Effects of certain i.v. anaesthetics on liver blood flow and hepatic oxygen consumption in the greyhound

Personalized anesthesia and precision medicine: a comprehensive review of genetic factors, artificial intelligence, and patient-specific factors

Precision medicine, characterized by the personalized integration of a patient's genetic blueprint and clinical history, represents a dynamic paradigm in healthcare evolution. The emerging field of personalized anesthesia is at the intersection of genetics and anesthesiology, where anesthetic care will be tailored to an individual's genetic make-up, comorbidities and patient-specific factors. Genomics and biomarkers can provide more accurate anesthetic protocols, while artificial intelligence can simplify anesthetic procedures and reduce anesthetic risks, and real-time monitoring tools can improve perioperative safety and efficacy. The aim of this paper is to present and summarize the applications of these related fields in anesthesiology by reviewing them, exploring the potential of advanced technologies in the implementation and development of personalized anesthesia, realizing the future integration of new technologies into clinical practice, and promoting multidisciplinary collaboration between anesthesiology and disciplines such as genomics and artificial intelligence.

Anesthesia Patients with Concomitant Cardiac and Hepatic Dysfunction

Anesthesia and surgery in patients with hepatic and cardiac dysfunction poses a challenge for anesthesiologists. It is imperative to optimize these patients perioperatively. Cirrhosis is associated with a wide range of cardiovascular abnormalities. Cirrhotic cardiomyopathy is characterized by blunted contractile responsiveness or systolic incompetence, and/or diastolic dysfunction. In liver disease, anesthetic drug distribution, metabolism, and elimination may be altered. Among patients with liver disease, propofol is a reasonable anesthetic choice and cisatracurium is the preferred neuromuscular blocker. Regional anesthesia should be used whenever appropriate if not contraindicated by coagulopathy, because it reduces the need for systemic analgesia.

Development of pharmacophoric maps for cardiovascular depression by intravenous anaesthetic agents: comparison with maps for immobilizing activity

BACKGROUND

The molecular basis of the cardiovascular effects of i.v. anaesthetics was investigated using comparative molecular field analysis (CoMFA).

METHODS

The cardiovascular effects, measured as changes in mean arterial pressure (MAP), compared with awake values of continuous infusions of 13 structurally diverse i.v. anaesthetics were compared at EC(50) plasma concentrations, and by determination of plasma-free drug concentrations associated with a 20% decrease in MAP (dMAP(20)). Data were obtained both from the literature and from unpublished data of the author. The results were fitted to a CoMFA activity model using field-fit minimization techniques to maximize similarities in molecular bulk and electrostatic potential to the lead compound, eltanolone.

RESULTS

The final model for cardiovascular depression based on free drug concentrations associated with dMAP(20) explained 95.8% of the variance in observed activities, with a cross-validated q(2) of 0.824 (n=12). A second model based on change in MAP at EC(50) plasma concentrations explained 98.3% of the variance in arterial pressure, but performed poorly at cross-validation (q(2) 0.526). The comparative model for immobilizing potency had an r(2) value of 0.987 and q(2) 0.823. Comparison of pharmacophoric maps showed several key electrostatic and steric regions common to both models when isocontours were constructed linking lattice grid points, making the greatest 40% contributions (87.57% for electrostatic fields and 86.16% for steric fields).

CONCLUSIONS

Comparison of activity models for cardiovascular depression and immobilizing potency for i.v. anaesthetics shows significant commonality, suggesting that it may not be possible to separate those molecular features associated with each of these effects.

What makes a molecule an anaesthetic? Studies on the mechanisms of anaesthesia using a physicochemical approach

Recent studies of mechanisms of anaesthesia have been mainly 'target orientated', investigating the activity of both volatile and i.v. agents at putative sites of action. An alternative approach is one that is 'ligand orientated', focusing on the properties of molecules that define their immobilizing ability and secondly define their potency. The use of conventional descriptors (such as non-polar solubility or the octanol-water partition coefficient [Log P]) are limited in their utility as predictors of potency as they represent three-dimensional molecular properties as a one-dimensional parameter. Using different computer-based molecular modelling methods (molecular similarity studies and comparative molecular field analysis [CoMFA]), we have identified the molecular bases of the activity of structurally diverse anaesthetics, such that they can be described as a single model based on the spatial distribution of molecular bulk and electrostatic potential. The same approach can also be used to model other properties of anaesthetic agents, such as cardiovascular depression. The present data suggest that, for the i.v. agents, it may be difficult to separate immobilizing (anaesthetic) activity and cardiovascular depression within a single molecule.

