Keith R. Branson

Comparison of ultrasonic Doppler flow monitor, oscillometric, and direct arterial blood pressure measurements in ill dogs

OBJECTIVE To compare blood pressure measurements obtained via ultrasonic Doppler flow monitor (DOP) and 2 oscillometric noninvasive blood pressure monitors (CAR and PAS) to invasive blood pressure (IBP) in hospitalized, conscious dogs with a range of blood pressures. DESIGN Prospective clinical study. SETTING University teaching hospital. ANIMALS Eleven client-owned dogs aged between 4 months and 11.5 years (median 6 y), and weighing between 5.8 and 37.5 kg (median 30.2 kg). INTERVENTIONS Blood pressure measurement. MEASUREMENTS AND MAIN RESULTS Three consecutive measurements of systolic, diastolic, and mean arterial pressure (MAP) were recorded for each of the 3 indirect devices (only systolic for DOP), along with concurrent IBP measurements. The data were categorized into 3 groups: hypotensive (direct MAP<80 mm Hg), normotensive (80 mm Hg<or=direct MAP>or=100 mm Hg), and hypertensive (direct MAP>100 mm Hg). Each indirect method was compared with the corresponding direct arterial pressure using the Bland-Altman method. Within the hypotensive group, each indirect method overestimated the corresponding IBP. Within the normotensive group all indirect systolic measurements and the PAS diastolic measurements underestimated the corresponding IBP. The remaining indirect measurements overestimated the corresponding IBP. Within the hypertensive group, DOP and CAR systolic measurements underestimated the corresponding IBP, and the remaining indirect measurements overestimated the corresponding IBP. In hypertensive dogs oscillometric systolic measurements were more accurate than MAP. In hypotensive dogs MAP measurements were more accurate than systolic measurements. All indirect measurements were most accurate in hypertensive dogs. CONCLUSIONS The noninvasive blood pressure monitors in our study did not meet the validation standards set in human medicine. However, CAR diastolic and MAP measurements within the normotensive group, CAR MAP measurements within the hypertensive group, and PAS diastolic measurements in all groups were close to these standards. All indirect measurements showed greater bias during hypotension. Precision was poorer for all indirect systolic measurements than for MAP.

The Effect of Bupivacaine and Morphine in a Coculture Model of Diarthrodial Joints

PURPOSE To perform a controlled laboratory study to evaluate the effect of bupivacaine and morphine on chondrocytes and synovium in a coculture model of diarthrodial joints. METHODS A proven coculture model that allows for the assessment of cartilage and synovium exists. The model allows for simulation of the diarthrodial joint in both health and disease by using culture media with or without the addition of interleukin-1. Effects of the presence of bupivacaine and morphine were evaluated by measuring media concentration of glycosamino glycans (GAG), nitric oxide (NO), and prostaglandin E(2) (PGE(2)), and tissue concentration of GAG, water, and collagen. Cell viability was determined through the use of confocal microscopy on days 1 and 2. RESULTS Cell viability 2 days after exposure to 0.5% bupivacaine was significantly less in the presence of bupivacaine than in the other groups, nearing a 100% decrease in viability. There was little effect of bupivacaine on cartilage water content or the tissue concentration of GAG and collagen. Morphine and bupivacaine both inhibited the expected rise in NO and PGE(2) when interleukin-1 was added to the media. CONCLUSIONS Continuous 0.5% bupivacaine exposure has a clear detrimental effect on chondrocytes in this in vitro study. Both bupivacaine and morphine appear to have anti-inflammatory effects. Continuous morphine exposure does not cause gross chondrotoxicity in vitro and presents itself as a potential alternative intra-articular analgesic. CLINICAL RELEVANCE Intra-articular bupivacaine infusion is an effective analgesic strategy and is frequently used in both office and outpatient surgical settings. This study provides evidence that the continued usage of postoperative bupivacaine continuous infusion pumps may have a detrimental effect on chondrocytes. Morphine has been shown to be an effective intra-articular analgesic, and its anti-inflammatory role seen in this study makes it a potential alternative to bupivacaine.

