Effects of the AT1-selective angiotensin II antagonist, telmisartan, on hemodynamics and ventricular function after cardiopulmonary resuscitation in pigs

Optimum chest compression point might be located rightwards to the maximum diameter of the right ventricle: A preliminary, retrospective observational study

BACKGROUND

Some researchers have reported that applying compression closer to the maximum diameter of the left ventricle (Point_max.LV) is associated with worse clinical outcomes, challenging its traditional position as optimum compression point (Point_optimum). By locating the mid-sternum (the actual compression site) in terms of Point_max.LV and its right ventricular equivalent (Point_max.RV), we aimed to determine its optimum horizontal position associated with increased chances of return of spontaneous circulation (ROSC).

METHODS

A retrospective, cross-sectional study was performed at a university hospital from 2014 to 2019 on non-traumatic out-of-hospital cardiac arrest (OHCA) victims who underwent chest computed tomography. On absolute x-axis, we designated the x-coordinate of the mid-sternum (x_mid-sternum) as 0 and leftward direction as positive. Re-defining the x-coordinate of Point_max.RV and Point_max.LV as 0 and 1 interventricular unit (IVU), respectively, we could convert x_mid-sternum to "-x_max.RV/(x_max.LV - x_max.RV) (IVU)." Using multiple logistic regression analysis, we investigated whether this converted x_mid-sternum was associated with clinical outcomes, adjusting core elements of the Utstein template.

RESULTS

Among 887 non-traumatic OHCA victims, 124 [64.4 ± 16.7 years, 43 women (34.7%)] were enrolled. Of these, 80 (64.5%) exhibited ROSC. X_mid-sternum ranging from -1.71 to 0.58 (-0.36 ± 0.38) IVU was categorised into quintiles: <-0.60, -0.60 to -0.37, -0.37 to -0.22, -0.22 to -0.07 and ≥-0.07 (reference) IVU. The first quintile was positively associated with ROSC (odds ratio [95% confidence interval], 9.43 [1.44, 63.3]).

CONCLUSION

Point_optimum might be located far rightwards to Point_max.RV, challenging the traditional assumption identifying Point_optimum as Point_max.LV.

Erythropoietin alleviates post-resuscitation myocardial dysfunction in rats potentially through increasing the expression of angiotensin II receptor type 2 in myocardial tissues

Activation of renin-angiotensin system (RAS) is one of the pathological mechanisms associated with myocardial ischemia-reperfusion injury following resuscitation. The present study aimed to determine whether erythropoietin (EPO) improves post‑resuscitation myocardial dysfunction and how it affects the renin‑angiotensin system. Sprague‑Dawley rats were randomly divided into sham, vehicle, epinephrine (EP), EPO and EP + EPO groups. Excluding the sham group, all groups underwent cardiopulmonary resuscitation (CPR) 4 min after asphyxia‑induced cardiac arrest (CA). EP and/or EPO was administrated by intravenous injection when CPR began. The results demonstrated that the vehicle group exhibited lower mean arterial pressure, left ventricular systolic pressure, maximal ascending rate of left ventricular pressure during left ventricular isovolumic contraction and maximal descending rate of left ventricular pressure during left ventricular isovolumic relaxation (+LVdP/dt max and ‑LVdP/dt max, respectively), and higher left ventricular end‑diastolic pressure, compared with the sham group following return of spontaneous circulation (ROSC). Few significant differences were observed concerning the myocardial function between the vehicle and EP groups; however, compared with the vehicle group, EPO reversed myocardial function indices following ROSC, excluding‑LVdP/dt max. Serum renin and angiotensin (Ang) II levels were measured by ELISA. The serum levels of renin and Ang II were significantly increased in the vehicle group compared with the sham group, which was also observed for the myocardial expression of renin and Ang II receptor type 1 (AT1R), as determined by reverse transcription‑quantitative polymerase chain reaction and western blotting. EPO alone did not significantly reduce the high serum levels of renin and Ang II post-resuscitation, but changed the protein levels of renin and AT1R expression in myocardial tissues. However, EPO enhanced the myocardial expression of Ang II receptor type 2 (AT2R) following ROSC. In conclusion, the present study confirmed that CA resuscitation activated the renin‑Ang II‑AT1R signaling pathway, which may contribute to myocardial dysfunction in rats. The present study confirmed that EPO treatment is beneficial for protecting cardiac function post‑resuscitation, and the roles of EPO in alleviating post‑resuscitation myocardial dysfunction may potentially be associated with enhanced myocardial expression of AT2R.

