Chapter 91 - Sepsis and septic shock Flashcards
Define sepsis
The clinical syndrome characterized by the systemic inflammatory response to a bacterial, viral, protozoal, or fungal origin. (SIRS + infectious cause)
Define severe sepsis
Sepsis complicated by dysfunction of one or more organs
Define septic shock
Acute circulatory failure and persistent arterial hypotension (despite volume resuscitation) associated with sepsis. In people, hypotension is defined by a systolic arterial pressure less than 90mmHg, a mean arterial pressure less than 60, or a reduction in systolic pressure of greater than 40 mmHg from baseline despite adequate volume resuscitation, in the absence of other causes of hypotension.
SIRS criteria in dogs and cats
DOGS
Temperature <99, >102.5 / HR >140 / RR >30 / WBC <6,000 > 19.000
CATS
Temperature <100.4, >104 / HR <140 > 225/ RR >40 / WBC <5,000 > 19.000
Diagnostic criteria for severe sepsis in people (=organ dysfunction variables)
Arterial hypoxemia - PaO2/FiO2 <300
Acute oliguria - Urine output <0.5 ml/kg/hr or 45 mmol/L for at least 2 hours
Creatinine > 2mg/dL
Coagulation abnormalities - INR (international normalized ratio) >15 or aPTT > 60s
Thrombocytopenia - Plt < 100,000/uL
Hyperbilirubinemia - Tbil > 2 mg/dL
List diagnostic criteria for sepsis in people (along with documented or suspected infection)
- General variables: temperature (fever, hyperthermia), heart rate (bradycardia, tachycardia), respiration rate (tachypnea), altered mental status, significant edema or positive fluid balance, hyperglycemia
- Inflammatory variables: leukocytosis, leukopenia, >10% immature forms of WBC, elevated plasma C-reactive (>2 SD above normal value), elevated procalcitonin (>2 SD above normal value)
- Tissue perfusion variables: hyperlactatemia, decreased capillary refill or mottling
- Other variables: ScvO2 >70%, Cardiac index >3.5 L/min
Define MODS
Physiologic drangements of the endothelial, cardiopulmonary, renal, nervous, endocrine, microcirculatory and gastrointestinal systems associated with the progression of uncontrolled systemic inflammation and disseminated intravascular dissemination.
What do the clinical manifestations and course of disease depend on?
- Location of infection
- Virulence of the organism
- Size of inoculums
- Host nutritional status
- Comorbidities
- Age
- Immune response
- Organ function
- Genetic host response
What the acronym PIRO stand for?
Predisposition, Insult or Infection, Response, Organ dysfunction
(conceptual and clinical framework adopted to stage sepsis, incorporating patient factors with the microbial insult)
What are the most common sources for Gram- sepsis?
Gastrointestinal and genitourinary systems
Describe the mechanism leading to the transcription of inflammatory cytokines, in case of a Gram- infection
Gram- bacterial lypopolysaccharide (LPS) -> LPS binding to LPS-binding protein (LBP) -> LPS-LBP complex binding to membrane-bound CD14 on macrophages -> activation of the macrophages, signaling transduction and transcription of inflammatory cytokines (notably TNFalpha, IL1, IL6, IL8, interferon gamma)
What are the most common sources for Gram+ sepsis?
Skin, injured soft tissue, intravenous catheter
Describe the mechanism leading to the transcription of inflammatory cytokines, in case of a Gram+ infection
Activation of T-cells in response to cell wall components, bacterial DNA or soluble bacterial exotoxins
What are the potentially host tissue damaging products released by neutrophils?
reactive oxygen species, proteases, lysozymes, lactoferrin, cathepsins, defensins
Name the derangements of normal homeostatic mechanisms in septic patients
- Loss of vasomotor tone
- Dysregulation of inflammation
- Dysregulation of coagulation
- Increased vascular permeability
- Microcirculatory derangements
Name the most powerful vascular smooth muscle relaxant responsible for the vasodilatory state in dogs and humans patients with septic shock
NO (nitric oxide), synthetized in response to stimulation with endotoxin, TNF-alpha, IL-1, or platelet activating factor
Define crytic shock
Microcirculatory derangements in the face of normal macrohemodynamics
Describe how an increased vascular permeability can lead to hypoxia
Increased vascular permeability -> Efflux of water, proteins and solutes into the interstitial space -> increased distance from the RBC within the capillaries to the target cell mitochondria -> impairement of oxygen transport and delivery to the mitochondria
What is the most common septic focus in cats and dogs?
Peritoneal cavity (dogs 35-36% / cats 47%)
What are the second most common septic foci in cats and dogs?
Dogs: soft tissue and bone (29%, trauma, osteomyelitis, bite wounds) / Cats: pulmonary, parenchymal, pleural sites (24% pyothorax + 14% pneumonia)
Above which lactate concentration fluid resuscitation should be promptly initiated?
Lactate 4 mmol/L
What is the percentage of positive blood culture in critically ill dogs and cats?
49% (human 30%-50%) (43% of dogs with GDV)
What are the factors that should be taken into consideration to select appropriate empirical antimicrobials (before culture results)?
- Location of infection (and ability of the antibiotic to penetrate the site)
- Suspected bacterial flora
- Community VS nosocomial source
- Duration of hospitalization
- Previous exposure to antimicrobials
Name methods to assess the volume status and potential for volume responsiveness in septic patient ()?
- PAOP (pulmonary artery occlusion pressure)
- CVP (central venous pressure) (not predictive of response)
- Echocardiographic evaluation of cardiac function
- Arterial waveform variation in ventilated patients
- Dynamic response to small fluid boluses or passive legs elevation
- Weight monitoring
- IN/OUT monitoring
Which volume of plasma is required to raise the albumin concentration by 0.5 g/dL?
22 mL/kg
What are the risks associated with the use of vasopressors to maintain arterial blood pressure?
Excessive vasoconstriction, especially to the splanchnic and renal circulation, thereby causing GI (promoting loss of gut barrier function and bacterial translocation) and renal ischemia
Name the most common vasopressors used for hypotensive patients in septic shock and peripheral vasodilation?
Norepinephrine, vasopressin, dopamine, phenylephrine
How can we interpret the venous oxygen saturation?
The venous oxygen saturation is reflective of the difference between oxygen delivery and oxygen consumption -> therapeutic target
SvO2 = mixed venous O2 saturation referring to venous blood in the pulmonary artery (pooled blood from the entire body)
ScvO2 = central venous O2 saturation referring to the cranial vena cava (head and upper body)