Feasibility and Safety of Targeted Cisplatin Delivery to a Select Lung Lobe in Dogs via the AeroProbe® Intracorporeal Nebulization Catheter

Delivery of drugs by airway can minimize systemic toxicity and maximize local drug concentrations. Most cancers metastasize to the lungs. Our purpose was to determine platinum concentrations in the lung after targeted delivery of cisplatin (CDDP) with an intracorporeal nebulizing catheter (INC), and to determine the safety of escalating doses of inhaled CDDP. In anesthetized and mechanically ventilated healthy dogs, the INC (AeroProbe) was introduced via flexible bronchoscope into the right caudal lung lobe (RCLL) and CDDP (10 mg/m2) administered. Tissue and serum platinum concentrations were compared to those after an equivalent intravenous dose of CDDP (n = 3 dogs/group). In three additional dogs, pharmacokinetics were performed after inhaled and intravenous CDDP. Increasing dosages of inhaled CDDP (10, 15, 20, and 30 mg/m2) were then administered every 2 weeks. Dogs were sacrificed for postmortem examination at week 10. One additional dog was treated with a single dose of 30 mg/m2 and sacrificed 2 weeks later. Immediately following a single inhaled dose, mean CDDP levels were 44 times greater in the RCLL than in most other tissues and 15.6 times lower in the serum compared to intravenous dosing. Pharmacokinetic comparison showed that the AUC0-24h was similar (p = 0.72), but maximum serum concentration was fivefold lower after inhalation than intravenous delivery (p = 0.02). Escalating doses of inhaled CDDP (cumulative 75 mg/m2) produced no significant clinical or hematological effects, but there was radiographic and histologic evidence of severe pneumonitis with mild to moderate fibrosis confined to the RCLL. Radiographic and histologic changes were similar in the single, high-dose dog. Targeted inhaled CDDP achieved high concentrations in the treated lobe, with lower peak serum levels than after intravenous administration. Escalating doses of inhaled CDDP produced focal pneumonitis and fibrosis in the treated lung lobe with minimal clinical and hematologic effects. Targeted inhaled chemotherapy could be a promising method of treatment for primary and secondary lung tumors.

Comparison of unilateral versus bilateral nasal catheters for oxygen administration in dogs

Objective: To determine the effect of bilateral nasal oxygen supplementation on tracheal airway and arterial blood gas parameters. Design: Original research. Setting: Research Laboratory. Animals: Eight normal dogs. Interventions: None. Measurements: Intra-tracheal oxygen concentration and arterial oxygen partial pressure at three different oxygen flow rates given through either unilateral or bilateral nasal catheters. Main results: FIO2 and PaO2 were significantly increased with higher total oxygen flow rates, but the increase was the same whether the higher flow was delivered through one nasal catheter or divided and administered though two nasal catheters. The use of bilateral nasal catheters allowed a tracheal FIO2 as high as 0.60 with minimal patient discomfort. Conclusions: The benefit of bilateral nasal catheters for oxygen supplementation is the ability to provide high total oxygen flows with decreased risk of patient discomfort. If the desired oxygen flow can be achieved with a unilateral nasal catheter, then the only benefit of bilateral catheters is increased patient comfort. The use of bilateral nasal oxygen catheters for oxygen supplementation can result in an FIO2 that is high enough to produce oxygen toxicity with prolonged administration.

Evaluation of pulse oximeter probes and probe placement in healthy dogs

Placement of two different pulse oximeter probes, a finger (f) probe and a multisite (s) probe, was evaluated in six healthy, anesthetized beagles. Concurrent arterial blood gas values were compared to determine the most consistent (repeatable) and accurate (compared to calculated hemoglobin saturations) pulse oximeter probe and probe placement sites for subsequent use in awake dogs. Hemoglobin oxygen saturation was determined from arterial blood gas analysis (SaO2) and by pulse oximetry (SpO2) at full hemoglobin saturation (mean, 99.5% SaO2) and at moderate desaturation (mean, 92.9% SaO2). Each probe was evaluated with three independent readings at seven different body sites (Achilles, ear, flank, lip, tail, toe, and tongue). Values for SpO2 obtained with the s probe demonstrated a significant correlation with SaO2 values (p = 0.014, R = 0.712) compared to the SpO2 values obtained with the f probe (p = 0.108). The best probe placement sites for the clip-on probes in this study were on the lip and tongue using the s probe; however, the ear, tail, and toe may be acceptable sites in awake dogs using a probe which maintains good contact across these vascular beds.

