The midazolam and fentanyl versus additional use of propofol in difficult-to-sedate cases during bronchoscopy by transcutaneous gas monitoring: a case control study

doi:10.21203/rs.3.rs-2438541/v1

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The midazolam and fentanyl versus additional use of propofol in difficult-to-sedate cases during bronchoscopy by transcutaneous gas monitoring: a case control study

https://doi.org/10.21203/rs.3.rs-2438541/v1

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Background: bronchoscopy is a relatively invasive procedure, and standard anesthesia is often inadequate. The recently introduced transcutaneous carbon dioxide (tcpCO₂) monitoring has become a convenient surrogate method for continuous monitoring of the partial pressure of arterial carbon dioxide (PaCO₂). The objective of this study was to evaluate the safety of additional use of propofol during bronchoscopy by transcutaneous blood gas monitoring.

Methods: patients in whom transcutaneous gas monitoring was performed during bronchoscopy were included in this study. The study subjects were divided into two groups: 1) the midazolam + fentanyl group (MF group), and 2) the group in which midazolam was switched to propofol because of inadequate sedation with midazolam + fentanyl (MFP group). We conducted a retrospective analysis of the transcutaneous gas measurement data obtained during bronchoscopy.

Results: data of a total of 61 patients (MF group, n=41; MFP group, n=20) were analyzed. The duration over which the tcpCO₂remained over 50 mm Hg was longer in the MFP group (MF 0.0 min vs. MFP 7.8 min, p=0.042). The percentage of patients in whom the tcpCO₂rose to over 50 mm Hg was also higher in the MFP group (MF group, 14.6% vs. MFP group, 65.0%). None of the patients required discontinuation of the bronchoscopic procedure due to inadequate sedation. Conclusions: while the addition of propofol improved the tolerability of the procedure in difficult-to-sedate patients, it was also associated with a higher risk of ventilatory failure and hypoxemia. Thus, in order to ensure safety, additional propofol should be used with caution under continuous pCO₂ monitoring, such as by transcutaneous measurement.

Trial registration: this study was conducted with the approval of the Clinical Research Management Division of Dokkyo Medical University (Approval No.: R-15-5J) under the supervision of a well-trained bronchoscopist. The contents of the study were disclosed in an opt-out format.

transcutaneous gas monitoring

transcutaneous carbon dioxide monitoring

bronchoscopy

propofol

difficult-to-sedate cases

Bronchoscopy is a widely used procedure for diagnosis and treatment of various respiratory diseases, including lung cancer, interstitial pneumonia, and bronchial asthma. Although it is a highly useful tool, it is a relatively invasive procedure as the bronchoscope has to be inserted into the respiratory tract via the larynx, and anesthesia for sedation, or even analgesia, is required in most cases [1]. In the early days of bronchoscopy, sedatives were rarely used due to concerns about adverse events, and no differences in the complication rates/diagnosis rates were reported between patients who did/did not receive sedation [1, 2]. However, none of these studies took into account patient distress during the examination, despite bronchoscopy without sedation being a rather invasive procedure [2, 3]. Even when sedatives and analgesics are used, they prove inadequate in some cases, and the procedure needs to be terminated due to patient distress. In recent years, more importance has been placed on patient satisfaction with bronchoscopy, and use of anesthesia for the examination has become the standard for all patients [4, 5].

Thus, for satisfactory performance of bronchoscopy, practitioners require not only good bronchoscopy skills, but also ensure adequate sedation of the patient. While sedation by an anesthesiologist would be desirable, it is not always practical due to cost and personnel issues, and in most cases in Japan, anesthesia management during bronchoscopy is performed by a physician other than an anesthesiologist, most often the treating physician. Midazolam is the most frequently used drugs for sedation during bronchoscopy [6]. In recent years, opioids have also come to be commonly administered in addition to sedatives to decrease the cough reflex, reduce the amount of lidocaine needed for use as a local anesthetic, and improve the tolerability of the procedure [1]. Based on some previous reports, we also began to perform bronchoscopy using the combination of midazolam + fentanyl as sedation for routine examinations at our institution. However, these drugs alone sometimes do not provide a sufficient depth of sedation, interfering with continuation of the procedure to completion. In such cases, at our facility, we switch from midazolam to propofol to obtain good sedation and complete the examination.

