Carsten Bandt

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.

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.

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.

Determination of cardiac output in neonatal foals by ultrasound velocity dilution and its comparison to the lithium dilution method.

OBJECTIVE To compare cardiac output (CO) measured by use of lithium dilution (LiDCO) and ultrasound velocity dilution (UDCO) in conditions of high, intermediate, and low CO in anesthetized foals. DESIGN Original prospective study. SETTING University teaching hospital. ANIMALS Six foals 1-3 days of age (38-45 kg). INTERVENTIONS Neonatal foals 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 foal at baseline and during low, intermediate, and high CO states. Measurements were converted to cardiac index (cardiac index=CO/body weight) values for statistical analysis. Agreement between the 2 methods was determined using Bland and Altman analysis and concordance correlation coefficients. MEASUREMENTS AND MAIN RESULTS LiDCO determinations of CO ranged between 4.0 and 14.0 L/min resulting in cardiac index ranging between 75.5 and 310 mL/kg/min. There was no significant effect of blood pressure variation on bias or relative bias (P=0.62 and 0.93, respectively). The mean bias and relative bias of UDCO (+/-SD) compared with LiDCO were -20.1+/-39.2 mL/kg/min and -7.7+/-23.4%, respectively. Concordance correlation coefficient between LiDCO and UDCO was 0.833. CONCLUSIONS When compared with LiDCO, the UDCO technique has acceptable clinical utility for measuring CO in healthy anesthetized newborn foals.

Use of IV Lipid Emulsion for Treatment of Ivermectin Toxicosis in a Cat

Ivermectin toxicosis in cats is infrequently reported. IV lipid emulsion (ILE) is a novel treatment in veterinary medicine that has been used for amelioration of adverse effects seen with multiple lipid soluble compounds. Previously, ILE has been investigated in experimental models with rats, rabbits, pigs, and dogs, mainly for resuscitation of cardiopulmonary arrest and treatment of hypotension due to local anesthetic drug overdose. There are few case reports in veterinary medicine of using ILE for drug toxicity. Only one feline case has been reported, with IV lipids used for treatment of lidocaine toxicity. This report describes a case of ivermectin toxicosis in a 1 yr old domestic shorthair that was safely and successfully treated using ILE.

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.

Evaluation of tissue oxygen saturation with near-infrared spectroscopy during experimental acute hemorrhagic shock and resuscitation in dogs

OBJECTIVE To evaluate tissue oxygen saturation (Sto2) by use of near-infrared spectroscopy in experimental acute hemorrhagic shock and resuscitation in dogs. ANIMALS 14 healthy adult purpose-bred Beagles. PROCEDURES Dogs were anesthetized with isoflurane via facemask, anesthesia was maintained with propofol and rocuronium bromide, and dogs were mechanically ventilated to maintain normocapnia. Dogs were studied under normovolemia (baseline), hypovolemia with target mean arterial blood pressure < 40 mm Hg achieved and maintained steady for 10 minutes (hypovolemia T1), then 20 minutes later (hypovolemia T2), following resuscitation with shed blood (after transfusion), and after administration of 20 mL of hetastarch/kg (hypervolemia). Conditions were executed sequentially during a single anesthetic episode, allowing stabilization between states (10 minutes). Hemoglobin concentration, mean arterial blood pressure, arterial blood gas concentrations, cardiac index, oxygen delivery indexed to body surface area, and Sto2 were monitored. RESULTS From baseline to hypovolemia T1, there was a significant reduction in mean ± SD oxygen delivery index (619 ± 257 mL/min/m(2) to 205 ± 76 mL/min/m(2)) and Sto2 (94 ± 4.4% to 78 ± 12.2%). Following resuscitation, Sto2 (80 ± 8.5% vs 92 ± 6.45%) and oxygen delivery index (211 ± 73 mL/min/m(2) vs 717 ± 221 mL/min/m(2)) significantly increased, returning to baseline values. Hypervolemia had no effect on Sto2 or oxygen delivery index. A strong correlation (r = 0.97) was detected between mean oxygen delivery index and Sto2 across all time points. CONCLUSIONS AND CLINICAL RELEVANCE Under the conditions of this study, there was a strong correlation between Sto2 and oxygen delivery, suggesting that Sto2 may be used to estimate oxygen delivery.

