Effects of Volatile Anesthetics on Oral Tissue Blood Flow in Rabbits: A Comparison Among Isoflurane, Sevoflurane, and Desflurane

A review of recent advances in anesthetic drugs for patients undergoing cardiac surgery

Inducing and maintaining general anesthesia requires a diverse set of medications. Currently, heart surgery anesthetic management does not adhere to any one standard protocol or set of drugs. To ensure steady circulatory function while providing sufficient sedation, anesthetic medications are carefully selected for cardiovascular operations. Among the opioids used most often in cardiac surgery are fentanyl, sufentanil, and remifentanil. As a cardiac anesthesiologist, your key responsibilities will be to maintain your patient's blood pressure (BP) and oxygen levels, reduce the frequency and intensity of ischemia events, and make it easy for them to get off of cardiopulmonary bypass (CPB) and supplemental oxygen fast. Additionally, new knowledge gaps have been identified as a result of developments in cardiac anesthetics, which must be addressed. The goal of the most recent developments in cardiac anesthesia has been to decrease risks and increase accuracy in patient outcomes during cardiac surgeries. Furthermore, new methods and tools are contributing to the evolution of cardiovascular anesthesia toward a more dynamic, patient-centered approach, with an eye on boosting safety, decreasing complications, and facilitating better recovery for patients. New medications and methods have emerged in the field of anesthetic pharmacology, aiming to improve anesthesia management, particularly for patients who have cardiovascular disease. Optimal cardiovascular stability, fewer side effects, and enhanced surgical recovery are achieved by use of these medications. We have reviewed all the different kinds of cardiac anesthetic techniques and medications in this research. We have also examined the many new anesthetic medicines that have been produced and used for individuals with cardiovascular issues. Next, we covered prospects in the realm of cardiovascular anesthesia and novel cardiac anesthetic drugs.

Involvement of α- and β-Adrenergic Receptors in Skeletal Muscle Blood Flow Changes During Hyper-/Hypocapnia in Anesthetized Rabbits

OBJECTIVE

This study investigated the involvement of α1- and β2-adrenergic receptors in skeletal muscle blood flow changes during variations in ETCO2.

METHODS

Forty Japanese White rabbits anesthetized with isoflurane were randomly allocated to 1 of 5 groups: phentolamine, metaproterenol, phenylephrine, butoxamine, and atropine. Heart rate (HR), systolic blood pressure (SBP), common carotid artery blood flow (CCBF), masseter muscle tissue blood flow (MBF), and quadriceps muscle tissue blood flow (QBF) were recorded and analyzed at 3 periods: (1) baseline, (2) during hypercapnia (phentolamine and metaproterenol groups) or hypocapnia (phenylephrine, butoxamine, and atropine groups), and (3) during or after receiving vasoactive agents.

RESULTS

MBF and QBF decreased during hypercapnia. The decrease in MBF was smaller than that in QBF. SBP and CCBF increased, while HR decreased. Both MBF and QBF recovered to their baseline levels after phentolamine administration. MBF became greater than its baseline level, while QBF did not fully recover after metaproterenol administration. MBF and QBF increased during hypocapnia. The increase rate in MBF was larger than that in QBF. HR, SBP, and CCBF did not change. Both MBF and QBF decreased to ∼90% to 95% of their baseline levels after phenylephrine or butoxamine administration. Atropine showed no effects on MBF and QBF.

CONCLUSION

These results suggest the skeletal muscle blood flow changes observed during hypercapnia and hypocapnia may mainly involve α1-adrenergic but not β2-adrenergic receptor activity.

Effects of Remifentanil on Cardiovascular Stimulation Caused by Local Anesthetic With Epinephrine: A Power Spectral Analysis

The objectives of this research were to investigate (a) what was the most effective infusion rate of remifentanil and (b) the degree to which sympathomimetic effects were involved with cardiovascular stimulation by using a power spectral analysis of heart rate variability (HRV). A total of 63 healthy individuals scheduled for sagittal split ramus osteotomy were enrolled and randomly allocated to 1 of 3 groups: remifentanil infusion rate of 0.1, 0.2, or 0.4 μg/kg/min. Anesthesia was maintained with remifentanil and propofol. Before the surgical procedure, 2% lidocaine containing 12.5 μg/mL epinephrine was administered in the surgical field for local anesthesia. Systolic blood pressure (SBP), heart rate (HR), low-frequency (LF) and high-frequency (HF) components in HRV power spectral analysis, and the LF/HF ratio were analyzed. Increases in SBP and HR were observed after local anesthesia in all 3 groups, but no significant differences were observed between the groups. Remifentanil infusion at 0.1 μg/kg/min may be appropriate to minimize cardiovascular stimulation caused by exogenous epinephrine from local anesthesia. Although a rise in the LF/HF ratio was observed after local anesthesia in all groups, no relationship was observed between the cardiovascular changes and the increase in LF/HF ratio. This suggests that sympathomimetic effects are involved to a lesser extent with the cardiovascular stimulation caused by exogenous epinephrine.

