James Edward Miles

Effect of propofol and remifentanil on cerebral perfusion and oxygenation in pigs: a systematic review

The objective of this review is to evaluate the existing literature with regard to the influence of propofol and remifentanil total intravenous anaesthesia (TIVA) on cerebral perfusion and oxygenation in healthy pigs. Anaesthesia has influence on cerebral haemodynamics and it is important not only in human but also in veterinary anaesthesia to preserve optimal regulation of cerebral haemodynamics. Propofol and remifentanil are widely used in neuroanaesthesia and are increasingly used in experimental animal studies. In translational models, the pig has advantages compared to small laboratory animals because of brain anatomy, metabolism, neurophysiological maturation, and cerebral haemodynamics. However, reported effects of propofol and remifentanil on cerebral perfusion and oxygenation in pigs have not been reviewed. An electronic search identified 99 articles in English. Title and abstract screening selected 29 articles for full-text evaluation of which 19 were excluded with reasons. Of the 10 peer-reviewed articles included for review, only three had propofol or remifentanil anaesthesia as the primary study objective and only two directly investigated the effect of anaesthesia on cerebral perfusion and oxygenation (CPO). The evidence evaluated in this systematic review is limited, not focused on propofol and remifentanil and possibly influenced by factors of potential importance for CPO assessment. In one study of healthy pigs, CPO measures were within normal ranges following propofol-remifentanil anaesthesia, and addition of a single remifentanil bolus did not affect regional cerebral oxygen saturation (rSO2). Even though the pool of evidence suggests that propofol and remifentanil alone or in combination have limited effects on CPO in healthy pigs, confirmative evidence is lacking.

Comparison of reliability of five patellar position indices at various stifle joint angles in pelvic limbs obtained from cadavers of red foxes (Vulpes vulpes)

OBJECTIVE To compare 5 patellar position indices at various stifle joint angles in cadavers of red foxes, determine measurement reliability, and assess the suitability of these indices for clinical use. SAMPLE Pelvic limbs from cadavers of 12 red foxes (Vulpes vulpes). PROCEDURES Patellar position in each limb at 7 stifle joint angles (30° to 148°) was assessed by use of the Insall-Salvati (IS), modified Insall-Salvati (mIS), de Carvalho (dC), patellotrochlear (PT), and Blackburne-Peel (BP) indices. RESULTS Values for all indices varied significantly on the basis of joint angle, but for IS and mIS indices, this was minor and nonsignificant between 52° and 130° and between 52° and 148°, respectively. The dC index increased linearly, and PT and BP indices varied polynomially with increases in stifle joint angle. Stifle joint angles measured from radiographs agreed well with the goniometrically set stifle joint angles up to approximately 100° and diverged thereafter. Intraobserver and interobserver agreement was substantial for all indices, and IS index was the most precise. CONCLUSIONS AND CLINICAL RELEVANCE IS and mIS index values were effectively independent of stifle joint angle, in contrast to dC, PT, and BP indices. The BP index varied nonsignificantly across a range of joint angles. To maximize angular accuracy, radiographs should not be obtained at joint angles > 100°. Although dC, PT, and BP indices appeared to be suitable for preoperative and postoperative evaluation of patellar position, BP index appeared to have the most promise for determination of patellar position in clinical applications.

Modulation of the intramedullary pressure responses by calcium dobesilate in a rabbit knee model of osteoarthritis.

Background and purpose The presence of bone marrow edema in patients with osteoarthritis is associated with pain and disease progression. Management of bone edema with the synthetic prostacyclin iloprost may be complicated by side effects. Calcium dobesilate, a treatment for chronic venous disease, shares some pharmacological actions with iloprost but appears to be better tolerated. Anecdotal reports have suggested that calcium dobesilate may be useful for medical management of osteoarthritis, possibly by reducing bone marrow edema, and this study was performed to investigate possible benefits of treatment. Methods The effects of a 6-week period of oral calcium dobesilate administration on tibial intramedullary pressure dynamics and physical joint characteristics were evaluated in 20 rabbits with unilaterally induced knee osteoarthritis that were randomly allocated to either a treatment group or a placebo control group. Treatment or placebo started 8 weeks after induction of osteoarthritis, and was followed by a 4-week washout period. Results Calcium dobesilate did not affect joint thickness or range of motion, nor individual pressure measurements, compared to placebo. Pressure ranges in the operated limb were greater than in the intact limb after 8 weeks, and approached those of the intact limb after 6 weeks of treatment with calcium dobesilate but not with placebo. Inter-limb differences were lower (p = 0.02) in the dobesilate group following the washout period. Interpretation Calcium dobesilate had a detectable effect on pressure dynamics in the subchondral bone of osteoarthritic joints in this model. The significance of these effects for pain and function should be established.

Proportion recovery and times to ambulation for non-ambulatory dogs with thoracolumbar disc extrusions treated with hemilaminectomy or conservative treatment: A systematic review and meta-analysis of case-series studies.

