Comparison of direct and indirect methods of intra‐abdominal pressure measurement in normal horses

Objectives – To develop a direct method for measuring intra‐abdominal pressures in the standing horse, identify a reference interval for direct intra‐abdominal pressures, compare these pressures to indirect intra‐abdominal pressures measured from the bladder, and determine the optimal bladder infusion volume for indirect pressure measurement. Design – Prospective, experimental study. Setting – A university‐based equine research facility. Animals – Ten healthy adult horses, 5 males and 5 females. Interventions – Direct intra‐abdominal pressures were measured through an intraperitoneal cannula and zeroed at the height midway between the height of the tuber ishii and point of the shoulder. Indirect measurements of intra‐abdominal pressure were performed by measuring intravesicular pressures through a transurethral catheter zeroed at the tuber ishii. Measurements and Main Results – Direct pressure measurements obtained in the standing horse were subatmospheric (mean, ?1.80 cm H₂O; SD, 1.61 cm H₂O; 95% CI, ?2.80 to ?0.80) and were shown to decrease as the horse's weight increased (Pearson's r=?0.67, P=0.04), with no effect of head position (P=0.15). Mean baseline indirect pressure measurements (mean, ?8.63 cm H₂O; SD, 4.37 cm H₂O; 95% CI, ?13.05 to ?4.21) were significantly different from the pressures measured directly from the abdomen (P<0.001). Indirect pressure measurements were noted to increase with increasing volumes infused into the bladder, and were statistically different at a volume of 100 mL (P=0.004). There was low to moderate correlation between direct and indirect pressure measurements of intra‐abdominal pressure over a range of fluid volumes infused into the bladder (Pearson's correlation range ?0.38 to 0.58). Conclusion – Pressures measured directly in the standing horse were subatmospheric, and increased as the horse's weight increased. Indirect pressures measured were altered by increasing volumes infused in the bladder. There was no significant correlation between the 2 methods of intra‐abdominal pressure measurement.     

A technique for central venous pressure measurement in normal horses

Objective – To investigate a technique of central venous pressure (CVP) measurement using a newly developed catheter in healthy adult horses. Design – Prospective experimental study. Setting – University research facility. Animals – Twenty healthy adult horses. Interventions – An equine central venous catheter was inserted into the jugular vein to a length of approximately 80 cm from the mid‐cervical region in an attempt to catheterize the pulmonary artery. Pulmonary arterial catheterization was confirmed by echocardiography. Insertion distance and pressure were measured at this location with a disposable manometer. The catheter was then withdrawn until presence in the right atrium was confirmed by echocardiography. Insertion distance and pressure were also measured at this location. The catheter was then withdrawn in 5 cm increments until exiting the jugular insertion site with pressure measured at each location. All pressure measurements were taken with the manometer zero position at the point of the shoulder. Measurements and Main Results – Pulmonary artery catheterization was successful in 16 of 20 horses. Mean pulmonary arterial pressure was 23.8 cm H₂O (17.5 mm Hg) (95% confidence interval [CI] 20.9–26.7 cm H₂O [15.4–19.6 mm Hg]). Mean right atrial pressure was 8.3 cm H₂O (6.1 mm Hg) (95% CI 7.1–9.4 cm H₂O [5.2–6.9 mm Hg]). Right atrial pressure was compared with pressures recorded at sequential insertion distances and resulted in a recommendation for catheter insertion of at least 40 cm for CVP measurement in adult horses. Jugular venous pressure measurement was statistically different from CVP measurement. Conclusions – This catheter measurement technique is well tolerated in normal horses. Routine clinical use of this equine central venous catheter may improve our ability to monitor patients and improve patient care and outcomes of ill horses in hospital.     

