Arterial oxygen and carbon dioxide tensions in conscious laterally recumbent ponies

Six adult ponies were trained calmly to assume and maintain left lateral recumbency without the use of sedative or immobilising agents. During a 30 min recumbent period, pHa, arterial oxygen and carbon dioxide tensions (PaO2 and PaCO2) and heart and respiratory rates were monitored at regular intervals to evaluate ventilatory response. Overall, there were no statistically significant differences found between mean control and recumbent or final standing values. When lightweight ponies were compared to heavyweight ponies, only mean PaO2 at 10 mins recumbency was different. This information supports the hypothesis that ventilation impairment during the first 30 mins of equine general anesthesia is primarily drug-mediated, rather than initiated by recumbency per se.     

Intraocular oxygen tensions in normal and diseased eyes of farmed halibut

We have previously documented ocular abnormalities in farmed halibut and reported that the production of gas-filled posterior segment cysts appears to be central in the pathogenesis of many, if not all of the signs in these eyes. In a number of fish, gas bubbles may be seen in the anterior chamber of the eye, especially after trauma or strenuous exertion associated with handling. A knowledge of the composition of this gas is important in understanding fully the mechanism of gas and cyst production. Here we report investigations into the composition of gas in the globes of normal fish, fish in which intraocular cysts have been documented previously by ultrasonography and fish where post-mortem examination demonstrated both gas- and fluid-filled choroidal cysts. High levels of oxygen were demonstrated in samples of aqueous from all fish but fish with affected eyes had a statistically significantly higher partial pressure of oxygen than did fish with normal eyes.     

Body position and mode of ventilation influences arterial pH, oxygen, and carbon dioxide tensions in halothane-anesthetized horses.

Effects of body position and type of ventilation were determined on arterial blood gases (PaO2, PaCO2) and pH during and immediately following clinical halothane anesthesia in 36 young, physically conditioned horses. Horses in dorsal recumbency had a lower PaO2 than did similarly breathing horses in a lateral position. Predictably controlled positive-pressure ventilation inproved arterial oxygenation and permitted maintenance of a normal PaCO2. Most horses, regardless of type of ventilation and operative body positioning, were hypoxemic in the immediate postanesthetic period.     

Static respiratory compliance in normal dogs

Static respiratory compliance was measured in a series of normal dogs. The values (mean SEM) for total compliance (n = 42), pulmonary compliance (n = 42) and chest wall compliance (n = 93) were 61 (3–8), 82 (4–7) and 94 (3-3) ml/ cmH₂0, respectively. There was a strong positive correlation between bodyweight and chest wall circumference and all divisions of compliance (r 0–55) and a slight negative correlation (r = -0–39) between age and chest wall compliance. There was a significant difference between compliance values for narrow chested dogs and broad chested dogs (P < 0–01). Of the four most frequently encountered breeds in this study (border collie, German shepherd, labrador retriever and rottweiler) the German shepherd dog had the strongest correlation between bodysize and compliance while the rottweiler, in general, showed a negative correlation. When corrected for body-weight the border collie had the highest compliance values and the rottweiler had the lowest. It was concluded from this study that compliance values for specific breeds cannot be extrapolated from the general population data and must be determined on an individual breed basis.     

Urine-blood carbon dioxide tension gradient in healthy dogs

The urine-blood carbon dioxide tension (PCO2) gradient was measured in 10 healthy mature Beagles after alkalinization of the urine by administration of sodium bicarbonate. The mean (+/- SD) urine-blood PCO2 gradient was 65.92 +/- 14.42 mm of Hg, with range of 38.2 to 82.2 mm of Hg. Mean urine PCO2 was 110.21 +/- 14.19 mm of Hg, with range of 84.1 to 127.3 mm of Hg. Because urine-blood PCO 2 gradient less than 30.0 mm of Hg or urine PCO2 less than 55 mm of Hg in people is diagnostic for a defect in distal nephron acidification, similar values might be applicable to diseases in dogs.     

