Nifedipine in hypertensive emergencies

Hypertensive Response to Ischemic Stroke in the Normotensive Wistar Rat

Background and Purpose—

Over 80% of ischemic stroke patients show an abrupt increase in arterial blood pressure in the hours and days following ischemic stroke. Whether this poststroke hypertension is beneficial or harmful remains controversial and the underlying physiological basis is unclear.

Methods—

To investigate the dynamic cardiovascular response to stroke, adult Wistar rats (n=5–8 per group, 393±34 g) were instrumented with telemeters to blood pressure, intracranial pressure, renal sympathetic nerve activity, and brain tissue oxygen in the predicted penumbra (P o 2 ). After 2 weeks of recovery, cardiovascular signals were recorded for a 3-day baseline period, then ischemic stroke was induced via transient middle cerebral artery occlusion, or sham surgery. Cardiovascular signals were then recorded for a further 10 days, and the functional sensorimotor recovery assessed using the cylinder and sticky dot tests.

Results—

Baseline values of all variables were similar between groups. Compared to sham, in the 2 days following stroke middle cerebral artery occlusion produced an immediate, transient rise above baseline in mean blood pressure (21±3 versus 2±4 mm Hg; P <0.001), renal sympathetic nerve activity (54±11% versus 7±4%; P =0.006), and cerebral perfusion pressure (12±5 versus 1±4; P ≤0.001). Intracranial pressure increased more slowly, peaking 3 days after middle cerebral artery occlusion (14±6 versus −1±1 mm Hg; P <0.001). Treating with the antihypertensive agent nifedipine after stroke (1.5–0.75 mg/kg per hour SC) ameliorated poststroke hypertension (12±3 mm Hg on day 1; P =0.041), abolished the intracranial pressure increase (3±1; P <0.001) and reduced cerebral perfusion pressure (10±3 mm Hg; P =0.017). Preventing poststroke hypertension affected neither the recovery of sensorimotor function nor infarct size.

Conclusions—

These findings suggest that poststroke hypertension is immediate, temporally matched to an increase in sympathetic outflow, and elevates cerebral perfusion pressure for several days after stroke, which may enhance cerebral perfusion. Preventing poststroke hypertension does not appear to worsen prognosis after stroke in young, normotensive, and otherwise healthy rats.

Visual Overview—

An online visual overview is available for this article.

Hypertensive Crises

Hypertensive crises are a group of medical conditions in which a rapid decrease in blood pressure is necessary to prevent serious complications. Although uncommon in clinical practice, a hypertensive crisis should be recog nized and treated promptly. Any form of hypertension may be associated with hypertensive crisis, the main determinant being the level of blood pressure rather than the cause of hypertension. In certain clinical situa tions the abruptness with which the blood pressure in creases seems to be more important than the absolute level of blood pressure in causing the hypertensive crisis (e.g., toxemia of pregnancy in women and acute onset of hypertension in children with acute glomerulo nephritis). In other clinical situations the absolute level of blood pressure does not affect the seriousness of hy pertension so much as coexisting complications that may make even moderate hypertension dangerous (e.g., acute aortic dissection and acute left ventricular fail ure ).

Blood pressure treatment and outcomes in hypertensive patients without acute target organ damage: a retrospective cohort

OBJECTIVES

The objective is of the study to evaluate the effect of antihypertensive therapy in emergency department (ED) patients with markedly elevated blood pressure (BP) but no signs/symptoms of acute target organ damage (TOD).

METHODS

This is a retrospective cohort study of ED patients age 18 years and older with an initial BP greater than or equal to 180/100 mm Hg and no acute TOD, who were discharged with a primary diagnosis of hypertension. Patients were divided based on receipt of antihypertensive therapy and outcomes (ED revisits and mortality) and were compared.

RESULTS

Of 1016 patients, 435 (42.8%) received antihypertensive therapy, primarily (88.5%) oral clonidine. Average age was 49.2 years, and 94.5% were African American. Treated patients more often had a history of hypertension (93.1% vs 84.3%; difference = -8.8; 95% confidence interval [CI], -12.5 to -4.9) and had higher mean initial systolic (202 vs 185 mm Hg; difference = 16.9; 95% CI, -19.7 to -14.1) and diastolic (115 vs 106 mm Hg; difference = -8.6; 95% CI, -10.3 to -6.9) BP. Emergency department revisits at 24 hours (4.4% vs 2.4%; difference = -2.0; 95% CI, -4.5 to 0.3) and 30 days (18.9% vs 15.2%; difference = -3.7; 95% CI, -8.5 to 0.9) and mortality at 30 days (0.2% vs 0.2%; difference = 0; 95% CI, -1.1 to 0.8) and 1 year (2.1% vs 1.6%; difference = -0.5; 95% CI, -2.5 to 1.2) were similar.

CONCLUSIONS

Revisits and mortality were similar for ED patients with markedly elevated BP but no acute TOD, whether they were treated with antihypertensive therapy, suggesting relative safety with either approach.

Treatment of hypertensive urgencies and emergencies

Although systemic hypertension is a common clinical condition, hypertensive emergencies are unusual in clinical practice. There are some situations, however, that qualify as hypertensive emergencies or urgencies. It is important, therefore, to diagnose these acute conditions, in which immediate treatment of hypertension is indicated. The diagnosis of hypertensive emergencies depends on consideration of the clinical manifestations as well as the absolute level of blood pressure. Manifestations of hypertensive emergencies can be quite profound, but they vary depending on the target organ that is affected. Thus, an accurate clinical diagnosis is necessary to render appropriate therapy. Fortunately, effective drug therapy is available to lower the blood pressure quickly in hypertensive emergencies. Physicians should be familiar with the pharmacologic and clinical actions of drugs in treating hypertensive emergencies. With proper clinical diagnosis, hypertensive emergencies can be successfully treated, and complications can be largely prevented with timely intervention.

