Lithium dilution cardiac output and oxygen delivery in conscious dogs with systemic inflammatory response syndrome

Objective: Compare cardiac index (CI) and oxygen delivery index (DO₂I) in conscious, critically ill dogs to control dogs; evaluate the association of CI and DO₂I with outcome. Design: Prospective non‐randomized clinical study. Setting: Veterinary teaching hospital. Animals: Eighteen client‐owned dogs with systemic inflammatory response syndrome (SIRS) and 8 healthy control dogs. Measurements and Main Results: CI of dogs with SIRS was measured using lithium dilution at times 0, 4, 8, 16, and 24 hours. Data collected included physical exam, arterial blood gas (ABG) and hemoximetry. CI of control dogs was measured 3 times with 1 measurement of ABG. Mean CI ± SE in SIRS patients was 3.32 ± 0.95 L/min/m²; lower than controls at 4.18 ± 0.22 L/min/m² (P<0.001). Mean DO₂I ± SE in SIRS patients was 412.91 ± 156.67 mL O₂/min/m²; lower than controls at 785.24 ± 45.99 mL O₂/min/m² (P<0.001). There was no difference in CI (P=0.49) or DO₂I (P=0.51) for dogs that survived to discharge versus those that did not. There was no difference in mean CI (P=0.97) or DO₂I (P=0.50) of survivors versus non‐survivors for 28‐day survival. Survivors had lower blood glucose (P=0.03) and serum lactate concentrations (P=0.04) than non‐survivors. Conclusions: CI and DO₂I in conscious dogs with SIRS were lower than control dogs, which differs from theories that dogs with SIRS are in a high cardiac output state. CI and DO₂I were not significantly different between survivors and non‐survivors. Similar to previous studies, lactate and glucose concentrations of survivors were lower than non‐survivors.     

Evaluation of oscillometric and Doppler ultrasonic devices for blood pressure measurements in anesthetized and conscious dogs

Two non-invasive blood pressure (NIBP) devices (oscillometry and Doppler) were compared to invasive blood pressure using a Bland–Altman analysis, in anesthetized and conscious dogs. When considering the systolic arterial pressure only during general anesthesia, both NIBP devices slightly underestimated the systolic arterial blood pressure however the precision and the limits of agreement for the Doppler were of a greater magnitude. This indicates a worse clinical performance by the Doppler. The performance of both NIBP devices deteriorated as measured in conscious animals. In general, for the oscillometric device, determination of invasive diastolic and mean arterial pressures was better than the invasive systolic arterial pressure. Overall, the oscillometric device satisfied more of the criteria set by the American College of Veterinary Internal Medicine consensus statement. Based upon these results, the oscillometric device is more reliable than the Doppler in the determination of blood pressure in healthy medium to large breed dogs.     

Evaluation of an indirect oscillometric blood pressure monitor in normotensive and hypotensive anesthetized dogs

Objective – To determine the accuracy and precision of an oscillometric noninvasive blood pressure device as a predictor of invasive direct blood pressure in healthy anesthetized hypotensive and normotensive dogs. Design – Prospective observational study. Setting – University teaching hospital. Animals – Eight crossbred adult dogs. Interventions – Anesthesia was induced with propofol and maintained with isoflurane. A catheter was placed in the dorsal pedal artery to record systolic, mean, and diastolic arterial blood pressures (aSAP, aMAP, and aDAP, respectively). The noninvasive blood pressure device cuff was placed around the contralateral front limb to record noninvasive systolic, mean, and diastolic blood pressure (nSAP, nMAP, and nDAP). Two states of blood pressure (BP) were studied: baseline state was established by keeping end‐tidal isoflurane concentration at 1.2±0.1%. The hypotensive state was achieved by maintaining the same isoflurane concentration while withdrawing approximately 40% of the animal's blood volume until aMAP was stable at approximately 40 mm Hg. At the end of the study, blood was returned to the animal and it was allowed to recover from anesthesia. Measurements and Main Results – Agreement between the direct and indirect BP measurements was determined by the Bland‐Altman method. The SAP and MAP but not DAP bias varied significantly between each BP state. Normotensive absolute biases (mean [SD]) for SAP, MAP, and DAP were ?14.7 mm Hg (15.5 mm Hg), ?16.4 mm Hg (12.1 mm Hg), and ?14.1 mm Hg (15.8 mm Hg), respectively. Absolute biases during the hypotensive state for SAP, MAP, and DAP were ?32 mm Hg (22.6 mm Hg), ?24.2 mm Hg (19.5 mm Hg), and ?16.8 mm Hg (17.2 mm Hg), respectively. Conclusion – The oscillometric device was not reliably predictive of intra‐arterial BP during hypotension associated with acute hemorrhage.     

