Haemodynamic changes and heart rate variability during midazolam‐propofol co‐induction*

Abstract

SummaryIn a prospective, blind, randomised study, we examined the effects of midazolam-propofol co-induction on haemodynamic (blood pressure, heart rate and stroke volume) and heart rate variability. The latter was measured by spectral analysis using the maximum-entropy method to calculate the following: the low frequency component (LF), which reflects both the cardiac sympathetic and parasympathetic activity, the high frequency component (HF) and entropy, which reflects the cardiac parasympathetic activity, the total power (TP), calculated by the addition of LF and HF, and the LF ⁄ HF ratio, which reflects the balance between the cardiac sympathetic and parasympathetic nervous activity. Forty patients were randomly allocated to the propofol group and the midazolam-propofol group, and the parameters described above were calculated at baseline (T1), post induction (T2), after tracheal intubation (T3), and 3 min (T4) and 5 min after intubation (T5). Propofol was administered at 2.5 mg.kg )1 in the propofol group and midazolam at 0.1 mg.kg )1 followed by propofol at 1.5 mg.kg )1 in the midazolam-propofol group for anaesthesia induction. Then, propofol was administered at 4-6 mg.kg )1 propofol for maintenance in both groups. The midazolam-propofol group showed compensated haemodynamic changes, which were related to significant increases in the LF ⁄ HF ratio at T2, T4 and T5 (p = 0.011, 0.038 and 0.034). These results suggest that the midazolam-propofol combination yielded compensated modulatory effects on the cardiovascular system, including preserved baroreflex activity. Combined induction (co-induction) refers to the administration of a small dose of a sedative or anaesthetic agent prior to the induction of anaesthesia, with the aim of achieving more specific 'target' responses, while minimising side-effects. Co-induction with midazolam and propofol has been mainly studied in relation to the drugs' synergistic hypnotic actions of the drugs and haemodynamic changes [1-4] during induction of anaesthesia, but there are no reports to date of the haemodynamic changes occurring during tracheal intubation. Propofol decreases the arterial blood pressure, associated with a decrease of the cardiac output ⁄ index, stroke volume index, and systemic vascular resistance [5]; on the other hand, the cardiac output ⁄ index and ventricular filling pressures are maintained after the administration of midazolam [5,6]. The autonomic nervous system exerts important neural control on the heart for maintaining cardiovascular stability. Previous studies have evaluated the effects of propofol [7][8][9][10] and midazolam [11][12][13] on the cardiac autonomic nervous system by means of heart rate variability (HRV) analysis, a non-invasive technique [14][15][16]. There are, however, no reports on simultaneous analysis of the changes of the stroke volume and HRV during midazolam-propofol co-induction. The aim of this study was to investigate the haemodynamic changes and heart rate variability during midazolam co-induction with propofol as comp...

Effects of aging and propofol on the cardiovascular component of the autonomic nervous system

“…The results of this study in younger patients were in agreement with previous reports that used propofol as the sole induction or sedation agent [13][14][15][16][17][18][19]. These reports described a significant increase in the LF/HF ratio, indicating sympathetic predominance during propofol administration.…”

“…These reports described a significant increase in the LF/HF ratio, indicating sympathetic predominance during propofol administration. Sympathetic predominance is attributed to 1) an increase in LFnorm with a concomitant decrease in HFnorm, indicating sympathetic enhancement and parasympathetic depression, respectively [13,14]; 2) a significant decrease in HFnorm, ie, parasympathetic withdrawal [15,16]; or 3) a significant decrease in both LFnorm and HFnorm, with more decrements in HFnorm that demonstrated a generalized depressive effect on ANS activity, where sympathetic outflow was less affected than parasympathetic activity [17,18]. Our results support the first mechanism of sympathetic predominance during propofol administration.…”

Effects of stellate ganglion block on cardiovascular reaction and heart rate variability in elderly patients during anesthesia induction and endotracheal intubation

“…HRV can be used to predict sudden cardiac death, evaluate the activity and balance of cardiac autonomic nervous functions, and determine relevant pathologic states [26,27]. The parameter has important clinical value and is considered the best noninvasive approach to evaluating cardiac autonomic nervous functions [28,29]. Therefore, monitoring and analyzing HRV at multiple time points during anesthesia induction provide more information with which to better understand the functional status of the cardiovascular system of elderly patients.…”

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“…This decrease, however, can be subsequent to applying local anesthetic and blocking the transmission of the stimulus. Furthermore, midazolam can cause a decrease in SAP even when administered isolated . In a study with howler monkeys, associating ketamine S(+) with midazolam reduced the SAP values throughout the procedure when comparing to the initial moment; however, this first measurement was done with the animal awake, presenting high levels of stress and, consequently, higher levels of circulating catecholamines …”