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Basics ⬇

Outline

BASICS

Definition!!navigator!!

  • SIRS—characterized by at least 2 of the 4 following abnormalities: (1) hyperthermia or hypothermia, (2) tachycardia, (3) tachypnea/hypocapnia, and (4) leukopenia, leukocytosis, or left shift
  • Sepsis—SIRS with a source of confirmed or suspected infection
  • Septic shock—sepsis with hypotension refractory to fluid resuscitation
  • Bacteremia—presence of bacteria in the bloodstream
  • Septicemia—bacterial or bacterial toxin invasion into the bloodstream with SIRS

Pathophysiology!!navigator!!

  • In utero infection and postnatal infections within the first week of life are the most common causes of neonatal septicemia. Bacteria can gain entry via placental infection, ingestion of organisms, or through umbilical structures or the respiratory tract
  • Overwhelming bacterial infection or inadequate defense against invading pathogens can lead to sepsis. Gram-negative bacteria are most commonly involved, although the incidence of Gram-positive septicemia is high in some recent reports. Actinobacillus spp., Escherichia coli, Enterobacter spp., Klebsiella spp., Salmonella spp., Streptococcus spp. and Enterococcus spp. are common isolates

Systems Affected!!navigator!!

  • Cardiovascular—may have an early increase in cardiac output that can rapidly progress to decompensated septic shock
  • Endocrine/metabolic—relative adrenal insufficiency may occur with severe sepsis. Energy homeostasis (hypoglycemia), mineral metabolism (hypocalcemia, hypomagnesemia), and pressure regulation (renin–angiotensin aldosterone system) may be affected
  • GI—the intestinal tract is often the primary site of infection (as with colitis and enteritis) or secondary ileus
  • Hemic/lymphatic/immune—neutropenia and immune compromise; less common—thrombocytopenia with disseminated intravascular coagulation and coagulopathies
  • Hepatobiliary—inflammatory cytokines can impair hepatocellular function
  • Musculoskeletal—septic arthritis and septic physitis are common sequelae of septicemia
  • Nervous—infection can localize as meningitis (rare)
  • Ophthalmic—uveitis possible; entropion in severe dehydration; corneal ulcers
  • Renal/urologic—renal insufficiency secondary to hypoperfusion and endotoxemia
  • Respiratory—bacterial pneumonia secondary to sepsis occurs most often via hematogenous spread. May also occur through inhalation or aspiration

Genetics!!navigator!!

There does not appear to be a genetic predisposition to sepsis.

Incidence/Prevalence!!navigator!!

Sepsis is one of the most common reasons for neonatal foals to present to referral centers. It is the main cause of mortality in the first week of life. It is reported to cause approximately 25–30% of neonatal deaths.

Geographic Distribution!!navigator!!

Incidence of septicemia does not appear to have a specific geographic distribution, although bacterial isolates may vary by geographic location.

Signalment!!navigator!!

Mean Age and Range

In utero infection can occur; it is most common within the first week of life.

Predominant Sex

None

Signs!!navigator!!

Historical Findings

  • Illness or stress in mare prior to parturition
  • Placentitis, vulval discharge, milk leakage prior to parturition
  • Premature delivery or prolonged gestation
  • Dystocia
  • Foal has never nursed or was slow to stand and nurse

Physical Examination Findings

  • Lethargy/depression
  • Decreased nursing; loss of suckle reflex
  • Fever or hypothermia
  • Tachycardia and tachypnea, can have bradycardia in late stages
  • Injected mucous membranes; petechiation
  • Late/decompensated sepsis—obtunded, cold extremities, cyanotic, weak pulses, hypothermia
  • Localizing signs—diarrhea, joint effusion, respiratory distress, uveitis, omphalophlebitis

Causes!!navigator!!

  • In utero infection (transplacental)
  • Bacterial inoculation via the GI tract or respiratory tract
  • Entry of bacteria via umbilical structures or wounds

Risk Factors!!navigator!!

