Veterinary Surgery

Objective—To determine what effect the timing of carprofen administration has on the severity of postoperative pain in dogs undergoing ovariohysterectomy and to investigate the pharmacokinetics of carprofen under these conditions.

Study Design—A prospective, randomized, double‐blind, clinical trial.

Animals—Sixty‐two adult bitches weighing between 10 and 25 kgs, undergoing elective ovariohysterectomy.

Methods—Examinations were performed for 20 hours postoperatively using subjective visual assessment scoring systems (DIVAS) and objective mechanical nociceptive threshold measurements. Forty dogs were assigned to one of three groups: (1) preoperative carprofen; (2) postoperative carprofen; and (3) no analgesics (saline injections). The dose of carprofen was 4.0 mg/kg subcutaneously. In another 22 bitches, the pharmacokinetics of carprofen given preoperatively or postoperatively at the same dose were examined.

Results—The dogs given carprofen preoperatively had lower pain scores than the other groups, significantly so at 2 hours postextubation (P< .01 andP< .05, Kruskal‐Wallis and post hoc Dunn's). Mechanical pain thresholds measured at the distal tibia showed the development of hyperalgesia at 12 and 20 hours postextubation; this was prevented by both the preoperative (P< .05 at 12 and 20 hours, Kruskal‐Wallis) and postoperative (P<.05 at 20 hours, Kruskal‐Wallis) administration of carprofen. Mechanical pain threshold testing at the wound showed a significant analgesic effect of carprofen. Plasma concentrations of carprofen were not directly related to analgesia; maximum plasma concentration, the area under the curve to the last data point, and area under the first moment curve up to the last data point were all significantly higher in the dogs given carprofen postoperatively (P< .05, Mann‐Whitney).

Conclusion—Preoperative administration of carprofen has a greater analgesic effect than postoperative administration in the early postoperative period in dogs undergoing ovariohysterectomy. Plasma levels of carprofen are not related to the degree of analgesia achieved. Clinical Relevance—Carprofen provides effective analgesia after canine ovariohysterectomy. The timing of analgesic administration is important to optimize the control of postoperative pain.

Objective—To determine the accuracy of three indirect blood pressure monitoring techniques (oscillometric technique [OS], Doppler [DOP], and optical plethysmography [OP] [blood pressure determined with a pulse oximeter waveform]) when compared with direct arterial pressure measurement in cats.

Study Design—Prospective study.

Animal Population—Eight healthy (five female, three male), domestic short‐hair cats, weighing 3.5 ± 0.8 kg

Methods—Cats were anesthetized with isoflurane. The inspired concentration of isoflurane was adjusted to produce mild hypotension (80 to 100 mm Hg direct systolic), moderate hypotension (60 to 80 mm Hg direct systolic), and severe hypotension (<60 mm Hg direct systolic). Indirect pressure measurements were obtained from the thoracic limb and compared with concurrent direct measurement using regression analysis and a modification of Bland and Altman's technique.

Results—All three techniques underestimated systolic pressure. OS produced the best prediction of systolic pressure with a bias ± precision of ‐15.9 ± 8.1 mm Hg. DOP and OP were relatively inaccurate with a bias ± precision of ‐25 ± 7.4 mm Hg and ‐25 ± 7.5 mm Hg. All three techniques correlated well with direct pressure with r values of 0.81, 0.88, and 0.88 for OS, DOP, and OP. DOP and OP provided an accurate prediction of direct mean arterial pressure with a bias ± precision of ‐0.8 ± 6 mm Hg and 0.6 ± 5.5 mm Hg. Correlation was good between DOP and mean arterial pressure with r = 0.89. Correlation was also good between OP and mean arterial pressure with r = 0.90.

Conclusions—OS provided the most accurate prediction of direct systolic pressure. DOP and OP provided a good prediction of mean arterial pressure in the cat.

Clinical Relevance—All three of these techniques are useful for detecting trends. Direct monitoring of blood pressure should be considered if accurate blood pressure measurement is required.

Objectives—To investigate the histologic diagnosis and incidence of new mammary tumor growth in the remaining mammary chain tissue after regional mastectomy.

Study Design—Prospective clinical study.

Animals—Female dogs (n=99) that had excision of a single mammary tumor.

Methods—Female dogs that had regional mastectomy to remove a single tumor were followed for ≥1 year postoperatively. Data regarding tumor type, tumor recurrence, and development of metastasis were recorded.

Results—Fifty‐seven (58%) dogs developed a new tumor in the ipsilateral mammary chain after the 1st surgery; 77% had repeat surgery. There was no significant correlation between the time to new tumor development and the histologic diagnosis for the 1st and 2nd tumor types. In 31 dogs, the histologic diagnosis for initial and subsequent tumors was identical and there was a significant correlation such that dogs with an initial malignant tumor are likely to develop another malignant tumor (P=.0089). The histologic classification of the new tumor was likely to be malignant if it was located close to the side where the initial tumor had been removed (P=.026).

Conclusions—Our results show that 58% of dogs developed a new tumor in the remaining mammary glands of the ipsilateral chain after regional mastectomy for removal of a single tumor.

Clinical Relevance—This should be taken into account when deciding on the surgical management (radical or regional mastectomy) in dogs with single mammary tumors.

