The student understands the primary disturbances, compensatory responses, decompensatory processes, and possible therapeutic interventions that pertain to various abnormal cardiovascular situations.
- Defines circulatory shock.
- Identifies the primary disturbances that can account for cardiogenic, hypovolemic, anaphylactic, septic, and neurogenic shock states.
- Lists the compensatory processes that may arise during shock.
- Identifies the decompensatory processes that may arise during shock and describes how these lead to irreversible shock states.
- Indicates how coronary artery disease may lead to abnormal cardiac function.
- Defines the term angina pectoris and describes the mechanisms that promote its development.
- Indicates the mechanisms by which various therapeutic interventions may alleviate angina and myocardial ischemia in association with coronary artery disease.
- Defines the term heart failure and differentiates between systolic and diastolic dysfunction.
- Identifies the short-term and long-term compensatory processes that accompany heart failure.
- Describes the advantages and disadvantages of the fluid accumulation that accompanies heart failure.
- Defines pulmonary and systemic arterial hypertension.
- Identifies the various factors that may contribute to the development of systemic hypertension.
- Describes the role of the kidney in establishing and/or maintaining systemic hypertension.
In this last chapter, some of the pathological situations that can interfere with the homeostatic functions of the cardiovascular system are introduced. It is not intended as an in-depth coverage of cardiovascular diseases but rather as an introductory presentation of how the physiological processes described previously are evoked and/or altered during various abnormal cardiovascular states. In each case there is generally a primary disturbance that evokes appropriate compensatory reflex responses. Often, however, pathological situations also lead to inappropriate “decompensatory processes,” which tend to accelerate the deterioration of cardiovascular function. Therapeutic interventions may be required and are often designed to limit or reverse these decompensatory processes. Students are again encouraged to review the summary of cardiovascular variables and their determinants in Appendix C because a thorough knowledge of this material will greatly help to understand the physiological consequences of these abnormalities.
A state of circulatory shock exists whenever there is a generalized, severe reduction in blood supply to the body tissues and the metabolic needs of the tissues are not met. Even with all cardiovascular compensatory mechanisms activated, arterial pressure is usually (though not always) low in shock.
In general, the shock state is precipitated either by severely depressed myocardial functional ability, by grossly inadequate cardiac filling due to low mean circulatory filling pressure or by profound systemic vasodilation. The first situation is called cardiogenic shock and occurs whenever cardiac pumping ability is compromised (eg, severe arrhythmias, abrupt valve malfunction, coronary occlusions, and myocardial infarction). The latter situations can be caused by any of the conditions itemized as follows that decrease central venous volume, ventricular filling or total peripheral resistance:
Hypovolemic shock accompanies significant hemorrhage (usually greater than 20% of blood volume), severe burns, chronic diarrhea, or prolonged vomiting. These situations can induce shock by depleting body fluids ...