Continuous positive airway pressure administered via face mask in tranquilized dogs

Objective – To evaluate the tolerance of a continuous positive airway pressure (CPAP) mask in tranquilized dogs and compare PaO₂ in arterial blood in dogs receiving oxygen with a regular face mask or CPAP mask set to maintain a pressure of 2.5 or 5 cm H₂O. Design – Prospective, randomized clinical study. Setting – University teaching hospital. Animals – Sixteen client‐owned dogs without evidence of cardiopulmonary disease were studied. Interventions – Eight animals were randomly assigned to each of 2 treatment groups: group A received 2.5 cm H₂O CPAP and group B received 5 cm H₂O CPAP after first receiving oxygen (5 L/min) by a regular face mask. Animals were tranquilized with acepromazine 0.05 mg/kg, IV and morphine 0.2 mg/kg, IM. An arterial catheter was then placed to facilitate blood sampling for pHa, PaO₂, and PaCO₂ determinations before and after treatments. Direct mean arterial pressure, heart rate, respiratory rate, and temperature were also recorded after each treatment. Measurements and Main Results – CPAP administration was well tolerated by all animals. The mean arterial pressure, heart rate, respiratory rate, temperature, PaCO₂, and pHa, did not differ at any time point between groups. Differences were seen in oxygenation; in group A, PaO₂ significantly increased from a mean of 288.3±47.5 mm Hg with a standard mask to a mean of 390.3±65.5 mm Hg with the CPAP mask and in group B, PaO₂ increased similarly from 325.0±70.5 to 425.2±63.4 mm Hg (P<0.05); no differences were detected between the 2 CPAP treatments. Conclusions – In healthy tranquilized dogs noninvasive CPAP is well tolerated and increases PaO₂ above values obtained when using a regular face mask.     

Effects of thiopentone and propofol on lower oesophageal sphincter and barrier pressure in the dog

The effects of thiopentone and propofol on oesophageal pressures were examined in 39 bitches. The dogs were premedicated with either atropine (n = 13), acepromazine maleate (n = 13) or a combination of atropine and acepromazine. Anaesthesia was induced with either thiopentone (15 dogs) or propofol (24 dogs), both given intravenously. Immediately following the induction of anaesthesia, gastric pressure and lower oesophageal sphincter pressure (LOSP) were measured and oesophageal barrier pressure determined. There were no significant differences attributable to the premedication regimens used but both LOSP and barrier pressure were significantly lower in the dogs anaesthetised with propofol compared to the animals given thiopentone (LOSP 12-2 ± 4-2 cm H₂O propofol group versus 26-8 ± 6-5 cm H₂O thiopentone group).     

Evaluation of the endotracheal tube cuff pressure resulting from four different methods of inflation in dogs

Objective To evaluate the endotracheal tube cuff pressure achieved by four different inflation methods. Study design Prospective clinical study. Animals Eighty client owned dogs. Methods After anaesthesia induction, endotracheal intubation was performed using plastic or silicone tubes. A clinician unaware of tube type inflated the cuff by simple digital palpation (method A), thereafter the cuff was deflated and inflated again by a second clinician who tried to reproduce a previously learned cuff pressure of between 19 and 24 mmHg (method B). During method C the cuff was inflated to the minimum occlusive volume at an airway pressure of 20 cm H₂O, and in method D the cuff was incrementally deflated until an audible air leak could be heard from the oral cavity at an airway pressure of 25 cm H₂O. For all the methods, an operator recorded the actual cuff pressure obtained using a manometer. Heart rate, respiratory rate and mean arterial pressure were monitored throughout the procedure. Results The mean inflation pressure for plastic tubes was 56 ± 28 mmHg for method A, 20 ± 9 mmHg for method B, 35 ± 32 mmHg for method C and 46 ± 39 mmHg for method D. Pressures using silicone tubes were significantly higher than for plastic tubes, the mean registered pressures being 79 ± 39, 33 ± 16, 77 ± 50 and 92 ± 56 mmHg for methods A, B, C and D. Conclusions and Clinical Relevance None of the methods evaluated in this study can be considered effective for inflating the endotracheal tube cuff to within the optimal range when using silicone tubes. Direct measurement of the cuff pressure with a manometer is therefore recommended.     

The effect of user experience and inflation technique on endotracheal tube cuff pressure using a feline airway simulator

Objective

The effect of user experience and inflation technique on endotracheal tube cuff pressure using a feline airway simulator.