Effects of dietary protein/phosphate restriction in normal dogs and dogs with chronic renal failure

The effects of three dietary protein intakes (1–9, 1–3, and 0–6 g protein/kg bodyweight/day) on selected aspects of protein, mineral and electrolyte balance as well as renal functions was studied in normal dogs with moderate chronic renal failure. Dietary phosphate levels varied according to the quantity of phosphate in protein sources. Within the ranges of protein intake examined in this study, protein intake did not have a significant effect on glomerular filtration rates as measured by inulin clearance or 24-hour creatinine clearance. Restricting protein intake to less than 1–9 g protein/kg bodyweight/day further reduced retention of nitrogenous waste products as measured by serum urea nitrogen concentrations, but at the expense of adequate protein nutrition. Diets providing less than 1–9 g protein/kg bodyweight/day promoted protein malnutrition characterised by hypoproteinaemia and hypoalbuminaemia in both normal dogs and dogs with renal failure. Serum protein concentrations were similar in normal and renal failure dogs, suggesting that, under the conditions of this study, normal and renal failure dogs may have similar protein requirements. Progressive dietary protein/phosphate restriction improved but did not normalise phosphate balance in renal failure dogs.     

Results of ancillary tests for respiratory disease in normal dogs

Twenty-five mixed-breed clinically normal mature dogs were evaluated for respiratory disease by thoracic radiographs, complete blood counts, modified Knott's test, fluorescent antibody test for heartworms, bronchoscopy, tracheal washing, and bronchial brushing. Gross necropsies, cultures of lung parenchyma, and microscopic studies of lung at the site of and adjacent to the tracheal washing and bronchial brushing techniques were performed. The high prevalence of abnormal findings reflected subclinical disease in a confined population. The importance of a combination of complementary diagnostic tests was reinforced by the lack of specificity of individual tests.     

Haematological characteristics predicting susceptibility for ascites. 1. High carbon dioxide tensions in juvenile chickens

1. Male broilers of two different genetic stocks, a pure broiler sire line (A) and commercially available Ross broilers (B), were used to study the effect of haematological characteristics in juvenile chickens on the development of clinical ascitic signs. Production performance (body weight gain (BWG), feed intake (FI), feed conversion ratio (FCR)) from 448 birds per stock was measured from 2 to 5 weeks of age. Mortality was recorded from 2 to 6 weeks of age. The birds were housed at a low ambient temperature to stimulate the incidence of ascites. 2. From each stock, 32 birds with the highest (high risk: HRc) and 32 birds with the lowest (low risk: LRc) carbon dioxide tensions (pCO2) in venous blood were selected at 11 d of age. These birds were marked for future blood sampling to determine changes in pCO2 with age to relate these values to ascites susceptibility. 3. At 2 weeks of age all birds (including HRc and LRc birds) were allotted to 32 floor pens (one HRc and one LRc in each pen) per stock. Venous blood samples were collected weekly from HRc and LRc birds for blood gas analysis and haematocrit, and at week 5 also for thyroid hormone (T3, T4) concentrations in plasma. At 5 weeks of age all HRc and LRc birds were examined post-mortem, relative heart, lung, and liver weights and arterial pressure index (API) values were recorded. 4. Birds from stock A showed a lower BWG and FCR and notably higher ascites mortality compared with stock B. An effect of pCO2 tensions at d 11 was found on the incidence of ascitic signs in selected birds of both stocks up to week 5. From the HRc groups 30% of the birds showed ascitic signs, whereas this was only 8% in the LRc group. LRc birds of stock B in particular showed constant low API values (20 +/- 3%) and none of these birds showed signs of ascites. 5. Our results suggest that the ascites problem in Ross birds can be eliminated by selection for low pCO2 tensions in venous blood. Stock effects on API, liver weight, lung weight, and plasma thyroid hormone independent of pCO2 showed a more complex picture of the ascitic signs in stock A compared with B. 6. We concluded that in this experiment a high pCO2 tension in venous blood measured at d 11 was a reliable predictor for ascites susceptibility observed at 5 weeks of age. A low pCO2 tension provides an appropriate criterion for genetic selection, whereas a high pCO2 tension emphasises the necessity for intensive management in poultry houses.     

