|Year : 2018 | Volume
| Issue : 3 | Page : 711-714
A study to assess the efficacy of different doses of propofol for tracheal intubation: A randomized clinical trial
Mohammad Asif1, Aman Sai Guntreddy2
1 Department of Anesthesia, SDM Medical College, Dharwad, Karnataka, India
2 Department of Anesthesia, Andhra Medical College, Visakhapatnam, Andhra Pradesh, India
|Date of Web Publication||11-Sep-2018|
Dr. Aman Sai Guntreddy
Department of Anesthesia, Andhra Medical College, Visakhapatnam, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: Tracheal intubation is usually facilitated by using a muscle relaxant to supplement drugs given for the induction of general anesthesia. Nondepolarizing muscle relaxants are also associated with the few disadvantages. Endotracheal intubation under volatile anesthetics without the use of muscle relaxants is possible, but it has disadvantages. Time available for intubation is much less when compared to the use of muscle relaxants. Considering the disadvantages of muscle relaxants and volatile agents in mind, there is a need for endotracheal intubation without muscle relaxants. Objective: The objective of the study is to assess the efficacy of different doses of propofol for tracheal intubation – a randomized clinical trial. Materials and Methods: A randomized study was conducted on 80 patients, comprising of 40 patients each. Patients of either sex were randomly allocated into Group P1 and Group P2 by computer-generated random numbers where Group P1 received 2 mg/kg propofol +3 μg/kg fentanyl and Group P2 received 4 mg/kg propofol +3 μg/kg fentanyl. SpO2, heart rate, blood pressure (BP)- systolic BP, diastolic BP, and mean arterial pressure were recorded at 1 and 3 min after administration of study drugs were recorded. Intubating conditions were assessed modified Helbo–Hansen scoring system. Results: The success rate of endotracheal intubation was 62.5% and 95% in propofol 2 mg/kg + fentanyl 3 μg/kg and propofol 4 mg/kg + Fentanyl 3 μg/kg, respectively. The total incidence of hypotension was 40% and 83% in propofol 2 mg/kg + Fentanyl 3 μg/kg and propofol 4 mg/kg + Fentanyl 3 μg/kg, respectively. The incidence of hypersensitivity was noted only in propofol 4 mg/kg + Fentanyl 3 μg/kg group and was 2.5%. Conclusion: We conclude that endotracheal intubation is possible in premedicated adult American Society of Anesthesiologists by Grade I patients with receiving 3 μg/kg Fentanyl + 2 mg/kg or 4 mg/kg propofol for induction without muscle relaxants, and the intubating conditions are acceptable. We found that propofol 4 mg/kg + Fentanyl 3 μg/kg is the optimal dose required for intubation without the use of muscle relaxants.
Keywords: Anesthesia, intubation, propofol, trachea
|How to cite this article:|
Asif M, Guntreddy AS. A study to assess the efficacy of different doses of propofol for tracheal intubation: A randomized clinical trial. Anesth Essays Res 2018;12:711-4
|How to cite this URL:|
Asif M, Guntreddy AS. A study to assess the efficacy of different doses of propofol for tracheal intubation: A randomized clinical trial. Anesth Essays Res [serial online] 2018 [cited 2019 Mar 21];12:711-4. Available from: http://www.aeronline.org/text.asp?2018/12/3/711/240884
| Introduction|| |
Tracheal intubation is usually facilitated by using a muscle relaxant to supplement drugs given for the induction of general anesthesia. Suxamethonium is the most commonly used muscle relaxant in day-to-day anesthetic practice but, it has many potential problems - bradycardia, asystole, increased salivation, increased intraocular and intracranial pressures, hyperkalemia, myalgia, and rarely life-threatening malignant hyperthermia. In pediatric anesthetic practice, utmost concern is its potential to cause masseter spasm, unexplained cardiac arrest and death.,
Other alternatives such as nondepolarizing muscle relaxants are associated with the following disadvantages:
- Prolonged neuromuscular blockade when compared to suxamethonium
- The inability to reverse the blockade quickly if airway management through mask or tracheal intubation not possible
- They are not suitable for surgeries of short duration.
