Dobutamine Requirements Research Articles

Retrospective study of the changes in dynamic compliance and ventilation/perfusion mismatch following salbutamol inhalation in hypoxaemic mechanically ventilated anaesthetized horses

ObjectiveTo study the changes in dynamic compliance (Cdyn), ventilation/perfusion (V˙/ Q˙) mismatch and haemodynamic variables in hypoxaemic anaesthetized horses whose PaO2 increased following salbutamol inhalation. Study designRetrospective, clinical, cohort study. AnimalsA group of 73 client-owned horses treated with salbutamol when PaO2 <100 mmHg (13.3 kPa) during anaesthesia. MethodsHorses were divided into two groups: responders (R), where PaO2 after salbutamol ≥1.2 PaO2 before treatment (i.e. ≥20% increase), and non-responders (NR), where PaO2 after salbutamol <1.2 PaO2 before treatment. Demographic data and intraoperative variables before treatment were compared between R and NR. Cdyn, arterial to end-tidal carbon dioxide difference [P(a-E´)CO2], estimated ratio of dead space to tidal volume (est.VD/VT), estimated shunt fraction (F-shunt), heart rate, systolic, mean and diastolic arterial pressure and dobutamine requirements were compared before and after treatment within R and NR. For each variable, the difference (Δ) between values pre- and posttreatment was calculated and compared between groups R and NR. Numerical data were compared using univariate or bivariate analysis and categorical data were compared using chi-square test; p < 0.05. ResultsOf the 73 horses 50 were classified as R while 23 horses were classified as NR. There was no statistical difference between R and NR for demographic data or initial intraoperative variables except for body weight [R: 531 (170–715) kg, NR: 540 (420–914) kg]. While salbutamol did not alter Cdyn in either group, it significantly decreased P(a-E´)CO2, est.VD/VT and F-shunt in R only. ΔP(a-E´)CO2, Δest.VD/VT and ΔF-shunt were significantly greater in R (−17.8%, −19.0% and −24.1%, respectively) than in NR (11.5%, 6.6% and −0.3%, respectively). Conclusions and clinical relevanceIn hypoxaemic anaesthetized horses responding to inhaled salbutamol by a ≥1.2 increase in PaO2 no change in Cdyn was detected, but indicators of V˙/ Q˙ mismatch improved.

Hemofiltration Improves Blood Perfusate Conditions Leading to Improved Ex Situ Heart Perfusion.

The aim was to optimize the perfusate composition by including a hemofiltrator to the PhysioHeartplatform for ex situ heart perfusion of porcine slaughterhouse hearts. Fourteen hearts were harvested from Dutch Landrace pigs and slaughtered for human consumption. All hearts were preserved for 4 hours using static cold storage before reperfusion for 4 hours on the PhysioHeart platform. Seven hearts were assigned to the hemofiltration group, where a hemofiltrator was added to the perfusion circuit, while the control group did not receive hemofiltration. In the hemofiltration group, the perfusion fluid was filtrated for 1 hour with a flow of 1 L/hour before reperfusion. After mounting the heart, hemofiltration was maintained at 1 L/hour, and cardiac function and blood samples were analyzed at multiple time points. Preserved cardiac function was defined as a cardiac output >3.0 L/min with a mean aortic pressure >60 mm Hg and a left atrial pressure <15 mm Hg. Hemofiltration resulted in a significantly reduced potassium concentration at all time points ( p < 0.001), while sodium levels remained at baseline values ( p < 0.004). Furthermore, creatinine and ammonia levels decreased over time. Functional assessment demonstrated a reduced left atrial pressure ( p < 0.04) and a reduction of the required dobutamine dose to support myocardial function ( p < 0.003) in the hemofiltration group. Preserved cardiac function did not differ between groups. Hemofiltration results in an improved biochemical composition of the whole blood perfusate and preserves cardiac function better during normothermic perfusion based on a reduced left atrial pressure (LAP) and dobutamine requirement to support function.

Xylazine Infusion during Equine Colic Anesthesia with Isoflurane and Lidocaine: A Retrospective Study.

