Blood Pressure Contains Clinical Information

Blood Pressure
(BP)

absolute blood pressureblood pressure changesblood pressure rhythmsblood pressure pulse wave

Information

Absolute values

Changes

Rhythms

Pulsewaves

General
Absolute values are the most popular form of BP - usually expressed in terms of the systolic pressure over the diastolic pressure (e.g. 140/80 mmHg)The human autonomic nervous systems controls BP and tries to keep it as stable and constant as possible. Unphysiological changes like hypertensive or hypotensive episodes or even massive instabilities indicate problems of the cardiovascular system.

Physiological rhythms are related to the different cardiovascular control mechanisms. The origins of these rhythms are either related to breathing or to the so called "Mayer waves". Different computer-aided markers can be derived from physiological rhythms - either from the BP-signal alone or in combination with other cardiovascular signals like ECG, respiratory and/or impedance.

 

BP - pulsewaves demonstrate the true behavior of the cardiovascular system: The steep increase of BP from diastolic minimum to the systolic maximum refers to heart contraction and the resulting ejection of blood into the aorta. The dicrotic notch in the middle of the pulse results from the closing of the aortic valve. Thereafter, BP decreases along an unloading curve, indicating the Windkessel function of the aorta.

A mathematical analysis of the pulsewave allows for an estimation of cardiac output (CO) and further parameters (SV, SVR/TPR, ...). Further pulsewave analysis may provide information about vascular condition and arterial stiffness.

 

Anesthesia

Before induction of anesthesia, initial BP measurment is mandatory

  • High BP values indicate hypertension or poor adjustment of hypertension therapy, which may be an indicator for different reaction to narcotics.
  • Hypotensive values combined with tachycardia may be an indicator for hypovolemia.
  • Hypotensive values in patients with pre-existing cardiac conditions may lead to heart failure during anesthesia.

 

Episodes of instabilities may indicate:
  • Heart failure, shock, ...

Hypotensive episodes:

  • may indicate bleeding, volume loss, unnecessary depth of anesthesia, high PEEP,
  • may cause an increase of complication rate in combination with tachycardia, ...
  • results in decreased organ perfusion

Hypertensive episodes may cause:

  • Hemorrhage, aneurysms, ...

In anesthetized patients, respiratory related BP-rhythms are predominant.

This "respiratory swing" is a physiological rhythm which has its origin in breathing-induced changes in venous return. The numerical value of "respiratory swing" is called "Pulse Pressure Variation" (PPV). High PPV indicates decreased venous return because the heart acts in the steep (left) portion of the Frank-Starling curve. Thus, increased PPV indicates reduced cardiac preload, volume responsiveness of the patient and, as a consequence, fluid administration is recommended.

 

Cardiac outputobtained from pulsewave analysis allows for goal directed therapy and fluid management during anesthesia.

Beside the calculation of CO, displaying the real-time BP-signal has several advantages:

  • Real-time monitoring of BP-curves give feedback about proper sensor placement and correct device function.
  • Pulsewave shape indicates cardiac filling pressures - this is the reason why pulsewave analysis can estimate cardiac output.
Cardiology
  • Hypotensive and hypertensive values in patients with pre-existing cardiac conditions may indicate heart problems.

  • High BP values indicate hypertension or poor adjustment of hypertension therapy.

 

BP instabilities may indicate cardiovascular problems. Beat-to-beat tracking of BP together with other vital signs like ECG may help to diagnose the problems.

Cardiovascular performance markers can be computed from physiological rhythms like blood pressure variability, baroreceptor reflex sensitivity and others. These parameters are related to the autonomic nervous system and in more detail to sympathetic and parasympathetic tone. In addition, decreased baroreflex sensitivity indicates impaired cardiac performance after myocardial infarction.

 

Cardiac output and further cardiac performance markers can be derived from pulsewave analysis. The slope of the systolic upstroke can be related to the inotropic state of the heart, and together with systolic pressure, it is used for the optimization of pacemakers.

Further, special algorithms can estimate cardiac output, stroke volume and total peripheral resistance.

Hypertensiology

Absolute values of BP are the main parameters in the field of hypertensiology. The limitations of single values should be well known by the physician ("white coat effect") as well as limitations of sphygmomanometers.

 

 

In the future, cardiovascular and autonomic performance markers computed from physiological rhythms may help to optimize the therapy of hypertension.

In the future, cardiac output and further cardiac performance markers computed with pulsewave analysis methods may help to optimize the therapy of hypertension. Parameters for arterial stiffness may give further information about the origin of hypertension.

Syncope Assessment

Absolute values of BP do not necessarily indicate susceptibility of syncopes - not even hypotensive values. State-of-the-art syncope assessment must investigate BP changes in a well defined protocol including a special orthostatic maneuver (e.g. tilt table testing or active standing "Schellong" test).

 

Guideline conforming syncope assessment tracks beat-to-beat BP drops during orthostasis. Depending on the recorded hemodynamic changes, syncope is classified and diagnosed.

 

Autonomic markers, which are related to parasympathetic (vagal) tone indicate vasovagal dysfunction during orthostasis.Total peripheral resistance - derived from mean BP and CO - is an additional marker that gives information about the origin of syncope.
Neurology

High BP values indicate hypertension or poor adjustment of hypertension therapy. The knowledge of poor adjustment and mode of action of the drugs used may give neurological insight.

 

Increase and decrease of BP in correlation with heart rate can be used as an indicator for mental stress.Autonomic markers are indicators for sympathetic and parasympathetic tone.Total peripheral resistance - derived from mean BP and CO - can possibly be used as an additional indicator of sympathetic drive.
Sports Medicine

High BP values indicate hypertension or poor adjustment of hypertension therapy. Both must be considered when creating individual sports activity programs.

 

BP tracking during exercise can be used for the evaluation of physical fitness.

Autonomic markers are indicators for sympathetic and parasympathetic tone. Especially the ability to relax after physical activity, indicated by the recurrence of parasympathetic tone as well as sympathetic reserve, is of interest.

 

Total peripheral resistance - derived from mean BP and CO - can possibly be used as an additional indicator of sympathetic drive.

 

Preventive Medicine

High BP values indicate hypertension or poor adjustment of hypertension therapy.

 

BP response after special tests may indicate cardiovascular performance in the future.

In the future, cardiovascular and autonomic performance markers computed from physiological rhythms may be used for preventive medicine.

 

Cardiac output as well as further cardiovascular markers computed with pulsewave analysis may help to predict diseases.

 

The information table contains typical examples and does not claim to be complete. References to the examples can be requested in writing via This email address is being protected from spambots. You need JavaScript enabled to view it..


 

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