Reversibility of cerebral symptoms in severe hypertension in relation to acute antihypertensive therapy. Danish Multicenter Study

Cerebral symptoms were registered in a multicenter study including 64 patients with severe hypertension, diastolic blood pressure (DBP) greater than or equal to 135 mmHg, and more or less pronounced hypertensive encephalopathy. The symptoms were: headache (70%), dizziness (35%), consciousness disturbances (28%), nausea (27%), paresis (23%), blurred vision (22%), paraesthesia (21%) and vomiting (14%). None had convulsions or coma. Initial treatment was furosemide i.v., and if DBP was greater than or equal to 125 mmHg after one hour, patients were randomized to treatment with either i.v. diazoxide (bolus injections of 75-150 mg) or i.m. dihydralazine (bolus injections of 6-12.5 mg). A gradual fall in blood pressure (BP) was obtained in all three groups. Along with BP reduction a substantial regression of neurological symptoms was registered. After 5 hours only minor cerebral symptoms were present without significant difference between diazoxide and dihydralazine. None developed cerebral complications. The study failed to show a significant correlation between BP reduction and regression of neurological symptoms graded semiquantitatively. Reduction of BP by titration using small repeated bolus injections is recommended, but oral treatment should be considered in the patients who are able to ingest peroral medication in spite of neurological symptoms.

Antihypertensive, haemodynamic and metabolic effects of nifedipine slow-release tablets in elderly patients

In a double-blind, cross-over study for 8 weeks, including 10 non-hospitalized elderly hypertensives (average age 73.2 years), WHO stage I-II, the antihypertensive effect of nifedipine slow-release tablets, 20 mg twice daily, was compared with placebo. Nifedipine reduced supine and standing blood pressure values significantly, and no signs of orthostatic hypotension were noted. An initial increment in heart rate was found after 1 week with a subsequent fall towards control values after 8 weeks of nifedipine administration. Heart rate pressure product in the supine position was reduced, and this reduction became statistically significant at the 8th week. Cardiac output measured non-invasively in 8 patients after 6-8 weeks' nifedipine therapy, using an Irex echocardiograph, was on an average 34% higher than in the placebo period (p less than 0.05). Serum electrolytes, cholesterol, HDL cholesterol, blood glucose and renal function were not affected by the drug. Side-effects were few and mild. It is concluded that nifedipine is a potent antihypertensive agent which may represent an attractive first choice alternative in the treatment of elderly hypertensive patients.

Hemodynamic effects of calcium channel blockers in essential hypertension

Calcium channel blockers decrease blood pressure in essential hypertension due to a marked reduction of systemic vascular resistance (arteriolar tone). They also dilate conducting arteries but have no venodilatory effect in antihypertensive doses. With the dihydropyridines (e.g. nifedipine) and diltiazem there is a transient increase in heart rate and cardiac output but this is not observed with verapamil. The vasodilatory responsiveness in the resistance vessels to calcium channel blockers is selectively enhanced in patients with established essential hypertension but not in the early borderline phase of hypertension. During treatment with chlorthalidone, atenolol, acebutolol or nitrendipine for four to six weeks the reduction of blood pressure is accompanied by a selective decrease in the vasodilatory responsiveness to calcium channel blockers.

Pharmacological interventions for hypertensive emergencies

BACKGROUND

Hypertensive emergencies, marked hypertension associated with acute end-organ damage, are life-threatening conditions. Many anti-hypertensive drugs have been used in these clinical settings. The benefits and harms of such treatment and the best first-line treatment are not known.

OBJECTIVES

To answer the following two questions using randomized controlled trials (RCTs): 1) does anti-hypertensive drug therapy as compared to placebo or no treatment affect mortality and morbidity in patients presenting with a hypertensive emergency? 2) Does one first-line antihypertensive drug class as compared to another antihypertensive drug class affect mortality and morbidity in these patients?

SEARCH STRATEGY

Electronic sources: MEDLINE, EMBASE, Cochrane clinical trial register. In addition, we searched for references in review articles and trials. We attempted to contact trialists. Most recent search August 2007.

SELECTION CRITERIA

All unconfounded, truly randomized trials that compare an antihypertensive drug versus placebo, no treatment, or another antihypertensive drug from a different class in patients presenting with a hypertensive emergency.

DATA COLLECTION AND ANALYSIS

Quality of concealment allocation was scored. Data on randomized patients, total serious adverse events, all-cause mortality, non-fatal cardiovascular events, withdrawals due to adverse events, length of follow-up, blood pressure and heart rate were extracted independently and cross checked.

MAIN RESULTS

Fifteen randomized controlled trials (representing 869 patients) met the inclusion criteria. Two trials included a placebo arm. All studies (except one) were open-label trials. Seven drug classes were evaluated in those trials: nitrates (9 trials), ACE-inhibitors (7), diuretics (3), calcium channel blockers (6), alpha-1 adrenergic antagonists (4), direct vasodilators (2) and dopamine agonists (1). Mortality event data were reported in 7 trials. No meta-analysis was performed for clinical outcomes, due to insufficient data. The pooled effect of 3 different anti-hypertensive drugs in one placebo-controlled trial showed a statistically significant greater reduction in both systolic [WMD -13, 95%CI -19,-7] and diastolic [WMD -8, 95%CI, -12,-3] blood pressure with antihypertensive therapy.

AUTHORS' CONCLUSIONS

There is no RCT evidence demonstrating that anti-hypertensive drugs reduce mortality or morbidity in patients with hypertensive emergencies. Furthermore, there is insufficient RCT evidence to determine which drug or drug class is most effective in reducing mortality and morbidity. There were some minor differences in the degree of blood pressure lowering when one class of antihypertensive drug is compared to another. However, the clinical significance is unknown. RCTs are needed to assess different drug classes to determine initial and longer term mortality and morbidity outcomes.

