Reduced blood flow to the skin layers may result in mottling or uneven, patchy discoloration of the skin

Cardiac ischemia may be asymptomatic or may cause chest pain, known as angina pectoris. It occurs when the heart muscle, or myocardium, receives insufficient blood flow. This most frequently results from atherosclerosis, which is the long-term accumulation of cholesterol-rich plaques in the coronary arteries. Ischemic heart disease is the most common cause of death in most Western countries and a major cause of hospital admissions.

Symptoms of cerebral infarction are determined by the parts of the brain affected. If the infarct is located in primary motor cortex, contralateral hemiparesis is said to occur. With brainstem localization, brainstem syndromes are typical: Wallenberg's syndrome, Weber's syndrome, Millard-Gubler syndrome, Benedikt syndrome or others.

Infarctions will result in weakness and loss of sensation on the opposite side of the body. Physical examination of the head area will reveal abnormal pupil dilation, light reaction and lack of eye movement on opposite side. If the infarction occurs on the left side brain, speech will be slurred. Reflexes may be aggravated as well.

There are various classification systems for a cerebral infarction.

- The Oxford Community Stroke Project classification (OCSP, also known as the Bamford or Oxford classification) relies primarily on the initial symptoms. Based on the extent of the symptoms, the stroke episode is classified as total anterior circulation infarct (TACI), partial anterior circulation infarct (PACI), lacunar infarct (LACI) or posterior circulation infarct (POCI). These four entities predict the extent of the stroke, the area of the brain affected, the underlying cause, and the prognosis.

- The TOAST (Trial of Org 10172 in Acute Stroke Treatment) classification is based on clinical symptoms as well as results of further investigations; on this basis, a stroke is classified as being due to (1) thrombosis or embolism due to atherosclerosis of a large artery, (2) embolism of cardiac origin, (3) occlusion of a small blood vessel, (4) other determined cause, (5) undetermined cause (two possible causes, no cause identified, or incomplete investigation).

Three progressive phases of mesenteric ischemia have been described:

- A "hyper active" stage occurs first, in which the primary symptoms are severe abdominal pain and the passage of bloody stools. Many patients get better and do not progress beyond this phase.

- A "paralytic" phase can follow if ischemia continues; in this phase, the abdominal pain becomes more widespread, the belly becomes more tender to the touch, and bowel motility decreases, resulting in abdominal bloating, no further bloody stools, and absent bowel sounds on exam.

- Finally, a "shock" phase can develop as fluids start to leak through the damaged colon lining. This can result in shock and metabolic acidosis with dehydration, low blood pressure, rapid heart rate, and confusion. Patients who progress to this phase are often critically ill and require intensive care.

Acute limb ischaemia can occur in patients through all age groups. Patients that smoke and have diabetes mellitus are at a higher risk of developing acute limb ischaemia. Most cases involve people with atherosclerosis problems.

Symptoms of acute limb ischaemia include:

- Pain

- Pallor

- Paresthesias

- Perishingly cold

- Pulselessness

- Paralysis

These symptoms are called "the six P's'"; they are commonly mis-attributed to compartment syndrome. One more symptom would be the development of gangrene. Immediate medical attention should be sought with any of the symptoms.

In late stages, paresthesia is replaced by anesthesia due to death of nerve cells.

In some cases, gangrene can occur within six hours of ischaemia.

Symptoms of mesenteric ischemia vary and can be acute (especially if embolic), subacute, or chronic.

Case series report prevalence of clinical findings and provide the best available, yet biased, estimate of the sensitivity of clinical findings. In a series of 58 patients with mesenteric ischemia due to mixed causes:

- abdominal pain was present in 95% (median of 24 hours duration). The other three patients presented with shock and metabolic acidosis.

- nausea in 44%

- vomiting in 35%

- diarrhea in 35%

- heart rate > 100 in 33%

- 'blood per rectum' in 16% (not stated if this number also included occult blood – presumably not)

- constipation in 7%

When a limb is ischemic in the non-acute (chronic) setting, the condition is alternatively called peripheral artery disease or critical limb ischemia, rather than ALI. In addition to limb ischemia, other organs can become ischemic, causing:

- Renal ischemia (nephric ischemia)

- Mesenteric ischemia

- Cerebral ischemia

- Cardiac ischemia

Up to 50% of people with PAD may have no symptoms. Symptoms of PAD in the legs and feet are generally divided into 2 categories:

1. Intermittent claudication—pain in muscles when walking or using the affected muscles that is relieved by resting those muscles. This is due to the unmet oxygen demand in muscles with use in the setting of inadequate blood flow.

