Comparison of different doses of intranasal nitroglycerine in attenuation of pressor response to laryngoscopy and intubation.

AIMS: To observe the various pressor responses to laryngoscopy and intubation in normotensive patient undergoing elective surgery under general anesthesia and use of three different attenuating doses (400, 800, 1200 mcg) of intranasal nitroglycerine administered five minutes before laryngoscopy and intubation, to observe the efficacy and safety. SETTINGS AND
DESIGN: Randomized study.
MATERIALS AND METHODS: The study was carried out in a total of 60 patients. ASA grade 1 and II patients posted for elective surgeries under general anesthesia were included. Patients received different doses of intranasal nitroglycerine five minutes before induction as given below Group 1-received 400 micrograms-20 patients Group 2-received 800 micrograms-20 patients Group 3-received 1200 micrograms-20 patients. STATISTICAL ANALYSIS: Student's t test. RESULTS AND
SUMMARY: Results were statistically analyzed. All three groups effectively attenuated the pressor response to laryngoscopy and intubation. Maximum rise in heart rate was seen in group III (23.86%). Maximum fall in systolic (19.6%), diastolic (30.76%), and mean arterial blood pressure (25.53%) was observed in group III at 10(th) minute of laryngoscopy and intubation.
CONCLUSION: Best results of attenuation of pressor response were seen with 400 and 800 micrograms of intranasal nitroglycerine. One thousand and two hundred micrograms dose caused maximum increase in heart rate and caused maximum fall in blood pressure, hence it is advisable to use increased dose with caution in attenuation of pressor response to laryngoscopy and intubation.

INTRODUCTION

In 1940, Reid and Brace first described hemodynamic response to laryngoscopy and intubation. The rise in the pulse rate and blood pressure is usually transient, variable, and unpredictable. Usually, these changes are well tolerated by healthy individuals. However, these changes may be fatal in patients with hypertension, coronary artery disease, or intracranial hypertension. To blunt this pressure response, various methods have been tried.

In the present study, we had observed cardiovascular responses following laryngoscopy, intubation and compared efficacy of different doses of intranasal nitroglycerine spray with groups belonging to normotensive ASA grade I, II risk surgical patient.

MATERIALS AND METHODS

The study was conducted in a total of 60 patients with 20 in each group [Table 1]. The present study was undertaken to observe the various cardiovascular responses to laryngoscopy and intubation in normotensive patient undergoing elective surgery under general anesthesia. It was undertaken to observe the attenuating effects of different doses of nitroglycerine spray administered intranasally before laryngoscopy and endotracheal intubation in normotensive patient. To compare the heart rate changes in three groups treated with intranasal nitroglycerine during laryngoscopic manipulation. To observe the systolic, diastolic, and mean arterial blood pressure changes in groups treated with intranasal nitroglycerine spray during laryngoscopic maneuver. Doses of intranasal nitroglycerine used are 400, 800, and 1200 micrograms given five minutes before laryngoscopy and intubation and observed till ten minutes after laryngoscopy and intubation every minute. Patients were watched for any complication like tachycardia, hypotension, arrhythmias, bronchospasm during intra-operative and post-operative period.

Table 1

Age distribution of cases

After obtaining approval from the institutional review board, 60 patients of ASA I and II scheduled for elective surgeries under general anesthesia were subjected to the study. Informed and written consent was taken. Patients belonging to age group of 15-65 years of ASA I and II grade were included in the study.

Exclusion criteria were: Baseline heart rate <60 beats per minute, baseline blood pressure <100/50 mm of Hg, reactive airways disease, history of cardiac disease and hypertensive patient, treatment with adrenergic augmenting or depleting drug, PR interval >0.24 seconds, 2nd and/or 3rd degree heart block, contraindication to use of nitroglycerine, patient requiring two or more attempt for laryngoscopy and intubation.

Patients were randomly divided into three groups of 20 each [Table 2]. Group I received 400 micrograms, group II received 800 micrograms, and group III received 1200 micrograms of intranasal nitroglycerine spray five minutes before laryngoscopy and intubation [Table 3].

Table 2

Sex distribution

Table 3

Weight distribution

All the patients were properly evaluated preoperatively. The procedure was explained to the patient, and patients were preloaded with crystalloid fluid, 8-10 ml/kg. All the patients were pre-medicated with inj. glycopyrolate 0.04 mg/kg.i.v, inj. ondansetron 0.15 mg/kg i.v., and inj. fentanyl 1 microgm/kg. Heart rate, systolic and diastolic blood pressure were recorded before pre-medication and 10 minutes after pre-medication in patients.

With patient in supine position, nitroglycerine spray was administered intranasally five minutes before laryngoscopy and intubation. Heart rate, systolic and diastolic blood pressure were recorded after 1.5 minutes of nitroglycerine spray administration in patient. Patients were induced with inj. pentothal (6-7 mg/kg) i.v. and inj. suxamethonium (2 mg/kg) i.v. followed by laryngoscopy and intubation. Variables to be monitored were heart rate, systolic blood pressure, diastolic blood pressure, spo2, and ECG morphology.

All parameters were recorded at following stages:

Before pre-medication (BPM);

After pre-medication (APM);

30 seconds after endotracheal intubation (AEI).

And then, every one minute to up to 10 minute (AEI).

