Alessio Vigani

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.

Cardiopulmonary effects of a new inspiratory impedance threshold device in anesthetized hypotensive dogs.

OBJECTIVE To compare the hemodynamic and respiratory effects of an inspiratory impedance threshold device (ITD) in anesthetized normotensive and hypotensive dogs. STUDY DESIGN Prospective randomized study. ANIMALS Ten adult dogs. METHODS Dogs were anesthetized with propofol followed by isoflurane. During spontaneous ventilation, tidal volume (.VT), systolic (SAP), mean (MAP) and diastolic arterial blood pressure, central venous pressure, gastric PCO(2) as an indicator of gastric perfusion, subcutaneous oxygen tension, subcutaneous blood flow, cardiac index (CI), systemic vascular resistance and blood lactate were monitored. To monitor respiratory compliance (RC) and resistance (ResR), animals were briefly placed on mechanical ventilation. Dogs were studied under four different conditions: 1) normotension (MAP > 60 mmHg) with and without the ITD and 2) hypotension (target MAP = 40 mmHg) with and without ITD. These four conditions were performed during one anesthetic period, allowing for stabilization of parameters for each condition. Data were analyzed by anova repeated measure mixed models. RESULTS No cardiovascular changes were detected between no ITD and ITD in the normotensive state. During hypotension, CI was higher with the ITD (5 +/- 1.0 L minute(-1) m(-2)) compared with no ITD (4 +/- 1.3 L minute(-1) m(-2)). During hypotension, SAP was increased with ITD (80 +/- 14 mmHg) versus without ITD (67 +/- 13 mmHg). There was an increase in ResR and decreased RC with the ITD in both normotensive and hypotensive state. CONCLUSION AND CLINICAL RELEVANCE Impedance threshold device in dogs during isoflurane-induced hypotension improved CI and SAP but had negative effects on RC and ResR.

Anesthesia and Analgesia for Standing Equine Surgery

Morbidity and mortality rate in equine anesthesia is still unacceptably high. Thus it is critical contemplating whether the benefit of general anesthesia for a specific patient and procedure outweighs the risks. Sedative protocols that would allow performing diagnostic and surgical procedures with the patient remaining standing would therefore be ideal. Infusion of short-acting agents allows to rapidly achieve a titratable steady state of sedation. Supplementing sedatives and tranquilizers with systemic analgesic or regional anesthetic techniques (i.e. epidurals) facilitates standing surgical procedures. Multimodal analgesia would also provide superior analgesia with potentially fewer side effects than a single agent approach.

Single-incision, multicannulated, laparoscopic ovariectomy in two tigers (Panthera tigris)

Two tigers (Panthera tigris), six and seven years old, presented for laparoscopic ovariectomy. The tigers were privately owned and had never been bred. Both animals had been receiving 375 mg medroxyprogesterone acetatea intramuscularly every 6 months for contraception.

Quantitative response of volumetric variables measured by a new ultrasound dilution method in a juvenile model of hemorrhagic shock and resuscitation

OBJECTIVE New volumetric variables of preload, such as total end-diastolic volume index (TEDVI) and active circulation volume index (ACVI) and central blood volume index (CBVI), may represent good indicators of preload and predictors of fluid responsiveness. During acute changes of intravascular volume these variables would allow a more accurate intervention. AIM The aim of the present study was to investigate the changes in TEDVI, ACVI, CBVI in a juvenile model of hemorrhagic shock and resuscitation. METHODS Twelve anaesthetized ponies (3-8 months of age) were studied at normovolaemia (BASE), after blood withdrawal to mean arterial pressure (MAP) of 40 mmHg (HEMO), after infusion of norepinephrine to reach a MAP of ± 10% of baseline (HE-NE), and after retransfusion of shed blood (RESU). TEDVI, ACVI, CBVI were measured by Ultrasound Dilution (UD) technology with CoStatus device. Data were analyzed using 1-way (ANOVA) followed by Bonferronis multiple pairwise comparisons. Evaluation of dependence between CoStatus volumetric variables and stroke volume index (SVI) were performed using the linear regression analysis and calculating the r(2) coefficient of determination. RESULTS TEDVI and ACVI changed significantly during HEMO and RESU status. NE administration induced MAP and CVP significant changes, whereas TEDVI and ACVI remained unchanged. CBVI showed high variability and seemed to be inconsistent on the identification of the volume status. In the correlation analysis, only TEDVI consistently correlated with SVI and volume induced SVI changes. CONCLUSIONS In this animal model, TEDVI and ACVI were superior to CBVI in consistently reflecting hemorrhage. TEDVI but not ACVI and CBVI correlated with volume-induced changes in SVI. NE administration did not affect this correlation.

