22 Jan 2018
Alex Gough looks at a study into the shock index, one on antibiotic prescribing habits and another on mast cell tumours in his latest Research Review.
Alex Gough
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IMAGE: mnikolaev / Fotolia.
Identifying shock is vital, to intervene with fluid resuscitation quickly and to prompt investigation of the underlying cause.
The shock index is the ratio of heart rate to systolic blood pressure, and has been suggested to be a sensitive indicator of shock.
McGowan et al1 performed a prospective study of 20 client-owned dogs, which were donating blood, to assess the changes in shock index after donation and the sensitivity of the index.
Measurements of heart rate and systolic blood pressure were made pre-donation, immediately after completion of donation and 10 minutes after completion of donation. PCV, total protein and plasma lactate were measured pre-donation and 10 minutes after donation. The shock index was significantly increased at both measurements after donation. No significant difference in PCV pre and post-donation existed.
Lactate and total protein were significantly different, but within reference ranges. Using a cut-off of 1.064, shock index was 80% specific and 85% sensitive for blood loss.
The authors suggested that using a shock index of more than 1 is a sensitive and specific way of detecting blood loss.
Antibiotic resistance is an increasingly concerning problem in human and veterinary medicine. Guidelines have been produced for responsible antibiotic use.
Barzelai and Whittem2 performed a study to investigate the antibiotic prescribing habits of Australian vets and compared the results with the pattern of prescribing from 20 years earlier.
A questionnaire was sent to 1,380 vets in Victoria, with 259 replies received. Some poor prescribing practice was noted – for example, using amoxicillin-clavulanate to treat chronic prostatitis, even though this drug does not penetrate into the prostate very well.
However, it was noted some prescribing patterns had changed in the past 20 years. For example, use of antibiotics to treat idiopathic vestibular disease had fallen from 45% to 5%, and a fall from 87% to 36% for the treatment of acute tracheobronchitis.
The authors noted antibiotic use was largely in line with current recommendations, but some variation existed.
Pituitary tumours can lead to endocrine diseases, such as Cushing’s disease, even when they are small (microadenomas). However, some pituitary tumours are large and can lead to neurological effects by pressure on the brain (macroadenomas). In particular, enlargement of the pituitary gland can exert pressure on the hypothalamus, which is involved with regulation of heart rate and body temperature.
Benchekroun et al3 performed a study to assess the effect of having a macroadenoma or microadenoma on these two parameters. Two groups of dogs with pituitary-dependent hyperadrenocorticism were included in the study.
Dogs that had a macroadenoma were found to have a significantly lower heart rate and body temperature than those with microadenomas. Heart rates of lower than 84 beats per minute and a body temperature of 38.3°C on initial presentation were more likely to imply the presence of a macroadenoma, especially if neurological signs were present.
Mast cells contain histamine and disruption – in excision of a mast cell tumour, for example – can lead to immune reactions, including anaphylaxis. Antihistamines can be used to lower the risk of these events.
Sanchez et al4 performed a randomised blinded clinical trial of 16 dogs with mast cell tumours undergoing surgical excision. Half were given diphenhydramine hydrochloride and half a saline control solution IV 10 minutes after induction.
Cardiorespiratory variables were monitored and blood samples taken at various intervals for concentrations of diphenhydramine and histamine. During tumour dissection and surgical closure, the mean diastolic arterial blood pressure was lower in the diphenhydramine group compared to the control group. Plasma histamine concentrations were higher at baseline than during the procedure for both groups, but this was not significant.
The authors concluded the data showed administration of diphenhydramine prior to mast cell tumour excision had no clear cardiorespiratory benefits compared to a control.
The European Veterinary Renal Pathology Service (EVRPS) is a web-based registry for kidney biopsies.
Aresu et al5 used specimens submitted to the EVRPS to examine whether differences exist in clinicopathological findings related to histopathological findings. In total, 162 cases where both light and electron microscopy had been used were included in the study.
Specimens were grouped into immune-complex-mediated glomerulonephritis (ICGN), non-ICGN and renal lesions not otherwise specified (RL-NOS).
Albumin levels were lower in dogs with ICGN and urine protein to creatinine ratio was higher in these dogs than the other two groups. Albumin was also found to be lower in dogs with amyloidosis or membranous, membranoproliferative and mixed glomerulonephritis, compared to dogs with other morphological diagnoses, such as minimal change disease and juvenile nephropathy.
The authors concluded dogs with ICGN tended to have more severe hypoalbuminaemia, but a lot of overlap existed between the groups in clinicopathological findings.
It can be challenging to differentiate genuine seizure activity from other seizure-mimicking disorders – such as compulsive behaviour, cardiac-related disorders and movement disorders – even when a video of the event is observed.
James et al6 performed a retrospective case series of 81 dogs that were undergoing investigation of unusual behavioural events and had undergone wireless video-electroencephalography (EEG) recordings. In 58 (72%) of cases, the EEG was able to rule in or out epilepsy. In total, 25 of these dogs had epilepsy confirmed and 33 had no epileptiform EEG abnormalities during the abnormal events. Decreased frequency of abnormal behaviour was associated with a decreased likelihood of making a diagnosis.
The authors concluded wireless video EEG was helpful in the diagnosis of unusual behavioural events of suspected epileptic origin.
Immune-mediated haemolytic anaemia is caused by immune-mediated destruction of circulating red cells. However, sometimes the red cell precursors can be targeted by the immune system (precursor-targeted immune-mediated anaemia; PIMA), leading to a poorly or non-regenerative anaemia.
Lucidi et al7 performed a study to characterise the cytological and histological bone marrow features of PIMA. In total, 25 cases were identified that had the correct criteria for PIMA and phagocytosis of erythroid precursors (rubriphagocytosis) that was stage-selective.
Four bone marrow patterns were identified – hypocellular, normocellular and hypercellular erythroid lineage, and a fourth pattern with severe collagen myelofibrosis. Mild to severe collagen myelofibrosis was common. Evidence of immune-mediated haemolysis was rarely found. In total, 77% of dogs responded to immunosuppressive treatment.
The authors suggested slow response to immunosuppressive treatment should warrant further investigation.
l Use of some of the medications mentioned in this article would be under the cascade.
