- Acute renal failure
- Bleeding disorders
- Heart failure
- Metabolic disorders
- Neurological dysfunction
- Post-surgical care
- Respiratory failure
Acute renal failure (ARF)
The kidneys have many functions, but their most important job is to filter the blood and remove metabolic waste products from the body by making urine. Patients can develop kidney failure as a result of many causes including infections such as leptospirosis, toxins such as antifreeze, drug reactions including due to NSAIDs, low blood pressure due to anaesthesia, blood clot formation, blockage of parts of the urinary tract, body-wide disease processes such as sepsis or as a result of old age changes.
When the kidneys fail rapidly, levels of waste products build up in the body causing depression, inappetence, nausea, vomiting and potentially cardiovascular, lung and central nervous system disease. These patients need urgent treatment to deal with the build up of waste products and the complications which result from disturbed body electrolytes.
Treatment of acute renal failure aims to deal with the underlying cause such as removal of the toxin, elimination of the infection or removal of the obstruction to urine flow. In addition patients will need intensive supportive therapy to correct electrolyte imbalances, manage fluid requirements and improve urine output.
In severe cases where patients are making very little urine dialysis may be required to stabilise the patient to provide time for the underlying disease process to be treated. In addition in some cases of intoxications dialysis may also be the primary therapy for the ARF. Dialysis can be achieved by instilling fluid into the abdomen, allowing it to absorb toxins and then removing it. This is called peritoneal dialysis. In some centres, it is possible to perform haemodialysis, where blood is taken out of the body through tubes, passed through a machine which filters it and then returning the cleaned blood back to the patient.
Severe anaemia can occur in animals for multiple reasons but it is generally caused by loss of red blood cells (bleeding), breakdown of red blood cells (haemolysis) or a lack of production of new red blood cells by the bone marrow. Sometimes two or more of these processes can occur in combination. Anaemia is not a disease in its own right, but rather a clinical sign, a symptom of an underlying disease process. Common causes of severe anaemia include haemorrhage due to trauma or a bleeding disorder , haemolysis due to toxins such as zinc or acetaminophen (paracetamol) or due to an immune-mediated condition (IMHA), or bone marrow disorders such as cancer.
Treatment of anaemia involves investigation and therapy of the underlying disease process. Whilst this investigation and treatment is undertaken, patients must be supported with a transfusion of a blood product. These blood products are donated by another animal of the same species. Blood products may be collected just prior to the transfusion or may have been collected previously and carefully stored in anticipation of future need. Blood banking (storage of blood products) is likely to occur only at larger centres. In some countries commercial blood banks are available from which veterinarians may obtain blood products when necessary.
Blood products include fresh whole blood (containing cells and plasma), packed red blood cells or plasma. Plasma products are typically used to treat bleeding disorders . Since the blood products are collected from another animal, even if they are related, patients receiving a blood transfusion must be carefully monitored. Transfusion reactions occur rarely, but can be very serious and so patients will often be hospitalised in Intensive Care Units whilst they receive their blood transfusion.
Coagulopathies or bleeding disorders can be inherited or acquired. Bleeding disorders are due to failure of formation of a platelet plug due to inadequate platelet numbers or platelet dysfunction or due to the failure of the clotting factor protein cascade to form a stable blood clot. Occasionally these disorders may occur in combination. An example of this is disseminated intravascular coagulation (DIC) a very serious condition which occurs secondary to other disorders such as sepsis .
Inherited bleeding disorders are most commonly identified in young animals and include diseases such as haemophilia and von Willebrands disease. These disorders are relatively straightforward to identify but can be challenging to treat. Acquired bleeding disorders are more frequent. Common causes include anticoagulant rodenticides (rat-poison), immune-mediated thrombocytopenia, lungworm infestation (angiostrongylosis) and liver failure.
Treatment of bleeding disorders requires identification of the underlying cause, specific therapy where appropriate and where possible replacement of the required blood component by transfusion of plasma or platelets.