Placental transfer of etomidate in pregnant ewes after an intravenous bolus dose and continuous infusion

Etomidate (ETO) is a short-acting intravenous (IV) anaesthetic characterised by cardiopulmonary stability and favourable pharmacokinetics. Although ETO has been used satisfactorily in obstetrical anaesthesia, little is known about placental transfer and the drug's pharmacokinetics in the fetus. Placental transfer in pregnant ewes has been evaluated following the administration of an IV bolus of 1mg/kg ETO; and after a 1-h infusion of 100 microg/kg min(-1) ETO preceded by an IV bolus of 1mg/kg. In ewes, ETO concentration and AUC were higher than those found in fetuses. After the ETO bolus dose, the fetus:ewe AUC ratio was 0.45+/-0.32, and the mean residence time (MRT) was 20+/-7 min for dams and 22+/-3 min for the fetuses. After ETO infusion, the AUC ratio was 0.37+/-0.08, and MRT was 46+/-12 min for ewes and 46+/-22 min for fetuses. Although ETO crosses the placenta very rapidly and reaches the fetus in high amounts, a certain placental barrier effect limits its transfer. There is no evidence of cumulative effects of the drug in the fetus as fetal ETO elimination was as rapid as in the dam.

A model to investigate hepatic extraction of oxygen during anaesthesia in the dog

Measurement of hepatic oxygen extraction was performed on six healthy Greyhound dogs over a two hour period. The Greyhounds were anaesthetised and a right subcostal surgical incision performed. Ultrasonic flow transducers were used to measure flow rate in the hepatic artery and the portal vein. The blood oxygen tensions in arterial blood and in the portal and hepatic veins were also measured. Hepatic oxygen extraction remained stable throughout the study, despite a steady decline in arterial blood pressure. The methodology described in this study provides a direct measure of oxygen uptake by the liver in the dog and could readily be used to investigate hepatic uptake of drugs.

Etomidate and telazol

These two drugs, etomidate and Telazol, have different pharmacological properties. The good properties of these drugs should be employed in specific patients and procedures to be performed (Table 3). There is no ideal injectable agent available yet for clinical practice. This in itself makes practice quite interesting because of the continuous process of rationalizing and determining the best drug for a specific condition and patient.

Splanchnic haemodynamics after intravenous terlipressin in anaesthetised healthy pigs

BACKGROUND/AIMS

Terlipressin is used for the treatment of bleeding oesophageal varices. We evaluated the effects of terlipressin on hepatic haemodynamics, with special focus on the interactions between portal venous flow and hepatic arterial flow over time. Secondly, we evaluated the estimated hepatic blood flow by the ICG clearance method against direct measurements of hepatic blood flow.

METHODS

Eight healthy anaesthetised pigs received terlipressin 1 mg or placebo intravenously in a randomised, blind, cross-over design. Hepatic arterial flow, portal venous flow, systemic haemodynamics, and portal vein diameter were recorded simultaneously. Portal venous flow and hepatic arterial flow were measured by transit time ultrasound flowmetry. Estimated hepatic blood flows at baseline and after terlipressin were compared with the sum of the portal venous flow and hepatic arterial flow.

RESULTS

Portal venous flow decreased significantly 5 min after administration of terlipressin (p<0.05). At 30 min it had decreased by 34% (p<0.01) and the hepatic arterial flow had increased by 81% (p<0.01). The estimated hepatic blood flow and the hepatic blood flow decreased by 23% (p<0.015). At baseline the estimated hepatic blood flow and the hepatic blood flow correlated significantly (r=0.85, p<0.01), but this correlation disappeared after administration of terlipressin (r=0.06, p=ns). The hepatic blood flow was 12% higher than the estimated hepatic blood flow before and after terlipressin.

CONCLUSIONS

Terlipressin decreased the portal venous flow, hepatic blood flow, and estimated hepatic blood flow significantly and was accompanied by a substantial increase in hepatic arterial flow. The estimated hepatic blood flow and hepatic blood flow were strongly correlated at baseline, but after terlipressin the correlation disappeared.

