Plasma, subcutaneous tissue and bone concentrations of ceftiofur sodium after regional limb perfusion in horses.

REASONS FOR PERFORMING STUDY: Regional limb perfusion (RLP) is an effective treatment option for injuries and infections of the distal limb in horses. Using ceftiofur sodium in RLP has been studied due to its superior spectrum of Gram-positive organisms compared to aminoglycosides, but it is not known if this antimicrobial drug adequately penetrates subcutaneous tissue and bone. OBJECTIVE: To determine the concentration of ceftiofur in plasma, subcutaneous tissue and bone in horses after RLP. STUDY DESIGN: Experimental prospective study. METHODS: Six healthy horses were used in this study. Under standing sedation, an Esmarch tourniquet was applied to both proximal metacarpi and RLP was performed in each forelimb by injecting either ceftiofur sodium (experimental limb) or saline (control limb) i.v. in the lateral palmar digital vein. The experimental limb was injected with 2 g ceftiofur diluted to 60 mL with sterile saline. The control limb was injected with 60 mL of sterile saline. The tourniquet was left in place for 30 min post injection. Plasma, subcutaneous tissue and cortical bone samples were collected immediately after tourniquet removal (0.5 h), 12 and 24 h post injection. Ceftiofur concentrations and its active metabolite desfuroylceftiofur were analysed using high performance liquid chromatography-tandem mass spectrometry and the results were compared between control and experimental limbs using a Wilcoxon signed rank test. RESULTS: The median plasma concentrations were greater than the minimum inhibitory concentration (MIC) for common pathogens (1 µg/mL) at 0 and 12 h post RLP. The median subcutaneous tissue concentrations were greater than MIC (1 µg/g) at all 3 time points in the experimental limb. The median bone concentration was above MIC (1 µg/g) at time 0 in the experimental limb but was below MIC at 12 and 24 h in the experimental limb. CONCLUSIONS: Ceftiofur administration via RLP maintained plasma concentrations above MIC for 12 h. Subcutaneous tissue concentrations above MIC were maintained for 24 h. Bone concentrations were only above MIC immediately after tourniquet removal. Further research is needed to evaluate ceftiofur administration via RLP and its implications in disease states.

Heterogeneity of intrapleural pressures during exercise.

We determined whether the caudodorsal region of the intrapleural space in exercising horses experiences larger pressure fluctuations than other regions and whether systematic phase-shifting of peak intrapleural pressures along the length of the thorax suggests the existence of locomotor-induced intrapleural pressure waves. We utilised percutaneous introducers and solid-state pressure-tip transducers implanted along the dorsal aspect of the thorax, mid-thorax or oesophagus to measure regional intrapleural pressures while 3 horses galloped on a flat treadmill at 13-14 m/s, then recorded pressures from the same catheters when horses exercised intensely (heart rate 170-190 beats/min) while swimming with no ground concussion. Pressure excursions in the caudodorsal region did not vary systematically from other regions during galloping or swimming, nor more than a few torr between different locations. During swimming, peak expiratory pressures were higher than during galloping (68-79 vs. 26-32 torr), and horses breathed explosively at frequencies 5 times slower than while galloping (28 vs. 120/min). During galloping, individual catheter locations registered locomotor concussion; however, this was variable and did not indicate a systematic pressure wave passing through the lung or intrapleural space.

Dual-energy x-ray absorptiometry in osteopetrosis.

We have used dual-energy x-ray absorptiometry (DXA) in evaluation and follow-up of a patient with osteopetrosis, before and after cord blood transplantation. Other methods of follow-up in such cases have been described, but the use of DXA has not previously been reported. We have shown that DXA offers a safe means of assessing disease progression, the timing of treatment, and response after therapy for osteopetrosis.

Transcranial Doppler, MRA, and MRI as a screening examination for cerebrovascular disease in patients with sickle cell anemia: an 8-year study.

OBJECTIVE: The authors previously reported five transcranial Doppler ultrasonography (TCD) findings as significant in detecting clinical cerebrovascular disease in a 4-year study in patients with sickle cell disease. This is a follow-up to evaluate the validity of the original findings over another 4-year period during which the study population doubled. A clinical follow-up of the original asymptomatic sickle cell patients with positive TCD, MRA, and MRI was also made. MATERIALS AND METHODS: Over an 8-year period TCD, MRI, and MRA were prospectively performed in 90 sickle cell patients who were clinically asymptomatic for stroke and in 27 sickle cell patients with clinical stroke. RESULTS: Of the 4 out of original 46 control patients in 1992 who had positive MRA and TCD, 3 have subsequently had clinical stroke. None of the 9 original patients with positive TCD and positive MRI but negative MRA have developed stroke. All five original TCD indicators of disease were still significant (P < 0.05) for detecting clinical disease: maximum velocity in ophthalmic artery (OA) > 35 cm/s, mean velocity in middle cerebral artery (MCA) > 170 cm/s, resistive index (RI) in OA < 50, velocity in OA greater than in MCA, and velocity in posterior cerebral (PCA), vertebral, or basilar arteries greater than in MCA. An RI of < 60 in the DA was also now found to be significant [corrected]. Four additional factors were also significant: turbulence, PCA or ACA without MCA, RI < 30, and maximum velocity in MCA > 200 cm/s. CONCLUSION: Positive MRA with a positive TCD in an asymptomatic patient in long-term follow-up suggests a trend for developing clinical stroke. A 4- to 8-year follow-up of nine patients with positive TCD, positive MRI, but not positive MRA did not show development of clinical stroke. Nine Doppler findings are significant in screening for clinically symptomatic vascular disease in sickle cell patients. It is recommended that children with sickle cell disease be screened for cerebrovascular disease with TCD. If one or two indicators of abnormality are present, MRA is recommended. If the MRA is positive, the patient may be considered for transfusion therapy or other treatment for prevention of stroke.