Veterinary Surgery

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.

Large mongrel dogs were anesthetized, instrumented, and subjected to electrically induced ventricular fibrillation after breathing either 100% oxygen (O₂) or 10% O₂ and 90% nitrogen for 10 minutes before arrest. Four minutes after arrest, open chest cardiopulmonary resuscitation (CPR) or intermittent abdominal compression closed chest CPR was initiated and continued for 20 minutes, at which time defibrillation was attempted. Central arterial and mixed venous blood samples were collected serially for the measurement of pH, carbon dioxide partial pressure (PCO₂), and O₂ partial pressure (PO₂), and calculation of bicarbonate concentration and base excess. Mixed venous blood was collected serially for the measurement of lactate concentration. Hemodynamically variable resuscitation techniques and pre‐arrest hypoxia or hy‐peroxia did not significantly influence blood‐gas values during CPR. Mixed venous lactate concentrations after 20 minutes of CPR were significantly higher when hypoxia preceded the arrest and when intermittent abdominal compression closed chest CPR was used for resuscitation. Mixed venous PCO₂ was significantly higher than arterial PCO₂ in all dogs during CPR but was not significantly different before arrest.

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.

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.

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.

Bite wounds of the chest wall in small dogs can extend into the thorax and can be associated with severe damage to chest wall muscles, ribs, and lungs. Two major problems associated with the management of these wounds are lack of sufficient muscle tissue for chest wall reconstruction, and difficulty draining the extensive dead space created in the chest wall. We describe a simple method to overcome these problems. The bite wound areas were surgically explored and all devitalized soft tissue was debrided. The pleural cavity was explored, intrathoracic injuries repaired, and a thoracic drainage tube was placed. Ribs in the injured area were stabilized in anatomic position by means of heavy gauge sutures passed around pairs of adjacent ribs, thus creating a scaffolding for soft tissues. Viable muscle and subcutaneous tissues were apposed as much as possible and the skin closed over the defect. Eleven small dogs were treated using this technique. All dogs had severe injuries to the thoracic wall muscles and eight dogs had multiple rib fractures. There was no evidence of chest wall instability in any of the dogs after surgery. Nine dogs survived the injury and were reevaluated 3 to 32 months after surgery. All were clinically normal. One dog developed wound infection and pyothorax, caused by insufficient debridement of injured muscle tissue, and died 10 days after surgery. A second dog died 24 hours postoperatively of undetermined causes.

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.

Objective—The purpose of this study was to determine the effects of phosphate‐buffered saline (PBS), sterile tap water, normal saline, and Ringer's lactate on wound healing in an in vitro model.

Study Design—The effects of PBS, sterile tap water, normal saline, and Ringer's lactate on a primary line of canine embryonic fibroblasts were determined.

Animals or Sample Population—A primary line of canine embryonic fibroblasts.

Methods—The effects of the various lavage solutions were determined by (1) vital staining of the treated cells with a 0.5% trypan blue solution, (2) evaluation of the amount of lactate dehydrogenase released by the treated cells, and (3) cytopathologic evaluation of hematoxylin and eosin‐stained monolayers of treated canine fibroblasts. The cells were exposed to the lavage treatments for the following time intervals: 0.5 minute, 1 minute, 2.5 minutes, 5 minutes, and 10 minutes. PBS was used as the control.

Results—Sterile tap water significantly damaged canine fibroblasts at all time intervals (P= .05). This was attributed to the alkaline pH, hypotonicity, and presence of numerous cytotoxic trace elements in the tap water used. Cytotoxic effects were noted in fibroblasts after 10 minutes' exposure to normal saline; this may be because of the acidic pH of normal saline and lack of a buffering system. Ringer's lactate did not induce any significant fibroblast injury.

Conclusions—PBS and Ringer's lactate do not induce any significant fibroblast injury, whereas normal saline and sterile tap water cause mild and severe cytotoxic effects in vitro.

Clinical Relevance—Further clinical investigation is indicated to establish whether Ringer's lactate is the wound lavage solution of choice compared with normal saline. Sterile tap water may cause considerable fibroblast injury.