Effects of  Hot shot  on recovery after hypothermic ischemia in neonatal lamb heart.
BACKGROUND
Terminal warm blood cardioplegia, "Hot shot", is the method for providing an energy replenishment and/or early recovery of aerobic metabolism without electromechanical activity at initial reperfusion. The mechanism of beneficial effects of this  Hot Shot  is multifactorial. This study was designed to assess the effects of terminal warm blood cardioplegia by comparing with oxygenated terminal warm crystalloid cardioplegia.


METHODS
In Group HS-B, n=8 (oxygenated blood; 37 degrees C, Ht: 20%, K+ 20 mEq/l, pH 7.237, PO2 219 mmHg) and in Group HS-C, n=8 (bloodless oxygenated (5% CO2+95%O2) crystalloid, 37 degrees C, K+ 20 mEq/l, pH 7.435, PO2 624 mmHg), terminal warm cardioplegia (20 ml/kg for 5 minutes) was studied in the isolated blood perfused neonatal lamb heart following 2 hr of cardioplegic ischemia. Another eight hearts served as control without any kind of terminal cardioplegia. After 60 min of reperfusion, LV function was measured. Coronary blood flow (CBF), oxygen content, and oxygen consumption (MVO2) were measured and the oxygen extraction ratio was calculated in Group HS-B and HS-C during terminal cardioplegia and/or reperfusion. Results are given as % recovery of preischemic values.


RESULTS
HS-B as well as HS-C groups showed better functional recovery in maximum developed pressure (DP: 78.0+/-8.3 in HS-B vs 65.2+/-9.2%; p=0.018), maximum dp/dt (67.3+/-6.2 in HS-B, 65.3+/-7.4 in HS-C vs 55.8+/-5.0%; p=0.003, p=0.02), DP V10 (87.1+/-8.5 in HS-B vs 67.2+/-9.9%; p=0.0001), and peak dp/dt V10 (76.4+/-7.6 in HS-B, 69.8+/-8.1 in HS-C vs 58.6+/-6.9 %; p=0.0001) than the control group. Between the HS-B and HS-C groups, HS-B showed better functional recovery in terms of DP V10 (p=0.01). Oxygen delivery of terminal cardioplegia was almost four times higher in HS-B group (90.4+/-17.7 vs 18.7+/-1.1 mcl/ml), contrarily, HS-C group showed four times higher oxygen extraction ratio compared to HS-B group (0.78+/-0.06 vs 0.18+/-0.11), thus oxygen consumption during hot shot was maintained at the same level in both groups. CBF in the control group was lower than that in the other groups at 60 min of reperfusion.


CONCLUSIONS
Reperfusion with both terminal warm cardioplegia including blood and oxygenated crystalloid cardioplegia resulted in better recovery of function and higher levels of CBF with slightly better function in terminal warm blood cardioplegia.
Nomura
F
F
Department of Cardiovascular Surgery, Children s Hospital, Boston, USA.
Forbess
J M
JM
Mayer
E J
EJ
D000818:Animals; D000831:Animals, Newborn; D001769:Blood; D002314:Cardioplegic Solutions; D003326:Coronary Circulation; D003331:Coronary Vessels / Q000503:physiopathology; D004730:Endothelium, Vascular / Q000503:physiopathology; D006324:Heart Arrest, Induced / Q000379:methods*; D006358:Hot Temperature; D007036:Hypothermia, Induced; D019344:Lactic Acid / Q000097:blood; D015425:Myocardial Reperfusion; D015428:Myocardial Reperfusion Injury / Q000503:physiopathology / Q000517:prevention & control*; D009206:Myocardium / Q000378:metabolism; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption; D017680:Potassium Compounds; D012756:Sheep; D014655:Vascular Resistance; D014664:Vasodilation; D016277:Ventricular Function, Left
D002314:Cardioplegic Solutions; D017680:Potassium Compounds; C018369:potassium cardioplegic solution; D019344:Lactic Acid; D010100:Oxygen