This retrospective study investigated the effect of a xylazine infusion on heart rate; mean arterial pressure; blood gases; anesthetic and dobutamine requirements; recovery quality and duration; percentage of death/survival; and days to die/discharge in horses after colic surgery under partial intravenous anesthesia with isoflurane and lidocaine infusion. Anesthetic records of equine colic surgery were reviewed from similar periods in 2020-2021 and 2021-2022. In both groups, after sedation with xylazine 0.7 mg/kg intravenously (IV) and induction with ketamine 2.2 mg/kg and midazolam 0.06 mg/kg IV, anesthesia was maintained with isoflurane and lidocaine (bolus 1.5 mg/kg IV, infusion 2 mg/kg/h). Group L (2020-2021, n = 45) received xylazine 0.2 mg/kg IV before recovery, group XL (2021-2022, n = 44) received xylazine 0.5 mg/kg/h IV intraoperatively. In group XL, minimal (p = 0.04) and average (p = 0.04) heart rate, intraoperative hematocrit (p = 0.001), minimal (p = 0.002) and maximal (p = 0.04) dobutamine administration rate, animals requiring ketamine top-ups (p = 0.04), and the number of days to discharge (p = 0.02), were significantly lower compared to group L. During recovery in group XL, the time to sternal recumbency (p = 0.03) and time to first attempt (p = 0.04) were significantly longer. This retrospective study suggests that a xylazine infusion may have beneficial effects on horses undergoing colic surgery. Further prospective studies are necessary.

Preliminary evaluation of the effects of a 1:1 inspiratory-to-expiratory ratio in anesthetized and ventilated horses

ObjectiveTo describe some cardiorespiratory effects of an inspiratory-to-expiratory (IE) ratio of 1:1 compared with 1:3 in ventilated horses in dorsal recumbency. Study designRandomized crossover experimental study. AnimalsA total of eight anesthetized horses, with 444 (330–485) kg body weight [median (range)]. MethodsHorses were ventilated in dorsal recumbency with a tidal volume of 15 mL kg–1 and a respiratory rate of 8 breaths minute–1, and IE ratios of 1:1 (IE1:1) and 1:3 (IE1:3) in random order, each for 25 minutes after applying a recruitment maneuver. Spirometry, arterial blood gases and dobutamine requirements were recorded in all horses during each treatment. Electrical impedance tomography (EIT) data were recorded in four horses and used to generate functional EIT variables including regional ventilation delay index (RVD), a measure of speed of lung inflation, and end-expiratory lung impedance (EELI), an indicator of functional residual capacity (FRC). Results were assessed with linear and generalized linear mixed models. ResultsCompared with treatment IE1:3, horses ventilated with treatment IE1:1 had higher mean airway pressures and respiratory system compliance (p < 0.014), while peak, end-inspiratory and driving airway pressures were lower (p < 0.001). No differences in arterial oxygenation or dobutamine requirements were observed. PaCO2 was lower in treatment IE1:1 (p = 0.039). Treatment IE1:1 resulted in lower RVD (p < 0.002) and higher EELI (p = 0.023) than treatment IE1:3. Conclusions and clinical relevanceThese results suggest that IE1:1 improved respiratory system mechanics and alveolar ventilation compared with IE1:3, whereas oxygenation and dobutamine requirements were unchanged, although differences were small. In the four horses where EIT was evaluated, IE1:1 led to a faster inflation rate of the lung, possibly the result of increased FRC. The clinical relevance of these findings needs to be further investigated.

Use of dexmedetomidine repeated subcutaneous administration for balanced anaesthesia in horses

BackgroundA balanced anaesthetic protocol is a common concept in modern veterinary anaesthesia and aims to maintain good intraoperative cardiopulmonary function. In horses, alpha-2-agonists produce sedation and analgesia and have been shown to reduce inhalational anaesthetic requirements when administered intravenously. Furthermore, these drugs can improve recovery quality. Preliminary investigations of subcutaneous dexmedetomidine administration in humans demonstrated a reduced haemodynamic impact if compared with the intravenous route suggesting that dexmedetomidine is adequately absorbed with both administration routes. The aim of the study was to compare two different dexmedetomidine (DEX) administration routes: intravenous constant rate infusion (CRI) versus repeated subcutaneous (SC) injections on cardiopulmonary function and recovery in anaesthetized horses.ResultsNo significant differences between groups in heart rate and systolic arterial pressure were detected. A significantly higher mean and diastolic arterial pressure were detected in the SC group at T25 (p = 0.04; p = 0.02), T75 (p = 0.02; p = 0.009), and T85 (p = 0.001; p = 0.005). In SC group there was a significantly lower dobutamine infusion rate (p = 0.03) and a significantly higher urinary output (p = 0.02). Moreover, recovery quality was higher (p = 0.01).ConclusionsCardiopulmonary effects in both groups were comparable and within clinical ranges with less dobutamine requirement in the subcutaneous group. Recovery was of better quality with fewer attempts in horses receiving subcutaneous dexmedetomidine. The present study suggests that intravenous constant rate infusion and subcutaneous repeated administration of dexmedetomidine at indicated dosage can be useful in balanced anaesthesia without any systemic or local adverse effects; moreover, in healthy horses undergoing general anaesthesia, repeated subcutaneous dexmedetomidine administration may be a suitable alternative if constant rate infusion is not feasible.

