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.

Melatonin and CIDR improved the follicular and luteal haemodynamics,uterine and ovarian arteries vascular perfusion,ovarian hormones and nitric oxide in cyclic cows

This study hypothesizes that melatonin with exogenous progesterone (CIDR) can improve follicular, luteal, ovarian and uterine haemodynamic of heat-stressed cows. Holstein cows (N = 12) studied for two spontaneous oestrous cycles during winter then divided equally during summer into the CIDR group received CIDR for 7 days and the melatonin group (Mel) received three injections of melatonin (75 mg/head) at the CIDR insertion, removal and ovulation days. Blood samples were collected to assay oestradiol (E2), progesterone (P4) and nitric oxide (NO). On day 0 (Ovulation), Mel had more small follicles (p < .05), higher ipsilateral and contralateral ovarian arteries (Ov.A.) peak systolic velocity (PSV), higher ipsilateral uterine artery (Ut.A.) PSV (p = .031) and blood flow volume (BFV), also Mel elevated contralateral Ut.A. PSV and BFV (p < .0001) but lowered contra Ut.A. pulsatility index (PI, p < .0001), E2 (p < .01) and NO (p < .0001). Mel increased the corpus luteum diameter (CL, p < .001), coloured area (p < .007) and P4 (p < .0001) on day 5 and reduced them (p < .05; p < .01) on Day 14. On day 10, Mel obtained CL diameter (p < .03) and coloured area (p < .002) of spontaneous that was higher than CIDR and decreased P4 (p < .003). Mel increased CL diameter, area and coloured area and decreased them thereafter. Mel increased the ipsilateral ovarian and uterine arteries PSV and BFV before ovulation and until day 8. Mel increased P4 and decreased NO until days 6 and 14. In conclusion, the improvement in follicular, luteal, ovarian and uterine haemodynamic and the decrease of NO production proved our hypothesis Melatonin doses higher than 75 mg/head is recommended to improve the heat-stressed cow's fertility.     

Medetomidine/midazolam/ketamine anaesthesia in ferrets: effects on cardiorespiratory parameters and evaluation of plasma drug concentrations

ObjectiveTo evaluate the cardiorespiratory effects and plasma concentrations of medetomidine-midazolam-ketamine (MMK) combinations administered by intramuscular (IM) or subcutaneous (SC) injection in sable ferrets (Mustela putorius furo).Study designProspective randomized experimental study.AnimalsEighteen adult ferrets: weight median 1.19 (range 0.81–1.60) kg.MethodsAnimals were allocated to one of three groups: group IM07 received 20 μg kg^?1 medetomidine, 0.5 mg kg^?1 midazolam and 7 mg kg^?1 ketamine IM; group IM10 20 μg kg^?1 medetomidine, 0.5 mg kg^?1 midazolam and 10 mg kg^?1 ketamine IM; and group SC10 20 μg kg^?1 medetomidine, 0.5 mg kg^?1 midazolam and 10 mg kg^?1 ketamine SC. Following instrumentation, cardiorespiratory parameters and plasma drug concentrations were measured every 5 minutes (T5–T30) for 30 minutes Ferrets were then euthanased. Data were analysed using anova for repeated measures. p < 0.05 was considered significant.ResultsResults are mean ± SD. Induction of anaesthesia (minutes) in IM07 and IM10 [2 (1)] was significantly faster than in SC10 [5 (2)]. All groups demonstrated the following: results given as groups IM07, IM10 and SC10 respectively. Mean arterial blood pressures (mmHg) were initially high [186 (13); 174 (33) and 174 (9) at T5] but decreased steadily. Pulse rates were initially 202 (20), 213 (17) and 207 (33) beats minute^?1, decreasing with time. PaO₂ (mmHg) was low [54.0 (8), 47.7 (10) and 38.5 (1)] at T5, although in groups IM07 and IM10 it increased over time. Plasma concentrations of all drugs were highest at T5 (36, 794 and 8264 nmol L^?1 for medetomidine, midazolam and ketamine, respectively) and decreased thereafter: for both midazolam and ketamine, concentrations in IM07 and IM10 were higher than SC10.Conclusions and clinical relevanceMMK combinations containing either 7 or 10 mg kg^?1 ketamine and given IM are suitable combinations for anaesthetising ferrets, although the observed degree of hypoxaemia indicates that oxygen administration is vital.     

