Anderson F. da Cunha

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 animals 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.

Agreement between directly measured blood pressure and pressures obtained with three veterinary-specific oscillometric units in cats

OBJECTIVE To determine whether veterinary-specific oscillometric blood pressure units yield measurements that are in good agreement with directly measured blood pressures in cats. DESIGN Evaluation study. ANIMALS 21 cats undergoing routine spaying or neutering. PROCEDURES A 24-gauge catheter was inserted in a dorsal pedal artery, and systolic, diastolic, and mean arterial pressures were directly measured with a validated pressure measurement system. Values were compared with indirect blood pressure measurements obtained with 3 veterinary-specific oscillometric blood pressure units. RESULTS There was poor agreement between indirectly and directly measured blood pressures. For unit 1, bias between indirectly and directly measured values was -14.9 mm Hg (95% limits of agreement [LOA], -52.2 to 22.4 mm Hg), 4.4 mm Hg (95% LOA, -26.0 to 34.8 mm Hg), and -1.3 mm Hg (95% LOA, -26.7 to 24.1 mm Hg) for systolic, diastolic, and mean arterial pressures, respectively. For unit 2, bias was -10.3 mm Hg (95% LOA, -52.9 to 32.2 mm Hg), 13.0 mm Hg (95% LOA, -32.1 to 58.0 mm Hg), and 9.1 mm Hg (95% LOA, -32.9 to 51.2 mm Hg) for systolic, diastolic, and mean arterial pressures, respectively. For unit 3, bias was -13.4 mm Hg (95% LOA, -51.8 to 25.1 mm Hg), 8.0 mm Hg (95% LOA, -25.5 to 41.6 mm Hg), and -3.6 mm Hg (95% LOA, -31.6 to 24.5 mm Hg) for systolic, diastolic, and mean arterial pressures, respectively. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that none of the 3 veterinary-specific oscillometric blood pressure units could be recommended for indirect measurement of blood pressure in cats.

Agreement between direct and indirect blood pressure measurements obtained from anesthetized Hispaniolan Amazon parrots

OBJECTIVE To determine the level of agreement between direct and indirect blood pressure measurements obtained from healthy Hispaniolan Amazon parrots (Amazona ventralis) anesthetized with isoflurane. DESIGN Validation study. ANIMALS 16 healthy adult Hispaniolan Amazon parrots. PROCEDURES Parrots were anesthetized, and a 26-gauge, 19-mm catheter was placed percutaneously in the superficial ulnar artery for direct measurement of systolic, mean, and diastolic arterial pressures. Indirect blood pressure measurements were obtained with a Doppler ultrasonic flow detector and an oscillometric unit. The Bland-Altman method was used to compare direct and indirect blood pressure values. RESULTS There was substantial disagreement between direct systolic arterial blood pressure and indirect blood pressure measurements obtained with the Doppler detector from the wing (bias, 24 mm Hg; limits of agreement, -37 to 85 mm Hg) and from the leg (bias, 14 mm Hg; limits of agreement, -14 to 42 mm Hg). Attempts to obtain indirect blood pressure measurements with the oscillometric unit were unsuccessful. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that there was substantial disagreement between indirect blood pressure measurements obtained with a Doppler ultrasonic flow detector in anesthetized Hispaniolan Amazon parrots and directly measured systolic arterial blood pressure.