Serum concentrations of 1,25-dihydroxycholecalciferol and 25-hydroxycholecalciferol in clinically normal dogs and dogs with acute and chronic renal failure

OBJECTIVE: To compare serum concentrations of 1,25-dihydroxycholecalciferol (1,25-[OH]2D3) and 25-hydroxycholecalciferol (25-[OH]D3) in healthy control dogs and dogs with naturally occurring acute renal failure (ARF) and chronic renal failure (CRF). ANIMALS: 24 control dogs, 10 dogs with ARF, and 40 dogs with CRF. PROCEDURE: Serum concentrations of 1,25-(OH)2D3 were measured by use of a quantitative radioimmunoassay, and serum concentrations of 25-(OH)D3 were measured by use of a protein-binding assay. RESULTS: Mean +/- SD serum concentration of 1,25-(OH)2D3 was 153 +/- 50 pmol/L in control dogs, 75 +/- 25 pmol/L in dogs with ARF, and 93 +/- 67 pmol/L in dogs with CRF. The concentration of 1,25-(OH)2D3 did not differ significantly between dogs with ARF and those with CRF and was in the reference range in most dogs; however, the concentration was significantly lower in dogs with ARF or CRF, compared with the concentration in control dogs. Mean +/- SD concentration of 25-(OH)D3 was 267 +/- 97 nmol/L in control dogs, 130 +/- 82 nmol/L in dogs with ARF, and 84 +/- 60 nmol/L in dogs with CRF. The concentration of 25-(OH)D3 was significantly lower in dogs with ARF or CRF, compared with the concentration in control dogs. CONCLUSIONS AND CLINICAL RELEVANCE: The concentration of 1,25-(OH)2D3 was within the reference range in most dogs with renal failure. Increased serum concentrations of parathyroid hormone indicated a relative deficiency of 1,25-(OH)2D3. A decrease in the serum concentration of 25-(OH)D3 in dogs with CRF appeared to be attributable to reduced intake and increased urinary loss.     

Efficacy of a single oral dose of isorsorbide 5-mononitrate in normal dogs and in dogs with congestive heart failure

Isosorbide 5-mononitrate (5-ISMN) was evaluated in normal dogs and dogs with congestive heart failure (CHF) in a randomized, blinded, and placebo-controlled study. Equilibrium blood pool imaging was used to detect changes in regional blood volume distribution. Six normal dogs were administered placebo, 2, 3, and 4 mg/kg 5-ISMN PO on separate days with a 1-week washout period between randomized dosings. Six dogs with CHF were administered placebo or 4 mg/kg 5-ISMN on separate days with a 1-week washout period between randomized dosings. Data were collected at baseline and at 15, 30, 45, 60, 90, 120, 150, 180, 210, and 240 minutes after dosing. Measured variables included indirect arterial blood pressure (BP), heart rate (HR), packed cell volume (PCV), scintigraphic count rates for normal dogs, and scintigraphic count rates for CHF dogs. Blood for plasma 5-ISMN concentration determination was collected at 60 minutes. Scintigraphic counts were corrected for decay and expressed as a percentage of the whole. No differences were detected in BP, HR, PCV, thoracic blood volume percentage (TBVP), or abdominal blood volume percentage (ABVP) between placebo and 5-ISMN in normal dogs at any dose. No differences were detected in TBVP or ABVP between placebo and 5-ISMN in dogs with CHF Plasma 5-ISMN concentration exceeded the minimum therapeutic concentration in all dogs and at all doses 60 minutes after drug administration. Equilibrium blood pool imaging failed to detect a shift in blood volume with oral 5-ISMN administration at any dose tested in normal dogs and dogs with CHF, despite adequate drug absorption. On the basis of the results of this study, 5-ISMN may not be beneficial in the treatment of dogs with CHF.     

Evaluation of carbon dioxide laser ablation combined with mitoxantrone and piroxicam treatment in dogs with transitional cell carcinoma

CASE DESCRIPTION: 8 dogs that underwent carbon dioxide (CO2) laser ablation of transitional cell carcinoma in the bladder trigone and proximal portion of the urethra and were also treated with mitotranxone and piroxicam. CLINICAL FINDINGS: Transitional cell carcinoma of the bladder frequently involves the trigone and urethra and can be difficult to manage surgically. Dogs underwent laser ablation of the primary tumor and were treated with mitoxantrone at a dosage of 5 mg/m2)every 3 weeks for 4 treatments. Piroxicam was given at a dosage of 0.3 mg/kg (0.14 mg/lb) once daily for the remaining life of the dog. TREATMENT AND OUTCOME: Median and mean disease-free intervals were 200 and 280 days, respectively. Median and mean survival times were 299 and 411 days, respectively. Adverse treatment effects were observed in 2 dogs; signs included mild, self-limiting inappetance and lethargy. The procedure appeared to be well tolerated; all treated dogs had rapid resolution of clinical signs of disease of the lower portion of the urinary tract. CLINICAL RELEVANCE: Although survival times achieved with CO2 laser ablation and treatment with mitoxantrone and piroxicam were similar to survival times associated with chemotherapy alone, resolution of clinical signs was better with the combined treatment.     

