Effects of sevoflurane on cardiovascular dynamics, coronary circulation and myocardial metabolism in dogs

Exploring kinetic energy as a new marker of cardiac function in the single ventricle circulation

Ventricular volumetric ejection fraction (VV EF) is often normal in patients with single ventricle circulations despite them experiencing symptoms related to circulatory failure. We sought to determine if kinetic energy (KE) could be a better marker of ventricular performance. KE was prospectively quantified using four-dimensional flow MRI in 41 patients with a single ventricle circulation (aged 0.5-28 yr) and compared with 43 healthy volunteers (aged 1.5-62 yr) and 14 patients with left ventricular (LV) dysfunction (aged 28-79 yr). Intraventricular end-diastolic blood was tracked through systole and divided into ejected and residual blood components. Two ejection fraction (EF) metrics were devised based on the KE of the ejected component over the total of both the ejected and residual components using 1) instantaneous peak KE to assess KE EF or 2) summating individual peak particle energy (PE) to assess PE EF. KE EF and PE EF had a smaller range than VV EF in healthy subjects (97.9 ± 0.8 vs. 97.3 ± 0.8 vs. 60.1 ± 5.2%). LV dysfunction caused a fall in KE EF ( P = 0.01) and PE EF ( P = 0.0001). VV EF in healthy LVs and single ventricle hearts was equivalent; however, KE EF and PE EF were lower ( P < 0.001) with a wider range indicating a spectrum of severity. Those reporting the greatest symptomatic impairment (New York Heart Association II) had lower PE EF than asymptomatic subjects ( P = 0.0067). KE metrics are markers of healthy cardiac function. PE EF may be useful in grading dysfunction. NEW & NOTEWORTHY Kinetic energy (KE) represents the useful work of the heart in ejecting blood. This article details the utilization of KE indexes to assess cardiac function in health and a variety of pathophysiological conditions. KE ejection fraction and particle energy ejection fraction (PE EF) showed a narrow range in health and a lower wider range in disease representing a spectrum of severity. PE EF was altered by functional status potentially offering the opportunity to grade dysfunction.

Pressure-volume loop-derived cardiac indices during dobutamine stress: a step towards understanding limitations in cardiac output in children with hypoplastic left heart syndrome

Background

Children with a single systemic right ventricle, such as in hypoplastic left heart syndrome (HLHS), frequently experience reduced exercise capacity. Elucidating the causes could help with optimising treatment strategies.

Methods

Prospective data from 10 consecutive symptomatic patients with HLHS undergoing clinical cardiac magnetic resonance with catheterisation (XMR) were analysed. Mean age 8.6 years (range 3.5–11.6 years), mean time since Fontan completion 5.5 years. MR-compatible catheters were placed in the systemic right ventricle and branch pulmonary arteries to record pressures at rest, with dobutamine infusion at 10 mcg/kg/min and at 20 mcg/kg/min. Cine short-axis stacks of the ventricle were performed at each condition and used to construct pressure–volume loops.

Results

Compared to rest, cardiac index increased with low-dose dobutamine (p < 0.01) with no further rise at peak stress despite a further, albeit, blunted rise in heart rate (p = 0.002). A fall in stroke volume occurred (p = 0.014) despite good contractility (74% increase, p = 0.045) and a well-coupled ventriculo-arterial ratio. End-diastolic pressure and early active relaxation, markers of diastolic function, were normal at rest. However, preload fell at peak stress (p < 0.008) while pulmonary vascular resistance (PVR) was low throughout. This group of HLHS patients demonstrated a fall in SV at peak stress, coinciding with a fall in preload.

Conclusions

Markers of systolic and diastolic function remained normal. Failure to adequately fill the ventricle implies a ceiling of maximal flow through the Fontan circuit despite low PVR.

