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Moretti EH, Rodrigues AC, Marques BV, Totola LT, Ferreira CB, Brito CF, Matos CM, da Silva FA, Santos RAS, Lopes LB, Moreira TS, Akamine EH, Baccala LA, Fujita A, Steiner AA. Autoregulation of blood flow drives early hypotension in a rat model of systemic inflammation induced by bacterial lipopolysaccharide. PNAS NEXUS 2023; 2:pgad014. [PMID: 36874271 PMCID: PMC9982072 DOI: 10.1093/pnasnexus/pgad014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Accepted: 01/09/2023] [Indexed: 01/22/2023]
Abstract
Uncontrolled vasodilation is known to account for hypotension in the advanced stages of sepsis and other systemic inflammatory conditions, but the mechanisms of hypotension in earlier stages of such conditions are not clear. By monitoring hemodynamics with the highest temporal resolution in unanesthetized rats, in combination with ex-vivo assessment of vascular function, we found that early development of hypotension following injection of bacterial lipopolysaccharide is brought about by a fall in vascular resistance when arterioles are still fully responsive to vasoactive agents. This approach further uncovered that the early development of hypotension stabilized blood flow. We thus hypothesized that prioritization of the local mechanisms of blood flow regulation (tissue autoregulation) over the brain-driven mechanisms of pressure regulation (baroreflex) underscored the early development of hypotension in this model. Consistent with this hypothesis, an assessment of squared coherence and partial-directed coherence revealed that, at the onset of hypotension, the flow-pressure relationship was strengthened at frequencies (<0.2 Hz) known to be associated with autoregulation. The autoregulatory escape to phenylephrine-induced vasoconstriction, another proxy of autoregulation, was also strengthened in this phase. The competitive demand that drives prioritization of flow over pressure regulation could be edema-associated hypovolemia, as this became detectable at the onset of hypotension. Accordingly, blood transfusion aimed at preventing hypovolemia brought the autoregulation proxies back to normal and prevented the fall in vascular resistance. This novel hypothesis opens a new avenue of investigation into the mechanisms that can drive hypotension in systemic inflammation.
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Affiliation(s)
- Eduardo H Moretti
- Departamento de Imunologia, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Av. Prof. Lineu Prestes, 1730, Sao Paulo, SP 05508-000, Brazil
| | - Abner C Rodrigues
- Instituto Internacional de Neurociencias Edmond e Lily Safra, Instituto de Ensino e Pesquisa Alberto Santos Dumont, Macaiba, RN 59288-899, Brazil
| | - Bruno V Marques
- Departamento de Farmacologia, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Sao Paulo, SP 05508-000, Brazil
| | - Leonardo T Totola
- Departamento de Fisiologia e Biofisica, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Sao Paulo, SP 05508-000, Brazil
| | - Caroline B Ferreira
- Departamento de Farmacologia, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Sao Paulo, SP 05508-000, Brazil.,Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213-2548, USA
| | - Camila F Brito
- Departamento de Imunologia, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Av. Prof. Lineu Prestes, 1730, Sao Paulo, SP 05508-000, Brazil
| | - Caroline M Matos
- Departamento de Imunologia, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Av. Prof. Lineu Prestes, 1730, Sao Paulo, SP 05508-000, Brazil
| | - Filipe A da Silva
- Departamento de Fisiologia e Biofisica, Instituto de Ciencias Biologias, Universidade Federal de Minas Gerais, Belo Horizonte, MG 31270-901, Brazil
| | - Robson A S Santos
- Departamento de Fisiologia e Biofisica, Instituto de Ciencias Biologias, Universidade Federal de Minas Gerais, Belo Horizonte, MG 31270-901, Brazil
| | - Luciana B Lopes
- Departamento de Farmacologia, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Sao Paulo, SP 05508-000, Brazil
| | - Thiago S Moreira
- Departamento de Fisiologia e Biofisica, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Sao Paulo, SP 05508-000, Brazil
| | - Eliana H Akamine
- Departamento de Farmacologia, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Sao Paulo, SP 05508-000, Brazil
| | - Luiz A Baccala
- Departamento de Engenharia de Telecomunicacoes e Controle, Escola Politecnica, Universidade de Sao Paulo, Sao Paulo, SP 05508-900, Brazil
| | - André Fujita
- Departamento de Estatistica, Instituto de Matematica e Estatistica, Universidade de Sao Paulo, Sao Paulo, SP 05508-090, Brazil
| | - Alexandre A Steiner
- Departamento de Imunologia, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Av. Prof. Lineu Prestes, 1730, Sao Paulo, SP 05508-000, Brazil
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Deep learning and computer vision techniques for microcirculation analysis: A review. PATTERNS (NEW YORK, N.Y.) 2022; 4:100641. [PMID: 36699745 PMCID: PMC9868679 DOI: 10.1016/j.patter.2022.100641] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
The analysis of microcirculation images has the potential to reveal early signs of life-threatening diseases such as sepsis. Quantifying the capillary density and the capillary distribution in microcirculation images can be used as a biological marker to assist critically ill patients. The quantification of these biological markers is labor intensive, time consuming, and subject to interobserver variability. Several computer vision techniques with varying performance can be used to automate the analysis of these microcirculation images in light of the stated challenges. In this paper, we present a survey of over 50 research papers and present the most relevant and promising computer vision algorithms to automate the analysis of microcirculation images. Furthermore, we present a survey of the methods currently used by other researchers to automate the analysis of microcirculation images. This survey is of high clinical relevance because it acts as a guidebook of techniques for other researchers to develop their microcirculation analysis systems and algorithms.
