CVMA | Table of Contents and Abstracts

Table of Contents and AbstractsApril 2020, Vol. 84, No. 2


Changes in CO-oximetry values and pulse oximetry in isoflurane-anesthetized dogs with and without nitrous oxide

Teela Jones, Cindy Feng, Tanya Duke-Novakovski (page 83)

Concentrations of 64% to 70% nitrous oxide (N2O) provide intra-operative analgesia. Clinically, pulse oximeter estimation (SpO2) of oxygen (O2) hemoglobin saturation (SaO2) was observed to decrease with N2O. Absorption atelectasis from breathing O2 was thought to decrease arterial partial pressure of O2 (PaO2) below 70 mmHg and reduce SaO2 and SpO2 when N2O was used. Administering N2O from the beginning of the anesthesia might prevent atelectasis development and low PaO2.

The study was done in 2 parts (P < 0.05). In Part 1, isoflurane-anesthetized dogs undergoing ovariohysterectomy (n = 15 each group) breathed N2O from anesthesia start (N2Oearly) or 1 hour later (N2Olate). SpO2, CO-oximetry values, and PaO2 were compared to dogs breathing O2 throughout anesthesia (control). Timing of N2O introduction did not affect PaO2 (lowest = 94 mmHg), SaO2, or SpO2. With N2O, the lowest SpO2 value was 91% and corresponded to a PaO2 of 151 mmHg. Carboxyhemoglobin increased (highest = 2.7%) and SaO2 decreased with N2O (lowest = 96.7%).

In Part 2, to replicate findings, 10 isoflurane-anesthetized dogs breathed N2O, then O2. With N2O, SaO2 did not decrease, but carboxyhemoglobin increased and returned to baseline once N2O was discontinued. The dog with the highest carboxyhemoglobin (2%) had an SaO2 of 96.8% (PaO2 = 93 mmHg). Carboxyhemoglobin and SaO2 changes were not clinically significant. Pulse oximetry did not reliably estimate SaO2 but N2O was not always a factor.

The effect of inspired oxygen concentration on oxidative stress biomarkers in dogs under inhalation anesthesia

Patarakit Chongphaibulpatana, Yuu Kumagai, Daisuke Fukui, Masaaki Katayama, Yuji Uzuka (page 91)

This study investigated oxidative stress biomarkers at 3 different oxygen concentrations in dogs under general anesthesia to determine whether high-concentration oxygen increases oxidative stress. Six healthy beagles were randomly assigned to receive 3 anesthesia protocols (inhalation of 40%, 60%, and 100% oxygen) during 3 hours of general anesthesia with sevoflurane, with at least one week in between each protocol. For each experiment, blood samples were collected at 0, 3, 6, and 24 hours after inhalation of oxygen. Derivatives of reactive oxygen metabolites, biochemical antioxidant potential, superoxide dismutase, and 8-hydroxydeoxyguanosine in the blood did not significantly differ among the 3 groups at any time point. This study is the first comparing high concentrations of oxygen with low concentrations of oxygen for anesthesia in dogs. According to our findings, 100% oxygen may not alter the oxidative stress level in dogs during general anesthesia with sevoflurane for 3 hours.

Respiratory and hemodynamic effects of 2 protocols of low-dose infusion of dexmedetomidine in dogs under isoflurane anesthesia

Caterina Di Bella, Despoina Skouropoulou, Marzia Stabile, Cosmin Muresan, Salvatore Grasso, Luca Lacitignola, Luisa Valentini, Antonio Crovace, Francesco Staffieri (page 96)

