Optimizing Hemodynamic Support in Severe Sepsis and Septic Shock, An Issue of Critical Care Clinics

Dane Nichols

Description

Guest Editor Dane Nichols, MD, has assembled a panel of experts focusing on Hemodynamic Support in Septic Shock. Topics include: Oxygen Delivery and Consumption: A Macro-Circulatory Perspective; Mean Arterial Pressure: Therapeutic Goals and Pharmacologic Support,Mechanisms; Detection and Potential Management of Microcirculatory Disturbances; Detection of Hypoxia at the Cellular Level; Type A & B Lactic Acidosis: Recognition, Kinetics, and Associated Prognosis; Venous blood gases: What Can They Tell Us About the State of the Circulation; Noninvasive Assessment of Cardiac Preload and Performance through CO2 Rebreathing/ETCO2 Monitoring.

Sujets

• Médecine
• Médecine d'urgence
• Critical Care
• Medical

Informations

• Publié par: Saunders
• Date de parution: 10 mai 2010
• Nombre de lectures: 0
• EAN13: 9781455700219
• Langue: English
• Poids de l'ouvrage: 1 Mo

Extrait

Critical Care Clinics , Vol. 26, No. 2, April 2010
ISSN: 0749-0704
doi: 10.1016/S0749-0704(10)00011-4

Contributors
Critical Care Clinics
Optimizing Hemodynamic Support in Severe Sepsis and Septic Shock
Dane Nichols, MD
Division of Pulmonary-Critical Care Medicine, Oregon Health & Sciences University, Portland, OR, USA
ISSN  0749-0704
Volume 26 • Number 2 • April 2010

Contents
Cover
Contributors
Forthcoming Issues
Preface
Oxygen Delivery and Consumption: A Macrocirculatory Perspective
Lactic Acidosis: Recognition, Kinetics, and Associated Prognosis
Mean Arterial Pressure: Therapeutic Goals and Pharmacologic Support
Static Measures of Preload Assessment
Dynamic Indices of Preload
Optimizing Hemodynamic Support in Septic Shock Using Central and Mixed Venous Oxygen Saturation
The Optimal Hematocrit
Techniques for Determining Cardiac Output in the Intensive Care Unit
The Role of Echocardiography in Hemodynamic Assessment of Septic Shock
Noninvasive Monitoring Cardiac Output Using Partial CO 2 Rebreathing
Mechanisms, Detection, and Potential Management of Microcirculatory Disturbances in Sepsis
Detection of Hypoxia at the Cellular Level
Index
Critical Care Clinics , Vol. 26, No. 2, April 2010
ISSN: 0749-0704
doi: 10.1016/S0749-0704(10)00013-8

Forthcoming Issues
Critical Care Clinics , Vol. 26, No. 2, April 2010
ISSN: 0749-0704
doi: 10.1016/j.ccc.2010.02.001

Preface

Dane Nichols, MD
Division of Pulmonary-Critical Care Medicine, Oregon Health & Sciences University, Portland, OR, USA
E-mail address: [e-mail]


Dane Nichols, MD Guest Editor
From the early recognition of altered hemodynamics in severe sepsis and septic shock, practitioners have sought new and improved ways to optimize convective oxygen transport, to establish important end points for resuscitation, and to assess the effect of various interventions on organ function and survival. In this regard, investigations of animal models of sepsis have provided unequivocal support for the central role of hemodynamics in determining outcome. 1 Unfortunately, the human experience has been checkered with positive and negative trials, providing clinicians with little certainty about how best to proceed when faced with patients suffering from severe sepsis and septic shock. 2 - 5 Notwithstanding The Surviving Sepsis Campaign’s endorsement of early goal-directed therapy, targets such as mean arterial pressure, central venous pressure, hemoglobin levels, and central venous saturation remain controversial goals and await validation in large, multicentered randomized trials. 6
Progress in our understanding of the pathophysiology of sepsis and the introduction of new technologies have added to the clinician’s dilemma. Which of the available and emerging monitoring devices and techniques offers the best assessment of the state of the circulation? What role does microcirculation play in the development of organ dysfunction? Will changes in the macrocirculation influence microcirculatory blood flow? Does this have any effect on tissue use of oxygen?
In this issue of the Clinics , we have attempted to address these and other questions that clinicians routinely face. Articles addressing static and dynamic preload indices, echocardiography, venous blood gas analysis, and the like are meant to provide practitioners with a balanced overview of the topics and seasoned opinions about the current role of these approaches and technologies in the care of patients.
I would like to thank the many contributors for their efforts in reviewing and condensing a large body of work in the area of hemodynamics and oxygen transport. In addition, special consideration goes out to Dr Richard Carlson, who has been a sage voice and source of inspiration to me throughout my career.