Thoracolumbar intervertebral disc extrusion is a common cause of spinal cord dysfunction in dogs. Peer-reviewed studies reporting treatment of predominantly chondrodystrophic dogs with disc extrusion with loss of ambulation with either hemilaminectomy or conservative treatment (rest, analgesics and anti-inflammatories) were evaluated in a systematic review of the literature. Generally, the level of evidence available was low with no controlled studies and only case series available. In the meta-analysis, there was a clear trend to a greater proportion of dogs recovering and returning faster to ambulation for dogs treated with hemilaminectomy than for conservatively treated dogs. The mean proportions that recovered for neurological grades 3, 4 and 5 were 93, 93 and 61% for those treated with hemilaminectomy, and 79, 62 and 10% for those treated conservatively (Grade 3 - non-ambulatory paraparetic dogs; grade 4 - paraplegic dogs with intact deep pain perception; grade 5 - paraplegic dogs without intact deep pain perception). Due to the use of case series, these results represent between-study comparisons, thereby increasing the risk of selection bias and other biases. Data presented in this review support the current recommendations for surgical management of non-ambulatory dogs with disc-extrusion, but controlled clinical studies comparing outcomes are necessary to confirm these findings.

Femoral rotation unpredictably affects radiographic anatomical lateral distal femoral angle measurements

OBJECTIVE To describe the effects of internal and external femoral rotation on radiographic measurements of the anatomical lateral distal femoral angle (a-LDFA) using two methods for defining the anatomical proximal femoral axis (a-PFA). METHODS Digital radiographs were obtained of 14 right femora at five degree intervals from 10° external rotation to 10° internal rotation. Using freely available software, a-LDFA measurements were made using two different a-PFA by a single observer on one occasion. RESULTS Mean a-LDFA was significantly greater at 10° external rotation than at any other rotation. The response of individual femora to rotation was unpredictable, although fairly stable within ±5° of zero rotation. Mean a-LDFA for the two a-PFA methods differed by 1.5°, but were otherwise similarly affected by femoral rotation. CLINICAL SIGNIFICANCE If zero femoral elevation can be achieved for radiography, a-LDFA measurements do not vary much with mild femoral rotation (±5°). Outside of this range, a-LDFA varies unpredictably with femoral rotation.

A comparison of anatomical lateral distal femoral angles obtained with four femoral axis methods in canine femora.

OBJECTIVES To report the repeatability and reproducibility of four different anatomical proximal femoral axis (a-PFA) methods for measuring anatomical lateral distal femoral angle (a-LDFA), and to compare a-LDFA values produced by each method at three different femoral elevation angles. METHODS Digital radiographs were obtained of seven dry canine femora at 0°, 12.5° and 25° elevations. Using image analysis software, landmarks defining four different a-PFA and the condylar axis were identified by two independent observers on two separate occasions. Corresponding a-LDFA were calculated for each femur, elevation and a-PFA. Repeatability and reproducibility parameters were calculated and compared statistically, along with the effect of technique and elevation on a-LDFA value. RESULTS Interobserver repeatability coefficients were subjectively better for three of the a-PFA methods at 2° compared to the fourth at 3.1°. Median a-LDFA increased significantly (p ≤ 0.002) with increasing femoral elevation for all a-PFA methods, with a median increase of 3.3°. The median difference in a-LDFA between a-PFA methods yielding the highest and lowest measurements was 2.6° over all three elevations. CLINICAL SIGNIFICANCE The combined effects of a-PFA choice, femoral elevation and measurement reproducibility may produce typical errors of ± 2.6°, which could have implications for the selection of candidates for corrective osteotomies. Clinicians need to be aware that values obtained with one method and femoral elevation may not be equivalent to values obtained with other methods or elevations.

The Quadriceps Angle: Reliability and Accuracy in a Fox (Vulpes vulpes) Pelvic Limb Model

OBJECTIVES To evaluate the effect of measurement technique and limb positioning on quadriceps (Q) angle measurement, intra- and interobserver reliability, potential sources of error, and the effect of Q angle variation. STUDY DESIGN Cadaveric radiographic study and computer modeling. ANIMALS Pelvic limbs from red foxes (Vulpes vulpes). METHODS Q angles were measured on hip dysplasia (HD) and whole limb (WL) view radiographs of each limb between the acetabular rim, mid-point (Q1: patellar center, Q2: femoral trochlea), and tibial tuberosity. Errors of 0.5-2.0 mm at measurement landmarks alone and in combination were modeled to identify the effect on Q angle. The effect of measured Q angles on the medial force exerted on the patella (F(MEDIAL)) was calculated. RESULTS The HD position yielded significantly (P < .001) more medial Q angles than the WL position. No significant difference was observed between Q1 and Q2, but Bland-Altman plots indicated they were not equivalent. Intra- and interobserver agreement was substantial. Q2 errors were inherently greater than Q1: the mid-point and tibial tuberosity are the most important sources of Q angle variability. Increasing Q angles significantly increased the exerted F(MEDIAL) (P < .0001, gradient 1.7%). CONCLUSIONS Measurements are reliable, but Q2 is more prone to error than Q1, and the 2 measurement techniques are not interchangeable. Positional errors must be kept below 1.3 mm (Q1) or 0.8 mm (Q2).