Influences of cardiopulmonary bypass and fentanyl anesthesia on hepatic circulation and oxygen metabolism in beagles

Decreases in hepatic blood flow (HBF) have been reported in patients and in animal experiments during cardiopulmonary bypass (CPB). We examined changes in HBF and hepatic oxygen metabolism during CPB in 16 beagles anesthetized with fentanyl. Hepatic arterial blood flow (HABF) and portal venous blood flow (PVBF) were measured by using an electromagnetic flowmeter before and during normothermic and hypothermic CPB with 10 microg x kg(-1) x h(-1) (F-10 group; n = 8) or 50 microg x kg(-1) x h(-1) (F-50 group; n = 8) of fentanyl anesthesia. CPB was conducted with membrane oxygenation and a nonpulsatile pump flow of 2.4 L x m(-2) x min(-1). Hepatic oxygen delivery (HDO2) and consumption (HVO2) were calculated from HBF and oxygen content in arterial, portal venous, and hepatic venous blood. HABF did not change during normothermic CPB in the F-10 group, but it decreased significantly during hypothermic CPB in both groups, especially the F-50 group. During CPB, PVBF and total HBF decreased significantly in both groups-more so with the larger dose of fentanyl--whereas HDO2 decreased significantly because the arterial and portal venous blood oxygen levels decreased. The HVO2 was stable in the F-10 group but was significantly depressed during CPB in the F-50 group. Our results indicate that during hypothermic nonpulsatile CPB larger doses of fentanyl are associated with reduced HBF and impaired HDO2 and HVO2.

IMPLICATIONS

Hepatic dysfunction after cardiopulmonary bypass (CPB) has been frequently reported and could be partly attributed to hepatic circulatory disturbance during CPB. We found that, in beagles, large doses of fentanyl were associated with greater decreases in hepatic blood flow and hepatic oxygen metabolism during hypothermic CPB than smaller doses of fentanyl.

Effects of sevoflurane and halothane anesthesia on liver circulation and oxygen metabolism in the dog during hepatolobectomy

PURPOSE

Effects of sevoflurane and halothane anesthesia on liver circulation and oxygen metabolism during hepatolobectomy were investigated in the dog, with the aim of choosing a better anesthetic for hepatic resection.

METHODS

Sixteen mongrel dogs were randomly divided into two groups with eight in each. Electromagnetic flowmeters were used to measure hepatic arterial and portal venous blood flows (1) before the inhalation of each anesthetic (base line); (2) 1 h after the start of inhalation of 1.5 minimum alveolar concentration (MAC) anesthetic; (3) 1 h after hepatolobectomy with the same MAC of anesthesia; and (4) 2 h after the discontinuation of anesthesia. Measurements of systemic hemodynamics, blood gas tensions, plasma enzyme leaks and arterial ketone body ratio were made at the same time.

RESULTS

Sevoflurane maintained hepatic arterial blood flow better than halothane anesthesia, both before and after hepatolobectomy. Hepatic arterial vascular resistance increased in the halothane group but did not change in the sevoflurane group after hepatolobectomy. No significant difference was found in oxygen metabolism and arterial ketone body ratio between two groups. Serum enzyme leakage was less in the sevoflurane group.

CONCLUSION

Sevoflurane has less adverse effects on liver circulation, especially hepatic arterial blood flow, and hepatic function than halothane in the case of hepatolobectomy.

Effects of enflurane and isoflurane on splanchnic oxygenation in humans

STUDY OBJECTIVES

To determine the effects of enflurane and isoflurane on hepatic venous oxygen saturation (ShvO2) and splanchnic oxygen (O2) extraction. To measure hemodynamic parameters and ShvO2, mixed venous, and arterial lactate concentrations during enflurane and isoflurane anesthesia.

DESIGN

Randomized, prospective study.

SETTING

University hospital.

PATIENTS

20 ASA physical status I, II, and III adults, who underwent major abdominal surgery requiring mechanical ventilation a few hours postoperatively.

INTERVENTIONS

After placement of catheters in the pulmonary artery, radial artery, peripheral and right hepatic vein, one hour postoperatively either enflurane or isoflurane was applied at different minimum alveolar concentration (MAC) of 0.5, 1.0, and 1.5 in a randomized order.

