European Journal of Cardiovascular Medicine

Reflex sympathetic discharge caused by epipharyngeal and laryngopharyngeal stimulation producing significant increase in heart rate and arterial pressure. The haemodynamic stress response to laryngoscopy and intubation should be attenuated to balance myocardial oxygen supply and demand especially in coronary artery disease patients. It is also hazardous in patients with cerebrovascular disease, intracranial pathology and hyperactive airways.

CARDIOVASCULAR RESPONSE:

Hypertension, tachycardia, bradycardia and dysrhythmias mediated by autonomic nervous system occurs. Hypertension, tachycardia, increase in cardiac work and oxygen consumption are mediated by sympathetic afferents via the cardioaccelerator fibres and sympathetic 8 chain ganglia. The polysynaptic pathway from 9th and 10th nerve afferents to sympathetic nervous system in the brain stem and spinal cord results in a diffuse autonomic response which includes widespread release of norepinephrine from the adrenergic terminals and release of epinephrine from the adrenal medulla.

RESPIRATORY SYSTEM:

1. Reflex glottis closure-laryngospasm
2. Decreases dead space
3. Increased airway resistance
4. Bronchospasm

STRESS RESPONSE IN PATHOLOGICAL STATES:

1. In patients with limited myocardial reserve, myocardial ischemia and failure can occur. It is essential to maintain the heart rate and blood pressure of the patient within 20% of the normal awake value. Heart rate should ideally be less than 110 beats per minute(ischemic threshold).
2. Intracranial vascular anomalies can rupture.
3. In patients with hyperactive airways bronchospasm and laryngospasm can occur.
4. Laryngoscopy and intubation can increase cerebral blood flow if autoregulation is impaired. The resultant increase in intracranial pressure can lead to brainstem herniation and death.

1.       Maintaining a deep plane of general anaesthesia using volatile anaesthetics. This dose of volatile anaesthetics required to block the cardiovascular responses to endotracheal intubation may result in profound cardiovascular depression. The volatile agents used are Halothane, Isoflurane and Sevoflurane.

2.       Local anaesthetics. Lignocaine is used. a) It is given as viscous gargle for oropharyngeal anaesthesia. b) aerosol for intratracheal anaesthesia c) intravenous d) local instillation or topical spray over the vocal cords. e) Regional nerve blocks

3.       Vasodilators –Nitroglycerine Sodium Nitroprusside Hydralazine

4.       Magnesium sulphate 11

5.       Narcotics –Fentanyl, Sufentanil, Remifentanil, Morphine, Pethidine. Fentanyl is the most commonly used narcotic.It is a potent analgesic, has a short duration of action, does not increase intracranial tension and has minimal circulatory changes.

6.       Calcium channel blockers- Nifedipine, Nicardipine, Verapamil, Diltiazem

7.       Adrenergic blockers –Beta blocker-Metoprolol, Esmolol -Alpha blocker-Phentolamine Alpha and beta blocker-Labetalol

8.       Central sympatholytics-Clonidine and Dexmedetomidine. They act by decreasing central sympathetic outflow.

9.       Sedatives and anxiolytics.

Baseline Hemodynamic Parameters

Table 1: Basal Heart Rate:

P value = 0.112. Hence there is no statistical significance in basal heart rate between the three groups.

Table 2: Basal Systolic Pressure:

P value = 0.504. Hence there is no statistical significance in basal systolic pressure between the three groups.

Table 3: Basal Diastolic Pressure:

p value = 0.707. Hence there is no statistical significance in basal diastolic pressure between the three groups.

Table 4: Basal Mean Arterial Pressure

p value = 0.544. Hence there is no statistical significance in basal mean arterial pressure between the three groups

.

Table 5: Heart Rate changes

Table 6: SYSTOLIC BLOOD PRESSURE CHANGES

Table 7: DIASTOLIC BLOOD PRESSURE CHANGES (mmHg)

Table 8: MEAN ARTERIAL PRESSURE CHANGES (mmHg)

Table 9: LARYNGOSCOPY DURATION:

Laryngoscopy and intubation can produce haemodynamic stress response charecterised by hypertension and tachycardia. It can also produce increase in intracranial pressure. No drug can attenuate this response completely. Many drugs have been reported to attenuate this response.

A.A.Vandenberg et al. 1 in October 2003, studied attenuation of haemodynamic response in Magnesium Sulphate pretreated patients undergoing cataract surgery. They compared Esmolol and MgSO4.They concluded that Esmolol 4mg/kg prevented increase in heart rate and rate pressure product. Mg SO4 40 mg/kg did not prevent response to laryngoscopy and intubation.

 SapnaBathla, Santhoshkumar et al. 4 in 2003, compared efficacy of IV Esmolol Diltiazem and Magnesium Sulphate, in attenuating haemodynamic stress response to laryngoscopy and intubation. Their study showed that MgSo4 produced tachycardia and failed to attenuate rise in heart rate. Esmolol prevented rise in heart rate though rise in blood pressure was suppressed but not prevented. 62 In our study, comparison of Esmolol 1.5mg/kg, MgSo4 50mg/kg and placebo was done in attenuating haemodynamic stress response to laryngoscopy and intubation.

The data was analysed using Microsoft Excel. Haemodynamic variables were represented by mean and standard deviation. Statistical significance was assessed by use of ANOVA and Pearson chi square test. TUKEYS HSD was applied to evaluate inter group comparisons.

P value less than 0.05 was considered as statistically significant.

From this study, it is concluded that hemodynamic changes to laryngoscopy and intubation can be attenuated by giving intravenous Esmolol 1.5mg/kg. Esmolol is effective in blunting the response followed by Magnesium Sulphate which blunts the hypertensive response but produces tachycardia during infusion of the drug.  Placebo was ineffective in blunting hemodynamic stress response to laryngoscopy and intubation.

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