Hypertensive emergencies. Etiology and management

Although systemic hypertension is a common clinical disorder, hypertensive emergencies are unusual in clinical practice. Situations that qualify as hypertensive emergencies include accelerated or malignant hypertension, hypertensive encephalopathy, acute left ventricular failure, acute aortic dissection, pheochromocytoma crisis, interaction between tyramine-containing foods or drugs and monoamine oxidase inhibitors, eclampsia, drug-induced hypertension and possibly intracranial hemorrhage. It is important to recognize these conditions since immediate lowering of systemic blood pressure is indicated. The diagnosis of hypertensive emergencies depends on the clinical manifestations rather than on the absolute level of the blood pressure. Depending on the target organ that is affected, the manifestations of hypertensive emergencies can be quite expressive, yet variable. Thus, the physician has to make the clinical diagnosis urgently in order to render appropriate therapy. Several parenteral drugs can quickly and effectively lower the blood pressure in hypertensive emergencies. Intravenous fenoldopam, a selective dopamine (DA1) receptor agonist, offers the advantage of improving renal blood flow and causing natriuresis. Intravenous nicardipine may be beneficial in reserving tissue perfusion in patients with ischemic disorders. Whereas trimethaphan camsilate is the drug of choice for managing acute aortic dissection, hydralazine remains the drug of choice for the treatment of eclampsia. The alpha-adrenoceptor, phentolamine, is useful in patients with pheochromocytoma crisis. Enalaprilat is the only ACE inhibitor available for parenteral use and may be particularly useful in treating hypertensive emergencies in patients with heart failure. However, ACE inhibitors may cause a precipitous fall in blood pressure in patients who are hypovolemic. Although useful as adjunctive therapy in hypertensive crises, diuretics should be used with caution in these patients because prior volume depletion may be present in some conditions such as malignant hypertension. The treating physician should be familiar with the pharmacological and clinical actions of drugs which are indicated for and useful in the treatment of hypertensive emergencies. Once the patient's situation has stabilized, the patient may be switched to an oral medication and the physician should discuss long term follow up plans. With appropriate clinical diagnosis, hypertensive emergencies can be successfully treated and the complications can be prevented with timely intervention.

Drug Treatment of Hypertensive Urgencies and Emergencies

Although systemic hypertension is a common clinical condition, hypertensive emergencies are distinctly unusual in clinical practice. There are some situations, however, that qualify as hypertensive emergencies or urgencies. It is important, therefore, to diagnose these conditions because immediate treatment of severe hypertension is indicated. The diagnosis of hypertensive emergencies depends on the consideration of the clinical manifestations as well as the absolute level of blood pressure. Depending on the target organ that is affected, manifestations of hypertensive emergencies can be quite profound, yet variable. Thus, the physician has to make an accurate clinical diagnosis properly to render appropriate therapy. Fortunately, effective drug therapy is available to decrease blood pressure quickly in hypertensive emergencies. Physicians should be familiar with the pharmacologic and clinical actions of drugs that are used in the treatment of hypertensive emergencies. With proper clinical diagnosis, hypertensive emergencies can be treated successfully and the complications can be prevented with timely intervention. This review discusses the treatment of hypertensive emergencies in general and the therapeutic role of fenoldopam in particular.

Influence of treatment with Ca(2+) antagonists on cerebral vasculature of spontaneously hypertensive rats

Hypertension is the main cause of stroke that represents the second most common cause of death in the industrialized world and a leading cause of inability of the elderly. Lowering blood pressure reduces cerebrovascular morbidity and mortality, but it is still controversial if blood pressure should be lowered in elderly individuals with concomitant cerebrovascular disease. The present study has analyzed comparatively the effect of treatment with the dihydropyridine-type Ca(2+) channel blockers lercanidipine, manidipine and nimodipine and with the non dihydropyridine-type vasodilator hydralazine on hypertension-dependent cerebrovascular changes in spontaneously hypertensive rats (SHR). Analysis included medium and small sized pial arteries and intracerebral arteries of frontal cortex, hippocampus, striatum, and cerebellum. In control SHR, systolic pressure (SBP) values were significantly higher in comparison with WKY rats. Pharmacological treatment significantly decreased SBP values, with nimodipine reducing only moderately SBP. In control SHR, thickening of arterial wall accompanied by luminal narrowing with consequent increase of the wall-to-lumen ratio occurred both in pial and intracerebral arteries. Dihydropyridine-type Ca(2+) antagonists and to a lesser extent hydralazine countered these morphological alterations. Lercanidipine displayed a particular activity on small sized intraparenchymal brain arteries, where it was more effective than other compounds tested. This activity of lercanidipine on small-sized intracerebral arteries might represent an interesting property for the treatment of hypertensive brain damage with concomitant ischemia.

The effect of oral clonidine premedication on lumbar cerebrospinal fluid pressure in humans

Alpha-2 adrenergic agonists including clonidine decrease cerebral blood flow. The specific actions of clonidine on cerebrospinal fluid (CSF) pressure in humans remain to be elucidated. We evaluated the effect of oral clonidine premedication on lumbar CSF pressure in patients without intracranial disease. Seventy-four patients undergoing subarachnoidal block were divided randomly into either a clonidine or a control group. In the clonidine group, the patients were premedicated orally with 5 microg/kg clonidine 60 min before arrival in the operating room. Subarachnoidal puncture was performed via midline approach using a 23-gauge needle at the L2-3 or L3-4 intervertebral space with the patient in the lateral decubitus position. Before the injection of local anesthetic, lumbar CSF pressure was measured. Lumbar CSF pressure was 8.1+/-2.4 mmHg in the clonidine group, which was significantly lower than that in the control group (9.4+/-2.8 mmHg, p<0.05). The cerebral perfusion pressures were 76.2+/-12.5 mmHg in the clonidine group and 91.7+/- 15.4 mmHg in the control group (p<0.001). In the clonidine group, preanesthetic mean blood pressure had a significant correlation with lumbar CSF pressure (r=0.619, p=0.019). We conclude that Lumbar CSF pressure was attenuated by oral premedication with 5 microg/kg clonidine. Clonidine also contributed to a significant correlation between preanesthetic mean blood pressure and CSF pressure.

Diagnosis and management of hypertensive emergencies

It has been estimated that approximately 600,000 to 800,000 Americans will develop a hypertensive crisis (Calhoun and Oparil, 1990). Although such numbers represent only about 1% of the estimated 60 million Americans with hypertension, hypertensive crisis often constitutes a major medical emergency, necessitating a focused, assertive, and reasoned therapeutic intervention. When such patients are seen in the emergency department or in a physician's office with a critical elevation in blood pressure (BP), appropriate and efficacious management is essential to avoid catastrophic injury to vital target organs, including the central nervous system, the heart, and the kidneys. Delays in initiating effective therapy or, equally important, overzealous therapy leading to a too-rapid reduction in BP can produce severe complications involving these target organs. This article reviews the spectrum of clinical syndromes that comprise hypertensive emergencies, highlighting 2 to illustrate the complexities of clinical presentation and management. The newly advocated treatment guidelines based on the category of acute severe hypertension (including asymptomatic hypertensive urgencies) are also considered, as are therapeutic strategies utilizing currently available antihypertensive agents.