Changes in circulating blood volume following isoflurane or sevoflurane anesthesia

Changes of circulating blood volume (CB volume) measured by the dual indicator dilution method were observed in 33 chronically instrumented mongrel dogs following either alpha-chloralose-urethane (C group), additive isoflurane (I group) or sevoflurane anesthesia (S group). These anesthetic groups were each divided into two subgroups with regard to respiratory care, namely Cp, Ip and Sp for those with intermittent positive pressure ventilation (six animals per subgroups), and Cs, Is and Ss for those with spontaneous breathing (five animals per subgroups). The CB volume under positive pressure ventilation remained unchanged in the Ip and Sp groups at both 0.5 and 1.0 MAC, and in the Cp group. The CB volume remained essentially unchanged in the Cs and Is groups at both 0.5 or 1.0 MAC, but the plasma volume tended to increase slightly in the Is group at 1.0 MAC. In the Ss group under spontaneous breathing, however, the CB volume increased from 84.4 +/- 7.0 to 91.4 +/- 7.7 at 0.5 MAC, and to 91.4 +/- 10.2 ml.kg(-1) at 1.0 MAC (0.01 < P < 0.05). These increases were caused by an increase in the plasma volume. The above data suggests that a concomitant increase in the venous pressure associated with an increase in the intrathoracic pressure produced by positive pressure ventilation would attenuate changes in the CB volume during sevoflurane anesthesia.

Prolonged sevoflurane, isoflurane and halothane anaesthesia in oxygen using rebreathing or non-rebreathing system in cats

Effects of prolonged sevoflurane, isoflurane and halothane anaesthesia in oxygen on clinical, cardiopulmonary, haematologic, and serum biochemical findings were compared in healthy, premedicated cats breathing spontaneously during 6 h of anaesthesia using rebreathing (semi-closed circuit) or non-rebreathing (Bain coaxial circuit) system. Recovery from anaesthesia with sevoflurane was more rapid than that with halothane or isoflurane in both systems. Respiration and heart rates during sevoflurane anaesthesia were similar to those during isoflurane rather than halothane anaesthesia in both systems. The degree of respiratory acidosis during prolonged sevoflurane anaesthesia was similar to that during isoflurane anaesthesia, and was less than that during halothane anaesthesia in both rebreathing and non-rebreathing systems. Prolonged sevoflurane anaesthesia induced mean arterial pressure similar to isoflurane or halothane anaesthesia in the non-rebreathing system, but it depressed mean arterial pressure less than isoflurane or halothane anaesthesia in the rebreathing system. Time related increase in the arterial carbon dioxide partial pressure was observed during halothane anaesthesia especially in the rebreathing system, however, no significant time-related changes in cardiopulmonary variables were observed during either sevoflurane or isoflurane anaesthesia in both systems. There were no significant differences among sevoflurane, isoflurane and halothane anaesthesia in serum biochemical values in both systems.

Sevoflurane preserves endocardial blood flow during coronary ligation in dogs: comparison with adenosine

BACKGROUND

Sevoflurane has been reported to attenuate ischaemia-induced changes of myocardial metabolism, but the mechanism is still unclear. We examined the effect of sevoflurane on regional myocardial blood flow (RMBF) in the ischaemic area and compared the flow with that in the presence of adenosine.

METHOD

Twenty-seven mongrel dogs were anaesthetized with fentanyl infused at the rate of 1 microgram.kg-1.min-1 throughout the experiment. Then they were divided into 4 groups; 0, 1, 2 MAC sevoflurane groups and adenosine group. Adenosine was infused into the left ventricle at a rate of 14.5 mg.kg-1.h-1. The left anterior descending coronary artery (LAD) was ligated for 3 min. RMBF in the endo- and epicardial layers were measured using coloured microspheres.

RESULTS

Sevoflurane decreased both systolic and diastolic blood pressures and LV dp/dt max. Adenosine increased heart rate and coronary flow. The endocardial blood flow in 2 MAC sevoflurane was almost the same as that in the 0 MAC group. Adenosine significantly increased the myocardial blood flow. During 3-min ischaemia, endocardial blood flow in the ischaemic area under 2 MAC sevoflurane was essentially the same as those in 0 MAC and adenosine groups, though myocardial work in 2 MAC sevoflurane was lower compared with that of the other groups.