Effects of acepromazine on pulmonary gas exchange and circulation during sedation and dissociative anaesthesia in horses

OBJECTIVE: To study pulmonary gas exchange and cardiovascular responses to sedation achieved with romifidine and butorphanol (RB) alone, or combined with acepromazine, and during subsequent tiletamine-zolazepam anaesthesia in horses. ANIMALS: Six (four males and two females) healthy Standardbred trotters aged 3-12 years; mass 423-520 kg. STUDY DESIGN: Randomized, cross-over, experimental study. MATERIALS AND METHODS: Horses were anaesthetized on two occasions (with a minimum interval of 1 week) with intravenous (IV) tiletamine-zolazepam (Z; 1.4 mg kg(-1)) after pre-anaesthetic medication with IV romifidine (R; 0.1 mg kg(-1)) and butorphanol (B; 25 microg kg(-1) IV). At the first trial, horses were randomly allocated to receive (protocol ARBZ) or not to receive (protocol RBZ) acepromazine (A; 35 microg kg(-1)) intramuscularly (IM) 35 minutes before induction of anaesthesia. Each horse was placed in left lateral recumbency and, after tracheal intubation, allowed to breathe room air spontaneously. Respiratory and haemodynamic variables and ventilation-perfusion (; multiple inert gas elimination technique) ratios were determined in the conscious horse, after sedation and during anaesthesia. One- and two-way repeated-measures anova were used to identify within- and between-technique differences, respectively. RESULTS: During sedation with RB, arterial oxygen tension (PaO(2)) decreased compared to baseline and increased mismatch was evident; there was no O(2) diffusion limitation or increase in intrapulmonary shunt fraction identified. With ARB, PaO(2) and remained unaffected. During anaesthesia, intrapulmonary shunt occurred to the same extent in both protocols, and mismatching increased. This was less in the ARBZ group. Arterial O(2) tension decreased in both protocols, but was lower at 25 and 35 minutes of anaesthesia in RBZ than in ARBZ. During sedation, heart rate (HR) and cardiac output (Qt) were lower while arterial-mixed venous oxygen content differences and haemoglobin concentrations were higher in RBZ compared with ARBZ. Total systemic vascular resistance, mean systemic, and mean pulmonary arterial pressures were higher during anaesthesia with RBZ compared to ARBZ. CONCLUSIONS AND CLINICAL RELEVANCE: Acepromazine added to RB generally improved haemodynamic variables and arterial oxygenation during sedation and anaesthesia. Arterial oxygenation was impaired as a result of increased shunt and mismatch during anaesthesia, although acepromazine treatment reduced disturbances and falls in PaO(2) to some extent. Haemodynamic variables were closer to baseline during sedation and anaesthesia when horses received acepromazine. Acepromazine may confer advantages in healthy normovolaemic horses.     

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.

The effects of halothane and isoflurane on cardiovascular function in dorsally recumbent horses undergoing surgery

ObjectiveTo determine the haemodynamic effects of halothane and isoflurane with spontaneous and controlled ventilation in dorsally recumbent horses undergoing elective surgery.Study designProspective randomized clinical trial.AnimalsTwenty-five adult horses, body mass 487 kg (range: 267–690).MethodsHorses undergoing elective surgery in dorsal recumbency were randomly assigned to one of four treatment groups, isoflurane (I) or halothane (H) anaesthesia, each with spontaneous (SB) or controlled ventilation (IPPV). Indices of cardiac function and femoral arterial blood flow (ABF) and resistance were measured using transoesophageal and transcutaneous Doppler echocardiography, respectively. Arterial blood pressure was measured directly.ResultsFour horses assigned to receive isoflurane and spontaneous ventilation (SBI) required IPPV, leaving only three groups for analysis: SBH, IPPVH and IPPVI. Two horses were excluded from the halothane groups because dobutamine was infused to maintain arterial blood pressure. Cardiac index (CI) was significantly greater, and pre-ejection period (PEP) shorter, during isoflurane compared with halothane anaesthesia with both spontaneous (p = 0.04, p = 0.0006, respectively) or controlled ventilation (p = 0.04, p = 0.008, respectively). There was an association between CI and PaCO₂ (p = 0.04) such that CI increased by 0.45 L minute⁻¹m⁻² for every kPa increase in PaCO₂. Femoral ABF was only significantly higher during isoflurane compared with halothane anaesthesia during IPPV (p = 0.0006). There was a significant temporal decrease in CI, but not femoral arterial flow.ConclusionThe previously reported superior cardiovascular function during isoflurane compared with halothane anaesthesia was maintained in horses undergoing surgery. However, in these clinical subjects, a progressive decrease in CI, which was independent of ventilatory mode, was observed with both anaesthetic agents.Clinical relevanceCardiovascular function may deteriorate progressively in horses anaesthetized for brief (<2 hours) surgical procedures in dorsal recumbency. Although cardiovascular function is superior with isoflurane in dorsally recumbent horses, the need for IPPV may be greater.     