Remifentanil infusion during desflurane anesthesia reduces tissue blood flow while maintaining blood pressure and tissue oxygen tension in the masseter muscle and mandibular bone marrow

The aim of this study was to compare changes in tissue blood flow and tissue oxygen tension in the masseter muscle and mandibular bone marrow induced by remifentanil under desflurane or sevoflurane anesthesia. Eleven male tracheotomized Japan White rabbits were anesthetized with desflurane or sevoflurane under mechanical ventilation. The order of the inhalation of desflurane or sevoflurane was randomized. Desflurane or sevoflurane was administered at 1.0 minimum alveolar concentration and remifentanil was infused at 0.4 µg/kg/min. Observed variables included heart rate (HR), blood pressure (BP), common carotid artery blood flow (CCBF), mandibular bone marrow tissue blood flow (BBF), masseter muscle tissue blood flow (MBF), mandibular bone marrow tissue oxygen tension (PbO₂), and masseter muscle tissue oxygen tension (PmO₂). Two way repeated measures ANOVA showed no interaction between volatile anesthetics and remifentanil infusion except for MBF. There were significant differences in HR, SBP, DBP, MAP and CCBF between desflurane and sevoflurane groups. There were also significant differences in HR, SBP, DBP, MAP, CCBF, BBF and PbO₂ before, during and after remifentanil infusion. Desflurane reduced tissue blood flow in the masseter muscle and mandibular bone marrow while better maintained HR and BP than sevoflurane. Under remifentanil infusion, although both anesthetics reduced tissue blood flow, tissue oxygen tension was maintained in masseter muscle and mandibular bone marrow.

Effects of anesthetics on microvascular reactivity measured by vascular occlusion tests during off-pump coronary artery bypass surgery: a randomized controlled trial

Microvascular function may be modulated by various anesthetics. Desflurane and propofol anesthesia have different effects on microvascular function. However, there are few reports on the effects of sevoflurane and desflurane on microvascular function during cardiac surgery. We compared the effects of sevoflurane and desflurane on microvascular reactivity, as measured by the vascular occlusion tests (VOTs) during off-pump coronary artery bypass (OPCAB) surgery. Patients undergoing OPCAB were eligible for study inclusion. Patients were excluded if they were unsuitable for treatment with volatile agents or the VOT, had renal failure or uncontrolled diabetes, or were pregnant. The enrolled patients were randomized to receive sevoflurane or desflurane during surgery. Tissue oxygen saturation (StO₂) dynamics during the VOT were measured at baseline (pre-anesthesia), pre-anastomosis, post-anastomosis of vessel grafts, and at the end of surgery. Macrohemodynamic variables, arterial blood gas parameters, and in-hospital adverse events were also evaluated. A total of 64 patients (32 in each group) were analyzed. StO₂ dynamics did not differ between the groups. Compared to baseline, StO₂ and the rate of recovery following vascular occlusion decreased at the end of surgery in both groups (adjusted p-value, < 0.001), and no group difference was observed. Macrohemodynamic variables, blood gas analysis results, and the rate of postoperative in-hospital adverse events were similar between the groups. Microvascular reactivity, as measured by the VOT during OPCAB, showed no difference between the sevoflurane and desflurane groups. Also, there were no group differences in macrohemodynamics or the rate of postoperative adverse events. TRIAL REGISTRATION : Clinicaltrials.gov, identifier NCT03209193; registered on July 3, 2017.

Effects of Stellate Ganglion Blockade on Muscle Blood Flow During Hypercapnia

This study investigated the effects of a unilateral stellate ganglion block (SGB) on ipsilateral and contralateral masseter muscle blood flow during permissive hypercapnia. Eight male Japanese white rabbits were anesthetized with isoflurane. Observed variables included heart rate (HR), blood pressure (BP), left common carotid artery blood flow (LCBF), left and right masseter muscle tissue blood flow (LMBF and RMBF), and left femoral quadriceps muscle tissue blood flow (LQBF). Variable measurements were taken at a baseline end-tidal carbon dioxide tension (EtCO2) of 40 mm Hg and repeated at an elevated EtCO2 of 60 mm Hg prior to and after administration of a left SGB. HR decreased, while systolic BP was elevated during hypercapnia and after the SGB. LCBF increased during hypercapnia and after the SGB. LMBF and RMBF decreased to 75% and LQBF decreased to 60% of their respective baseline values during hypercapnia. After the SGB, LMBF was restored, reapproximating its baseline, but RMBF and LQBF further decreased to 55 and 45% of their respective baseline values. In conclusion, unilateral SGB restored the ipsilateral masseter muscle blood flow that had been reduced during hypercapnia. In contrast, the SGB exacerbated the hypercapnia-induced reduction in blood flows in the contralateral masseter muscle and the femoral quadriceps muscle.

Decreases in Oral Tissue Blood Flow Induced by Remifentanil Are Not Accompanied by Deterioration of Oral Tissue Oxygen Tension in Rabbits

PURPOSE

The purpose of this study was to investigate the effects of remifentanil infusion on tissue blood flow and tissue oxygen tension in the mandibular bone marrow and masseter muscle in rabbits. In addition, changes in tissue oxygen consumption in those tissues during remifentanil infusion were investigated.