CONCLUSION

Preservation of endocardial blood flow related to the myocardial work during ischaemia occurred during 2 MAC sevoflurane. The decrease in LV dp/dt max induced by 2 MAC sevoflurane is one of the factors responsible for the preservation of the endocardial blood flow during ischaemia.

Cardiopulmonary effects of sevoflurane in cats: comparison with isoflurane, halothane, and enflurane

The cardiopulmonary effects of sevoflurane (mean, 2.6, 3.8-3.9 and 5.2 per cent) were compared with those of halothane (1.2, 1.8 and 2.4 per cent), enflurane (2.4, 3.6 and 4.8 per cent) and isoflurane (1.6, 2.4 and 3.2-3.3 per cent) at end-tidal concentrations equivalent to 1, 1.5 and 2 minimal alveolar concentrations (MACs) during spontaneous or controlled ventilation (SV or CV) in 57 cats. Cats were assigned to four groups of nine animals each in SV trial and four groups of five or six animals each in CV trial. During SV, respiration rate was decreased by sevoflurane and isoflurane at 2 MAC and by enflurane at each MAC multiple when compared with control values, whereas halothane increased respiration rate at 2 MAC. The degree of hypercapnia and acidosis induced by sevoflurane was not different from that induced by isoflurane and was less than that induced by halothane at 1 to 1.5 MAC or enflurane at 2 MAC. During SV and CV, four anaesthetics decreased heart rate at 2 MAC when compared with control values, but there was no significant difference between anaesthetics. Sevoflurane, like halothane and isoflurane, induced hypotension at 2 MAC when compared with 1 MAC.

Comparisons of prolonged sevoflurane, isoflurane, and halothane anaesthesia combined with nitrous oxide in spontaneously breathing cats

The clinical, cardiopulmonary, haematologic, and serum biochemical effects of sevoflurane, isoflurane and halothane anaesthesia with 66% nitrous oxide, were compared in healthy, premedicated cats breathing spontaneously during 6 h of anaesthesia. Recovery time from anaesthesia with sevoflurane-nitrous oxide was more rapid than that with halothane-nitrous oxide, but it does not differ from that with isoflurane-nitrous oxide. The degree of respiratory acidosis with sevoflurane-nitrous oxide anaesthesia was similar to that with isoflurane-nitrous oxide and was less than that with halothane-nitrous oxide. There were no significant differences among the groups in the heart rate, arterial pressures, haematological and serum biochemical values. The three anaesthetic regimens induced a similar degree of hyperglycemia during anaesthesia. Serum biochemical examination did not reveal apparent hepatic or renal injuries after each anaesthesia. Time-related increases in respiration rate and arterial carbon dioxide partial pressure were observed during prolonged halothane-nitrous oxide anaesthesia. No significant time-related changes in cardiopulmonary variables were observed during either sevoflurane- or isoflurane-nitrous oxide anaesthesia. Therefore, sevoflurane-nitrous oxide may be used as an effective and safe anaesthetic combination similar to isoflurane-nitrous oxide for long-term anaesthesia in healthy cats.

Sevoflurane anesthesia maintains reflex tachycardia on position change from supine recumbent to head-up tilt

This study evaluated the effects of inhalational anesthetics on hemodynamic changes in response to head-up tilt in humans. Twenty-four patients were randomly divided into three groups that received either halothane, isoflurane, or sevoflurane. Changes in heart rate, blood pressure, and plasma norepinephrine concentrations were determined before and during head-up tilt position in the awake and anesthetized state. Head-up tilt caused a significant increase in the heart rate, concomitantly with a decrease or no significant changes in systolic blood pressure in the awake state. However, under 2 minimum alveolar concentrations (MAC) of halothane and isoflurane anesthesia, the heart rate did not significantly change during head-up tilt in spite of significant decreases in systolic blood pressure. In contrast, under 2 MAC of sevoflurane anesthesia, the heart rate significantly increased during head-up tilt. Plasma norepinephrine did not significantly alter during head-up tilt in the awake as well as the anesthetized state. These results suggest that sevoflurane maintains an increase in heart rate in response to head-up tilt, whereas halothane and isoflurane attenuate the response.

