Infectious Diseases and Antimicrobial Stewardship in Critical Care Medicine

Cheston B. Cunha, Burke A. Cunha, Cheston B. Cunha, Burke A. Cunha

• Publisher: CRC Press
• Year: 2020
• ISBN:
  9781351583381
• Edition: 4
• Topic: Médecine
• Subtopic: Théorie, pratique et référence de la médecine

Infectious Diseases and Antimicrobial Stewardship in Critical Care Medicine 4E has been fully updated and revised. The clinical diagnostic approach to common infectious disease problems in the CCU is the underlying theme in the book. Emphasized throughout is the importance of formulating an accurate early presumptive clinical syndromic diagnosis which is the basis for selecting optimal initial antimicrobial therapy in the CCU. Without an accurate presumptive clinical diagnosis, effective therapy is unlikely at best. Based on the most probable clinical diagnosis, optimal antibiotic empiric therapy, based on antimicrobial stewardship principles, minimizes resistance and antibiotic complications in the CCU.

This new edition features chapters that explain the tenets of differential diagnostic reasoning, differential diagnostic characteristics of fever patterns in the CCU. The proper interpretation of rapid diagnostic tests, in the appropriate clinical context, is included. The diagnostic importance of cardinal clinical findings, particularly when combined, in the appropriate clinical context is emphasized and remains the basis for clinical problem solving in the CCU. Uniquely, critical diagnostic physical findings in the CCU, including color atlas of diagnostic eye findings, are included as important diagnostic determinants in the CCU.

Written by infectious disease clinicians for CCU consultants, Infectious Diseases and Antimicrobial Stewardship in Critical Care Medicine 4E remains a useful evidence based and experience tempered key clinical resource for infectious disease problems in the CCU.

Key Features

• Essentials of the tenets of clinical diagnostic reasoning is explained as it relates to formulating a rapid and accurate clinical syndromic diagnosis in the CCU
• The diagnostic significance of fever patterns and their relationship to the pulse rate in the proper clinical context is explained in depth as related to the CCU setting
• Formulating an accurate early clinical syndromic diagnosis is presented as essential since it is the basis of effective empiric antibiotic therapy in the CCU
• How to combine key non-specific laboratory and imaging findings to increase diagnostic specificity and diagnostic probability in the CCU is presented
• Clinical perspective on the proper interpretation of the clinical significance of rapid diagnostic test results in the CCU is included
• A clinical approach to apparent "antibiotic failure" in the CCU is presented either due to actual antibiotic failure or seeming but unrelated non-antibiotic failure
• Section focuses on the practical aspects of antimicrobial stewardship particularly as related to optimizing dosing effectiveness while minimizing resistance and adverse effects in the CCU

Section II

Clinical Syndromic Approach in the Critical Care Unit

10	The Clinical Approach to Sepsis and Its Mimics in the Critical Care Unit Abdullah Chahin and Steven M. Opal

CONTENTS

Clinical Perspective

The New Sepsis Definitions

Epidemiology of Sepsis

Sepsis Workup: Approach Considerations

Mimics of Sepsis

Cardiogenic vs. Septic Shock

Summary

References

CLINICAL PERSPECTIVE

Sepsis is a life-threatening organ dysfunction due to dysregulated host response to an infective process. In sepsis, the infection triggers a complex network of interactions between the host response and microbial invasion and replication. The infected host’s innate and adaptive immune response features an array of pro- and anti-inflammatory cytokines and chemokines, along with complement-mediated defenses and pro- and anti-coagulation mediators [1]. If the infection is not controlled locally, sepsis continues to propagate, leading to dysfunction in multiple organ systems.

The initial immune host response manifests as systemic inflammatory response syndrome (SIRS), a term first coined by Roger Bone and associates in 1992. It consists of four readily available clinical and laboratory parameters (elevated body temperature, pulse rate, respiratory rate, and white blood cell count), thought to embody the signs and symptoms seen with the body’s innate immune reaction to the inflammatory process. The SIRS criteria were intended to be used to standardize the terminology and the reproducibility of patient populations enrolled in new therapeutic trials in sepsis. However, their ease of use and face validity were rapidly adopted by clinicians as a diagnostic tool for the early recognition of sepsis in the emergency room, medical floors, and the critical care unit.