  • Maternal—short or prolonged gestation, placental disorders, dystocia, maternal diseases
  • Foal—failure of transfer of passive immunity, prematurity/dysmaturity, NMS, hypoxia, immunosuppression, viral infections, severe combined immunodeficiency syndrome
  • Environment—poor farm management, poor hygiene

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

  • NMS
  • Prematurity/dysmaturity
  • White muscle disease
  • Botulism
  • Congenital neurologic or cardiac abnormalities

CBC/Biochemistry/Urinalysis!!navigator!!

  • Leukopenia (often neutropenia with left shift and toxic changes), although may have normal white blood cell count or leukocytosis
  • Hyperfibrinogenemia or increased serum amyloid A concentration shortly after birth suggestive of in utero infection
  • Hypoglycemia is common
  • Azotemia and elevated liver and muscle enzymes may be present

Other Laboratory Tests!!navigator!!

  • Serum IgG concentrations—failure of transfer of passive immunity is common
  • Blood cultures (aerobic and anaerobic) can confirm sepsis and help direct antimicrobial therapy
  • Blood l-lactate—normal foals <12 h old have l-lactate concentrations up to 4 mmol/L; decreases to <2.5 mmol/L by 24 h of age
  • Blood gas—mixed metabolic and respiratory acidosis is common
  • Arthrocentesis with cytology and culture if septic arthritis suspected
  • Cerebrospinal fluid aspirate with cytology and culture if bacterial meningitis suspected

Imaging!!navigator!!

Radiography

  • Thoracic radiography—pneumonia may be seen
  • Musculoskeletal radiography if septic arthritis/physitis suspected

US

  • Abdominal US—detects signs of ileus and enterocolitis
  • US of umbilical remnants—umbilicus may appear normal externally, but internal structures are commonly affected
  • Thoracic US—detects pleural effusion, consolidation, or pleural roughening

Other Diagnostic Procedures!!navigator!!

Sepsis score—historical data, clinical examination, CBC, and other laboratory data are scored to give a prediction of sepsis. If in doubt, treat the foal for septicemia pending results of blood culture.

Pathologic Findings!!navigator!!

  • Localized infection—pneumonia, septic arthritis, enterocolitis, etc.
  • Generalized petechiation and adrenal hemorrhage are consistent with, but not specific to, neonatal septicemia

Treatment ⬆ ⬇

Outline

TREATMENT

Appropriate Health Care!!navigator!!

Inpatient medical management, and often emergency inpatient intensive care management.

Nursing Care!!navigator!!

  • Fluid therapy—needed to maintain hydration and perfusion
  • Dextrose supplementation for hypoglycemic foals
  • Transfusion with hyperimmune plasma for foals with IgG <800 mg/dL. IgG levels should be rechecked in septic foals as they may consume IgG
  • Oxygen therapy if PaO2 is low
  • Pressors/inotropes if IV fluids do not correct hypotension
  • Prevention of pressure sores—padding and maintain sternal recumbency
  • Eye lubrication

Activity!!navigator!!

Activity is restricted (stall rest) in weak foals and those with musculoskeletal involvement.

Diet!!navigator!!

  • Enteral feeding via nasogastric feeding tube is needed in foals with a weak suckle reflex or inability to stand and nurse
  • Parenteral feeding for foals that are unable to maintain sternal recumbency or do not tolerate enteral feeding (e.g. enterocolitis)

Client Education!!navigator!!

Sepsis with multisystem involvement can be very expensive to treat and has a guarded prognosis. Clients should be aware of the costs and potential complications.

Surgical Considerations!!navigator!!

