Comparison of pulse pressure variation versus echocardiography-derived stroke volume variation for prediction of fluid responsiveness in mechanically ventilated anesthetized dogs

ObjectiveTo evaluate the ability and accuracy of aortic flow velocity–time integral variation (ΔVTI) and peak aortic velocity variation (ΔVpeak) compared with pulse pressure variation (PPV) to predict fluid responsiveness in mechanically ventilated dogs.Study designProspective clinical study.AnimalsA group of 50 mechanically ventilated dogs with spontaneous hypotension during orthopedic or oncologic surgery.MethodsInvestigations were performed in the surgery room. When mean arterial pressure (MAP) decreased to <65 mmHg, measurements were performed before and after a fluid challenge (lactated Ringer’s solution 5 mL kg⁻¹ over 15 minutes). Responders were defined as a change in stroke volume (SV; transesophageal Doppler) ≥15%. Data were analyzed using paired/unpaired t test or Mann–Whitney/Wilcoxon test when appropriate and receiver operating characteristics (ROC) curves; a p value <0.05 was considered statistically significant.ResultsAfter the fluid challenge, 35 (70%) of 50 dogs were responders with significant increases in SV and decreases in PPV; 15 dogs were nonresponders. ΔVTI and ΔVpeak correlated with a 15% increase in SV. The optimum cut-off value for PPV was 15.6% (sensitivity, 88%; specificity, 100%), for ΔVTI was 10.65% (sensitivity, 65%; specificity, 100%) and for ΔVpeak was 10.15% (sensitivity, 80%; specificity, 100%). The area under the ROC curve for PPV was (0.93 ± 0.08) and for ΔVpeak was (0.89 ± 0.09), before fluid challenge. The gray zone area spread from 6.15% to 15.6% for PPV (18 dogs), 2.45% to 10.65% for ΔVTI (22 dogs) and 0.6% to 10.15% for ΔVpeak (25 dogs).ConclusionsWhen using mechanical ventilation, ΔVTI and ΔVpeak predicted fluid responsiveness with the same ability as PPV, based on the area under the ROC curve analysis. However, PPV showed great accuracy demonstrated by a narrower gray zone that included fewer individuals.Clinical relevanceΔVTI and ΔVpeak can be used as indices of fluid responsiveness in anesthetized dogs.     

Noninvasive stroke volume variation using electrical velocimetry for predicting fluid responsiveness in dogs undergoing cardiac surgery

Objective

To evaluate the ability of a noninvasive cardiac output monitoring system with electrical velocimetry (EV) for predicting fluid responsiveness in dogs undergoing cardiac surgery.

Clinical evaluation of the Surgivet V60046, a non invasive blood pressure monitor in anaesthetized dogs

OBJECTIVE: To compare the performance of the Surgivet Non-Invasive Blood Pressure (NIBP) monitor V60046 with an invasive blood pressure (IBP) technique in anaesthetized dogs. STUDY DESIGN: A prospective study. ANIMALS: Thirty-four dogs, anaesthetized for a variety of procedures. METHODS: Various anaesthetic protocols were used. Invasive blood pressure measurement was made using a catheter in the femoral or the pedal artery. A cuff was placed on the contralateral limb to allow non invasive measurements. Recordings of arterial blood pressures (ABPs) were taken at simultaneous times for a range of pressures. For analysis, three pressure levels were determined: high [systolic blood pressure (SAP) > 121 mmHg], normal (91 mmHg < SAP < 120 mmHg) and low (SAP < 90 mmHg). Comparisons between invasive and non invasive measurements were made using Bland-Altmann analysis. RESULTS: The NIBP monitor consistently underestimated blood pressure at all levels. The lowest biases and greatest precision were obtained at low and normal pressure levels for SAP and mean arterial pressure (MAP). At low blood pressure levels, the biases +/- 95% confidence interval (CI) were 1.9 +/- 2.96 mmHg (SAP), 8.3 +/- 2.41 mmHg diastolic arterial pressure (DAP) and 3.5 +/- 2.09 mmHg (MAP). At normal blood pressure levels, biases and CI were: 1.2 +/- 2.13 mmHg (SAP), 5.2 +/- 2.32 mmHg (DAP) and 2.1 +/- 1.54 mmHg (MAP). At high blood pressure levels, the biases and CI were 22.7 +/- 5.85 mmHg (SAP), 5.5 +/- 3.13 mmHg (DAP) and 9.4 +/- 3.52 mmHg (MAP). In 90.6% of cases of hypotension (MAP < 70 mmHg), the low blood pressure was correctly diagnosed by the Surgivet. CONCLUSIONS: Measurement of blood pressure with the indirect monitor allowed detection of hypotension using either SAP or MAP. The most accurate readings were determined for MAP at hypotensive and normal levels. The monitor lacked accuracy at high pressures. CLINICAL RELEVANCE: When severe challenges to the cardiovascular system are anticipated, an invasive method of recording ABP is preferable. For routine usage, the Surgivet monitor provided a reliable and safe method of NIBP monitoring in dogs, thereby contributing to the safety of anaesthesia by providing accurate information about the circulation.     

