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The goal of resuscitative fluid therapy is to rapidly expand circulating blood volume in order to restore tissue perfusion. Although this therapy often serves to improve macrohemodynamic parameters, it can be associated with adverse effects on the microcirculation and endothelium. The endothelial surface layer (ESL) provides a protective barrier over the endothelium and is important for regulating transvascular fluid movement, vasomotor tone, coagulation, and inflammation. Shedding or thinning of the ESL can promote interstitial edema and inflammation and may cause microcirculatory dysfunction. The pathophysiologic perturbations of critical illness and rapid, large-volume fluid therapy both cause shedding or thinning of the ESL. Research suggests that restricting the volume of crystalloid, or “clear” fluid, may preserve some ESL integrity and improve outcome based on animal experimental models and preliminary clinical trials in people. This narrative review critically evaluates the evidence for the detrimental effects of resuscitative fluid therapy on the ESL and provides suggestions for future research directions in this field.

Background Venom-induced consumption coagulopathy (VICC) from tiger snake (Notechis scutatus) envenomation results in a dose-dependent coagulopathy that is detectable on coagulometry. However, individual coagulation factor activities in dogs with tiger snake envenomation have not been determined. This study aimed to characterise VICC and the time course of recovery in tiger snake envenomed dogs and to investigate an association between tiger snake venom (TSV) concentrations and factor activity. Methods This was a prospective, observational, cohort study. The study cohort was 11 dogs of any age, breed, sex, body weight >10 kg, confirmed serum TSV on ELISA and treated with antivenom. Blood was collected at enrolment before antivenom administration, then at 3, 12 and 24 h after antivenom administration. Tiger snake venom concentrations were detected with a sandwich ELISA. Fibrinogen was measured using a modified Clauss method, and coagulation factors (F) II, V, VII, VIII and X were measured with factor-deficient human plasma using a modified prothrombin (PT) and activated partial thromboplastin (aPTT) method. Linear mixed models, with multiple imputations of censored observations, were used to determine the effect of time and TSV concentration on the coagulation times and factor activity. This cohort was compared to 20 healthy controls. Results At enrolment, there were severe deficiencies in fibrinogen, FV and FVIII, with predicted recovery by 10.86, 11.75 and 13.14 h after antivenom, respectively. There were modest deficiencies in FX and FII, with predicted recovery by 20.57 and 32.49 h after antivenom, respectively. No changes were detected in FVII. Prothrombin time and aPTT were markedly prolonged with predicted recovery of aPTT by 12.58 h. Higher serum TSV concentrations were associated with greater deficiencies in FII, FV and FVIII, and greater prolongations in coagulation times. The median (range) serum TSV concentration was 57 (6–2295) ng/mL. Conclusions In tiger snake envenomed dogs, we detected a profound, TSV-concentration-related consumption of select coagulation factors, that rapidly recovered toward normal. These findings allowed further insight into tiger snake VICC in dogs.

Objective To review the current literature with respect to the physiology, pathophysiology, and measurement of lactate. Data sources Data were sourced from veterinary and human clinical trials, retrospective studies, experimental studies, and review articles. Articles were retrieved without date restrictions and were sourced primarily via PubMed, Scopus, and CAB Abstracts as well as by manual selection. Human and veterinary data synthesis Lactate is an important energy storage molecule, the production of which preserves cellular energy production and mitigates the acidosis from ATP hydrolysis. Although the most common cause of hyperlactatemia is inadequate tissue oxygen delivery, hyperlactatemia can, and does occur in the face of apparently adequate oxygen supply. At a cellular level, the pathogenesis of hyperlactatemia varies widely depending on the underlying cause. Microcirculatory dysfunction, mitochondrial dysfunction, and epinephrine-mediated stimulation of Na+ -K+ -ATPase pumps are likely important contributors to hyperlactatemia in critically ill patients. Ultimately, hyperlactatemia is a marker of altered cellular bioenergetics. Conclusion The etiology of hyperlactatemia is complex and multifactorial. Understanding the relevant pathophysiology is helpful when characterizing hyperlactatemia in clinical patients.