Influence of fentanyl on intra-abdominal pressure during laparoscopy in dogs

ObjectiveTo evaluate the influence of fentanyl on intra-abdominal pressures in spontaneously breathing dogs during capnoperitoneum.Study designProspective clinical study.AnimalsEleven healthy client-owned and five healthy experimental dogs undergoing laparoscopy.MethodsDogs were premedicated with acepromazine (0.03 mg kg^?1 IV) and carprofen (4 mg kg^?1 IV). Anaesthesia was induced with propofol and maintained with isoflurane in oxygen. The abdomen was insufflated with CO₂ (11–16 cm H₂O). Intra-abdominal pressures were measured with a transducer. Respiratory variables were measured with a spirometry sensor and side-stream capnography. Following preparation, fentanyl (1 μg kg^?1) was injected over 30 seconds IV. Data were recorded 5 minutes before, during and 5 minutes after treatment. The following time points were selected for statistical analysis (anova, p < 0.05): ?160, ?140, ?120, ?100, ?80, ?60, ?40, ?20, 0, 30, 50, 70, 90, 110, 130 and 150 seconds after the start of fentanyl injection.ResultsIntra-abdominal pressure increased during inspiration in 15 dogs but decreased in one dog. Fentanyl treatment did not alter these patterns. Peak inspiratory and end-expiratory intra-abdominal pressures continuously decreased over time during the whole experiment and fentanyl exaggerated the decrease in inspiratory pressures but did not affect the rate of decrease in expiratory pressures. Differences between intra-abdominal pressures were stable before, but decreased after fentanyl administration from 4.1 ± 1.4 to 3.3 ± 1.2 cm H₂O (at 0 and 150 seconds time points). End-tidal CO₂ partial pressures increased from 6.0 ± 0.8 to 6.6 ± 0.9 kPa, respiratory rate decreased from 10.8 ± 2.6 to 7.8 ± 2.2 breaths per minute and tidal volume decreased from 13.7 ± 4.4 to 12.4 ± 2.9 mL kg^?1 after fentanyl but these variables did not change before fentanyl treatment. Airway pressures did not change.Conclusions and clinical relevanceFentanyl did not increase intra-abdominal pressures in dogs.     

Correlation between jugular and central venous pressures in laterally recumbent horses

Objective To compare and correlate right atrial pressure, which represents central venous pressure (CVP) to jugular vein pressure (JVP) in laterally recumbent horses under anesthesia. Study design Retrospective clinical trial. Animals Seven adult healthy horses (411 ± 8.7 kg). Methods Horses were sedated with IV xylazine and anesthesia was obtained with IV ketamine and diazepam. Anesthesia was maintained with sevoflurane in oxygen. All horses were positioned in left lateral recumbency. An 8F catheter introducer was inserted into the right jugular vein to measure JVP. An 8F catheter introducer was inserted into the left jugular vein to be used as the port for a 7F 110 cm catheter that reached the right atrium to measure CVP. Both, CVP and JVP were measured simultaneously with a water calibrated aneroid manometer using the sternum as the 0 cmH₂O reference point. Measurements were compared using Spearman correlation and the Bland‐Altman plot. Results Twenty paired samples were obtained over a period of 2 hours. The CVP ranged from 7 to 31 cmH₂O, while the JVP ranged from 5 to 30 cmH₂O. The Spearman correlation coefficient indicated that CVP and JVP had a strong correlation with r = 0.88. The Bland‐Altman plot showed a bias of 0.7 cmH₂O. Conclusion and clinical relevance Jugular vein pressure showed a strong correlation with CVP in healthy, euvolemic, laterally recumbent anesthetized adult horses. Thus, JVP cannot replace CVP but it may be used clinically to monitor CVP in laterally recumbent horses.     