Influence of the inspiratory-to-expiratory ratio on respiratory mechanics and regional aeration in anesthetized horses in dorsal recumbency

Introduction: Anesthesia impairs respiratory mechanics in horses. Increasing the inspiratory-to-expiratory (IE) ratio could be beneficial. We evaluated the effect of two IE ratios on respiratory mechanics and dobutamine requirements.

Effect of Fentanyl Infusion on Heart Rate Variability and Anaesthetic Requirements in Isoflurane-Anaesthetized Horses.

Simple SummaryHistorically, the use of opioids in equine anaesthesia has been limited due to many reported adverse effects. Even though more research is being conducted, there is conflicting evidence on the efficacy of opioids and their behavioural effects in horses. The aim of this study was to investigate the effect of the synthetic opioid fentanyl on various parameters measured during general anaesthesia, as well as to determine its possible sparing-effect on inhalant anaesthetic.Controversy continues to surround the use of opioids in equine anaesthesia, with variable effects reported. This blinded clinical study aimed to investigate the influence of a low-dose fentanyl continuous rate infusion (CRI) on isoflurane requirements, parasympathetic tone activity (PTA), and anaesthetic parameters in horses during general anaesthesia. All of the twenty-two horses included in the research underwent a standard anaesthetic protocol. Eleven horses in the fentanyl group (Group F) received a loading dose of fentanyl at 6 µg/kg, followed by a CRI of 0.1 µg/kg/min during anaesthesia. A further 11 horses in the control group (Group C) received equivalent volumes of normal saline. Anaesthetic parameters and PTA index were recorded during anaesthesia. The achieved mean fentanyl plasma concentration was 6.2 ± 0.83 ng/mL. No statistically significant differences between groups were found in isoflurane requirements, MAP values, and mean dobutamine requirements. However, horses in Group F required a significantly lower dose of additional ketamine to maintain a sufficient depth of anaesthesia. Significantly higher PTA values were found in the fentanyl group. Further research is warranted to determine the limitations of PTA monitoring, and the influence of various anaesthetics on its values.

Demographic, preoperative and anaesthesia-related risk factors for unsatisfactory recovery quality in horses undergoing emergency abdominal surgery

ObjectiveTo determine demographic, preoperative and anaesthesia-related variables that may be associated with unsatisfactory recovery quality in horses undergoing emergency abdominal surgery (colic) in an equine teaching hospital. Study designRetrospective case series. AnimalsA total of 313 horses. MethodsThe anaesthetic records of horses admitted for surgical treatment of colic between 2005 and 2018 were examined. Overall quality of recovery was assessed as dangerous, poor, fair, good or excellent. The following categories were constructed as a dichotomic variable: unsatisfactory recovery (poor and dangerous recoveries) and satisfactory recovery (excellent, good and fair recoveries). Univariable and multivariable analyses were performed to evaluate the association between all studied variables and recovery. ResultsAll recoveries were unassisted. Unsatisfactory recovery quality totalled 17.2% (3.5% and 13.7% were dangerous and poor recoveries, respectively), whereas satisfactory recoveries totalled 82.8% (26.2%, 40.9% and 15.7% were fair, good and excellent recoveries, respectively). Univariable analysis showed that unsatisfactory recoveries were associated with high preoperative packed cell volume, pain behaviour, poor premedication and induction quality, high intraoperative mean heart rate, low mean arterial blood pressure, dobutamine dose ≥1.5 μg kg–1 minute–1, non-administration of romifidine, long anaesthesia time and prolonged time to stand. The multivariable model showed that factors strongly associated with unsatisfactory recovery quality were dobutamine dose ≥1.5 μg kg–1 minute–1 [adjusted odds ratio (AOR) = 6.60; 95% confidence interval (CI), 2.91–14.96], poor premedication quality (AOR=4.60; 95% CI, 1.73–12.23) and a time to stand > 70 minutes (AOR=2.59; 95% CI, 1.13–5.91). Conclusions and clinical relevanceOur study shows that high dobutamine requirements, poor premedication quality and a prolonged time to stand are risk factors for unsatisfactory recovery quality in horses undergoing anaesthesia for colic surgery. Addressing these factors may enable clinicians to improve the quality of recovery phase.