Concerning the use of propofol, the British Thoracic Society guidelines state that since the therapeutic window of the drug is narrow and there is a high risk of over-sedation, the drug should be administered by those with advanced training and its use by non-specialists is not recommended [7, 8]. The American Society of Anesthesiologists’ guidelines for sedation and analgesia by non-anesthesiologists state that pulse oximetry monitoring alone during anesthesia is not sufficient to accurately assess a patient’s respiratory status and that additional monitoring of end-tidal exhaled carbon dioxide (EtCO₂) for assessing the ventilatory status is recommended [9].

While EtCO₂ monitoring is recommended, there are some concerns about its measurement during bronchoscopy. It is challenging to stably measure the EtCO₂ during bronchoscopy due to the cough reflex, and depending on the device, a closed-circuit needs to be prepared. Hence, the versatility of EtCO₂ measurement during bronchoscopy is not adequate. In recent years, transcutaneous gas measurement has become widely available, making it possible to easily assess transcutaneous carbon dioxide (tcpCO₂) which is known to be correlated with the partial pressure of carbon dioxide (pCO₂) [10]. Previous studies have reported the usefulness of transcutaneous blood gas measurement during gastrointestinal endoscopy and bronchoscopy [11–13]. However, most of these studies mainly compared sedative drugs and did not examine actual real-world clinical situations, such as evaluation after addition or switching of drugs when adequate sedation was difficult to achieve.

The present study was conducted in consecutive cases in which transcutaneous blood gas monitoring was performed during bronchoscopy at our department. The results were organized and analyzed retrospectively based on whether the patient was anesthetized with midazolam + fentanyl (MF group) or with midazolam + fentanyl, followed by the addition of propofol instead of additional midazolam in patients with inadequate sedation (MFP group). The purpose of this study was to evaluate the safety of additional use of propofol by transcutaneous gas monitoring in patients in whom adequate sedation could not be achieved with the usual anesthesia for bronchoscopy.

Patients and Procedures

This retrospective analysis was conducted on the data of 82 consecutive patients who had undergone bronchoscopy at Dokkyo Medical University School of Medicine, Respiratory Endoscopy Center between April 2018 and August 2019 under transcutaneous blood gas monitoring. All of the patients were 18 years old or over. Twenty-one patients were excluded because of renal dysfunction (n = 9), cryobiopsy (n = 4), measurement error (n = 3), bronchial thermoplasty (n = 2), no sedation (n = 1), tracheotomy (n = 1), and intubation (n = 1). The remaining 61 patients were divided into two groups: 1) 41 patients who underwent bronchoscopy under sedation with midazolam + fentanyl (MF group), and 2) 20 patients who received additional use of propofol instead of midazolam when adequate sedation could not be achieved with midazolam + fentanyl (MFP group) (Fig. 1).

Sedation was induced starting with about 0.05 mg/kg of midazolam and adjusted to Richmond Agitation-Sedation Scale (RASS) -3 to -4 and Ramsay scale 5 [14, 15]. If the desired sedation was not obtained at the time of induction, an additional 0.5-1 mg dose of midazolam was administered. If arousal was still observed during the examination, yet another 0.5-1 mg dose of midazolam was given as appropriate. If the above sedation scale could not be achieved even after the additional administrations of midazolam, midazolam was discontinued and replaced with propofol at the discretion of the physician performing the procedure (MFP group). Propofol was used in the range of 0.3–3.0 mg/kg/h, and the depth of sedation was adjusted on the same scale as that for midazolam. Fentanyl was used concomitantly at the dose of 0.3–0.5 µg/kg as an analgesic and to suppress the cough reflex. Additional 0.2 µg/kg doses were given as required. No restrictions were placed on the use of fentanyl after the addition of propofol. Oxygen supplementation was used as appropriate to maintain the oxygen saturation as measured by pulse oximetry (SpO₂) at above 90%. Local anesthesia was administered by spraying 200 mg of lidocaine into the larynx as pretreatment prior to the bronchoscopy and as needed during the examination. Excess sprayed or inhaled lidocaine was collected by aspiration.

