Effects of propofol on haemodynamics and on regional blood flows in dogs submitted or not to a volaemic expansion

Evaluation of renal injury caused by acute volume replacement with hydroxyethyl starch 130/0.4 or Ringer's lactate solution in pigs

This work aimed to evaluate the effects on renal tissue integrity after hydroxyethyl starch (HES) 130/0.4 and Ringer's lactate (RL) administration in pigs under general anesthesia after acute bleeding. A total of 30 mL/kg of blood were passively removed from the femoral artery in two groups of Large White pigs, under total intravenous anesthesia with propofol and remifentanil. After bleeding, Group 1 (n = 11) received RL solution (25 mL/kg) and Group 2 (n = 11) received HES 130/0.4 solution (20 mL/kg). Additionally, Group 3 (n = 6) was not submitted to bleeding or volume replacement. Pigs were euthanized and kidneys were processed for histopathological and immunohistochemical analyses. Minimal to moderate glomerular, tubular, and interstitial changes, as well as papillary necrosis, were observed in all experimental groups. Pre-apoptosis and apoptosis indicators were higher in pigs that received HES 130/0.4, indicating a higher renal insult. Both HES 130/0.4 and RL administration may cause renal injury, although renal injury may be more significant in pigs receiving HES 13/0.4. Results also suggest that total intravenous anesthesia with propofol and remifentanil may cause renal injury, and this effect can be dose related.

Microvascular perfusion in cardiac arrest: a review of microcirculatory imaging studies

Cardiac arrest represents a leading cause of mortality and morbidity in developed countries. Extracorporeal cardiopulmonary resuscitation (ECPR) increases the chances for a beneficial outcome in victims of refractory cardiac arrest. However, ECPR and post-cardiac arrest care are affected by high mortality rates due to multi-organ failure syndrome, which is closely related to microcirculatory disorders. Therefore, microcirculation represents a key target for therapeutic interventions in post-cardiac arrest patients. However, the evaluation of tissue microcirculatory perfusion is still demanding to perform. Novel videomicroscopic technologies (Orthogonal polarization spectral, Sidestream dark field and Incident dark field imaging) might offer a promising way to perform bedside microcirculatory assessment and therapy monitoring. This review aims to summarise the recent body of knowledge on videomicroscopic imaging in a cardiac arrest setting and to discuss the impact of extracorporeal reperfusion and other therapeutic modalities on microcirculation.

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.

Anesthesia and the Microcirculation

There is increasing evidence that the microcirculation and its regulation are severely compromised during many pathological conditions, such as hemorrhage, sepsis, or trauma. The effects of anesthetic agents on macrohemodynamics were investigated intensively in the last several decades. Research regarding modern anesthetics and anesthesia techniques has increased knowledge regarding the nonanesthetic effects of anesthetic agents, including those on organ perfusion and the microcirculation. Alterations in microvascular reactivity, nitric oxide pathways, and cytokine release are presumably the main mechanisms of anesthetic-induced tissue perfusion changes. This review summarizes current methods of microcirculatory status assessment and current knowledge regarding the microcirculatory effects of intravenous and potent volatile anesthetics and anesthesia-related techniques under both normal and pathophysiological conditions.

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.

Effect of intraoperative intravenous crystalloid infusion on postoperative nausea and vomiting after gynaecological laparoscopy: comparison of 30 and 10 ml kg(-1)

BACKGROUND

I.V. fluid administration has been shown to reduce postoperative nausea and vomiting (PONV). The optimum dose is unknown. We tested the hypothesis that administration of i.v. crystalloid of 30 ml kg(-1) would reduce the incidence of PONV compared with 10 ml kg(-1) of the same fluid.

METHODS

A total of 141 ASA I female patients undergoing elective gynaecological laparoscopy were randomized, in double-blind fashion, to receive either 10 ml kg(-1) (n=71; CSL-10 group) or 30 ml kg(-1) (n=70; CSL-30 group) of i.v. compound sodium lactate (CSL).

RESULTS

In the first 48 h after anaesthesia, the incidence of vomiting was lower in the CSL-30 group than in the CSL-10 group (8.6% vs 25.7%, P=0.01). Anti-emetic use was less in the CSL-30 group at 0.5 h (2.9% vs 14.3%, P=0.04). The incidence of severe nausea was significantly reduced in the treatment group at awakening (2.9% vs 15.7%, P=0.02), 2 h (0.0% vs 8.6%, P=0.04) and cumulatively (5.7% vs 27.1%, P=0.001). The numbers needed to treat to prevent vomiting, severe nausea and antiemetic use in the first 48 h were 6, 5 and 6, respectively.

CONCLUSION

I.V. administration of CSL 30 ml kg(-1) to healthy women undergoing day-case gynaecological laparoscopy reduced the incidence of vomiting, nausea and anti-emetic use when compared with CSL 10 ml kg(-1).

The effects of systolic arterial blood pressure variations on postoperative nausea and vomiting

In this clinical study, we tested the hypothesis that a marked systolic blood pressure decrease >35% (DeltaSBP >35%) from preanesthetic baseline during the induction and maintenance of anesthesia is associated with more postoperative nausea and vomiting (PONV). In 300 ASA physical status I and II women undergoing elective gynecological surgery with general anesthesia, the maximum DeltaSBP during the induction as well as maintenance of general anesthesia were calculated. Observers blinded to hemodynamic variables assessed the incidence of PONV. The overall incidence of nausea (visual analog scale >4) and vomiting within the immediate observation period (0-2 h) was 39% and 25%, respectively. Frequency of nausea and vomiting in the late observation period was 21% and 9%, respectively. Women with a DeltaSBP >35% during the induction of anesthesia suffered from a more frequent incidence of PONV within the immediate (57% versus 35% and 41% versus 22%, respectively; P < 0.01) and within the late observation period (33% versus 18% and 19% versus 7%, respectively; P < or = 0.01). In women with a DeltaSBP >35% during maintenance of anesthesia, a more frequent incidence of nausea within the immediate observation period (53% versus 36%; P < 0.05) was found. We conclude that a maximum DeltaSBP >35% during the anesthetic induction is associated with an increased incidence of PONV after gynecological surgery during general anesthesia.

IMPLICATIONS

A prospective clinical investigation revealed that a marked systolic blood pressure decrease >35% (DeltaSBP >35%) during the induction of general anesthesia is associated with an increased incidence of postoperative nausea and vomiting (PONV). The association between a DeltaSBP >35% during maintenance of general anesthesia and PONV is less pronounced.