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Abstract

Objective—To quantify left ventricle (LV) volumes by use of 1-D, 2-D, and 3-D echocardiography versus MRI in dogs.

Animals—10 healthy Beagles.

Procedures—During anesthesia, each dog underwent an echocardiographic examination via the Teichholz method, performed on the basis of standard M-mode frames (1-D); the monoplane Simpson method of disk (via 2-D loops); real-time triplane echocardiography (RTTPE) with a 3-D probe; and real-time 3-D echocardiography with a 3-D probe. Afterward, cardiac MRI was performed. Values for the LV end-diastolic volume (EDV), end-systolic volume (ESV), and ejection fraction (EF) were compared between each echocardiographic method and the reference method (cardiac MRI).

Results—No significant differences for EDV, ESV, and EF were detected between RTTPE and cardiac MRI. Excellent correlations (r = 0.97, 0.98, and 0.95 for EDV, ESV, and EF, respectively) were found between RTTPE and values for cardiac MRI. The other echocardiographic methods yielded values significantly different from cardiac MRI and results correlated less well with results of cardiac MRI for EDV, ESV, and EF. Use of the Teichholz method resulted in LV volume overestimation, whereas the Simpson method of disk and real-time 3-D echocardiography significantly underestimated LV volumes.

Conclusions and Clinical Relevance—Use of RTTPE yielded excellent correlations and nonsignificant differences with cardiac MRI and is a suitable method for routine veterinary cardiac examination.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate the influence of various anesthetic protocols and 3 multiples of isoflurane minimum alveolar concentration (MAC) before and after supramaximal stimulation on electroencephalographic (EEG) variables in dogs.

Animals—6 healthy adult Beagles (mean ± SD body weight, 16.3 ± 1.0 kg).

Procedures—All dogs underwent 3 anesthesia sessions with a minimum of 1 week separating sessions: isoflurane alone, isoflurane and a constant rate infusion of dexmedetomidine (3 μg/kg/h, IV; ID), and isoflurane and a constant rate infusion of remifentanil (18 μg/kg/h, IV; IR). The MAC of isoflurane was determined via supramaximal electrical stimulation. Quantitative variables (frequency bands and their ratios, median frequency, 95% spectral edge frequency [SEF], and an EEG index) were determined directly before and after supramaximal stimulation at 0.75, 1.0, and 1.5 times the MAC for each session of 20-second epochs.

Results—Mean ± SD isoflurane MACs for isoflurane alone, ID, and IR were 1.7 ± 0.3%, 1.0 ± 0.1%, and 1.0 ± 0.1%, respectively. Prestimulation 95% SEF decreased significantly with increasing MAC during the isoflurane alone and ID sessions. Significant decreases in δ frequency band (0.5 to 3.5 Hz) presence and significant increases in β frequency band (> 12.5 Hz) presence, median frequency, and 95% SEF after stimulation were dependent on the MAC and anesthetic protocol. The EEG index had the strongest correlation with increasing MAC during the isoflurane-alone session (ρ = −0.89) and the least in the IR session (ρ = −0.15).

Conclusions and Clinical Relevance—Anesthesia with isoflurane alone resulted in the greatest overall EEG depression of all protocols. Use of remifentanil depressed the EEG response to nociceptive stimulation more strongly than did dexmedetomidine. The EEG variables evaluated did not appear useful when used alone as indicators of anesthetic depth in dogs.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate the influence of 3 anesthetic protocols and multiples of minimum alveolar concentration (MAC) on heart rate variability (HRV) with and without nociceptive stimulation in dogs.

Animals—6 healthy adult Beagles.

Procedures—Each dog was anesthetized 3 times: with isoflurane alone, with isoflurane and a constant rate infusion of dexmedetomidine (IsoD; 3 μg/kg/h, IV), and with isoflurane and a constant rate infusion of remifentanil (IsoR; 18 μg/kg/h, IV). Individual MAC was determined via supramaximal electrical stimulation. Sinus rhythm–derived intervals between 2 adjacent R-R intervals were exported from ECG recordings. Selected HRV time and frequency domain variables were obtained (at 2-minute intervals) and analyzed offline with signed rank tests before and after stimulation at 0.75, 1.0, and 1. 5 MAC for each anesthetic session.

Results—The isoflurane session had the overall lowest prestimulation SDNN (SD of all R-R intervals) values. Prestimulation SDNN values decreased significantly with increasing MAC in all sessions. For the IsoD session, SDNN (milliseconds) or high-frequency power (milliseconds2) was inversely correlated with MAC (Spearman rank correlation coefficient for both variables, −0.77). In the isoflurane and IsoR sessions, heart rate increased significantly after stimulation. In the IsoD session, poststimulation SDNN was increased significantly, compared with prestimulation values, at 0.75 and 1.0 MAC.

Conclusions and Clinical Relevance—On the basis of SDNN and high-frequency power values, anesthetic levels between 0.75 and 1.5 MAC within the same anesthetic protocol could be differentiated, but with a large overlap among protocols. Usefulness of standard HRV variables for assessment of anesthetic depth and nociception in dogs is questionable.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To compare response rates and remission and survival times in dogs with lymphoma treated with a continuous, multiagent, doxorubicin-based chemotherapeutic protocol or with a short-term single-agent protocol incorporating doxorubicin.

Design—Nonrandomized controlled clinical trial.

Animals—114 dogs with lymphoma.

Procedures—Dogs were treated with a chemotherapeutic protocol consisting of L-asparaginase, vincristine, cyclophosphamide, doxorubicin, methotrexate, and prednisolone (n = 87) or doxorubicin alone (27).

Results—63 of 86 (73%) dogs treated with the multiagent protocol (data on response was unavailable for 1 dog) and 14 of 27 (52%) dogs treated with the single-agent protocol had a complete remission. Dogs with lymphoma classified as substage ≤ and dogs with a high BUN concentration at the time of initial diagnosis were significantly less likely to have a complete remission. No significant difference in remission or survival time could be demonstrated between treatment groups. Incidence of hematologic and gastrointestinal tract toxicoses did not differ between treatment groups, with the exception that vomiting was more common among dogs treated with the multiagent protocol.

Conclusions and Clinical Relevance—In this population of dogs, we were not able to identify any significant difference in remission or survival times between dogs with lymphoma treated with a continuous, multiagent chemotherapeutic protocol and dogs treated with a short-term single-agent protocol involving doxorubicin.

Full access
in Journal of the American Veterinary Medical Association