Measuring level of agreement between values obtained by directly measured blood pressure and ultrasonic Doppler flow detector in cats

OBJECTIVE To determine if blood pressure measured with an ultrasonic Doppler flow detector (Doppler) is in good agreement with directly measured blood pressures in anesthetized cats. DESIGN Prospective observational study. SETTING University veterinary teaching hospital. ANIMALS Thirty-nine cats undergoing routine neutering. INTERVENTIONS Cats were divided into 2 groups; 19 cats enrolled in Group A had a 24-Ga catheter inserted into a dorsal pedal artery; 20 cats in Group B had a 20-Ga catheter placed in a femoral artery. In both groups, systolic, diastolic, and mean arterial pressures were directly measured using a validated pressure measurement system. Indirect values were compared against direct blood pressure measurements. RESULTS There was no difference between groups. Overall, there was poor agreement with a significant bias observed between Doppler and directly measured blood pressures. For the systolic arterial pressure the bias was -8.8 with limits of agreements (LOA) of -39.3 and 21.7. For the mean arterial pressure, the bias was 14.0 with LOA of -13.9 and 41.9. For the diastolic arterial pressure, the bias was 27.9 with LOA of -4.4 and 60.2. Methodology, weight, sex, and replicates did not have a significant effect on the difference between indirect and direct measurements in any model. CONCLUSIONS Results suggest poor agreement between Doppler values and directly measured blood pressures in anesthetized cats. Use of Doppler in cats could be misleading and readings should be interpreted with caution in a clinical context.

Palpation- and ultrasound-guided brachial plexus blockade in Hispaniolan Amazon parrots (Amazona ventralis)

OBJECTIVE To compare palpation-guided with ultrasound-guided brachial plexus blockade in Hispaniolan Amazon parrots. STUDY DESIGN Prospective randomized experimental trial. ANIMALS Eighteen adult Hispaniolan Amazon parrots (Amazona ventralis) weighing 252-295 g. METHODS After induction of anesthesia with isoflurane, parrots received an injection of lidocaine (2 mg kg(-1)) in a total volume of 0.3 mL at the axillary region. The birds were randomly assigned to equal groups using either palpation or ultrasound as a guide for the brachial plexus block. Nerve evoked muscle potentials (NEMP) were used to monitor effectiveness of brachial plexus block. The palpation-guided group received the local anesthetic at the space between the pectoral muscle, triceps, and supracoracoideus aticimus muscle, at the insertion of the tendons of the caudal coracobrachial muscle, and the caudal scapulohumeral muscle. For the ultrasound-guided group, the brachial plexus and the adjacent vessels were located with B-mode ultrasonography using a 7-15 MHz linear probe. After location, an 8-5 MHz convex transducer was used to guide injections. General anesthesia was discontinued 20 minutes after lidocaine injection and the birds recovered in a padded cage. RESULTS Both techniques decreased the amplitude of NEMP. Statistically significant differences in NEMP amplitudes, were observed within the ultrasound-guided group at 5, 10, 15, and 20 minutes after injection and within the palpation-guided group at 10, 15, and 20 minutes after injection. There was no statistically significant difference between the two groups. No effect on motor function, muscle relaxation or wing droop was observed after brachial plexus block. CONCLUSIONS AND CLINICAL RELEVANCE The onset of the brachial plexus block tended to be faster when ultrasonography was used. Brachial plexus injection can be performed in Hispaniolan Amazon parrots and nerve evoked muscle potentials were useful to monitor the effects on nerve conduction in this avian species. Neither technique produced an effective block at the doses of lidocaine used and further study is necessary to develop a useful block for surgical analgesia.

Effects of dopamine and dobutamine on isoflurane-induced hypotension in Hispaniolan Amazon parrots (Amazona ventralis).

