The Cardiac Sympathetic Nerve Activity in the Elderly Is Attenuated in the Right Lateral Decubitus Position

Ability of the Analgesia Nociception Index variations to identify a response to a volume expansion of 250 mL of crystalloids in the operating room (REVANI): a prospective observational study

BACKGROUND

Analgesia Nociception Index (ANI) is a device based on analysis of the R-R interval and respiratory sinus arrhythmia to assess the balance between sympathetic and parasympathetic activity. The autonomic system is directly affected by load changes. Therefore, monitoring sympathetic tone and its change could theoretically allow tracking of load changes during volume expansion. The aim of the present study was to determine whether changes in ANI are able to track the increase in stroke volume caused by volume expansion (SV).

METHODS

This prospective observational study included mechanically ventilated patients undergoing neurosurgery and benefiting from SV monitoring. Exclusion criteria were cardiac dysfunction, arrhythmias, beta-blockade therapy, and dysautonomia. SV was optimized by fluid administration of 250 ml of crystalloid fluid. A positive fluid increase was defined as a SV increase of 10% or more from baseline. Changes in SV and medium ANI (ANIm) were recorded before and 4 to 5 min after volume expansion.

RESULTS

Sixty-nine patients had 104 fluid challenges (36 positive and 68 negative). Volume expansion resulted in a greater ANI increase in responders than in nonresponders. The change in ANIm > 5 predicted fluid responsiveness with a sensitivity of 68.4% (95% CI: 67.4% to 69.5%) and a specificity of 51.2% (95% CI: 50.1% to 52.3%). The area under the receiver operating characteristic curve was 0.546 (95% CI: 0.544 to 0.549) and appeared to be affected by remifentanil dose and baseline ANI.

CONCLUSION

Changes in ANIm induced by fluid challenge is not able to predict fluid responsiveness in mechanically ventilated patients undergoing neurosurgery.

TRIAL REGISTRATION

Clinical trial registration: NCT04223414.

Blanco L, Lamy J, Kachenoura N, Quesson B, Cochet H, Coronel R, Dekker LRC. A left lateral body position increases pulmonary vein stress in healthy humans

Pulmonary vein (PV) stretch is proarrhythmic for atrial fibrillation (AF). AF patients often report that a left lateral (LL) body position can trigger arrhythmia symptoms. Because the PV myocardium is thought to trigger AF, we hypothesized that the LL compared to the supine body position increases PV wall stress. Functional cardiac magnetic resonance imaging was performed in supine and LL recumbent body position in awake condition in healthy human volunteers (n = 20). Following a change from supine to LL position, the heart moved in an anterior-LL direction in the thorax. The right superior PV diameter was increased by 19% (24.6 ± 3.1 vs. 20.7 ± 3.2 mm, p = 0.009) and left atrial (LA) volume was larger by 17% (61.7[15.4] vs. 51.0[17.8] ml, p = 0.015) in LL than supine position, respectively. The passive LA conduit fraction (normalized difference between maximum and pre-contraction LA volume) increased by 25% in LL compared to supine position (19.6 ± 9.0 vs. 15.7 ± 7.6%, respectively, p = 0.016). Local wall stress in the PV regions increased in LL compared to supine position (overall mean: 1.01 ± 0.12 vs. 1.10 ± 0.10 arb. unit, LL vs. supine, position effect p = 0.041), whereas this was not the case in the LA walls (overall mean: 1.18 ± 0.31 vs. 1.21 ± 0.21 arb. unit, LL vs. supine, position effect p = 0.381). In conclusion, a left lateral body position increases PV myocardial stress during the atrial relaxation phase of healthy volunteers. These results have implications for the mechanisms of posture-triggered AF.

Self-Reported Onset of Paroxysmal Atrial Fibrillation Is Related to Sleeping Body Position

Background: Because stretch of the atrial myocardium is proarrhythmic for atrial fibrillation (AF) and a left lateral body position increases atrial dimensions in humans, we hypothesized that left lateral recumbence is a frequent AF-triggering body position in AF patients.

Methods: We performed a questionnaire study of symptomatic paroxysmal AF (episodes of AF < 1 week) patients scheduled for a first AF ablation therapy at Catharina Hospital, Eindhoven, the Netherlands and at University Hospital, Bordeaux, France.

