Sympathovagal Effects of Spinal Anesthesia Assessed by the Spontaneous Cardiac Baroreflex 

Abstract

Using a noninvasive, continuous technique to estimate cardiac sympathovagal balance, no significant variation in autonomic balance induced by spinal anesthesia was observed. However, untoward episodes of bradycardia and hypotension occurred in three patients, who could not be prospectively identified by the parameters studied.

Unusual sinus arrhythmia

“…Furthermore, during syncope, a large sinus arrhythmia (range: 30-95 bpm) occurred [21]. The oscillation between bradycardia and tachycardia lasted one beat [21], as here. Present kinetics is compatible with bursts of vagal activity.…”

“…Bradycardia occurred during expiration within one beat [20]: thus bradycardia was thought to be linked to bursts of vagal activity [20]. Furthermore, during syncope, a large sinus arrhythmia (range: 30-95 bpm) occurred [21]. The oscillation between bradycardia and tachycardia lasted one beat [21], as here.…”

Intrathecal drug spread

“…Hypotension and bradycardia are related to block height, but again are too non-specific. Vasomotor responses 47 can be used to detect neuronal integrity, and can be detected by colour and temperature changes in the affected area using thermography, 26 but are less reliable signs 39 and occur at a higher level of block than sensory changes. 26 The vasoconstrictive response in the skin of the upper limb to both pinprick and cold stimulation has been claimed to be a good indicator of block height, 60 although whether it offers anything over subjective response to sensory stimulation is unclear.…”

Parada cardiorrespiratória em raquianestesia

“…usually, the reduction in lv end-diastolic volume results in reduction in the activity of those receptors, but a fast reduction in ventricular volume can stimulate and increase activity in those receptors, leading to bradycardia. those three reflexes have in common the fact that the effector arms of each one involves an increase in vagal tonus 3-5, [19][20][21][22]26,28 .…”