Moderately hypothermic cardiopulmonary bypass and selective cerebral perfusion in ascending aorta and aortic arch surgery. Preliminary experience in twenty-two patients

Central Nervous System Protection in Cardiac Surgery

Neurological dysfunction and stroke following cardiac surgery and thoracic surgery requiring hypothermic circulatory arrest is a well-defined problem. The original studies in CABG patients identified risk factors, such as prior stroke and lower educational level. There is older evidence suggesting that higher perfusion pressures during cardiopulmonary bypass are helpful. Hyperthermia during rewarming on cardiopulmonary bypass and postoperative hyperthermia have been associated with adverse cognitive outcomes. Glucose management intraoperatively remains controversial, but most now advocate for moderate glucose control using insulin, if required. The subset of patients having thoracic aortic surgery requiring periods of aortic discontinuity are particularly problematic. A cerebral protection strategy should be determined, and this may include hypothermic circulatory arrest, selective cerebral perfusion, or retrograde cerebral perfusion. All of these techniques have been associated with good surgical outcomes, but there is little information on cognitive outcomes of thoracic aortic surgery.

Regional cerebral saturation monitoring with near-infrared spectroscopy during selective antegrade cerebral perfusion: Diagnostic performance and relationship to postoperative stroke

OBJECTIVE

To investigate whether regional cerebral tissue oxygen saturation monitoring during hypothermic selective antegrade cerebral perfusion in surgery involving the aortic arch can predict neurologic sequelae and to evaluate the diagnostic performance of near-infrared spectroscopy monitoring in this setting.

METHODS

Data from 46 consecutive patients were analyzed. Selective antegrade cerebral perfusion was established by perfusion of the right subclavian artery (with or without left carotid artery perfusion) or by separate concomitant perfusion of the innominate and the left carotid arteries. The bilateral regional cerebral tissue oxygen saturation index was monitored by using near-infrared spectroscopy equipment (INVOS 4100). Stroke was the primary clinical end point, along with the indices of diagnostic performance.

RESULTS

Six patients died in the hospital, and 6 patients (13%) experienced a perioperative stroke. In patients with stroke, regional cerebral tissue oxygen saturation values were significantly lower during selective antegrade cerebral perfusion, and regional cerebral tissue oxygen saturation tended to be lower in the affected hemisphere. In receiver operating characteristic curve analysis, the area under the curve for relative regional cerebral tissue oxygen saturation values ranged from 0.72 to 0.87. During selective antegrade cerebral perfusion, regional cerebral tissue oxygen saturation between 76% and 86% of baseline had a sensitivity up to 83% and a specificity up to 94% in identifying individuals with stroke. The associated odds ratio for stroke was 5.6 (95% confidence interval, 0.5-144) to 21 (95% confidence interval, 1.8-566).

CONCLUSIONS

Monitoring of regional cerebral tissue oxygen saturation by using near-infrared spectroscopy during selective antegrade cerebral perfusion allows detection of clinically important cerebral desaturation. It can help predict perioperative neurologic sequelae. Its performance as a diagnostic instrument is satisfying and supports its use as a noninvasive trend monitor of cerebral saturation.

Neurological Complications of Aortic Surgery

Surgery of the aortic arch involves an inherently high risk of neurological complications. A number of factors have been identified which may predispose the patient to brain injury, and various techniques employed in an attempt to counteract these are outlined. In particular the vulnerability of the brain to ischemia has led to the development of three adjunctive cerebral protective techniques, hypothermic circulatory arrest, retrograde cerebral perfusion and selective antegrade cerebral perfusion, all based upon brain cooling and metabolic inhibition. The relative merits and disadvantages of these techniques are therefore discussed. Finally, pharmacologic adjuncts and potential future developments in aortic arch surgery are discussed.