Comparisons of sevoflurane, isoflurane, and halothane anesthesia in spontaneously breathing cats

The clinical effects of sevoflurane, isoflurane, and halothane anesthesia with or without nitrous oxide, were compared in healthy, premedicated cats breathing spontaneously during 90 minutes of anesthesia. The effect of nitrous oxide in accelerating the induction of and recovery from anesthesia was more evident for halothane than for sevoflurane or isoflurane. The cats recovered more rapidly from sevoflurane-oxygen than from either halothane- or isoflurane-oxygen. Heart rates did not significantly change during anesthesia with any of the anesthetics. Arterial blood pressures during sevoflurane-oxygen anesthesia were somewhat higher than those with either isoflurane- or halothane-oxygen. There were no significant differences in arterial blood pressures among sevoflurane, isoflurane, and halothane anesthesia when combined with nitrous oxide. The respiration rate during sevoflurane-oxygen was similar to that during halothane-oxygen. There were no significant differences in respiration rate among sevoflurane, isoflurane, and halothane anesthesia when combined with nitrous oxide. The degree of hypercapnia and acidosis during sevoflurane anesthesia was similar to that observed during isoflurane anesthesia and less than during halothane anesthesia. The three anesthetic regimens, with or without nitrous oxide, induced a similar degree of hyperglycemia and hemodilution during anesthesia. Serum biochemical examination did not reveal any hepatic or renal injuries after each anesthesia.

Cardiovascular and pulmonary effects of sevoflurane anesthesia in horses

The effects of 1.0, 1.5, and 2.0 minimum alveolar concentration (MAC) of sevoflurane on hemodynamic, pulmonary and blood chemistry variables were measured during spontaneous and controlled ventilation in healthy horses. Sevoflurane was the only anesthetic drug administered to the horses. In a dose-dependent manner, sevoflurane significantly decreased (P < .05) mean arterial blood pressure, cardiac output, and stroke volume. There was a progressive decrease in peripheral vascular resistance and an increase in heart rate as the concentration of sevoflurane was increased, but the differences were not significant. During spontaneous ventilation there was a dose-dependent decrease in respiratory rate that caused a decrease in the minute volume. As the dose of sevoflurane increased, the arterial carbon dioxide tension also increased (P < .05). All blood chemistries remained within normal limits. Recovery from anesthesia was without incident. In conclusion, sevoflurane induces a dose-dependent decrease in hemodynamic variables and pulmonary function in horses that is not greatly different from that of other approved inhalant anesthetics.

Sevoflurane in paediatric anaesthesia: effects on respiration and circulation during induction and recovery

This study examined induction and recovery times and respiratory and cardiovascular changes during induction and recovery in paediatric patients undergoing anaesthesia under spontaneous respiration induced with sevoflurane (S group, n = 10) and halothane (H group, n = 9) at 2.4 MAC. FET/FI increased more rapidly, the incidence of breath holding and coughing was less and the recovery time was shorter in the S group compared with the H group. During induction with sevoflurane at 2.4 MAC, min vol/bodyweight decreased due to reduced tidal vol/bodyweight despite increased respiratory frequency, as with halothane at the same MAC. Slight decrease in blood pressure was observed during induction in the S group, while the circulatory depression was not observed during induction in the H group. These results suggest that sevoflurane is a suitable agent for induction under spontaneous respiration with higher concentrations in paediatric anaesthesia.

Effects of sevoflurane on ischaemic myocardium in dogs

We studied the effect of sevoflurane on ischaemic myocardium in terms of myocardial energy and carbohydrate metabolism. Mongrel dogs were anaesthetized initially with sodium pentobarbitone, and then inhaled sevoflurane at 0% (0 MAC), 2.4% (1.0 MAC) or 4.7% (2.0 MAC) of inspired concentration for 60 min. Ischaemia was then induced for 3 min by ligating the left anterior descending coronary artery. The tissue levels of energy and carbohydrate metabolites were determined before and after sevoflurane inhalation, and after 3 min of ischaemia. Sevoflurane significantly decreased systolic and diastolic blood pressures, heart rate, and rate-pressure product in a dose dependent manner. When the animals did not inhale sevoflurane (0 MAC), ischaemia significantly decreased adenosine triphosphate and creatine phosphate levels, and produced alterations of carbohydrate metabolism. These metabolic changes induced by ischaemia were lessened by inhalation of sevoflurane. To exclude the influence of haemodynamic changes, blood pressure and heart rate were maintained during 1.0 MAC sevoflurane inhalation. Significant attenuation of ischaemia-induced metabolic changes caused by sevoflurane was still observed in some metabolites. These results indicate that the ischaemic influences on the myocardium may be reduced by sevoflurane, and this protective effect can be explained not only by its haemodynamic effect.