Electrical velocimetry for noninvasive cardiac output and stroke volume variation measurements in dogs undergoing cardiovascular surgery

Objective

To compare electrical velocimetry (EV) noninvasive measures of cardiac output (CO) and stroke volume variation (SVV) in dogs undergoing cardiovascular surgery with those obtained with the conventional thermodilution technique using a pulmonary artery catheter.

Vasopressin therapy in dogs with dopamine-resistant hypotension and vasodilatory shock

Objective: To describe the therapeutic use of vasopressin in dogs with dopamine‐resistant hypotension and vasodilatory shock. Series summary: We report the effects of intravenous vasopressin therapy on mean arterial blood pressure and central venous pressure (CVP) in 5 dogs with dopamine‐resistant hypotension from vasodilatory shock. All subjects had documented hypotension and vasodilation, despite adequate intravascular volume and catecholamine therapy. There was an increase in mean arterial pressure following vasopressin administration. No cardiac arrhythmias were noted, nor were there clinically significant changes in CVP. New information provided: Mean arterial blood pressure increased following vasopressin therapy in all of the dogs. Vasopressin may prove useful in the treatment of vasodilatory shock, however further research is warranted.     

Evaluation of an oscillometric blood pressure monitor for use in anesthetized sheep

ObjectiveTo determine the accuracy of an oscillometric blood pressure monitor in anesthetized sheep.Study designProspective study.AnimalsTwenty healthy adult sheep, 11 males and nine females, weighing 63.6 ± 8.6 kg.MethodsAfter premedication with buprenorphine or transdermal fentanyl, anesthesia was induced with ketamine‐midazolam and maintained with isoflurane and ketamine, 1.2 mg kg^?1 hour^?1, ± lidocaine, 3 mg kg^?1 hour^?1. Invasive blood pressure measurements were obtained from an auricular arterial catheter and noninvasive measurements were from a cuff on the metatarsus or antebrachium. Simultaneous invasive and noninvasive measurements were recorded over a range (55–111 mmHg) of mean arterial pressures (MAP). Isoflurane concentration was increased to decrease MAP and decreasing the isoflurane concentration and infusing dobutamine achieved higher pressures. Invasive and noninvasive measurements were compared.ResultsCorrelation (R²) was good between the two methods of measurement (average of three consecutive readings) for systolic (SAP) (0.87), diastolic (DAP) (0.86), and mean (0.90) arterial pressures (p < 0.001). Bias ± SD between noninvasive and invasive measurements for SAP was 3 ± 8 mmHg, for DAP was ?10 ± 7 mmHg, and MAP was ?7 ± 6 mmHg. There was no significant difference between the average of three measurements and use of the first measurement. Correlations using the first measurement were SAP (0.82), DAP (0.84), and MAP (0.89). Bias ± SD for SAP was 3 ±10 mmHg, for DAP was ?11 ± 7 mmHg, and MAP was ?7 ± 6 mmHg. The oscillometric monitor slightly overestimated SAP and underestimated DAP and MAP for both average values and the first reading.Conclusions and clinical relevanceThis oscillometric model provided MAP measurements that were acceptable by ACVIM standards. MAP measurements with this monitor were lower than those found with the invasive technique so a clinical diagnosis of hypotension may be made in sheep that are not hypotensive.     

