Direct laryngoscopy and tracheal intubation in patients with normal protective airway reflexes results in stimulation of the sympathetic nervous system. This, in turn, may lead to hemodynamic changes such as increased HR, elevated systolic BP, and cardiac arrhythmias (especially ventricular bigeminy). In the study below [image and citation needed], a comparison in healthy normotensive subjects show changes in HR and SBP during direct laryngoscopy alone (LSA), direct laryngoscopy with intubation (LSI) and light wand intubation (LSI). As you can see, HR and SBP show increases with all three interventions, however, the increases in both HR and SBP tend to be higher when tracheal intubation is achieved compared to DL alone. These hemodynamic effects may persist up to 5 minutes after the intubation.
Less commonly, bradycardia may be encountered as a vagal response to laryngoscopy. It should be noted that when larygoscopy is difficult and repeated doses of succinylcholine are used, bradycardia can be encountered. If brachycardia occurs in this context, it is thought to be the result of the accumulation of succinyl monocholine (a metabolite of succinylcholine) and not a direct result of laryngoscopy.
Laparoscopy: CV effects