Heart failure is a common cause of hospitalisation in Intensive Care Units. Cardiac disease is common in both dogs and cats. Heart failure occurs when the heart is unable to pump sufficient blood to satisfy the metabolic needs of the body. Heart failure may occur because of leaking heart valves, failure of the heart to pump with sufficient strength or due to a disturbance of the normal electrical rhythm of the heart.
Heart failure is general a term for multiple types of cardiac dysfunction but typically patients will have accumulation of fluid in their chest (pleural effusion) and abdomen (ascites) or in their lungs (pulmonary oedema). In addition many patients will have a high heart rate and weak pulses due to a failing heart pump.
Patients with heart failure require investigation of the underlying cause so that drug therapy can be tailored to them. This investigation will often entail chest x-rays, a cardiac ultrasound examination (echocardiography) and recording of the electrical activity of the heart (ECG). Therapy for heart failure typically involves administration of drugs to encourage removal of excess water (diuretics), drugs to encourage the heart to beat more strongly and more effectively and potentially drugs to control heart rate or heart rhythm.
Patients with severe heart failure are frequently unstable and require intensive supportive treatment including oxygen supplementation, round-the-clock drug therapy and a minimal stress environment. Such patients require close monitoring and are frequently hospitalised in Intensive Care Units.
Due to their inquisitive nature and in some cases lack of dietary discretion (Labrador Retrievers!) animals are prone to intoxications. A huge range of potential toxins exist in our homes and in the environment. Toxins can include household cleaning products, garden chemicals, human or animal medicines, plants and human foodstuffs including grapes, chewing gum and chocolate.
Making a definitive diagnosis of intoxication can be very difficult. Typically, the history of potential exposure is vague, many intoxication syndromes appear similar, few definitive tests for toxins exist and our patients can tell us what they have ingested!
Management of intoxication is also challenging. A few antidotes exist such as N-acetylcysteine for acetaminophen, ethanol or fomepizole for ethylene glycol or dimercaprol for lead. In most cases however therapy for intoxication follows three principles: gastrointestinal or topical decontamination, administration of supportive care and close monitoring for complications. Intoxicated patients are often very sick and in some cases the therapy for intoxication (such as ethanol therapy for ethylene glycol toxicity or anticonvulsant medication for pyrethrin toxicity) makes patients more dependent on veterinary staff to care for them. The sickest intoxicated patients will undoubtedly require Intensive Care.
Severe metabolic disorders can be difficult to manage in animals and often these patients will require some time in the Intensive Care Unit where they can be closely monitored and where their medical care can be fine-tuned. Two of the most common metabolic conditions are diabetic ketoacidosis and hepatic encephalopathy.
Diabetic ketoacidosis (DKA)
Animals with sugar diabetes (diabetes mellitus) have a reduced ability to make and/or respond to insulin. Most can be well controlled with injections of insulin and live a happy, healthy life. In some cases where the insulin therapy has not been optimal, when an animal develops another disease process (such as pancreatitis or an infection) or when diabetes mellitus is identified for the first time animals may be very unwell as a result of DKA.
DKA occurs when the body is unable to use sugar as the source of energy because of inadequate insulin or an inability to respond to insulin (insulin resistance). In these animals fats are used as the principal sources of energy. The increased fat metabolism that occurs in these patients leads to the build up of ketone bodies. This build up of ketone bodies alters the acidity of the blood and leads to detrimental alterations of fluid and electrolyte balance.
Patients with DKA require intensive insulin therapy, close monitoring of their fluid balance, electrolyte concentrations and glucose levels and investigation and treatment of any underlying disease processes. During treatment, these patients can become dangerously anaemic and may require blood transfusions. Management of DKA is often best achieved in an Intensive Care Unit where round-the-clock monitoring and therapy can be provided.
Patients with severe liver disease may develop neurological complications such as behavioural abnormalities, severe mental depression or seizures. The cause of these changes is multifactorial and poorly understood. Treatment is aimed at managing the underlying liver condition to provide time for the liver to regenerate and limiting the development of neurological side effects with drug therapy. These patients require close monitoring for deterioration of their condition and to ensure that seizure activity is identified and treated rapidly.