Simulation study of a selective cerebral perfusion system with a single centrifugal pump

We previously successfully developed a simple nonroller extracorporeal circulation system (NRECC). In aortic arch surgery, more than two pumps are generally used for systemic perfusion and selective cerebral perfusion (SCP); we developed a new pressure-dependent perfusion system for SCP based on our NRECC and operated by a single centrifugal pump. The cerebral perfusion line was branched from the main perfusion line, and one 15 French and two 12 French cannulae were used for SCP. The perfusion pressure was regulated with a tube occluder. Afterload was changed from 30 to 80 mm Hg, the pressure of the SCP line was increased from 80 to 200 mm Hg, and flow volume was measured. When the afterload was set at 50 mm Hg, according to the increase of perfusion from 80 to 200 mm Hg, the flow volume of the 15 French cannula increased from 280 to 950 ml/min. Under the same conditions, flow volume of the 12 French cannula increased from 160 to 560 ml/min. Sufficient flow volume of the SCP lines was obtained when the SCP line pressure was over 80 mm Hg. As a result of the increased perfusion pressure, the flow volume showed a direct increase. These findings suggest that aortic arch surgery is possible using this SCP system.

First-stage palliation for hypoplastic left heart syndrome in the twenty-first century

Improved understanding of the postoperative physiology and experience with the surgical techniques and perioperative care of patients with hypoplastic left heart syndrome have resulted in improved outcomes. Over the past few years, numerous modifications to the intraoperative and postoperative management of these patients have been described. It is likely that in combination, these modifications and better understanding of the unique physiology after the Norwood procedure are responsible for decreasing early mortality. This review describes and discusses the current surgical and medical management of patients undergoing first-stage palliation for hypoplastic left heart syndrome and its variants.

Gastric intramucosal pH during lower body circulatory arrest under open distal anastomosis with selective cerebral perfusion in aortic arch repair

Selective cerebral perfusion (SCP) and open distal anastomosis (OD) with hypothermia has been used as a popular means for circulatory assistance in aortic arch surgery. Although SCP has become accepted for brain protection, the influence of OD accompanying circulatory arrest on lower body ischemia is not known. We studied gastric tonometry (gastric intramucosal pH [pHi]) to estimate splanchnic ischemia during OD, and its relationship to postoperative organ function. In five patients (pts) (range, 65-78 years; mean, 71 years; group OD) who underwent arch replacement using SCP and OD with moderate hypothermia (25 degrees C) during the period from March to August of 1999, pHi was measured precardiopulmonary bypass (pre-CPB), 30 min of CPB (CPB30), 10 min after OD (OD10), at end of CPB, and post-CPB. Eight pts (range, 52-78 years; mean; 66 years) who underwent standard CPB (33 degrees C) during the same period (coronary artery bypass surgery in six and valve surgery in two) served as controls (group C). In group OD, pHi was significantly decreased at OD10 (7.35 +/- 0.03 at CPB30 vs. 7.23 +/- 0.07 at OD10, p < 0.05) but recovered by the end of CPB (7.32 +/- 0.02). Creatinine clearance on the first postoperative day (1POD) was significantly (p < 0.05) lower in group OD (82 +/- 40 ml/min) than in group C (126 +/- 25 ml/min), although there was no significant difference in preoperative values between the two groups. The pHi at OD10 did not correlate with the duration of OD (range, 30-47 min; mean, 38 min), whereas pHi at OD10 significantly correlated with BUN (r = -0.973, p = 0.0054), Cr(r = -0.977, p = 0.0043), and CCr (r = 0.908, p = 0.0328) on 1POD. One patient in group OD developed paraplegia and renal failure postoperatively. His pHi at OD10 was severely decreased to 7.11. These results suggest that intraoperative monitoring of pHi may be useful for the evaluation of visceral organ ischemia during OD in arch replacement and may contribute to improved technique for circulatory assistance in aortic surgery.

Surgical techniques. Ascending aorta

Aneurysm and dissection are the most common diseases affecting the ascending aorta. Graft replacement of the ascending aorta is a straightforward cardiovascular procedure with excellent early and late results. When aneurysm or dissection extends into the aortic sinuses or arch, management becomes more complex and may entail replacement of the aortic root, aortic valve, or a portion of the aortic arch using hypothermic circulatory arrest. The optimal root prosthesis depends on several patient- and procedure-related variables. Valve-sparing procedures confer many long-term advantages and should be considered in all cases where the aortic valve leaflets are normal. The Ross procedure, although ideally suited for isolated aortic valve disease in young patients, may be applicable to some patients with combined aortic valve and ascending aortic disease, unless there is evidence of a systemic connective tissue disorder.