A new modality in nonstress testing: evaluation of beat-to-beat fetal heart rate variability

The vagus nerve and the inflammatory reflex: wandering on a new treatment paradigm for systemic inflammation and sepsis

BACKGROUND

The immune system protects the host against dangerous pathogens and toxins. The central nervous system is charged with monitoring and coordinating appropriate responses to internal and external stimuli. The inflammatory reflex sits at the crossroads of these crucial homeostatic systems. This review highlights how the vagus nerve-mediated inflammatory reflex facilitates rapid and specific exchange of information between the nervous and immune systems to prevent tissue injury and infection.

METHODS

Review of the pertinent English-language literature. Nearly two decades of research has elucidated some of the essential anatomic, physiologic, and molecular connections of the inflammatory reflex. The original descriptions of how these key components contribute to afferent and efferent anti-inflammatory vagus nerve signaling are summarized.

RESULTS

The central nervous system recognizes peripheral inflammation via afferent vagus nerve signaling. The brain can attenuate peripheral innate immune responses, including pro-inflammatory cytokine production, leukocyte recruitment, and nuclear factor kappa β activation via α7-nicotinic acetylcholine receptor subunit-dependent, T-lymphocyte-dependent, vagus nerve signaling to spleen. This efferent arm of the inflammatory reflex is referred to as the "cholinergic anti-inflammatory pathway." Activation of this pathway via vagus nerve stimulation or pharmacologic α7 agonists prevents tissue injury in multiple models of systemic inflammation, shock, and sepsis.

CONCLUSIONS

The vagus nerve-mediated inflammatory reflex is a powerful ally in the fight against lethal tissue damage after injury and infection. Further studies will help translate the beneficial effects of this pathway into clinical use for our surgical patients.

The pulse of inflammation: heart rate variability, the cholinergic anti-inflammatory pathway and implications for therapy

Biological therapeutics targeting TNF, IL-1 and IL-6 are widely used for treatment of rheumatoid arthritis, inflammatory bowel disease and a growing list of other syndromes, often with remarkable success. Now advances in neuroscience have collided with this therapeutic approach, perhaps rendering possible the development of nerve stimulators to inhibit cytokines. Action potentials transmitted in the vagus nerve culminate in the release of acetylcholine that blocks cytokine production by cells expressing acetylcholine receptors. The molecular mechanism of this cholinergic anti-inflammatory pathway is attributable to signal transduction by the nicotinic alpha 7 acetylcholine receptor subunit, a regulator of the intracellular signals that control cytokine transcription and translation. Favourable preclinical data support the possibility that nerve stimulators may be added to the future therapeutic armamentarium, possibly replacing some drugs to inhibit cytokines.

Antepartum nonstress fetal heart rate monitoring: systematic analysis of baseline patterns and decelerations as an adjunct to reactivity in the prediction of fetal risks

A total of 1552 antepartum nonstress tests performed during the week before delivery are analyzed with respect to both reactivity and the presence of pathologic baseline patterns (tachycardia, bradycardia, diminished beat-to-beat variability) or decelerations. Correlation with mode of delivery and condition of the newborn infant shows that, irrespective of nonstress test reactivity, the presence of baseline anomalies and/or decelerations is associated with significantly increased perinatal morbidity and mortality. Nonstress test analysis, if systematic, that is, not restricted to reactivity alone, makes it possible to better detect fetuses at high perinatal risk, in which case closer surveillance would be indicated.

The nonstress test as a diagnostic test: a critical reappraisal

In the past decade the nonstress test has become a major method of assessing high-risk pregnancy. Although many studies have been published, there has been a lack of rigorous adherence to the standard criteria for diagnostic testing, that is, presentation of test specificity, sensitivity, predictive value, and the prevalence of abnormal outcomes in the populations studied. Furthermore, the populations studied vary widely in composition, testing conditions, methods of test interpretation, and clinical management. The authors undertake a review of these studies, with a focus on these issues, in an attempt to indicate potential problems involved in current test usage and to suggest avenues for needed clinical investigation.

Comprehensive fetal monitoring by microcomputer--a clinical approach

An inexpensive microcomputer has been devised to analyze fetal heart signals and fetal activity which were simultaneously recorded. Digital techniques were used to provide quantitative analysis of each of these inputs, and the interrelations among them. A parallel graphical presentation of those inputs was also provided.

Short-term variability assessment from abdominal electrocardiogram during the antepartum period

One hundred eighty-eight patients undergoing antepartum fetal heart rate (FHR) monitoring with abdominal fetal electrocardiogram (ECG) technique were studied with respect to FHR variability derived from fetal R-R intervals. Statistically significant positive correlation existed between various measures of FHR variability and accelerations per minute (p less than 0.01). Insufficient numbers of positive contraction stress tests (CST) were available to establish a relationship with variability, although a trend existed between positive CST and low variability. Postdate pregnancies had significantly higher variability than nonpostdate pregnancies (p less than .05). This mathematical analysis establishes statistical significance between short-term variability and accelerations per minute and application of this technique for assessment of true variability in antepartum testing is possible.

Short term variability of fetal heart rate during insulin-dependent diabetic pregnancies

The clinical significance of quantified short term variability of antepartal fetal heart rate (FHR) in prediction of fetal distress in labor was assessed in 120 insulin-dependent diabetic pregnancies. FHR was recorded by abdominal fetal electrocardiography (aFECG), from which the differential indices (DI) describing the short term variability of FHR were analyzed by a microprocessor-based on-line method. The analysis was successful in 308 of 350 trials (87%). In ten pregnancies, no acceptable a FECG was obtained. Fetal distress developed in 28 of the 110 pregnancies with successful FHR analysis. There were no intrauterine deaths in this series, but two newborn infants died (perinatal mortality 1.7%). Ninety-three pregnancies with FHR analyses within one week of delivery were included in the assessment of the test. DI predicted 2 of the 17 cases of fetal distress (sensitivity 67%). Twelve of the 18 cases with a pathological DI developed fetal distress (predictive value 71%). DIs were normal in 67 of the 73 pregnancies without fetal distress (specificity 92%). Risk of fetal distress after a pathological DI was 8.5 times that after normal DIs (relative risk), which is highly significant.