Bronchopulmonary Disease in the Cat: Historical, Physical, Radiographic, Clinicopathologic, and Pulmonary Functional Evaluation of 24 Affected and 15 Healthy Cats

The results of clinical and pulmonary functional evaluation of 24 cats with bronchopulmonary disease and 15 healthy cats are presented. Affected cats had historical evidence of excessive reflexes (coughing, sneezing); physical evidence of airway secretions (crackles), obstruction (wheezing), and increased tracheal sensitivity; radiographic evidence of bronchial and interstitial lung disease; and cytological evidence of airway inflammation or mucous secretions. Bacterial isolates from healthy and affected cats were predominantly Gram-negative rods, indicating that bronchi of cats are not always sterile and that normal flora should be considered in interpreting cultures from cats with suspected bronchopulmonary disease. Cats were grouped according to relative disease severity based on scored historical, physical, and radiographic abnormalities. The mean (± standard deviation) baseline lung resistance measurement in healthy cats was 28.9 cm H₂O/L/s (±6.2 cm H₂O/L/s), whereas in mildly, moderately, and severely affected cats it was 38.3 cm H₂O/L/s (±21.5 cm H₂O/L/s), 44.8 cmH₂O/L/s (±7.7 cm H₂O/L/s), and 105.2 cm H₂O/L/s (±66.9 cm H₂O/L/s), respectively. In healthy cats, dynamic lung compliance was 19.8 (±7.4), whereas in mildly, moderately, and severely affected cats it was 14.7 mL/cm H₂O (±3.8 mL/cm H₂O), 17.7 mL/cm H₂O (±6.9 mL/cm H₂O), and 13.0 mL/cm H₂O (±7.9 mL/cm H₂O), respectively. Thus, airway obstruction was present in many of the affected cats. Based on acute response to the bron-chodilator, terbutaline, airway obstruction was partially reversible in many affected cats, although the degree of reversibility varied. Furthermore, based on bronchoprovocation testing, 6 (of 7) affected cats evaluated also had increased airway responsiveness to aerosolized methacholine.     

Endotracheal intubation in horses: a study of two cuff inflation pressures, correlation with liquid aspiration, and tracheal wall damage

Nine adult horses were anesthetized for a nonsurvival abdominal adhesion study. Horses were randomly assigned into two groups to receive endotracheal tube cuff pressures of either 80 cm H₂O (Group P80) or 120 cm H₂O (Group P120). After intubation (Bivona 30 mm ID), anesthesia was maintained with isoflurane. Horses were ventilated 10 times per minute with a suitable inspiratory pressure to maintain Pe ′CO₂ in the 35–40 mm Hg (4.7–6.0 kPa) range. Cuff pressure was continuously monitored with a pressure transducer (TruWave, Baxter) calibrated to the atmospheric pressure and maintained at a constant pressure. Twenty‐five millilitres of methylene blue dye in saline were instilled proximal to the cuff over 5 minutes. The horses were euthanized 123 ± 23 minutes later (mean ± SD). Immediately, the trachea was opened distal to the tip of the endotracheal tube, and the mucosa was observed for evidence of dye leaking past the cuff. The cervical trachea was resected and the lumen exposed by a ventral longitudinal incision. Biopsies (1–2 rings) were obtained at mid‐cuff level and distal to the tip of the endotracheal tube, and placed in formalin for later histologic examinations (H&E stain). Methylene blue stain was not observed distal to the endotracheal tube cuff in any horse. Visual examination of the tracheal mucosa revealed hyperemic or hemorrhagic lesions at the level of cuff contact both ventrally and dorsally. Histologic changes included epithelium damage, submucosal neutrophil infiltrates, and acute submucosal hemorrhages. P80 horses had none or focal to multifocal lesions on the ventral and dorsal aspects of the rings. P120 horses had multifocal to diffuse lesions on all aspects (dorsal, ventral, and lateral). We concluded that the endotracheal tube cuff produced a seal sufficient to prevent leakage at both pressures. Tracheal damages on gross and microscopic examinations were more severe and occurred more frequently at the higher cuff pressure.     