2. Critical limb ischemia, consisting of:

Medical signs of PAD in the legs, due to inadequate perfusion, include:

- Noticeable change in color – blueness, or in temperature (coolness) when compared to the other limb.

- Buerger's test can check for pallor on elevation of limb and redness (rubor) on a change to a sitting position, in an assessment of arterial sufficiency.

- Diminished hair and nail growth on affected limb and digits

PAD in other parts of the body depends on the organ affected. Renal artery stenosis can cause renovascular hypertension.

Carotid artery disease can cause strokes and transient ischemic attacks.

CT angiography would be helpful in differentiating occlusive from non-occlusive causes of mesenteric ischaemia.

The signs and symptoms of carotid artery dissection may be divided into ischemic and non-ischemic categories:

"Non-ischemic signs and symptoms"

- Localised headache, particularly around one of the eyes.

- Neck pain

- Decreased pupil size with drooping of the upper eyelid (Horner syndrome)

- Pulsatile tinnitus

"Ischemic signs and symptoms"

- Temporary vision loss

- Ischemic stroke

Non-occlusive mesenteric ischemia occurs due to severe vasoconstriction of mesenteric vessels supplying the intestine. Acute abdominal pain is the only early acute symptom in those patients, which makes early diagnosis difficult.

The causes of internal carotid artery dissection can be broadly categorised into two classes: spontaneous or traumatic.

Peripheral artery disease (PAD) is a narrowing of the arteries other than those that supply the heart or the brain. When narrowing occurs in the heart, it is called coronary artery disease, while, in the brain, it is called cerebrovascular disease. Peripheral artery disease most commonly affects the legs, but other arteries may also be involved. The classic symptom is leg pain when walking which resolves with rest, known as intermittent claudication. Other symptoms including skin ulcers, bluish skin, cold skin, or poor nail and hair growth may occur in the affected leg. Complications may include an infection or tissue death which may require amputation; coronary artery disease, or stroke. Up to 50% of cases of PAD are without symptoms.

The main risk factor is cigarette smoking. Other risk factors include diabetes, high blood pressure, and high blood cholesterol. The underlying mechanism is usually atherosclerosis. Other causes include artery spasm. PAD is typically diagnosed by finding an ankle-brachial index (ABI) less than 0.90, which is the systolic blood pressure at the ankle divided by the systolic blood pressure of the arm. Duplex ultrasonography and angiography may also be used. Angiography is more accurate and allows for treatment at the same time; however, it is associated with greater risks.

It is unclear if screening for disease is useful as it has not been properly studied. In those with intermittent claudication from PAD, stopping smoking and supervised exercise therapy improves outcomes. Medications, including statins, ACE inhibitors, and cilostazol also may help. Aspirin does not appear to help those with mild disease but is usually recommended in those with more significant disease. Anticoagulants such as warfarin are not typically of benefit. Procedures used to treat the disease include bypass grafting, angioplasty, and atherectomy.

In 2015 about 155 million people had PAD worldwide. In the developed world it affects about 5.3% of 45 to 50 years olds and 18.6% of 85- to 90-year-olds. In the developing world it affects 4.6% of people between the ages of 45 to 50 and 15% of people between the ages of 85 to 90. In the developed world PAD is equally common among men and women while in the developing world women are more commonly affected. In 2015 PAD resulted in about 52,500 deaths up from 16,000 deaths in 1990.

Reperfusion injury or reperfusion insult, sometimes called ischemia-reperfusion injury (IRI) or reoxygenation injury, is the tissue damage caused when blood supply returns to tissue ("" + "perfusion") after a period of ischemia or lack of oxygen (anoxia or hypoxia). The absence of oxygen and nutrients from blood during the ischemic period creates a condition in which the restoration of circulation results in inflammation and oxidative damage through the induction of oxidative stress rather than (or along with) restoration of normal function.