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Roy TK, Secomb TW. Effects of impaired microvascular flow regulation on metabolism-perfusion matching and organ function. Microcirculation 2020; 28:e12673. [PMID: 33236393 DOI: 10.1111/micc.12673] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Accepted: 11/17/2020] [Indexed: 12/14/2022]
Abstract
Impaired tissue oxygen delivery is a major cause of organ damage and failure in critically ill patients, which can occur even when systemic parameters, including cardiac output and arterial hemoglobin saturation, are close to normal. This review addresses oxygen transport mechanisms at the microcirculatory scale, and how hypoxia may occur in spite of adequate convective oxygen supply. The structure of the microcirculation is intrinsically heterogeneous, with wide variations in vessel diameters and flow pathway lengths, and consequently also in blood flow rates and oxygen levels. The dynamic processes of structural adaptation and flow regulation continually adjust microvessel diameters to compensate for heterogeneity, redistributing flow according to metabolic needs to ensure adequate tissue oxygenation. A key role in flow regulation is played by conducted responses, which are generated and propagated by endothelial cells and signal upstream arterioles to dilate in response to local hypoxia. Several pathophysiological conditions can impair local flow regulation, causing hypoxia and tissue damage leading to organ failure. Therapeutic measures targeted to systemic parameters may not address or may even worsen tissue oxygenation at the microvascular level. Restoration of tissue oxygenation in critically ill patients may depend on restoration of endothelial cell function, including conducted responses.
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Affiliation(s)
- Tuhin K Roy
- Department of Anesthesiology & Perioperative Medicine, Mayo Clinic, 200 First Street SW, Rochester, MN, 55905, USA
| | - Timothy W Secomb
- Department of Physiology, University of Arizona, Tucson, AZ, 85724, USA
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Obonyo NG, Fanning JP, Ng ASY, Pimenta LP, Shekar K, Platts DG, Maitland K, Fraser JF. Effects of volume resuscitation on the microcirculation in animal models of lipopolysaccharide sepsis: a systematic review. Intensive Care Med Exp 2016; 4:38. [PMID: 27873263 PMCID: PMC5118377 DOI: 10.1186/s40635-016-0112-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2016] [Accepted: 11/15/2016] [Indexed: 12/29/2022] Open
Abstract
Background Recent research has identified an increased rate of mortality associated with fluid bolus therapy for severe sepsis and septic shock, but the mechanisms are still not well understood. Fluid resuscitation therapy administered for sepsis and septic shock targets restoration of the macro-circulation, but the pathogenesis of sepsis is complex and includes microcirculatory dysfunction. Objective The objective of the study is to systematically review data comparing the effects of different types of fluid resuscitation on the microcirculation in clinically relevant animal models of lipopolysaccharide-induced sepsis. Methods A structured search of PubMed/MEDLINE and EMBASE for relevant publications from 1 January 1990 to 31 December 2015 was performed, in accordance with PRISMA guidelines. Results The number of published papers on sepsis and the microcirculation has increased steadily over the last 25 years. We identified 11 experimental animal studies comparing the effects of different fluid resuscitation regimens on the microcirculation. Heterogeneity precluded any meta-analysis. Conclusions Few animal model studies have been published comparing the microcirculatory effects of different types of fluid resuscitation for sepsis and septic shock. Biologically relevant animal model studies remain necessary to enhance understanding regarding the mechanisms by which fluid resuscitation affects the microcirculation and to facilitate the transfer of basic science discoveries to clinical applications.
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Affiliation(s)
- Nchafatso G Obonyo
- Critical Care Research Group, The Prince Charles Hospital, Brisbane, Queensland, Australia.,Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya.,School of Medicine, University of Queensland, Brisbane, Queensland, Australia
| | - Jonathon P Fanning
- Critical Care Research Group, The Prince Charles Hospital, Brisbane, Queensland, Australia.,School of Medicine, University of Queensland, Brisbane, Queensland, Australia
| | - Angela S Y Ng
- Critical Care Research Group, The Prince Charles Hospital, Brisbane, Queensland, Australia.,School of Medicine, University of Queensland, Brisbane, Queensland, Australia
| | - Leticia P Pimenta
- Critical Care Research Group, The Prince Charles Hospital, Brisbane, Queensland, Australia
| | - Kiran Shekar
- Critical Care Research Group, The Prince Charles Hospital, Brisbane, Queensland, Australia.,School of Medicine, University of Queensland, Brisbane, Queensland, Australia
| | - David G Platts
- Critical Care Research Group, The Prince Charles Hospital, Brisbane, Queensland, Australia.,School of Medicine, University of Queensland, Brisbane, Queensland, Australia
| | - Kathryn Maitland
- Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya.,Department of Paediatrics, Faculty of Medicine, Imperial College London, London, UK
| | - John F Fraser
- Critical Care Research Group, The Prince Charles Hospital, Brisbane, Queensland, Australia. .,School of Medicine, University of Queensland, Brisbane, Queensland, Australia.
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