Assessment of cardiac output measurement in dogs by transpulmonary pulse contour analysis

Objective – To determine if metatarsal artery pressure (COmet) is comparable to femoral artery pressure (COfem) as the input for transpulmonary pulse contour analysis (PiCCO) in anesthetized dogs, using the lithium dilution method (LiDCO) as a standard for cardiac output (CO) measurement. Design – Prospective randomized study. Setting – University research laboratory. Animals – Ten healthy purpose‐bred mixed breed dogs were anesthetized and instrumented to measure direct blood pressure, heart rate, arterial blood gases, and CO. Interventions – The CO was measured using LiDCO and PiCCO techniques. Animals had their right femoral and left distal metatarsal artery catheterized for proximal (COfem) and distal (COmet) PiCCO analysis, respectively. Measurements were obtained from each animal during low, normal, and high CO states by changing amount of inhalant anesthetics and heart rate. Measurements were converted to CO indexed to body weigh (CI_BW=CO/kg) for statistical analysis. Agreement was determined using Bland and Altman analysis and concordance correlation coefficients. Measurements and Main Results – Thirty paired measurements were taken. The LiDCO CI_BW (± SD) was 68.7 ± 30.3, 176.0 ± 53.0, and 211.1 ± 76.5 mL/kg/min during low, normal, and high CO states, respectively. There was a significant effect of CI_BW state on bias and relative bias with COmet (P<0.001 and P=0.003, respectively). Bias of the COmet method (± SD) was ?116.6 (70.5), 20.1(76.4), and 91.3 (92.0) mL/kg/min at low, normal, and high CI_BW, respectively. Bias of the COfem (± SD) was ?20.3 (19.0), 8.6 (70.9), and ?2.9 (83.0) mL/kg/min at low, normal, and high CI_BW, respectively. The mean relative bias for COfem was ?6.7 ± 44% (limits of agreements: ?81.2 to 67.9%). Conclusion – Compared with lithium dilution, the pulse contour analysis provides a good estimation of CO, but requires femoral artery catheterization in anesthetized dogs.     

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).     

Subarachnoid pressures and cardiorespiratory parameters during cisternal myelography in isoflurane anaesthetized dogs

ObjectiveTo measure subarachnoid pressures, systemic circulatory and respiratory effects, and to calculate cerebral perfusion pressure during cisternal myelography.Study designProspective clinical study.AnimalsForty‐three client owned dogs with clinical signs of spinal disease, weighing 6–56 kg.MethodsDogs were premedicated with butorphanol and diazepam intravenously (IV) and anaesthesia was induced with propofol and maintained with isoflurane vaporized in oxygen. Ventilation was spontaneous. Heart and respiratory rates, invasive mean arterial blood pressure (MAP), end tidal carbon dioxide and isoflurane concentration were measured continuously. Initial subarachnoid pressure (SaP₀) was measured in the cisterna magna with a needle pressure gauge. Iohexol 0.3 mL kg^?1 was injected at a rate of 4.1 mL minute^?1 into the cerebellomedullary cistern. The SaP was recorded during and at 120 seconds after contrast administration. The maximum SaP (SaP_max) and minimum calculated cerebral perfusion pressure (CPP_min) were recorded for each case.ResultsPrior to contrast injection, mean ± SD, MAP was 73 ± 20 mmHg and SaP₀ was 10 ± 3 mmHg. The cerebral perfusion pressure (CPP) was 64 ± 20 mmHg. The contrast injection increased the SaP₀ to 73 ± 33 mmHg (SaP_max). After injection, MAP increased to 97 ± 25 mmHg and the CPP decreased to 14 ± 34 mmHg. A negative correlation was found between the lowest CPP and body weight (ρ = ?0.77, p < 0.0001). Nine dogs had bradycardia, apnoea and hypertension, 21 dogs had at least one of these signs. The number of clinical signs showed significant correlation with body weight (ρ = ?0.68, p < 0.0001), SaP_max (ρ = ?0.66, p < 0.0001) and CPP_min (ρ = ?0.73, p < 0.0001).Conclusions and clinical relevanceCerebral perfusion can severely decrease during cisternal myelography using the standard dose of iohexol. Bradycardia, apnoea and systemic hypertension were associated with decreased CPP.     