  • Joint lavage for treatment of septic arthritis
  • Umbilical resection for omphalophlebitis that does not respond to medical therapy

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

Antimicrobials

  • Broad-spectrum antimicrobial combination based on penicillin (e.g. potassium penicillin 22 000 IU/kg IV every 6 h) in combination with an aminoglycoside (e.g. amikacin 20–25 mg/kg IV every 24 h) until results of blood culture are available or there is a lack of response to this combination. A third-generation cephalosporin (e.g. ceftazidime or cefotaxime 40–50 mg/kg IV every 6–8 h) may be indicated
  • Metronidazole (for foals <10 days of age, 10 mg/kg q12 h; for foals >10 days of age, 15 mg/kg q12 h IV or PO) if there is suspicion of anaerobic sepsis. Chloramphenicol (40–50 mg/kg PO every 6–8 h) can be considered in foals that remain febrile or have umbilical abscess

Anti-inflammatories

  • Flunixin meglumine (0.5–1.1 mg/kg IV every 12 h)
  • Ketoprofen (1.1–2.2 mg/kg IV every 12 h)
  • Corticosteroids—low-dose hydrocortisone may be used to treat relative adrenal insufficiency or refractory septic shock, but there is no clear evidence for its use in foals
  • Carprofen
  • Meloxicam (0.6 mg/kg PO every 12 h)

Antiendotoxin Therapy

Polymyxin B (3000–5000 IU/kg IV every 8–12 h).

Vasopressors/Inotropes

Gastroprotectants

Routine use of acid suppressors (e.g. omeprazole, ranitidine) to raise the gastric pH is discouraged in septic foals, as these foals tend to have an alkaline gastric pH, and further alkalinization may encourage bacterial overgrowth and translocation.

Precautions!!navigator!!

  • Aminoglycosides, NSAIDs, and polymyxin B should be used with caution in hypotensive and hypovolemic foals owing to the risk of renal damage
  • NSAIDs may contribute to development of renal damage and gastric ulcers

Alternative Drugs!!navigator!!

Dopamine and vasopressin (argipressin) may also be used for treatment of septic shock.

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Patient Monitoring!!navigator!!

  • Intensive monitoring with frequent checks of vital parameters (every 1–4 h). Advanced monitoring includes blood pressure, urine output, and cardiac output measurements
  • l-Lactate, blood glucose, renal parameters, electrolytes, and CBC should be monitored to assess response to therapy. Localized infections (septic arthritis, pneumonia, etc.) may develop during hospitalization

Prevention/Avoidance!!navigator!!

  • Clean foaling environment; reduce contamination of mare's udder and limbs
  • Ensure adequate colostrum intake; administer IV plasma if IgG is not adequate
  • Dip umbilicus with dilute chlorhexidine or povidone–iodine

Possible Complications!!navigator!!

  • Organ failure (renal, respiratory)
  • Decreased athletic performance after septic arthritis

Expected Course and Prognosis!!navigator!!

Short-term survival is approximately 50%, with reported ranges from 30% to 70%. Gram-negative septicemia, multisystem disease, and high sepsis score have been correlated with higher mortality. The ability of the foal to stand and normal l-lactate concentration on admission are positively correlated with survival.

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Associated Conditions!!navigator!!

  • Septic arthritis
  • Omphalophlebitis
  • Diarrhea

Age-Related Factors!!navigator!!

Foals are most commonly affected in the first week of life.

Synonyms!!navigator!!

Bacteremia

Abbreviations!!navigator!!

  • CRI = constant rate infusion
  • GI = gastrointestinal
  • IgG = immunoglobulin G
  • NMS = neonatal maladjustment syndrome
  • NSAID = nonsteroidal anti-inflammatory drug
  • PaO2 = partial pressure of oxygen in arterial blood
  • SIRS = systemic inflammatory response syndrome
  • US = ultrasonography, ultrasound

Suggested Reading ⬆ ⬇

Corley KT, Donaldson LL, Furr MO. Arterial lactate concentration, hospital survival, sepsis, and SIRS in critically ill neonatal foals. Equine Vet J 2005;37:53–59.

Sanchez LC. Equine neonatal sepsis. Vet Clin North Am Equine Pract 2005;21:273–293.

Wong DM, Wilkins PA. Defining the systemic inflammatory response syndrome in equine neonates. Vet Clin North Am Equine Pract 2015;31:463–481.

Author(s) ⬆

Author: Ramiro Toribio

Consulting Editor: Margaret C. Mudge

Acknowledgment: The author acknowledges the prior contribution of Margaret C. Mudge.