Assessing the depth of isoflurane anaesthesia during cardiopulmonary bypass

Extracorporeal Membrane Oxygenation Use in Thoracic Surgery

This narrative review is focused on the application of extracorporeal membrane oxygenation (ECMO) in thoracic surgery, exclusive of lung transplantation. Although the use of ECMO in this indication is still rare, it allows surgery to be performed in patients where conventional ventilation is not feasible-especially in single lung patients, sleeve lobectomy or pneumonectomy and tracheal or carinal reconstructions. Comparisons with other techniques, various ECMO configurations, the management of anticoagulation, anesthesia, hypoxemia during surgery and the use of ECMO in case of postoperative respiratory failure are reviewed and supported by two cases of perioperative ECMO use, and an overview of published case series.

Central inhibition prevents the in vivo acute toxicity of harmine in mice

BACKGROUND

Harmine is a β-carboline alkaloid that displays antidepressant, antitumor and other pharmacological effects. However, the strong toxic effects limit its clinical application, and should be first considered.

PURPOSE

To evaluate the in vivo toxicity of harmine and explore intervention strategies against its toxicity.

METHODS

The in vivo toxicity of harmine was assessed from the symptoms, biochemical indices, and cardiovascular effects in mice. The intervention experiments were performed by using anesthetics, central drugs, and peripheral anticholinergics.

RESULTS

The acute toxicity of harmine is significantly dose-dependent and the median lethal dose is 26.9 mg/kg in vivo. The typical symptoms include convulsion, tremor, jumping, restlessness, ataxia, opisthotonos, and death; it also changes cardiovascular function. The anesthetics improved the survival rate and abolished the symptoms after harmine poisoning. Two central inhibitors, benzhexol and phenytoin sodium, uniformly improved the survival rates of mice poisoned with harmine. The peripheral anticholinergics didn't show any effects.

CONCLUSION

Harmine exposure leads to central neurological symptoms, cardiovascular effects and even death through direct inhibition of the central AChE activity, where the death primarily comes from central neurological symptoms and is cooperated by the secondary cardiovascular collapse. Central inhibition prevents the acute toxicity of harmine, and especially rapid gaseous anesthetics such as isoflurane, might have potential application in the treatment of harmine poisoning.

Volatile Anesthesia Versus Total Intravenous Anesthesia During Cardiopulmonary Bypass: A Narrative Review on the Technical Challenges and Considerations

The Mortality in Cardiac Surgery Randomized Controlled Trial of Volatile Anesthetics (MYRIAD) demonstrated that cardiac surgery with either volatile anesthesia or intravenous anesthesia techniques can be comparable with respect to morbidity and mortality. Maintaining anesthesia during cardiopulmonary bypass (CPB) with either approach requires appreciation of the nuances that are unique to each. This narrative review addresses these technical challenges and other considerations.

A Comparison of the Arterial Blood Concentration of Isoflurane During Cardiopulmonary Bypass Between 2 Polypropylene Oxygenators

OBJECTIVE

The primary objective was to compare arterial blood concentration of isoflurane during cardiopulmonary bypass (CPB) between 2 polypropylene oxygenators of different designs. Secondary objectives were to compare levels of Bispectral Index Score (BIS) during CPB between the 2 oxygenators and to examine the relationships between oxygenator exhaust and arterial blood concentrations of isoflurane and BIS.

DESIGN

Single, blinded, randomized control trial.

SETTING

Teaching hospital.

PARTICIPANTS

Twenty-five patients undergoing cardiac surgery with CPB.

INTERVENTIONS

Subjects were randomly assigned (1:1) to Inspire 8F (Sorin) or Affinity Fusion (Medtronic) oxygenators.

MEASUREMENTS AND MAIN RESULTS

The mean arterial blood concentration in the Inspire 8F (Sorin) group was 59 (standard deviation [SD] 23) µg/mL, compared with 53 (SD 17) µg/mL in the Affinity Fusion (Medtronic) group with a nonsignificant mean difference of 6 (95% confidence interval = -11, 22) µg/mL (t[23] = 0.676, p = 0.50). No significant difference in BIS was found between the groups (p = 0.896). Moderate and strong, negative correlations respectively, were found between arterial and oxygenator exhaust correlations and BIS (r = -0.472, p < 0.05; r = -0.812, p < 0.001). A strong, positive correlation was found between arterial and exhaust isoflurane concentration (r = 0.810, p < 0.0005).