Comparison between pulse pressure variation and systolic pressure variation measured from a peripheral artery for accurately predicting fluid responsiveness in mechanically ventilated dogs

ObjectiveTo compare pulse pressure variation (PPV) and systolic pressure variation (SPV) measured from a peripheral artery to predict fluid responsiveness in anesthetized healthy dogs.Study designProspective study.AnimalsA total of 39 dogs (13.8–26.8 kg) anesthetized with isoflurane for elective ovariohysterectomy.MethodsVentilation was controlled (tidal volume 12 mL kg^–1; 40% inspiratory pause). PPV and SPV were recorded from a dorsal pedal artery catheter using an automated algorithm. A fluid challenge (FC) with lactated Ringer’s solution (20 mL kg^–1 over 15 minutes) was administered once (21 animals) or twice (18 animals) before surgery. Increases in transpulmonary thermodilution stroke volume index > 15% from values recorded before each FC defined responders to volume expansion. Final fluid responsiveness status was based on the response to single FC or second FC. Predictive ability of PPV and SPV was compared by receiver operating characteristic (ROC) curve analysis and by the range of cut-off values associated with uncertain results (gray zone).ResultsAll animals after the single FC were responders; all animals administered two FCs were nonresponders after the second FC. The area under the ROC curve (AUROC) of PPV (0.968) did not differ from that of SPV (0.937) (p = 0.45). Best cut-off thresholds to discriminate responders from nonresponders were >11.7% (PPV) and >7.4 mmHg (SPV). The gray zone of PPV and SPV was 8.2–14.6% and 7.0–7.4 mmHg, respectively. The percentage of animals with PPV and SPV values within the gray zone was less for SPV (10.2%) than for PPV (30.8%).Conclusions and clinical relevancePPV and SPV obtained from the dorsal pedal artery are useful predictors of fluid responsiveness in dogs. Using an automated algorithm, SPV may more accurately predict fluid responsiveness than PPV, with responders identifiable by PPV > 14.6% and SPV > 7.4 mmHg.     

Validation of oscillometric blood pressure measurement using a Datex S/5 Compact multiparameter monitor in anaesthetized adult dogs

ObjectiveTo compare noninvasive (NIBP) with invasive blood pressure (IBP) measurements from a Datex S/5 Compact monitor in anaesthetized adult dogs, and to evaluate it according to the American College of Veterinary Internal Medicine (ACVIM) and the Association for the Advancement of Medical Instrumentation (AAMI) criteria.Study designProspective clinical study.AnimalsA group of 34 client-owned adult dogs.MethodsDogs were anaesthetized for different surgical procedures using different anaesthetic protocols. IBP was measured using a catheter placed in a dorsal pedal artery. A blood pressure cuff was placed over the contralateral dorsal pedal artery for NIBP measurement. Data were recorded using the Datex iCollect program, and paired readings were matched every 3 minutes for 60 minutes. Bland-Altman and error grid analyses were used to estimate the agreement between IBP and NIBP measurements, and its clinical significance, respectively. Data were reported as mean bias [lower, upper limits of agreement (LoA)].ResultsThe Datex S/5 monitor conformed to most ACVIM criteria. The correlation coefficient was less than 0.9 for systolic, diastolic, and mean arterial pressures (MAP). The best agreement between the noninvasive and invasive methods was observed for MAP, with LoA (–17 to 13 mmHg) and higher percentage of NIBP readings within 5 (55.6%), 10 (81.7%) and 20 (98.6%) mmHg of the IBP values. The Datex S/5 NIBP technology did not meet the AAMI validation criteria and less than 95% of the paired measurements were found within the green zone of the error grid analysis.Conclusions and clinical relevanceThe Datex S/5 monitor conformed to most ACVIM criteria but not with the more rigorous AAMI standards. Despite good agreement between IBP and NIBP for MAP measurements, care must be taken when using this device to guide therapeutic interventions of blood pressure in anaesthetized healthy adult dogs.     

