Diastole

FIGURE 2.18 Inotropic and lusitropic responses of guinea pig left atria to (3-adrenoceptor stimulation. Panels A to C isometric tension waveforms of cardiac contraction (ordinates are mg tension abscissae are msec), (a) Effect of 0.3 nM isoproterenol on the waveform. The wave is shortened due to an increase in the rate of diastolic relaxation, whereas no inotropic response (change in peak tension) is observed at this concentration, (b) A further shortening of waveform duration (lusitropic response) is observed with 3 nM isoproterenol. This is concomitant with positive inotropic response (increase maximal tension), (c) This trend continues with 100 nM isoproterenol, (d) Dose-response curves for ino tropy (filled circles) and lusitropy (open circles) in guinea pig atria for isoproterenol, (e) Dose-response curves for inotropy (filled circles) and lusitropy (open circles) in guinea pig atria for the P-adrenoceptor partial agonist prenalterol. Data redrawn from [6]. 

Kenakin, T. P., Ambrose, J. R., and Irving, P. E. (1991). The relative efficiency of beta-adrenoceptor coupling to myocardial inotropy and diastolic relaxation Organ-selective treatment of diastolic dysfunction. J. Pharmacol. Exp. Ther. 257 1189—1197. 

As a result of such studies hypertension has been operationally defined as the blood pressure level above which therapeutic intervention has clinical benefit. As increasingly aggressive intervention has continued to demonstrate benefits, this level has gradually reduced over time and is commonly defined as systolic blood pressure>l40 mmHg and/or diastolic blood pressure >90 mmHg (Table 1). Isolated systolic hypertension is defined as systolic blood pressure >140 mmHg and diastolic blood pressure <90 mmHg. 

Category Systolic [mm Hg] I Diastolic [mm Hg] Stroke mortality relative risk... 

The higher category applies, if systolic and diastolic blood pressure values of a patient fall into different categories. 

Clarkson CW, Hondeghem LM (1985) Mechanism for bupivacaine depression of cardiac conduction fast block of sodium channels during the action potential with slow recovery from block during diastole. Anesthesiology 62 396-405... 

Systolic and Diastolic Blood Pressure and Pulse Pressure 1175... 

Systolic pressure, or maximum blood pressure, occurs during left ventricular systole. Diastolic pressure, or minimum blood pressure, occurs during ventricular diastole. The difference between systolic and diastolic pressure is the pulse pressure. While diastolic blood pressure has been historically been used as the most relevant clinical blood pressure phenotype, it has now been clearly established that systolic blood pressure is the more important clinical predictor for cardiovascular morbidity and mortality. More recently, additional attention is focussed on the importance of pulse pressure, i.e. the blood pressure amplitude, as a predictive factor for cardiovascular disease. 

A significant decrease in blood pressure (systolic or diastolic) or a systolic pressure below 100 mm Hg... 

Explains that a slight change in readings is normal, but if a drastic change in either or both the systolic or diastolic readings occurs, the patient should contact the primary health care provider as soon as possible. 

Once essential hypertension develops, management of this disorder becomes a lifetime task. When a direct cause of the hypertension can be identified, the condition is described as secondary hypertension. Among the known causes of secondary hypertension, kidney disease ranks first, with tumors or other abnormalities of the adrenal glands following. In malignant hypertension the diastolic pressure usually exceeds 130 mm Hg. In secondary hypertension,... 

In most individuals, the systolic pressure increases sharply with age, whereas the diastolic pressure increases until about age 55 years and then declines. Older individuals with an elevated systolic pressure have a condition known as isolated systolic hypertension (ISH). When the systolic pressure is high, blood vessels become less flexible and stiffen, leading to cardiovascular disease and kidney damage. Research indicates that treating ISH saves lives and reduces illness. The treatment is the same for ISH as for other forms of hypertension. 

Notify the primary care provider if the diastolic pressure suddenly increases to 130 mm Hg or higher you may have malignant hypertension. 

The application of high concentrations (above 5 x 10 g/mL) of MTX caused a biphasic inotropic change and gradual rise in diastolic tension of the atria. Furthermore, MTX produced various arrhythmic movements and cardiac arrest in the guinea pig left and right atria (Figure 4). 

To characterize the responses to PbTx-2, five dose rates (0, 12.5, 25, 50, and 100 ig/kg/hr in 2 ml saline) were infused into the jugular catheters of rats (four per group). Heart rates, systolic and diastolic arterial blood pressures, pulse pressures, respiratory rates, core and peripheral body temperatures, lead VI0 ECCjs, and arterial blood gases were monitored. Clinical signs and behaviors were recorded by video camera. After infusion, animals were monitored for 6 hr, by which time most had either died or recovered to near baseline physiological levels. 

If a stroke patient receives intravenous (IV) thrombolysis, care often continues in the ED until the patient arrives in the ICU. Close monitoring must continue during this time, with special attention to the blood pressure. The blood pressure is most commonly checked via an arm cuff, since the placement of invasive lines (e.g., arterial catheterization) is relatively contraindicated once the patient has received intravenous thrombolysis (unless the situation is emergent and mandates such treatment). The systolic pressure must not exceed 185 mm Hg, and the diastolic pressure limit should be 110 mm Hg. Should the blood pressure exceed these limits, IV antihypertensive agents should be administered. IV pushes of labetolol (10-20 mg over 1-2 minutes) may be effective, but if patients are refractory to these initial measures then a continuous infusion of labetolol (0.5-2.0 mg/minute), nicardipine (5-15 mg/hour), or nitro-prusside (0.25-10 mg/kg/minute) may be necessary to keep the patient s blood pressure within the range. There will be a more detailed discussion of these antihypertensive agents, including their side effect profiles, later in this chapter. 

Essential hypertension, whose prevalence is increased nearly two-fold in the diabetic population, may be another source of free-radical activity. The vascular lesions of hypertension can be produced by free-radical reactions (Selwign, 1983). In the recent Kuopio Ischaemic Heart Risk Factor Study in Finnish men, a marked elevation of blood pressure was associated with low levels of both plasma ascorbate and serum selenium (Salonen etal., 1988). A few studies report a hypotensive effect of supplementary ascorbate in patients with hypertension, but the actual changes in both systolic and diastolic pressure after ascorbate were not statistically significant in comparison with placebo (Trout, 1991). 

Reduce mean arterial pressure (MAP) by 20-25% or to a diastolic blood pressure of 110 mmHg in hypertensive emergencies... 

Antihypertensive agents should be avoided unless the systolic blood pressure is >220 mmHg or the diastolic blood pressure is >120 mmHg (see Table 3.2 for management)... 

Patients who are otherwise eligible (except blood pressure) for alteplase, should have their blood pressure lowered cautiously to a systolic <185 mmHg and a diastolic <110 mmHg... 

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