Comparison of Doppler,oscillometric, auricular and carotid arterial blood pressure measurements in isoflurane anesthetized New Zealand white rabbits

ObjectiveTo assess agreement between carotid arterial pressure and auricular arterial, thoracic limb Doppler or thoracic limb oscillometric blood pressure measurements.Study designProspective experimental study.AnimalsSix adult New Zealand white rabbits.MethodsRabbits were anesthetized with isoflurane in oxygen at 1, 1.5 and 2 MAC on two separate occasions. Catheters in the auricular and the contralateral external carotid artery were connected to calibrated pressure transducers via non-compliant tubing. Inflatable cuffs of width equal to approximately 40% of the limb circumference were placed above the carpus on both thoracic limbs with a Doppler transducer placed distal to the cuff on one. Systolic (SAP) and mean (MAP) arterial blood pressure measurements were obtained at each dose, on each occasion. Agreement between measurement techniques was evaluated by repeated measures Bland Altman analysis with carotid pressure as the reference. Variation in bias over the measurement range was evaluated by regression analysis.ResultsCarotid MAP and SAP ranged from 20 to 65 mmHg and 37 to 103 mmHg respectively. Bias and 95% limits of agreement for auricular and oscillometric MAP were 7 (0–14) and ?5 (?21–11) mmHg, respectively, and for auricular, oscillometric and Doppler SAP were 23 (8–37), ?2 (?24–20) and 13 (?14–39) mmHg, respectively. Bias varied significantly over the measurement range (p < 0.001) for all three SAP techniques but not for MAP measurements.Conclusions and clinical relevanceLimits of agreement for all measurements were large but less so for MAP than SAP. Variation in bias with SAP should be considered when using these measurements clinically.     

Evaluation of oscillometric and Doppler ultrasonic methods of indirect blood pressure estimation in conscious dogs

To assess the accuracy and precision of indirect measurements of systemic arterial blood pressure (BP), results obtained with an oscillometric device (BPo) and a Doppler ultrasonic device (BPud) were compared with those obtained by direct radiotelemetry (BPrt) in 12 conscious beagles. The correlation between indirectly obtained and directly measured values for BP parameters ranged widely for the different indirect methods and sites of cuff placement, with R2 between 0.001 and 0.901. Both indirect methods underestimated all BP parameters, the degree of underestimation increasing at higher values for the BP. The highest correlation occurred when estimates were the average of 5 values consecutively obtained with the oscillometric device and cuff placement at the coccygeal artery (R2 = 0.854 for mean BPo, 0.886 for systolic BPo, and 0.901 for diastolic BPo; P < 0.0001 for all parameters) or with the ultrasonic Doppler device at the metatarsal arteries (R2 = 0.810 for systolic BPud; P < 0.0001). Multiple consecutively obtained values are advised, as this approach improves the reliability of indirect BP measurements. The strong correlation between directly measured values and estimates derived as the average of 5 consecutive indirectly obtained values indicates that the latter approach provides a useful estimate of BP in conscious dogs and is likely to be useful in monitoring disease progress and treatment in dogs with abnormal BP.     

Comparison of direct and Doppler arterial blood pressure measurements in rabbits during isoflurane anaesthesia