Endotracheal intubation under volatile anesthetics without the use of muscle relaxants is possible, but it has the following disadvantages:
- Anesthetic depth required to produce the satisfactory intubating conditions may be difficult to gauge
- Premature attempt at intubation can result in life-threatening laryngospasm
- Time available for intubation is much less when compared to the use of muscle relaxants.
Cardiovascular events bradycardia, hypotension, and myocardial depression can occur  and this may not be acceptable in patients with compromised myocardial reserve and function as in Ischemic heart disease. Considering the disadvantages of muscle relaxants and volatile agents in mind, there is a need for endotracheal intubation without muscle relaxants. Propofol is unique in having property to suppress airway reflexes better than any other agent, abducts, and immobilizes the vocal cords enabling laryngoscopy. Keaveny and Knell were among the first workers to propose the concept of intubation with only propofol without muscle relaxants. This was the beginning for the thought of elimination of muscle relaxants for intubation.
In some studies, intubating conditions under propofol without muscle relaxants ranged from impossible/unacceptable to as ideal as produced by suxamethonium. Hovorka et al. in 1991 concluded that propofol alone without muscle relaxants produced unacceptable intubating conditions and that muscle relaxants need to be used routinely for endotracheal intubation.
Striebel et al. in 1995 concluded that the intubating conditions produced by propofol supplemented with fentanyl but without the use of muscle relaxants produced conditions that were as ideal as that produced by thiopentone and suxamethonium.
Fentanyl as a supplement to propofol for endotracheal intubation has not been extensively studied. Available literature reveals conflicting conclusions regarding the feasibility and intubating conditions (not possible/possible but not ideal/possible and ideal as with relaxants) under propofol without muscle relaxants.
Hence, this prospective randomized clinical trial was conducted employing two fixed doses of propofol 2 mg/kg or 4 mg/kg supplemented with a fixed dose of 3 μg/kg fentanyl (without muscle relaxants) in adult patients with normal airway anatomy for endotracheal intubation. Feasibility, intubating conditions, effect on the hemodynamics, and safety were studied and compared.
The objective of the study is to assess the efficacy of different doses of propofol for tracheal intubation – a randomized clinical trial.
| Materials and Methods|| |
A prospective randomized clinical trial was conducted at Shri B. M. Patil Medical College Hospital Vijayapura, from December 2014 to June 2016. All patients requiring general anesthesia through endotracheal tube for elective surgical procedures and meets the inclusion criteria were included in the study.
All cases of elective of procedure under general anesthesia with the American Society of Anesthesiologists (ASA) Grade I and modified Mallampati class I airway anatomy or below within the age of 21–40 years with body mass index (BMI) between 18.5 and 24.9.
During preanesthetic evaluation, history of any significant medical illness (endocrine/metabolic derangement, hypertension, valvular cardiac lesions, and bronchial asthma) or drug hypersensitivity if any was elicited. Weight, pulse rate, and blood pressure (BP) were recorded during the general examination of the patients. Airway assessment: Mouth opening, temporomandibular joint movement, Mallampati view of upper airway, submandibular space, and cervical spine movement was assessed patients were asked to sit with head in neutral position, the mouth wide open and tongue protruding to its maximum and the airway assessed at eye level patients with:
- One finger insinuation at the temporomandibular joint
- More than 2 finger breadths (>4 cm) of mouth opening (inter-incisor distance)
- More than 3 finger breadths of thyromental distance (>6 cm) – submandibular space
- Mallampati class I view – visualization possible of the soft palate, entire uvula, anterior and the posterior tonsillar pillars
- Normal neck movements – flexion, extension, and side to side movements were included in our study.
Patients fulfilling the above criteria were included in our study.
- Anticipated difficult intubation
- Upper airway pathology
- Heart diseases
- Emergency surgeries.
