Anesth Analg 2000;91:1555-1559
© 2000 International Anesthesia Research Society
TECHNICAL COMMUNICATION
The SiBITM Connector: A New Medical Device to Facilitate Preoxygenation and Reduce Waste Anesthetic Gases During Inhaled Induction with Sevoflurane
Marie-José Colas, MD, FRCPC,
Jean-Pierre Tétrault, MD, MSc, FRCPC,
Lynne Dumais, MD,
Patrick Truong, MD,
Yves Claprood, MD, FRCPC, and
René Martin, MD, FRCPC
Department of Anesthesiology, University of Sherbrooke, Sherbrooke, Quebec, Canada
Address correspondence and reprint requests to M.-J. Colas, MD, FRCPC, Department of Anesthesiology, Centre Hospitalier Universitaire de Sherbrooke, 3001 12e ave. Nord, Fleurimont, Quebec, Canada, J1H 5N4. Address e-mail to mjcolas{at}courrier.usherb.ca
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Abstract
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Implications: The SiBITM connector is a new medical device used for vital capacity inhaled induction with sevoflurane. It allows efficient preoxygenation of patients and reduces waste anesthetic gases in the operation room during induction.
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Introduction
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During vital capacity induction (VCI) with sevoflurane, the anesthesia circuit normally used to facilitate preoxygenation is no longer available because it is being primed with anesthetic gases to allow a rapid inhaled induction (1). Furthermore, during inhaled induction, momentary breaking closure of the circuit, which contains large concentrations of anesthetic gases, leads to gas leaks into the operating room (OR) (2–4). The SiBI connectorTM, manufactured by Ventitech Medical Devices (Sherbrooke, Quebec, Canada) (patent pending; the device is authorized for distribution in Canada and the United States; it will soon be commercially available), is a new medical device that facilitates preoxygenation and reduces waste anesthetic gases in the OR.
The SiBI connector (Single Breath Induction) is comparable to a 3-way stopcock that swivels between the preoxygenation system and the anesthesia circuit. It must be installed between the distal end of the anesthetic circuit and the anesthesia mask. It replaces the usual 90° connector (Figure 1). Being a bidirectional airtight connector, it allows preoxygenation of the patient before VCI while the circuit is being simultaneously primed. Simply rotating the flow direction selector allows control of the source of gas flow delivered to the patient, O2 from the preoxygenation side (Position A: Figure 2A), or anesthetic gas from the anesthesia circuit (Position B: Figure 2B). The connector is small (dead space, 16 cm3), lightweight (30 g), transparent, latex- and lubricant-free, and reusable. The connector offers negligible resistance to airflow. On the preoxygenation side, there is an O2 vent that eliminates the risk of barotrauma. It is removable, thus reducing the size and weight of the connector to that of a simple 90° connector after the induction has taken place. We evaluated the efficiency of the connector to preoxygenate patients and reduce waste anesthetic gases during VCI.
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Figure 1. The SiBITM connector and accessories. The SIBITM connector is manufactured by Ventitech Medical Devices, Sherbrooke, Quebec, Canada.
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Figure 2. The SiBI connector (A) in "preoxygenation and priming position" and (B) in "induction and anesthesia maintenance" 1 = O2 tube, 2 = reservoir bag, 3 = O2 vent, 4 = anesthesia circuit, 5 = Luer lock tubing, 6 = flow direction selector. The SIBITM connector is manufactured by Ventitech Medical Devices, Sherbrooke, Quebec, Canada.
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Technical Evaluation
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After approval by our IRB, written, informed consent was obtained from ASA physical status I or II patients who were scheduled for anesthesia during elective surgery. Patients who refused inhaled induction, were at risk of regurgitation, or had a history of malignant hyperthermia were excluded. By using a random table, patients were assigned to receive VCI in different groups depending on the study. Circle circuits were primed with 8% sevoflurane, N2O 5 L/min, and O2 3 L/min. Once the concentration of sevoflurane in the circuit was more than 5% (measured by using a DatexTM Capnomac Ultima [Helsinki, Finland] monitor), the circuit was considered ready and VCI was performed (1).
Preoxygenation Evaluation
The efficiency of preoxygenation with the SiBITM connector was assessed. We also evaluated trends in the PaO2 during VCI in patients who were or were not preoxygenated before VCI. Twenty patients were divided into two groups. The first group (n = 10) underwent VCI without preoxygenation, and the second group (n = 10) was preoxygenated by using the SiBITM connector. A secondary O2 source with a flow of 10 L/min and a 2-L reservoir bag was connected to the SiBITM. Preoxygenation was performed for 4 min by face mask. In both groups, arterial blood gases were obtained 4 min before the induction (PaO2 -4), immediately before the induction (PaO2 0), and 1, 2, and 3 min postinduction (PaO2 +1, +2, and +3). Arterial blood gases were analyzed with a Nova Stat Profile 5TM apparatus (Nova Biomedical, Waltham, MA).