OBJECTIVE To assess the effects of dopamine and dobutamine on the blood pressure of isoflurane-anesthetized Hispaniolan Amazon parrots (Amazona ventralis). ANIMALS 8 Hispaniolan Amazon parrots. PROCEDURES A randomized crossover study was conducted. Each bird was anesthetized (anesthesia maintained by administration of 2.5% isoflurane in oxygen) and received 3 doses of each drug during a treatment period of 20 min/dose. Treatments were constant rate infusions (CRIs) of dobutamine (5, 10, and 15 μg/kg/min) and dopamine (5, 7, and 10 μg/kg/min). Direct systolic, diastolic, and mean arterial pressure measurements, heart rate, esophageal temperature, and end-tidal partial pressure of CO(2) were recorded throughout the treatment periods. RESULTS Mean ± SD of the systolic, mean, and diastolic arterial blood pressures at time 0 (initiation of a CRI) were 132.9 ± 22.1 mm Hg, 116.9 ± 20.5 mm Hg, and 101.9 ± 22.0 mm Hg, respectively. Dopamine resulted in significantly higher values than did dobutamine for the measured variables, except for end-tidal partial pressure of CO(2). Post hoc multiple comparisons revealed that the changes in arterial blood pressure were significantly different 4 to 7 minutes after initiation of a CRI. Overall, dopamine at rates of 7 and 10 μg/kg/min and dobutamine at a rate of 15 μg/kg/min caused the greatest increases in arterial blood pressure. CONCLUSIONS AND CLINICAL RELEVANCE Dobutamine CRI at 5, 10, and 15 μg/kg/min and dopamine CRI at 5, 7, and 10 μg/kg/min may be useful in correcting severe hypotension in Hispaniolan Amazon parrots caused by anesthesia maintained with 2.5% isoflurane.

Measuring the level of agreement between directly measured blood pressure and pressure readings obtained with a veterinary‐specific oscillometric unit in anesthetized dogs

OBJECTIVE To determine if an oscillometric device optimized for use in dogs produces systolic, diastolic, and mean arterial pressures (MAPs) measurements that are in good agreement with directly obtained pressures DESIGN Prospective study. SETTING University teaching hospital. ANIMALS Twenty-one dogs under general anesthesia for surgical procedures. INTERVENTIONS A 20-Ga catheter was placed into the dorsal pedal artery and systolic, diastolic, and MAPs were directly measured using a validated blood pressure measurement system. Indirect blood pressure measurements were collected using a widely available veterinary oscillometric blood pressure unit. Results obtained by the 2 methods were then compared. MEASUREMENTS AND MAIN RESULTS Agreement between the directly and indirectly measured pressure demonstrated a bias of 9.9 mm Hg and limits of agreement (LOA) 73.7 to -53.9, a bias of -8.9 mm Hg and LOA 23.3 to -41.2, and a bias of -6.3 mm Hg and LOA 28.2 to -40.8 for systolic, diastolic, and MAP, respectively. CONCLUSIONS There was poor agreement between the direct and indirect measured blood pressure measurement systems. Therefore, use of the oscillometric blood pressure unit evaluated in this study for monitoring patients under anesthesia cannot be recommended at this time.

Comparison of directly measured arterial blood pressure at various anatomic locations in anesthetized dogs.

OBJECTIVE To determine whether directly measured arterial blood pressure differs among anatomic locations and whether arterial blood pressure is influenced by body position. ANIMALS 33 client-owned dogs undergoing anesthesia. PROCEDURES Dogs undergoing anesthetic procedures had 20-gauge catheters placed in both the superficial palmar arch and the contralateral dorsal pedal artery (group 1 [n = 20]) or the superficial palmar arch and median sacral artery (group 2 [13]). Dogs were positioned in dorsal recumbency, and mean arterial blood pressure (MAP), systolic arterial blood pressure (SAP), and diastolic arterial blood pressure (DAP) were recorded for both arteries 4 times (2-minute interval between successive measurements). Dogs were positioned in right lateral recumbency, and blood pressure measurements were repeated. RESULTS Differences were detected between pressures measured at the 2 arterial sites in both groups. This was especially true for SAP measurements in group 1, in which hind limb measurements were a mean of 16.12 mm Hg higher than carpus measurements when dogs were in dorsal recumbency and 14.70 mm Hg higher than carpus measurements when dogs were in lateral recumbency. Also, there was significant dispersion about the mean for all SAP, DAP, and MAP measurements. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that arterial blood pressures may be dependent on anatomic location and body position. Because this may affect outcomes of studies conducted to validate indirect blood pressure measurement systems, care must be used when developing future studies or interpreting previous results.