ObjectiveTo measure the level of agreement between Doppler measured (DOP) arterial blood pressure (ABP) in the forelimb and directly measured (DIR) auricular systolic ABP (SAP) and mean ABP (MAP) in isoflurane-anaesthetized rabbits.Study designProspective clinical study.AnimalsData were analysed from 17 of 24 healthy rabbits, weighing 1.3–2.8 kg.MethodsRabbits were anaesthetized for neutering using a standardized protocol. A 26G catheter placed in an auricular artery was connected via heparinised saline filled non-compliant tubing (regularly flushed) to a calibrated pressure transducer (zeroed level with the thoracic inlet) to obtain DIR ABP. A cuff was placed proximal to the carpus (approximately level with the thoracic inlet) and a Doppler transducer sited over the dorsal carpal branch of the radial artery to obtain DOP ABP. Simultaneous DIR and DOP ABP recordings were made every 5–10 minutes during anaesthesia. Agreement was assessed as described by Bland JM &; Altman (2007).ResultsMean ± SD cuff width: limb circumference ratio was 0.50 ± 0.04. Mean between-method differences ± SD, DIR SAP- DOP and DIR MAP- DOP, were +1 ± 8 and ?13 ± 8 mmHg respectively. The 95% limits of agreement between DIR SAP and DOP and between DIR MAP and DOP were ?14 to +17 and ?28 to +2 mmHg respectively. Differences between DIR SAP and DOP were ≤10 mmHg 85% of the time. Defining hypotension as either DIR SAP < 80 mmHg or DIR MAP < 60 mmHg, and taking DOP ABP of <80 mmHg to indicate hypotension, sensitivity and specificity were 92% and 67% respectively.ConclusionsGood agreement was found between DIR SAP and DOP. Doppler measurements below 80 mmHg are a reliable indicator of arterial hypotension.Clinical relevanceDOP is acceptable for monitoring ABP in isoflurane-anaesthetized rabbits and is useful for detection of hypotension.     

Comparison of whole blood and plasma colloid osmotic pressure in healthy dogs

Objective – To determine the difference between colloid osmotic pressure (COP) values determined from plasma versus those determined from whole blood. Design – Prospective observational study. Settings – University veterinary teaching hospital. Animals – Fifty‐three healthy dogs. Interventions – None. Measurements and Main Results – Whole blood and plasma COP, CBC, plasma biochemistry. In all dogs, plasma COP values were significantly lower (P=0.02) than whole blood COP, with a mean of difference of 0.5 mm Hg. The mean and median whole blood COP was 21.75 and 21.4 mm Hg, respectively, with a range of 17.9–27.1 mm Hg. The mean and median plasma COP was 21.2 and 20.9 mm Hg with a range of 16.7–28.9 mm Hg. Conclusions – While significant difference exists between plasma and whole blood COP, the individual values are within expected reference intervals for dogs (21–25 mm Hg). Using either sample appears to provide the same information in clinically healthy dog; however, it is recommended that clinicians utilize the same sample type for comparison in an individual patient.     

Evaluation of a new oscillometric blood pressure monitor in isoflurane-anesthetized dogs

Objective This study was conducted to evaluate the performance of a new veterinary oscillometric noninvasive blood pressure (NIBP) monitor in anesthetized dogs. Study design Assessment was made to determine how closely indirect measurements were associated with direct measurements, and if there were statistically significant differences between the measurements by site. Animals Six mongrel dogs weighing 27.8 ± 2.9 kg. Methods Dogs were anesthetized with thiopental and maintained with isoflurane, which was delivered with controlled ventilation. Direct pressure measurements were obtained via a percutaneously placed arterial catheter. A range of systolic arterial pressures (SAP) were achieved by changing the isoflurane concentrations. Sites of cuff placement for indirect measurements were identified as metacarpus, metatarsus, and anterior tibial. Results At pressures below 80 mm Hg, indirect systolic measurements averaged 4 ± 3 mm Hg, higher than the direct values. At normal and high levels, indirect systolic measurements underestimated direct values by 18 ± 6 and 23 ± 6 mm Hg, respectively. Diastolic and mean pressure measurements followed the same trend, with indirect values being lower than the direct arterial pressures. Systolic, diastolic and mean arterial pressure measurements differed by cuff‐placement site. Conclusions When analyzed by site and level, indirect systolic and mean arterial blood pressures during hypotension were essentially the same as direct pressures. However, at pressures within the normal or high range, indirect measurements underestimated the direct pressures. Clinical relevance Noninvasive blood pressure measurements with a new oscillometric monitor provided an excellent means of detecting arterial hypotension in anesthetized dogs. The metatarsal site for cuff placement was slightly better than the metacarpal or anterior tibial site, considering that the regression line was closest to complete equality between the indirect and direct measurements for SAP.     

A comparison of direct and indirect (oscillometric) measurements of arterial blood pressure in anaesthetised dogs, using tail and limb cuffs

Oscillometric measurements of arterial blood pressure were compared with direct measurements in anaesthetised dogs being monitored during routine surgery. Readings were obtained with tail cuffs and limb cuffs and the reproducibility (precision) of the readings from various cuff sites was also compared in conscious dogs. Tail cuffs gave the best precision in conscious dogs and the closest correlation with direct measurements in anaesthetised dogs, especially for systolic pressure. The proximal hindlimb site gave results with a slightly lower precision.     