COVID-19 Complicating Perioperative Management of Left Ventricular Assist Device Implantation

IntroductionThe coronavirus 2019 disease (COVID-19) affected almost 40 million people worldwide and caused more than one million deaths. Some conditions are associated with worse prognosis such as heart failure and left ventricular assist device (LVAD) recipients.Case ReportA 31-year-old male patient without comorbidities was admitted due to cardiogenic shock and pneumonia. He required IABP and ECMO. The patient recovered from organ dysfunctions and ECMO was weaned off. He persisted dependent on dobutamine and IABP. Echocardiogram showed severe left ventricular dysfunction and moderate right ventricular dysfunction (RVD), but right heart catheterization revealed no pulmonary hypertension. SARS-CoV-2 RT-PCR was negative and myocardiopathy investigation was inconclusive after endomyocardial biopsy. LVAD implantation was planned as a bridge to transplant. A Heart Mate 3 was successfully implanted. The patient presented fever in the operating room and persisted febrile for 3 days. COVID-19 was suspected and SARS-CoV-2 RT-PCR was positive. He was extubated on 3rd postoperative day (POD) and echocardiogram showed only mild RVD. On 5th POD, he became hypoxemic requiring high flow nasal cannula, and chest X-ray revealed multiple pulmonary bilateral opacities. Antibiotics and corticosteroids were prescribed. Echocardiogram showed severe RVD and hemodynamic instability led to milrinone and dobutamine requirement in maximal doses. On 10th POD endotracheal intubation was required. The patient experienced severe acute respiratory distress syndrome (ARDS) and multiple complications: shock, bacterial pneumonia, hemothorax, pneumothorax due to barotrauma and bloodstream infection. He had no thromboembolic events. After 48 days he was free from mechanical ventilation and from inotropes. Echocardiogram showed moderate RVD and pulmonary artery systolic pressure 35mmHg. After 51 days he was discharged from the intensive care unit and is now in rehabilitation program.SummarySevere cases of COVID-19 are associated with a cytokine storm and a prothrombotic state. LVAD recipients are at particular risk of unfavorable outcomes. Besides the higher risk of thromboembolic events, LVAD recipients are more vulnerable to RVD in the setting of ARDS. This could be particularly critical during the perioperative management of RV failure as presented in this case.

A retrospective comparison of induction with thiopental/guaifenesin and propofol/ketamine in Thoroughbred racehorses anesthetized with sevoflurane and medetomidine during arthroscopic surgery.

ABSTRACTThis study compares clinical characteristics between induction with thiopental/guaifenesin and propofol/ketamine in Thoroughbred racehorses anesthetized with sevoflurane and medetomidine. Clinical records of 214 horses that underwent arthroscopic surgery between 2015 and 2016 were retrospectively retrieved. Horses were premedicated with medetomidine and midazolam to sedate at the adequate level for smooth induction, and then induced with either thiopental (4.0 mg/kg) and guaifenesin (100 mg/kg) in Group TG (n=91) or propofol (1.0 mg/kg) and ketamine (1.0 mg/kg) in Group PK (n=123). Anesthesia was maintained using sevoflurane with constant rate infusion of medetomidine. Quality of induction/recovery, sevoflurane requirement, cardiovascular function and recovery characteristics were evaluated. Anesthetic induction scores (median, range) for Group TG (5, 2–5) and Group PK (5, 2–5) were not significantly different. There were no significant differences in end-tidal sevoflurane concentration (mean ± standard deviation) between Group TG and Group PK (both 2.4 ± 0.2%). Dobutamine infusion rate (µg/kg/min) required for keeping mean arterial blood pressure (MAP) above 70 mmHg in Group PK (0.43, 0.10–1.40) was significantly lower than in Group TG (0.67, 0.08–1.56). Recovery score in Group PK (5, 2–5) was significantly higher than in Group TG (4, 2–5). Both propofol/ketamine and thiopental/guaifenesin provided a smooth induction of anesthesia. Moreover, induction with propofol/ketamine resulted in lower dobutamine requirements for keeping MAP above 70 mmHg during maintenance, and better quality of recovery. Induction with propofol/ketamine would be preferable to thiopental/guaifenesin in Thoroughbred racehorses anesthetized with sevoflurane and medetomidine during arthroscopic surgery.

Impact of Trendelenburg (head down) and reverse Trendelenburg (head up) position on respiratory and cardiovascular function in anaesthetized horses

ObjectiveTo describe the cardiorespiratory effects of a change in table position in anaesthetized horses. Study designProspective, crossover, randomized, experimental study. AnimalsSix adult horses (mean body weight 621 ± 59 kg, aged 13 ± 4 years). MethodsThe horses were anaesthetized twice in dorsal recumbency. They were either placed in the Trendelenburg position (head down; HD) followed by reverse Trendelenburg position (head up; HU) or in reverse order. Every position was maintained for 90 minutes. The order of positions was randomly assigned at initial anaesthesia. Extensive cardiorespiratory monitoring was performed. Statistical analysis consisted of a mixed model with horses as random effect and time, position, section of anaesthesia and interaction between those as fixed effects (p < 0.05). ResultsWhen HU was applied during the first section of anaesthesia, PaO2, (p = 0.012), oxygen saturation (SaO2, p < 0.01) and oxygen content (CaO2, p < 0.01) were significantly higher, while venous admixture (Q˙s/Q˙t, p < 0.01), mean arterial (p = 0.039), right atrial (p < 0.01) and mean pulmonary arterial pressure (p < 0.01) were lower than in HD. After changing from HU to HD, PaO2 and SaO2 remained higher and Q˙s/Q˙t lower compared to the inverse order. Independent of the order, in the HD position Q˙s/Q˙t (p = 0.019) increased while PaO2 (p < 0.01), SaO2 (p = 0.011), CaO2 (p < 0.01), venous PO2 (Pv¯O2; p = 0.019), venous saturation (p = 0.004) and venous oxygen content (p = 0.010) decreased over time. No significant differences were found for cardiac output, oxygen delivery, oxygen consumption and dobutamine requirement between the two positions. Conclusions and clinical relevanceGas exchange is better preserved in HU compared to HD, especially if applied from the start of the anaesthesia.

