Evaluation of Intubating Conditions with Varying Doses of Propofol without Muscle Relaxants.

BACKGROUND: Since 1988 anaesthesiologist have proved that induction dose of propofol is sufficient to intubate patient without muscle relaxants. Propofol is unique in having property to suppress airway reflexes better than any other agent. Therefore study was undertaken to evaluate clinically acceptable intubating conditions with different doses of propofol without muscle relaxants. PATIENTS AND METHODS: 90 ASA grade I and II patients posted for elective surgery requiring general anesthesia divided randomly into group I (propofol 2 mg kg(-1)); group II (2.5 mg kg(-1)); groupIII (3mg kg(-1)). Premedication with inj.Glycopyrollate, inj.Ranitidine, Inj.Ondensetron; inj.Midazolam and inj.fentanyl was done. After waiting for 5 minutes, 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 group II (2.5 mg kg(-1) propofol) and 100% in group III (3 mg kg(-1) propofol). We found that clinically acceptable intubating conditions can be achieved with 2.5 mg kg(-1) and 3 mg kg(-1) propofol without significant hemodynamic changes and 100% success can be obtained with 3 mg kg(-1) of propofol
CONCLUSION: Ideal intubating conditions without muscle relaxants can be achieved with propofol 3 mg kg(-1) with fentanyl 2 μg kg(-1) and lignocaine 1.5 mg kg(-1) without significant hemodynamic changes.

RCT Entities:   Population Interventions Outcomes

Keaveny JP and Knell PJ were amongst the first workers to propose the concept of intubation with only propofol without muscle relaxants.1 This was the begining for the thought of elimination of muscle relaxants for intubation. In 1988, Mckeating K, Bali IM, Dundee JW compared thiopentone (4&5mg kg-1) and propofol (2.5mg kg-1) to asses suppression of airway reflexes and found propofol to be better hypnotic.2 Stevens JB, Vesoco V, Harris K found that etomidate with alfentanil and propofol with alfentanil produce comparable intubating conditions, better than thiopentone with alfentanil. They also found that addition of lignocaine improves condition for intubation with attenuation of intub-ation response.3 Saarnivaara L, Klemola VM could achieve 89% success in intubation with 2.5 mg kg-1 propofol with 30μg kg-1 alfentanil without muscle relaxants.4 Mulholand D, Carlisle RJT compared tracheal intubation with 2.5 mg kg-1 propofol with and without 1.5 mg kg-1 lignocaine without any opioids and muscle relaxants. They found that dose of 2.5mg kg-1 propofol is sufficient to intubate the trachea without muscle relaxants and addition of ligocaine 1.5 mg kg-1 attenuates the stress response to intubation well.5

We in our study have compared different doses of propofol with lignocaine and fentanyl to obtain clinically acceptable intubating conditions without using muscle rela-xants. Attenuation of pressor response and haemodynamic changes were also observed during the study.

PATIENTS AND METHODS

90 ASA class I and II patients who were posted for abdominal, orthopaedic, gynecological, ENT surgeries requiring general anesthesia were chosen for study and divided randomly into 3 groups.

Group I received 2 mg kg-1 propofol, Group II 2.5 mg kg-1 propofol and group III received 3 mg kg-1 propofol.

Criterion for choosing the patients include age between 20 to 65 years, ASA class I or II and MPC grade I or II. Patients with history of hypertension, asthma and previously documented difficult intubation were excluded from the study.

Written informed consent was obtained from each patient.

On the OT table each patient was attached to ECG monitor, Pulse-oximeter and NIBP. All the patients were cannulated with 18G cannula and 10 ml kg-1 of ringer lactate solution was given 10 minutes before induction.

All patients were premedicated with inj.Glycopyrollate 5μg kg-1, Inj. Ranitidine 0.3 mg kg-1, Inj. Ondensetron 100 μg kg-1, inj. Midazolam 0.02 mg kg-1and Inj. Fentanyl 2 μg kg-1one after the other as slow i.v bolus in the same order.

After giving inj. Fentanyl patients were watched for apnea, oxygen saturation and given 100% oxygen by mask.

