**3. Etiological classification of neurological complications**

188 Aortic Valve Surgery

Neurological complications (NC) associated with postoperative aortic valve surgery are relatively frequent in spite of technical advances in surgery and CPB systems, and they give rise to an increase in morbidity and mortality, increased lengths of stays in hospital and rising costs after discharge from hospital. Therefore, the main purpose of the medical team responsible for assessing and treating patients who require cardiac surgery is to conduct a proper assessment and preventive measures for these complications and, once they have occurred, to minimise the physical, psychological, social and economic consequences for the

**2. Changes in cerebral blood flow during CPB with extracorporeal pump** 

The brain weighs about 2% of total body weight. Cerebral blood flow accounts for 10 to 15% of cardiac output. Cerebral blood flow in normothermia is 50 millilitres (ml)/100 grams (g) of tissue per minute (min) and oxygen consumption is 3.5 ml/100 g tissue / min. Cerebral circulation is unusual in its self-regulating ability performed through the arteries of medium and large size. The ability for self-regulation acts at between 50 and 155 millimetres of mercury (mm Hg) for systolic blood pressure in normal conditions, but below 50 mm Hg brain irrigation is directly dependent on the amount of flow to this area. In cases of severe hypertensive disease or cerebral vascular disease, the lower limits can be much higher

At normothermia, there is permanent neurological damage when there is a cerebral perfusion defect or flow is less than 125 ml/min for more than 7 minutes. Vascular territories with little reserve, such as the border zones of cerebral arteries, the spinal cord and basal ganglia are the most sensitive and most affected by a situation of ischemia. The hippocampal cells and cerebellar Purkinje cells are also particularly sensitive to ischemia.

Fig. 2. Cannulation in ascending aorta and right atrium in preparation for using cardiopulmonary bypass. Similarly, the coronary sinus is cannulated to administer

patient and their family.

cardioplegic solution

(Sotaniemi et al., 1986, Caplan et al., 1999).

The series that we can see in the bibliography show that there is a greater number of NCs in valve replacement surgery than in coronary artery bypass grafting, with an incidence of stroke or transient ischemic attack of 1.7% in patients undergoing coronary artery bypass grafting, 3.6% in those with a simple valve replacement, 3.3% in those undergoing both procedures and 6.7% in those who undergo a multiple valve replacement (Boeken et al., 2005)

The NCs in these patients may affect the brain, the spinal cord and peripheral nerves, and the most common of these are often strokes, anoxic-ischemic encephalopathy, epilepsy and brachial plexus injuries

Among the many threats to which the Nervous System is subjected during cardiovascular surgery, we can highlight the following: embolism, CPB, general anaesthetics, hypothermia, aortic clamping, and in some cases circulatory arrest. (Mills, 1995; Roach et al., 1996; Hallow et al, 1999).

According to the guidelines of the American College of Cardiology / American Heart Association as regards heart surgery for 1999, neurological complications are classified as type I deficiency, including focal lesions such as stroke and stupor or coma, and type II when intellectual functioning and memory are affected, and seizures. However, there are intermediate forms that are difficult to classify (Roach et al., 1996).

**Strokes** or **cerebrovascular accidents** are on the whole 80% ischemic and 20% hemorrhagic (use of anticoagulants). 50% of the ischemic ones are usually caused by atherothrombotic reasons, 25% are lacunar (associated with chronic arterial high blood pressure), 20% are cardioembolic, and the remaining 5% involve the ones we usually include in cardiac surgery: heart attacks in the border zone area between the anterior cerebral artery and the middle cerebral artery (called man-in-the-barrel syndrome due to its clinical consequences), and between the latter and the posterior cerebral artery. (Sanz et al., 2008)

In cardiac surgery, the incidence of stroke ranges from 0.7 to 3.8% when assessed retrospectively or between 4.8 to 5.2% if assessed prospectively (Bocerius, 2004). This is the main cause of morbidity in people undergoing cardiac surgery. Its frequency is 5% higher in patients with valvular disease, either due to an increased frequency of atrial fibrillation in these cases or because the valve surgery requires opening the heart chambers and increases the likelihood of air embolization, unlike in coronary surgery.

It may appear early on, occurring during surgery, and become apparent when the patient awakes, or later after normal awakening with no focal neurological damage apparent. Both the early and late kinds have a high hospital mortality of 41% and 13% respectively. (Hogue et al, 1999).

