Neuroprotective effects of selective β-1 adrenoceptor antagonists, landiolol and esmolol, on transient forebrain ischemia in rats; a dose-response study

Early Intravenous Beta-Blockade with Esmolol in Adults with Severe Traumatic Brain Injury (EBB-TBI): Protocol for a Phase 2a Intervention Design Study

Traumatic brain injury is a leading cause of death and disability worldwide. Interventions that mitigate secondary brain injury have the potential to improve outcomes for patients and reduce the impact on communities and society. Increased circulating catecholamines are associated with worse outcomes and there are supportive animal data and indications in human studies of benefit from beta-blockade after severe traumatic brain injury. Here, we present the protocol for a dose-finding study using esmolol in adults commenced within 24 h of severe traumatic brain injury. Esmolol has practical advantages and theoretical benefits as a neuroprotective agent in this setting, but these must be balanced against the known risk of secondary injury from hypotension. The aim of this study is to determine a dose schedule for esmolol, using the continual reassessment method, that combines a clinically significant reduction in heart rate as a surrogate for catecholamine drive with maintenance of cerebral perfusion pressure. The maximum tolerated dosing schedule for esmolol can then be tested for patient benefit in subsequent randomized controlled trials.Trial registration ISRCTN, ISRCTN11038397, registered retrospectively 07/01/2021 https://www.isrctn.com/ISRCTN11038397.

Beta-Adrenergic Blockade in Critical Illness

Catecholamine upregulation is a core pathophysiological feature in critical illness. Sustained catecholamine β-adrenergic induction produces adverse effects relevant to critical illness management. β-blockers (βB) have proposed roles in various critically ill disease states, including sepsis, trauma, burns, and cardiac arrest. Mounting evidence suggests βB improve hemodynamic and metabolic parameters culminating in decreased burn healing time, reduced mortality in traumatic brain injury, and improved neurologic outcomes following cardiac arrest. In sepsis, βB appear hemodynamically benign after acute resuscitation and may augment cardiac function. The emergence of ultra-rapid βB provides new territory for βB, and early data suggest significant improvements in mitigating atrial fibrillation in persistently tachycardic septic patients. This review summarizes the evidence regarding the pharmacotherapeutic role of βB on relevant pathophysiology and clinical outcomes in various types of critical illness.

Esmolol during cardiopulmonary resuscitation reduces neurological injury in a porcine model of cardiac arrest

Primary vasopressor efficacy of epinephrine during cardiopulmonary resuscitation (CPR) is due to its α-adrenergic effects. However, epinephrine plays β1-adrenergic actions, which increasing myocardial oxygen consumption may lead to refractory ventricular fibrillation (VF) and poor outcome. Effects of a single dose of esmolol in addition to epinephrine during CPR were investigated in a porcine model of VF with an underlying acute myocardial infarction. VF was ischemically induced in 16 pigs and left untreated for 12 min. During CPR, animals were randomized to receive epinephrine (30 µg/kg) with either esmolol (0.5 mg/kg) or saline (control). Pigs were then observed up to 96 h. Coronary perfusion pressure increased during CPR in the esmolol group compared to control (47 ± 21 vs. 24 ± 10 mmHg at min 5, p < 0.05). In both groups, 7 animals were successfully resuscitated and 4 survived up to 96 h. No significant differences were observed between groups in the total number of defibrillations delivered prior to final resuscitation. Brain histology demonstrated reductions in cortical neuronal degeneration/necrosis (score 0.3 ± 0.5 vs. 1.3 ± 0.5, p < 0.05) and hippocampal microglial activation (6 ± 3 vs. 22 ± 4%, p < 0.01) in the esmolol group compared to control. Lower circulating levels of neuron specific enolase were measured in esmolol animals compared to controls (2[1-3] vs. 21[16-52] ng/mL, p < 0.01). In this preclinical model, β1-blockade during CPR did not facilitate VF termination but provided neuroprotection.

Effects of β1-adrenergic receptor blockade on the cerebral microcirculation in the normal state and during global brain ischemia/reperfusion injury in rabbits

Background

Although recent studies using experimental models of ischemic brain injury indicate that systemically-administered β₁-blockers have potential protective effects on the cerebrovascular system, the precise mechanisms remain unclear. In addition to their cardiovascular effects, water-soluble β₁-blockers can pass the blood–brain barrier and may exert their vascular action on cerebral microvessels. The aim of this study was to investigate the direct effects of β₁-blockade on the cerebral microvasculature both in the normal state and ischemia/reperfusion state using the cranial window method.