Radiographic, ultrasonographic, and anatomic assessment of femoral trochlea morphology in red foxes (Vulpes vulpes)

OBJECTIVE To compare repeatability and equivalency of measures of femoral trochlea depth and trochlear angle in red foxes (Vulpes vulpes) determined by use of radiography, ultrasonography, and digital photography of cadaver limbs. SAMPLE 24 pelvic limbs from 12 red fox cadavers. PROCEDURES Cranioproximal-craniodistal oblique (skyline) and lateromedial radiographic views of the stifle joint and ultrasonographic images at 5 locations along the femoral trochlea were used in the study. Spacing of the 5 locations was determined on the basis of patellar position with the stifle joint at various caudal angles ranging from 96° to maximal extension (approx 170°). Ultrasonographic measurements were compared with those obtained at matched locations on photographs of anatomic preparations. Trochlear depth was assessed with all 3 image formats, and trochlear angle (measured between the trochlear ridges and sulcus) was assessed on radiographs and ultrasonographic images. Patellar thickness was measured on radiographs. Values obtained were compared by means of ANOVA, modified Bland-Altman plots, and repeatability testing. RESULTS Depth measurement repeatability was considered good for all modalities. Small but significant differences between mean ultrasonographic trochlear depth and anatomic (photographic) measurements were found at 3 locations; 95% limits of agreement for paired anatomic and ultrasonographic measurements were wide. The ratio of trochlear depth to radiographic patellar thickness was approximately 30% for all modalities. Trochlear angle measurements were more variable than trochlear depth measurements, especially in the distal aspect of the trochlea. CONCLUSIONS AND CLINICAL RELEVANCE Paired anatomic and ultrasonographic measurements did not appear equivalent in this study, possibly attributable to imprecise probe location, which could limit quantitative use of ultrasonography in assessing proximal trochlear depth in a clinical setting.

Measurement repeatability of tibial tuberosity-trochlear groove offset distance in red fox (Vulpes vulpes) cadavers

OBJECTIVE To describe CT image reconstruction criteria for measurement of the tibial tuberosity-trochlear groove (TT-TG) offset distance, evaluate intra- and inter-reconstruction repeatability, and identify key sources of error in the measurement technique, as determined in vulpine hind limbs. ANIMALS 12 red fox (Vulpes vulpes) cadavers. PROCEDURES CT images of each hind limb in intact cadavers were obtained; at 1-week intervals, 3 reconstructions were performed that were based on 1 plane passing through the centers of the femoral head and medial condyle and parallel to the caudal femoral condyles, 1 plane aligned with the femoral trochlea, and a third orthogonal plane. Randomized and anonymized reconstructions were assessed for TT-TG offset distance with a single-image technique by 1 observer, and inter-reconstruction repeatability and intra- and inter-reconstruction measurement repeatability were assessed via the repeatability coefficient and intraclass correlation coefficient. RESULTS Multiplanar reconstructions of hind limb images were repeatedly made to within a few degrees of each other. Intra- and inter-reconstruction repeatability for TT-TG offset distance measurement was good. Repeatability was most affected by accurate identification of the tibial tuberosity and femoral trochlea landmarks. CONCLUSIONS AND CLINICAL RELEVANCE Results obtained from vulpine hind limb CT images indicated that reconstructions can be made with a high degree of repeatability when based on strictly defined and applied criteria. The TT-TG offset distance has potential as an objective assessment of alignment of the distal portion of the quadriceps mechanism; its use as an aid in case selection for corrective femoral osteotomy among dogs with medial patellar luxation warrants investigation.

Five patellar proximodistal positioning indices compared in clinically normal Greenland sled dogs

Patellar luxation in large-breed dogs is associated with abnormal proximodistal patellar positioning. Using a clinically normal population of Greenland sled dogs, measurement reliability and the effect of limb position were compared for five patellar proximodistal positioning indices based on the Insall-Salvati (IS), modified Insall-Salvati (mIS), de Carvalho (dC), patellotrochlear (PT) and Blackburne-Peel (BP) indices. Indices were measured at one knee angle in 44 dogs and two knee angles in 10 dogs. Index susceptibility to error was modelled for different errors in knee angle estimation. Two reported techniques for determining knee angle were compared in a fox hind limb model. Indices dC and PT were significantly affected by knee angle (P<0.001). Error susceptibility was the lowest for IS and the greatest for PT. Intra- and inter-observer agreements were moderate to substantial for all indices. Measurement precision was good for all indices except BP. Patellar ligament laxity significantly affected IS, mIS, dC and BP (P<0.05). Knee angle measurements were technique dependent, with a bias of 9° to 13° and limits of agreement of ±5°. All five indices were reliable, but precision varied. For pre- and post-operative comparison, dC showed less error susceptibility than PT and better precision than BP. An ideal index for clinical use remains to be defined; the best option is dC, although with limitations. The method of knee angle measurement must be defined prior to index measurement and comparison of index values. Index values may vary with species and/or body size.