The aim of this study was to evaluate the respiratory and hemodynamic effects of a low-dose dexmedetomidine infusion [1 µg/kg body weight (BW) per hour], with or without a loading dose (1 µg/kg BW), in dogs under isoflurane anesthesia. Thirty dogs were premedicated with methadone [0.3 mg/kg BW intramuscular (IM)], induced with propofol intravenous (IV) and maintained with isoflurane (1.3% to 1.4%) under mechanical ventilation. Animals were randomly assigned to 3 intravenous (IV) treatments (n = 10): 1 µg/kg BW dexmedetomidine, followed by 1 µg/kg BW per hour (group BI); or saline solution bolus, followed by either an infusion of 1 µg/kg BW per hour dexmedetomidine (group I) or saline solution (group C). The infusions were interrupted after 30 minutes. Respiratory system static compliance (Cstat) and respiratory system resistance (Rrs), partial pressure of oxygen/fractional inspired oxygen ratio (PaO2/FIO2), intrapulmonary shunt (Fshunt), and cardiac output (CO) were determined 5 minutes before the bolus (BASELINE), at the end of the bolus (BOLUS), and at 15 (T15), 30 (T30), and 45 minutes (T45) intervals. In group BI, Cstat and PaO2/FiO2 were higher at T15 and T30 than at BASELINE in the same group and than group C at the same times. In group I, the same parameters at T30 were higher than at BASELINE and than group C at the same time. In group BI, Rrs and Fshunt were lower than at BASELINE and than group C at the same time. In group I, the same parameters at T30 were lower than at BASELINE and those of group C at the same time. Cardiac output (CO) at T30 was higher in groups BI and I than in group C. The results of this study showed that low-dose dexmedetomidine infusion improves oxygenation and respiratory system mechanics and has a stabilizing hemodynamic effect in dogs anesthetized with isoflurane and mechanically ventilated.

Cardiovascular and respiratory effects of carbon dioxide pneumoperitoneum in the domestic rabbit (Oryctolagus cuniculus)

Claudia Kabakchiev, Alexander Valverde, Ameet Singh, Hugues Beaufrère (page 108)

The objective of this study was to evaluate the effect of intra-abdominal pressure (IAP) on cardiorespiratory parameters during pneumoperitoneum with carbon dioxide in domestic rabbits. Six juvenile female New Zealand white rabbits were assigned to randomized sequences of IAP (0, 4, 8 mmHg) in a crossover study. The following parameters were measured at each IAP: direct arterial blood pressure (ABP); cardiac output, (CO), cardiac index, and stroke volume index (CI, SVI); heart rate; end-tidal carbon dioxide (ETCO2); arterial blood gases (PaCO2, PaO2); peak inspiratory pressure (PIP); and peripheral oxygen saturation (SpO2). Between IAPs, the abdomen was desufflated for a 5-minute washout period. Mixed linear regression models were used for statistical analysis. Heart rate, SpO2, and ABP were not significantly affected by IAP, although there was a positive increase in ABP with IAP. Partial pressure of carbon dioxide (PaCO2) was increased at an IAP of 8 mmHg and ETCO2 and PIP were greater with each IAP applied. Cardiac output and CI were significantly decreased with IAP and, although SVI showed the same trend, it was not statistically significant. In conclusion, pneumoperitoneum with carbon dioxide causes an increase in ETCO2, PaCO2, and PIP, whereas cardiac output and CI decrease. These cardiorespiratory changes should be considered when determining the optimal IAP for laparoscopic procedures in rabbits.

In-vitro effects of taurolidine alone and in combination with mitoxantrone and/or piroxicam on canine transitional cell carcinoma

Brittney Byer, Lisa J. Schlein, Barbara Rose, Bernard Séguin (page 115)

The objective of this in-vitro study was to evaluate taurolidine as a therapy for transitional cell carcinomas in canine patients. Transitional cell carcinoma (TCC) is the most common cancer of the urinary bladder in dogs and accounts for approximately 2% of reported malignancies in this species. There is no cure for this neoplasm and most dogs are lost from complications associated with progression of the local disease. Taurolidine has been shown to have anti-tumor and antiangiogenic effects against a variety of neoplasms in human and animal models. Four canine TCC cell lines were treated with various concentrations of taurolidine, mitoxantrone, and piroxicam alone. In addition, combinations of taurolidine/mitoxantrone, taurolidine/piroxicam, mitoxantrone/piroxicam, and taurolidine/mitoxantrone/piroxicam were assessed. Susceptibility of the TCC cell lines was based on a 72-hour growth inhibition assay using resazurin with absorbance measured at λ530/590. The ability of taurolidine to induce apoptosis was evaluated on 2 of the cell lines with an Annexin-V/propidium iodide assay. All cell lines were susceptible to treatment with taurolidine, mitoxantrone, and piroxicam alone. The results of the combination therapies of the 3 drugs were dependent on cell line and concentration and revealed no change in cell growth inhibition, a subadditive relationship, or a synergistic relationship. Taurolidine induced apoptosis in a concentration- and time-dependent fashion. Taurolidine alone showed significant effects on cell viability in vitro in canine TCC cell lines and these effects can be potentially enhanced with the addition of mitoxantrone and/or piroxicam.