Validity and reliability of Doppler ultrasonography and direct arterial blood pressure measurements in anaesthetized dogs weighing less than 5 kg

Objective

To assess the validity and reliability of Doppler ultrasonography (DOP) as compared with invasive arterial blood pressure measurements in anaesthetized dogs weighing less than 5 kg.

Effect of ephedrine and phenylephrine on cardiopulmonary parameters in horses undergoing elective surgery

ObjectiveTo assess the cardiopulmonary effects of ephedrine and phenylephrine for management of isoflurane‐induced hypotension in horses.Study designProspective randomized clinical study.AnimalsFourteen isoflurane‐anesthetized horses undergoing digital palmar neurectomy.MethodsEphedrine (EPH group; 0.02 mg kg^?1 minute^?1; n = 7) or phenylephrine (PHE group; 0.002 mg kg^?1 minute^?1; n = 7) was administered to all horses when mean arterial pressure (MAP) was <60 mmHg. The infusions were ended when the target MAP was achieved, corresponding to a 50% increase over the pre‐infusion MAP (baseline). The horses were instrumented with an arterial catheter to measure blood pressure and allow the collection of blood for pH and blood‐gas analysis and a Swan‐Ganz catheter for measurement of cardiac output using thermodilution. Cardiopulmonary parameters were recorded at baseline and at 5, 30, 60 and 90 minutes after achieving the target MAP.ResultsIn both groups, the MAP and systemic vascular resistance (SVR) increased significantly at 5, 30, 60 and 90 minutes post infusion compared to baseline (p < 0.05). The EPH group had a significant increase in cardiac index (CI) and systemic oxygen delivery index at 5, 30, 60 and 90 minutes post infusion compared to baseline (p < 0.05) and compared to the PHE group (p < 0.05). The PHE group had significantly higher SVR and no decrease in oxygen extraction compared with the EPH group at 30, 60 and 90 minutes post infusion (p < 0.05). No significant differences in ventilatory parameters were observed between groups after the infusion.ConclusionsEphedrine increased the MAP by increasing CI and SVR. Phenylephrine increased MAP by increasing SVR but cardiac index decreased. Ephedrine resulted in better tissue oxygenation than phenylephrine.Clinical relevanceEphedrine would be preferable to phenylephrine to treat isoflurane‐induced hypotension in horses since it increases blood flow and pressure.     

A clinical comparison between a non‐invasive blood pressure monitor using high definition oscillometry (Memodiagnostic MD 15/90 Pro) and invasive arterial blood pressure measurement in anaesthetized dogs

ObjectiveTo compare high definition oscillometry (HDO) to invasive blood pressure measurement in anaesthetized dogs.Study designProspective, clinical trial.AnimalsFifty dogs weighing 1.95–79 kg (mean 23.5 kg).Materials and methodsAnaesthetic and peri–anaesthetic management was chosen according to each dog's physical status and anaesthetist's preference. Direct arterial blood pressure measurements were performed using a catheter placed in the dorsal pedal artery and an electronic pressure transducer connected to a multiparameter monitor. Non–invasive blood pressure measurements were performed using an appropriately sized cuff placed around the tail base. Comparisons between the two methods were made using Bland and Altman plots. The data are reported as mean bias (lower, upper limits of agreement). Further analysis was performed after separating the data into the following categories based on invasive mean arterial blood pressure (MAP): high (MAP > 100 mmHg), medium (70 mmHg < MAP < 100 mmHg) and low (MAP < 70 mmHg) blood pressure (BP). The two methods were compared as used clinically.ResultsEight hundred measurement pairs for invasive and HDO BP readings were compared. Overall, the HDO measured lower values for SAP and DAP but higher for MAP than the invasive method. The lowest bias (upper, lower limits of agreement) were obtained for MAP, ?1 (?22, 19) mmHg. The biggest discrepancy between the methods was reflected by a large bias (limits of agreement) 5 (?34, 45) mmHg, was for SAP. The results for DAP were between those for SAP and MAP with a bias (limits of agreement) of 3 (?20, 27) mmHg. When the values were separated into the pressure range categories the HDO measured higher in the high, medium and low BP groups, with the exception of SAP in the low BP group.ConclusionsWhen considering the mean bias, the accuracy of HDO compared well with direct arterial blood pressure, but the precision was poor, as determined by wide limits of agreement.Clinical relevanceUsing trends and serial measurements rather than a single measurement for clinical decision making is recommended with both methods, when used as reported here.     