Diagnosis and treatment of ischemic stroke

Most patients who have a stroke are evaluated initially by a primary care physician. For patients to benefit from new stroke therapies that must be initiated within a few hours of stroke onset, primary care physicians must be prepared to diagnose stroke and initiate acute treatment. This article provides information on the rapid and accurate diagnosis and management of patients with acute ischemic stroke. This information is particularly relevant due to the relatively high risk:benefit ratio associated with some acute stroke therapies, such as tissue plasminogen activator. Information is also provided about medical and surgical therapies to prevent subsequent strokes.

Management of hypertension in acute intracerebral hemorrhage

Hypertension commonly occurs in the acute period following spontaneous intracerebral hemorrhage. Management of this hypertension is controversial. Some advocate lowering blood pressure to reduce the risk of bleeding, edema formation, and systemic hypertensive complications, whereas others advocate allowing blood pressure to run its natural course as a protective measure against cerebral ischemia. This article reviews the pertinent clinical and experimental data regarding these issues and briefly discusses the use of antihypertensive agents commonly administered in this setting.

Amlodipine, a Ca2+ channel antagonist, modifies cerebral blood flow autoregulation in hypertensive rats

We measured the cerebral blood flow at rest and during hemorrhagic hypotension in 7 rats of each group using laser-Doppler flowmetry. Simultaneously, the absolute baseline cerebral blood flow values in the parietal cortex were quantified with the hydrogen clearance method. Baseline mean arterial pressure was significantly lowered, by 29 mm Hg, in the amlodipine-treated group, while the baseline cerebral blood flow was 36 +/- 4 ml/100 g/min (mean +/- S.D.) which was almost the same as the 40 +/- 5 in the control group. The lower limits of the cerebral blood flow autoregulation, defined as the mean arterial pressure at which the cerebral blood flow decreased by 10% of the baseline value, were shifted to a lower level of 107 +/- 9 mm Hg in the treated group compared with 133 +/- 5 mm Hg in the control (P < 0.001). The results demonstrated that, in hypertensive rats with amlodipine treatment, cerebral perfusion was preserved at a lower blood pressure level, which is advantageous under hypotensive conditions.

Treatment modalities for hypertensive patients with intracranial pathology: options and risks

OBJECTIVES

To review the cerebrovascular pathophysiology of hypertension, and the risks and benefits of antihypertensive therapies in the patient with intracranial ischemic or space-occupying pathology.

DATA SOURCES

Review of English language scientific and clinical literature, using MEDLINE search.

STUDY SELECTION

Pertinent literature is referenced, including clinical and laboratory investigations, to demonstrate principles of pathophysiology and controversies regarding the treatment of hypertension in patients with intracranial ischemic or space-occupying pathology.

DATA EXTRACTION

The literature was reviewed to summarize the pathophysiology, risks, and benefits of antihypertensive therapies in the patient with intracranial ischemic or space-occupying pathology. Treatment strategies were outlined with a particular emphasis on how antihypertensive agents may affect the brain.

DATA SYNTHESIS

Cerebral autoregulation typically occurs over a range of cerebral perfusion pressures between 50 and 150 mm Hg. Chronic hypertension results in adaptive changes that allow cerebral autoregulation to occur over a high range of pressures. Acute hypertension (rapid increase in perfusion pressure above the autoregulatory limit) may result in cerebral edema, persistent vasodilation, and brain injury. Treatment of a hypertensive emergency must be undertaken conservatively since the chronically hypertensive patient is at risk for ischemic brain injury when perfusion pressure is rapidly decreased beyond autoregulatory limits. In the patient with head injury or primary neurologic injury, acute antihypertensive intervention can result in further brain injury. Selection of appropriate antihypertensive therapy necessitates the careful consideration of agent-specific effects on cerebral blood flow, autoregulation, and intracranial pressure. For example, some vasodilators treat hypertension but also dilate the cerebral vasculature, and increase cerebral blood volume and intracranial pressure while decreasing cerebral perfusion pressure. Pharmacologic blockade of alpha 1- or beta 1-adrenergic receptors can reduce arterial blood pressure with little or no effect on intracranial pressure within the autoregulatory range. Like the direct peripheral vasodilators, calcium-channel antagonists are limited by cerebral vasodilation and increased intracranial pressure. Angiotensin converting enzyme inhibitors can also be used for mild to moderate hypertension but have the potential to further increase intracranial pressure in patients with intracranial hypertension. Barbiturates offer an alternative antihypertensive therapy since they decrease blood pressure as well as cerebral blood flow and oxygen metabolism.

CONCLUSIONS

The treatment of acute hypertension in the patient with intracranial ischemic or space-occupying pathology requires an understanding of the pathophysiology of hypertension and determinants of cerebral perfusion pressure. Individual agents should be selected based on their ability to promptly and reliably decrease blood pressure, while considering effects on cerebral blood flow and intracranial pressure.

Pharmacological management of hypertension in paediatric patients. A comprehensive review of the efficacy, safety and dosage guidelines of the available agents

The prevalence of hypertension in children, although lower than in adults, is still significant. An underlying cause is often identified in the younger patient, with essential hypertension accounting for the majority of cases in adolescents. The natural history of hypertension in childhood is still not well delineated. Previous Task Force recommendations are addressed to reflect current experience with the newer classes of agents, namely the angiotensin converting enzyme (ACE) inhibitors and the calcium channel blockers (CCBs) where either limited or no experience was previously available. In addition, the current treatment recommendations of Joint National Committee V (JNCV) are reflected in our discussion. The current drug classes are reviewed with respect to dosage guidelines, adverse effects and potential drug-drug interactions. The advantages and disadvantages of a tailored or individualised therapeutic approach as opposed to rigid stepped care therapy will be presented. Clearly, more long term data need to be obtained with respect to the safety and efficacy of the newer classes of drugs.