OBJECTIVE: To review the current literature pertaining to the use of lactate as a prognostic indicator and therapeutic guide, the utility of measuring lactate concentrations in body fluids other than blood or plasma, and the clinical management of hyperlactatemia in dogs, cats, and horses. DATA SOURCES: Articles were retrieved without date restrictions primarily via PubMed, Scopus, and CAB Abstracts as well as by manual selection. HUMAN AND VETERINARY DATA SYNTHESIS: Increased plasma lactate concentrations are associated with increased morbidity and mortality. In populations with high mortality, hyperlactatemia is moderately predictive in identifying nonsurvivors. Importantly, eulactatemia predicts survival better than hyperlactatemia predicts death. Consecutive lactate measurements and calculated relative measures appear to outperform single measurements. The use of lactate as a therapeutic guide has shown promising results in people but is relatively uninvestigated in veterinary species. Increased lactate concentrations in body fluids other than blood should raise the index of suspicion for septic or malignant processes. Management of hyperlactatemia should target the underlying cause. CONCLUSION: Lactate is a valuable triage and risk stratification tool that can be used to separate patients into higher and lower risk categories. The utility of lactate concentration as a therapeutic target and the measurement of lactate in body fluids shows promise but requires further research.

Objective To retrospectively determine the population and outcome characteristics of a cohort of Australian elapid snake envenomed cats requiring mechanical ventilation (MV). Design Retrospective observational study (2005–2014). Setting Academic veterinary emergency and critical care service. Animals Twelve cats undergoing MV for elapid snake envenomation. Interventions None. Measurements and Main Results The medical records were searched to identify cats requiring MV as part of treatment for elapid snake envenomation. Signalment, the indication for, duration of and complications associated with MV, duration of hospitalization, and survival to hospital discharge were recorded for each of the enrolled cases. Seven cats (58.3%) underwent MV because of presumed unsustainable respiratory effort and 5 cats (41.7%) for respiratory arrest. Eleven cats (91.7%) were successfully weaned from MV and survived to hospital discharge. No cats developed ventilator associated pneumonia or pneumothorax. The median duration of MV was 19.5 hours for the survivors (range 7.0–37.0 hours) and median duration of hospitalization was 3.5 days (range 2.4–14.9 days). Conclusions Cats requiring MV for elapid snake envenomation have a favorable outcome and require a relatively short period of MV. Complications encountered are unlikely to influence outcome.

Lactate is an essential, versatile metabolic fuel in cellular bioenergetics. In human emergency and critical care, lactate is used as a biomarker and therapeutic endpoint and evidence is growing in veterinary medicine supporting its clinical utility. Lactate production is a protective response providing ongoing cellular energy during tissue hypoperfusion or hypoxia and mitigating acidosis. Hence, hyperlactatemia is closely associated with disease severity but it is an epiphenomenon as the body attempts to protect itself. This article reviews lactate biochemistry, kinetics, pathophysiology, some practical aspects of measuring lactate, as well as its use in diagnosis, prognosis, and monitoring.

OBJECTIVE: To assess the in vitro effects of crystalloid and colloid IV fluids on the thromboelastographic (TEG) variables of canine whole blood. DESIGN: In vitro experimental study. SETTING: Veterinary teaching hospital. ANIMALS: Twenty-two healthy dogs. INTERVENTION: Citrated whole blood samples collected from healthy dogs were diluted with 3.4% hypertonic saline (HTS 3.4), 7% hypertonic saline (HTS 7), and 20% mannitol at 8% and 16% dilutions; hydroxyethyl starch 130/0.4 (HES 130/0.4) at 16% dilution; lactated Ringer's solution (LRS) at 16%, 33%, and 66% dilutions; and HTS 7-HES 130/0.4 at 25% and 50% dilutions. Kaolin-activated TEG analysis was concurrently performed on diluted and control (undiluted) samples. MEASUREMENTS AND MAIN RESULTS: Dilution of canine whole blood with LRS compared to control reduced α angle and MA at both 33% (P = 0.009 and P = 0.011, respectively) and 66% dilution (P

Objective – To evaluate the effect of body position on the arterial partial pressures of oxygen and carbon dioxide (PaO2, PaCO2), and the efficiency of pulmonary oxygen uptake as estimated by alveolar-arterial oxygen difference (A-a difference). Design – Prospective, randomized, crossover study. Setting – University teaching hospital, intensive care unit. Animals – Twenty-one spontaneously breathing, conscious, canine patients with arterial catheters placed as part of their management strategy. Interventions – Patients were placed randomly into lateral or sternal recumbency. PaO2 and PaCO2 were measured after 15 minutes in this position. Patients were then repositioned into the opposite position and after 15 minutes the parameters were remeasured. Measurements and Main Results – Results presented as median (interquartile range). PaO2 was significantly higher (P=0.001) when patients were positioned in sternal, 91.2 mm Hg (86.0–96.1 mm Hg), compared with lateral recumbency, 86.4 mm Hg (73.9–90.9 mm Hg). The median change was 5.4 mm Hg (1.1–17.9 mm Hg). All 7 dogs with a PaO2