All intubation were accomplished within 15 seconds by an expert anesthesiologist. Only one attempt of intubation was accepted in the study. Patients who had coughed or bucked during procedure were excluded from study. After intubation, patients were maintained with isoflurane (0.4% v/v) or sevoflurane (0.8% v/v), O2 (50%), N2o (50%), and non-depolarizing muscle relaxant. At the end of surgery, patients were reversed with inj. glycopyrolate and inj. neostigmine. Patients were watched for any complication like tachycardia, hypotension, arrhythmias, bronchospasm during intra-operative and post-operative period.

DISCUSSION

In our study, we found that baseline mean heart rate in group I (400 micrograms) was 87.00 ± 6.72, in group II was 88.50 ± 6.83, and in group III was 88.8 ± 8.04. Results that there was no significant difference (P = 0.668) in heart rate between the three groups in pre-induction period. There was highly significant (P = 0.0001) increase in heart rate as compared to base line values in all three groups after laryngoscopy and intubation, which came to baseline values by 10th minute post-laryngoscopy and intubation. Group I showed 13.8% increase, group II showed 18.18% increase, and group III showed 23.86% increase in heart rate. Group III showed maximum increase in heart rate when compared to group I and group II. All the three groups had increase in heart rate. The mean arterial pressure which increased initially came down to baseline value by four minutes and significant hypotension was seen by ten minutes post intubation in all the three groups [Table 4].

Table 4

Heart rate changes (Mean±SD)

There was significant increase in systolic blood pressure in all three groups immediately after laryngoscopy and intubation compared to baseline value, which came back to baseline value by 4th minute post-laryngoscopy and intubation. Significant hypotension (P < 0.05) was seen in all three groups compared to baseline value from 5th minute to 10th minute. Group I showed 11.2% decrease, group II showed 12.19% decrease, and group III showed 19.6% decrease in systolic blood pressure. Maximum hypotension was seen in group III [Table 5].

Table 5

Systolic blood pressure changes (Mean±SD)

There was significant increase in diastolic blood pressure in all three groups immediately after laryngoscopy and intubation compared to baseline value, which came back to baseline value by 3rd minute post-laryngoscopy and intubation. Significant hypotension (P < 0.05) was seen in all three groups compared to baseline value from 4th to 10th minute. Group I showed 24.3% decrease, group II showed 27.27% decrease, and group III showed 30.76% decrease in diastolic blood pressure. Maximum hypotension was seen in group III [Table 6].

Table 6

Diastolic blood pressure changes (Mean±SD)

There was significant increase in mean arterial pressure in all three groups immediately after laryngoscopy and intubation compared to baseline value, which came back to baseline value by 3th minute post-laryngoscopy and intubation. Significant hypotension (P < 0.05) was seen in all three groups compared to baseline value from 5th minute to 10th minute. Group I showed 19.14% decrease, group II showed 20.65% decrease, and group III showed 25.53% decrease in mean arterial pressure. Maximum hypotension was seen in group III [Table 7].

Table 7

Mean arterial pressure changes (Mean±SD)

Two cases in group III developed hypotension, which required intervention in the form of intravenous fluids and inotropes.

This coincides with study done by Fassoulaki A, Kaniaris P. in 1983. He studied intranasal administration of nitroglycerine (NTG) in 35 adult female patients one min before the induction of anesthesia. Systolic arterial pressure (SAP) and heart rate (HR) were recorded before the induction of anesthesia and at 0, 3, and 5 min after tracheal intubation. SAP did not increase significantly in the NTG group immediately after intubation, while significant decreases in SAP were observed at 3 and 5 min (P > 0.005 and P < 0.001, respectively). SAP did increase significantly in the control group. HR was increased in both groups immediately after intubation (P < 0.001 and P < 0.001, respectively).[1] Three cases had hypotension, which required i.v. fluids and inotropic support.

Dini’sh Sood et al. in 2003 studied 50 normotensive patients belonging to ASA grade I and II, aged 20 to 45 years and body weight 35 to 65 kg, scheduled for elective surgical procedure under G A. and had concluded that intranasal 0.75 mg NTG administration 30 seconds before induction attenuate the pressure response to laryngoscopy and intubation in normotensive healthy patient.[23]

In our study, we found that all the three doses (400, 800, and 1200 micrograms) of intranasal nitroglycerine were effective in attenuating the pressor response to laryngoscopy and intubation. We found out that all the three doses caused tachycardia and hypotension after intubation. We also found that 1200 micrograms intranasal nitroglycerine spray caused maximum tachycardia and hypotension after laryngoscopy and intubation

We conclude that all the three doses of intranasal nitroglycerine spray (400, 800, and 1200 micrograms) attenuated the pressor response to laryngoscopy and intubation. There was rise in HR in all the three groups; maximum seen in group III, seen one minute after laryngoscopy and intubation, which returned to baseline by 10th minute post-laryngoscopy and intubation. There was fall in systolic, diastolic, and mean arterial BP in all the three groups; maximum fall was seen in group III around 10th minute after laryngoscopy and intubation.

Best results of attenuation of pressor response to laryngoscopy and intubation was seen with 400 and 800 micrograms of intranasal nitroglycerine spray. As the dose of 1200 micrograms of intranasal nitroglycerine spray caused maximum increase in HR and maximum decrease in SBP, DBP, and mean arterial BP, and two cases of significant hypotension, which required intervention, it is advisable to use it with caution in attenuation of laryngoscopy and intubation.