The Hemodynamic Effects of Methylene Blue When Administered at the Onset of Cardiopulmonary Bypass

Abstract

Hypotension occurs during cardiopulmonary bypass (CPB), in part because of induction of the inflammatory response, for which nitric oxide and guanylate cyclase play a central role. In this study we examined the hemodynamic effects of methylene blue (MB), an inhibitor of guanylate cyclase, administered during cardiopulmonary bypass (CPB) to patients taking angiotensin-converting enzyme inhibitors. Thirty patients undergoing cardiac surgery were randomized to receive either MB (3 mg/kg) or saline (S) after institution of CPB and cardioplegic arrest. CPB was managed similarly for all study patients. Hemodynamic data were assessed before, during, and after CPB. The use of vasopressors was recorded. All study patients experienced a similar reduction in mean arterial blood pressure (MAP) and systemic vascular resistance (SVR) with the onset of CPB and cardioplegic arrest. MB increased MAP and SVR and this effect lasted for 40 minutes. The saline group demonstrated a persistently reduced MAP and SVR throughout CPB. The saline group received phenylephrine more frequently during CPB, and more norepinephrine after CPB to maintain a desirable MAP. The MB group recorded significantly lower serum lactate levels despite equal or greater MAP and SVR. In conclusion, administration of MB after institution of CPB for patients taking angiotensin-converting enzyme inhibitors increased MAP and SVR and reduced the need for vasopressors. Furthermore, serum lactate levels were lower in MB patients, suggesting more favorable tissue perfusion.

Plasma methemoglobin as a potential biomarker of anemic stress in humans

“…3 Methylene blue is also known for its NO binding capacity and treatment of vasoplegia associated with cardiopulmonary bypass. 40,41 Taken together, these data suggest that methylene blue is a potent inhibitor of NO production/action and is also associated with a profound vasoconstricting effect. This may maintain blood pressure in the setting of profound vasoplegia associated with cardiac surgery.…”

Methylene blue for vasoplegic syndrome treatment in heart surgery: fifteen years of questions, answers, doubts and certainties

“…Observing the other 55 studies we can find: 1) one study (1.67%) based on evidences through metanalysis of literature [13]; 2) seven review articles (11.67%) [4,14,23]. The other bibliographical citations in number of 44 (73.33%) are distributed as case reports (great majority) [24][25][26][27][28][29][30][31][32][33][34][35][36], letters [37][38][39][40][41][42][43][44], technical aspects of the MB use [45][46][47][48][49][50] and other studies involving risk [51,52], the VS incidence in the "off pump" CABG and the possibility of MB use in anaphylaxis and anaphylactic shock [53], also a proposal of the author of this text ( Figure 4) [54][55][56][57][58]. The presented numbers, surely, are not totally compatible with the total of publications, but it is possible to assume that this imprecision does not affect the general vision of the problem.…”

Reassessing the risk of hemodilutional anemia: Some new pieces to an old puzzle

“…98 In a recent clinical trial, methylene blue was administered prior to CPB to determine if it could improve hemodynamics and tissue perfusion. 99 Although the initial results provided evidence of improved tissue perfusion with methylene blue, these results must be interpreted with caution, since previous attempts to reduce NO bioavailability have led to increased mortality. 92,96 Methylene blue acts by restricting NO bioavailability by three mechanisms: 1) inhibition of NOS; 2) direct scavenging of NO; and 3) inhibiting the action of downstream soluble guanylate cyclase ( Figure 6).…”