A new preparation of nifedipine for sublingual application in hypertensive urgencies

A new preparation of nifedipine for sublingual application in hypertensive urgencies was investigated in a prospective study. Patients admitted to the Emergency Department with a persistent elevation of systolic blood pressure (SBP) greater than 190 mmHg and/or a diastolic blood pressure (DBP) greater than 100 mmHg received nifedipine 10 mg sublingual with a sprayer. A second dose was administrated fifteen minutes later if an adequate response defined as a stable reduction of SBP below 180 mmHg and DBP below 100 mmHg had not occurred. Of 30 patients, 21 (70%) responded to the first nifedipine application, 7 responded to the second dose, and 2 nonresponders had to be treated with urapidil. Overall mean SBP was 206 +/- 19 mmHg and mean DBP was 113 +/- 15 mmHg before treatment, and a significant antihypertensive effect was noted within fifteen minutes after nifedipine spray (p < 0.05). The maximum antihypertensive effect was for SBP in sixty minutes (146 +/- 19 mmHg) and for DBP after one hundred twenty minutes (78 +/- 18 mmHg). The average reduction in SBP was 29% and in DBP 31%. In first-dose responders (n = 21) a significant antihypertensive effect was noted within fifteen minutes. SBP declined from 205 +/- 21 to a minimum of 142 +/- 15 mmHg (22.3%) after sixty minutes and DBP from 113 +/- 13 to a minimum of 77 +/- 11 mmHg (22.2%) after one hundred twenty minutes. In second-dose responders (n = 7) a significant antihypertensive effect was noted within thirty minutes.(ABSTRACT TRUNCATED AT 250 WORDS)

Treatment of hypertensive emergency. Comparison of a new dosage form of the calcium antagonist nitrendipine with nifedipine capsules

OBJECTIVE

To present the efficacy and tolerability of a new oral dosage form of the calcium antagonist nitrendipine compared to nifedipine capsules in patients with hypertensive emergency.

DESIGN

Multicenter randomized double blind clinical study.

SETTING

23 study centres (hospitals) in Germany.

PATIENTS

161 patients between 20 and 70 years with acutely elevated blood pressure (systolic 200-250 mmHg, diastolic between 110-140 mmHg) with and without concomitant clinical symptoms.

INTERVENTIONS

Double blind treatment with 10 mg nifedipine or 5 mg nitrendipine. Nifedipine was administered as capsules, nitrendipine was given from a small plastic tube (vial), containing 1 ml alcoholic solution. Every patient received in addition to the test medication a placebo corresponding to the other product. Patients with insufficient treatment after 45 min were given either an additional capsule of 10 mg nifedipine or a further vial containing 5 mg nitrendipine according to their group and maintaining the double dummy procedure.

MEASUREMENTS AND RESULTS

Blood pressure and heart rate were measured repeatedly during 4 h, before and 90 min after beginning of the treatment a 12 channel resting ECG was recorded. At 45 min after administration the blood pressure had fallen significantly from 216.0/117.4 mmHg to 170.0/93.3 mmHg under nifedipine and from 216.9/117.3 mmHg to 177.4/94.4 mmHg under nitrendipine. 61.6% of the nifedipine patients and 58.8% of the nitrendipine patients had already reached blood pressure values < 180/100 mmHg after 45 min and in both groups 83% of these patients were still in this limit at the end of the observation period after 4 h. Tolerability was very good in both groups.

CONCLUSION

The new dosage form of nitrendipine (vial with 1 ml of alcoholic solution) represents an alternative in the treatment of hypertensive emergency.

Oral labetalol versus oral nifedipine in hypertensive urgencies in the ED

Therapy in hypertensive urgencies is debated and complicated by the side effects of available agents. In a prospective, randomized, open labeled study, the use of oral labetalol, an alpha- and beta-adrenergic blocker, with oral nifedipine in hypertensive urgencies in the emergency department was compared. Patients with diastolic blood pressures (DBP) of more than 120 mm Hg without criteria for a hypertensive emergency were eligible. The drugs were given in a loading manner with doses and timing based on their respective pharmacokinetics until a DBP of 110 mm Hg or lower was obtained or 4 hours had passed. Either an initial labetalol dose of 200 mg and a repeat dose of 100 to 200 mg at 2 hours, depending on the DBP or nifedipine, 10-mg bite and swallow every hour up to a total dose of 20 mg were given. Ten patients were enrolled into each study group. A 100% response rate was defined as a DBP of 110 mm Hg or less was observed for nifedipine and an 80% response rate for labetalol (P > .2) was observed. The mean time to control was 67.5 minutes for labetalol and 60.0 minutes for nifedipine (P > .2). The pretreatment pressure for labetalol was 195/127 mm Hg and for nifedipine was 198/128 mm Hg (P > .2), which decreased to a posttreatment pressure for labetalol of 154/100 mm Hg and for nifedipine of 163/100 mm Hg (P > .2). The mean decrease in systolic (SBP)/DBP was 42.6/26.5 mm Hg with labetalol and 34.9/28.4 mm Hg for nifedipine (P > .2). No significant side effects occurred with either drug.(ABSTRACT TRUNCATED AT 250 WORDS)

Vasodilators during cerebral aneurysm surgery

The objective of this review is to review the anaesthetic implications of vasoactive compounds particularly with regard to the cerebral circulation and their clinical importance for the practicing anaesthetist. Material was selected on the basis of validity and application to clinical practice and animal studies were selected only if human studies were lacking. Hypotensive drugs have been used to induce hypotension and in the treatment of intraoperative hypertension during cerebral aneurysm surgery. After subarachnoid haemorrhage, cerebral blood flow is reduced and cerebral vasoreactivity is disturbed which may lead to brain ischaemia. Also, cerebral arterial vasospasm decreases cerebral blood flow, and may lead to delayed ischaemic brain damage which is a major problem after subarachnoid haemorrhage. Recently, the use of induced hypotension has decreased although it is still useful in patients with intraoperative aneurysm rupture, giant cerebral aneurysm, fragile aneurysms and multiple cerebral aneurysms. In this review, a variety of vasodilating agents, prostaglandin E1, sodium nitroprusside, nitroglycerin, trimetaphan, adenosine, calcium antagonists, and inhalational anaesthetics, are discussed for their clinical usefulness. Sodium nitroprusside, nitroglycerin and isoflurane are the drugs of choice for induced hypotension. Prostaglandin E1, nicardipine and nitroglycerin have the advantage that they do not alter carbon dioxide reactivity. Local cerebral blood flow is increased with nitroglycerin, decreased with trimetaphan and unchanged with prostaglandin E1. Intraoperative hypertension is a dangerous complication occurring during cerebral aneurysm surgery, but its treatment in association with subarachnoid haemorrhage is complicated in cases of cerebral arterial vasospasm because fluctuations in cerebral blood flow may be exacerbated. Hypertension should be treated immediately to reduce the risk of rebleeding and intraoperative aneurysmal rupture and the choice of drugs is discussed. Although the use of induced hypotension has declined, the control of arterial blood pressure with vasoactive drugs to reduce the risk of intraoperative cerebral aneurysm rupture is a useful technique. Intraoperative hypertension should be treated immediately but the cerebral vascular effects of each vasodilator should be understood before their use as hypotensive agents.