Comparison of femoral and auricular arterial blood pressure monitoring in pigs

Objective To compare arterial blood pressure measurements obtained from the femoral and auricular arteries in anaesthetized pigs. Study design Prospective experimental study. Animals Fifteen female Large White pigs were used weighing 21.3 ± 2.3 kg. Methods The pigs were anaesthetized with tiletamine/zolazepam and xylazine administered intramuscularly, and anaesthesia maintained with isoflurane delivered in oxygen/nitrogen. Arterial oxygen partial pressures were maintained between 11.3 and 13.3 kPa and PaCO₂ between 4.6 and 6.0 kPa. Monitoring included electrocardiogram, capnography and invasive blood pressure. The auricular and femoral arteries were catheterized for continuous systolic (SAP), diastolic (DAP) and mean arterial pressure (MAP) measurements. Measurements were recorded every 15 minutes. Statistical analysis involved a Bland–Altman plot analysis. Results The mean difference ± confidence intervals between the femoral and the auricular arterial diastolic, systolic and mean blood pressure measurements during hypotension were 2 ± 7, 2 ± 5 and 2 ± 5 mmHg respectively. In conditions of normotension mean difference ± confidence intervals, of femoral and auricular arterial blood pressure measurements of diastolic, systolic and mean blood pressure were 4 ± 5, 3 ± 7 and 4 ± 4 mmHg respectively. In conditions of increased arterial blood pressure, mean difference ± confidence intervals, of femoral and auricular arterial blood pressure measurements of diastolic, systolic and mean blood pressure were 4 ± 5, 3 ± 8 and 4 ± 4 mmHg respectively. Conclusion Auricular artery catheterization is easier and quicker to perform. Pressure measurements from the auricular artery compared well with the femoral artery. Clinical relevance We found that auricular arterial blood pressures were similar to femoral arterial values under the conditions of this experiment. We did not test extremes of blood pressure or significant alterations in body temperature.     

Effects of bilateral arytenoid cartilage stenting on canine laryngeal resistance ex vivo

Objective: To evaluate the effect of Nitinol stents for bilateral arytenoid lateralization on canine laryngeal resistance. Study Design: Ex vivo experimental study. Animals: Canine cadaver larynges (n=7). Methods: Laryngeal resistance was calculated in all specimens with the epiglottis in open and closed positions. Bilateral arytenoid stenting was performed, rima glottidis width measured, and laryngeal resistance calculated. The effects of stenting on laryngeal resistance were evaluated by repeated measures ANOVA. Results: Calculated laryngeal resistance in the 3 stented groups, 2 cm (0.034±0.059 cmH₂O/L/s), 3 cm (0.034±0.059 cmH₂O/L/s), and 4 cm (0.034±0.059 cm H₂O/L/s), was significantly decreased versus the control (unstented) group (0.947±0.624 cmH₂O/L/s; P=.0098) with an epiglottis in the normal position. Calculated laryngeal resistance in the 3 stented groups, 2 cm (43.407±17.348 cm H₂O/L/s), 3 cm (70.659±34.705 cmH₂O/L/s), and 4 cm (92.637±44.509 cm H₂O/L/s), was significantly increased versus the control (unstented) group (29.561±14.499 cm H₂O/L/s) (P=.0185) with an epiglottis in the closed position. The width of the rima glottidis correlated with the size of the stent (r=0.95, P<.001). Conclusions: Bilateral arytenoid stenting significantly reduced calculated laryngeal resistance with an open epiglottis. Stenting resulted in a significant increase in laryngeal resistance versus the control with a closed epiglottis. Use of bilateral arytenoid stenting in clinical cases of laryngeal paralysis may provide an adequate decrease in open‐epiglottis airway resistance to alleviate clinical signs, while increasing closed‐epiglottis airway resistance. This could potentially lead to a decrease in the risk of postoperative aspiration pneumonia.     