Comparison of high definition oscillometric and Doppler ultrasound devices with invasive blood pressure in anaesthetized dogs

Objective To use the American College of Veterinary Internal Medicine (ACVIM) validation criteria to evaluate the performance of high definition oscillometric (HDO) and Doppler blood pressure measurement techniques against invasive blood pressure measurements in anaesthetized dogs. Study design Prospective clinical study. Animals Twenty client‐owned dogs. Materials and Methods Invasive blood pressure was measured using a catheter inserted into a pedal artery and an electronic transducer. The sites of cuff placement for the HDO measurements were the mid antebrachium or the proximal tail and, for the Doppler technique, the distal tibia. Agreement between invasive and non‐invasive blood pressure measurements was estimated by the Bland–Altman method. Results Only 10% and 34% of Doppler measurements were within 10 and 20 mmHg of invasive blood pressure values, respectively. The Doppler device failed to meet the ACVIM validation criteria for blood pressure measurement devices. The best agreement between HDO and invasive blood pressure measurement technique was observed for mean arterial blood pressure (MAP); 67% and 95% of readings were within 10 and 20 mmHg of invasive blood pressure values respectively. In addition, 52% and 87% of diastolic arterial blood pressure (DAP) measurements were within 10 and 20 mmHg of invasive readings. High definition oscillometric readings did not meet ACVIM recommended limits for SAP. Conclusion and clinical relevance The Doppler technique overestimated and the HDO device showed limited agreement with invasive blood pressure measurement in anaesthetized dogs. High definition oscillometry met most of the ACVIM requirements for MAP and DAP while the Doppler technique did not.     

Accuracy of an oscillometric blood pressure monitor during phenylephrine-induced hypertension in dogs

OBJECTIVE: To examine the agreement between direct arterial blood pressure measurements obtained from 2 arteries and indirect blood pressure measurements obtained with an oscillometric blood pressure monitor (OBPM) during normotension and phenylephrine-induced hypertension in dogs. ANIMALS: 16 male Beagles. PROCEDURES: In anesthetized dogs, arterial catheters were placed in the lingual and dorsal pedal arteries for measurement of arterial blood pressure. A blood pressure cuff was placed on either the dog's fore- or hind limb and connected to an OBPM. Systolic, diastolic, and mean arterial blood pressures (SAP, DAP, and MAP, respectively) were recorded from both arteries and the OBPM every 5 minutes for 30 minutes (baseline), during a 30-minute period in which dogs received a phenylephrine infusion IV to induce hypertension, and for 30 minutes after discontinuation of the infusion. Mean differences in blood pressure values and confidence intervals were calculated to compare the indirect and direct measurement techniques. RESULTS: In dogs, oscillometry underestimated SAP during normotension, and the difference between oscillometric and direct measurements increased during hypertension. Oscillometry underestimated DAP, but the difference between oscillometric and direct measurements decreased during hypertension. There was close agreement among techniques for MAP determinations. Biases between direct measurements and OPBM blood pressure values measured from dogs' forelimbs or hind limbs were not significantly different. CONCLUSIONS AND CLINICAL RELEVANCE: In normotensive dogs, oscillometric measurements of MAP and SAP agreed more closely with direct arterial pressure measurements than oscillometric estimates of DAP. Oscillometric measurement of MAP was accurate during both normotension and hypertension in dogs.     

Comparison of direct and indirect blood pressure measurements in anesthetized dogs.

The precision and accuracy of an indirect oscillometric blood pressure measurement technique (Dinamap 8100) was assessed in 11 anesthetized Beagle dogs weighing 8 to 11.5 kg. Direct blood pressure measurements were made by catheterization of the lingual artery, and simultaneous indirect measurements were determined by placing a cuff over the median artery (midradial area). Blood pressure measurements at 2 different planes of anesthesia (light and deep) were recorded in triplicate. At a light plane of anesthesia, the Dinamap 8100 underestimated diastolic and mean arterial pressure, and at a deep anesthetic plane overestimated systolic pressure. The indirect technique had good repeatability of systolic pressures. Regression analysis for the 2 techniques showed excellent correlation (r = 0.93). The results indicate that the indirect oscillometric blood pressure measurement technique provides a good estimate of systolic, diastolic, and mean arterial pressure in dogs weighing 8-11.5 kg.     