Results: Ninety-four symptomatic paroxysmal AF patients were included [mean age 61 ± 11 years, median AF history of 29(48) months, 31% were females]. Twenty-two percent of patients reported a specific body position as a trigger of their AF symptoms. The triggering body position was left lateral position in 57% of cases, supine position in 33%, right lateral position in 10%, and prone position in 5% (p = 0.003 overall difference in prevalence). Patients with positional AF had a higher body mass index compared to patients without nocturnal/positional AF [28.7(4.2) and 25.4(5.2) kg/m², respectively, p = 0.025], but otherwise resembled these patients.

Conclusion: Body position, and the left lateral position, in particular, is a common trigger of AF in symptomatic AF patients. Moreover, positional AF is associated with overweight. Understanding of the underlying mechanisms of positional AF can contribute to AF treatment and prevention.

The effect of body posture on resting-state functional connectivity

INTRODUCTION

An important but under-investigated confound of functional MRI (fMRI) is body posture. Although it is well-established that body position changes cerebral blood flow, the amount of cerebrospinal fluid in the brain, intracranial pressure, and even the firing rate of certain cell types, there is currently no study that directly examines its effect on fMRI measurements. Moreover, fMRI is typically done in a supine position, which often does not correspond to how these processes are performed in everyday settings.

METHODS

In this study, 20 healthy adults underwent resting-state fMRI under three body positions: supine, right lateral decubitus (RLD), and left lateral decubitus (LLD). We first investigated whether there were differences in overall organization of whole-brain connectivity between conditions using graph theory. Second, we examined whether functional connectivity of two most studied default mode network (DMN) seeds to the rest of the brain was altered as a function of body position.

RESULTS

Nonparametric statistical analyses revealed that global network measures differed among conditions, with the supine and LLD showing identical results compared to the RLD. There was decreased connectivity for DMN seeds in the RLD condition compared to the supine and LLD, but there were no significant differences between the latter two conditions.

DISCUSSION

Potential mechanisms underlying these alterations include gravity, changes in physiology, and body anatomy. Our results suggest that, compared to supine and LLD, the RLD position leads to changes in whole-brain and DMN connectivity. Finally, depending on the research question, combining imaging modalities that allow for more naturalistic settings can provide a better understanding of certain phenomena.

Gender difference and laterality of sleep position

OBJECTIVE

A higher incidence in women (approximately 7:3) and a predominant involvement of the right ear (approximately 7:5) are interesting features of BPPV (benign paroxysmal positional vertigo). It is speculated that these features are related to sleep position. The first aim of this study was to compare the frequency of position shifts during sleep between men and women. The second aim was to elucidate any differences in sleep position between men and women. The third aim was to clarify the laterality of sleep position.

METHODS

We retrospectively selected the data of 30 males (mean, 53.1 years) and 22 females (mean, 50.6 years) diagnosed as mild or moderate obstructive sleep apnea. A position sensor was attached to the patient's anterior chest. Supine position was defined as less than 45° tilt, and lateral position was defined as more than 45° tilt. A single overnight laboratory polysomnography provided the number of position shifts, total sleep time, sleep time spent in the supine position (S), sleep time spent in the right-side-down lateral position (R), and sleep time spent in the left-side-down lateral position (L).

RESULTS

The mean value and standard deviation of the number of position shifts per hour was 2.4±1.3 in males, and 2.3±1.1 in females. There was no significant difference between males and females. Twelve cases (40%) were lateral type (S<R+L), and 18 (60%) were supine type (S>R+L) in males. Ten cases (45%) were lateral type, and 12 (55%) were supine type in females. There was no significant difference between males and females. Seventeen cases (56.6%) were right-dominant type (R-L>0), and 13 (43.3%) were left-dominant type (R-L<0) in males. Thirteen cases (59%) were right-dominant type, and 9 (41%) were left-dominant type in females.

CONCLUSION

Body position and the number of position shifts during sleep differ substantially between individuals. There is no gender difference in the frequency of position shifts. Although the supine type is more common than the lateral type, there is no gender difference in sleep position. Therefore, the reason of higher incidence in women is not related to sleep. The right-dominant type occurs more than the left-dominant type in both genders. It is possible that this behavior is the reason for the predominant involvement of the right ear in BPPV.