MATERIALS AND METHODS

Sixteen male tracheotomized Japanese White rabbits were anesthetized with sevoflurane under mechanical ventilation. Under oxygen and air inhalation, fraction of inspiratory oxygen was set at 0.4 and remifentanil was infused at a rate of 0.4 μg ∙ kg^-1 ∙ min^-1. Measurements were performed before remifentanil infusion, 20 minutes after the start of remifentanil infusion, and 20 and 60 minutes after the completion of remifentanil infusion (n = 8). The observed variables included heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), mandibular bone marrow tissue blood flow (BBF), masseter muscle tissue blood flow (MBF), mandibular bone marrow tissue oxygen tension (PbO₂), and masseter muscle tissue oxygen tension (PmO₂). Another 8 rabbits were observed for arterial pH, lactate, base excess (BE), and tissue oxygen consumption in the region from which the retromandibular vein received venous blood. Measurements were performed before remifentanil infusion and 20 minutes after the start of remifentanil infusion.

RESULTS

HR, SBP, DBP, MAP, BBF, and MBF decreased during remifentanil infusion. PbO₂ increased 20 minutes after remifentanil infusion and returned to almost the baseline value 60 minutes after remifentanil infusion. PmO₂ did not change throughout the experiment. The difference between the arterial oxygen content of the femoral artery and the venous oxygen content of the retromandibular vein decreased during remifentanil infusion. Arterial pH, lactate, and BE did not change during remifentanil infusion.

CONCLUSIONS

Remifentanil decreased BBF and MBF but did not decrease PbO₂ and PmO₂. It is suggested that tissue oxygen consumption decreased during remifentanil infusion.

Remifentanil decreases oral tissue blood flow while maintaining internal carotid artery blood flow during sevoflurane anesthesia in rabbits

The aim of this study was to investigate the effect of remifentanil infusion on oral tissue blood flow including submandibular gland tissue blood flow (SBF) and internal carotid artery blood flow (ICBF) in rabbits during sevoflurane anesthesia. Twelve male Japan White rabbits were anesthetized with sevoflurane and remifentanil. Remifentanil was infused at 0.2 and 0.4 µg/kg/min. Measurements included circulatory variables, common and external carotid artery blood flow (CCBF, ECBF), ICBF, tongue mucosal blood flow (TMBF), masseter muscle tissue blood flow (MBF), mandibular bone marrow tissue blood flow (BBF), tongue muscle tissue blood flow (TBF) and SBF. Vascular resistances for each tissue, including the tongue mucosa, masseter muscle, mandibular bone marrow, tongue muscle and submandibular gland, were calculated by dividing the mean arterial pressure by the respective tissue blood flow. Remifentanil infusion decreased oral tissue blood flow and circulatory variables. CCBF, ECBF and ICBF did not change. The calculated vascular resistance in each oral tissue, except for the tongue mucosa, increased in an infusion-rate-dependent manner. These results showed that remifentanil infusion reduced TMBF, MBF, BBF, TBF and SBF in an infusion-rate-dependent manner without affecting ICBF under sevoflurane anesthesia.

Impact of Epinephrine Contained in Local Anesthetic Solution on Serum Lactate Level During Orthognathic Surgery

PURPOSE

There have been many discussions of a relation between endogenous and exogenous epinephrine and hyperlactatemia. This study aimed to identify the impact of epinephrine contained in a local anesthetic solution on serum lactate levels in patients who underwent orthognathic surgery.

MATERIALS AND METHODS

This study was a retrospective record review of cases of maxillary and mandibular osteotomy at the Tokyo University Hospital (Tokyo, Japan) from January 2006 through December 2014. One hundred ninety-three patients were enrolled in this study.

RESULTS

The maximum intraoperative serum lactate level was 22.3 ± 14.7 mg/dL. Of 193 patients, 91 showed an intraoperative serum lactate level that was higher than the normal maximum of 19.8 mg/dL (2.2 mmol/L), and 16 of these had a level that was at least 40 mg/dL (≥4.49 mmol/L). Multiple logistic regression analysis showed 2 factors that could increase the serum lactate level: the amount of epinephrine contained in the local anesthetic solution injected into the oral cavity (odds ratio [OR] = 1.014; 95% confidence interval [CI], 1.006-1.022; P = .0001) and the absence of intraoperative treatment with propranolol (OR, 0.105; 95% CI, 0.019-0.434; P = .0013). Patients with severe serum lactate concentrations (ie, ≥40 mg/dL [≥4.49 mmol/L]) had slight metabolic acidosis. All patients survived 90 days. The number of postoperative hospitalization days for patients with severe serum lactate concentrations was 12.8 ± 2.6 days and that for patients without severe serum lactate concentration was 16.0 ± 8.6 days.

CONCLUSION

Increases in intraoperative serum lactate levels during orthognathic surgery are associated, at least in part, with increased aerobic glycolysis because of β₂-adrenergic signaling. Lactate increase caused by epinephrine contained in a local anesthetic solution does not result in a poor postoperative outcome.