Effects of sevoflurane on sympathetic neurotransmission in human omental arteries and veins

Autonomic Responses during Labor: Potential Implications for Takotsubo Syndrome

Takotsubo syndrome is a serious complication of labor. Although the pathophysiologic role of excessive sympathetic activation is established in this process, concurrent vagal responses have not been adequately described. Moreover, it remains unclear whether autonomic activity depends on the mode of delivery. Here, we explored the hypothesis that the different management of cesarean and vaginal delivery may elicit diverse responses affecting both autonomic arms. For this aim, continuous electrocardiographic recording was performed in 20 women during labor, and non-invasive indices of sympathetic and vagal activity were compared between the two modes of delivery. We report sympathetic prevalence during cesarean delivery, caused by marked vagal withdrawal, whereas autonomic activity was rather stable during vaginal delivery. These differences may be attributed to the effects of anesthesia during cesarean delivery, along with the protective effects of oxytocin administration during vaginal delivery. Our results provide further insights on autonomic responses during labor that may prove useful in the prevention of complications, such as takotsubo syndrome.

Role of Renal Sympathetic Nerve Activity in Volatile Anesthesia's Effect on Renal Excretory Function

Regulation of fluid balance is pivotal during surgery and anesthesia and affects patient morbidity, mortality, and hospital length of stay. Retention of sodium and water is known to occur during surgery but the mechanisms are poorly defined. In this study, we explore how the volatile anesthetic sevoflurane influences renal function by affecting renal sympathetic nerve activity (RSNA). Our results demonstrate that sevoflurane induces renal sodium and water retention during pediatric anesthesia in association with elevated plasma concentration of renin but not arginine-vasopressin. The mechanisms are further explored in conscious and anesthetized ewes where we show that RSNA is increased by sevoflurane compared with when conscious. This is accompanied by renal sodium and water retention and decreased renal blood flow (RBF). Finally, we demonstrate that renal denervation normalizes renal excretory function and improves RBF during sevoflurane anesthesia in sheep. Taken together, this study describes a novel role of the renal sympathetic nerves in regulating renal function and blood flow during sevoflurane anesthesia.

May sevoflurane prevent the development of neurogenic pulmonary edema and improve the outcome? Or as a new sedation method for severe brain injury patients

Neurogenic pulmonary edema (NPE) is a life-threatening complication that develops rapidly and dramatically after injury to the central nervous system (CNS). Severe primary brain injury and subsequent secondary brain injury cascade events are thought to be involved in the development of NPE. Activation of the sympathetic nervous system and release of vasoactive substances are also essential prerequisites for NPE. We hypothesize that sevoflurane may be an effective treatment for preventing the development of NPE. Sevoflurane may play a role in protecting brain and lung tissue after acute brain injury through its sympatholytic, antioxidative, ion channel stabilizing, anti-inflammatory, anti-apoptotic, and pulmonary protection effects. It has the potential to be used as a sedative in the neurosurgical intensive care unit (NICU), which can help maintain nervous system and cardiopulmonary function in patients with acute brain injury to improve prognosis. Sevoflurane also has the advantages of fast induction of anesthesia, rapid drug metabolism, little interference to the cardiovascular system, and controllable depth of anesthesia. If our hypothesis is supported by further experiments, use of sevoflurane may open a new door for the treatment of acute brain injury and NPE.

Propofol Attenuates the Myocardial Protection Properties of Desflurane by Modulating Mitochondrial Permeability Transition

BACKGROUND

Desflurane and propofol are cardioprotective, but relative efficacy is unclear. The aim was to compare myocardial protection of single, simultaneous, and serial administration of desflurane and propofol.

METHODS

Sixty New Zealand White rabbits and 65 isolated Sprague Dawley rat hearts randomly received desflurane, propofol, simultaneous desflurane and propofol, or sequential desflurane then propofol. Rabbits were subdivided to receive either ischemia-reperfusion with temporary occlusion of the left anterior descending artery or a time-matched, nonischemic perfusion protocol, whereas rat hearts were perfused in a Langendorff model with global ischemia-reperfusion. End points were hemodynamic, functional recovery, and mitochondrial uptake of H-2-deoxy-D-glucose as an indicator of mitochondrial permeability transition.

RESULTS

In rabbits, there were minimal increases in preload-recruitable stroke-work with propofol (P < .001), desflurane (P < .001), and desflurane-and-propofol (P < .001) groups, but no evidence of increases with pentobarbitone (P = .576) and desflurane-then-propofol (P = .374). In terms of end-diastolic pressure-volume relationship, there was no evidence of increase compared to nonischemic controls with desflurane-then-propofol (P = .364), a small but significant increase with desflurane (P < .001), and larger increases with pentobarbitone (P < .001), propofol (P < .001), and desflurane-and-propofol (P < .001).In rat hearts, there was no statistically significant difference in mitochondrial H-activity between propofol and desflurane-and-propofol (165 ± 51 × 10 vs 154 ± 51 × 10 g·mL·min/μmol; P = .998). Desflurane had lower uptake than propofol (65 ± 21 × 10 vs 165 ± 51 × 10 g·mL·min/μmol; P = .039), but there was no statistically significant difference between desflurane and desflurane-then-propofol (65 ± 21 × 10 vs 59 ± 11 × 10 g·mL·min/μmol; P = .999).