Methods

The closed cranial window method was used to visualize the cerebral microcirculation and changes in the pial arteriole diameter in adult male rabbits. In the first experiment, various concentrations of the selective β₁-blocker landiolol were administered into the cranial window to evaluate the dose-response. In the second experiment, the effect of β₁-blockade on the brain during ischemic/reperfusion injury was investigated. Global brain ischemia/reperfusion was induced by clamping the brachiocephalic, left common carotid, and left subclavian arteries for 15 min. Either landiolol or artificial cerebrospinal fluid was infused 5 min after initiation of ischemia through 120 min after reperfusion. Pial arteriole diameter and hemodynamic and physiological parameters were recorded before ischemia, during ischemia, and 5, 10, 20, 40, 60, 80, 100, and 120 min after reperfusion.

Results

In the first experiment, topical administration of landiolol at higher concentrations produced slight pial arteriole dilation (10^− 8 mol/L: 4.3 ± 3.4%, 10^− 6 mol/L: 8.0 ± 5.8%, 10^− 4 mol/L: 7.3 ± 4.0%). In the second experiment, the topical administration of landiolol significantly dilated the pial arteriole diameters during ischemia/reperfusion injury (ischemia: 30.6 ± 38.6%, 5 min: 47.3 ± 42.2%, 10 min: 47.8 ± 34.2%, 20 min: 38.0 ± 39.0%). There were no statistical differences in hemodynamic and physiological parameters between the landiolol and control groups.

Conclusions

The blockade of β₁-adrenergic receptors induced significant vasodilation of pial arterioles during ischemia/reperfusion injury. By contrast, only a slight dilation of the arterioles was observed in the normal state, indicating that ischemic cerebral microvessels are more susceptible to the vasodilatory effect induced by selective blockade of β₁-adrenergic receptors than normal microvessels.

Successful Management of Fulminant Guillain-Barré Syndrome and Its Complications

A 3-year-old girl presented with muscle weakness of her limbs and trunk 6 days after developing symptoms of common cold. Two days later, she experienced respiratory arrest with a Glasgow Coma Scale score of 3, necessitating endotracheal intubation. Therefore, she was transferred to our hospital with suspected acute encephalopathy. Although no abnormalities were observed on brain and spinal magnetic resonance imaging and electroencephalography, peripheral nerve conduction velocity tests failed to evoke motor and sensory nerve action potentials. Thus, we gave a diagnosis of fulminant Guillain-Barré syndrome and initiated immunoglobulin therapy. On day 3 of admission, she developed sinus tachycardia that induced circulatory failure and oliguria, which was successfully treated with landiolol. Subsequently, we performed plasmapheresis followed by immunoglobulin and steroid pulse therapies. She was weaned off the mechanical ventilator by day 20 of admission, was ambulatory by day 44, and had completely recovered without any adverse sequelae by day 55. In conclusion, landiolol was effective for treating acute sinus tachycardia-induced circulatory failure and played a key role in saving the life of this patient.

The suppressive effects of landiolol administration on the occurrence of postoperative atrial fibrillation and tachycardia, and plasma IL-6 elevation in patients undergoing esophageal surgery: A randomized controlled clinical trial

STUDY OBJECTIVE

To determine whether perioperative landiolol administration suppresses postoperative atrial fibrillation (AF) and the plasma cytokines elevation in patients undergoing esophageal cancer surgery.

DESIGN

A prospective, randomized controlled trial.

SETTING

Akita University Hospital, Akita, Japan, from April 2012 to January 2015.

PATIENTS

Forty American Society of Anesthesiologists grade I-II patients undergoing elective esophagectomy.

INTERVENTIONS

Patients were randomly divided into two groups, landiolol group (landiolol: 5μg/kg/min) and control group (the same volume of covered saline). Landiolol or saline was infused continuously from the induction of anesthesia until next morning.

MEASUREMENTS

We examined the new onset of AF and sinus tachycardia, and measured plasma concentrations of cytokines (IL-1β, IL-6, IL-8, IL-10, and TNF-α) just before surgery, at the end of surgery, the next day, and 2days after surgery. Data (mean±SD) were analyzed using two-way ANOVA followed by the Bonferroni"s test for post hoc comparison; a P<0.05 was considered statistically significant.

MAIN RESULTS

Demographic data were similar between the landiolol and the control groups. The incidence of AF was significantly lower in the landiolol group (1/19=5.3%) compared with the control group (7/20=35%) as well as sinus tachycardia (landiolol group, 0/19=0% vs. control group, 5/20=25%). Plasma IL-6 level at the end of surgery was significantly lower in the landiolol group compared with the control group, but the other plasma cytokines levels were similar between the two groups during the entire study period.

CONCLUSIONS

Perioperative landiolol administration suppressed the incidence of new-onset of AF as well as sinus tachycardia, and the plasma IL-6 elevation in patients undergoing esophageal cancer surgery.

An intensive care approach to posterior reversible encephalopathy syndrome (PRES): An analysis of 7 cases

OBJECTIVE

The aim of this study was to retrospectively evaluate the intensive care unit treatments applied to obstetrics patients with a diagnosis of posterior reversible encephalopathy syndrome (PRES).

