Research Departments & Organizations
I am presently undertaking several major areas of research.
- I am seeking to get a better insight into regulation of blood flow at the level of the capillaries and tissues, with an emphasis on assessing how this is controlled by the autonomic nervous system.
- Detecting when somebody is dehydrated or is losing blood before the change in volume status can cause significant harm to the body.
- New means of monitoring body temperature through a surface temperature monitor.
- Developing a common score for assessing the local impact of disorders, the systemic impact of disorders, and the impact of challenges such as surgery.
Specialized Terms: Anesthesiology; Cardiovascular System; Congestive Heart Failure; Headaches; Heart; Hypertension; Ischemia; Neuromuscular Disorders; Pain; Perfusion Or Reperfusion; Circulation; Circulatory Disorders; Endothelial Dysfunction; Healthcare Worker Safety; Hypovolemia; Microcirculation; Needle Safety; Needlesticks; Neuromuscular System; Neuromuscular Disorders
Extensive Research Description
1. Using a multi-dimensional computerized data acquisition system, we are integrating input from arterioles and capillaries (laser Doppler flowmetry), arteries and veins (plethysmography), with continuous monitors of blood pressure and heart rate to gain insight into two major areas of cardiovascular physiology: a) the regulation of microvascular perfusion, with a focus on autonomically-mediated autoregulatory processes; b) the assessment of the cardiovascular responses to volume loss intraoperatively and in healthy volunteers (withdrawal and reinfusion of two units of blood; simulated hypovolemia with the use of lower body negative pressure). These studies involve time-domain and spectral-domain analytical techniques in collaborative efforts with Cardiology, Emergency Medicine, Pulmonary Medicine, and Physiology at Yale and the J.B. Pierce Foundation as well as with Chairman of Biomedical Engineering at another institution. The work has led to intellectual property that has been transferred to Yale University School of Medicine.
2. As Co-Director of the BTT Interdisciplinary Research Group, I am the senior investigator on a series of multidisciplinary, multicenter studies monitoring brain and core temperature noninvasively. In collaboration with Dr. Marc Abreu, the discoverer of the brain thermal tunnel (BTT) and inventor of related technology, I h ave been determining the ability to continuously monitor core and, more specifically, brain temperature, with a noninvasive surface sensor applied beneath the medial brow ridge. Our initial studies have focused on whether BTT is an accurate measure of brain temperature and a reliable detector of brain/core discordance. We thereby haveidentified (and quantified) changes in brain temperature during anesthesia and throughout the perioperative period. For example, we identified otherwise unseen brain hyperthermia (with the potential for neuronal injury) during recovery from cardiopulmonary bypass surgery. In the emergency setting, we documented otherwise undetected ipsilateral hypothermia during incipient ischemic stroke, leading to likely application of BTT as a harbinger of brain loss. Monitoring via the BTT has enabled us to delineate changes during sleep, including delta and REM sleep and abnormalities thereof. We similarly have isolated changes in brain temperature during seizures, craniotomy, mental effort, ischemic stroke and exercise. Preliminary evidence suggests that monitoring BTT may enable us to more effectively identify incipient heat stroke. Such monitoring thus provides previously unattainable insight into brain thermodynamics in health and disease, constituting a hinge moment for brain as well as core thermometry -- and hence patient safety. Upon publication of our initial manuscripts (in prep), I anticipate that BTT will become required monitoring during major surgery and prove to be invaluable in myriad other hospital and nonhospital settings. The sensitivity of monitoring via the BTT to temperature channels at the level of the hypothalamus (body’s thermostat) may make it particularly valuable in detecting prodromal phases of a disorder (such as the flu) as well as active and recovery phases.
3. I have introduced a new way for uniform scoring of bodily systems and the disorders affecting them and integrating this with the anticipated risks associated with anesthesia and surgery. I am exploring ways of adapting my new method of assessment to improve the utility and workability of the electronic health record.
- Integrated assessment and consultation for the preoperative patient Silverman DG. Rosenbaum SH. Integrated assessment and consultation for the preoperative patient. Medical Clinics of North America. 93(5):963-977, 2009 Sep.
- Modeling Perioperative Risk – Can Numbers Speak Louder Than Words? Holt NF, Silverman DG: Modeling Perioperative Risk – Can Numbers Speak Louder Than Words? In: Rosenbaum SH (editor). Anesthesiology Clinics of NA 24:427-459, 2006
- The relationship between the photoplethysmographic waveform and systemic vascular resistance Awad AA. Haddadin AS. Tantawy H. Badr TM. Stout RG. Silverman DG. Shelley KH. The relationship between the photoplethysmographic waveform and systemic vascular resistance. Journal of Clinical Monitoring & Computing. 21(6):365-72, 2007 Dec.
- Comparing the effect of arginine vasopressin on ear and finger photoplethysmography Jablonka DH, Awad AA, Stout RG, Silverman DG, Shelley KH: Comparing the effect of arginine vasopressin on ear and finger photoplethysmography. Journal of Clinical Anesthesia 20:90-93, 2008
- Distinction between atropine-sensitive control of microvascular and cardiac oscillatory activity Silverman DG, Stout RG: Distinction between atropine-sensitive control of microvascular and cardiac oscillatory activity. Microvasc Res 63:196-208, 2002
- Peripheral assessment of phenylephrine-induced vasoconstriction by laser Doppler flowmetry and its potential relevance to homeostatic mechanisms Silverman DG, Jotkowitz AB, Freemer M, Gutter V, O'Connor TZ, Braverman IM: Peripheral assessment of phenylephrine-induced vasoconstriction by laser Doppler flowmetry and