Bronchoscopy was performed by several experienced respiratory physicians. Transcutaneous gas measurement during the examination was performed using TCM5 FLEX®ฎ (Radiometer, Inc.), a transcutaneous blood gas partial pressure measuring device. The device’s temperature was set at 44°C, and the tcpCO₂ and transcutaneous pressure of oxygen (tcpO₂) were measured continuously. Pulse oximetry, electrocardiographic, and blood pressure monitoring were also performed simultaneously.

The patient background characteristics were organized by the age, gender, body mass index (BMI), pulmonary function test results (percent predicted vital capacity [%VC], percent predicted forced vital capacity [%FVC], forced expiratory volume in one second/forced vital capacity [FEV₁/FVC], percent predicted forced expiratory volume in one second [%FEV1]), the blood gas analysis [BGA] data (pH, arterial partial pressure of carbon dioxide [PaCO₂], arterial partial pressure of oxygen [PaO₂], base excess [BE], bicarbonate [HCO₃⁻]), suspected disease/procedure indication (lung cancer, infection, others [interstitial pneumonia, bronchial asthma etc.]), bronchoscopic procedure performed (transbronchial biopsy [TBB]/ transbronchial lung biopsy [TBLB], bronchoalveolar lavage [BAL], transbronchial needle aspiration [TBNA], others), and adverse events encountered (need for tracheal intubation, need for use of vasopressors, delayed arousal lasting until after return of the patient to his/her room).

Monitoring during bronchoscopy included the duration of monitoring (from anesthesia start to completion of the examination) and the following ventilatory indices: post-anesthetic tcpCO₂, maximum tcpCO₂ and minimum tcpCO₂ during the procedure, duration of tcpCO₂ > 50 mm Hg (min), and number of cases with tcpCO₂ > 50 mm Hg. As markers of oxygenation, the following indices were analyzed: the duration (min) for which the tcpO₂ value fell below 10 mm Hg during the procedure (ΔtcpO₂ <-10 time [min]), the maximum oxygen flow rate used during the procedure (max oxygen [L/min]), the duration of oxygen use (min), and the need for oxygen supplementation after the bronchoscopy (BF) (L).

The amounts of lidocaine (mg), midazolam (mg), propofol (mg) and fentanyl (mg) used as anesthetics during the bronchoscopy were analyzed. The amount of lidocaine used was recorded taking into account the amount by inhalation before bronchoscopy and by spraying during the bronchoscopy, but not the amount re-aspirated during the examination.

In the MFP group, the timing of initiation of propofol administration was categorized into “induction,” defined as propofol administration prior to the bronchoscopy because of inadequate sedation with MF, “<30 min,” that is, propofol administration within 30 minutes after insertion of the bronchoscope, and “≥30 min,” to indicate propofol administration later than 30 minutes after insertion of the bronchoscope.

Statistical Analysis

Statistical analysis for gender, indication, and procedure was performed by the Chi-square test. Student’s t-test was used for comparisons of the post-anesthetic tcpCO₂, maximum tcpCO₂, minimum tcpCO₂, number of cases with tcpCO₂ > 50 mm Hg, and the amounts used of lidocaine, midazolam, propofol and fentanyl. Mann-Whitney’s U test was used for statistical comparisons of the remaining variables. For comparison of the propofol-treated groups at the time of initiation of propofol (induction, < 30 min, ≥ 30 min), the Chi-square test was used for gender comparison, and the Kruskal-Wallis test was used for the remaining variables. P < 0.05 was considered as denoting statistical significance. All statistical analyses were performed using SPSS (IBM).

A total of 61 patients were eligible for the study, including 41 patients classified into the MF group (41/61, 67.2%) and 20 patients classified into the MFP group (20/61, 32.8%) (Fig. 1). None of the patients discontinued the bronchoscopic procedure which was difficulty in achieving appropriate sedation by additional propofol in place of midazolam.

