 10 μg/kg of fentanyl showed a reduction in MAP and CO, with a downward trend in mPAP in the pre bypass period in patients undergoing cardiac surgery. Furthermore, we observed a decrease in HR and MAP following anesthesia induction, I-gel airway insertion and during maintenance with sevoflurane. The filling pressures, including mPAP, also showed a downward trend before the onset of CPB, which was similar to previous results.[111819] Further, in adult patients undergoing carotid surgery with sevoflurane being used for the induction of anesthesia, the HR and MAP showed a more or less similar trend to that observed in our study.[20]

In fact, the safety of I-gel airway insertion and sevoflurane inhalation with respect to the frequency of myocardial ischemia and additional heart problems in known cardiac patients undergoing noncardiac surgery has been previously demonstrated.[421] In children undergoing cardiac surgery after insertion of the I-gel airway, the CI and HR were preserved, while MAP decreased at both 1.0 and 1.5 MAC of sevoflurane.[422]

In our study, the total dose of fentanyl required was significantly higher in the ETT group as compared with the I-gel group. This obvious difference, arising mainly because of the additional doses of fentanyl given in response to laryngoscopy, indicates that 10 μg/kg of fentanyl combined with 1.0-1.5 MAC sevoflurane may be too little to provide satisfactory intubation conditions in adult patients undergoing cardiac surgery.

Ueda et al. demonstrated that sevoflurane could safely regulate the perfusion pressure and maintain adequate SVR indices during CPB.[23] However, in this study, we did not use sevoflurane for maintenance of anesthesia during CPB, instead using propofol infusion. As sevoflurane and propofol have been shown to have comparable hemodynamic profiles,[724] we expect this to have only a minimal effect on the overall results. Furthermore, as regard to regurgitation or aspiration no cases were detect in our study. We believe as others[2252627] believed that the I-gel has features designed to separate the airway and gastrointestinal tracts and as such should offer some protection against aspiration. Protections that we have went to it during our study were exclusion patients undergoing emergency surgery, long period of fasting, selected patients with no history of gastroesophageal reflux, nonsmoker nonalcohol consumers and the supine position during operation.

When we investigated for the previous articles interested with regurgitation or aspiration with the I-gel airway, only two articles we could find the first presented three patients of regurgitation while using the I-gel supraglottic airway in more than 280 patients. In two elective cases, the I-gel completely protected the airway from aspiration and the research stated that one patient had no identifiable risk factors for regurgitation and one patient reported mild, infrequent reflux symptoms, but had no other risk factors. There was no evidence of aspiration clinically or on fiberoptic inspection of the interior of the I-gel and of the laryngeal inlet. Both patients recovered from anesthesia without complications. In one patient who consumes alcohol occasionally, aspiration occurred during the use of the I-gel in a study to determine ease of use when used by nonanesthetists, it did not provide complete protection.[2] The second was an article reported a case of gastric aspiration in a young male with a preoperative 6 h only of fasting and undergoing left lateral position for surgical access.[27] This investigations agreed with our scope of the results of the study that I-gel airway can be recommended for patients at low risk of aspiration and high risk of critical events during induction. However, the efficacy of these features has not been confirmed, and further study is required to determine the safety profile of the device.

In our study, the technique of airway management by I-gel airway decreased the concomitant use of the intravenous opioid, which is classically considered one of the main steps in a fast-track process,[28] and different anesthesia protocols have been proposed to achieve this goal. In 1990s, the common procedure for fast-track cardiac anesthesia included a limited intravenous opioid dose with the concomitant use of volatile anesthetics or propofol, or both.[520]

Many authors estimated prolonged CPB, postoperative low CO or shock, prolonged vasopressor therapy, and elevated preoperative systemic venous pressure may be from the main causes of gastrointestinal complications after cardiac surgery they emphasized the gastrointestinal complications were remote and not sharing in regurgitation or aspiration and they did not mention in their researches to the airway management and their relation to regurgitation or aspiration.[29303132] The results demonstrated by Cheng et al. as regard to time to extubation (4.1 h)[5] were agreed with our results which showed that the application of fast-track cardiac anesthesia resulted in a decreased intubation time in patients undergone CABG surgery. Subsequently, and based on this fact our study prove that the I-gel airway allow fast-tracking and early airway removal in adult patients undergoing cardiac surgery (3.9 h) due to decreased the total dose of fentanyl used. The previous results together with our collected data as regard to the filling pressures, namely CVP, PCWP, and mPAP, which were significantly lower in the I-gel airway group than in the ETT group (P < 0.05), may share in decreasing the gastrointestinal complications after cardiac surgery.

We conclude that the I-gel airway was well-tolerated, efficacious, and allowed rapid airway removal when used under anesthesia induced by 10 μg/kg of fentanyl in combination with sevoflurane at 1.0-1.5 MAC, with hemodynamic stability superior to that provided by the conventional ETT in adult patients undergoing cardiac surgery and in view of this it is now fair to replace gold standard of cuffed ETT, which provides full proof effect against aspiration by the I-gel airway. However, regardless of our findings about the airway management with I-gel airway and even if it is generally accepted that early airway removal is one of the main determinants of early discharge from the ICU after cardiac surgery, there is still an open debate about the optimal extubation time after cardiac operations.[5333435] We see that our work is important in preventing sympathetic responses at a lower dose of opioids and helpful in fast-tracking.

However, from the cardiac anesthesia point, there is a serious deficiency in our technique of anesthesia using I-gel in place of ETT. In our technique, using I-gel, there is no room for inserting a transesophageal echocardiography (TEE) probe for the evaluation of myocardial function or paravalvular leak, if required. In the present day, practice of cardiac anesthesia perioperative use of TEE is standard of care and any anesthesia technique, which does not provide a possibility of putting a TEE probe, if required, is not acceptable for patients undergoing cardiac surgery.[3637] We believe our work may be important for noncardiac surgery in cardiac patients or patients undergoing cardiac surgery, but not in need for TEE monitoring.

Our study has important limitations. First limitation is small sample size. The study included only 49 participants who fulfilled all the inclusion criteria and had undergone cardiac surgery. The sample size was restricted to 49 cases because of logistical reasons; we could only schedule one surgery per week. Moreover, the study drugs and devices were provided free of cost to all the study participants, limiting the inclusion of more cases. Second, our results are specific to patients with no history of reactive airway disease or morbid obesity with unforeseeable occurrence of increased in airway pressure, bronchospasm or pulmonary edema. Insertions were done in patients with normal airway for easy repositioning of the I-gel in the postoperative period for needed cases. Third, nonblind study because the great differences between I-gel and ETT in the shape, it was the need to cover the face of our patients and this was difficult in such risky patients. Fourth,the lack of baseline CO and filling pressures values; however, as HR and BP were preserved during the peri-induction period, we assumed that there were no significant changes in those parameters from the baseline.