References

   1. C. Natason, R.L. Danner, J.M. Reilly, et al. Antibiotics versus cardiovascular support in a canine model of human septic shock. Am J Physiol . 1990;259:H1440-H1447.
   2. D. Bihari, M. Smithies, A. Gimson, et al. The effect of vasodilation with prostacyclin on oxygen delivery and uptake in critically ill patients. N Engl J Med . 1987;317:397-403.
   3. M.A. Hayes, E.H. Yau, A.C. Timmins, et al. Response of critically ill patients to treatment aimed at achieving supranormal oxygen delivery and consumption: Relationship to outcome. Chest . 1993;103(3):886-895.
   4. J.J. Ronco, J.C. Fenwick, M.G. Tweeddale, et al. Identification of the critical oxygen delivery for anaerobic metabolism in critically ill septic and nonseptic humans. JAMA . 1993;270:1724-1730.
   5. E. Rivers, B. Nguyen, S. Haystad, et al. Early goal-directed therapy in the treatment of severe sepsis and septic shock. N Engl J Med . 2001;345(19):1368-1377.
   6. Clinical Trials.Gov. Available at: http://www.clinicaltrial.gov/ct2/results?term=early+goal+directed+therapy Accessed January 11, 2010
Critical Care Clinics , Vol. 26, No. 2, April 2010
ISSN: 0749-0704
doi: 10.1016/j.ccc.2009.12.003

Oxygen Delivery and Consumption: A Macrocirculatory Perspective

Dane Nichols, MD a , * , Nathan D. Nielsen, MD, MSc b
a Division of Pulmonary & Critical Care Medicine, Oregon Health and Sciences University, OHSU-UHN-67, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
b Tulane University, SL-9, 1430 Tulane Avenue, New Orleans, LA 70130, USA
* Corresponding author.
E-mail address: [e-mail]

Abstract
Severe sepsis is a leading cause of death and resource use throughout the world. This article examines the relationship of oxygen delivery to oxygen use under varying conditions. Topics reviewed include the concept of the critical dissolved oxygen, concerns over shared measurement errors in obtaining estimates of oxygen consumption, seminal articles in this area, and the practice of early goal directed therapy.

Keywords
• Oxygen delivery • Oxygen consumption • Early goal-directed therapy
Despite decades of investigation, severe sepsis continues to be a leading cause of death and resource use throughout the world. Deaths attributable to complications of infection now are thought to be on par with those secondary to acute myocardial infarction. In 2001, Angus and colleagues, 1 using data obtained from all nonfederal hospitals in a seven state area as an estimate of national figures, calculated the number of severe sepsis cases in the United States to be somewhere in the neighborhood of 751,000 cases per annum with an associated mortality of 28.6% or 215,000 deaths overall. This figure was roughly twice that estimated by the Centers for Disease Control (CDC) at the beginning of the 1990s. Moreover, they predicted that the incidence of severe sepsis would continue to increase at an annual rate of 1.5%. This trend was borne out in a longitudinal study using information from a national hospital database representing roughly 20% of nonfederal short-term institutions. Over the period from 1993 to 2003, Dombrovskiy and colleagues 2 reported a doubling in hospitalizations for severe sepsis from 64.7 to 134.6 cases per 100,000 population. In addition, the investigators noted an increase in the percentage of patients developing multiple organ dysfunction during their stay. Whereas acuity of illness and crude severe sepsis rate were clearly increasing, the associated case-fatality rate fell approximately 7% during the decade under study. Not surprisingly, the cases were disproportionately concentrated in the elderly, with patients over the age of 65 accounting for roughly three-fifths of hospitalizations. The expense of caring for patients with this syndrome is staggering. During the calendar year 1995, the cost per case of severe sepsis was estimated to be $22,100, which translated into national expenditures approaching $16.7 billion. 1
Over the last 5 decades, remarkable advances in our understanding of the pathophysiology of sepsis have occurred. A crucial aspect of the syndrome involves cardiovascular dysfunction that was first appreciated by Waisbren 3 in the 1950s. Early observations suggested that the lactic acidosis and organ dysfunction seen in septic states were occurring in the setting of normal or high oxygen delivery to tissues and, therefore, represented a unique form of shock. Indeed, experimental models revealed that the critical level of oxygen delivery in sepsis was significantly higher than that seen in anemic, stagnant, and hypoxic hypoxia. 4 Another poorly understood phenomenon also seemed to be occurring in septic animals and patients: normal compensatory increases in O 2 extraction to meet tissue demand appeared to be limited, suggesting that the optimal means to meet increased demand would be through an increase in global oxygen delivery. 4, 5
The problem of meeting cellular oxygen needs and maintaining tissue and organ viability in sepsis has become increasingly complex with the modern demonstration of marked microcirculatory disturbances along with early organelle injury and dysfunction. A variety of studies suggest that augmenting convective transport in the macrocirculation often has little impact on the distribution of microcirculatory blood flow or measured oxygen consumption. 6, 7 Other studies suggest that oxygen tension within a variety of tissues may be more than adequate for normal cellular respiration implying that as shock progresses treatment strategies based on enhanced convective transport are not likely to be successful. 8, 9
Cellular and organelle injury appears to occur very early on in severe septic conditions. Brealey and colleagues, 10 studying mitochondria obtained from septic patients within the first 24 hours of admission to an ICU, frequently found abnormal activity in electron transport complexes I and IV along with marked alterations in the levels of ATP and the ADP-ATP ratio. Even though initially patients were clinically indistinguishable, nonsurvivors had roughly half the amou