Sevoflurane and oxygen anaesthesia following administration of atropine-xylazine-guaifenesin-thiopental in spontaneously breathing horses

The effects of sevoflurane-oxygen anaesthesia at a light-surgical depth on clinically important features were evaluated in spontaneously breathing horses that received atropine, xylazine, and guaifenesin-thiopental. Mean end-tidal concentrations of sevoflurane ranged from 1.6 to 2.3% during 90 min maintenance. Recovery from anaesthesia was extremely rapid and smooth. Heart rates did not significantly change after anaesthesia. Arrhythmia was not observed. Mean arterial pressure (mean +/- SD) ranged from 86 +/- 17 to 98 +/- 5 mmHg during anaesthesia. Minute ventilation was low due to decreased respiratory rates during anaesthesia. Changes in arterial blood gases and pH demonstrated respiratory acidosis during anaesthesia. Haematological findings revealed haemodilution during anaesthesia. Serum potassium decreased slightly during anaesthesia, but other serum biochemical values did not significantly change for 7 days post-anaesthesia. These results suggest that sevoflurane may be an effective inhalant anaesthetic which produces a rapid recovery from anaesthesia in horses.

The echocardiographic assessment of left ventricular performance during sevoflurane and halothane anesthesia

The cardiovascular effects of sevoflurane were studied and compared with those of halothane in 30 healthy patients. The patients were assigned to receive 1 MAC sevoflurane (n = 10), 2 MAC sevoflurane (n = 10) or 1 MAC halothane (n = 10) in N(2)O 2 l.min(-1) and O(2) 4 l.min(-1). The changes in left ventricular diastolic and systolic dimension (Dd and Ds), fractional shortening (FS), mean velocity of circumferential fiber shortening (mVcf), left ventricular diastolic and systolic volume (Vd and Vs), stroke volume (SV), ejection fraction (EF) and cardiac index (CI) were evaluated by echocardiography. Sevoflurane produced significant dose-dependent decreases in FS, mVcf, EF and SV, but no significant changes in Dd and Vd. Therefore, the decrease in SV was due mainly to the increase in left ventricular residual volume (Vs). One MAC halothane produced a more significant decrease in FS, mVcf, EF and SV, when compared to values obtained at 1 MAC sevoflourane ( P < 0.01). CI was more significantly decreased with 1 MAC halothane than with 1 MAC and 2 MAC sevoflurane ( P < 0.01). This was brought about by a slight decrease in HR with halothane and a slight increase in HR with sevoflurane, in addition to a smaller decrease in SV with sevoflurane than with halothane. This study suggests that sevoflurane may better preserve cardiac function as a pump in healthy patients, when compared to halothane.

Effects of sevoflurane with or without nitrous oxide on cardiac contractility and sinoatrial node rate

Cardiac effects of sevoflurane (SE) with or without nitrous oxide were examined in the canine blood-perfused papillary muscle and sinoatrial node preparations. Although SE depressed developed tension (DT), mean arterial pressure (MAP) and heart rate of the donor dog (DHR) dose dependently, sinoatrial rate (SAR) was not changed significantly. No significant changes in MAP, DHR and SAR were observed with the addition of nitrous oxide to SE. However, the addition of nitrous oxide to SE resulted in significant decrease of DT. These results suggest that SE depresses BP and cardiac contractility dose dependently, but dose not change heart rate. The combination of nitrous oxide and SE may produce less cardiovascular depressant effect at a given MAC level than SE given alone.