Comparison of the effects of an intravenous lidocaine infusion combined with 1% isoflurane versus 2% isoflurane alone on selected cardiovascular variables and recovery characteristics during equine general anaesthesia

ObjectivesTo compare the effects of a lidocaine constant rate infusion (CRI) combined with 1% isoflurane versus those of 2% isoflurane alone on cardiovascular variables in anaesthetized horses, and to estimate the sample size required to detect a difference in recovery quality. Study designProspective, randomized, blinded, crossover study. AnimalsTwelve healthy experimental horses. MethodsHorses were anaesthetized twice using an intravenous (IV) administration of acepromazine, romifidine, diazepam and ketamine. Horses were placed in dorsal recumbency and ventilated mechanically. During the first 10 minutes (P1), anaesthesia was maintained with a 2% inspired isoflurane fraction (FIIso). During the following 20 minutes (P2), horses received IV lidocaine (1.5 mg kg−1) (group IL) or saline (group I). During the last 60 minutes (P3), group IL received a lidocaine CRI (50 μg kg−1 minute−1 IV) and FIIso 1%, whereas group I received a saline CRI and FIIso 2%. Three weeks later, the horses received the alternative treatment. Painful stimuli were induced by introducing an 18 gauge needle intramuscularly. Ketamine and dobutamine requirements and physiological variables were recorded. Recoveries were assessed by two anaesthetists unaware of the treatment. Lidocaine plasma concentrations were measured during recovery. Data were analysed with anova. ResultsDuring P3, group IL had a lower heart rate (p = 0.002), higher mean arterial pressure (p < 0.001) and lower dobutamine requirement (p < 0.001) than group I. One horse had lidocaine plasma concentrations above toxic levels. Recoveries did not differ significantly between groups. Sample sizes of 208 horses in each group would be necessary to detect a statistically significant difference (85% statistical power) in recovery quality. Conclusions and clinical relevanceA lidocaine CRI combined with FIIso 1% rather than FIIso 2% alone may improve cardiovascular variables in healthy anaesthetized horses.

Cardiopulmonary effects and anaesthesia recovery quality in horses anaesthetized with isoflurane and low‐dose S‐ketamine or medetomidine infusions

ObjectivesTo evaluate cardiopulmonary effects and anaesthesia recovery quality in horses anaesthetized with isoflurane receiving medetomidine or S‐ketamine infusions. Study designRandomized, blinded, prospective clinical trial. AnimalsFifty horses undergoing elective surgery. MethodsAfter acepromazine and flunixin meglumine premedication, horses received medetomidine (7 μg kg−1) intravenously (IV). Anaesthesia was induced with midazolam and racemic ketamine (Med treatment group; 2.2 mg kg−1; n = 25) or S‐ketamine (S‐ket treatment group; 1.1 mg kg−1; n = 25) IV and maintained with isoflurane in oxygen/air and medetomidine (Med; 3.5 μg kg−1 hour−1) or S‐ketamine (S‐ket; 0.5 mg kg−1 hour−1). All horses were mechanically ventilated. Cardiopulmonary variables were evaluated. Isoflurane end‐tidal concentrations (Fe′Iso), dobutamine requirements and thiopental boli were recorded. Plasma samples were collected in six horses to evaluate S‐ketamine and S‐norketamine concentrations. After surgery, medetomidine 2 μg kg−1 was administered IV. Four independent observers scored recovery using a visual analogue scale and a numerical rating scale. ResultsBoth groups required similar mean Fe′Iso (1%). However, S‐ket horses needed more thiopental boli. Median intraoperative cardiac index values were higher with S‐ket (4.5 L minute−1 m−2) than Med (3.9 L minute−1 m−2). Overall, there were no differences in heart rate, blood pressure or dobutamine requirements; however, horses in S‐ket showed higher heart rate values at 30 minutes after anaesthesia induction. Compared with Med horses, S‐ket horses showed decreased PaO2 and increased pulmonary venous admixture values estimated with the Fshunt calculation. Recoveries were shorter and of poorer quality with S‐ket. During infusion, S‐ketamine and S‐norketamine plasma concentrations lay in the ranges of 0.209–0.917 μg mL−1 and 0.250–0.723 μg mL−1, respectively. Conclusions and clinical relevanceDespite the higher intraoperative cardiac index with S‐ket, both protocols were considered to provide acceptable cardiovascular function. However, recovery quality was significantly better in the Med group.

