What is Impaired Tissue Perfusion?
Ineffective tissue perfusion is a state in which an individual has a decrease in oxygen resulting in failure to nourish the tissues at the capillary level.
Tissue perfusion is a critical parameter for tissue survival and function, and both relative and absolute perfusion assessments are highly relevant for both diagnosis and evaluation of the therapy response.
Sometimes situations occur where this exchange of gases between the blood and the cells is disrupted, meaning the cells (and ultimately the tissues and organs) stop getting adequate oxygen supply. The body can’t function without oxygen, so obviously this is a problem. When tissues don’t receive enough oxygen through the capillaries, this is called ineffective tissue perfusion.
Many conditions can disrupt the exchange of oxygen and carbon dioxide, but diabetes, obesity, anemia, high blood pressure, and coronary artery disease are some of the more common risk factors that can cause ineffective tissue perfusion. We can further classify the type of ineffective tissue perfusion based on the part of the body affected. For example, there’s renal (meaning kidney), cerebral (meaning brain), cardiopulmonary (meaning heart and lungs), gastrointestinal (meaning digestive tract), and peripheral (meaning affecting the extremities) ineffective tissue perfusion.
Common Risk Factors
Small arteries in diabetic subjects, whether hypertensive or normotensive, exhibit severe hypertrophic remodeling, and histological analysis of skeletal muscle biopsy samples reveals capillary rarefaction in subjects with type 2 diabetes. Histological capillary density is inversely related to fasting plasma glucose and fasting insulin levels and positively related to insulin sensitivity in nondiabetic individuals. Microvascular permeability to large molecules such as albumin is increased in diabetes, a process that is linked to hyperglycemia and ROS
In humans, coronary flow reserve is significantly lower in obese than in nonobese subjects, and capillary recruitment is reduced in nondiabetic obese individuals compared with lean control subjects. Even in a sample of healthy children (11 to 14 years of age), microvascular function was negatively correlated with adiposity. Thus, obesity appears to have an independent effect on microvascular function.
Coronary flow reserve decreases progressively with age in subjects without coronary artery disease, from approximately 4 at 30 years to 3 at 65 years of age, largely due to increased basal myocardial blood flow.
Tobacco smoking acutely impairs capillary recruitment, and thus hyperemic blood flow increases in skin and coronary flow reserve is reduced in established smokers. Coronary flow reserve in smokers can be improved by administration of antioxidant vitamin C, which suggests that smoking-related oxidative stress is an important mechanism.
Individuals with hypercholesterolemia without coronary artery disease have reduced coronary flow reserve, and coronary flow reserve is inversely correlated with LDL cholesterol. A reduction in coronary flow reserve can be detected in healthy young men (mean age 31 years) with familial hypercholesterolemia, which suggests that microvascular abnormality is detectable early in the atherosclerotic process.
Given the relationships between individual cardiovascular risk factors with measures of microvascular status, it is not surprising that the overall Framingham risk score is inversely correlated with skin capillary recruitment, maximal skin capillary density, and coronary flow reserve.
Ineffective Tissue Perfusion is characterized by the following signs and symptoms:
- Abnormal arterial blood gases
- Altered respiratory rate outside of acceptable parameters
- Capillary refill >3 seconds
- Chest pain
- Chest retraction
- Nasal flaring
- Sense of “impending doom”
- Use of accessory muscles
- Altered mental status
- Behavioral changes
- Changes in motor response
- Changes in pupillary reactions
- Difficult in swallowing
- Extremity weakness or paralysis
- Speech abnormalities
- Abdominal distention
- Abdominal pain or tenderness
- Hypoactive or absent bowel sounds
- Altered sensations
- Altered skin characteristics (hair, nails, moisture)
- Cold extremities
- Dependent, blue, or purple skin color
- Diminished arterial pulsations
- Positive Homan’s sign
- Skin discolorations
- Skin temperature changes
- Skin color pale on elevation, color does not return on lowering the leg
- Slow healing of lesions
- Weak or absent pulses
- Altered blood pressure outside of acceptable parameters
- Elevation in BUN/creatinine ratio
- Oliguria or anuria
Damage, Complications, and Prognosis
Microvascular abnormalities that lead to impaired tissue perfusion appear to represent a generalized condition that affects multiple tissues and organs. For example, in hypertension, coronary flow reserve is correlated with the media:lumen ratios of small arteries in biopsies of subcutaneous fat. Dilatation of venules in the retina independently predicts progression of cerebral small-vessel disease, and in diabetes, reduced coronary flow reserve predicts the occurrence of retinopathy.
Impaired tissue perfusion may be involved in target-organ damage and complications that involve several vascular beds. For the coronary microcirculation, an obvious example associated with both hypertension and diabetes is the occurrence of myocardial ischemia and angina in the presence of angioscopically normal epicardial coronary arteries, also known as cardiac syndrome X. Impaired myocardial perfusion may also be an important factor in the development of hypertensive heart failure and may lead to localized ischemia and disturbed patterns of electrical activity that constitute a substrate for serious arrhythmias. In the case of renal disease, glomerular and peritubular capillary rarefaction has been noted in different animal models and in human progressive renal disease, and it precedes the development of impaired perfusion and chronic hypoxia. It has been suggested that hypoxia may be the common factor linking many forms of progressive renal disease.
Microvascular abnormality is also a predictor of prognosis. In hypertensive patients, the media:lumen ratio of peripheral small arteries is a strong independent predictor of cardiovascular events. Among individuals with normal or minimally diseased coronary arteries, reduced coronary flow reserve is an independent predictor of cardiovascular events within the next decade. Finally, in patients with chest pain and angiographically normal arteries, coronary flow reserve <3 is associated with a 6-fold increase in all-cause mortality risk compared with coronary flow reserve >3 during 8.5 years of follow-up.