Determination of cardiac output by ultrasound velocity dilution in normovolemia and hypovolemia in dogs.

OBJECTIVE The purpose of this study was to compare CO measured by use of lithium dilution (LiDCO) and ultrasound velocity dilution (UDCO) in a canine model of acute hemorrhage. STUDY DESIGN Prospective descriptive evaluation. ANIMALS Twelve dogs (15-34 kg). METHODS Dogs were anesthetized and instrumented to measure direct blood pressure, heart rate, arterial blood gases and CO. The CO was measured by use of LiDCO and UDCO techniques. Measurements were obtained from each animal at baseline and during a low CO state (hemorrhagic state). Measurements were converted to cardiac index (CI = CO/BSA) values for statistical analysis. To measure CO using UDCO, a 20 mL bolus of 0.9% sodium chloride was administered and CO was calculated from the transient dilution of blood proteins created by the injection bolus. Hypovolemia was induced by withdrawing 40% of the blood volume until the mean arterial blood pressure (MAP) was stable at 40 mmHg for 10 minutes. Agreement was determined using Bland & Altman analysis and concordance correlation coefficients. RESULTS Twenty-four comparisons were made. Lithium determinations of CI ranged between 7.5 and 1.3 L minute(-1) m(-2), and the mean overall difference between the two methods was -0.40 L minute(-1) m(-2). The mean relative bias was -17 ± 21% (limits of agreements: -59% to 25%). There was no significant effect of state of CI on bias or relative bias (p = 0.24 and p = 0.10, respectively). The concordance correlation coefficient between LiDCO and UDCO as 0.88 (p < 0.0001). CONCLUSIONS When compared to lithium dilution, the UDCO technique is a viable method for measuring cardiac output in a model of normovolemia and hypovolemia in dogs.

Cardiopulmonary effects of a new inspiratory impedance threshold device in acute hemorrhagic shock in dogs

OBJECTIVE To compare cardiovascular and respiratory effects of an inspiratory impedance threshold device (ITD) in dogs before and after induction of acute hemorrhagic shock. STUDY DESIGN Prospective experimental randomized study. ANIMALS Eight healthy adult dogs. METHODS Dogs were anesthetized and maintained on spontaneous ventilation. Tidal volume (V(T)), systolic, mean and diastolic arterial blood pressure (SAP, MAP, DAP), central venous pressure (CVP), gastric P(CO2) (GBF) as an indicator of gastric perfusion, cardiac index (CI), systemic vascular resistance (SVR), oxygen delivery (DO(2)), and plasma lactate were monitored. To monitor respiratory compliance (RC) and respiratory resistance (ResR), animals were briefly placed on mechanical ventilation. Dogs were studied under 4 different conditions: (1) baseline (euvolemic state) (MAP > 60 mm Hg) with and without the ITD and (2) acute hemorrhagic shock (hypovolemic state) (target MAP of 40 mm Hg) with and without ITD. These 4 conditions were performed during one anesthetic period, allowing time for stabilization of parameters for each condition. Data were analyzed by ANOVA for repeated measure mixed models. RESULTS No cardiovascular changes were detected between groups with and without use of ITD during euvolemic states. During acute hemorrhagic hypovolemic state, CI and DO(2) were higher with the ITD (2.9 ± 0.6 L/min/m(2)) and (326.5 ± 86.8 mL/min) compared with no ITD (1.8 ± 0.6 L/min/m(2)) and (191.3 ± 58.1 mL/min), respectively. The use of ITD during hypovolemia also increased SAP and MAP. There was an increase in ResR and decreased RC with the ITD in both euvolemic and hypovolemic states. CONCLUSION AND CLINICAL RELEVANCE The use of an ITD in dogs during acute hemorrhagic hypovolemic shock improved cardiovascular parameters but had negative effects on RC and ResR.