Strokes cause major disability and high rehabilitation costs because these patients most often require the use of different technical aids or orthotics for walking, wheelchairs, adaptation of their home due to architectural barriers, help from third parties and in some cases the everyday need for health care staff, requiring admission to specialised homes.

Neurological Complications in Aortic Valve Surgery and Rehabilitation Treatment Used 191

impairment of cognitive functions, a reduced level of consciousness that is sometimes prolonged, hallucinations, and increased or decreased psychomotor activity. Its incidence ranges from 3 to 12% and though it involves high mortality (7.5%) this is usually lower than that of a stroke, and has an average hospital stay double that of the usual stay. Encephalopathy in these patients may be metabolic (disorders in the internal environment), pharmacological (drug toxicity), hypoxic ischemic (hypotension) or due to multiple causes

**Epilepsy** usually occurs as a result of diffuse encephalopathy, a stroke, and in patients with previous epilepsy, and is usually related to the presence of metabolic disorders (generalized epilepsy) or a structured lesion (focal epilepsy). It occurs in 0.3 and 10% of cases and does

Effects on the **spinal cord** are usually diagnosed by the appearance of paraparesis in connection with a spinal cord infarction related to hypotension in the border zone or clamping of the aorta. The effects appear most often in reconstructive aortic aneurysms, dissections or traumatic rupture, as well as in valve repairs and the use of intra-aortic

The most common injuries to the **Peripheral Nervous System** are **brachial plexus neuropathy**, **recurrent laryngeal nerve injury** and **phrenic nerve injury**, almost all related to compression neuropathy of a mechanical nature, due to fracture of the first rib by





We must rule out other types of polyneuropathy such as ICU, produced by malnutrition or

**Extrapyramidal system damage:** especially choreoathetosis, whose frequency ranges from 1-12% of patients with neurological complications. This is most often associated with hypothermia and total cardiac arrest. It appears between the 2nd and 6th days after surgery and usually decreases in intensity over time, although it may leave significant hypotonia. **Neuropsychological disorders:** these are assessed by means of memory, intelligence, visual acuity and motor tests. Diffuse disorders can appear in up to 80% of cases in the immediate postoperative period and up to 20-40% still persist two months after surgery. They are more common at older ages. They appear as the patient's subjective sensation of loss of concentration, alertness, memory, learning etc. (Asenbaum et al, 1991; Bendszus et

Table 1 shows a summary of the most common complications in cardiac surgery in general.


(the aforementioned ones plus sepsis, use of balloon counterpulsation).

excessive intraoperative traction exerted on the sternum and chest wall.

the deficits are usually transient. (Benecke et al, 1988).

not often lead to epilepsy.

balloon counterpulsation.

arch.

al, 2002).

protection (Beran et al, 2008).

fibular head on a hard surface.

deficits such as phosphorus.

Fig. 3. Sagittal cross-section MRI image showing effects firstly on the cortex of both hemispheres of the brain in the superior fronto-parietal regions and bilaterally. Bilateral basal ganglia are also affected, especially in the left thalamus and both heads of the caudate nuclei. Infarction in the border zone. Man in a barrel syndrome

Fig. 4. Sagittal cross-sectional MRI image showing a hyperintense lesion in T2 (which was T1 hypointense) from D7 to L2, compatible with secondary spinal cord ischemia with aortic arch surgery. (Taken from Martin C et al, 2007)

**Encephalopathy** is usually secondary to a diffuse cerebral injury, and is believed to originate from multiple microembolic events or hypoperfusion (Jacobs et al, 1998). This clinical situation manifests itself in various ways, but it is diagnosed as a state of global

Fig. 3. Sagittal cross-section MRI image showing effects firstly on the cortex of both hemispheres of the brain in the superior fronto-parietal regions and bilaterally. Bilateral basal ganglia are also affected, especially in the left thalamus and both heads of the caudate

Fig. 4. Sagittal cross-sectional MRI image showing a hyperintense lesion in T2 (which was T1 hypointense) from D7 to L2, compatible with secondary spinal cord ischemia with aortic

**Encephalopathy** is usually secondary to a diffuse cerebral injury, and is believed to originate from multiple microembolic events or hypoperfusion (Jacobs et al, 1998). This clinical situation manifests itself in various ways, but it is diagnosed as a state of global

nuclei. Infarction in the border zone. Man in a barrel syndrome

arch surgery. (Taken from Martin C et al, 2007)

impairment of cognitive functions, a reduced level of consciousness that is sometimes prolonged, hallucinations, and increased or decreased psychomotor activity. Its incidence ranges from 3 to 12% and though it involves high mortality (7.5%) this is usually lower than that of a stroke, and has an average hospital stay double that of the usual stay. Encephalopathy in these patients may be metabolic (disorders in the internal environment), pharmacological (drug toxicity), hypoxic ischemic (hypotension) or due to multiple causes (the aforementioned ones plus sepsis, use of balloon counterpulsation).

