Intervention Affecting Autonomic Nervous System Clinical Trial
The purpose of this study is to measure the variations of autonomic nervous system (ANS) modulation directed to the heart and vessels induced by pneumoperitoneum and steep trendelenburg position.
The association of pneumoperitoneum and steep trendelenburg position, commonly used during
laparoscopic radical prostatectomy, leads to significant changes in hemodynamics. Many
studies found modifications of cardiac output, stroke work index, arterial pressure, central
vein pressure and wedge pressure. Moreover, there are reports of severe bradycardia and
cardiac arrest following pneumoperitoneum in association with steep trendelenburg. A vagal
hypertone (induced by the combination of these two factors) or sympathetic hypractivity
(elicited by pneumoperitoneum) had been alternatively postulated to cause these hemodynamic
changes. To date there are not sufficient physiologic evidences of modification of ANS
activity during steep trendelenburg position in association with pneumoperitoneum.
ANS modulation is studied non invasively by means of heart rate variability and baroreflex
sensitivity. Beat-to-beat intervals are computed detecting the QRS complex on the ECG and
locating the R-apex using parabolic interpolation. The maximum arterial pressure within each
R-to-R interval is taken as systolic arterial pressure (SAP). Sequences of 300 values are
randomly selected inside each experimental condition. The power spectrum is estimated
according to a univariate parametric approach fitting the series to an autoregressive model.
Autoregressive spectral density is factorized into components each of them characterized by
a central frequency. A spectral component is labeled as LF if its central frequency is
between 0.04 and 0.15 Hz, while it is classified as HF if its central frequency is between
0.15 and 0.4 Hz. The HF power of R-to-R series is utilized as a marker of vagal modulation
directed to the heart , while the LF power of SAP series is utilized as a marker of
sympathetic modulation directed to vessels. The ratio of the LF power to the HF power
assessed from R-to-R series is taken as an indicator simpatho-vagal balance directed to the
heart. Baroreflex control in the low frequencies is computed as the square root of the ratio
of LF(RR) to LF(SAP). Similarly baroreflex control in the high frequencies is defined as the
square root of the ratio of HF(RR) to HF(SAP).
The optic nerve sheet's diameter is assessed echographically after induction of general
anesthesia and at the end of the surgery.
Management of general anesthesia is standardized:
- induction with propofol 1.5-2 mg/kg, Remifentanil Target Controlled Infusion (TCI) Ce 4
ng/ml , neuromuscolar blockade with cisatracurium 0.2 mg/kg.
- Maintenance: Sevoflurane 0.6-1.5 MAC (State Entropy target: 40-60); Remifentanil TCI
(range Ce 3-15 ng/ml) (Surgical Pleth Index target: 20-50).
- mechanical ventilation at respiratory rate ≥14 breats/min, with tidal volume adjusted
to maintain end-tidal carbon dioxide at 32-38 mmHg, and Pplateu <32 cmH2O.
Sample size:
to detect a difference in LF/HF ratio of 0.8 with a SD of 1.7, a power of 0.80 and type I
error of 0.05, 37 patients are needed.
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Observational Model: Cohort, Time Perspective: Prospective
| Status | Clinical Trial | Phase | |
|---|---|---|---|
| Completed |
NCT02324478 -
Exploration of Autonomic Nervous System by Photoplethysmography
|
N/A |