Effect of Pre- and Postoperative Phenylbutazone and Morphine Administration on the Breathing Response to Skin Incision, Recovery Quality, Behavior, and Cardiorespiratory Variables in Horses Undergoing Fetlock Arthroscopy: A Pilot Study

This prospective blinded randomized study aimed to determine whether the timing of morphine and phenylbutazone administration affects the breathing response to skin incision, recovery quality, behavior, and cardiorespiratory variables in horses undergoing fetlock arthroscopy. Ten Standardbred horses were premedicated with acepromazine (0.04 mg kg−1 IM) and romifidine (0.04 mg kg−1 IV). Anesthesia was induced with diazepam (0.05 mg kg−1) and ketamine (2.2 mg kg−1) IV at T0. Horses in group PRE (n = 5) received morphine (0.1 mg kg−1) and phenylbutazone (2.2 mg kg−1) IV after induction and an equivalent amount of saline after surgery. Horses in group POST (n = 5) received the inversed treatment. Anesthesia was maintained with isoflurane 2% in 100% oxygen. Hypotension (mean arterial pressure <60 mmHg) was treated with dobutamine. All horses breathed spontaneously. Dobutamine requirements, respiratory rate (fR), heart rate (HR), mean arterial blood pressure, end-tidal CO2, inspired (i) and expired (e) tidal and minute volume (VT and ), inspiratory time (IT), and the inspiratory gas flow (VTi/IT) were measured every 5 min. Data were averaged during four 15 min periods before (P1 and P2) and after the incision (P3 and P4). Serial blood–gas analyses were also performed. Recoveries were unassisted, video recorded, and scored by three anesthetists blinded to the treatment. The postoperative behavior of the horses (25 demeanors), HR, and fR were recorded at three time points before induction (T0–24 h, T0–12 h, and T0–2 h) and six time points after recovery (TR) (TR + 2, 4, 6, 12, 24, 48 h). Data were compared between groups using a Wilcoxon test and within groups using a Friedman test or a Kruskal–Wallis signed-rank test when applicable. Tidal volumes (VTe and VTi) were higher in PRE than in POST during all the considered periods but the difference between groups was only significant during P2 (VTe in mL kg−1 in PRE: 13 [9, 15], in POST: 9 [8, 9], p = 0.01). None of the other variables were significantly different between and within groups. Under our experimental conditions, skin incision did not affect respiratory variables. Administration of pre- versus postoperative phenylbutazone and morphine did not influence recovery quality, HR, fR, or animal behavior.

Left Ventricular Ejection Time in Acute Heart Failure Complicating Precapillary Pulmonary Hypertension

Novel noninvasive tools may improve the management of patients with pulmonary hypertension (PH) experiencing heart failure. Major right ventricle overload leads to decreased stroke volume, which shortens left ventricular ejection time (LVET). Our arterial tonometry study tested the hypothesis that LVET carries prognostic value in patients with precapillary PH with heart failure. Clinical, biologic, and radial artery tonometry variables were prospectively obtained at admission and at day 3 to 5 in 53 consecutive patients with PH admitted to our ICU for clinical deterioration. LVET was measured from the reconstructed aortic pressure curve. Overall ICU mortality (median stay, 5 days) was 17%. At admission, the LVET was shorter in patients with unfavorable outcome (median, 228 milliseconds [25th-75th percentiles, 212-278 milliseconds] vs 257 milliseconds [237-277 milliseconds], P = .032), whereas other tonometric indices were similar. The LVET at entry (237 milliseconds) had 73% sensitivity and 89% specificity for identifying death in the ICU. Other prognostic factors at admission were higher serum levels of brain natriuretic peptide (BNP) and creatinine and lower natremia. Dobutamine requirement, higher furosemide dose, and higher oxygen flow were associated with unfavorable outcome. At the second evaluation, higher serum levels of creatinine and BNP, higher furosemide dose and oxygen flow, and dobutamine or norepinephrine requirement were associated with poor outcome. The change in LVET between admission and follow-up measurement was not associated with outcome. The 90-day mortality was 28%. Shortened LVET at ICU admission was a prognostic factor in patients with precapillary PH with heart failure. Previously documented prognostic factors were also confirmed in this cohort.