As fentanyl takes 5-7 minutes for its plasma concentration to equilibrate with that of brain concentration, we waited for 5 minutes after giving inj.fentanyl after which inj. propofol either 2mg kg-1, 2.5 mg kg-1 or 3 mg kg-1 in precalculated amount, chosen randomly (based on computer generated randomization) and grouped accordingly was given slowly intravenously over 10 seconds followed by inj. Lignocaine 1.5 mg kg-1 as i.v bolus.

The order of giving Propofol and lignocaine was planned such a way that laryngoscopy and intubation was done at 7 minutes after giving Fentanyl.

Patients were watched for apnea, oxygen saturation and ventilated bag mask with 100% oxygen.

90 seconds after completion of propofol injection, laryngoscopy and intubation was performed. We waited for 90 seconds because good to excellent intubating conditions are reported 90 seconds after hypnotic doses of propofol.3

For success only one attempt at laryngoscopy and intubation was considered. All male patients were intubated with portex cuffed endotracheal tube no.8.5 and female patients with no.7.5

Clinically acceptable intubating conditions = excellent+ good Hemodynamic responses were recorded at following stages: - baseline value, after premedication, at 5 minutes after inj.Fentanyl, after giving propofol and lignocaine, pre-intubation, post-intubation, 5 minutes after intubation.

If patients could not be intubated they were given muscle relaxant to facilitate intubation.Following intubation, anesthesia was maintained at the discretion of attending anesthesiologist.

RESULTS

There was no significant difference in gender of cases in any of the propofol group

In group II clinically acceptable intubating conditions (excellent+good) were present in 96.70% with failure rate being 3.30%.In group III clinically acceptable intubating conditions (excellent+good) were present in 100% patients with failure rate being zero.

During laryngoscopy and intubation there was significant increase in heart rate in all the three groups (P < 0.05 ) but when compared between group I, II and III there was no significant difference.

During laryngoscopy and intubation there was significant rise in MAP in group I (P < 0.05) not only from the baseline level but also from the level at preoxygenation.5 minutes after laryngoscopy and intubation the MAP returned almost to the baseline level. In group II and III, during laryngoscopy and intubation there was rise in MAP but it remained below the baseline level and remained the same 5 minutes after intubation.

DISCUSSION

Keaveny JP et al were one of the first workers who achieved 95% success rate of intubation without neuromuscular blocking agents; only with propofol 2.5 mg kg-1.1

Anaesthesiologists have tried to formulate combination of drugs which will help us to intubate patients without coughing or bucking in absence of muscle relaxants.

Mullholand D et al have used lignocaine 1.5 mg kg-1 and found incidence of post intubation coughing lower than in which lignocaine was not used.5

In our study in Group I (Propofol 2 mg kg-1) we found that 10% of patients had excellent and 56.70% patients had good intubating conditions (Table 1). Thus 66.70% patients had clinically acceptable intubating conditions (excellent + good) However 33.30% patients could not be intubated and had to be given muscle relaxants to achieve it. Better intubating conditions with 2 mg kg-1 of propofol have been reported by Erhan E et al achieved along with remifentanil 30μg kg-1 6 scheller M et al achieved 100% success rate with 2 mg kg-1 propofol and 40 μg kg-1 Alfentanil as optimum dose. They observed that when dose of Alfentanil was increased to 50 μg/kg-1 success rate dropped to 93% and with 60 μg/kg-1 it further dropped to 86%. Authors could not explain the reason.7

Intubating conditions were assessed as follows:

However Saarnivara L et al achieved only 16% success rate with 2 mg kg-1 propofol and 30 μg kg-1 Alfentanil.4

Compared to our study the higher success rate achieved by Grant S et al10 and Scheller M et al7 might be due to use of Remifentanil and Alfentanil.

In our study in group II (propofol 2.5 mg kg-1) we found that excellent intubating conditions were present in 66% of patients and good intubating conditions were present in 36.70%. Thus 96.70% patients had clinically acceptable intubating conditions and only 3.30 % of patients could not be intubated and were given muscle relaxants for achieving it (Table 1).

