Society of Cardiovascular Anesthesiologists

Jugular bulb desaturation during coronary artery surgery: a comparison of off-pump and on-pump procedures.

Diephuis JC, Moons KGM, Nierich AN, Bruens M, van Dijk D, Kalkman CJ. Br J Anaesth 2005; 94:715-720.

Reviewer: Mark A. Chaney, MD
University of Chicago
Chicago, IL

Abstract: Conventional coronary artery bypass surgery has been associated with cerebral injury attributed to cardiopulmonary bypass and surgical manipulation of the ascending aorta. Off-pump coronary artery surgery avoids these factors and could prevent cerebral injury. However, moving the heart from its natural position affects the circulation and could compromise cerebral oxygenation and perfusion. These investigators compared episodes of poor global cerebral oxygenation, defined as a jugular bulb saturation less than 50%, between patients randomized to off-pump or conventional on-pump coronary artery surgery. One hundred eighty-seven patients were assigned randomly to off-pump or on-pump coronary artery surgery. Oxygen saturation in the jugular bulb was measured during revascularization of the three main coronary vessels in the off-pump group, and at the start of cardiopulmonary bypass, before rewarming, and after rewarming in the on-pump group. Samples with jugular bulb desaturation (less than 50%) were compared between treatment groups. One hundred seventy-five patients (81 in off-pump group, 94 in on-pump group) had complete jugular oxygen saturation data. Thirty-nine patients in the off-pump group (48%) and 25 patients in the on-pump group (27%) had one or more samples with desaturation during revascularization or cardiopulmonary bypass (p <0.01). These investigators conclude that jugular bulb desaturation occurs more frequently during off-pump coronary artery surgery than during conventional coronary artery surgery.

Comments: The recent resurgence of off-pump cardiac surgery has been driven by the determination to avoid the well-known detrimental physiologic effects of exposure to cardiopulmonary bypass (neurologic dysfunction, pulmonary dysfunction, renal dysfunction, excessive bleeding, etc.) The most clinically important problem associated with cardiopulmonary bypass is neurologic dysfunction. Stroke (likely from macroemboli) occurs in approximately 5% of patients, and diffuse neurological deficits (likely from microemboli) occur with much greater frequency ( 20% - 80%), depending on definition. While brain damage following exposure to cardiopulmonary bypass is multifactorial, macroembolism, microembolism, and/or hypoperfusion remain the most likely culprits. Off-pump cardiac surgery involves much less surgical manipulation of the aorta (less macroemboli?) and avoids cardiopulmonary bypass (less microemboli?), thus one would think neurologic complications would be profoundly decreased by use of the technique. Unfortunately, and somewhat surprisingly, clinical investigations have been equivocal. It seems that risk from macroembolism is likely decreased. However, despite clear evidence from ultrasound studies showing decreased microembolic load with off-pump surgery, well-designed clinical studies (prospective, randomized, blinded) have shown no real beneficial effect on diffuse neurologic deficits. Why is the so? These investigators provide a possible explanation for why off-pump cardiac surgery may not decrease postoperative diffuse neurological deficits. Using jugular bulb oxygen desaturation (less than 50%) as their definition, they have clearly demonstrated that patients undergoing off-pump cardiac surgery experience far more cerebral hypoperfusion than when conventional cardiac surgery with cardiopulmonary bypass is used. This most likely is secondary to the profound dislocation of the heart required for distal anastomoses (and profound hemodynamic changes). Dislocation of the heart can cause profound decreases in stroke volume and mean arterial pressure. It may be that any benefit obtained by decreasing cerebral microembolic load by using the off-pump technique is offset by increased levels of cerebral hypoperfusion. While the relationship between jugular venous desaturation and postoperative neurological deficits remains unclear, the results of this clinical investigation are intriguing. The risk:benefit ratio of off-pump cardiac surgery continues to evolve. At present, the technique (when compared to conventional cardiopulmonary bypass) appears to decrease risk of gross stroke yet does not appear to decrease risk of diffuse neurological deficits.

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