Drug therapy of renovascular hypertension

The renin-angiotensin system is responsible for renovascular hypertension resulting from narrowing of the renal arteries. Inhibitors of angiotensin-converting enzyme (ACE) interrupt the conversion of angiotensin I to angiotensin II, causing a reduction in blood pressure. Several drugs of this family have been introduced since captopril was launched, including enalapril, lisinopril, ramipril and others. While they are effective antihypertensive agents, they can in some cases lead to deterioration of renal function, especially in patients with bilateral renal artery stenosis or stenosis of a solitary kidney. ACE inhibitors must also be administered with caution to sodium-depleted patients. Calcium antagonists, presumed to be ideal for the treatment of low renin hypertension, have also proved to be effective in patients with renal artery stenosis, many of whom have severe refractory hypertension. These agents, in common with ACE inhibitors, may be useful for determining the lateralisation index used to establish the kidney responsible for hypertension.

Effect of hypercapnia or xylazine on lateral ventricle and lumbosacral cerebrospinal fluid pressures in pentobarbital-anesthetized horses

Facial artery pressure, central venous pressure, heart rate, and lateral ventricle cerebrospinal fluid (CSF) pressure (LV-CSFP) were measured in 10 pentobarbital-anesthetized horses at arterial partial pressure of carbon dioxide (PaCO2) values of 40, 60, and 80 mm Hg, produced by varying the inspired carbon dioxide concentration. Variables were recorded at 5-minute intervals for 15 minutes at each level of PaCO2. Arterial blood gas analysis was performed at the end of the 15-minute time period for each level of PaCO2. Lateral ventricle CSF pressure was significantly increased (p < .05) at a PaCO2 of 80 mm Hg. Cardiovascular variables were not significantly changed by changing PaCO2. The PaCO2 was returned to 40 mm Hg; 1.1 mg xylazine/kg body weight was injected intravenously in eight horses, and data were collected for 60 minutes. No significant changes were observed. No changes were observed in two control horses not receiving xylazine. Subsequently, placement of a lumbosacral subarachnoid catheter allowed simultaneous measurement of LV-CSFP and lumbosacral CSF pressure (LS-CSFP) at PaCO2 values of 40, 60, and 80 mm Hg. The Pearson Correlation Coefficient between LV-CSFP and LS-CSFP was 0.94 (p < .0001) It was concluded that changes in CSF pressure could be detected at the lateral ventricle and the lumbosacral space; increasing PaCO2 to 80 mm Hg resulted in significant increases in LV-CSFP; xylazine does not increase LV-CSFP in pentobarbital-anesthetized, normocapnic horses; and under the conditions of this experiment, LV-CSFP and LS-CSFP were closely correlated.

Management of hypertensive emergencies

Between 1975 and 1985, 454 patients with hypertension were admitted to the Renal Unit of the Hospital for Sick Children. A total of 110 (24%) patients presented with severely raised blood pressures deemed to require emergency management. At presentation 84/110 had symptoms and signs of long standing hypertension with neurological involvement. Between 1975 and 1980 bolus intravenous injections of diazoxide and/or hydralazine were used with the aim of reducing the blood pressure to within the normal range for age in the first 12-24 hours after admission. Of 57 patients treated in this way 13 developed hypotensive complications and four, whose blood pressures returned to normal within 24 hours of admission, suffered irreversible neurological damage. Subsequently, the management changed to the use of intravenous infusions of labetalol (1-3 mg/kg/hour) and/or sodium nitroprusside (0.5-8 micrograms/kg/min) to enable a more gradual controlled reduction of blood pressure over the first 96 hours of admission. Between 1980 and 1985, 53 patients were treated using this regimen. In all cases blood pressure reduction was achieved in a more controlled manner without further neurological impairment or serious irreversible side effects. From our experience, the use of labetalol and sodium nitroprusside by incremental infusion in the critical early phase of management has resulted in improved control of accelerated hypertension without the sudden hypotensive episodes seen when bolus injections are used.

A comparison of the acute hypotensive effects of two different doses of nifedipine

To determine whether a dose of 5 mg of nifedipine would be useful in the treatment of hypertensive emergencies, we compared the acute hypotensive effects of two different doses of nifedipine, 5 mg and 10 mg, in patients with severe hypertension. In this prospective, randomized, double-blind study, 30 consecutive black patients with diastolic blood pressure that was equal to or greater than 115 mm Hg received either a 5 mg or 10 mg nifedipine capsule and a placebo capsule, which matched that of the alternative strength. Patients were asked to bite the capsules and swallow the contents. Blood pressure response over 4 hours and adverse effects were monitored. Mean systolic blood pressure was reduced from 191.7 mm Hg (95% confidence interval 170.8 to 212.7 mm Hg) to 157.9 mm Hg (137.0 to 178.9 mm Hg) and 206.1 mm Hg (185.1 to 227.0 mm Hg) to 153.7 mm Hg (132.8 to 174.7 mm Hg) in patients who were given 5 mg and 10 mg doses of nifedipine, respectively. Mean diastolic blood pressure in the group of patients that received 5 mg doses of nifedipine decreased from 128.2 mm Hg (115.6 to 140.7 mm Hg) to 105.2 mm Hg (92.7 to 117.7 mm Hg); the corresponding values in the group that received 10 mg doses of nifedipine were 129.9 mm Hg (117.4 to 142.5 mm Hg) and 97.5 mm Hg (85.0 to 110.1 mm Hg), respectively. The minimum mean systolic blood pressures occurred 20 and 25 minutes after administration of the 5 mg and 10 mg capsules, respectively; the minimum diastolic blood pressures were reached after 20 and 30 minutes, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Is sublingual nifedipine administration superior to oral administration in the active treatment of hypertension?