A biomechanical analysis of the results of an over‐the‐top procedure for replacement of the cranial cruciate ligament (CCL) in the dog is presented. Using 15 adult mongrel dogs, the CCL in one stifle joint was reconstructed using fascia lata and the lateral one‐third of the patellar ligament. The opposite CCL served as the control. Animals were sacrificed at 0, 4, 12 and 26 weeks postoperation and axial failure tests were performed. Stiffness, maximum load, and elastic modulus of the replacement increased over time, while elongation to maximum load continually decreased as compared to controls. Other parameters showed less consistent trends.

The results are encouraging given the reduction in joint laxity and the increases in tissue stiffness and strength. However, the ligament substitute was still unable to replicate the mechanical properties of the normal cruciate ligament. Longer studies therefore are required to determine if this replacement is capable of completely restoring joint stability and normal function.

A prospective study was undertaken to compare the analgesic effect of intra‐articular bupivacaine, morphine, or saline in the 24‐hour period following cranial cruciate ligament repair in dogs. Thirty‐six clinical patients with ruptured cranial cruciate ligaments were randomly assigned to one of three groups. After surgical stabilization, and before skin closure, an intra‐articular injection was given; group one (n = 12) received 0.5% bupivacaine HCl at 0.5 mL/kg, group two (n = 12) received morphine at 0.1 mg/kg diluted with saline to a volume of 0.5 mL/kg, and group three (n = 12) received saline at 0.5 mL/kg. Heart rate, respiratory rate, mean arterial blood pressure, cumulative pain score, visual analog pain score, and pain threshold test on both stifles were recorded preoperatively and at 0 to 6 and 24 hours postoperatively. Surgeons and pain scoring investigators were unaware of the intra‐articular medication given. Supplemental analgesia, if needed, was provided in the postoperative period according to subjective assessment of patient discomfort. Postoperative pain scores were lowest in the bupivacaine group and highest in the saline group. Pain threshold, measured by applying calibrated loads to the knee, was higher postoperatively in the bupivacaine group than in the saline group. Dogs in the morphine and bupivacaine groups required less supplemental analgesia than dogs in the saline group. The local provision of analgesia reduces the need for systemic drugs with potential side effects. Both intra‐articular morphine and intra‐articular bupivacaine provided better postoperative analgesia than intra‐articular saline, with intra‐articular bupivacaine showing the greatest effect.

The clinical effects of sevoflurane, isoflurane, and halothane anesthesia with or without nitrous oxide, were compared in healthy, premedicated cats breathing spontaneously during 90 minutes of anesthesia. The effect of nitrous oxide in accelerating the induction of and recovery from anesthesia was more evident for halothane than for sevoflurane or isoflurane. The cats recovered more rapidly from sevoflurane‐oxygen than from either halothane‐ or isoflurane‐oxygen. Heart rates did not significantly change during anesthesia with any of the anesthetics. Arterial blood pressures during sevoflurane‐oxygen anesthesia were somewhat higher than those with either isoflurane‐ or halothane‐oxygen. There were no significant differences in arterial blood pressures among sevoflurane, isoflurane, and halothane anesthesia when combined with nitrous oxide. The respiration rate during sevoflurane‐oxygen was similar to that during halothane‐oxygen. There were no significant differences in respiration rate among sevoflurane, isoflurane, and halothane anesthesia when combined with nitrous oxide. The degree of hypercapnia and acidosis during sevoflurane anesthesia was similar to that observed during isoflurane anesthesia and less than during halothane anesthesia. The three anesthetic regimens, with or without nitrous oxide, induced a similar degree of hyperglycemia and hemodilution during anesthesia. Serum biochemical examination did not reveal any hepatic or renal injuries after each anesthesia.

Dobutamine was infused (1.7 μg/kg/minute) into 200 anesthetized horses as treatment for hypotension. The horses had been premedicated with xylazine, and anesthesia was induced with guaifenesin and ketamine and maintained with halothane. One hundred fifty‐seven horses (79%) responded with an average increase in systolic blood pressure of at least 10 mm Hg within 10 minutes. A cardiac arrhythmia developed in 56 horses (28%) after dobutamine administration: 34 with sinus bradycardia, 18 with atrioventricular block, 2 with premature atrial contractions, and 2 with atrioventricular dissociation. Dobutamine intravenous infusion was effective treatment for hypotension in horses anesthetized with halothane.

Chlorhexidine diacetate and povidone‐iodine were evaluated for fibroblast toxicity on a primary line of canine embryonic fibroblasts, and for bactericidal efficacy against Staphylococcus aureus. The cultured fibroblasts or S. aureus were exposed for 30 minutes to incremental dilutions of 0.5 to 0.0005% chlorhexidine diacetate, 5.0 to 0.05% povidone‐iodine, or physiologic buffered saline as a control. To determine survival, fibroblasts were trypsinized and counted; S. aureus colonies were counted on brain‐heart infusion agar. Survival for both groups was expressed by calculating the number of living cells in test dilutions as a percentage of the number in control cultures. Fibroblast survival occurred at chlorhexidine concentrations less than 0.013% and at povidone‐iodine concentrations less than 0.5% (p < 0.05). Significant S. aureus survival (p < 0.05) was noted at chlorhexidine concentrations less than 0.05% and povidone‐iodine concentrations less than 1.0%. These data showed that all bactericidal concentrations of chlorhexidine diacetate and povidone‐iodine were lethal to canine embryonic fibroblasts in vitro, whereas non‐lethal concentrations allowed significant bacterial survival.