Patients in the MFP group were younger than those in the MF group (median age,70 years [interquartile range (IQR) 64.5–76] vs. 65.5 years [IQR 51.5–69.0] p = 0.003), but there was no difference in the gender distribution or mean BMI between the two groups. Comparison of the spirometric parameters revealed no significant difference in %VC, %FVC, FEV₁/FVC, or %FEV₁ between the two groups (no data on the respiratory function parameters were available for six patients in the MF group and 4 patients of the MFP group). There were no statistically significant differences in the BGA data (pH, PaCO₂, PaO₂, BE, HCO₃⁻) between the two groups (Table 1) (BGA data were missing for four patients of the MF group and 3 patients of the MFP group). In regard to the indications for bronchoscopy (procedure indication), lung cancer was the most common (33/41 [80.5%] in the MF group and 12/20 [60.0%] in the MFP group), followed by infection (1/41 [2.4%] in the MF group and 3/20 [15.0%] in the MFP group), and others (7/41 [17.1%] in the MF group and 5/20 [25.0%] in the MFP group). Thus, there were no significant differences in the indications for bronchoscopy between the two groups (p = 0.269) (Table 2).

In terms of the contents of the test procedure, in cases where a single procedure was performed, TBB/TBLB was the most common (22/41 [53.7%] in the MF group and 10/20 [50.0%] in the MFP group), followed by BAL (0/41 [0%] in the MF group and 1/20 [5.0%] in the MFP group), TBNA (6/41 [14.6%] in the MF group and 1/20 [5.0%] in the MFP group), and others (2/41 [4.9%] in the MF group, 2/20 [10.0%] in the MFP group). Two procedures were used in combination in 9/41 (21.9%) cases in the MF group, and 4/20 (20.0%) cases in the MFP group, and three procedures were performed during the same session in 2/41 (4.9%) patients in the MF group and 2/20 (10.0%) patients in the MFP group. Thus, there were no significant differences in the contents of the test procedure between the two groups (p = 0.265).

No severe adverse events (need for tracheal intubation, need for use of vasopressors, delayed arousal until after the patient’s return to the ward) were observed in either of the groups (Table 2).

In respect of monitoring during the procedure, the duration of monitoring (min) was longer in the MFP group (45.0 [IQR 32.5–61.5] vs. 75.0 [IQR 40.0–86.5], p = 0.018). In addition, the duration of tcpCO₂ > 50 mm Hg (min) was significantly higher in the MFP group (0.0 [IQR 0–13] vs. 7.8 [IQR 0–48.8], p = 0.042). As for oxygen use, the max oxygen flow rate (L/min) (0.0 [IQR 0–2] vs. 2.0 [IQR 1–3.75], p = 0.005) and duration of oxygen supplementation during the procedure (0.0 [IQR 0–13.5] vs. 25.0 [IQR 4.75–60.0], p < 0.001) were significantly higher in the MFP group. The number of patients with tcpCO₂ > 50 mm Hg was 6/41 (14.6%) in the MF group and 13/20 (65.0%) in the MFP group, being significantly higher in the MFP group (p < 0.001). No statistically significant difference was observed in the post-anesthetic tcpCO₂, max tcpCO₂, minimum (min) tcpCO₂, ΔtcpO₂ <-10 mm Hg time or duration of oxygen supplementation after the BF (L). No statistically significant difference was observed in the amounts used of lidocaine (mg), midazolam (mg), or fentanyl (mg) (Table 3).

In the MFP group, the time of initiation of propofol administration was categorized as “induction,” (n = 11), “<30 min” (n = 4), and “≥30” (n = 4) (1 patient was excluded because data on the time of administration of propofol was not recorded). There were no significant differences in the age, gender, BMI, %FVC, FEV₁(G), BGA data, duration of monitoring, post anesthetic tcpCO₂, maximum tcpCO₂, minimum tcpCO₂, duration of tcpCO₂ > 50 mm Hg, ΔtcpO₂ <-10 time, maximum oxygen supplementation flow rate, duration of oxygen supplementation (min), need for oxygen supplementation after the BF (L), or the amounts of lidocaine, midazolam and fentanyl used among the 3 groups (Table 4).