The result obtained by us are significantly better than Leitaut T et al who found clinically acceptable intubating conditions in only 35% of patients with propofol 2.5 mg kg-1 (like us) and Fentanyl 3 μg kg-1 (higher than us). In their study authors performed Laryngoscopy and Intubation 3 mins after Fentanyl injection whereas we did Laryngoscopy, Intubation at 7 mins after Fentanyl injection.9

The peak action of Fentanyl comes after 7 mins34 and the smaller time lag after Fentanyl injection might be the cause of their poor success.

Davidson JAH et al found clinically acceptable intubating conditions in 93% of patients with propofol 2.5 mg kg-1 and Alfentanil 20 μg kg-1 with 1 mg kg-1 propofol and Alftentanil 10 μg kg-1.10 Alcock R. et al found 86% clinically acceptable intubating conditions with 2.5 mg kg-1 propofol and Alfentanil 10 μg kg-1.11

Clinically acceptable intubating condition in 66% of patients with 2.5 mg kg-1 propofol and 1.5 mg kg-1 Lignocaine has been reported by Mullholand D et al. the authors did not use any opioids in that study.5 May be this is the cause for lower success rate.

Howorkaa J et al have studied intubating conditions without muscle relaxants with Pentothal 5 mg kg-1 and propofol 2.5 mg kg.-1 They found that they could visualize the cords in 60% of patients and intubate easily in 48 % of patients in Pentothal group as against 46% visualization and 22% intubation in propofol group.12

However better intubating conditions with propofol than other hypnotics have been reported by Erhan E et al6 and Mckeating K et al.2

In our study with 3 mg kg-1 Propofol we got excellent intubating conditions in 56.70% of patients and good intubating conditions in 43.30% of patients. Thus clinically acceptable intubating conditions were found in 100% of patients; Failure rate being Zero% (Table 1).

Khouri SJ et al reported 62.5% clinically acceptable intubating conditions.13 This lower success rate of authors as compared to our results could be due to early intubation by them. They intubated the patients 90 seconds after Fentanyl whereas we intubated after 7 mins of Fentanyl injection.

Attenuation of pressor response and hemodynamic changes were also assessed. For this we took the blood pressure recordings after premedication (midazolam and fentanyl) as the baseline blood pressure for comparison between different propofol groups.

We found that in all the three groups after premedication there was a fall in MAP compared to baseline level which is not significant.

When compared between the three groups there was no significant difference in the fall of MAP with 2, 2.5, 3 mg kg-1 of propofol (Graph 4) and none of the patients had to be treated for hypotension.

Figure 4

Comparison of mean arterial pressure at various intervals in three propofol groups.

Similar results of fall in MAP not requiring active management have been reported by Stevens J et al3; and Davidson JAH et al.10

During Laryngoscopy and intubation there was significant increase in Heart rate in all the three groups but when compared between gr I, II and III there was no significant difference (Graph 3).

Figure 3

Comparison of heart rate in three propofol groups

However during Laryngoscopy and Intubation there was a significant rise in MAP in Gr. I. The rise was significant not only from the baseline level but also from the level at preoxygenation. 5 min after Larygoscopy and Intubation the MAP returned almost to the baseline level. (Graph 4).

In gr. II and III during laryngoscopy and intubation there was rise in MAP but it remained below the baseline level and remained same 5 min after intubation (Graph 4).

There was significant difference in response to larygoscopy and intubation between group I and group II and III. There was good attenuation of response to laryngoscopy and intubation in 2.5 mg kg-1 and 3 mg kg-1 propofol group along with 1.5 mg kg-1 Lignocaine and 2 μg kg-1 fentanyl. (Graph 4)

Thus in conclusion, ideal intubating conditions for intubation without using muscle relaxants are possible with 3 mg kg-1 propofol with 2μg kg-1 fentanyl and 1.5 mg kg-1 lignocaine and the stress response to laryngoscopy and intubation gets attenuated well.

Gender distribution in three propofol groups.

Comparison of intubation score between in 3 Propofol group

Table 2

Comparison of intubating conditions in 3 Propofol groups