Nifedipine, a calcium-channel-blocking agent, was administered orally to 44 untreated patients (Group A) and sublingually to 51 untreated patients (Group B) who had a diastolic blood pressure more than 90 mm Hg and systolic blood pressure more than 140 mm Hg. The mean pretreatment systolic and diastolic blood pressure values were 185.3 +/- 26.0 and 115.1 +/- 13.4 mm Hg in Group A patients and 193.6 +/- 23.1 and 118.1 +/- 14.1 mm Hg in Group B patients respectively (p greater than 0.05). The hypotensive activity of nifedipine was observed at the tenth minute in both groups. Mean systolic and diastolic pressures were 168.9 +/- 23.7 and 101.9 +/- 14.2 mm Hg in Group A and 170.6 +/- 26.2 and 103.0 +/- 15.8 mm Hg in Group B, (p less than 0.001) Diastolic blood pressures dropped under 100 mm Hg at the twentieth minute in both groups. Maximal reduction of blood pressure was observed at the fortieth minute in both groups and the degree of reduction in blood pressure was also the same (mean systolic and diastolic blood pressures: 143.7 +/- 22.1 and 86.9 +/- 11.7 in Group A and 148.7 +/- 21.4 and 91.7 +/- 17.0 in Group B (p less than 0.05). The authors conclude that sublingual nifedipine administration is not superior to oral nifedipine administration (in capsular form) in the acute treatment of hypertension.

Reversal of endothelin-1-induced vasoconstriction by nifedipine in human resistance vessels in vivo in healthy subjects

The influence of blockade of voltage-operated calcium channels by nifedipine on endothelin-1-induced vasoconstriction was investigated in 10 healthy volunteers. Brachial artery infusions of nifedipine (0.25, 0.5, 1 and 3 micrograms/min/100 ml forearm tissue) resulted in dose-dependent increases (mean +/- SD) in forearm blood flow (103 +/- 63% to 833 +/- 426%). Intraarterial infusions of endothelin-1 (50 ng/min/100 ml) resulted in transient increases in forearm blood flow (2.6 +/- 0.9 vs 3.9 +/- 2.0 ml/min/100 ml, p less than 0.01) in the first minute of infusion and subsequent decreases (to 1.0 +/- .5 ml/min/100 ml, p less than 0.01) in the third minute of infusion. Endothelin-1-induced vasoconstriction was reversed by the lowest dose of nifedipine, whereas the higher dosages of nifedipine further increased forearm blood flow to 12.5 +/- 6.4 ml/min/100 ml. The percent increase of forearm blood flow during co-infusion of endothelin-1 and the highest dosage of nifedipine was significantly greater compared with nifedipine alone (1,204 +/- 531% vs 833 +/- 426%, p less than 0.05). The results demonstrate a dual action of luminally applied endothelin-1 in human resistance vessels in vivo (e.g., transient initial vasodilation followed by pronounced vasoconstriction) and suggest that blockade of voltage-operated calcium channels can effectively counteract the vasoconstrictor effects of endothelin-1.

Oral nifedipine in the treatment of hypertensive crises in patients with hypertensive encephalopathy

Hypertensive emergencies, including hypertensive encephalopathy represents an acute threat to vital organ functions and call for urgent treatment. The intravenous medications currently available for the management of hypertensive emergencies, have significant potential for serious side effects and acute lowering of blood pressure has often been the cause of considerable morbidity and mortality. Nifedipine is known to be effective as an antihypertensive agent and it is widely used in hypertensive emergencies. We studied the efficacy and effective dose of nifedipine in 22 patients (9 females and 13 males; mean age 51) with hypertensive encephalopathy. Nifedipine (20 mg by oral drop) caused a significant fall in diastolic an systolic blood pressure in all patients from 236/121 to 172/96 mmHg after 30 minutes (P less than 0.005, P less than 0.001). Continuous therapy with nifedipine (2-5 mg every 2-3 hours, mean total dose 52 mg/24 h) gave successful control of blood pressure. These data prove that nifedipine can be used as the first-line drug for the treatment of hypertensive crises in patients with hypertensive encephalopathy.

Effect of endothelin-1 in man: pretreatment with nifedipine, with indomethacin and with cyclosporine A

The rise in blood pressure following the intravenous administration of endothelin-1 remained unchanged in healthy male volunteers pretreated with either the calcium-channel antagonist nifedipine (10 mg orally), the cyclo-oxygenase inhibitor indomethacin (150 mg day-1 for three days) or the immunosuppressive agent cyclosporine (5 mg kg-1 body weight for five days). Following administration of nifedipine the rise in plasma concentrations of endothelin-1 during the infusion of the peptide was markedly higher (P less than 0.01) than during control experiments without nifedipine. It is concluded that, in healthy men, nifedipine, indomethacin and cyclosporine do not exert a major influence on the pressor action of endothelin-1. However, nifedipine apparently influences the elimination of endothelin-1 from the circulation in healthy men.

Single-dose sublingual nifedipine as the only treatment in hypertensive urgencies and emergencies

One hundred and eighteen patients with hypertensive urgencies and emergencies and diastolic blood pressure (DBP) at least 120 mm Hg by the cuff method were seen at the Emergency Care Department; none had received calcium channel blockers during the previous twelve hours. Patients with DBP of 120 to 139 mm Hg received 10 mg of sublingual nifedipine; patients with left ventricular hypertrophy or failure, renal disease, hypertensive encephalopathy, angina, papilledema, or a DBP over 140 mm Hg received 20 mg of the drug. The criterion for control was the achievement of a DBP of 100 mm Hg or less within sixty minutes of receiving sublingual nifedipine and maintenance of the effect until discharge. Control was achieved in all patients; a sixty-three-year-old man died of a brain hemorrhage after pulmonary edema and a DBP of 210 had been controlled; the other 117 were discharged to their attending physicians, either as outpatients or to a hospital ward. No patient developed hypotension, clinical or electrocardiographic signs of myocardial ischemia, or clinical signs of neurologic dysfunction. Practical, fast, safe, and dependable control of hypertensive urgencies and emergencies has made sublingual nifedipine the treatment of choice of such patients in the Emergency Care Department.

