Agreement between invasive blood pressure measured centrally and peripherally in anaesthetized horses.

OBJECTIVE: To determine the agreement of invasive blood pressure measured in the facial, metatarsal and carotid arteries, and evaluate the effects of two haemodynamic conditions on agreement. STUDY DESIGN: Prospective randomized study. ANIMALS: A group of eight horses aged 7 (4-23) years with a body weight of 493 ± 33 kg. METHODS: Horses were anaesthetized and positioned in dorsal recumbency. Invasive blood pressure was measured simultaneously via catheters placed in the facial, metatarsal and carotid arteries. Cardiovascular function and agreement between arteries was assessed before and during administration of phenylephrine and sodium nitroprusside. These were administered until carotid mean pressure (MAPc) increased or decreased from baseline (65 ± 5) to >90 or <50 mmHg, respectively. Data recorded at each sample time included systolic (SAP), mean (MAP) and diastolic (DAP) arterial pressures for carotid (c), facial (f) and metatarsal (m) arteries as well as cardiac output (Q˙t) and systemic vascular resistance (SVR). Bland-Altman analysis was used to assess agreement between peripheral and central sites, and regression analysis to determine influence of Q˙t and SVR. RESULTS: The largest difference was observed in SAPc and SAPm with a bias and limits of agreement (LOA) of 2 (-15 to 19) mmHg. The bias (LOA) for MAPc and MAPf was 2 (-4 to 9) mmHg and for MAPc and MAPm was 5 (-4 to 14) mmHg. The best agreement for DAP was seen between DAPc and DAPf with bias (LOA) of 1 (-3 to 5) mmHg. Regression analysis indicated marginal influence on agreement by Q˙t on MAPc and MAPf. CONCLUSIONS AND CLINICAL RELEVANCE: MAP and DAP of the carotid artery were higher than those of the peripheral arteries, which may lead to overzealous treatment of hypotension, albeit maintaining central pressures. Q˙t and SVR did not largely influence the difference between sites.

Agreement between invasive blood pressures measured in three peripheral arteries in anaesthetized horses under clinical conditions.

OBJECTIVE: To determine agreement between invasive blood pressures measured in three peripheral arteries in anaesthetized horses undergoing elective surgery. STUDY DESIGN: Prospective balanced incomplete block design. ANIMALS: A total of 18 client-owned horses. METHODS: Invasive blood pressure (IBP) was measured simultaneously in one of the following three combinations: 1) transverse facial and facial artery; 2) transverse facial and metatarsal artery; and 3) facial and metatarsal artery. The agreement in blood pressure measured for each combination was performed in six horses. At each sample time, systolic (SAP), mean (MAP) and diastolic (DAP) arterial pressures were measured concurrently in each artery, and the mean of three consecutive measurements was recorded. The position of horse, heart rate and use of dobutamine were also recorded. Bland-Altman analysis was used to assess agreement between sites. RESULTS: A total of 54 paired measurements were obtained, with 18 paired measurements from each combination. All paired measurements showed poor and haphazard (nonsystematic) agreement. The widest limit of agreement was 51 mmHg for SAP measured in the facial artery and metatarsal artery, with a bias of -11 mmHg. The smallest limit of agreement was 16 mmHg for MAP measured in the transverse facial and metatarsal artery, with a bias of 1 mmHg. CONCLUSIONS AND CLINICAL RELEVANCE: There was poor and haphazard agreement for SAP, MAP and DAP measured in each pair of peripheral arteries in this study. These results show that blood pressure measured in different peripheral arteries cannot be used interchangeably. This has implications for studies that use IBP as an outcome variable and studies determining agreement between noninvasive blood pressure and IBP measurements in horses under general anaesthesia.

Agreement of invasive and non-invasive blood pressure measurements in anaesthetised pigs using the Surgivet V9203.

The automated oscillometric method is a common method for measuring blood pressure non-invasively and is broadly and confidently used in the veterinary setting. Twenty-one pigs undergoing anesthesia for exploratory laparotomy were enrolled in a study to evaluate the performance of the Surgivet V9203 non-invasive blood pressure (NIBP) monitor. The aim was to compare measurements of arterial blood pressure obtained simultaneously using the Surgivet V9203 oscillometric system and an intra-arterial catheter-transducer system, both at the level of the metatarsus. Invasive blood pressure (IBP) was consistently underestimated by the non-invasive method. Bland-Altman analysis showed poor agreement between the two modalities based on evaluation of mean bias and 95% limits of agreement. The Surgivet V9203 cannot therefore be recommended as a reliable alternative to invasive blood pressure monitoring in anaesthetised pigs. As pulse detection is one of the most important factors affecting NIBP accuracy it is likely that our findings may reflect an anatomical or physiological difference in the species that alters the detection of wall movement by the oscillometric technique and additionally, makes the algorithm used by the Surgivet to determine blood pressure parameters unsuitable for use in pigs.