MEASUREMENTS AND MAIN RESULTS

Before and 10 minutes after administration of each desired end-expiratory anesthetic concentration, the following parameters were determined: hemodynamic parameters, arterial (SaO2), mixed venous (SvO2), and hepatic venous oxygen saturations, systemic and splanchnic O2 extraction, arterial, mixed venous, and hepatic venous lactate concentrations. Cardiac output (CO) and mean arterial pressure (MAP) decreased in a dose dependent manner. SaO2, SvO2, and systemic O2 extraction remained unchanged with enflurane and isoflurane anesthesia. In the enflurane group, but not in the isoflurane group, ShvO2 decreased with increasing inhalational concentrations. This decrease in ShvO2 reflected an increase in splanchnic O2 extraction with enflurane; in contrast to isoflurane.

CONCLUSIONS

Enflurane causes a decrease in ShvO2, which indicates an impairment of splanchnic perfusion corresponding to the reduction in CO and MAP in a dose-dependent manner. Isoflurane maintains splanchnic perfusion in contrast to enflurane.

Effects of positive end-expiratory pressure ventilation on splanchnic oxygenation in humans

OBJECTIVES

To examine the influence of positive end-expiratory pressure (PEEP) ventilation on splanchnic oxygenation and lactate production in humans without pulmonary disorders.

DESIGN

Prospective study.

SETTING

Single-institutional surgical intensive care unit in a university hospital.

PARTICIPANTS

Twenty patients who underwent major abdominal surgery.

INTERVENTIONS

Radial artery, pulmonary artery, and right hepatic vein catheters. Blood samples were collected to determine lactate concentrations and oxygen saturations.

MEASUREMENTS AND MAIN RESULTS

Six hours postoperatively PEEP levels (5, 10, and 15 cmH2O) were applied in a randomized order, and the following parameters were determined before and at the end of each PEEP level: cardiac output (CO); mean arterial pressure (MAP); arterial (SaO2), mixed venous (SvO2) and hepatic venous oxygen saturation (ShvO2); systemic (C[a-v]O2) and splanchnic (C[a-hv]O2) arterial venous oxygen content difference; and arterial, mixed venous, and hepatic venous lactate concentration. CO and MAP were reduced at PEEP 10 and 15 cmH2O, accompanied by a decrease in SvO2 but unchanged SaO2. A decrease in ShvO2 was seen at PEEP 15 cmH2O. C(a-v)O2 and C(a-hv)O2 were increased at PEEP 15 cmH2O. However, at PEEP 15 cmH2O, the percent increment in C(a-hv)O2 was greater than the increment in C(a-v)O2. Lactate concentrations remained unchanged.

CONCLUSIONS

Ventilation with PEEP causes reductions in CO and MAP, resulting in a comparable impairment of systemic and splanchnic oxygen. The absence of changes in lactate concentrations indicates that a critical reduction in systemic and splanchnic oxygenation is unlikely during ventilation with low or high PEEP levels.

Use of proton nmr spectroscopy to measure propofol metabolites in the urine of the female Caucasian patient

1. Six female Caucasian patients received i.v. doses of propofol (2.7 +/- 0.3 (SE) mg/kg) for induction of anaesthesia. Anaesthesia was maintained with nitrous oxide, oxygen and enflurane for periods up to 3 h. A total urine collection was made from each subject for 24 h after administration of propofol; samples were concentrated and analysed for propofol metabolites by nmr spectroscopy. 2. By 24 h, 50.9 +/- 4.0% of the dose of propofol was recovered as metabolites. The proportions of propofol metabolites, 1-quinol glucuronide (1-QG), 4-quinol glucuronide (4-QG), propofol glucuronide (PG) and 4-quinol sulphate (4-QS) recovered in urine (0-24 h) of the patients were 12 +/- 1, 8 +/- 2, 76 +/- 4 and 4 +/- 1% respectively. However, one patient showed a metabolite profile in which PG comprised 93% and 1-QG 7% of the total metabolites. 3. Nmr spectroscopy has been shown to be a satisfactory method for the quantification of propofol metabolites in urine without the necessity for reference samples.