Einsatz von Atracurium bei der Vitrektomie des Pferdes

In most ocular procedures, a central position of the eye is necessary. This can be achieved using a deep plane of anaesthesia, locoregional blocks or with neuromuscular blocking agents. The aim of this study was to evaluate the influence of atracurium on cardiovascular parameters, and on recovery quality and duration in horses. Thirty-four warmblood horses undergoing in total 50 vitrectomies were divided into two groups. Premedication, induction and maintenance were identical in all patients. After 20 minutes, horses of group A received atracurium (0.1 mg/kg) while in the control group (group K) the depth of anaesthesia was adapted to keep the bulbus in a central position. Dobutamine and fluids were administered to maintain the mean arterial blood pressure (MAP) above 70 mmHg. Cardiac output (CO), heart rate (HR), MAP, respiratory rate, end-expiratory isoflurane concentration (ETIso) and dobutamine requirements were determined. Position and movement of the globe during the surgical procedure were scored. Time and quality of the recovery period was scored. Horses of group K required significantly higher concentrations of isoflurane (group A: 1.08 ± 0.1%; group K: 1.34 ± 0.2%) and had an overall lower MAP (group A: 88.4 ± 10.3 mmHg; group K: 76.6 ± 11.6 mmHg) and CO (group A: 36.9 ± 11.7 l/min; group K: 28.5 ± 7.2 l/min) but needed significantly more dobutamine (group A: 0.37 ± 0.17 μg/kg/min; group K: 0.99 ± 0.46 μg/kg/min) compared to group A. Complete relaxation occurred 9.5 ± 2.5 minutes after atracurium bolus and lasted for 25 ± 7.1 minutes. The score of the bulbus position and movement was significantly lower in group A, resulting in a better quality for the surgical procedure. In group A, the recovery time to standing was significantly shorter (group A: 18.1 ± 5.4 min; group K: 31.5 ± 7.1 min), with no difference in quality. The use of atracurium resulted in a better cardiovascular condition, probably because of the isoflurane-sparing effect. The recovery time was shorter in these horses without negative effects on recovery quality. No signs of residual atracurium effects were detected.

Use of continuous positive airway pressure (CPAP) to optimise oxygenation in anaesthetised horses – a clinical study

Hypoxaemia is a common problem during equine anaesthesia. Continuous positive airway pressure (CPAP) is a ventilation mode routinely employed in man to overcome hypoxaemia but has not been objectively assessed in horses. To test the effects of CPAP on oxygenation and its indices in anaesthetised horses in a clinical setting. Twenty-four healthy horses requiring anaesthesia in dorsal recumbency were anaesthetised using a standard protocol. Following orotracheal intubation and connection to an anaesthetic machine capable of applying CPAP, horses were randomly allocated to ventilate at physiological airway pressure measured at the airway opening (Group PAP) or to receive CPAP of 8 cmH2O (Group CPAP). Arterial blood gas analysis was performed as soon as arterial cannulation was achieved and 30, 60 and 90 min after induction. If PaCO2 increased above 9.31 kPa controlled ventilation was initiated. Groups were compared using a general linear model. Horses receiving CPAP had significantly higher PaO2 and calculated oxygen indices than horses receiving PAP. No significant differences in ventilation indices were observed between the 2 groups. Eight horses receiving PAP and 5 receiving CPAP required controlled ventilation. No differences in dobutamine requirements or mean arterial pressures were recorded. Continuous positive airway pressure of 8 cmH2O improved oxygenation indices in dorsally recumbent horses without significantly influencing ventilation. Continuous positive airway pressure reduces the incidence of hypoxaemia in anaesthetised horses. Further research is warranted to elucidate the effects of CPAP on the cardiovascular system.

Dexamethasone Pretreatment Provides Antiinflammatory and Myocardial Protection in Neonatal Arterial Switch Operation

This prospective double-blinded randomized study tested the hypothesis that preoperative treatment with dexamethasone would attenuate inflammatory priming of the myocardium, reduce the systemic inflammatory reaction upon cardiac operation, and provide organ protection in neonates. Twenty neonates (age, 8 to 21 days) with transposition of the great arteries scheduled for arterial switch operation were included. Nine received dexamethasone (1 mg/kg body weight) 4 hours before cardiopulmonary bypass, and 11 received natrium chloride. We studied intramyocardial messenger RNA expression of interleukin (IL)-6, IL-8, IL-1β, and tumor necrosis factor-α (TNF-α), as well as IL-10 and expression of TNF-α on protein level in right atrial tissue taken before institution of CPB. We measured plasma levels of IL-6, IL-10, lipopolysaccharide binding protein, and cardiac troponin T. Cytokine expression was related to postoperative outcome. Pretreatment with dexamethasone led to a significant decrease in myocardial expression of IL-6, IL-8, IL-1β, and TNF-α messenger RNA and to a decrease in protein synthesis of TNF-α. Plasma concentrations of IL-6 were significantly lower and those of IL-10 significantly higher in pretreated patients. This was associated with lower cardiac troponin T values and lower dobutamine requirement. Levels of lipopolysaccharide binding protein were significantly higher postoperatively in pretreated neonates. Dexamethasone administration before arterial switch operation leads to a shift in the myocardial and systemic cytokine expression profile in neonates with transposition of the great arteries, with downregulation of proinflammatory and upregulation of antiinflammatory cytokines. Lower myocardial cell damage and lower catecholamine requirement suggest myocardial protection in treated patients.