CRYSTALLOID fluids contain water, electrolytes and non-electrolyte solutes, and can enter all body fluid compartments. They can be used to replace fluid deficits or to provide for ongoing losses, and play an important role in small animal veterinary practice. Replacement solutions are required for patients with deficits of either electrolytes, water or, most commonly, both. Maintenance solutions are indicated once an animal has been stabilised to provide for normal fluid and electrolyte demands, or if patients have solely pure water loss. Replacement solutions can be used as maintenance solutions provided they are supplemented with potassium and the animal is capable of excreting the extra sodium. This is possible in most cases, but extra care must be taken with patients with compensated congestive heart failure or those with hyper- or hyponatraemia, and in situations of pure water loss. This article describes the properties of commonly used crystalloid solutions and their indications. An article in the March issue of In Practice will review colloid solutions. Part 1, published in the last issue (In Practice, January 2008, volume 30, pp 16-19), discussed patient assessment and the principles of fluid therapy in small animals.

Initial and serial plasma lactate concentrations can be used to guide decision making in individual dogs with GDV but care is necessary in phrasing conversations with owners. Published data suggests that survival is more likely and the chance of complications less in dogs with an initial plasma lactate of4 mmol/L. An initial lactate6 mmol/L makes gastric necrosis and greater expense more likely. However, because of the overlap between groups and the good overall survival rates, exploratory laparotomy should always be recommended irrespective of the plasma lactate concentration. Falls in plasma lactate of greater than ~40% after fluid resuscitation are likely to indicate better survival. If the initial plasma lactate concentration is moderately to severely increased (5-10 mmol/L) and a sustained increase in plasma lactate occurs after fluid resuscitation, the cause should be aggressively pursued. Many dogs with persistent hyperlactatemia over 24-48 hours do not survive.

HAEMOGLOBIN-based oxygen-carrying (HBOC) solutions have been extensively developed and studied in the human medical field over the past three decades as a means of providing a readily available alternative to red blood cell (RBC) transfusion, due to increased concerns over disease transmission and limited supplies of human blood. Their use so far in human clinical medicine has been restricted by the lack of licensed products. Recently, an HBOC solution for the treatment of anaemia in dogs (Oxyglobin; Biopure) has been licensed in the UK. This article, based on the authors9 experience of using the product to date, discusses the clinical applications, and limitations, of this new addition to the veterinary clinician9s armoury.

Objective: To evaluate plasma sodium and glucose concentrations in dogs with congestive heart failure (CHF) prior to treatment and evaluate the differences between survivors and non-survivors. Design: Retrospective study. Animals: Fifty-nine dogs with CHF prior to receiving cardiac medication. Interventions: None. Measurements and main results: The mean plasma sodium concentration in dogs with CHF was below the reference range (144–156 mmol/L) and significantly lower (P=0.009) in non-survivors (141±6 mmol/L) compared with survivors (147±4 mmol/L). The mean plasma glucose concentration was above the reference range (76–117 mg/dL) and significantly higher (P=0.004) in non-survivors (128±52 mg/dL) compared with survivors (100±13 mg/dL). Forty-four percent of non-survivors had concurrent low plasma sodium and high plasma glucose concentrations, whereas no survivors had both abnormalities (P

Objective: To review the principles and practice of cardiopulmonary cerebral resuscitation (CPCR) in veterinary medicine, and to incorporate recommendations from the human International Guidelines 2000 Conference on cardiopulmonary resuscitation and emergency cardiovascular care. Data sources: Both clinical and experimental studies from the human and veterinary literature were reviewed for this manuscript. Summary: Cardiopulmonary cerebral resuscitation consists of basic life support measures, advanced life support measures, and post-resuscitation care. Part I of this article introduced the evidence-based recommendations from human medicine and reviewed basic life support. Part II of this article reviews advanced life support, including drug therapy and electrical defibrillation based upon the electrocardiographic rhythm present at the time of cardiopulmonary arrest (CPA). Post-resuscitation care is discussed, with a particular focus on optimizing perfusion to the brain, kidneys, and gastrointestinal tract. Several currently investigational methods that may improve future patient outcomes are also addressed. Conclusions: Advanced life support techniques provide methods to augment CPCR efforts. As with basic life support, recent recommendations to improve advanced life support in humans may be also be applied to veterinary patients. However, clinical research evaluating these interventions in veterinary CPCR is necessary. Post-resuscitation care requires vigilant monitoring and aggressive support to ensure vital organ perfusion and maximize patient outcomes.