Patients of either sex were randomly allocated into Group P1 and Group P2 by computer-generated random numbers.
- Group P1 received 2 mg/kg propofol +3 μg/kg fentanyl
- Group P2 received 4 mg/kg propofol +3 μg/kg fentanyl.
Design of the study
Intravenous (IV) line was secured using 18G cannula, and all patients were preloaded with 10 ml/kg body weight crystalloid over 15 min. Electrocardiography, noninvasive BP, and SpO2 were monitored. Baseline heart rate (HR), SpO2, and BP (systolic, diastolic, and mean arterial pressure [MAP]) were recorded. The study drugs were injected into the forearm vein in the following sequence contents of the 5 ml syringe–Fentanyl 3 μg/kg over 15 s and after 1 min, administration of the contents of the 5 ml syringe containing Xylocard 0.2 mg/kg and propofol 2 or 4 mg/kg over 30 s. SpO2, HR, BP-systolic BP (SBP), diastolic BP (DBP), and MAP 1 min after administration of study drugs were recorded. The difference between the preinduction baseline HR and B.P. readings and the corresponding readings 1 min after the completion of injection of the study drugs but before laryngoscopy and intubation was taken as the effect of drugs on the cardiovascular system. One minute after the administration of the study drugs, direct laryngoscopy was performed using appropriate McIntosh curved blade, and the intubating conditions were assessed as per the modified Helbo–Hansen scoring system.,
- Unacceptable intubating conditions: Total score of 8 or more
- Acceptable intubating conditions: Total score of 7 or less
- Successful intubation: Total score of 7 or less coupled with first attempt endotracheal intubation with appropriate sized cuffed endotracheal tubes
- Failure: Inability to intubate in the first attempt was considered as failure. In these cases, suxamethonium was used before the second attempt at endotracheal intubation.
More than 20% difference between the preinduction baseline HR and BP readings and the corresponding readings 1 min after the completion of injection of the study drug but before laryngoscopy was considered as effect of the drug on cardiovascular system.
SpO2, HR and BP–SBP, DBP, MAP were recorded 1 min' and 3 min' postintubation. More than 20% of difference between the preinduction baseline HR and BP readings and the corresponding readings, 1-min postintubation was considered as presser response to laryngoscopy and intubation. HR and BP were recorded 3 min' postintubation to know whether HR and BP reached the baseline or not.
Data were analyzed using SPSS software v. 23.0(IBM Corp, Armonk, NY). For continuous variables, the summary statistics of n, mean, standard deviation (SD) were used. For categorical data, the number and percentage were used in the data summaries. Chi-square/Fisher's exact test was employed to determine the significance of differences between groups for categorical data. The difference of the means of analysis variables was tested with the unpaired t-test. If P < 0.05, then the results will be considered to be statistically significant.
| Results|| |
A total of 80 Patients 40 in each group Group 1 (P1) and 20 patients in Group 2 (P2) were included in the study.
The mean age of patients in P1 was 31.2 + 5.9 years and P2 was 30.7 + 5.6 years of age. The mean weight of patients in P1 was 53.1 + 7.1 kg and P2 was 53.4 + 5.4 kg. The BMI of Group P1 was 20 + 1.3 and P2 was 19.7 + 1 kg/m2. All the Variables were found to be statistically not significant.
The HR in the preinduction duration was 91 and 95.7 respectively in both Groups P1 and P2. The HR in both groups after 1 min of induction and postintubation and 3-min postintubation was almost similar, and it was also found to be statistically not significant.
The mean DBP was found to be statistically significant between both groups after 1 min after induction and after 1 min after intubation and even after 3-min postintubation.
The mean arterial BP was more in Group P1 than Group P2 and it was found to be statistically significant between both groups after 1 min after induction and after 1 min after intubation and even after 3-min postintubation.
The mean apnea duration in the P1 group was 4.4 min with 0.5 min SD and in P2 group the apnea duration was 4.2 min with 0.6 min' SD from the mean, and it was found to be statistically not significant.