Despite the fact that the cutoff values for the SIRS criteria were set by expert opinion, they seemed reasonable and quickly became established as the criteria to diagnose sepsis expeditiously and to begin management as soon as possible [2]. Clinical experience soon began to appreciate that the SIRS plus infection definition of sepsis had some major practical limitations. A large study found that infection accounted for only 26% of SIRS patients in the emergency room setting in the United States [3]. Another recent study in the critical care unit (CCU) found a sensitivity of 88% for SIRS in patients with confirmed sepsis [4]. The SIRS criteria are therefore a reasonably sensitive but highly non-specific measure, as it can be caused by ischemia-reperfusion injury, sterile inflammation, tissue trauma, burns, necrosis, or several insults combined. In Table 10.1, the initial category of illness causing SIRS in adults, when presenting to emergency departments in the United States (2007–2010) [3]. Mimics of sepsis are a common cause of misdiagnosis in acute settings, as all of these clinical conditions present with symptoms and signs that meet the definition of SIRS. It is of critical importance to differentiate between infection-mediated sepsis and its common clinical mimics in the intensive care settings. The failure to recognize these mimics as separate entities from sepsis carries the potential for increased mortality and morbidity.

THE NEW SEPSIS DEFINITIONS

In response to the increasingly recognized, clinically evident shortcomings of the SIRS-sepsis-severe sepsis-septic shock definitions, as purposed by the Bone criteria in 1992, an international sepsis definition consensus conference was organized in 2001 [2]. At this meeting, the investigators widely agreed that the lack of precision in the current diagnostic criteria was problematic for both clinicians and clinical investigators alike. The participants acknowledged that the lack of clear diagnostic criteria for sepsis terminology was a hindrance to progress, but no concrete proposals were agreed upon to move the field ahead. The conference participants added a number of organ dysfunctions and biomarkers that were highly associated with sepsis. They also proposed the idea of categorizing patients by using the PIRO method. PIRO stands for Predisposing factors; Infection; host Response, and Organ dysfunction. The logic was to categorize septic patients into a system akin to the TNM (T-tumor size, N-nodal involvement, M-metastasis) classification used so effectively in clinical oncology as a guide to staging, optimal treatment, and prognostication. This concept is still an intriguing framework to approach sepsis from a logical, graded format but has not been extensively developed to analyze its clinical relevance in sepsis research [2].

TABLE 10.1
Distinguishing Features Between the 1991/2001 and the 2106 Version 3 Sepsis Definitions

Definition Terms	1991/2001 Versions 1/2	2016 (Version 3)
Colonization	Not stated	Contact with a potential pathogen but no host response
Infection	Contact with a pathogen inducing a local host immune response	Contact with a pathogen inducing a local host immune response
Severe infection	Not stated	Contact with a pathogen inducing systemic host inflammatory response
Sepsis	Infection accompanied by SIRS	Severe infection accompanied by one or more damaging host-induced organ dysfunction(s)
Severe sepsis	Contact with a pathogen inducing SIRS and one or more damaging host-induced organ dysfunction(s)	Term no longer used, as all sepsis is considered severe and life-threatening
Septic shock	Subset of severe sepsis with fluid-non-responsive hypotension necessitating vasopressors	Subset of sepsis with fluid-non-responsive hypotension necessitating vasopressors to maintain MAP >65 mmHg and blood lactate >2 mmol/L

TABLE 10.2
Sepsis Mimics

Condition	Features Mimicking Sepsis	Distinctive Features
Macrophage activation syndrome	High fever, lymphadenopathy, altered mental status, cytokine elevation, pancytopenia, multi-organ failure	Pancytopenia on presentation, mucocutaneous findings (purpura, easy bruising, mucosal bleeding), hepatosplenomegaly, elevated ferritin
Pancreatitis	Low grade fever, leukocytosis, tachycardia, lung infiltrates	Severe, epigastric pain, elevated amylase and lipase, abdominal computerized tomography findings consistent with pancreatitis
Aspiration pneumonitis	Dyspnea, tachypnea, fever, lobar infiltrate on chest X-ray	Witnessed aspiration of gastric contents, pneumonitis comes on suddenly while pneumonia builds up gradual symptoms Infiltrates in dependent areas of lung
Adrenal insufficiency	Fatigue, hypotension, hyperdynamic state with low SVR	Positive response to hydrocortisone stress dose
Hypovolemia	Tachypnea, tachycardia, hypotension, low-grade fever	Clinical signs of dehydration External signs of volume loss (hemorrhage, trauma, vomiting, diarrhea)
Pulmonary embolism	Fever, tachycardia, leukocytosis	Hypoxemia with respiratory alkalosis, unilateral leg swe...