CONCLUSIONS

Propofol and desflurane are cardioprotective, but desflurane is more effective than propofol. The added benefit of desflurane is lost when used simultaneously with propofol.

Changes of dorsalis pedis artery flow pattern after caudal block in children: observational study using a duplex sonography

OBJECTIVE

To evaluate the changes of the flow velocity, the volume flow, and the diameter of dorsalis pedis artery using a duplex ultrasonography after caudal block with sevoflurane anesthesia in children.

AIM

To know the acute change in peripheral arterial flow patterns of sympathetically blocked lower limbs in anesthetized children.

BACKGROUND

Caudal analgesia in combination with general anesthesia may affect the circulatory hemodynamics due to sympatholytic vasodilating effects.

METHODS

After approval by the Ethics Committee, we evaluated the changes of peripheral hemodynamics using a duplex ultrasonography before and after a caudal block in sevoflurane-anesthetized children.

RESULTS

A caudal block using 0.15% ropivacaine 1.5 ml·kg(-1) significantly altered the arterial flow patterns; increased peak velocity (24%) and volume flow (76%), and the diameter of the dorsalis pedis artery (20%) in children. However, blood pressures and heart rates were not affected significantly by caudal block.

CONCLUSIONS

Duplex sonographic measurements indicate that a caudal block changes the flow patterns of the dorsalis pedis artery significantly in the anesthetized children.

Hemodynamic differences between propofol-remifentanil and sevoflurane anesthesia for repair of cleft lip and palate in infants

BACKGROUND

Propofol-remifentanil anesthesia is widely used in adults but few studies are available in infants. We aimed at comparing the hemodynamic effects of propofol-remifentanil vs sevoflurane-fentanyl anesthesia. In addition, we sought to investigate recovery and whether remifentanil induced acute opioid tolerance.

METHODS

In total, 39 infants 4-6 months old were prospectively enrolled and randomized to receive either a combination of remifentanil and propofol (n = 17) or a sevoflurane-fentanyl anesthesia (n = 22) for surgical repair of cleft lip and palate. In both groups, sevoflurane was used for induction of anesthesia and fentanyl was administered before tracheal extubation. Mean arterial blood pressure and heart rate were recorded every 5 min after induction. We also recorded time from termination of surgery to tracheal extubation, postoperative behavior and the need for analgesia for the first 24 h after surgery. Postoperative observations were blinded.

RESULTS

In the remifentanil-propofol group, the mean arterial blood pressure was higher [58 (51-65) vs 51 (45-55), P = 0.02] and the mean heart rate was lower [111 (108-113) vs 128 (122-143), P < 0.0001]. There were no differences in recovery time or behavior after surgery. In the remifentanil group, a median fentanyl dose of 4 microg x kg(-1) was required to insure a smooth recovery, but there was no difference in morphine consumption during the first 24 h after surgery.

CONCLUSIONS

A high-dose remifentanil-propofol infusion was associated with a higher blood pressure and lower heart rate than sevoflurane-fentanyl anesthesia in infants. Postoperative morphine consumption, recovery time and quality were similar.

Sevoflurane promotes endothelium-dependent smooth muscle relaxation in isolated human omental arteries and veins

Anesthesia with sevoflurane is accompanied by vasodilatation. This could be due to the effects of sevoflurane on endothelium-dependent relaxation. We measured muscle tension of isolated human omental arteries and veins in response to substance P or glyceryl trinitrate in the presence of sevoflurane (0%, 1%, 2%, or 4%). Vascular levels of guanosine 3', 5'-cyclic monophosphate were measured with enzyme-linked immunosorbent assay. Substance P induced an endothelium- and concentration-dependent relaxation in omental vessels that was not affected by sevoflurane. In the presence of L-N(G)-nitroarginine methyl ester (nitric oxide synthase inhibitor), KCl (prevention of hyperpolarization), or both, sevoflurane at 4% enhanced the relaxation in the arteries (P < 0.05). In the vein segments, the relaxation was enhanced by sevoflurane at 4% in the presence of KCl and 2% and 4% in the presence of both L-N(G)-nitroarginine methyl ester and KCl (P < 0.05). The glyceryl trinitrate-induced endothelium-independent relaxation was enhanced by sevoflurane at 4% in both artery and vein segments (P < 0.05). Substance P increased the levels of guanosine 3', 5'-cyclic monophosphate similarly in the presence and absence of sevoflurane. These results show that sevoflurane, in contrast to its effect in animal models, promotes endothelium-dependent relaxation in human omental arteries and veins via an enhancement of the smooth muscle response to relaxing second messengers.