Sepsis continues to be one of the leading causes of mortality in both veterinary and human medicine. In people, severe sepsis is the third leading cause of death, with a mortality rate of 28-50% or higher. If sepsis can be recognised in its early stages then there is a higher probability of being able to save that patient. However, once sepsis leads to septic shock and multiple organ failure, the mortality rate skyrockets.

Definitions

The terminology used to discuss sepsis and inflammation is often confusing but the following definitions have been agreed by the American College of Chest Physicians/Society of Critical Care Medicine and have been adapted for use by veterinarians.

 Systemic Inflammatory Response Syndrome (SIRS): overwhelming systemic response to inflammation, which may occur with or without infection. The clinical criteria for SIRS are manifested by two or more of the following conditions:

 Heart rate >140 bpm (dog), or <140 or >225 bpm (cat)

 Respiratory rate >28 breaths per minute or PaCO₂ <32 mmHg

 Temperature >39.7°C (103.5°F) or <37.8°C (100°F)

 White blood cell count >12 x 10⁹/l or <4 x 10⁹/l or >10% bands

 Sepsis: the systemic inflammatory response syndrome resulting from a documented infection

 Severe sepsis: sepsis associated with organ dysfunction, hypoperfusion or hypotension. Hypoperfusion and perfusion abnormalities may include, but are not limited to, lactic acidosis, oliguria, or an acute alteration in mental status

 Septic shock: severe sepsis with hypotension despite adequate fluid resuscitation, together with the presence of perfusion abnormalities or organ dysfunction

 Multiple organ dysfunction syndrome (MODS): presence of altered organ function in an acutely ill patient such that homeostasis cannot be maintained without intervention

Early recognition of sepsis or SIRS is essential, but the best treatment is prevention. Once an animal develops sepsis or SIRS, treatment is primarily supportive; however, any source of infection or inflammation must be effectively treated or removed. All patients with sepsis are at risk for developing MODS and death, therefore it is imperative to initiate aggressive preventative treatment and monitoring. Patients considered to be at risk for sepsis include those with an identified source of inflammation/infection such as severe wounds, extensive tissue trauma or burns, severe inflammatory diseases such as pancreatitis, history of prolonged hypotension, extensive surgery or trauma, immunosuppression and metastatic neoplasia.

Clinical Presentation

The clinical presentation of sepsis will vary depending on the severity and stage of the disease process. Sepsis can be described as early or late. In early sepsis the body is in a compensatory state in order to maintain adequate perfusion to the heart and brain. This state is often referred to as 'hyperdynamic' sepsis. Physical parameters in early sepsis will reveal the following: fever; tachycardia; tachypnoea; brick-red or muddy mucous membranes; rapid capillary refill time (<1 second); bounding pulses; and mental depression.

As the sepsis progressively worsens, cardiac output is decreased. Vascular leakage and vasodilation will result in decreased venous return and decreased cardiac output leading to decompensated sepsis or 'hypodynamic' septic shock. Physical parameters in late sepsis will reveal the following: pale mucous membranes; prolonged capillary refill time (>2 seconds); weak or thready femoral pulses; tachypnoea; hypothermia; tachycardia (bradycardia in the cat); severe hypotension; stuporous mental state; and evidence of organ failure (oliguria, hypoxaemia, oedema, bloody diarrhoea, icterus and disseminated intravascular coagulation (DIC)).

Laboratory Changes with Sepsis

Systemic inflammation results in both haematological and biochemical changes. The source of inflammation or infection and the severity of illness will influence these changes. Common findings include: hyperglycaemia (early) or hypoglycaemia; azotaemia; leucocytosis or leucopenia; mild to moderate thrombocytopenia; hypoalbuminaemia; prolonged clotting times; increased serum lactate; and hyperbilirubinaemia.

Management

The keys to the successful management of sepsis are restoration of cardiac output, support of secondary organs affected and control of the source of infection. The most critical goal is preventing disease progression. The source of inflammation or infection should be identified as quickly as possible, and attempts made either to initiate appropriate aggressive medical therapy or to remove the focus, or both. In addition, the septic patient has systemic abnormalities that need supportive care.

