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Many patients presented to the emergency veterinarian are suffering from global or local tissue hypoperfusion. Global or systemic hypoperfusion can occur secondary to a reduction in the effective circulating intravascular volume (hypovolemic shock) or reduced ability of the heart to pump blood around the body secondary to reduced cardiac function (cardiogenic shock),obstruction to blood flow (obstructive shock), or maldistribution of the circulating intravascular volume (distributive shock). Initial assessment involving physical examination supplemented by measurement of hemodynamic and metabolic parameters allows the clinician to recognize and treat patients with severe global hypoperfusion. Use of techniques like sublingual capnometry and measurement of central venous oxygen saturation may aid recognition and evaluation of early hypoperfusion. Treatment decisions are made based on an assessment of the severity of the hypoperfusion and its probable underlying cause. Early effective treatment of hypoperfusion is likely to lead to a better outcome for the patient.

A five-year-old domestic longhaired cat was evaluated for a seven-day history of worsening respiratory distress. Serum analysis for feline leukaemia virus antigen was positive. Pleural effusion was detected on thoracic radiographs and echocardiography revealed a pericardial effusion and cardiac tamponade. Cytological evaluation of the pleural and pericardial effusions showed lymphoblastic cells indicative of disseminated lymphoma. Following thoracocentesis and pericardiocentesis, the cat was treated for lymphoma using the University of Wisconsin-Madison chemotherapy protocol. The cat was sent home after three days and, at the time of writing (six months after initial presentation), was still symptom free. To the authors' knowledge, this is the first report confirming pericardial effusion and cardiac tamponade in the cat as a direct result of an extranodal lymphoma with cytological evidence of neoplastic cells in the pericardial fluid.

Veterinary species experience similar perturbations of their health to those of human patients. When the long-term prognosis is good and providing suffering can be minimized, animals stand to benefit greatly from recent advances in the field of emergency and critical care. Outcomes in many conditions in small and large animals have improved markedly in the last 15 years, as management has improved, making the financial and emotional investment in critical care worthwhile for many owners.

Objective To review the pathophysiology of fluid and macromolecular movement between the microvascular, interstitial and lymphatic spaces and provide a basis for logical intravenous colloid therapy. Databases used Medline (1966 – present), Commonwealth Agricultural Bureaux abstracts (1973 – present) and Personal files.

Assays for detecting and measuring antinuclear antibodies (ANA) in dogs were compared. They included the indirect immunofluorescence test, using rat liver as substrate, and ELISAs for three nuclear antigens: double-stranded DNA, single-stranded DNA, and histone. There was no correlation between the ANA titre and antibodies to the three nuclear antigens. Analysis of ANA in different arthropathies showed no specific disease association. HEP-2 cells showed no fluorescence reaction with either ANA-positive or ANA-negative dog sera. Western blotting produced too complex a pattern to identify specific antigens. The antigens that reacted with ANA in dogs were not identified; there is either a broad range of reactivities or non-specific binding of immunoglobulins.

Serological surveys of common and grey seals were performed to monitor the spread of the phocid distemper outbreak in 1988 and its effects on the host immune response. The disease affected mainly common seals; grey seals were largely unaffected but did have anti-CDV antibodies which developed during 1988. Canadian seals, both common and grey, showed evidence of a morbillivirus infection but without the apparent mortality observed in British common seals. Common seal circulating immunoglobulin levels were not greatly affected during the outbreak, although there was some reduction in the most severely affected pups. Vaccination of common seals with CDV antigens elicited high titres of antibodies and produced clinical protection. Vertical transmission of host immunity was shown in grey seals although the longevity of protection has not been determined. The large population of common seals which are not immune emphasises that such an epizootic could have serious consequences again in the future.

Immunoglobulin concentrations were measured in the serum and colostrum of adult and pup Grey seals from North Rona in the outer Hebrides and the Isle of May in the Firth of Forth. IgG was shown to be the main immunoglobulin and two subclasses were identified. Serum immunoglobulin content was low in the week-old pups and increased up to 5 weeks, although it remained substantially lower than in the adults. Colostral immunoglobulins were high and cannot explain the low values in the pup serum. It is considered that the increased opportunistic infections seen in Grey seal pups may be related to this low immunoglobulin status.

COLLOID fluid therapy is indicated to treat hypovolaemia and aid the maintenance of plasma volume and intravascular colloid osmotic pressure. The numerous types, preparations and concentrations of colloid solutions available all have varying indications, pharmacokinetics and pharmacodynamics. Selection of a particular product should be based on a sound understanding of these individual characteristics, including their benefits, limitations and side effects. This article describes the properties of commonly used colloid solutions and their indications. Part 1, published in January 2008 (In Practice, volume 30, pp 16-19), discussed patient assessment and the principles of fluid therapy in small animals. Part 2, published in the last issue (In Practice, February 2008, volume 30, pp 85-91), reviewed crystalloid solutions.

Objective: To measure serum parathyroid hormone (PTH) and 25-hydroxyvitamin D3 concentrations in cats with urethral obstruction. Design: Prospective single cohort study. Setting: University affiliated veterinary teaching hospital. Animals: Male cats with urethral obstruction. Interventions: Routine blood samples drawn from male cats with urethral obstruction. Measurements and main results: Measured variables included blood gas parameters, plasma sodium, potassium, chloride, and ionized calcium concentrations, as well as serum blood urea nitrogen, creatinine, phosphorus, PTH, and 25-hydroxyvitamin D3 concentrations. PTH was inversely correlated with ionized calcium and positively correlated with serum phosphorus. No discernable relationship could be found between 25-hydroxyvitamin D3 and any of the measured parameters. Conclusions: Lack of parathyroid response does not appear to be the underlying mechanism for ionized hypocalcemia in cats with urethral obstruction.

THE administration of fluid therapy is commonly used in veterinary medicine to combat dehydration, hypovolaemia and hypoperfusion, to maintain intravascular volume and osmotic pressure, and to correct electrolyte imbalances. An understanding of the physiology of body fluids is important to ensure that the most appropriate fluid is chosen for a given situation. This article, the first in a series of three, describes the principles of fluid therapy and highlights the key aspects of patient assessment. Articles in the February and March issues of In Practice will discuss the individual properties of crystalloid and colloid solutions, respectively.

MANAGEMENT of an animal with an acute abdomen presents one of the greatest challenges in veterinary emergency medicine. This clinical syndrome has a large number of possible causes, many of which require urgent surgery to optimise the chances of a successful outcome. Rapid assessment of the patient9s major body systems (particularly the cardiovascular system) and early institution of supportive medical therapy are a priority while a definitive diagnosis is sought and a suitable treatment plan is formulated. This article describes key aspects of the investigation and initial stabilisation of dogs and cats with an acute abdomen. An article in the next issue of In Practice will discuss the surgical treatment of acute abdominal conditions in small animals.