Comparison of cardiac output determined by an ultrasound velocity dilution cardiac output method and by the lithium dilution cardiac output method in juvenile horses with experimentally induced hypovolemia

OBJECTIVE To assess the accuracy of an ultrasound velocity dilution cardiac output (UDCO) method, compared with that of the lithium dilution cardiac output (LiDCO) method, for determination of cardiac output (CO) in juvenile horses with experimentally induced hypovolemia. ANIMALS 12 anesthetized 2- to 6-month-old horses. PROCEDURES For each anesthetized horse, CO was determined by the LiDCO and UDCO methods prior to any intervention (baseline state), after withdrawal of approximately 40% of the horses blood volume (low CO state), after maintenance of hypovolemia and infusion of norepinephrine until mean arterial blood pressure was equal to baseline value (high CO state), and after further infusion of norepinephrine and back-transfusion of withdrawn blood (posttransfusion state). For each of the 4 hemodynamic situations, CO and calculated cardiac index (CI) values were obtained by each method in duplicate (8 pairs of measurements/horse); mean values for each horse and overall mean values across all horses were calculated. Agreement between CI determined by each method (96 paired values) was assessed by Bland-Altman analysis. RESULTS For the UDCO method-derived CI measurements among the 12 horses, mean ± SD bias was -4 ± 11.3 mL/kg/min (95% limits of agreement, -26.1 to 18.2 mL/kg/min) and mean relative bias was -10.4 ± 21.5% (95% limits of agreement, -52.6% to 31.8%). CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that, compared with the LiDCO method, the UDCO method has acceptable clinical usefulness for determination of CO in foals.

Computed tomography angiography of coarctation of the aorta in a dog

Coarctation of the aorta has been described previously as either a post-mortem or angiographic finding in three dogs with clinical signs related to the aortic coarctation. A 10-year-old dog was presented for evaluation of suspected laryngeal paralysis. On physical examination, femoral pulses were absent bilaterally, with an indirect systolic blood pressure difference of 60 mmHg between the ipsilateral thoracic and pelvic limbs. Coarctation of the aorta was detected on a thoracic computed tomographic angiography study. The coarctation was pre-ductal in position, with extensive dilation of the descending thoracic aorta. Characteristic rib changes that are seen in humans with coarctation were not apparent in this dog. 3D reconstructions of the thorax provided high vascular definition with exact localization of the aortic narrowing.

Cardiopulmonary effects of a new inspiratory impedance threshold device in acute hemorrhagic shock in dogs: Impedance threshold device for hemorrhagic shock

OBJECTIVE To compare cardiovascular and respiratory effects of an inspiratory impedance threshold device (ITD) in dogs before and after induction of acute hemorrhagic shock. STUDY DESIGN Prospective experimental randomized study. ANIMALS Eight healthy adult dogs. METHODS Dogs were anesthetized and maintained on spontaneous ventilation. Tidal volume (V(T)), systolic, mean and diastolic arterial blood pressure (SAP, MAP, DAP), central venous pressure (CVP), gastric P(CO2) (GBF) as an indicator of gastric perfusion, cardiac index (CI), systemic vascular resistance (SVR), oxygen delivery (DO(2)), and plasma lactate were monitored. To monitor respiratory compliance (RC) and respiratory resistance (ResR), animals were briefly placed on mechanical ventilation. Dogs were studied under 4 different conditions: (1) baseline (euvolemic state) (MAP > 60 mm Hg) with and without the ITD and (2) acute hemorrhagic shock (hypovolemic state) (target MAP of 40 mm Hg) with and without ITD. These 4 conditions were performed during one anesthetic period, allowing time for stabilization of parameters for each condition. Data were analyzed by ANOVA for repeated measure mixed models. RESULTS No cardiovascular changes were detected between groups with and without use of ITD during euvolemic states. During acute hemorrhagic hypovolemic state, CI and DO(2) were higher with the ITD (2.9 ± 0.6 L/min/m(2)) and (326.5 ± 86.8 mL/min) compared with no ITD (1.8 ± 0.6 L/min/m(2)) and (191.3 ± 58.1 mL/min), respectively. The use of ITD during hypovolemia also increased SAP and MAP. There was an increase in ResR and decreased RC with the ITD in both euvolemic and hypovolemic states. CONCLUSION AND CLINICAL RELEVANCE The use of an ITD in dogs during acute hemorrhagic hypovolemic shock improved cardiovascular parameters but had negative effects on RC and ResR.