Agreement between direct, oscillometric and Doppler ultrasound blood pressures using three different cuff positions in anesthetized dogs

ObjectiveTo evaluate the agreement between invasive blood pressure (IBP) and Doppler ultrasound blood pressure (DUBP) using three cuff positions and oscillometric blood pressure (OBP) in anesthetized dogs.Study designProspective study.AnimalsNine adult dogs weighing 14.5–29.5 kg.MethodsThe cuff was placed above and below the tarsus, and above the carpus with the DUBP and above the carpus with the OBP monitor. Based on IBP recorded via a dorsal pedal artery catheter, conditions of low, normal, and high systolic arterial pressures [SAP (mmHg) <90, between 90 and 140, and >140, respectively] were induced by changes in isoflurane concentrations and/or dopamine administration. Mean biases ± 2 SD (limits of agreement) were determined.ResultsAt high blood pressures, regardless of cuff position, SAP determinations with the DUBP underestimated invasive SAP values by more than 20 mmHg in most instances. With the DUBP, cuff placement above the tarsus yielded better agreement with invasive SAP during low blood pressures (0.2 ± 16 mmHg). The OBP underestimated SAP during high blood pressures (?42 ± 42 mmHg) and yielded better agreement with IBP for mean (MAP) and diastolic (DAP) arterial pressure measurements [overall bias: 2 ± 15 mmHg (MAP) and 0.2 ± 16 mmHg (DAP)].ConclusionsAgreement of SAP determinations with the DUBP is poor at SAP > 140 mmHg, regardless of cuff placement. Measurement error of the DUBP with the cuff placed above the tarsus is clinically acceptable during low blood pressures. Agreement of MAP and DAP measurements with this OBP monitor compared with IBP was clinically acceptable over a wide pressure range.Clinical relevanceWith the DUBP device, placing the cuff above the tarsus allows reasonable agreement with IBP obtained via dorsal pedal artery catheterization. Only MAP and DAP provide reasonable estimates of direct blood pressure with the OBP monitor evaluated.     

Effects of suture tension during unilateral cricoarytenoid lateralization on canine laryngeal resistance in vitro

Objective— To evaluate the effect of abduction suture tension for unilateral arytenoid lateralization on laryngeal resistance. Study Design— Experimental study. Animals— Canine cadaver larynges (n=16). Methods— Laryngeal resistance was calculated in all specimens with the epiglottis in open and closed positions. Left cricoarytenoid lateralization was performed under low or high suture tension, and laryngeal resistance was re‐calculated. The effects of suture tension on laryngeal resistance were evaluated by repeated measures ANOVA. Results— Cricoarytenoid lateralization under low or high suture tension significantly reduced laryngeal resistance with the epiglottis in an open or closed position. There was no difference in laryngeal resistance with an open epiglottis between the low‐tension (1.00±0.0001 cm H₂O/L/s) and high‐tension (1.10±0.35 cm H₂O/L/s) groups (P=.33). The low‐tension group (22.80±14.20 cm H₂O/L/s) had significantly greater laryngeal resistance than the high‐tension group (8.45±4.00 cm H₂O/L/s) with a closed epiglottis (P=.016). There was no difference in laryngeal resistance with a closed epiglottis for the low‐tension group before (34.30±36.50 cm H₂O/L/s) and after (22.80±14.20 cm H₂O/L/s; P=.42) arytenoid lateralization. Conclusions— Cricoarytenoid lateralization under low suture tension significantly reduced laryngeal resistance with an open epiglottis, but resulted in a significantly greater resistance with a closed epiglottis than cricoarytenoid lateralization under high suture tension. Clinical Relevance— Clinically, use of a low‐tension suture for cricoarytenoid lateralization may provide an adequate decrease in open‐epiglottis laryngeal resistance to alleviate clinical signs, while maintaining enough closed‐epiglottis laryngeal resistance to reduce the risk of postoperative aspiration pneumonia.     