Paradoxical bradycardia during surgical caudal vena cava occlusion in an anesthetized dog.

OBJECTIVE: To describe the anesthetic management of a dog undergoing caudal vena cava (CVC) occlusion during adrenalectomy, and to discuss a reflex bradycardia that was observed during the procedure. CASE SUMMARY: General anesthesia of a 10-year-old Rhodesian ridgeback for excision of an adrenal mass and associated CVC tumor thrombus was performed. The dog was premedicated with IV methadone and anesthesia was induced with IV alfaxalone and maintained with isoflurane in 100% oxygen. An IV remifentanil infusion was administered for intraoperative analgesia. Surgical removal of the thrombus necessitated temporary complete occlusion of the CVC. During CVC occlusion an acute paradoxical bradycardia occurred, which was successfully treated with IV atropine. The cardiovascular change resembled a Bezold-Jarisch or reverse Bainbridge reflex, and was believed to be mediated by cardiac mechanoreceptors following the sudden decrease in preload. Increased myocardial contractility subsequent to increased sympathetic nervous system activity may also have contributed. A decrease in urine output was observed following CVC occlusion but had returned to normal 2 hours following the end of anesthesia. Recovery from anesthesia was otherwise uneventful. NEW OR UNIQUE INFORMATION PROVIDED: Although the mechanism is unclear, a paradoxical bradycardia may occur during complete CVC occlusion in the dog. Factors that increase sympathetic nervous system outflow, such as administration of dopamine, may have contributed to the occurrence of the reflex.

Comparison of invasive and noninvasive blood pressure measurements in anaesthetized horses using the Surgivet V9203.

OBJECTIVES: To determine the bias and precision of noninvasive versus invasive blood pressure measurements obtained using the Surgivet V9203 in anaesthetized horses; to compare these with the current American College of Veterinary Internal Medicine Hypertension Consensus Panel (AHCP) and Veterinary Blood Pressure Society (VBPS) recommendations; and to investigate whether noninvasive blood pressure monitoring could be a clinically useful alternative to invasive blood pressure monitoring in anaesthetized horses. STUDY DESIGN: Prospective clinical study in a university teaching hospital. ANIMALS: Forty-three horses with an average weight of 485 ± 90 kg and a mean age of 103.4 ± 57.6 months. METHODS: Arterial blood pressure (BP) was measured noninvasively (NIBP) via a cuff placed over either the ventral coccygeal artery or the metacarpal artery, and invasively (IBP) via a catheter in either the facial artery or the metatarsal artery. A total of 143 paired readings were obtained. Comparison of measurements was carried out using the Bland-Altman method. Analysis was performed using all the data, and these data were subdivided according to the position of the horse and the magnitude of the pressure measurement. To determine the accuracy of the noninvasive measurements, the calculated precision and bias were compared with AHCP and VBPS guidelines. RESULTS: For all categories, NIBP measurements were generally lower than IBP measurements. For pooled data, the bias and precision for systolic arterial pressure (SAP) were 6.8 and 11.9 mmHg; for mean arterial pressure (MAP) the values were 1.9 and 10.0 mmHg; and for diastolic arterial pressure (DAP) they were 5.7 and 10.8 mmHg. The bias and precision for MAP and DAP measurements were within the recommended guidelines defined by the AHCP and VBPS. CONCLUSIONS AND CLINICAL RELEVANCE: These results suggests that systolic, mean and diastolic NIBP measured using the Surgivet V9203 are a clinically acceptable alternative to IBP measurements in anaesthetized horses undergoing routine elective surgeries.

Comparison of invasive versus noninvasive blood pressure measurements before and after hemorrhage in anesthetized greyhounds using the Surgivet V9203.