**Epilepsy** usually occurs as a result of diffuse encephalopathy, a stroke, and in patients with previous epilepsy, and is usually related to the presence of metabolic disorders (generalized epilepsy) or a structured lesion (focal epilepsy). It occurs in 0.3 and 10% of cases and does not often lead to epilepsy.

Effects on the **spinal cord** are usually diagnosed by the appearance of paraparesis in connection with a spinal cord infarction related to hypotension in the border zone or clamping of the aorta. The effects appear most often in reconstructive aortic aneurysms, dissections or traumatic rupture, as well as in valve repairs and the use of intra-aortic balloon counterpulsation.

The most common injuries to the **Peripheral Nervous System** are **brachial plexus neuropathy**, **recurrent laryngeal nerve injury** and **phrenic nerve injury**, almost all related to compression neuropathy of a mechanical nature, due to fracture of the first rib by excessive intraoperative traction exerted on the sternum and chest wall.


We must rule out other types of polyneuropathy such as ICU, produced by malnutrition or deficits such as phosphorus.

**Extrapyramidal system damage:** especially choreoathetosis, whose frequency ranges from 1-12% of patients with neurological complications. This is most often associated with hypothermia and total cardiac arrest. It appears between the 2nd and 6th days after surgery and usually decreases in intensity over time, although it may leave significant hypotonia.

**Neuropsychological disorders:** these are assessed by means of memory, intelligence, visual acuity and motor tests. Diffuse disorders can appear in up to 80% of cases in the immediate postoperative period and up to 20-40% still persist two months after surgery. They are more common at older ages. They appear as the patient's subjective sensation of loss of concentration, alertness, memory, learning etc. (Asenbaum et al, 1991; Bendszus et al, 2002).

Table 1 shows a summary of the most common complications in cardiac surgery in general.

Neurological Complications in Aortic Valve Surgery and Rehabilitation Treatment Used 193

membrane oxygenators are used, as well as arterial line filters and smaller circuits coated with heparin. These circuits also attempt to maintain the functioning of platelets, preventing the formation of procoagulants, fibrinolysis, reducing bleeding and the need for transfusion. Proper control of temperature is important (avoiding cerebral hyperthermia), metabolic control and correctly maintaining the acid-base status so as not to increase the possibility of

Cerebral hypoperfusion may reduce purging of microemboli, thereby encouraging neighbouring infarcts. This is why hemodynamic stability should be maintained throughout the surgery. Although autoregulation of cerebral blood flow during cardiopulmonary bypass occurs within a wide range of pressures, hypertensive and diabetic patients may require higher average pressures to maintain perfusion (90 mm Hg). Therefore, although the optimal level is not firmly established, one attempts to apply more pressure than usual to

Non-CPB surgery does not remove medical complications since the inflammatory response is also triggered, though to a lesser degree. This is associated with a relative reduction in the

It is important to try to avoid haematomas on the central or peripheral vascular accesses and pressure zones in order to decrease potential injury to the peripheral nervous system. **Post-operative prevention:** metabolic control should be continued as regards blood glucose and adequate oxygenation, and anticoagulation and antiagregation should be started immediately. Arrhythmias should be avoided as much as possible, especially atrial

One should continue avoiding zones of compression or of excessive pressure in order to

It is very important at this stage to control all that has been mentioned above since all of this may prolong the time in intensive care units, possibly leading to polyneuropathy in the critical patient with a pattern of axonal damage that would cause long-term consequences similar to those caused by the side effects of a stroke. It is therefore important to get the

**5. Rehabilitation treatment for neurological complications after aortic valve** 

and increasing the patient's participation in and return to daily life.

The **rehabilitative treatment** for NCs arising from aorta surgery ranges from prevention of possible complications to restoring the motor control of walking, improving limb functions

In patients with stroke and severe postoperative NCs, rehabilitation treatment in the **acute** 


neurological effects.

risk of stroke by 50%.

reduce neurological damage in high-risk patients.

fibrillation, usually by using beta blockers.

patient to sit up as soon as possible.

**surgery** 

**phase** is:

techniques.

decrease injury to the peripheral nervous system.


Table 1. Major neurological complications in cardiac surgery