Angiotensin II type 1 receptor antagonists in animal models of vascular, cardiac, metabolic and renal disease

We have reviewed the effects of angiotensin II type 1 receptor antagonists (ARBs) in various animal models of hypertension, atherosclerosis, cardiac function, hypertrophy and fibrosis, glucose and lipid metabolism, and renal function and morphology. Those of azilsartan and telmisartan have been included comprehensively whereas those of other ARBs have been included systematically but without intention of completeness. ARBs as a class lower blood pressure in established hypertension and prevent hypertension development in all applicable animal models except those with a markedly suppressed renin-angiotensin system; blood pressure lowering even persists for a considerable time after discontinuation of treatment. This translates into a reduced mortality, particularly in models exhibiting marked hypertension. The retrieved data on vascular, cardiac and renal function and morphology as well as on glucose and lipid metabolism are discussed to address three main questions: 1. Can ARB effects on blood vessels, heart, kidney and metabolic function be explained by blood pressure lowering alone or are they additionally directly related to blockade of the renin-angiotensin system? 2. Are they shared by other inhibitors of the renin-angiotensin system, e.g. angiotensin converting enzyme inhibitors? 3. Are some effects specific for one or more compounds within the ARB class? Taken together these data profile ARBs as a drug class with unique properties that have beneficial effects far beyond those on blood pressure reduction and, in some cases distinct from those of angiotensin converting enzyme inhibitors. The clinical relevance of angiotensin receptor-independent effects of some ARBs remains to be determined.

Arginine vasopressin during cardiopulmonary resuscitation: laboratory evidence, clinical experience and recommendations, and a view to the future

When stimulating adult pigs with ventricular fibrillation or postcountershock pulseless electrical activity for cardiopulmonary resuscitation, vasopressin improved vital organ blood flow, cerebral oxygen delivery, ability to be resuscitated, and neurologic recovery better than epinephrine. In pediatric preparations with asphyxia, epinephrine was superior to vasopressin, whereas in both pediatric pigs with ventricular fibrillation and adult porcine models with asphyxia, combinations of vasopressin and epinephrine proved to be highly effective. This may suggest that a different efficiency of vasopressors in pediatric vs. adult preparations and different effects of dysrhythmic vs. asphyxial cardiac arrest on vasopressor efficiency may be of significant importance. Whether these theories can be extrapolated to humans is unknown at this time. In patients who experienced out-of-hospital ventricular fibrillation, a larger proportion of patients treated with vasopressin survived 24 hrs compared with patients treated with epinephrine; during in-hospital cardiopulmonary resuscitation, comparable short-term survival was found in groups treated with either vasopressin or epinephrine. Currently, a large trial comprising patients who experience out-of-hospital cardiac arrest and who are treated with vasopressin vs. epinephrine is ongoing in Germany, Austria, and Switzerland. The new cardiopulmonary resuscitation guidelines of both the American Heart Association and the European Resuscitation Council consider 40 units of vasopressin intravenously and 1 mg of epinephrine intravenously equally effective for the treatment of adult patients with ventricular fibrillation; however, because of a lack of clinical data, no recommendation for vasopressin has been made for adult patients with asystole and pulseless electrical activity or for pediatric patients.

Pressor drugs in the treatment of cardiac arrest

The importance of vital organ perfusion in patients suffering cardiac arrest makes arterial vasomotor tone, and the resultant perfusion pressure, critical in resuscitation from sudden death. Although there are multiple mechanisms that may affect arterial vascular tone, historically, the therapy most commonly used has been catecholamine-induced adrenergic receptor stimulation, with catecholamine epinephrine being the commonest drug used. Over the last decade, however, it has become widely known that the utility of epinephrine during cardiopulmonary resuscitation is undefined. This has led to research into alternative agents, in particular nonadrenergic vasoactive peptides. Other agents appear promising. This article addresses pressor drugs and adrenergic agonists, including a review of their history, basic science, mechanism of action, and efficacy. Epinephrine is reviewed.