The oxygen uptake and carbon dioxide output of late chick embryos

Measurements of the oxygen uptake and carbon dioxide output during the last 36 hr. of incubation show that the exchange of these two gases increases progressively from the start of pulmonary respiration until hatching. The evidence indicates that prior to the penetration of the shell by the beak of the embryo (” pipping “) there is marked hypoxia and hypercapnia which are relieved when the embryo gains access to atmospheric air. At the time of hatching there is a very rapid release of carbon dioxide from the body surface and the internal surface of the allantoic membranes. There is no evidence to suggest that its release indicates either hypoxia or hypercapnia in the embryo immediately before hatching.     

Changes in pH of peritoneal fluid associated with carbon dioxide insufflation during laparoscopic surgery in dogs

OBJECTIVE: To evaluate changes in pH of peritoneal fluid associated with CO2 insufflation during laparoscopy in dogs. ANIMALS: 13 client-owned dogs and 10 purpose-bred teaching dogs. PROCEDURES: Laparotomy was performed on control dogs; peritoneal fluid pH was measured at time of incision of the abdominal cavity (time 0) and 30 minutes later. Laparoscopic insufflation with CO2 was performed and routine laparoscopic procedures conducted on the teaching dogs. Insufflation pressure was limited to 12 mm Hg. Intraperitoneal fluid pH was measured by use of pH indicator paper at 4 time points. Arterial blood gas analysis was performed at the same time points. RESULTS: Peritoneal fluid pH did not change significantly between 0 and 30 minutes in the control dogs. For dogs with CO2 insufflation, measurements obtained were a mean of 8.5, 24.5, 44.5, and 72.0 minutes after insufflation. The pH of peritoneal fluid decreased significantly between the first (7.825 +/- 0.350) and second (7.672 +/- 0.366) time point. Blood pH decreased significantly between the first (7.343 +/- 0.078), third (7.235 +/- 0.042), and fourth (7.225 +/- 0.038) time points. The PaCO2 increased significantly between the first (39.9 +/- 9.8 mm Hg) and fourth (54.6 +/- 4.4 mm Hg) time points. Base excess decreased significantly between the first and all subsequent time points. CONCLUSIONS AND CLINICAL RELEVANCE: Pneumoperitoneum attributable to CO2 insufflation caused a mild and transient decrease in peritoneal fluid pH in dogs. Changes in peritoneal fluid associated with CO2 insufflation in dogs were similar to those in other animals.     

Telomerase activity in clinically normal dogs and dogs with malignant lymphoma

OBJECTIVES: To determine whether telomerase activity was present in lymph nodes, buffy coat, and serum samples from dogs with malignant lymphoma (ML) and in liver, lymph node, buffy coat, and serum samples from clinically normal dogs SAMPLE POPULATION: Tissue specimens and blood samples were obtained from 11 clinically normal adult dogs (age range, 1 to 4 years) and 14 client-owned dogs with ML. PROCEDURE: The telomere repeat amplification protocol assay was used to quantify telomerase activity in the tissues from clinically normal dogs and dogs with ML. RESULTS: Of 11 clinically normal dogs, 8 had lymph node samples, 5 had liver samples, and 1 had buffy coat samples with detectable telomerase activity. None of the serum samples from the clinically normal dogs had detectable telomerase activity. Of 14 dogs with ML, 9 had lymph node samples, 3 had buffy coat samples, and 1 had serum samples with measurable telomerase activity. CONCLUSIONS AND CLINICAL RELEVANCE: Telomerase activity was not specific to tumor cells and overlapped with that found in cells from clinically normal dogs. Telomerase activity in neoplastic lymph nodes was not substantially different from that found in lymph nodes from clinically normal dogs. The determination of telomerase activity cannot be used as a sole diagnostic test for cancer. Therapeutic modalities directed toward the telomerase enzyme may not be feasible in dogs, because somatic tissues from clinically normal dogs possess variable amounts of telomerase activity.     