Assessment of diastolic function using mitral flow propagation velocity in cats

Keisuke Sugimoto, Nana Kawase, Takuma Aoki (page 124)

The objectives of this study were to investigate the usefulness of mitral flow propagation velocity (Vp) in cats by evaluating the effect of the flow pattern summation and evaluation of Vp variables in cats with hypertrophic cardiomyopathy (HCM). Healthy cats were categorized into summation (Sum) and separation (Sepa) groups to evaluate the effects of the flow pattern summation on Vp. Cats with HCM were categorized into HCM left atrial (LA) (−), LA (+), and LA (++) groups according to the degree of LA enlargement to investigate the feasibility of Vp. There were no significant differences noted in Vp between the Sum and Sepa groups and no significant correlation between Vp and heart rate. Decline of Vp was associated with the degree of LA enlargement. Mitral flow propagation velocity appeared to be clinically feasible in cats and could possibly be useful in the detection of diastolic dysfunctions in cats with HCM.

Effects of laser power, wavelength, coat length, and coat color on tissue penetration using photobiomodulation in healthy dogs

Lindsay H. Elam, R. Eric Heidel, Justin W. Shmalberg (page 131)

Photobiomodulation is an accepted regenerative medicine treatment modality used to stimulate tissue repair, mediate inflammation, and improve mobility in humans and animals. The objective of this study was to assess the influence of laser power and wavelength, coat length and color, and shaving on in-vivo photon delivery by therapeutic laser in dogs. Forty-seven dogs of various breeds and coat colors (17 black, 15 brown, and 15 white) and with varying coat lengths were assessed with 2 commercially available veterinary lasers. Photons were delivered to the lateral aspect of the inguinal fold and calcaneal tendon, with direct penetration through the dermis, as well as dermis and tendon, as measured with a thermopile laser sensor. Significant impacts on laser transmission were noted for laser power (P = 0.001), wavelength (P < 0.002), coat color (P < 0.001), and shaved coat (P < 0.001). Percent transmission was higher for a class IV 810/980 nm wavelength laser at 0.5 W than for a class IIIb 904 nm laser (P < 0.001). There was a significant difference between transmission of photons among white, brown, and black coats, with less transmission noted with increasing coat pigment (P < 0.001). Transmission was greater at higher power levels (3 W, 5 W) Results showed significant differences in laser transmission for all variables assessed, with the exception of coat length, which was not a significant predictor of laser transmission. As transmission was significantly reduced in darker and unshaved areas, higher power lasers may be necessary for darker pigmented dogs and shaving of hair is recommended before laser therapy.

Bile composition of healthy cats and cats with suspected hepatobiliary disease using point-of-care analyzers: A prospective preliminary study

Romain Huvé, Elizabeth O’Toole, Carolyn Gara-Boivin, Pascal Fontaine, Marie-Claude Bélanger (page 138)

Although hepatobiliary disease is common in cats, little is known about the bile composition in either these diseased states or in healthy cats. The objectives of this study were to evaluate several analytes from the bile of healthy cats and to investigate the usefulness of measuring these variables to predict bacterial cholangitis. Cats were prospectively enrolled and divided into 3 groups: 21 healthy cats (group 1) and 14 cats with suspected hepatobiliary disease: 9 without bacterial biliary infection (group 2) and 5 with bacterial biliary infection (group 3). Percutaneous ultrasound-guided cholecystocentesis was conducted on each cat. Bile cytology and culture were carried out and bile was analyzed for pH, lactate, and glucose levels using several point-of-care (POC) devices. Reference values for several bile analytes in healthy cats were calculated and are presented in this study. Neither the pH (P = 0.88) nor the lactate concentration (P = 0.85) was significantly different among the 3 groups. Sodium concentration was significantly higher in group 3 than in group 2 (P < 0.05). Bile pH, lactate, and glucose levels were unable to predict the presence of a bacterial infection in the bile.

