Evaluation of a free vascularized medial tibial bone graft in dogs.

OBJECTIVE: To develop a free vascularized tibial bone graft based on the periosteal saphenous blood supply. STUDY DESIGN: Preliminary anatomic study of medial tibial blood supply. In vivo comparison of a vascularized and avascular tibial bone graft. ANIMALS: Nine canine cadavers; 14 healthy adult dogs that weighed 25 to 32 kg. METHODS: An anatomic study of the vascular supply of the medial aspect of the tibia was performed using the Spalteholz technique. A bone graft consisting of the medial aspect of the tibia was transferred to a mandibular defect as a vascularized graft in 7 dogs and as an avascular graft in 7 dogs. Bone scans were performed to evaluate graft perfusion. Radiographic evaluation of the mandibles and tibias was performed. The dogs were killed after 60 days, five mandibles from each group were examined histologically, and two from each group were evaluated using the Spalteholz technique. RESULTS: The saphenous vascular pedicle provides vascular perfusion to the medial tibial cortex. Bone scans and radiographic evaluations were consistent with viable bone in the vascularized grafts, and nonviable bone in the avascular grafts. Histological examination revealed live, healing bone in vascular grafts and necrotic bone in avascular grafts. Spalteholz evaluation revealed many small arborizing vessels in the vascular grafts and no organized vasculature in the avascular grafts. CONCLUSIONS: The vascularized medial tibial cortical bone graft survived and proceeded to bony union in the mandibular body defect more readily than the avascular graft in this experimental model. CLINICAL RELEVANCE: A vascularized medial tibial bone graft is a suitable free graft for use in reconstructing bone defects in dogs.

Evaluation of a hypertonic saline-dextran solution for treatment of dogs with shock induced by gastric dilatation-volvulus.

OBJECTIVE: To test the hypothesis that small volumes of hypertonic saline-dextran (HSD) solution can be used to effectively resuscitate dogs in shock induced by gastric dilatation-volvulus (GDV), and, compared with administration of large volumes of lactated Ringer's solution (LRS), can be used to limit the overall volume of fluid needed for resuscitation. DESIGN: Prospective, clinical study. ANIMALS: 15 dogs with GDV-induced shock. PROCEDURE: Initially, HSD solution (5 ml/kg of body weight) or LRS (60 to 90 ml/kg) was administered. All dogs then received a maintenance administration (20 ml/kg/h) of LRS. Cardiorespiratory, blood gas, and serum biochemical analyses were performed over a 4-hour period after initiation of treatment. RESULTS: Systolic arterial and central venous pressures and plasma volume increased more rapidly in dogs in the HSD + LRS group. The cumulative dose of fluids administered to dogs in the HSD + LRS group was significantly less than that administered to dogs in the LRS group. Serum sodium and chloride concentrations and osmolality increased significantly in dogs in the HSD + LRS group, but not in dogs in the LRS group. Ventricular arrhythmias were detected in both groups of dogs, but did not appear to be induced by either form of fluid therapy. CLINICAL IMPLICATIONS: Administration of HSD rapidly restored cardiorespiratory function and induced resuscitation equivalent to administration of large volumes of LRS. Use of HSD solutions to treat dogs in GDV-induced shock may be more efficient than use of isotonic fluids. Administration of HSD solution was not associated with noticeable complications.

Factors associated with perioperative mortality in dogs with surgically managed gastric dilatation-volvulus: 137 cases (1988-1993).

OBJECTIVE: To evaluate factors associated with perioperative mortality in dogs with gastric dilatation-volvulus and to determine the influence of treatment differences between university and private specialty practices on outcome. DESIGN: Retrospective analysis of medical records. ANIMALS: 137 dogs with gastric dilatation-volvulus. PROCEDURE: Signalment; frequency of preoperative and postoperative treatments and complications; intraoperative findings; surgical technique; and hematologic, serum biochemical, and electrocardiographic results were recorded, evaluated for association with mortality, and compared between institutions. RESULTS: Mortality did not differ between institutions, and overall mortality was 18% (24/137). Surgical techniques differed between institutions, but were not associated with mortality. Gastric necrosis was associated with significantly higher mortality (46%; 13/28). When partial gastrectomy or splenectomy was performed, mortality (35 and 32% or 8/23 and 10/31, respectively) was significantly increased. Splenectomy was performed in 11 of 23 dogs requiring partial gastrectomy, and when both procedures were performed, mortality (55%; 6/11) was significantly increased. Preoperative cardiac arrhythmias were associated with significantly higher mortality (38%; 6/16). Mortality in dogs > 10 years old was not significantly greater than that in younger dogs. CLINICAL IMPLICATIONS: Patient management differences between practices did not seem to influence survival in dogs with surgically managed gastric dilatation-volvulus. Signalment, including age, did not influence mortality. Gastric necrosis, gastric resection, splenectomy, and preoperative cardiac arrhythmias were associated with mortality > 30%.