Fluid Therapy

Animals with sepsis will have massive losses of fluids from the intravascular compartment into third body spaces. Volume replacement is an important element in restoring blood pressure and cardiac output. Combinations of crystalloid, colloid, blood component and other volume expander therapies are used as needed during and after initial volume resuscitation. The concurrent use of colloids during resuscitation will rapidly restore intravascular volume and reduce the amount of crystalloid required. In addition it will help to decrease the development of peripheral oedema from the increased vascular permeability. Patients that do not respond to adequate volume resuscitation may require pharmacological support with vasoactive drugs to improve haemodynamic function. Placement of a central venous line, which allows central venous pressure monitoring and serial blood sampling, is useful. Although a central line provides some guidance for fluid resuscitation, the length of the catheter does not allow for the rapid administration of intravenous fluids, so it must be placed in addition to short, widebore peripheral catheters.

Oxygen Therapy

Oxygen supplementation should be administered to septic patients to maximise oxygen delivery to the tissues. Hypoxaemia is common, due to ventilation-perfusion mismatch from decreased perfusion and interstitial oedema. Attempts should be made to maintain the patient's PaO₂ above 80 mmHg. Anaemic patients may require a blood transfusion to maximise oxygen delivery to the tissues and maintain the haematocrit above 25%.

Nutritional Therapy

Sepsis produces a hypermetabolic state that requires support with adequate nutrition. The gut has been identified as a key organ in sepsis, and gastrointestinal dysfunction is common. Early nutritional support is primarily used to maintain the integrity of the intestinal mucosal barrier and decrease chances of bacterial translocation. Enteral nutrition is the preferred method of nutritional support. If abdominal surgery is required for the underlying problem, then consideration should be given to placement of a gastrostomy or jejunostomy tube. If enteral feeding is not tolerated, partial parenteral nutrition can provide nutritional support for a few days until enteral nutritional support is reinstituted. Gastric protectants may be required to prevent ulceration and treat gastrointestinal bleeding.

Miscellaneous Therapies

Coagulopathies are a potential risk due to the large inflammatory response occurring, and DIC can be expected in septic patients. The use of anticoagulants and fresh frozen plasma may be required to replace clotting factors and prevent thrombosis. In the event that the patient has a coagulopathy, avoid excessive venipuncture especially use of the jugular vein.

Pain management in the postoperative septic patient is very important and the analgesic selected must cause minimal cardiovascular depression, and must be reversible in case of an adverse event. Drugs that have minimal cardiovascular depressant effects such as pure opioids are often chosen.

Monitoring

Due to the haemodynamic and cardiovascular instability associated with sepsis, aggressive monitoring is necessary. It is important to recognise that the septic patient can rapidly decompensate. Vital signs including heart rate and rhythm, respiratory rate, body temperature, mucous membrane colour, capillary refill time and pulse quality should be checked regularly and will provide information on cardiovascular status.

Blood pressure should be monitored, as the risks of hypotension resulting from hypovolaemia are significant. Systolic pressure must remain above 90 mmHg and the mean arterial pressure must remain above 60 mmHg to maintain renal perfusion. Urine output should be assessed on an ongoing basis as a reflection of renal function and fluid balance. An indwelling urinary catheter should be connected to a closed system to record urine output accurately.

Constant electrocardiograph (ECG) monitoring is important as cardiac arrhythmias can decrease cardiac output in a patient who is likely to be already compromised.

Laboratory parameters, including packed cell volume, total solids, albumin, blood glucose, coagulation times, electrolytes and acid-base balance, should be evaluated frequently. Appropriate interventions should be taken to correct any deficits or abnormalities. Potassium levels may drop as a result of fluid diuresis and may require supplementation.

Having a multilumen catheter in place from which blood can easily be drawn will minimise the need for repeated venipuncture.

Nursing Care

Monitoring and treatment is intense in these patients and experienced nursing care is a must. Many of these animals are nonambulatory, so bladder/urinary care, colon care, passive range of motion, oral care and prevention of pressure sores are absolutely necessary. Nursing management should include strict adherence to standards of practice to prevent infection. Close monitoring and regular cleaning of catheter or tube insertion sites are important, and all fluid lines or drainage systems should be changed at least every 48 hours. It is recommended that all persons working with critically ill or immunocompromised animals wear personal protective equipment and follow appropriate hand cleansing procedures.

Conclusion

SIRS, sepsis and MODS are all very serious syndromes and can quickly lead to patient death if clinical signs go unrecognised. Since the physiological status in these patients is so dynamic, experienced personnel are needed in order to recognise sudden, frequent changes in an animal's status. Although early recognition and goal-directed therapy may lead to more positive outcomes, the prognosis for septic patients remains guarded to poor.