CONCLUSIONS

No significant difference in arterial blood concentration of isoflurane or BIS was found between the Inspire 8F (Sorin) and Affinity Fusion (Medtronic) oxygenators. A significant positive correlation was found between arterial blood and oxygenator exhaust concentrations of isoflurane, as well as significant negative correlations between both arterial and oxygenator exhaust concentrations of isoflurane and BIS.

The effect of hypothermia during cardiopulmonary bypass on three electro-encephalographic indices assessing analgesia and hypnosis during anesthesia: consciousness index, nociception index, and bispectral index

The depth of anesthesia is commonly assessed in clinical practice by the patient's clinical signs. However, during cardiopulmonary bypass and hypothermia, common symptoms of nociception such as tachycardia, hypertension, sweating, or movement have low sensitivity and specificity in the description of the patient nociception and hypnosis, in particular, detecting nociceptive stimuli. Better monitoring of the depth of analgesia during hypothermia under cardiopulmonary bypass will avoid underdosage or overdosage of analgesia, especially opioids. Induced hypothermia has a multifactorial effect on the level of analgesia and hypnosis. Thermoregulatory processes appear essential for the activation of analgesic mechanisms, ranging from a physiological strong negative affiliation between nerve conduction velocity and temperature, until significant repercussions on the pharmacological dynamics of the analgesic drugs, the latter decreasing the clearance rate with a subsequent increase in the effect-site concentrations. Under the hypothesis that deep hypothermia induces massive effects on the analgesia and hypnosis levels of the patient, we studied whether hypothermia effects were mirrored by several neuromonitoring indices: two hypnosis indices, consciousness index and bispectral index, and a novel nociception index designed to evaluate the analgesic depth. In this clinical trial, 39 patients were monitored during general anesthesia with coronary atherosclerosis cardiopathy who were elective for on-pump coronary artery bypass graft surgery under hypothermia. The changes and correlation between the consciousness index, bispectral index, and nociception index with respect to the temperature were compared in different timepoints at basic state, during cardiopulmonary bypass and after cardiopulmonary bypass. While the three neuromonitoring indices showed significant correlations with respect to the temperature, the nociception index and consciousness index showed the strongest sensitivities, indicating that these two indices could be an important means of intraoperative neuromonitoring during induced hypothermia under cardiopulmonary bypass.

The depth of anaesthesia associated with the administration of isoflurane 2.5% during cardiopulmonary bypass

BACKGROUND

Administering isoflurane 2.5% into the oxygenator during cardiopulmonary bypass results in no patient movement. However, doing so may result in an excessive depth of anaesthesia particularly, when hypothermia is induced. Bispectral index and arterial blood and oxygenator exhaust concentrations of volatile anaesthetics should be related to depth of anaesthesia. The primary aim of this study was to measure the depth of anaesthesia using bispectral index, resulting from administering isoflurane 2.5% into the oxygenator during cardiopulmonary bypass, and secondary aims were to examine the relationships between blood and oxygenator exhaust isoflurane concentrations and bispectral index.

METHODS

Arterial and mixed-venous blood samples were aspirated at three time points during cardiopulmonary bypass and measured for isoflurane concentration using mass spectrometry. Simultaneously, oxygenator exhaust isoflurane concentration, nasopharyngeal temperature and bispectral index were recorded.

RESULTS

When averaged across the three time points, all patients had a bispectral index score below 40 (binomial test, p < 0.001). There were no significant correlations between bispectral index score and arterial or mixed-venous blood isoflurane concentrations (r = -0.082, p = 0.715; r = -0.036, p = 0.874) and oxygenator exhaust gas concentration of isoflurane (r = -0.369, p = 0.091).

CONCLUSION

When 2.5% isoflurane was administered into the sweep gas supply to the oxygenator during cardiopulmonary bypass, all patients experienced a bispectral index score less than 40 and no significant relationship was found between either arterial or mixed-venous blood or oxygenator exhaust concentrations of isoflurane and bispectral index.