Thoracolumbar epidural anaesthesia blocks the circulatory response to laryngoscopy and intubation

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Abstract
Laryngoscopy and endotracheal intubation cause a stress reaction resulting in an increase in heart rate and systemic blood pressure. This haemodynamic response is considered to be due to a sympathetic discharge caused by stimulation of the upper respiratory tract. This stress reaction during laryngoscopy and endotracheal intubation was studied in patients with total thoracolumbar epidural anaesthesia (EDA). Nine patients with thoracolumbar EDA including at least the segments T1 to L2 were compared to seven patients without EDA during induction of general anaesthesia. The epidural anaesthesia was achieved with 2% mepivacaine with adrenaline. General anaesthesia was induced with thiopentone 4-5 mg/kg followed by 100 mg suxamethonium. The highest blood pressure value during the first 2 min after intubation was compared to the value immediately before intubation. The epidural anaesthesia caused a reduction of the mean arterial blood pressure (MAP) by 25%, and a reduction of the heart rate (HR) by 7%, but neither the induction with thiopentone nor the laryngoscopy and intubation caused any changes in mean arterial blood pressure or heart rate. However, in the control group MAP increased 29% and HR 16% following intubation. Thus, the T1-L2 epidural anaesthesia with 2% mepivacaine with adrenaline blocked the blood pressure reaction to laryngoscopy and intubation, and consequently the efferent sympathetic nervous system was completely blocked.