Vagal innervation influences the whole body oxygen consumption-delivery relationship in the dog.

Vagotomy alters regional blood flow distribution by interrupting the tonic central inhibitory effect of cardiopulmonary vagal afferent nerves on sympathetic outflow predominantly to the renal, splanchnic, and cutaneous circulations. We hypothesized that the alteration of blood flow distribution by vagotomy would lead to disruption of the oxygen consumption-oxygen delivery relationship (VO2/DO2), increase critical DO2 (DO2Crit), and decrease whole-body oxygen extraction ratio (O2ER). Nineteen chloralose-anesthetized, paralyzed, splenectomized dogs were submitted to either bilateral vagosympathectomy (n = 7), bilateral vagotomy (n = 6), or sham denervation (n = 6) following baseline cardiorespiratory parameter measurement. VO2 was measured by indirect calorimetry and carotid blood flow by ultrasonic flow probe. Incremental hemorrhages (1-5 mL/kg) were performed to determine the VO2/DO2 relationship. Cardiorespiratory parameters were measured after each hemorrhage at steady-state VO2. DO2Crit was derived from the VO2/DO2 relationship using a best-fit regression analysis technique. The average DO2Crit values of the vagotomy (9.1 +/- .54) and vagosympathectomy (11.5 +/- 1.2 mL/min/kg) groups were significantly greater than the control group (7.72 +/- .43). After hemorrhage had been performed to a point that decreased mean arterial pressure to approximately 70 mmHg from baseline values, carotid blood flow in the vagosympathectomy group was significantly greater than the control group. We conclude that vagotomy disrupts the VO2/DO2 relationship. Vagosympathectomy causes a severe disruption of the VO2/DO2 relationship, probably by the combined effect of vagotomy and interruption of sympathetic nervous system control of blood flow to the head and neck.

Comparative effects of 7% NaCl in 6% dextran 70 and 0.9% NaCl on oxygen transport in endotoxemic dogs.

We compared the effects of 7% NaCl in 6% dextran 70 (HSD) and 0.9% NaCl (IS) resuscitation of endotoxic dogs on hemodynamic and cardiorespiratory parameters and the oxygen consumption-delivery relationship. Escherichia coli endotoxin (3 mg.kg-1, intravenously) was infused over 5 min into 13 paralyzed, chloralose-anesthetized, splenectomized dogs. Six additional dogs received a sham endotoxin infusion (saline) and served as controls. After 30 min, the endotoxic animals were resuscitated to 150% of their baseline cardiac output (CO) and maintained at this CO for 30 min using 7% NaCl in 6% dextran 70 (HSD at 1 ml.kg-1.min-1; n = 7) or 0.9% NaCl (IS at 4 ml.kg-1.min-1; n = 6). Oxygen consumption (VO2), measured by indirect calorimetry, hemodynamic parameters, and oxygen delivery (DO2), improved in similar temporal patterns in both groups during resuscitation and VO2 reached steady-state values. Oxygen delivery, VO2, mean arterial pressure, and cardiac output did not significantly differ between groups at the end of resuscitation, but VO2 increased significantly from baseline values only in the HSD group. The total volume of HSD administered averaged 10.0 +/- 0.2 ml.kg-1 which was significantly less than the volume of IS, which averaged 67.2 +/- 9.3 ml.kg-1. Incremental hemorrhages (2-5 ml.kg-1) were then performed in all dogs to determine the oxygen consumption-delivery relationship and the critical level of oxygen delivery (DO2Crit). The average DO2Crit values of the HSD, IS, and control groups were 9.42, 9.15, and 6.82 ml.min-1.kg-1, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)