Objective—To evaluate the effect of prednisone alone, compared with a combination of prednisone and vincristine, on platelet counts in bleeding dogs with severe primary immune-mediated thrombocytopenia (IMT). Design—Prospective case study. Animals—24 dogs with severe primary IMT. Procedure—All dogs received immunosuppressive doses of prednisone (1.5 to 2 mg/kg [0.7 to 0.9 mg/lb] of body weight, PO, q 12 h). In addition, 12 dogs received a single dose of vincristine (0.02 mg/kg [0.01 mg/lb], IV). Platelet count, transfusion requirement, and outcome were monitored. A response was defined as an increase in platelet count to ≥ 40,000/µl. Dogs in the prednisone group that failed to respond received 1 dose of vincristine on day 7. Results—Dogs that received prednisone and vincristine had a significantly faster increase in platelet count to ≥ 40,000/µl than dogs that received prednisone alone (mean ± SD, 4.9 ± 1.1 vs 6.8 ± 4.5 days, respectively). A similarly rapid response was observed in dogs that received vincristine on day 7 after treatment with prednisone alone failed. Furthermore, duration of hospitalization was reduced in the vincristine group, compared with the prednisone group (5.4 ± 0.3 vs 7.3 ± 0.5 days, respectively). No adverse effects attributable to vincristine were observed in any dog. Conclusions and Clinical Relevance—Administration of combined vincristine and prednisone is associated with more rapid increase in platelet numbers and shortened duration of hospitalization in dogs with IMT, compared with use of prednisone alone. Early use of vincristine seems warranted in dogs with severe primary IMT. (J Am Vet Med Assoc 2002; 220:477–481)

Objective—To determine the incidence of and risk factors for ventilatory failure in dogs undergoing surgery for treatment of cervical spinal disorders and to document ventilator management, clinical course, and long-term outcome of dogs that experienced ventilatory failure in association with cervical spinal disorders or their management. Design—Retrospective study. Animals—14 dogs. Procedure—Dogs with cervical spinal disorders that required positive-pressure ventilation (PPV) were identified, and signalment, concurrent diseases, neurologic status at initial examination, clinical course, pulmonary function before, during, and after PPV, management techniques, complications, and outcome were recorded. Dogs that underwent surgery and required PPV were compared with dogs that underwent cervical spinal surgery during the same period that did not require PPV. Results—14 dogs with cervical spinal disorders required PPV to treat hypoventilation, including 13 of 263 (4.9%) dogs that underwent surgery for cervical spinal disorders. Lesions between the second and fourth cervical vertebrae and treatment by means of a dorsal decompressive laminectomy were associated with a significantly increased risk of perioperative hypoventilation. Pulmonary gas exchange function was normal or nearly normal throughout the course of PPV in dogs that survived. Ten dogs survived, and 9 of the 10 regained neurologic function. All 9 dogs that regained neurologic function had deep pain perception on initial examination at the veterinary teaching hospital. Conclusions and Clinical Relevance—Results suggest that a small percentage of dogs with cervical spinal disorders may require perioperative ventilatory support. With prolonged PPV and aggressive management, a good outcome may be achieved in dogs similar to those described in the present study. (J Am Vet Med Assoc 2001;218:1598–1602).

Objectives To discuss the advantages and disadvantages of colloidal therapy in veterinary medicine. Databases used MEDLINE (1966-present), Commonwealth Agricultural Bureau Abstracts (1973-present), personal files.

Objective: To determine the effect of storage on ammonia concentration in canine packed red blood cell (pRBC) units. Design: In vitro and in vivo study. Setting: University Veterinary Teaching Hospital. Interventions: Ammonia concentration was measured in 7 units of canine pRBC prepared in citrate-phosphate-dextrose (CPD) and Adsola on Days 1 and 35 of storage. Ammonia was measured in 4 additional units of canine pRBC on Days 0, 7, 14, 21, 28, and 35. Plasma ammonia was also determined in 5 anemic dogs receiving pRBC. Measurements and Main Results: Ammonia concentration increased from 73 ± 15 mmol/L (mean ± SD) on Day 1 to 800 ± 275 mmpl/L on Day (p

Acquisition of vascular access in the emergent small animal patient is one of the keys to successful management of a population of patients that are often unstable with regard to their major body systems. Venous and intraosseus cannulation allow for the administration of a variety of fluids and potentially life-saving medications. In addition, central venous and arterial access also serve as conduits for atraumatic blood sampling and intravascular pressure monitoring. A thorough knowledge of vascular access theory, the dynamics of fluid flow, vascular anatomy, catheter selection criteria, and placement techniques are critical to the proper and safe use of the vascular access options available today to the small animal clinician.