Differential influence of laboratory anaesthetic regimens upon renal and hepatosplanchnic haemodynamics in the rat

Renal blood flow in rats anaesthetized with the combination alphaxolone/alphadolone (3.90 mL min-1 (g tissue)-1) was significantly (P less than 0.05) greater than in rats anaesthetized with ketamine midazolam (3.24 mL min-1 (g tissue)-1, pentobarbitone (3.19 mL min-1 (g tissue)-1), fentanyl/fluanisone midazolam (2.84 mL min-1 (g tissue)-1) or urethane (1.99 mL min-1 (g tissue)-1). Renal blood flow in the urethane anaesthetized rats was significantly (P less than 0.05) lower than in animals anaesthetized with the other anaesthetic regimens, and is consistent with literature reports of a depressive effect of urethane anaesthesia upon xenobiotic renal clearance in the rat. Hepatosplanchnic blood flow was highest in the alphaxolone/alphadolone anaesthetized animals (71.7 mL min-1 kg-1), with the urethane anaesthetized animals demonstrating a significantly (P less than 0.05) lower (33.4 mL min-1 kg-1) blood flow. The fentanyl fluanisone/midazolam (65.4 mL min-1 kg-1), pentobarbitone (61.1 mL min-1 kg-1), and ketamine/midazolam (51.4 mL min-1 kg-1) regimens resulted in hepatosplanchnic blood flows of intermediate magnitude. The observed marked differential effects of the anaesthetic regimens upon renal and hepatosplanchnic blood flows may dramatically influence drug disposition in the experimental animal, and be of significance to laboratory pharmacokinetic studies in which anaesthesia is used.

Influence of pentobarbital and chloralose on metabolic and hemodynamic changes in liver ischemia

Hemodynamic and metabolic consequences of a 90-minute period of liver ischemia followed by 120 minutes of reperfusion were studied in rats that were awake during most of the experiment and in rats anesthetized with either pentobarbital (40 mg/kg body weight) or chloralose (30 mg/kg X hour) during the complete length of the experiment. Ischemia was induced by occluding the blood vessels to the left and median liver lobes with a small vascular clamp, which was removed after 90 minutes. Protein synthesis rate was determined by measuring incorporation rate of 14C-leucine into protein in incubated liver slices. At the end of the ischemic period, adenosine triphosphate levels in liver tissue and protein synthesis rate were reduced by 80% to 90%, with no significant differences among groups. During reperfusion, energy levels and protein synthesis rate remained depressed in the anesthetized animals, but improved, although not to normal values, in the awake rats. Hepatic tissue water increased during ischemia, probably reflecting hepatocellular membrane injury. The increase in hepatic tissue water was more pronounced in the chloralose group than in the other groups of rats. During reperfusion hepatic tissue water remained increased in the anesthetized rats but was normalized in the awake group. Mean arterial blood pressure was stable during ischemia and reperfusion in the pentobarbital anesthetized rats, while a progressive decrease in blood pressure during the experiment was noted in the chloralose group. The results suggest that hemodynamic and metabolic responses to liver ischemia and reperfusion can be influenced by anesthetics. Chloralose may be less suitable than pentobarbital for anesthesia when liver ischemia is inflicted.

Analgesia for appendectomy: comparison of fentanyl and alfentanil in children

During etomidate-N2O vecuronium anaesthesia for appendectomy, three groups of 13 children received fentanyl as a 10 micrograms.kg-1 loading dose and 2 micrograms.kg-1 increments in Group F, alfentanil as a 100 micrograms.kg-1 initial loading dose and either 20 micrograms.kg-1 increments in Group AB or 1 microgram.kg-1.min-1 continuous infusion in Group AI. On the basis of intraoperative heart rate changes, the opioid regimen was less efficient in Group AB (P less than 0.05). Based upon equianalgesic cumulative dosage, the alfentanil/fentanyl potency ratio was in the range of 1/10 to 1/13. The awakening time was similar in all groups, as were the duration of postoperative analgesia, the incidence of postoperative pain and the incidence of nausea and vomiting. We conclude that high-dose alfentanil is as efficient as fentanyl for intra and postoperative analgesia in children undergoing appendectomy.

Effects of ketamine on liver blood flow and hepatic oxygen consumption. Studies in the anaesthetised greyhound

The effects of three increasing doses of ketamine on the blood flow to, and oxygen consumption of, the liver, were studied in seven anaesthetised greyhounds. Hepatic arterial and portal venous blood flows were measured continuously using electromagnetic flow probes, and mean arterial pressure and cardiac output monitored as appropriate. Ketamine, even at the highest dose, had little effect on the blood flow to the liver: hepatic arterial blood flow and portal venous blood flow did not differ significantly from their baseline values. However, the oxygen delivery to the liver decreased due, probably, to an increase in oxygen consumption by the pre-portal organs.