Hyperaemia, hyperæmia, or hyperemia (Greek ὑπέρ (hupér, "over") + αἷμα (haîma, “blood”)) is the increase of blood flow to different tissues in the body. It can have medical implications but is also a regulatory response, allowing change in blood supply to different tissues through vasodilation. Clinically, hyperaemia in tissues manifest as erythema (redness of the skin) because of the engorgement of vessels with oxygenated blood. Hyperaemia can also occur due to a fall in atmospheric pressure outside the body.

An arterial thrombus or embolus can also form in the limbs, which can lead to acute limb ischemia.

Cavernous sinus thrombosis is a specialised form of cerebral venous sinus thrombosis, where there is thrombosis of the cavernous sinus of the basal skull dura, due to the retrograde spread of infection and endothelial damage from the danger triangle of the face. The facial veins in this area anastomose with the superior and inferior ophthalmic veins of the orbit, which drain directly posteriorly into the cavernous sinus through the superior orbital fissure. Staphyloccoal or Streptococcal infections of the face, for example nasal or upper lip pustules may thus spread directly into the cavernous sinus, causing stroke-like symptoms of double vision, squint, as well as spread of infection to cause meningitis.

A study of aortic cross-clamping, a common procedure in cardiac surgery, demonstrated a strong potential benefit with further research ongoing.

Symptoms of arterial gas embolism include:

- Loss of consciousness

- Cessation of breathing

- Vertigo

- Convulsions

- Tremors

- Loss of coordination

- Loss of control of bodily functions

- Numbness

- Paralysis

- Extreme fatigue

- Weakness in the extremities

- Areas of abnormal sensation

- Visual abnormalities

- Hearing abnormalities

- Personality changes

- Cognitive impairment

- Nausea or vomiting

- Bloody sputum

- Symptoms of other consequences of lung overexpansion such as pneumothorax, subcutaneous or mediastinal emphysema may also be present.

Reactive hyperaemia or venous hyperemia is the transient increase in organ blood flow that occurs following a brief period of ischaemia. Following ischaemia there will be a shortage of oxygen and a build-up of metabolic waste.

This is commonly tested in the legs using Buerger's test.

Reactive hyperaemia often occurs as a consequence of Raynaud's phenomenon, where the vasospasm in the vasculature leads to ischaemia and necrosis of tissue and thus a subsequent increase in blood flow to remove the waste products and clear up cell debris.

Small amounts of air often get into the blood circulation accidentally during surgery and other medical procedures (for example, a bubble entering an intravenous fluid line), but most of these air emboli enter the veins and are stopped at the lungs, and thus a venous air embolism that shows any symptoms is very rare.

The clinical presentation of CST can be varied. Both acute, fulminant disease and indolent, subacute presentations have been reported in the literature.

The most common signs of CST are related to anatomical structures affected within the cavernous sinus, notably cranial nerves III-VI, as well as symptoms resulting from impaired venous drainage from the orbit and eye.

Classic presentations are abrupt onset of unilateral periorbital edema, headache, photophobia, and bulging of the eye (proptosis).

Other common signs and symptoms include:

Ptosis, chemosis, cranial nerve palsies (III, IV, V, VI). Sixth nerve palsy is the most common. Sensory deficits of the ophthalmic and maxillary branch of the fifth nerve are common. Periorbital sensory loss and impaired corneal reflex may be noted. Papilledema, retinal hemorrhages, and decreased visual acuity and blindness may occur from venous congestion within the retina. Fever, tachycardia and sepsis may be present. Headache with nuchal rigidity may occur. Pupil may be dilated and sluggishly reactive. Infection can spread to contralateral cavernous sinus within 24–48 hours of initial presentation.

Blue toe syndrome is a situation that may reflect atherothrombotic microembolism, causing transient focal ischaemia, occasionally with minor apparent tissue loss, but without diffuse forefoot ischemia. The development of blue or violaceous toes can also occur with trauma, cold-induced injury, disorders producing generalized cyanosis, decreased arterial flow, impaired venous outflow, and abnormal circulating blood.

The terms "blue toe syndrome", "grey toe syndrome" and "purple toe syndrome" are sometimes used interchangeably.

Studies may include echocardiography, thoracic and abdominal CT or MRI, peripheral arterial run off imaging studies, hypercoagulopathy labs, and interrogation of syndromes that lead to peripheral vascular pathology.

Renal ischemia also known as"nephric ischaemia", is the deficiency of blood in one or both kidneys or nephrons, usually due to functional constriction or actual obstruction of a blood vessel.