Animals are commonly hospitalised due to severe neurological dysfunction. This can be due to dysfunction of the brain, spinal cord or peripheral nerves and muscles. Common conditions which cause neurological dysfunction and may require a stay in the Intensive Care Unit include seizures, hepatic encephalopathy , intervertebral disc disease, trauma , intoxications or developmental diseases such as hydrocephalus.
Patients with severe neurological dysfunction may require intensive care because they are unable to protect their airway, require frequent drug administration and close monitoring, are unable to move unaided or have other major body system abnormalities such as respiratory failure .
Some patients are admitted to the ICU following major surgical procedures. These surgical patients may have undergone planned elective surgery and their stay in ICU postoperatively is also planned to ensure a safe and speedy recovery from major surgery such as portosystemic shunt ligation or surgery for congenital cardiac conditions. In other cases emergency surgical patients may require ICU care following surgery, particularly since these animals often have ongoing medical conditions or remain unstable after surgery. Common examples include chest surgery following trauma (thoracotomy) or after bowel resection (enterectomy) associated with septic peritonitis (a bacterial infection of the abdominal cavity).
Post-surgical patients can be extremely sick. These patients need close monitoring and careful attention to their surgical wounds and to provision of pain relief. Surgical patients also have to deal with the physiologic demands of anaesthesia. It is vital that the groups of clinicians the surgeons, anaesthetists and critical care clinicians involved in the care of surgical patients communicate closely with each other to ensure a smooth transition between the operating theatre and the ICU.
The principle functions of the lung are to oxygenate the blood and to remove carbon dioxide from the body. Respiratory failure occurs when the lungs do not work effectively. Respiratory failure can result in inadequate oxygenation of the blood (hypoxaemia), inadequate removal of carbon dioxide (hypoventilation) or both.
Respiratory failure can be caused by a variety of conditions such as heart failure, pneumonia or lungworm. When it is severe it can be called Acute Lung Injury (ALI) or most severe of all Acute Respiratory Distress Syndrome (ARDS).
Treatment of respiratory failure may require oxygen therapy and treatment of the underlying disease e.g. antibiotics for pneumonia. In severe cases when the animal is no longer able to cope without additional support, mechanical ventilation can be used. This involves placing a tube in the animals airway and using a machine to take over the work of breathing for a period of time. This allows the treatment of the underlying disease time to work and the animals lungs time to recover. In most cases the animal will be given drugs to keep them asleep (anaesthesia) to prevent distress.
Infections are a common cause of admission to the Intensive Care Unit. Some patients will develop infections before they arrive at the hospital. For many reasons, other patients may develop an infection whilst in the hospital. Usually the illness that brought the patient to the hospital in the first place has weakened their ability to fight off infections.
Uncontrolled inflammation associated with an infection is called sepsis and is a very serious condition. When the infection is overwhelming such as bacterial peritonitis it can cause dysfunction of other organs such as the kidneys or lungs. If this happens the condition is called severe sepsis and carries a very guarded prognosis.
Patients with sepsis are likely to be in the Intensive Care Unit. They will require intravenous antibiotics and treatment of the underlying cause potentially including surgery. In addition they will require lots of supportive care including fluid therapy, pain relief and drugs to support their blood pressure. In very severe cases their lung function and kidney function may also need support.
Animals are frequently involved in accidents involving falls from height, road traffic collisions or bite injuries caused by other animals. Traumatised patients frequently have injuries to multiple areas of their bodies and often have dysfunction of their major body systems (cardiovascular, respiratory and neurological). Traumatised patients can be very challenging to manage and may require the attention and expertise of multiple personnel emergency and critical care clinicians, neurologists, surgeons and anaesthetists in order to have the best chance of survival and a return to health.
Traumatised patients will often have a long stay in the hospital and frequently will be in the Intensive Care Unit for part of this time. Critical care clinicians sometimes oversee the care of these patients and co-ordinate the multiple procedures and ongoing treatments that these patients require. Traumatised patients frequently require potent analgesics for pain relief, dressing changes for wound management, surgery for fixation of fractures, blood transfusions for treatment of blood loss and close monitoring for complications.