MATERIAL AND METHODS

The cases of 7 pregnant patients who had been diagnosed with PRES between July 2011 and July 2013 were retrospectively reviewed. The patients' clinical data, brain magnetic resonance imaging (MRI) images before and after treatment, and neuropsychological tests were evaluated.

RESULTS

Five out of 7 patients had eclampsia, 1 patient had severe preeclampsia, and 1 patient developed HELLP syndrome secondary to PRES. Calcium channel blockers and β-blockers were used as antihypertensive treatment. All patients were treated with parenteral magnesium sulfate. In addition, sodium thiopental was given to control sedation and convulsions in all patients except 1. The neurological and radiological findings of all cases treated in the intensive care unit improved.

CONCLUSION

Posterior reversible encephalopathy syndrome is a clinical condition with a multifactorial etiology and can result in different clinical findings. Radiological imaging techniques can be used for the diagnosis of PRES. Pregnancy and the postpartum period often lead to this syndrome. In some cases, PRES can cause irreversible neurological deficits or death. For patients with severe radiological findings, early diagnosis and thiopental infusion, in addition to treatment with antihypertensive agents and magnesium sulfate, may lead to quicker and more effective recovery from clinical manifestations. We suggest supplementation of standard treatment with early thiopental infusion.

Inhibition of brain swelling after ischemia-reperfusion by β-adrenergic antagonists: correlation with increased K+ and decreased Ca2+ concentrations in extracellular fluid

Infarct size and brain edema following ischemia/reperfusion are reduced by inhibitors of the Na⁺, K⁺, 2Cl⁻, and water cotransporter NKCC1 and by β₁-adrenoceptor antagonists. NKCC1 is a secondary active transporter, mainly localized in astrocytes, driven by transmembrane Na⁺/K⁺ gradients generated by the Na⁺,K⁺-ATPase. The astrocytic Na⁺,K⁺-ATPase is stimulated by small increases in extracellular K⁺ concentration and by the β-adrenergic agonist isoproterenol. Larger K⁺ increases, as occurring during ischemia, also stimulate NKCC1, creating cell swelling. This study showed no edema after 3 hr medial cerebral artery occlusion but pronounced edema after 8 hr reperfusion. The edema was abolished by inhibitors of specifically β₁-adrenergic pathways, indicating failure of K⁺-mediated, but not β₁-adrenoceptor-mediated, stimulation of Na⁺,K⁺-ATPase/NKCC1 transport during reoxygenation. Ninety percent reduction of extracellular Ca²⁺ concentration occurs in ischemia. Ca²⁺ omission abolished K⁺ uptake in normoxic cultures of astrocytes after addition of 5 mM KCl. A large decrease in ouabain potency on K⁺ uptake in cultured astrocytes was also demonstrated in Ca²⁺-depleted media, and endogenous ouabains are needed for astrocytic K⁺ uptake. Thus, among the ionic changes induced by ischemia, the decrease in extracellular Ca²⁺ causes failure of the high-K⁺-stimulated Na⁺,K⁺-ATPase/NKCC1 ion/water uptake, making β₁-adrenergic activation the only stimulus and its inhibition effective against edema.

Expression and functions of β1- and β2-adrenergic receptors on the bulbospinal neurons in the rostral ventrolateral medulla

The expression and effects of β-adrenergic receptors (β-ARs) on the neurons of the bulbospinal rostral ventrolateral medulla (RVLM) have been limitedly examined to date. The objective of this study was to examine the expression of β1- and β2-ARs on the bulbospinal RVLM neurons electrophysiologically and histologically. To directly investigate whether RVLM neurons display sensitivity to metoprolol (a β1-AR antagonist), dobutamine (a β1-AR agonist), butoxamine (a β2-AR antagonist), and salbutamol (a β2-AR agonist), we examined changes in the membrane potentials of the bulbospinal RVLM neurons using the whole-cell patch-clamp technique during superfusion of these drugs. During metoprolol superfusion, 16 of the 20 RVLM neurons were hyperpolarized, and 5 of the 6 RVLM neurons were depolarized during dobutamine superfusion. During butoxamine superfusion, 11 of the 16 RVLM neurons were depolarized, and all of the 8 RVLM neurons were hyperpolarized during salbutamol superfusion. These results suggest the expression of β1- and β2-ARs on the RVLM neurons. To determine the presence of β1- and β2-ARs histologically, immunofluorescence examination was performed. Five metoprolol-hyperpolarized neurons were examined for β1-AR and tyrosine hydroxylase (TH) immunoreactivity. All of the neurons displayed β1-AR immunoreactivity, whereas three of the neurons displayed TH immunoreactivity. All of the five RVLM neurons that became depolarized during metoprolol superfusion and hyperpolarized during butoxamine superfusion displayed β1- and β2-AR immunoreactivity. Our findings suggest that β1-AR antagonists or β2-AR agonists may decrease blood pressure through decreasing the activity of the bulbospinal RVLM neurons.