Use of aortic flow indexes derived from transthoracic echocardiography to evaluate response to a fluid challenge in anesthetized dogs.

OBJECTIVE: To evaluate the ability of transthoracic echocardiographic aortic flow measurements to discriminate response to a fluid challenge (FC) in healthy anesthetized dogs. STUDY DESIGN: Prospective experimental study. ANIMALS: A total of 48 isoflurane-anesthetized dogs (14.2-35.0 kg) undergoing elective surgery. METHODS: Fluid responsiveness was evaluated before surgery by FC (lactated Ringer's 10 mL kg-1 intravenously over 5 minutes). Percentage increases in transpulmonary thermodilution stroke volume (ΔSVTPTD) >15% from values recorded before FC defined responders to volume expansion. A group of 24 animals were assigned as nonresponders (ΔSVTPTD ≤15%). When ΔSVTPTD was >15% after the first FC, additional FC were administered until ΔSVTPTD was ≤15%. Final fluid responsiveness status was based on the response to the last FC. Percentage increases after FC in aortic flow indexes [velocity time integral (ΔVTIFC) and maximum acceleration (ΔVmaxFC)] and in mean arterial pressure (ΔMAPFC) were compared with ΔSVTPTD. RESULTS: After one FC, 24 animals were responders. For nonresponders, ΔSVTPTD was ≤15% after one, two and three FCs in eight/24, 15/24 and one/24 animals, respectively. The FC that defined responsiveness increased ΔSVTPTD by 29 (18-53)% in responders and by 8 (-3 to 15)% in nonresponders [mean (range)]. The area under the receiver operating characteristics curve (AUROC) of ΔVTIFC (0.901) was larger than the AUROCs of ΔVmaxFC (0.774, p = 0.041) and ΔMAPFC (0.519, p < 0.0001). ΔMAPFC did not predict responsiveness (p = 0.826). Best cut-off thresholds for discriminating responders, with respective zones of diagnostic uncertainty (gray zones) were >14.7 (10.8-17.6)% for ΔVTIFC and >8.6 (-0.3 to 14.7)% for ΔVmaxFC. Animals within the gray zone were 17% (ΔVTIFC) and 50% (ΔVmaxFC). CONCLUSIONS AND CLINICAL RELEVANCE: Changes in VTI induced by FC can determine responsiveness with reasonable accuracy in dogs and could play an important role in goal-directed fluid therapy.

Comparison of the diagnostic accuracy of dynamic and static preload indexes to predict fluid responsiveness in mechanically ventilated, isoflurane anesthetized dogs.

OBJECTIVE: To compare the diagnostic accuracy of pulse pressure variation (PPV), stroke volume variation from pulse contour analysis (SVVPCA), plethysmographic variability index (PVI), central venous pressure (CVP) and global end-diastolic volume index measured by transpulmonary thermodilution (GEDVITPTD) to predict fluid responsiveness (FR) in dogs. STUDY DESIGN: Prospective study. ANIMALS: A group of 40 bitches (13.8-26.8 kg) undergoing ovariohysterectomy. METHODS: Anesthesia was maintained with isoflurane under volume-controlled ventilation (tidal volume 12 mL kg-1; inspiratory pause during 40% of inspiratory time; inspiration:expiration ratio 1:1.5). Transpulmonary thermodilution cardiac output was recorded through a femoral artery catheter. FR was evaluated by a fluid challenge (lactated Ringer's, 20 mL kg-1 over 15 minutes) administered once (n = 21) or twice (n = 18) before surgery. Individuals were responders if stroke volume index measured by transpulmonary thermodilution increased >15% after the last fluid challenge. RESULTS: Of the 39 animals studied, 21 were responders and 18 were nonresponders. Area under the receiver operating characteristics curve (AUROC) was 0.976, 0.906, 0.868 and 0.821 for PPV, PVI, CVP and SVVPCA, respectively (p < 0.0001 from AUROC = 0.5). GEDVITPTD failed to predict FR (AUROC: 0.660, p = 0.078). Best cut-off thresholds discriminating responders and nonresponders, with respective zones of diagnostic uncertainty (gray zones) were: PPV >16% (15-16%), PVI >11% (10-13%), SVVPCA >10% (9-18%) and CVP ≤1 mmHg (0-3 mmHg). Percentage of animals within gray zone limits was 13% (PPV), 28% (PVI), 51% (SVVPCA) and 67% (CVP). CONCLUSIONS AND CLINICAL RELEVANCE: PPV has better diagnostic accuracy to predict FR (conclusive results in nearly 90% of population) than other preload indexes in healthy dogs. When invasive blood pressure is unavailable, PVI will predict FR with reasonable accuracy (conclusive results in approximately 70% of the population). PPV and PVI values above gray zone limits (>16% and >13%, respectively) can reliably predict responders to volume expansion.