Cardiorespiratory effects of enoximone in anaesthetised colic horses

No studies have been reported on the effects of enoximone in anaesthetised colic horses. To examine whether enoximone improves cardiovascular function and reduces dobutamine requirement in anaesthetised colic horses. Forty-eight mature colic horses were enrolled in this prospective, randomised clinical trial. After sedation (xylazine 0.7 mg/kg bwt) and induction (midazolam 0.06 mg/kg bwt, ketamine 2.2 mg/kg bwt), anaesthesia was maintained with isoflurane in oxygen and a lidocaine constant rate infusion (15 mg/kg bwt, 2 mg/kg/h). Horses were ventilated (PaCO2 < 8.00 kPa). If hypotension occurred, dobutamine and/or colloids were administered. Ten minutes after skin incision, horses randomly received an i.v. bolus of enoximone (0.5 mg/kg bwt) or saline. Monitoring included respiratory and arterial blood gases, heart rate (HR), arterial pressure and cardiac index (CI). Systemic vascular resistance (SVR), stroke index (SI) and oxygen delivery index (DO2I) were calculated. For each variable, changes between baseline and T10 within each treatment group and/or colic type (small intestines, large intestines or mixed) were analysed and compared between treatments in a fixed effects model. Differences between treatments until T30 were investigated using a mixed model (a = 0.05). Ten minutes after enoximone treatment, CI (P = 0.0010), HR (P = 0.0033) and DO2I (P = 0.0007) were higher and SVR lower (P = 0.0043) than at baseline. The changes in CI, HR and SVR were significantly different from those after saline treatment. During the first 30 min after enoximone treatment, DO2I (P = 0.0224) and HR (P = 0.0003) were higher than after saline administration. Because the difference in HR between treatments was much clearer in large intestine colic cases, an interaction was detected between treatment and colic type in both analyses (P = 0.0076 and 0.0038, respectively). Enoximone produced significant, but short lasting, cardiovascular effects in colic horses. Enoximone's cardiovascular effects in colic horses were of shorter duration than in healthy ponies.

Are there sex-based differences in serum troponin I after cardiac surgery?

To determine whether there are sex-based differences in serum troponin I (TnI) after cardiac surgery with cardiopulmonary bypass. Prospective, observational, cohort study. Tertiary cardiac surgery intensive care unit (ICU) at a university hospital. None. Serum TnI was measured in samples obtained at ICU admission and 6, 12, 24, and 48 hours later. A total of 761 consecutive patients were studied (444 men and 317 women). The characteristics and results of the different sex subgroups were as follows:A) Coronary bypass: 165 men and 38 women. Age, Parsonnet score, Acute Physiology and Chronic Health Evaluation III score, prevalence of renal failure, intra-aortic balloon use, and the lengths of cardiopulmonary bypass, mechanical ventilation, and ICU stay were similar in the two groups. Body mass index, red-cell transfusion needs, and use of noradrenaline were significantly higher in women, whereas dobutamine requirements were higher in men. Mortality: 3 men (1.6%) vs. 0 women (p = not significant).The TnI peak was slightly, but significantly, higher in men (6.2 +/- 4.9 vs. 4.5 +/- 2.6 microg/L. p < 0.05).B) Valve surgery: 279 men and 279 women. Some significant differences were found: Women were older than men and had higher Parsonnet score and transfusion needs. The other recorded variables were similar. Mitral prosthesis: 62 men and 125 women (p < 0.05). Mitral valvuloplasty: 24 men, 7 women (p < 0.05). Aortic prosthesis: 162 men, 103 women (p < 0.05). Mitral and aortic prosthesis: 31 men and 44 women (p < 0.05). TnI peaks were similar for both sexes in each valve subgroup. Mortality: 3 men (1%) vs. 11 women (3.4%) (p < 0.05).The TnI peak did not reach any significant differences between sexes (men 7.9 +/- 6.0 vs. 8.5 +/- 6.5 microg/L in women. p = not significant). No clinically relevant sex-based differences were found in the TnI peaks after cardiac surgery.