OBJECTIVE: To determine the agreement between blood pressure obtained with a noninvasive technique and direct technique using the Surgivet V9203 at varying blood pressure levels created using a canine hemorrhage model. DESIGN: Experimental study. SETTING: University Teaching Hospital. ANIMALS: Twenty-nine greyhounds with an average weight of 30 kg. Approval from the Murdoch University Animal Ethics Committee was obtained (R228609). METHODS: Arterial blood pressure (BP) was measured noninvasively (NIBP) via a cuff placed over the dorsal metatarsal artery and via a catheter in the contralateral dorsal metatarsal artery (IBP). Retrospectively the blood pressure measurements recorded were divided into various BP categories. A total of 84 paired readings were obtained. The data were further analyzed with respect to heart rate [<120/min and >120/min]. Comparison of the measurements was performed using the Bland-Altman method. RESULTS: For all categories, BP measurements were generally lower when recorded using the oscillometric technique [Systolic (Sys) bias 4.20 kPa (31.54 mm Hg), mean bias 0.52 kPa (3.93 mm Hg), and diastolic bias 1.04 kPa (7.83 mm Hg)]. Mean arterial BP had the least bias and greatest precision in the hypotensive group (bias 0.174 kPa (1.3063 mm Hg), precision 0.79 kPa (5.89 mm Hg)), low BP group (bias 0.62 kPa (4.67mm Hg) and precision 0.89 kPa (6.67mm Hg)) and normotensive group [bias 0.76 kPa (5.71 mm Hg) and precision 1.16 kPa (8.73 mmHg)]. CONCLUSIONS: The results demonstrate that the agreement between NIBP measurements and IBP, are within the limits of agreement recommended by the American College of Veterinary Internal Medicine Hypertension Consensus Panel for all pressures except Sys BP. This suggests that mean and diastolic NIBP using the Surgivet V9203 are a clinically acceptable alternative of IBP in hypovolemic hypotensive dogs.

Incidence of seizures associated with the use of acepromazine in dogs undergoing myelography.

OBJECTIVE: To investigate the frequency of seizures associated with acepromazine administration when used as a premedicant with methadone for dogs undergoing myelography. DESIGN: Retrospective clinical case study. SETTING: University veterinary teaching hospital. ANIMALS: Sixty-six dogs (mixed and pure breeds), aged between 4 months and 15 years, weighing between 3.5-61 kg. All animals were classified as ASA score I or II. INTERVENTIONS: Forty-three animals were premedicated with methadone (0.1-0.5 mg/kg) and acepromazine (0.01-0.05 mg/kg) intramuscularly. Twenty-three animals were premedicated with methadone alone (0.1-0.5 mg/kg) intramuscularly. Anesthesia was induced with propofol intravenously and maintained with isoflurane delivered in 100% oxygen. All animals received a balanced isotonic crystalloid solution intravenously at a rate of 10 mL/kg/h. Blood pressure, end-tidal CO(2) , oxygen saturation, respiratory rate, and heart rate were monitored throughout anesthesia. Animals requiring surgery immediately following myelography were excluded from the study. MEASUREMENTS AND MAIN RESULTS: The frequency of seizures was 14% (CI: 3.6-24.3%) and 13.0% (CI: 0.7-27%) in dogs that received methadone/acepromazine and methadone alone, respectively. There was no significant difference in the frequency of seizures between dogs receiving methadone/acepromazine or methadone alone (P = 1). Analysis of the association of site of injection of the contrast and the frequency of seizures in dogs receiving methadone/acepromazine showed no significant difference in the frequency of seizures following cervical injection (25%; CI: 0.5-24.5%) or lumbar injection (9.7%; CI: -0.7-20.1%). CONCLUSIONS: The administration of acepromazine combined with methadone as a premedicant used with propofol and isoflurane anesthesia did not significantly increase the frequency of seizures following myelography compared to dogs who received methadone alone.

Anaesthetic and surgical management of an intra-tracheal mass in a cat.

An 11-year-old, 7 kg male neutered domestic shorthair cat, presented to the University Veterinary Hospital (UVH) for investigation of chronic tachypnoea and dyspnoea. Radiographs, bronchoscopy and computerised tomography (CT) demonstrated an intra-tracheal mass measuring 13 mm × 5 mm × 6 mm arising from the right wall of the caudal trachea immediately cranial to the carina. Due to size and position, debulking and subsequent cryosurgery were attempted to minimise the amount of tissue removed and prevent recurrence. A combination of anaesthetic techniques was required to allow cryotherapy, with the trachea open whilst maintaining adequate ventilation. This case report demonstrates that cryotherapy in conjunction with anaesthetic planning, can achieve a positive outcome for the cat.