Telmisartan: a review of its use in hypertension

Telmisartan is an angiotensin II receptor antagonist that is highly selective for type 1 angiotensin II receptors. It was significantly more effective than placebo in large (n >100), double-blind, randomised, multicentre clinical trials in patients with mild to moderate hypertension. Telmisartan 20 to 160 mg once daily produced mean reductions in supine trough systolic blood pressure and diastolic blood pressure of up to 15.5 and 10.5 mm Hg, respectively. Maximum blood pressure reduction occurred with a dosage of 40 to 80 mg/day. Telmisartan 40 to 120 mg/day was as effective as amlodipine 5 to 10 mg/day or atenolol 50 to 100 mg/day in dose-titration studies. Telmisartan 20 to 160 mg/day was generally similar in efficacy to enalapril 5 to 20 mg/day or lisinopril 10 to 40 mg/day in both titration-to-response and other studies. Hydrochlorothiazide was coadministered in most of the titration-to-response studies if patients remained hypertensive. Telmisartan 80 mg/day was more effective than submaximal dosages of losartan (50 mg/day) or valsartan (80 mg/day) and was as effective as a fixed-dose combination of losartan 50 mg plus hydrochlorothiazide 12.5 mg over the last 6 hours of the dosage interval and the whole 24-hour postdose interval. In patients with severe hypertension, telmisartan 80 to 160 mg/day was as effective as enalapril 20 to 40 mg/day (both agents could be titrated and combined sequentially with hydrochlorothiazide 25 mg and amlodipine 5 mg). The addition of hydrochlorothiazide to telmisartan was more effective than each agent alone at lowering blood pressure in patients with hypertension. Telmisartan was well tolerated in patients with mild to moderate hypertension and was significantly less likely to cause persistent, dry cough than lisinopril.

CONCLUSION

Telmisartan is an effective antihypertensive agent with a tolerability profile similar to that of placebo. Comparative data have shown telmisartan to be as effective as other major classes of antihypertensive agents at lowering blood pressure. Compared with lisinopril, telmisartan is associated with a significantly lower incidence of dry, persistent cough. Therefore, telmisartan is a useful therapeutic option in the management of patients with hypertension.

Arginine vasopressin during cardiopulmonary resuscitation and vasodilatory shock: current experience and future perspectives

Epinephrine use during cardiopulmonary resuscitation (CPR) is controversial because of its receptor-mediated adverse effects such as increased myocardial oxygen consumption, ventricular arrhythmias, ventilation-perfusion defect, postresuscitation myocardial dysfunction, ventricular arrhythmias, and cardiac failure. In the CPR laboratory, vasopressin improved vital organ blood flow, cerebral oxygen delivery, resuscitability, and neurologic recovery more than did epinephrine. In patients with out-of-hospital ventricular fibrillation, a larger proportion of patients treated with vasopressin survived 24 hours than did patients treated with epinephrine. Currently, a large trial of out-of-hospital cardiac arrest patients being treated with vasopressin versus epinephrine is ongoing in Germany, Austria, and Switzerland. The new international CPR guidelines recommend 40 U vasopressin intravenously, and 1 mg epinephrine intravenously, as equally effective for the treatment of adult patients in ventricular fibrillation; however, no recommendation for vasopressin has been made to date for adult patients with asystole and pulseless electrical activity, or in children, because of lack of clinical data. When adrenergic vasopressors were unable to maintain arterial blood pressure in patients with vasodilatory shock, continuous infusions of vasopressin (0.04-0.10 U/min) stabilized cardiocirculatory parameters and even ensured weaning from catecholamines.

Effects of vasopressin and epinephrine on splanchnic blood flow and renal function during and after cardiopulmonary resuscitation in pigs

OBJECTIVE

To compare the effects of vasopressin versus epinephrine on splanchnic blood flow during and after cardiopulmonary resuscitation (CPR), and to evaluate the effects of these vasopressors on renal function in the postresuscitation phase.

