**5. Complications of DHCA**

Disadvantages of DHCA include increased cardiopulmonary bypass (CPB) time, edema formation, coagulopathy, and alteration in many organ functions including the kidney, the brain, vascular smooth muscles, intestinal mucosa, alveolar epithelium, the liver, and the pancreas. Based on reports from 8 major cardiac surgery centers in the United States, Europe, and Japan, the risk of permanent neurologic injury after aortic arch surgery using DHCA ranged from 3% to 12%, renal dysfunction from 5% to 14%, pulmonary insufficiency from 5% to 39%, and left ventricular failure or low-cardiac-output syndrome from 7% to 34%. Alternatives to the use of DHCA during aortic arch replacement are the use of normothermic CPB or mild-to-moderate degrees of hypothermia. These alternatives obviously require the use of a perfusion system for the brain, separate from the rest of the body, which might increase the risk of cerebral emobilization.

#### **5.1 Neurologic injury**

Neurologic injury is the most troublesome adverse effect of DHCA and CPB, presenting either as transient neurologic deficit (5.9%-28.1%) or irreversible neurologic injury (1.8%- 13.6%). Early postoperative mortality markedly is increased (18.2%) in patients with neurologic injury, and long-term cognitive disability is common among survivors. Neurologic deficit after DHCA encompasses a wide scale of disorders ranging from deep coma to subtle, hardly perceptible alterations in cognitive functions or behavior. In the immediate postoperative period, the return of sophisticated neurologic functions is often obscured by the administration of sedative and analgesic agents. Neurologic injury presents at that time mostly as a focal or diffuse deficit. A focal deficit is due to interruption of blood in a terminal vascular territory, usually following embolism of material or gas bubbles. The

blood remains the same. During hypothermia, if a blood sample is taken and warmed to 37°C in the blood gas analyzer, the CO2 initially dissolved will now contribute to the partial pressure of CO2 (PCO2) and the PCO2 will be within the normal normothermic range. If, on the other hand, the value is estimated at the patient's actual temperature, the PCO2 will be reduced despite similar arterial CO2 content. In addition to its effect on gas solubility, hypothermia decreases the metabolic rate and CO2 production. Maintaining the PCO2 within the normal range in rewarmed 37°C blood is called "alpha-stat." If the PCO2 is corrected to the patient's actual temperature and that value is kept within the normal range, the

A number of biochemical and cellular structural changes take place as the duration of circulatory arrest lengthens. After 15 minutes of ischemia at 18°C, the recovery of oxygen consumption is impaired, and after 20 minutes, cerebral lactate is detected in the effluent blood. The safe duration of circulatory arrest at 15°C was predicted to be about 29 minutes and at 10°C about 40 minutes. If ischemic tolerance is considered 5 minutes at normothermia, the calculated safe period of circulatory arrest at 18°C would be 15 minutes. Clinical studies have shown a persistent loss of cognitive function (lasting more than 6 weeks) and deterioration in postoperative cognitive scoring/testing in patients who

Disadvantages of DHCA include increased cardiopulmonary bypass (CPB) time, edema formation, coagulopathy, and alteration in many organ functions including the kidney, the brain, vascular smooth muscles, intestinal mucosa, alveolar epithelium, the liver, and the pancreas. Based on reports from 8 major cardiac surgery centers in the United States, Europe, and Japan, the risk of permanent neurologic injury after aortic arch surgery using DHCA ranged from 3% to 12%, renal dysfunction from 5% to 14%, pulmonary insufficiency from 5% to 39%, and left ventricular failure or low-cardiac-output syndrome from 7% to 34%. Alternatives to the use of DHCA during aortic arch replacement are the use of normothermic CPB or mild-to-moderate degrees of hypothermia. These alternatives obviously require the use of a perfusion system for the brain, separate from the rest of the

Neurologic injury is the most troublesome adverse effect of DHCA and CPB, presenting either as transient neurologic deficit (5.9%-28.1%) or irreversible neurologic injury (1.8%- 13.6%). Early postoperative mortality markedly is increased (18.2%) in patients with neurologic injury, and long-term cognitive disability is common among survivors. Neurologic deficit after DHCA encompasses a wide scale of disorders ranging from deep coma to subtle, hardly perceptible alterations in cognitive functions or behavior. In the immediate postoperative period, the return of sophisticated neurologic functions is often obscured by the administration of sedative and analgesic agents. Neurologic injury presents at that time mostly as a focal or diffuse deficit. A focal deficit is due to interruption of blood in a terminal vascular territory, usually following embolism of material or gas bubbles. The

underwent aortic arch surgery by using DHCA for more than 25 minutes at 10°C.

body, which might increase the risk of cerebral emobilization.

management is called "pH-stat."

**5. Complications of DHCA** 

**5.1 Neurologic injury** 

**4. Duration of DHCA** 

clinical expression is typically motor-sensory deficit, aphasia, or cortical blindness (Kunihara et al, 2005; Lipton, 1999). Computed tomography and magnetic resonance imaging are usually able to detect a sharply demarcated area of necrosis in the brain.

A focal deficit is usually an embolic phenomenon, whereas a prolonged poor perfusion of the brain may produce necrosis in watershed zones. Age, atherosclerosis, and manipulation of the aorta are risk factors for both. Global cerebral ischemia leads to diffuse neurologic deficit, which may be benign and reversible or more debilitating (seizures, Parkinsonism, and coma). Risk factors include increased duration of circulatory arrest and CPB, diabetes mellitus, and hypertension. Transient neurologic dysfunction appears to be a marker of long-term cerebral injury. Deficits of memory and fine-motor function may persist after hospital discharge. Reductions in CMRO2 and the duration of DHCA reduce the risk of neurologic injury. The length of time on CPB might be a better predictor of postoperative death and stroke than the duration of DHCA time (Hagl et al, 2003).

Aortic procedures requiring hypothermic circulatory arrest have been specifically correlated with increased risk of both stroke and mortality in all patients. This may be accentuated in the elderly, who may have less tolerance for neurological insult. Many physicians think patients >75 years old are too frail and lack the reserve to survive a major cardiothoracic surgery. In particular, there remains some hesitancy in performing procedures with a higher risk of stroke in patients with a higher susceptibility for adverse neurological sequelae. This perceived combination of risk and susceptibility may be a barrier to care for elderly patients requiring hypothermic circulatory arrest to address their aortic pathology. According to Coselli et al. (2008), in a study accessing the safety and efficacy of HCA, there are various major complications associated with HCA. These included death (interoperative, during hospital stay, and within 30 days), stroke, paraplegia, paraparesis, uncontrolled bleeding which required reoperation, renal failure, cardiac complications, and vocal cord paralysis.
