title: Warm nondepolarizing adenosine and lidocaine cardioplegia: continuous versus intermittent delivery.
abstract: OBJECTIVE
  Continuous infusion of warm to normothermic cardioplegia may limit the surgeon's visual field, increase coronary vascular resistance, and lead to potassium-exacerbated ischemia-reperfusion damage. Our aim was to examine the versatility of a new normokalemic, nondepolarizing adenosine-lidocaine cardioplegia during continuous or intermittent infusion at 33 degrees C and compare it with lidocaine cardioplegia.
  
  
  METHODS
  Isolated, perfused rat hearts (n = 6 each group) were arrested at 33 degrees C for 40 or 60 minutes with 200 microm of adenosine and 500 microm of lidocaine in Krebs-Henseleit buffer (10 mmol/L glucose, pH 7.6-7.7 at 37 degrees C) or 500 microm of lidocaine in Krebs-Henseleit buffer for 60 minutes delivered at 60 mm Hg.
  
  
  RESULTS
  Times to arrest were 7 to 10 seconds for the adenosine-lidocaine groups and 102 seconds for the lidocaine group (P < .05). Total cardioplegia volumes for intermittent (2 minutes every 18 minutes) and continuous deliveries were 122 to 159 mL and 699 to 922 mL for the 40- and 60-minute adenosine-lidocaine arrest protocols, respectively, and 136 mL for the 60-minute intermittent lidocaine group. In the last 2 minutes of the 40- and 60-minute arrest protocols, the coronary vascular resistance was not significantly different for the hearts arrested with adenosine and lidocaine (0.27-0.32 megadyne/sec/cm(-5)). Significantly higher coronary vascular resistance was found in the lidocaine cardioplegia group (0.38 megadyne/sec/cm(-5)). No significant differences were found between the continuous or intermittent adenosine-lidocaine delivery protocols. Hearts arrested with adenosine and lidocaine recovered 88% to 89% of aortic flow and 109% of coronary flow at 60 minutes of reperfusion after 40-minute arrest, and 77% to 86% of aortic flow and 98% to 109% of coronary flow at 60 minutes of reperfusion after 60-minute arrest. Lidocaine cardioplegia led to significantly lower aortic and coronary flows after 60-minute arrest compared with the intermittent adenosine-lidocaine group.
  
  
  CONCLUSIONS
  We conclude that adenosine-lidocaine cardioplegia can be delivered intermittently or continuously with similar functional recoveries after a 40- or 60-minute arrest at 33 degrees C. Hearts receiving lidocaine cardioplegia took a significantly longer time to arrest, showed higher coronary vascular resistance, and achieved lower functional recovery than the 60-minute adenosine-lidocaine cardioplegia groups. Intermittent or continuous delivery of adenosine-lidocaine cardioplegia may offer an alternative to current surgical hyperkalemic cardioplegia at warm to normothermic temperatures.
authors.affiliation: Department of Physiology and Pharmacology, Molecular Science Building, James Cook University, Townsville, Queensland, Australia.
authors.forename: Kathryn L
authors.initials: KL
authors.lastname: Sloots
authors.forename: Jakob
authors.initials: J
authors.lastname: Vinten-Johansen
authors.forename: Geoffrey P
authors.initials: GP
authors.lastname: Dobson
mesh_terms: D000241:Adenosine / Q000008:administration & dosage*; D000818:Animals; D001011:Aorta / Q000502:physiology; D001783:Blood Flow Velocity; D001794:Blood Pressure; D002314:Cardioplegic Solutions / Q000008:administration & dosage*; D003326:Coronary Circulation; D006324:Heart Arrest, Induced / Q000379:methods*; D006339:Heart Rate; D066298:In Vitro Techniques; D008012:Lidocaine / Q000008:administration & dosage*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D013696:Temperature; D014655:Vascular Resistance
chemical_list: D002314:Cardioplegic Solutions; D008012:Lidocaine; D000241:Adenosine