Arterial blood gas tensions in healthy aged dogs.

Twenty-four healthy dogs > 8 years old were recruited. In each instance, arterial blood gas tensions were analyzed. The alveolar-to-arterial oxygen gradient (P[A-a]O2) was calculated to assess adequacy of pulmonary gas exchange. Thoracic radiographs were evaluated to ensure lack of visible signs of pulmonary disease and that lung features were similar to those in aged dogs of previous reports. Unlike findings in aged human beings, arterial partial pressure of oxygen (PaO2) was not decreased in this group of aged dogs (mean +/- SD, 102.9 +/- 7.8 mm of Hg). Similarly, P(A-a)O2 also was not increased. The thoracic radiographic findings were consistent with those of previous reports of pulmonary changes in aged dogs. The extent of radiographic abnormalities and the PaO2 were not correlated.     

Assessment of fat absorption in normal dogs and in dogs with hyperadrenocorticalism

Fat absorption was determined quantitatively in clinically normal dogs, dogs with confirmed hyperadrenocorticalism before and after treatment with mitotane (op' DDD) and in pruritic dogs before and after administration of prednisolone. Fat absorption was significantly higher (P less than 0.001) in dogs with untreated hyperadrenocorticalism and pruritic dogs on prednisolone therapy than in normal dogs. It was normal in pruritic dogs before prednisolone therapy and approached normality in dogs with treated hyperadrenocorticalism. It is concluded that high circulating cortisol or prednisolone levels result in increased intestinal absorption of dietary fat possibly mediated by increased glucocorticoid induced activity of enterocytes or reduced hepatic clearance of triglycerides.     

Effect of body position on the arterial partial pressures of oxygen and carbon dioxide in spontaneously breathing,conscious dogs in an intensive care unit

Objective – To evaluate the effect of body position on the arterial partial pressures of oxygen and carbon dioxide (PaO₂, PaCO₂), and the efficiency of pulmonary oxygen uptake as estimated by alveolar‐arterial oxygen difference (A‐a difference). Design – Prospective, randomized, crossover study. Setting – University teaching hospital, intensive care unit. Animals – Twenty‐one spontaneously breathing, conscious, canine patients with arterial catheters placed as part of their management strategy. Interventions – Patients were placed randomly into lateral or sternal recumbency. PaO₂ and PaCO₂ were measured after 15 minutes in this position. Patients were then repositioned into the opposite position and after 15 minutes the parameters were remeasured. Measurements and Main Results – Results presented as median (interquartile range). PaO₂ was significantly higher (P=0.001) when patients were positioned in sternal, 91.2 mm Hg (86.0–96.1 mm Hg), compared with lateral recumbency, 86.4 mm Hg (73.9–90.9 mm Hg). The median change was 5.4 mm Hg (1.1–17.9 mm Hg). All 7 dogs with a PaO₂<80 mm Hg in lateral recumbency had improved arterial oxygenation in sternal recumbency, median increase 17.4 mm Hg with a range of 3.8–29.7 mm Hg. PaCO₂ levels when patients were in sternal recumbency, 30.5 mm Hg (27.3–32.7 mm Hg) were not significantly different from those in lateral recumbency, 32.2 mm Hg (28.3–36.0 mm Hg) (P=0.07). The median change was ?1.9 mm Hg (?3.6–0.77 mm Hg). A‐a differences were significantly lower (P=0.005) when patients were positioned in sternal recumbency, 21.7 mm Hg (17.3–27.7 mm Hg), compared with lateral recumbency, 24.6 mm Hg (20.4–36.3 mm Hg). The median change was ?3.1 mm Hg (?14.6–0.9 mm Hg). Conclusions – PaO₂ was significantly higher when animals were positioned in sternal recumbency compared with lateral recumbency, predominantly due to improved pulmonary oxygen uptake (decreased A‐a difference) rather than increased alveolar ventilation (decreased PaCO₂). Patients with hypoxemia (defined as PaO₂<80 mm Hg) in lateral recumbency may benefit from being placed in sternal recumbency. Sternal recumbency is recommended to improve oxygenation in hypoxemic patients.