In our study, the intubating condition score of 7 was considered as an indicator of acceptable intubating conditions. The intubating condition scores were Group P1 (6.8) >Group P2 (5.3).
Intubating conditions scores in Group P2 group was lower than Group P1, the statistical difference being very highly significant (P< 0.001).
| Discussion|| |
Propofol depresses pharyngeal and laryngeal tone making insertion of supraglottic airways easier. Propofol in certain doses depresses the laryngeal reflexes enabling laryngoscopy, abducts and immobilizes the vocal cords. These unique airway properties of propofol made some authors attempt endotracheal intubation under propofol alone without the use of muscle relaxants in adults and children.
Many scoring systems to evaluate intubating conditions are available. Based on a study done by Grant et al., Blair et al. and Gupta et al., we chose Modified Helbo–Hansen Scoring system as it is more descriptive including 5 parameters, each parameter assessed and graded individually. We preferred the modified Helbo–Hansen scoring system over the other scoring systems where all the variables were clubbed together and assessed in the same plane without assigning individual scoring to each of the variable. In practice, all the variables need not be in the same plane at a given time of assessment. We considered four (out of five) variables – jaw relaxation, ease of laryngoscopy, position of vocal cords, and coughing as the factors likely to influence the feasibility of endotracheal intubation. Hence, score ≤7 was considered as acceptable intubating condition score.
In the study of Grant et al. who considered all the variables including the limb movements of modified Helbo–Hansen scoring system to assess the intubating conditions. In our study, the incidence and intensity of purposeful/gross limb movements, (propofol 2 mg/kg + Fentanyl 3 μg/kg group only) at the time of laryngoscopy, was minimal and we were still able to intubate in the first attempt. This conclusion is in agreement with the study of Dr. Srivastava et al.
Among the study individuals in Group P1, our intubation success rate (62.5%) with propofol 2 mg/kg + Fentanyl 3 μg/kg is almost similar to the success rate (67%) in Scheller et al. and Tsuda et al. study. Our intubation success rate (62.5%) with propofol 2 mg/kg + Fentanyl 3 μg/kg in patients is marginally lesser than that of Mangesh S Gore and Kalpana D Harnagale  (66.7%) in patients. Gore and Harnagale  used IV. Lignocaine 1.5 mg/kg bolus after induction with propofol. Lignocaine has been reported to be a useful adjunct to facilitate tracheal intubation in the doses of 1–2 mg/kg. A decrease in HR by 5% in our study postinjection of study drugs agrees with a similar reduction (↓ 4%) in the HR observed in the study of Grant et al.
Among the study individualsin Group P2, the intubation success rate (95%) with propofol 4 mg/kg + Fentanyl 3 μg/kg is almost similar to the success rate (95%) in studies done by Olmos et al., Striebel et al. and (93%) Morgan et al. Decrease in HR by 10% in our study postinjection of study drugs is slightly different when compared to the HR change (↓ 13%) observed in the study of Dr. Srivastava et al. In our study, the incidence (83%) and magnitude of fall in MAP (↓ 27% mmHg) in response to the injection of the study drugs were observed. We are unable to quote any corroborative study.
| Conclusion|| |
We conclude that endotracheal intubation is possible in premedicated adult ASA Grade I patients with receiving 3 μg/kg Fentanyl + 2 mg/kg or 4 mg/kg propofol for induction without muscle relaxants and the intubating conditions are acceptable. The success of endotracheal intubation, the cardiovascular effects, and the side effects are dose-related. This technique is an alternative to the use of muscle relaxants on an individualized basis. We feel that propofol 4 mg/kg + Fentanyl 3 μg/kg is the optimal dose required for intubation without the use of muscle relaxants.
- Dr. Mohammad Asif for his contribution regarding the concept of the study, framing of the protocol of the study and collection of the data with literature searching and in writing the article with searching of references for the Manuscript
- Dr. Aman Sai contributed in the collection of the data of the study, data entry, and analysis of the data and helped in the searching of the literature and writing the Article.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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