The effect of using an impedance threshold device on hemodynamic parameters during cardiopulmonary resuscitation in dogs

OBJECTIVE To investigate the hemodynamic effects following the use of an impedance threshold device (ITD) in a canine model of cardiopulmonary arrest. DESIGN Experimental, randomized crossover study. SETTING Cardiovascular research laboratory at a university veterinary center. ANIMALS Eight purpose bred beagle dogs. INTERVENTIONS Dogs were anesthetized and instrumented for the measurement of right atrial pressure , systolic blood pressure, mean blood pressure, and diastolic arterial blood pressure, end-tidal CO(2) , and carotid blood flow (CBF). CBF was determined via ultrasonic flow probe placed around the carotid artery. Animals were taking part in an unassociated terminal study and following subsequent euthanasia with pentobarbital, standardized cardiopulmonary resuscitation (CPR) was performed with an impedance threshold device attached (ITD-CPR group) and without (S-CPR group). Order of treatment was randomized. MEASUREMENTS AND MAIN RESULTS ITD group had increased CBF, coronary perfusion pressure, and a decrease in right atrial diastolic pressure. No differences in end-tidal CO(2) , diastolic arterial blood pressure, mean blood pressure, or systolic blood pressure were seen. Return of spontaneous circulation was not observed in any of the animals CONCLUSIONS Use of the ITD resulted in favorable changes in hemodynamic parameters in dogs undergoing CPR. The ITD may be a useful adjunct during CPR in dogs and warrants clinical evaluation.Objective To investigate the hemodynamic effects following the use of an impedance threshold device (ITD) in a canine model of cardiopulmonary arrest. Design Experimental, randomized crossover study. Setting Cardiovascular research laboratory at a university veterinary center. Animals Eight purpose bred beagle dogs. Interventions Dogs were anesthetized and instrumented for the measurement of right atrial pressure , systolic blood pressure, mean blood pressure, and diastolic arterial blood pressure, end-tidal CO2, and carotid blood flow (CBF). CBF was determined via ultrasonic flow probe placed around the carotid artery. Animals were taking part in an unassociated terminal study and following subsequent euthanasia with pentobarbital, standardized cardiopulmonary resuscitation (CPR) was performed with an impedance threshold device attached (ITD-CPR group) and without (S-CPR group). Order of treatment was randomized. Measurements and Main Results ITD group had increased CBF, coronary perfusion pressure, and a decrease in right atrial diastolic pressure. No differences in end-tidal CO2, diastolic arterial blood pressure, mean blood pressure, or systolic blood pressure were seen. Return of spontaneous circulation was not observed in any of the animals Conclusions Use of the ITD resulted in favorable changes in hemodynamic parameters in dogs undergoing CPR. The ITD may be a useful adjunct during CPR in dogs and warrants clinical evaluation.

Establishment of reference values for various coagulation tests in healthy Florida manatees (Trichechus manatus latirostris) and evaluation of coagulation in debilitated manatees during rehabilitation

OBJECTIVE To establish reference ranges for coagulation parameters in healthy Florida manatees (Trichechus manatus latirostris) and compare results with those for debilitated manatees undergoing treatment at a rehabilitation facility. DESIGN Prospective study. ANIMALS 29 healthy manatees and 45 debilitated manatees with various diseases. PROCEDURES Manatees considered healthy on the basis of results of physical examination, CBC, and serum biochemical analysis underwent coagulation testing including measurement of prothrombin time, partial thromboplastin time, D-dimer concentration, platelet count, and fibrinogen concentration to establish reference ranges. For comparison, a group of manatees undergoing rehabilitation was also tested, and the results were compared. Thromboelastography was also performed on some animals. RESULTS Values for D-dimer concentration were significantly higher in debilitated versus healthy animals. There was no significant difference for prothrombin time, partial thromboplastin time, platelet count, or fibrinogen concentration between groups. Thromboelastography was performed on 8 healthy animals. CONCLUSIONS AND CLINICAL RELEVANCE Reference ranges were established for various tests of coagulation that may assist clinicians during the initial evaluation and rehabilitation of Florida manatees. Future research to evaluate the effect of specific disease processes on the coagulation cascade is recommended.