The prevalence and significance of hyperglycemia in hospitalized cats

Objective – To report the prevalence of hyperglycemia in cats admitted to a veterinary hospital and to determine if hyperglycemic cats had increased morbidity and mortality when compared with normoglycemic cats.
Design – Retrospective clinical study.
Setting – Community-based referral hospital.
Animals – Nondiabetic cats admitted to the hospital.
Interventions – None.
Measurements and Main Results – The medical records of nondiabetic cats admitted to the hospital over a 1-year period were reviewed. There were 182 cats that met the criteria for inclusion in the study. Information obtained included signalment, length of hospitalization, initial and highest blood glucose measurement, diagnosis, treatment, and final disposition. Sixty-three percent of cats (116/182) were hyperglycemic at the time of presentation. Total incidence of hyperglycemia at any point during hospitalization was 64% (118/182). No association was found between hyperglycemia either initially or at any point during the hospitalization and mortality. However, a significant association was documented between the presence of hyperglycemia and increased length of hospitalization (LOH) ( P =0.04). The duration of LOH was also significantly associated with the degree of hyperglycemia ( P =0.01). A number of different disease processes were represented in the study population. However, the number of cats in each disease category was small and no association could be found between any of them and blood glucose affecting mortality and morbidity.
Conclusion – The prevalence of hyperglycemia in feline patients admitted to a primary referral hospital was 64%. Cats with hyperglycemia had a longer LOH when compared with normoglycemic cats; however, presence of hyperglycemia did not impact mortality in this population of cats.     

Original Study: Determination of normal intra‐abdominal pressure using urinary bladder catheterization in clinically healthy cats

Objective – To establish a reference interval for intra‐abdominal pressure (IAP) measured by urinary bladder catheterization in normal cats and determine if IAP is affected by observer variation, volume of saline instillation before measurement, or subject variables of gender, positioning, body condition score, and sedation. Design – Prospective experimental study. Setting – Private referral center. Animals – Twenty healthy adult cats. Interventions – Sedation with butorphanol, midazolam, and propofol for catheterization of the urinary bladder and measurement of IAP. Measurements and Main Results – A 5‐Fr red rubber urinary catheter was placed under sedation, and IAP was determined using a water manometer with the cats in right lateral and sternal recumbency. Three readings were taken in each position by 2 observers. The cats were allowed to recover with the urinary catheter in place, and IAP was measured in each cat while they were awake in right lateral and sternal recumbency. Conclusions – In this population of clinically healthy cats, median (interquartile range) IAP taken over all measurements was 7.00 cm H₂O (5.23–8.83 cm H₂O). There was no statistical difference between observers or subject gender. Factors associated with a statistically significant increase in IAP were right lateral compared with sternal recumbency (P=0.002), being awake compared with sedated (P<0.001), having a higher body condition score (P=0.01 and 0.001), instillation of a higher volume of saline into the bladder for measurement (P<0.001), and struggling during awake measurements (P<0.001).     

Validity and reliability of Doppler ultrasonography and direct arterial blood pressure measurements in anaesthetized dogs weighing less than 5 kg

Objective

To assess the validity and reliability of Doppler ultrasonography (DOP) as compared with invasive arterial blood pressure measurements in anaesthetized dogs weighing less than 5 kg.

Indirect oscillometric and direct blood pressure measurements in anesthetized and conscious neonatal foals

Objective: To investigate the agreement between indirect oscillometric and direct blood pressure measurement in the equine neonate. Design: Prospective observational study. Setting: University Veterinary Teaching Hospital. Animals: Ten crossbred foals of 30–46 hours of age. Interventions: Six animals (Group 1) were anesthetized. Four animals (Group 2) were restrained on a mat. All animals were instrumented with a catheter in the greater metatarsal artery and an oscillometric blood pressure cuff over the coccygeal artery. Blood pressure was varied with dobutamine, phenylephrine, nitroprusside, and increased depth of anesthesia (Group 1) or dopamine (Group 2). Measurements and main results: Simultaneous direct and indirect blood pressure measurements were obtained from the greater metatarsal artery and the coccygeal artery, respectively. There was good agreement between the 2 methods for mean and diastolic blood pressures in both groups, but not for systolic pressure. The agreement was best in mean blood pressure of anesthetized foals (mean bias –1.07; limits of agreement – 9.39, 7.25 mmHg). Conclusions: Indirect oscillometry appears to be an acceptable method for measuring mean arterial blood pressure in both anesthetized and conscious neonatal foals, and may be a valid method of monitoring critically ill foals.