Fatal hemothorax following management of an esophageal foreign body.

A 10.8-year-old, spayed female toy poodle presented with an esophageal foreign body. The foreign body was removed endoscopically, and a gastrostomy tube was placed to provide nutritional support during esophageal healing. The gastrostomy tube was later removed by endoscopic retrieval of the bulb through the esophagus. Immediately afterward, the dog developed hemothorax and eventually died. It was determined that many small arterial branches were avulsed from the aorta. The involved sections of aorta histopathogically evidenced medial necrosis, which was believed to be related to a prior disruption of blood flow through the vasa vasorum.

Targeted Combined Aerosol Chemotherapy in Dogs and Radiologic Toxicity Grading

BACKGROUND We investigated whether combination chemotherapy, targeted with the AeroProbe® Intracorporeal Nebulizing Catheter (INC), could be safely administered, and developed a radiologic grading scheme to monitor subclinical effects on the lungs. METHODS In anesthetized and mechanically ventilated healthy dogs (n = 3), we introduced the INC via a flexible bronchoscope into the right caudal lung lobe and administered escalating dosages of gemcitabine (1, 2, 3, or 6 mg/kg) followed by cisplatin (10 mg/m(2)). Treatments were performed every 2 weeks for 4 treatments and dogs were monitored weekly with physical examination, biochemical tests, and thoracic radiographs. Dogs were sacrificed 2 weeks after the final treatment and tissues examined histologically. A radiologic grading scheme was developed to monitor subclinical pulmonary toxicity. RESULTS No significant side effects occurred in any dog. All dogs developed focal pneumonitis radiographically, and chronic, severe pneumonia with fibrosis histologically limited to the treated portion of the lung. Radiologic scores increased over time following increasing doses of chemotherapy. CONCLUSIONS Targeted aerosol delivery of gemcitabine and cisplatin by INC was clinically well tolerated. This minimally invasive method is promising for lung cancer treatment, especially given the lack of clinical toxicity. The proposed radiologic grading scheme provides a method to monitor subclinical local drug toxicity.

Comparison of Short-Term Postoperative Analgesia by Epidural, Femoral Nerve Block, or Combination Femoral and Sciatic Nerve Block in Dogs Undergoing Tibial Plateau Leveling Osteotomy.

OBJECTIVE To compare early postoperative analgesia in dogs undergoing unilateral tibial plateau leveling osteotomy (TPLO) that received bupivacaine via preoperative femoral nerve block (FNB), combination femoral-sciatic nerve block (F+SNB), or lumbosacral epidural (EPI). STUDY DESIGN Randomized, blinded, prospective clinical trial. ANIMALS Forty-five client-owned dogs undergoing unilateral TPLO. METHODS Dogs undergoing unilateral TPLO were enrolled and randomly allocated to 1 of 3 treatments: FNB, F+SNB, or EPI. Assessments were completed by an observer blinded to treatment at 0, 1, 2, 4, 6, and 8 hours after extubation using the Glasgow Composite Pain Score-Short Form (GCPS-SF). Dogs with a total score ≥ 6 or ≥ 3 in any category were given a rescue analgesic. Outcome measures analyzed for differences across treatments were the GCPS-SF at each time point, time to first rescue analgesic, and total number of rescue analgesic doses per dog. RESULTS The GCPS-SF score at extubation was significantly higher for FNB (median 3) compared to F+SNB (median 2). A significantly higher proportion of dogs receiving FNB (4/14) than F+SNB (0/17) required rescue analgesic at extubation. There was no significant difference in the proportion of dogs requiring rescue at extubation between FNB and EPI (2/14) or between F+SNB and EPI. There was no significant difference in the median time to first rescue between FNB (0 hours) and F+SNB (2 hours) or between F+SNB and EPI (1.5 hours). CONCLUSION In dogs undergoing unilateral TPLO, bupivacaine administered via FNB, alone or in combination with sciatic nerve block, can provide short-term postoperative analgesia not different to that with administration via lumbosacral epidural.