Management of hypertensive emergencies: changing therapeutic options

Rapid lowering of severe hypertension is essential to prevent irreversible damage to vital organs. The patient's clinical status should be evaluated, noting particularly cardiac, neurologic, and renal functions. Choice of treatment should be based on speed and efficacy of action and on hemodynamic, vascular, and renal consequences. It is also important to preserve circulatory homeostasis and vital organ function. Sodium nitroprusside, labetalol, diazoxide, and hydralazine have been used parenterally for rapid control of severe hypertension, but they do not always produce optimal, balanced hemodynamic effects. Calcium antagonists have been advocated because of their beneficial circulatory effects. Nicardipine, a new dihydropyridine calcium antagonist, produces significant antihypertensive effects, and when given intravenously, results in a rapid fall in blood pressure. Studies have confirmed that nicardipine is effective and safe in the management of severe hypertension and hypertensive crises. Because the aim of rapidly controlling severe hypertension is to prevent target organ dysfunction, nicardipine therapy offers a useful additional option in the clinical management of severe hypertension and hypertensive crises.

Oral labetalol in hypertensive urgencies

The response to incremental doses of oral labetalol in 16 patients with hypertensive urgencies is presented. After inadequate blood pressure control with 20 mg of intravenous furosemide, each patient received a 300 mg oral dose of labetalol. Subsequent oral doses of labetalol, 100 mg, were administered at 2-hour intervals, if the diastolic blood pressure remained greater than 100 mm Hg. The maximum dose of labetalol per patient was 500 mg. Five patients required only the initial 300 mg dose of labetalol. Two patients required further therapy for satisfactory blood pressure control. Mean arterial pressure fell from 156 +/- 12 mm Hg to 123 +/- 14 mm Hg.

Use of nifedipine in hypertension and Raynaud's phenomenon

The reduction of transmembranous calcium influx into vascular smooth muscle cells by calcium antagonists leads to a reduction of tension development and vascular tone. Nifedipine reduces forearm vascular resistance dose-dependently when infused into the brachial artery in patients with essential hypertension, attesting to its potent arterial vasodilator effects. This effect can be successfully utilized for the treatment of essential hypertension, where nifedipine acts by reducing increased peripheral vascular resistance, thereby normalizing the main hemodynamic derangement of hypertensive patients. In contrast to other direct-acting vasodilators, the antihypertensive effect is not accompanied by sympathetic reflex activation or volume retention, making it feasible to use nifedipine as monotherapy for hypertensive patients. Although the pathophysiologic disturbances leading to vasospasm are not clear, blockade of slow calcium channels is also effective for the treatment of Raynaud's phenomenon, reducing attack frequency, digital pain, and functional disability in many patients, particularly those with primary Raynaud's phenomenon.

Cerebral blood flow during the acute therapy of severe hypertension with oral clonidine

A major risk associated with the acute treatment of severe hypertension is a reduction in cerebral blood flow (CBF) with ischemic injury to the central nervous system. The authors studied CBF before and after the acute treatment of severe hypertension (diastolic blood pressure greater than 115 mm Hg) with clonidine in 13 patients. One patient did not reach goal blood pressure (diastolic blood pressure 105 mm Hg or a decrease by 30 mm Hg) after clonidine alone. In the remaining 12 patients, oral clonidine reduced supine blood pressure from 201.7 +/- 5.0/126.3 +/- 2.1 mm Hg to 149.4 +/- 5.3/96.8 +/- 1.7 mm Hg over an average time period of 85 +/- 7 minutes. Although mean CBF for the group did not change (72.6 +/- 4.2 v 73.7 +/- 3.5 mL/100 mg/min), a significant (greater than 10%) change occurred in 9 of the 12 patients (5 increases and 4 reductions). The magnitude and direction of the change were dependent upon initial CBF (r = -0.65, P less than .05); patients with low pretreatment CBF experienced an increase, whereas those with high initial flow exhibited a decrease. No significant adverse effects were observed. These data confirm previous reports that clonidine is effective in the acute treatment of severe hypertension and demonstrate that its effects on CBF are determined by the pretreatment levels of flow.

Acute effects of antihypertensive agents on cerebral blood flow in hypertensive rats

The acute effects of various antihypertensive agents on cerebral blood flow and mean arterial pressure (MAP) were studied in anesthetized (amobarbital 100 mg/kg) spontaneously hypertensive rats. Cerebral blood flow in the cortex and thalamus was measured by the hydrogen clearance method before and during a 60-min i.v. infusion of calcium antagonist (nifedipine), angiotensin converting enzyme inhibitor (captopril) or beta-blocker (propranolol). Nifedipine, 30 or 150 micrograms/kg per h, decreased dose dependently the MAP by 20 or 31%, and concomitantly increased cortical blood flow by 28 or 74%, and thalamic blood flow by 51 or 64%, respectively. Captopril, 10 or 100 mg/kg per h, decreased MAP by 7 or 14%, but changed cerebral blood flow minimally. In contrast, propranolol, 1.0 or 5.0 mg/kg per h, decreased MAP by 13 or 11%, with a concomitant reduction of cortical and thalamic blood flow by 20 or 15 and 33 or 37%, respectively. It is concluded that the changes in cerebral blood flow in response to hypotension are varied by antihypertensive drugs depending on the direct or indirect effect of the drugs (dilatation or constriction) on cerebral vessels. Nifedipine seems to dilate while propranolol constricts cerebral vessels.

The efficacy of beta-adrenoceptor and calcium-entry blockers in hypertensive blacks

The data on treatment of hypertension in black patients with beta-adrenoceptor blockers (BB) or calcium-entry blockers (CEB) have been reviewed. There is much evidence that in monotherapy BB are no better than inert placebo for the majority of hypertensive black patients. Their hypotensive action in blacks is less than that induced by other antihypertensive agents, mainly diuretics. Comparative evaluation of the responsiveness of blacks, whites, and Indians to BB therapy showed a poorer control of blood pressure (BP) among blacks than among nonblacks. However, when combined with diuretic therapy, BBs are equipotent in blacks and whites. The reasons for the hyporesponsiveness of black patients to BB therapy are not fully understood. On the other hand, CEBs appear to be as efficacious as diuretic therapy in hypertensive blacks. In addition, they lower blood pressure to the same extent in black and white patients. They are also proven to be effective adjunctive therapy to diuretics for hypertension in blacks. The reason for the better responsiveness of blacks to CEB therapy might include the severity of hypertension in blacks, their low plasma renin, their blunted sympathetic activity, and their high intracellular sodium concentration.