DESIGN

Prospective, randomized laboratory investigation using an established porcine CPR model with instrumentation for continuous measurement of splanchnic and renal blood flow.

SETTING

University hospital experimental laboratory.

SUBJECTS

A total of 12 anesthetized, 12- to 16-wk-old domestic pigs weighing 30-35 kg.

INTERVENTIONS

After 4 mins of cardiac arrest, and 3 mins of CPR, 12 pigs were randomly assigned to receive either 0.4 units/kg vasopressin (n = 6) or 45 microg/kg epinephrine (n = 6). Defibrillation was performed 5 mins after drug administration; all animals were observed for 6 hrs after return of spontaneous circulation (ROSC).

MEASUREMENTS AND MAIN RESULTS

Mean +/- SEM superior mesenteric artery blood flow was significantly (p < .05) lower after vasopressin compared with epinephrine at 90 secs after drug administration (13+/-3 vs. 129+/-33 mL/min); at 5 mins after drug administration (31+/-18 vs. 155+/-39 mL/min); at 5 mins after ROSC (332+/-47 vs. 1087+/-166 mL/min); and at 15 mins after ROSC (450+/-106 vs. 1130+/-222 mL/min); respectively. Mean +/- SEM left renal and hepatic artery blood flow after ROSC was comparable in both groups ranging between 120-290 mL/min (renal blood flow), and 150-360 mL/min (hepatic blood flow), respectively. Median urine output after ROSC showed no difference between groups, and highest values (180-220 mL/hr) were observed in the first 60 mins after ROSC. Median calculated glomerular filtration rate showed no difference between groups with values ranging between 30 and 80 mL/min in the postresuscitation phase. Calculated fractional sodium excretion and osmolar relationship between urea and plasma indicated no evidence for renal tubular dysfunction.

CONCLUSIONS

In the early postresuscitation phase, superior mesenteric blood flow was temporarily impaired by vasopressin in comparison with epinephrine. With respect to renal blood flow and renal function after ROSC, there was no difference between either vasopressor given during CPR. Vasopressin given during CPR did not result in an antidiuretic state in the postresuscitation phase.

Efficacy and safety of telmisartan, a selective AT1 receptor antagonist, compared with enalapril in elderly patients with primary hypertension. TEES Study Group

OBJECTIVE

To assess the antihypertensive efficacy and safety of the novel AT1 receptor antagonist, telmisartan, compared with that of enalapril in elderly patients with mild to moderate hypertension.

DESIGN

A 26-week, multicenter, double-blind, parallel-group, dosage titration study.

METHODS

A total of 278 patients aged > or = 65 years were randomized to eithertelmisartan or enalapril once a day. The telmisartan dosage was increased from 20 to 40-80 mg and that of enalapril from 5 to 10-20 mg at 4-week intervals until trough supine diastolic blood pressure was < 90 mmHg. After 12 weeks, hydrochlorothiazide at 12.5-25 mg once a day was added to the treatment regimen of those patients not controlled on monotherapy.

RESULTS

Both treatments lowered blood pressure in a comparable and clinically meaningful manner. The adjusted mean changes from baseline in supine diastolic blood pressure at trough were -12.8 mmHg for telmisartan and -11.4 mmHg for enalapril (P = 0.074). Mean changes in supine systolic blood pressure were -22.1 mmHg for telmisartan and -20.1 mmHg for enalapril (P = 0.350). Overall, 63 and 62% of patients responded to telmisartan and enalapril, respectively, with a supine diastolic blood pressure of < 90 mmHg. Both regimens provided effective blood pressure lowering over the 24 h dosing interval, as determined by ambulatory blood pressure monitoring. Both regimens were well tolerated; however, patients on the enalapril regimen had more than double the incidence of treatment-related cough compared with those on the telmisartan regimen (16 versus 6.5%).

CONCLUSIONS

These results demonstrate that telmisartan is well tolerated and is at least as effective as enalapril in treating elderly patients with mild to moderate hypertension.