Chapter 91 - Sepsis and septic shock

Question 1

Define sepsis

Answer 1

The clinical syndrome characterized by the systemic inflammatory response to a bacterial, viral, protozoal, or fungal origin. (SIRS + infectious cause)

Question 2

Define severe sepsis

Answer 2

Sepsis complicated by dysfunction of one or more organs

Question 3

Define septic shock

Answer 3

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.

Question 4

SIRS criteria in dogs and cats

Answer 4

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

Question 5

Diagnostic criteria for severe sepsis in people (=organ dysfunction variables)

Answer 5

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

Question 6

List diagnostic criteria for sepsis in people (along with documented or suspected infection)

Answer 6

• 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

Question 7

Define MODS

Answer 7

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.

Question 8

What do the clinical manifestations and course of disease depend on?

Answer 8

• Location of infection
• Virulence of the organism
• Size of inoculums
• Host nutritional status
• Comorbidities
• Age
• Immune response
• Organ function
• Genetic host response

Question 9

What the acronym PIRO stand for?

Answer 9

Predisposition, Insult or Infection, Response, Organ dysfunction
(conceptual and clinical framework adopted to stage sepsis, incorporating patient factors with the microbial insult)

Question 10

What are the most common sources for Gram- sepsis?

Answer 10

Gastrointestinal and genitourinary systems

Question 11

Describe the mechanism leading to the transcription of inflammatory cytokines, in case of a Gram- infection

Answer 11

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)

Question 12

What are the most common sources for Gram+ sepsis?

Answer 12

Skin, injured soft tissue, intravenous catheter

Question 13

Describe the mechanism leading to the transcription of inflammatory cytokines, in case of a Gram+ infection

Answer 13

Activation of T-cells in response to cell wall components, bacterial DNA or soluble bacterial exotoxins

Question 14

What are the potentially host tissue damaging products released by neutrophils?

Answer 14

reactive oxygen species, proteases, lysozymes, lactoferrin, cathepsins, defensins

Question 15

Name the derangements of normal homeostatic mechanisms in septic patients

Answer 15

• Loss of vasomotor tone
• Dysregulation of inflammation
• Dysregulation of coagulation
• Increased vascular permeability
• Microcirculatory derangements

Question 16

Name the most powerful vascular smooth muscle relaxant responsible for the vasodilatory state in dogs and humans patients with septic shock

Answer 16

NO (nitric oxide), synthetized in response to stimulation with endotoxin, TNF-alpha, IL-1, or platelet activating factor

Question 17

Define crytic shock

Answer 17

Microcirculatory derangements in the face of normal macrohemodynamics

Question 18

Describe how an increased vascular permeability can lead to hypoxia

Answer 18

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

Question 19

What is the most common septic focus in cats and dogs?

Answer 19

Peritoneal cavity (dogs 35-36% / cats 47%)

Question 20

What are the second most common septic foci in cats and dogs?

Answer 20

Dogs: soft tissue and bone (29%, trauma, osteomyelitis, bite wounds) / Cats: pulmonary, parenchymal, pleural sites (24% pyothorax + 14% pneumonia)

Question 21

Above which lactate concentration fluid resuscitation should be promptly initiated?

Answer 21

Lactate 4 mmol/L

Question 22

What is the percentage of positive blood culture in critically ill dogs and cats?

Answer 22

49% (human 30%-50%) (43% of dogs with GDV)

Question 23

What are the factors that should be taken into consideration to select appropriate empirical antimicrobials (before culture results)?

Answer 23

• 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

Question 24

Name methods to assess the volume status and potential for volume responsiveness in septic patient ()?

Answer 24

• 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

Question 25

Which volume of plasma is required to raise the albumin concentration by 0.5 g/dL?

Answer 25

22 mL/kg

Question 26

What are the risks associated with the use of vasopressors to maintain arterial blood pressure?

Answer 26

Excessive vasoconstriction, especially to the splanchnic and renal circulation, thereby causing GI (promoting loss of gut barrier function and bacterial translocation) and renal ischemia

Question 27

Name the most common vasopressors used for hypotensive patients in septic shock and peripheral vasodilation?

Answer 27

Norepinephrine, vasopressin, dopamine, phenylephrine

Question 28

How can we interpret the venous oxygen saturation?

Answer 28

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)