Comparison of cardiac output determined by arterial pulse pressure waveform analysis method (FloTrac/Vigileo) versus lithium dilution method in anesthetized dogs

Objective – To compare the determination of cardiac output (CO) via arterial pulse pressure waveform analysis (FloTrac/Vigileo) versus lithium dilution method. Design – Prospective study. Setting – University teaching hospital. Animals – Six adult dogs. Interventions – Dogs were instrumented for CO determinations using lithium dilution (LiDCO) and FloTrac/Vigileo methods. Direct blood pressure, heart rate, arterial blood gases, and end‐tidal isoflurane (ETIso) and CO₂ concentrations were measured throughout the study while CO was manipulated with different depth of anesthesia and rapid administration of isotonic crystalloids at 60 mL/kg/h. Measurements and Main Results – Baseline CO measurements were obtained at 1.3% ETIso and were lowered by 3% ETIso. Measurements were obtained in duplicate or triplicate with LiDCO and averaged for comparison with corresponding values measured continuously with the FloTrac/Vigileo method. For 30 comparisons between methods, a mean bias of ?100 mL/kg/min and 95% limits of agreement between ?311 and +112 mL/kg/min (212 mL/kg/min) was determined. The mean (mL/kg/min) of the differences of LiDCO?Vigileo=62.0402+?0.8383 × Vigileo, and the correlation coefficient (r) between the 2 methods 0.70 for all CO determinations. The repeatability coefficients for the individual LiDCO and FloTrac/Vigileo methods were 187 and 400 mL/kg/min, respectively. Mean LiDCO and FloTrac/Vigileo values from all measurements were 145 ± 68 mL/kg/min (range, 64–354) and 244 ± 144 mL/kg/min (range, 89–624), respectively. The overall mean relative error was 48 ± 14%. Conclusion – The FloTrac/Vigileo overestimated CO values compared with LiDCO and the relative error was high, which makes this method unreliable for use in dogs.     

Aspects of in vivo endotracheal tube intracuff pressure in cats

Objectives

To determine the endotracheal tube cuff pressure produced with two inflation techniques, in two brands of endotracheal tube in cats. To determine the inspiratory pressure which produces an audible leak when the intracuff pressure is 30 cmH₂O.

Agreement of high definition oscillometry with direct arterial blood pressure measurement at different blood pressure ranges in horses under general anaesthesia

ObjectiveTo determine the agreement of high definition oscillometry (HDO) with direct arterial blood pressure measurements in normotensive, hypotensive and hypertensive horses during general anaesthesia.Study designExperimental study.AnimalsSeven healthy warmblood horses, aged 3–11 years, weighing 470–565 kg.MethodsMeasurements from a HDO device with the cuff placed around the base of the tail were compared with pressures measured invasively from the facial artery. High blood pressures were induced by intravenous (IV) administration of dobutamine (5 μg kg⁻¹ minute⁻¹) over ten minutes followed by norepinephrine (0.1 mg kg⁻¹ IV) and low pressures by increasing the inspired fraction of isoflurane and administration of nitroglycerine (0.05 mg kg⁻¹ IV). For analysis three pressure levels were determined: high (MAP>110 mmHg), normal (60 mmHgResultsA total of 245 paired measurements of systolic (SAP), mean (MAP) and diastolic (DAP) pressures were obtained. The HDO device underestimated blood pressure at hypertensive and normotensive levels and overestimated blood pressure at hypotensive levels. Best agreement was obtained for SAP and MAP within normotensive limits. At normotension, bias ± standard deviation for SAP, MAP and DAP were 0.1 ± 19.4 mmHg, 0.5 ± 14.0, 4.7 ± 15.6, respectively. At high pressure levels bias and SD were 26.1 ± 37.3 (SAP), 4.2 ± 19.4 (MAP), 1.5 ± 16.8 (DAP) and at low pressures -20.0 ± 20.9 (SAP), -11.4 ± 19.6 (MAP), -4.7 ± 20.1 (DAP), with HDO measurements at a MAP <50 mmHg often failing.Conclusion and clinical relevanceGood agreement with invasive arterial blood pressures was obtained with HDO at normotensive levels in horses. At high and low pressure ranges HDO was unreliable. Therefore, if haemodynamic instability is expected, invasive measurement remains preferable.