川芎嗪和黄芪注射液对家兔急性心肌缺血血流动力学和心电图的影响

目的:探讨川芎嗪和黄芪注射液对家兔急性心肌缺血血流动力学和心电图的影响。方法将2.5月龄家兔18只随机分成3组,设垂体后叶素对照组、川芎嗪组和黄芪组。分别在造模后5min、10min、15min、25min测定左心室收缩压、左心室舒张末压,左心室内压最大上升和最大下降速率;测定Ⅱ导联心电图(ECG)的T波、ST偏移、P-R间期、Q-T间期、心率等的变化。结果:CXz和MR组与PIt组比较,对家兔急性心肌缺血心电图T波抬高和ST段偏移均有极显著或显著抑制作用(P﹤0.01或P<0.05);25min后CXz组MR组均能抑制P-R、Q-T间期的延长、HR增加,但MR组在静脉注射后5~10min对P-R间期和Q-T间期有延长,HR有降低作用。CXz和MR组与PIt组比较对LVSPH和±dp/dtmax均有明显提高,对LVEDP均有降低作用,能够扩张冠状血管和改善心脏舒缩功能。结论川芎嗪和黄芪注射液对垂体后叶素所致家兔急性心肌缺血都具有一定的保护作用,但黄芪组和川芎嗪组对心血管的作用机制有所不同。     

Haemodynamic differences between pancuronium and vecuronium in an experimental pig model

ObjectiveTo compare baseline cardiovascular function in anesthetised pigs using either pancuronium or vecuronium as a neuromuscular blocker.Study designRetrospective, non-randomized comparison.AnimalsNorwegian Land Race pigs (Sus scrofa domesticus) weighing mean 42 ± SD 3 kg.MethodsOne hundred and sixteen animals from four different research protocols premedicated with identical doses of ketamine, diazepam, atropine and isoflurane, and anaesthetised with pentobarbital, fentanyl, midazolam and N₂O were arranged into three uniform groups with respect to neuromuscular blocking agent: pancuronium bolus of 0.063 mg kg⁻¹ followed by 0.14 mg kg⁻¹ hour⁻¹ (n = 54), low-dose vecuronium 0.4 mg kg⁻¹/0.2 mg kg⁻¹ hour⁻¹ (n = 29) and high-dose vecuronium 0.6 mg kg⁻¹/0.3 mg kg⁻¹ hour⁻¹ (n = 33).ResultsThe majority of cardiovascular parameters demonstrated no significant differences between groups. For heart rate, there was an overall group difference, p = 0.036. Dromotropy was low in the pancuronium group, with an increased normalised PR-interval compared to the high-dose vecuronium group, median 0.200 interquartile range (0.190, 0.215) versus 0.182 (0.166, 0.199), p < 0.05. Left ventricular compliance was increased in pancuronium-treated animals, demonstrated as a reduction in the nonlinear end-diastolic pressure volume relationship β compared to both vecuronium groups, 0.021 (0.016, 0.025) versus 0.031 (0.025, 0.046) and 0.031 (0.022, 0.048), p < 0.05. The linear end-diastolic pressure volume relationship EDPVR_lin was reduced as well in the pancuronium group, compared to the low-dose vecuronium group, 0.131 (0.116, 0.169) versus 0.181 (0.148, 0.247), p < 0.05.ConclusionsThere are only minor haemodynamic differences when using pancuronium compared to vecuronium in the fentanyl-pentobarbital-midazolam-N₂O anesthetised domestic pigs. Furthermore, increasing doses of vecuronium have minimal haemodynamic effects.Clinical relevanceExperimental studies in pigs using either pancuronium or vecuronium as a neuromuscular blocking agent are comparable with regard to cardiac and haemodynamic performance.     

Continuous versus intermittent thermodilution for cardiac output measurement during alveolar recruitment manoeuvres in sheep

ObjectiveTo evaluate interchangeability of a thermodilution based STAT mode continuous cardiac output (CCO) measurement method with bolus thermodilution (BTD).Study designRandomized crossover study.AnimalsTen 9 month old healthy male sheep.MethodsEach sheep was anaesthetized twice for laparoscopy. On one occasion mechanical ventilation was used immediately after anaesthetic induction (IPPV treatment) and on the other occasion the start of IPPV was delayed and two periods of alveolar recruitment manoeuvres were also performed (RM treatment). Cardiac output (CO) was measured simultaneously with both CCO and BTD at 6 time points. Data were analysed using difference versus mean plots. A priori limits of acceptance were set at ±30% of the mean of every paired measurement. If <5% of the data fell outside of these limits (Chi-square test, p < 0.05) the interchangeability of methods was accepted. Proportions of data outside of these limits were also compared between treatments (Fisher's test, p < 0.05). Cardiac output data from each treatment and measurement method were also analyzed separately with one-factorial anova and Bonferroni test (p < 0.05).ResultsA total of 119 measurements were obtained. Cardiac output ranged from 1.9 to 10.4 L minute^?1 (CCO) and from 1.1 to 9.8 L minute^?1 (BTD). The bias and limits of agreement were 0.5 ± 1.9 L minute^?1. More than 5% of all data fell outside of the limits of acceptance (24/119), and a larger proportion fell outside of these limits in the RM (20/59) compared to the IPPV treatment (4/60). The Bonferroni test detected significant decreases of CO over time in both treatments when measured with BTD but not with CCO.Conclusions and clinical relevanceThe STAT mode CCO method is not interchangeable with BTD during acute haemodynamic changes caused by recruitment manoeuvres, thus the results of STAT mode CCO should be interpreted with caution because decreases in CO may not be detected.