Cardiovascular tolerance of intravenous lidocaine in broiler chickens (Gallus gallus domesticus) anesthetized with isoflurane

OBJECTIVE To determine the cardiovascular effects of lidocaine infused intravenously (IV) in broiler chickens. STUDY DESIGN Two phase study: Phase 1, randomized up-and-down study to determine effective dose 50 (ED50) for lidocaine; Phase 2, prospective randomized study to determine the cardiovascular effects of lidocaine. ANIMALS Seventeen Ross-708 broiler chickens (Gallus gallus domesticus) [11 chickens (Phase 1) and 6 chickens (Phase 2)], weighing 2.6-4.3 kg. METHODS After induction of anesthesia with isoflurane and placement of monitoring equipment including invasive blood pressure, chickens were administered lidocaine IV. During Phase 1, using an up-and-down design, each animal received a variable dose selected based on the response of the previous animal. During Phase 2, each animal was administered 6 mg kg(-1) of lidocaine IV over 2 minutes. Clinically irrelevant cardiovascular effects were defined as a relative decrease of heart rate (HR) and mean blood pressure (MAP) <30% subsequent to IV lidocaine administration. The ED50 was defined as the dose rate that would cause clinically irrelevant cardiovascular depression in 50% of the population. RESULTS During Phase 1, using an up-and-down study design (n = 11), the ED50 of lidocaine was determined to be 6.30 mg kg(-1) and 6.22 mg kg(-1) (95% confidence interval, 5.30-7.13 mg kg(-1)), when calculated by Dixons up-and-down method, and logistic regression, respectively. During Phase 2, following infusion of lidocaine (6 mg kg(-1)), no clinically relevant effects on HR or MAP were detected in any animal. CONCLUSIONS AND CLINICAL RELEVANCE Previous reports state that the dose of lidocaine used in birds should be ≤4 mg kg(-1). In this study, 6 mg kg(-1) of lidocaine injected IV was not associated with adverse cardiovascular effects. These results suggest that the dose of 4 mg kg(-1) can be exceeded, at least in chickens, and opens the possibility of other therapeutic uses for lidocaine in birds.

Evaluation of four methods for inducing death during slaughter of American alligators (Alligator mississippiensis)

OBJECTIVE To evaluate physical methods for inducing death during the slaughter of American alligators (Alligator mississippiensis). ANIMALS 24 captive hatched-and-reared American alligators. PROCEDURES Baseline electroencephalograms (EEGs) were obtained for awake and anesthetized alligators. Corneal reflex, spontaneous blinking, and EEGs were evaluated after severance of the spinal cord, severance of the spinal cord followed by pithing of the brain, application of a penetrating captive bolt, or application of a nonpenetrating captive bolt (6 alligators/group). RESULTS Overall, alligators subjected to spinal cord severance alone differed from those subjected to the other techniques. Spinal cord severance alone resulted in postprocedure EEG power values greater than those in anesthetized alligators, whereas the postprocedure EEG power values were isoelectric for the other 3 techniques. Corneal reflex and spontaneous blinking were absent in all alligators immediately after application of a penetrating or nonpenetrating captive bolt. One of 6 alligators had a corneal reflex up to 1 minute after pithing, but all others within that group had immediate cessation of reflexes after pithing. Mean time to loss of spontaneous blinking and corneal reflex for alligators subjected to spinal cord severance alone was 18 minutes (range, 2 to 37 minutes) and 54 minutes (range, 34 to 99 minutes), respectively. CONCLUSIONS AND CLINICAL RELEVANCE Spinal cord severance followed by pithing of the brain and application of a penetrating or nonpenetrating captive bolt appeared to be humane and effective techniques for inducing death in American alligators, whereas spinal cord severance alone was not found to be an appropriate method.