Indirect measurement of blood pressure using a pulse oximeter in isoflurane anesthetized dogs

Objective: To determine the accuracy of indirect blood pressure (BP) measurements obtained with a pulse oximeter as compared with direct measurements in dogs under isoflurane anesthesia. The Doppler and oscillometric BP monitors were included for comparison. Design: Prospective, experimental study. Animals: Twenty healthy dogs (23 ± 8 kg) anesthetized for research or teaching. Interventions: Dogs were anesthetized with propofol or thiopental and maintained using positive pressure ventilation with isoflurane in 100% O₂. Random adjustment of BP was achieved by inhalant adjustment or dopamine infusion to achieve low (≤85 mmHg), normal (90–120 mmHg), or high systolic BP (≥125 mmHg). Triplicate measurements for BP were taken with direct (dorsal pedal artery), Doppler (forelimb), oscillometric (same forelimb), and plethysmographic (pulse oximeter on tongue) methods. Measurements and main results: Using regression analysis and a modified Bland–Altman's technique, the lowest bias was achieved with the Doppler. Systolic BP readings at low, normal, and high BP were within 10 mmHg of direct recordings 95%, 70%, and 30% of the time for pulse oximetry; 95%, 85%, and 55% of the time for Doppler; 42%, 65%, and 30% of the time for oscillometric determination, respectively. Oscillometric mean BP readings were within 10 mmHg of direct measurements 53%, 60%, and 45% of the time, respectively. Conclusions: The pulse oximeter is an acceptable method for measuring BP in anesthetized dogs if assessment of trends is sufficient. All indirect methods showed greater bias and poorer precision at high BP. The Doppler may be the preferred indirect method.     

Evaluation of a new oscillometric blood pressure monitor in isoflurane-anesthetized dogs

Objective This study was conducted to evaluate the performance of a new veterinary oscillometric noninvasive blood pressure (NIBP) monitor in anesthetized dogs. Study design Assessment was made to determine how closely indirect measurements were associated with direct measurements, and if there were statistically significant differences between the measurements by site. Animals Six mongrel dogs weighing 27.8 ± 2.9 kg. Methods Dogs were anesthetized with thiopental and maintained with isoflurane, which was delivered with controlled ventilation. Direct pressure measurements were obtained via a percutaneously placed arterial catheter. A range of systolic arterial pressures (SAP) were achieved by changing the isoflurane concentrations. Sites of cuff placement for indirect measurements were identified as metacarpus, metatarsus, and anterior tibial. Results At pressures below 80 mm Hg, indirect systolic measurements averaged 4 ± 3 mm Hg, higher than the direct values. At normal and high levels, indirect systolic measurements underestimated direct values by 18 ± 6 and 23 ± 6 mm Hg, respectively. Diastolic and mean pressure measurements followed the same trend, with indirect values being lower than the direct arterial pressures. Systolic, diastolic and mean arterial pressure measurements differed by cuff‐placement site. Conclusions When analyzed by site and level, indirect systolic and mean arterial blood pressures during hypotension were essentially the same as direct pressures. However, at pressures within the normal or high range, indirect measurements underestimated the direct pressures. Clinical relevance Noninvasive blood pressure measurements with a new oscillometric monitor provided an excellent means of detecting arterial hypotension in anesthetized dogs. The metatarsal site for cuff placement was slightly better than the metacarpal or anterior tibial site, considering that the regression line was closest to complete equality between the indirect and direct measurements for SAP.     