L-lactate in cerebrospinal fluid can be used as a biomarker of encephalitis in cattle

Juliana M. Curti, Gustavo R. Queiroz, Priscilla F.V. Pereira, Mayara C. Anjos, Karina K.M.C. Flaiban, Júlio A.N. Lisbôa (page 146)

Cerebrospinal fluid (CSF) changes are significant for antemortem diagnoses of some neurological diseases. The aim of this study was to evaluate if the concentration of L-lactate in CSF could be used to differentiate healthy from encephalitic cattle. Cerebrospinal fluid samples from healthy cattle (n = 10) and from those naturally affected by rabies (n = 15), bovine herpesvirus type 5 meningoencephalitis (n = 16), histophilosis (n = 6), or bacterial encephalitis (n = 4), including 1 case of listeriosis, were collected and analyzed. Physical, biochemical (i.e., protein and glucose), and cellular analyses were performed in fresh samples. L-lactate, electrolytes (sodium, potassium, and chloride), calcium, and magnesium concentrations were measured in CSF samples that were kept frozen. L-lactate concentrations were also measured in plasma. Analysis of variance was used for comparison between groups and receiver operating characteristic analysis was performed considering L-lactate in CSF of healthy versus encephalitic cattle. The CSF L-lactate concentration was significantly higher in cattle with bacterial encephalitis than in healthy cattle; however, it did not differ between viral and bacterial encephalitis. The calcium concentrations were lower in cattle with encephalitis. L-lactate concentration in CSF > 3.6 mmol/L can be accepted as a cut-off value to indicate encephalitis. Thus, L-lactate in CSF is important for the diagnosis of encephalitis in cattle. Despite the small number of cases of bacterial encephalitis, it is suggested that L-lactate was not important for the differentiation between viral and bacterial encephalitis. Additional studies with a greater number of observations are necessary to clarify this, specifically in cases of listeriosis.

Duration of immunity after rabies vaccination in dogs: The Rabies Challenge Fund research study

W. Jean Dodds, Laurie J. Larson, Kris L. Christine, Ronald D. Schultz (page 153)

A prospective study of 65 research beagles kept in a rabies-free environment was undertaken to determine the duration of immunity after they received licensed rabies vaccines. The eventual goal was to extend mandated rabies booster intervals to 5 or 7 years and help reduce the risk of vaccine-associated adverse events. Three groups of dogs were vaccinated with 1 of 2 commercial rabies vaccines or saline at 12 and 15 weeks of age. Beginning 5 years 5 months later, vaccinated and unvaccinated dogs were challenged with virulent rabies virus and observed for 90 days over a series of 3 trials. Humoral and cellular immune responses were examined by serology and flow cytometry. Brain tissue from all challenged dogs was tested for rabies virus. Challenge trial 1 was confounded due to insufficiently virulent virus. In trials 2 and 3 virulent challenge provided 100% mortality in controls. Vaccinate survival was 80% (4/5) after 6 years 7 months, 50% (6/12) after 7 years 1 month, and 20% (1/5) after 8years 0 months. Antibody responses 12 days post-challenge correlated strongly with survival. In a separate non-challenge trial, administration of either a recombinant or a killed rabies vaccine demonstrated memory antibody responses 6 years 1 month after initial vaccination compared with unvaccinated controls. Our data demonstrated that i) duration of immunity to rabies in vaccinated dogs extends beyond 3 years; ii) immunologic memory exists even in vaccinated dogs with serum antibody titer < 0.1 IU/mL; and iii) non-adjuvanted recombinant rabies vaccine induces excellent antibody responses in previously vaccinated dogs 14 days after administration.

Brief Communications

Pilot study investigating the feasibility of mitral valve repair without aortic cross-clamping and cardioplegia

Wanda J. Gordon-Evans, John P. Carney, Mathew T. Lahti, Richard W. Bianco (page 159)

There is evidence that perfusing the heart with a heart and lung machine is less injurious than cross-clamping the aorta and administering cardioplegia during cardiac surgery. Although mitral valve replacement has been carried out without aortic cross-clamping and cardioplegia, it has been stated that cross-clamping is necessary in order to maintain visualization and a motionless surgical field for mitral valve repair. The purpose of this study was to determine the surgical feasibility of mitral valve repair without cross-clamping the aorta and using cardioplegia. Our hypothesis was that a completely bloodless and motion-free field would not be necessary to carry out mitral valve repair with annuloplasty and synthetic chordae tendineae sutures. Papillary muscles, chordae tendineae, annulus, and mitral valve leaflets were all readily visualized. Chordae tendineae sutures were used and annuloplasty was conducted without visual obstruction or motion interference. Our results show that mitral valve repair is feasible without cross-clamping the aorta and using cardioplegia.