Effect of platelet-rich plasma on the healing of mandibular defects treated with fresh frozen bone allograft: a radiographic study in dogs.

The purpose of this study was to radiographically analyze the effect of autologous platelet rich plasma (PRP) on the healing of fresh frozen bone allograft (FFBA) placed in surgically created resection defects in mandibles of dogs. Bilateral resection defects measuring 1.5 cm × 1 cm were surgically created on the inferior border of the mandible in 10 adult male dogs. The defects were randomly divided into three groups: C, FFBA, and FFBA/PRP. In Group C, the defect was filled by blood clot only. In Group FFBA, the defect was filled with particulate fresh frozen bone allograft. In Group FFBA/PRP, it was filled with particulate fresh frozen bone allograft combined with PRP. At 90 days postoperative, standardized radiographs of the mandibles were obtained and results were quantitatively evaluated. Analysis of digitized radiographs indicated that non-PRP grafts were significantly less dense than the PRP grafts. Group FFBA/PRP also presented a statistically greater mineralized tissue area than Groups C and FFBA. Within the limits of this study, it can be concluded that PRP enhanced the healing of FFBA in resection defects in mandibles of dogs.

Effect of lidocaine on the minimum alveolar concentration of sevoflurane in dogs.

OBJECTIVE: To investigate the effects of a low-dose constant rate infusion (LCRI; 50 microg kg(-1) minute(-1)) and high-dose CRI (HCRI; 200 microg kg(-1) minute(-1)) lidocaine on arterial blood pressure and on the minimum alveolar concentration (MAC) of sevoflurane (Sevo), in dogs. STUDY DESIGN: Prospective, randomized experimental design. ANIMALS: Eight healthy adult spayed female dogs, weighing 16.0 +/- 2.1 kg. METHODS: Each dog was anesthetized with sevoflurane in oxygen and mechanically ventilated, on three separate occasions 7 days apart. Following a 40-minute equilibration period, a 0.1-mL kg(-1) saline loading dose or lidocaine (2 mg kg(-1) intravenously) was administered over 3 minutes, followed by saline CRI or lidocaine LCRI or HCRI. The sevoflurane MAC was determined using a tail clamp. Heart rate (HR), blood pressure and plasma concentration of lidocaine were measured. All values are expressed as mean +/- SD. RESULTS: The MAC of Sevo was 2.30 +/- 0.19%. The LCRI reduced MAC by 15% to 1.95 +/- 0.23% and HCRI by 37% to 1.45 +/- 0.21%. Diastolic and mean pressure increased with HCRI. Lidocaine plasma concentration was 0.84 +/- 0.18 for LCRI and 1.89 +/- 0.37 microg mL(-1) for HCRI. Seventy-five percent of HCRI dogs vomited during recovery. CONCLUSION AND CLINICAL RELEVANCE: Lidocaine infusions dose dependently decreased the MAC of Sevo, did not induce clinically significant changes in HR or arterial blood pressure, but vomiting was common during recovery in HCRI.