Waste Anesthetic Gases Evaluation
The efficiency of the connector to reduce waste anesthetic gases during VCI was evaluated. Forty-two patients, different from those participating in the preoxygenation evaluation, received VCI in one of two groups (21 patients per group). The first group underwent induction without the SiBITM connector, and the device was used in the second group. In the group without SiBITM, during the anesthetic circuit priming, complete occlusion of the distal end of the circuit was performed manually to prevent gas leakage. At the beginning of VCI, the anesthesia provider quickly connected an anesthesia mask to the circuit and applied it rapidly to the patient’s face. In patients undergoing induction with the SiBITM connector, occlusion of the anesthesia circuit was provided by the connector in Position A (Figure 2A). For VCI, the flow direction selector was then turned to Position B (Figure 2B). In both groups, the plane of anesthesia was deepened for endotracheal intubation by ventilating with 8% sevoflurane with inspiratory pressures <20 mm Hg. During intubation, the sevoflurane vaporizer was closed, but the N2O and O2 flowmeters remained opened. In the SiBITM group, during that time, the flow direction selector was turned to Position A to eliminate gas leaks. To quantify gas leakage in both groups, N2O and sevoflurane concentrations in the OR were measured by using a spectrophotometer, according to established guidelines (5). Gas sampling was done at a vertical distance of 30 cm from the patient’s nose. Measurements were at 15-s intervals, beginning with priming and throughout the VCI, until 5 min postintubation. We focused our analysis on a timeframe of 8 min during VCI because this corresponds to the period of maximal anesthetic gas leaks (2–4). The OR had 15 exchanges/h with fresh air.
Continuous data were analyzed by using a paired t-test for comparison between groups; Wilcoxon and Mann-Whitney tests were used for nonparametric data. For the waste anesthetic gases evaluation, the area under the curve, for measured concentration of N2O and sevoflurane in relation to time, was evaluated by using the Mathcad 3.1 program developed by Mathsoft Inc. (Cambridge, MA). The alpha error was set at 0.05.
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Results
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Preoxygenation Evaluation
No differences were found between groups with regard to demographic data or gases in the anesthetic circuit at the end of priming (Table 1 ). Median PaCO2 values were similar in both groups (Table 2 ). The median PaO2 versus time during VCI for patients nonpreoxygenated and those preoxygenated with the SiBITM connector are shown in Figure 3.
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Figure 3. Median PaO2 (mm Hg) versus time (min) in relation to the induction with a mean fraction of inspired oxygen of 36%. Time 0 is just before the induction.  = the additional safety margin. The SIBITM connector is manufactured by Ventitech Medical Devices, Sherbrooke, Quebec, Canada.
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Waste Anesthetic Gases Evaluation
Four patients, one in the group without and three in the group with the SiBITM were excluded for various reasons: one had a mask that was too large, and three had gas leaks (one from the circuit and two from the scavenging system). No differences were found between the two groups with regard to demographic data, gases in the anesthetic circuit at end of priming, time to loss of lash reflex, and time to intubation (Table 1). The N2O and sevoflurane median values in ppm, obtained from all patients in their respective groups during the 8-min timeframe were shown in a graph (Figure 4). We calculated the area under the curve for both groups and found that the exposure of anesthesia provider to N2O and sevoflurane during the induction was decreased by 750% (537.5/71.5 ppm) and 740% (40.0/5.4 ppm), respectively, when the SiBITM connector was used (P < 0.001).
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Figure 4. Mean operating room concentration of (A) N2O (ppm) and (B) sevoflurane (ppm) versus time (min) during vital capacity inhaled induction. *AUC = area under the curve. **NIOSH Threshold-National Institute for Occupational Safety and Health current threshold values for N2O and sevoflurane (ppm) as time-weighted average. The SIBITM connector is manufactured by Ventitech Medical Devices, Sherbrooke, Quebec, Canada.
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Discussion
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The preoxygenation evaluation demonstrated that the SiBITM connector provides an efficient way to preoxygenate patients by obtaining median PaO2 values comparable to that obtained when the anesthesia circuit is used for preoxygenation before the IV induction (6). The importance of preoxygenation before the IV induction is widely accepted (7–10). Although we did not want to compare preoxygenation with the SiBITM connector with other modes of preoxygenation, we established that this new system yields PaO2 values higher than the ones obtained with other methods currently available before VCI, unless a reservoir mask is used (11,12).
The serial measurements of PaO2 allowed us to study trends in PaO2 during VCI. These trends demonstrate that, during VCI with an anesthetic gas mixture containing 57% N2O, nonpreoxygenated patients have a limited O2 reserve compared with preoxygenated patients. This leaves a smaller margin of security if an adverse respiratory event occurs during the induction (such as a "cannot ventilate" situation as a result of laryngospasm). In our evaluation, we used N2O during VCI to take advantage of its second gas effect (13–15). For those who choose to use an even larger concentration of N2O for VCI (1), it becomes even more desirable to preoxygenate patients. If a mixture of 100% O2 and sevoflurane is used for VCI, the benefit of preoxygenation remains to be demonstrated.
In the second study, we demonstrated that the SiBITM connector allows a significant reduction of waste anesthetic gases during VCI. This was predictable because it prevents the momentary breaking closure of the circuit, which produces gas leaks. There is some controversy regarding the possible health consequences of exposure to trace concentrations of OR gases (16–18). Even though the National Institute for Occupational Safety and Health limits were exceeded for only a short period of time during VCI without the connector, it is obviously desirable to minimize exposure of OR personnel to trace anesthetic gases (18).
In conclusion, the SiBI connector allows efficient preoxygenation of patients and reduces waste anesthetic gases in the OR during VCI.
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Acknowledgments
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Support was provided by departmental sources. August 22, 2000.
Acknowledgments to M. Pilote, RN, for data collection, N. Corriveau for secretarial work, and OR staff of the Sherbrooke University Hospital Center for their collaboration.
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Abstract
Introduction