Transcutaneous gas measurement involves heating a sensor to dilate the subcutaneous arteries and measures the amounts of oxygen and carbon dioxide that diffuses through the skin. tcpO₂ is reported to be well correlated with the arterial oxygen partial pressure [16], and tcpCO₂ is reported to be well correlated with the arterial pCO₂ [10]. In this study, transcutaneous gas monitoring used to evaluate the safety of additional anesthetic administration. In our study, the group that required additional propofol administration (MFP group) was relatively young and had a better mean FEV₁/FVC than the MF group. This implies the importance of continuous CO₂ monitoring taking into consideration the risk of hypoxemia and ventilatory insufficiency when using additional propofol, even in young patients with a good respiratory function status.

Midazolam, a benzodiazepine sedative, has a long half-life and shows relatively poor clearance in older persons [17]. Similarly, flunitrazepam is reported to be associated with a linear increase in the post-test amnesic action with increasing age, and the ability to stand and walk and eye co-ordination takes longer. [18]. In general, as older persons tend to show reduced liver metabolism and renal excretion functions, even other sedative drugs can cause prolonged sedation [19]. However, younger patients often require higher doses of anesthetic drugs than older patients to achieve the desired depth of sedation. The MFP group consisted of many young patients (Table 2), and therefore it was difficult to obtain adequate sedation using the same dose of midazolam as in the other group. Moreover, as adequate sedation was difficult to achieve in this group with midazolam, the patients were switched to propofol. In the present study, additional propofol was most often added because of inadequate sedation during the induction period (Table 4). Accordingly, the longer examination time in the MFP group may have been due to the longer time required at induction because of the difficulty in sedation. The “induction” group included many younger patients, and adequate sedation was difficult to achieve with midazolam alone, and additional propofol was required. On the other hand, the “≥30” group included relatively old patients, with reduced respiratory functions, in whom carbon dioxide could easily accumulate in the body and the resultant hypercarbia could lead to agitation, necessitating additional propofol administration [20].

While propofol has a rapid onset and recovery time, the optimal concentration range is narrow, and as respiratory depression could therefore occur relatively easily because of over-sedation, cautious use is important. As compared with midazolam anesthesia during bronchoscopy, propofol has been reported to be better tolerated by the patients, but due to the reasons mentioned above, use of the bispectral index is recommended [21]. A previous report comparing ventilatory failure following administration of propofol and midazolam during bronchoscopy performed under transcutaneous blood gas monitoring analysis showed no difference in tcpCO₂ value between the two drugs [13]. Another study showed no difference in the mean lowest arterial oxygen saturation during bronchoscopy between a group administered propofol and a group administered a combination of a benzodiazepine plus opioid anesthesia during bronchoscopy, despite the potential risk of respiratory failure, suggesting that propofol is a useful anesthetic agent for use during bronchoscopy [22]. However, this study focused on the oxygenation status, and not on ventilatory failure. The aforementioned study was similar to ours in that an opioid was used in combination with a benzodiazepine, but we switched to propofol after midazolam. Since midazolam had already been used, the MFP group might have been more prone to ventilatory failure.

In 20 of the 61 patients (32.8%) analyzed in this study (MFP), the examining physician judged that the sedation achieved with the commonly used anesthesia regimen was inadequate and chose to switch the sedative. The relatively high percentage of patients in whom inadequate sedation was achieved with the commonly used midazolam + fentanyl combination indicates that this scenario is often experienced in clinical practice. The purpose of our study was to evaluate the safety of switching the sedative to propofol. Although switching to propofol significantly increased the duration of tcpCO₂ > 50 mm Hg (min), number of patients in whom tcpCO₂ exceeded 50 mm Hg, and the oxygen use time, it was associated with better tolerance of the patients to bronchoscopy, and the examination could be completed in all the patients. Moreover, no serious adverse events were observed (Table 3).

The limitations of this study included the small number of patients and the retrospective design of the study conducted at a single center. At least, it is clear that bronchoscopy can be conducted safely with the addition of propofol after midazolam in patients in whom adequate sedation is not achieved with the latter alone at our institution.