Peritonitis is a clinical syndrome rather than a definitive diagnosis and, as such, the underlying cause must be identified. Many potential causes exist, and peritonitis may be classified as primary or secondary, local or diffuse, acute or chronic, or according to the causative agent. Peritonitis is one of the most common initiators of the systemic inflammatory response syndrome faced by the small animal practitioner. Because systemic inflammatory response syndrome is such a devastating disease process, aggressive stabilization, rapid definitive diagnosis, and prompt surgical and medical treatment are vital for optimizing outcome.

Summary We report the first case of colonic volvulus in a cat. A 12-year old spayed, female domestic shorthair cat with chronic bowel disease presentated with one-day history of lethargy and anorexia. Physical examination abnormalities included cachexia, poor perfusion, and poor skin turgor. A large, non painful, gas-filled, tubular structure, occupying the majority of the abdominal cavity was noted by palpation. Abdominal radiographs revealed a gas-filled displaced colon. Exploratory laparotomy confirmed a volvulus at the root of the colonic mysetery, along with a partial torsion of the distal colon. The majority of the colon was determined to be necrotic and was surgically resected. Due to persistent hypotension and perceived poor prognosis, the cat was euthanized.

Summary A retrospective analysis was conducted of all feline necropsies performed during a nine year period to identify cases of sever, acute, centrilobular (periacinar), hepatic necrosis (ACHN). After exclusion of cats with anemia, a series of seven cases of ACHN was identified. In addition, two similar cases were identified from tissue submitted for histopathology following, and eight had bile duct hyperplasia. Seven of the nine cats received diazepam prior to dath, and one received zolazepam. Of the seven cats that received diazepam, five were healthy prior to treatment and received oral diazepam for the treatment of inappropriate urination, intercat aggression, or skin disease. Two cats which received diazepam exhibited other clinical signs: one had chronic vomiting, and the other received diazepam after biochemical evidence of hepatocellular necrosis was present. Onset of clinical sings in cats receiving oral diazepam occurred 7–13 days following the initiation of treatment. Clinical signs and clinical biochemical analysis were compatible with severe hepatocellular necrosis and acute liver failure. All cats had lesions in other organs: five had pancreatic disease, five had cardiac disease, and five had renal disease. All cats died, or were euthanized, within 4 dyas of the onset of clinical signs and 2 days after presentation to a veterinarian. Fatal, acute, centrilobular hepatic necrosis appears to be a serious adverse reaction to diazepam therapy in certain cats.

This article reviews the diagnostic evaluation and critical care management necessary to optimize outcome in cases of potentially reversible, acute liver failure in dogs and cats. A definitive histopathologic diagnosis should always be pursued to allow evaluation of the reversibility of the underlying condition. Treatment of acute liver failure in dogs and cats is largely supportive and requires specific attention to each functional derangement. With the current advances in veterinary critical care, improved medical and technical management of the patient with acute liver should reduce both morbidity and mortality.

Objective— To report successful surgical treatment of double chambered right ventricle (DCRV) in a cat. Study Design— Clinical report. Animals— Cat with DCRV. Methods— DCRV was diagnosed in a 5-month-old male Maine Coon cat using echocardiography and angiocardiography. At 2 years, despite medical therapy, chylothorax developed. A section of the right ventricular free wall that spanned the fibromuscular obstruction was excised under total venous inflow occlusion (TVIO) using the incised pericardial patch technique. Results— Short-term recovery was complicated by return of chylothorax but this resolved after thoracocentesis and diuretic therapy. Three years after surgery, the cat is free of clinical signs and no longer on any medical therapy. Conclusions— Partial right ventriculectomy can be performed under TVIO through an incised pericardial patch. Clinical Relevance— DCRV in cat can be successfully treated by partial right ventriculectomy performed under TVIO through an incised pericardial patch.

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.

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.