Effects of topical nipradilol and timolol maleate on intraocular pressure, facility of outflow, arterial blood pressure and pulse rate in dogs

Nipradilol is an alpha(1), beta-blocker with milder side effects than other beta-blockers used in humans. In this study the effects of nipradilol were compared with those of timolol maleate in dogs. Twelve clinically normal dogs (nine mongrels, two beagles, and one Akita) were used. We applied 0.25% nipradilol or 0.5% timolol maleate drops for a period of 28 days. Intraocular pressure (IOP) was measured before and after administration on the 2nd, 4th, 7th, 14th, 21st and 28th day. Blood pressure, pulse rate and coefficient of aqueous outflow (C-value) were also measured before and after administration on the 7th, 14th, 21st and 28th day. Both nipradilol and timolol maleate significantly lowered IOP from the 2nd day to the end of the study period. Nipradilol lowered IOP to an equivalent degree to timolol maleate. There was no significant change in blood pressure and pulse rate throughout the study period with administration of nipradilol. C-value showed a significant rise from the 14th day with administration of nipradilol, while it did not show any significant change during the study period with administration of timolol maleate. The reduction of IOP by nipradilol was similar to that by an existing beta-adrenergic antagonist, timolol maleate, but nipradilol was associated with fewer systemic side effects in dogs. Nipradilol appears to be a useful drug for treatment of glaucoma in dogs.     

Acid‐base and electrolyte balance following administration of three crystalloid solutions in dogs undergoing elective orthopaedic surgery

ObjectiveTo compare acid–base balance and incidence of hyperchloraemic metabolic acidosis following administration of three crystalloid solutions to dogs undergoing anaesthesia for orthopaedic surgery.Study designProspective, randomised, clinical study.AnimalsSixty dogs.MethodsDuring a non–standardised anaesthetic, 0.9% saline (S), Hartmann's solution (H) or a polyionic glucose–free maintenance solution (M) was administered IV at 10 mL kg^?1 hour^?1. Venous blood pH, PCO₂, PCV, total protein, urea, sodium, potassium and chloride concentrations were measured at induction of anaesthesia (T0) and after 2 hours of fluid therapy (T2). Base excess (BE), bicarbonate, corrected chloride concentration (corrCl), osmolality, change in plasma volume (PV) and strong ion gap (SIG) were calculated. Changes in variables within groups (1–sample Student's t–test/Wilcoxon signed rank test) and between groups (1–way anova/Kruskal–Wallis) were assessed. Data are presented as median (interquartile range). Significance was set at p < 0.05.ResultsNo significant differences existed between groups for pH, PCO₂, PCV, total protein, urea, potassium, corrCl, PV and SIG. Potassium significantly increased in all groups. Significant differences existed between groups S and M for BE, sodium, chloride, bicarbonate and osmolality, and between groups H and M for sodium and osmolality. Chloride concentration significantly changed from 116 (114–117) to 117 (116–119) mmol L^?1 in group S, 116 (115–118) to 115 (113–117) mmol L^?1 in group H and 116 (115–118) to 114 (113–118) mmol L^?1 in group M. In groups H and M, sodium and osmolality decreased, and BE and bicarbonate concentration increased significantly. Plasma volume increased by 28 (14–44)%, 25 (5–40)% and 24 (13–33)% in groups S, H and M, respectively.Conclusion and clinical relevanceHyperchloraemic metabolic acidosis did not develop after intraoperative 0.9% saline, Hartmann's solution or maintenance solution at 10 mL kg^?1 hour^?1 for 2 hours in dogs undergoing elective orthopaedic surgery. Bicarbonate and BE increased after Hartmann's and maintenance solutions. Increases in potassium concentration were unexplained.