Switching to propofol from midazolam is an effective option for anesthesia during bronchoscopy for patients in whom adequate sedation is not achieved with the commonly used combination of a benzodiazepine + opioid. On the other hand, addition of propofol may be associated with a significant risk of ventilatory failure, so that it may be advisable to use propofol only under conditions that would allow continuous monitoring of the patient’s ventilatory status, such as by transcutaneous blood gas measurement.

tcpCO_2:transcutaneous carbon dioxide, PaCO₂: partial pressure of arterial carbon dioxide, MF group: the midazolam + fentanyl group, MFP group: the group in which midazolam was switched to propofol because of inadequate sedation with midazolam + fentanyl, EtCO₂: end-tidal exhaled carbon dioxide, RASS: Richmond Agitation-Sedation Scale, SpO₂: the oxygen saturation as measured by pulse oximetry, tcpO₂: transcutaneous pressure of oxygen, BMI: body mass index, %VC: the percent predicted vital capacity, %FVC: percent predicted forced vital capacity, FEV₁/FVC: forced expiratory volume in one second/forced vital capacity, %FEV₁: percent predicted forced expiratory volume in one second, BGA: the blood gas analysis, PaCO₂: arterial partial pressure of carbon dioxide, PaO₂: arterial partial pressure of oxygen, BE: base excess, HCO₃^-: bicarbonate, TBB: transbronchial biopsy, TBLB: transbronchial lung biopsy, BAL: bronchoalveolar lavage, TBNA: transbronchial needle aspiration.

Ethics approval and consent to participate

This experiment was performed in accordance with the Declaration of Helsinki and approved by the Institutional Review Board for Clinical Research, Dokkyo Medical University (Approval No.: R-15-5J). Informed consent was obtained in the form of opt-out on the website from all subjects. We have posted adequate period to confirm this research project for all subjects. Those who rejected were excluded. All methods in the study were carried out in accordance with the R-15-5J approval.

Consent for publication

Consent for publication was also included in the opt-out form, and the consent was obtained in same way of informed consent from all subjects.

Availability of data and materials

These data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to containing information that could compromise research participant privacy.

Competing interests

The authors declare that they have no potential conflicts of interests to disclose.

Funding

This study was funded by Dokkyo Medical University School of Medicine.

Authors' contributions

N.Y. and Y.N. prepared all the figures and wrote the manuscript. Y.N. designed the study. N.U., Y.S., M.M., H.O., S.S., N.I. and R.A. undertook the bronchoscopy data collection. A.T., K.C., S.N. and Y.S. advised us on the study design and contributed to the discussion and development of the study. All the authors reviewed the manuscript.

Acknowledgements

This work was partly supported by Dokkyo medical University Investigator-Initiated Research Grant to Y.N. (No.2020-05). The authors wish to thank Ms. Sakai and Mr. Sawaguchi of the Respiratory Endoscopy Center for assisting with the transcutaneous measurements.

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Tables 1 to 4 are available in the Supplementary Files section.

No competing interests reported.

20230103BMCtable1.xlsx
Table 1: Total patient characteristics. []: interquartile range Abbreviations: %VC, percent predicted vital capacity; %FVC, percent predicted forced vital capacity; FEV1/FVC, forced expiratory volume in one second / forced vital capacity; FEV1%, percent predicted forced expiratory volume in one second; BGA, blood gas analysis; PaCO₂,partial pressure of carbon dioxide; PaO₂, partial pressure of oxygen; BE, base excess; HCO₃^-, bicarbonate.
20230103BMCtable2.xlsx
Table 2: Bronchoscopy indication, procedure, and adverse events. Abbreviations: TBB, transbronchial biopsy; TBLB, transbronchial lung biopsy; BAL, bronchoalveolar lavage; TBNA, transbronchial needle aspiration.
20230103BMCtable3.xlsx
Table 3: Transcutaneous pressure (tcp) of CO₂ and O₂ during flexible fiberoptic bronchoscopy and anesthesia classified by the group (MF vs. MFP). Abbreviations: tcpCO₂, transcutaneous carbon dioxide; tcpCO₂, transcutaneous partial pressure of carbon dioxide.
20230103BMCtable4.xlsx
Table 4: Patient background characteristics and transcutaneous pressure (tcp) of CO₂ and O₂ according to the time of initiation of propofol administration.

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The midazolam and fentanyl versus additional use of propofol in difficult-to-sedate cases during bronchoscopy by transcutaneous gas monitoring: a case control study

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