Shinichi Hatsuoka

Utility and limitations of near-infrared spectroscopy during cardiopulmonary bypass in a piglet model

Near-infrared spectroscopy assessment of cytochrome oxygenation could be a valuable technique to monitor cerebral intraneuronal oxygen delivery during cardiopulmonary bypass. However, the validity of the cytochrome signal has been questioned as it could easily be overwhelmed by the Hb signal. Five- to six-week-old control piglets (n = 5) underwent cardiopulmonary bypass at 37°C. Study animals (n = 10) received 100 mg/kg of sodium cyanide to uncouple cytochrome from Hb. Hematocrit was then decreased in steps of 5% from 35 to 5% with crystalloid hemodilution. In study piglets, the initiation of cardiopulmonary bypass was associated with oxygenated Hb increasing from 0 to 62.9 ± 25.6 μM times the differential path-length factor, and oxidized cytochrome a,a3 increasing to 1.9 ± 1.8 μM times the differential path-length factor. Cyanide caused oxygenated Hb to increase further to 132.3 ± 48.9 μM times the differential path-length factor, and oxidized cytochrome c decreased to −7.0 ± 2.6 μM times the differential path-length factor as anticipated, confirming uncoupling of electron transport. However, hemodilution subsequently resulted in linear decreases in oxidized cytochrome a,a3 (F = 8.57, p < 0.001) suggesting important cross-talk between the Hb and cytochrome signals as cytochrome is only intracellular. In control piglets, tissue oxygenation index showed a positive correlation with pump flow (r = 0.986, p = 0.013). The cytochrome signal as presently measured by near-infrared spectroscopy is highly dependent on hematocrit.

New strategy for treatment of MRSA mediastinitis: one-stage procedure for omental transposition and closed irrigation

Mediastinitis due to methicillin-resistant Staphylococcus aureus is a devastating potential complication of cardiac surgery. We treated 4 patients with this condition using a new technique. First we performed an early radical removal of infected tissue and omental transposition with direct primary closure of the sternum and closed continuous irrigation with saline/vancomycin hydrochloride; that was followed by an administration of intravenous antibiotics. We obtained good clinical results, which are reported herein along with the clinical courses.

Noninvasive evaluation of internal thoracic artery and left anterior descending coronary artery anastomotic sites using transthoracic Doppler echocardiography: comparison with coronary arteriography.

OBJECTIVES This study was designed to evaluate anastomotic sites located between the internal thoracic artery and left anterior descending coronary artery using transthoracic Doppler echocardiography, and then to clarify the accuracy of those results by comparison with coronary arteriographic findings. METHODS We examined 35 consecutive patients who had undergone bypass surgery. The echocardiographic examinations were performed within approximately 1 week of follow-up coronary arteriography, which occurred at 4.3 +/- 2.2 months after bypass surgery. We measured the diameter using intraluminal flow signals, and we also measured flow velocity. RESULTS Adequate spectral Doppler recordings of coronary flow in the anastomosis were obtained in 31 (89%) of the 35 study patients. In the normal anastomosis group (n = 25), the diameter and the peak blood flow velocity of the internal thoracic artery and left anterior descending coronary artery were 1.5 +/- 0.3 mm and 2.0 +/- 0.4 mm, and 58 +/- 25 cm/s and 47 +/- 20 cm/s, respectively. Stringed internal thoracic artery was found in 4 patients; the echocardiographic findings revealed a greater amount of information regarding the physiologic state in the area of anastomosis compared with angiographic findings. In a stenotic anastomosis found in 2 patients, the blood flow velocity findings at the anastomotic sites (83 +/- 228 cm/s) were higher than those in normal anastomotic patients (59 +/- 28 cm/s). CONCLUSIONS Transthoracic Doppler echocardiography enabled an effective evaluation of anastomotic sites between the internal thoracic artery and left anterior descending coronary artery in over 80% of our patients. This totally noninvasive method is thought to be reliable and able to provide a greater amount of information, compared with coronary arteriography, regarding the physiologic state of an anastomosis, such as a competitive relationship.

Effects of cyanosis and hypothermic circulatory arrest on lung function in neonatal lambs

BACKGROUND Lung function is often impaired after cardiac surgery and cardiopulmonary bypass (CPB), particularly in chronically cyanotic patients. This study aimed to evaluate lung function in a surgically created chronic cyanotic neonatal lamb model after CPB and deep hypothermic circulatory arrest (DHCA) and to assess the role of nitric oxide (NO) in the pathogenesis of increased pulmonary vascular resistance. METHODS A chronic cyanosis model was surgically created in 7 lambs (4.7+/-0.8 days old) by anastomosing the pulmonary artery (PA) to the left atrium (LA). Another 7 lambs underwent a sham operation (control). One week later, the animals underwent shunt takedown and CPB with 90 minutes of DHCA at 18 degrees C. Cardiac index (CI), pulmonary vascular resistance index (PVRI), lung dynamic compliance (Cdyn), alveolar-arterial oxygen difference (AaDO2), left atrial plasma nitrate/nitrite (NO metabolites) levels, and pulmonary cGMP production (concentration difference between LA and PA) were measured before CPB and at 1 and 2 hours after reperfusion. RESULTS The cyanosis model consistently produced significantly lower arterial oxygen tension (34.8+/-2.3 vs 93.1+/-8.8 torr in control, p < 0.001) and Qp/Qs (0.6+/-0.1 vs 1.0+/-0.0 in control, p < 0.001) than controls. Postoperative PVRI was significantly lower in the cyanosis group than in controls, although CPB with DHCA significantly elevated PVR in both cyanotic and control animals. There were no significant differences in AaDO2 and Cdyn after CPB between groups. The level of NO metabolites did not change before or after CPB in either cyanotic or acyanotic animals. NO metabolite levels tended to be higher in the cyanotic animals (p = 0.08). There was no significant difference in pulmonary cGMP production between both groups. CONCLUSIONS These findings suggest that CPB with DHCA, per se, does not affect NO production in cyanotic or acyanotic neonatal lambs but causes increased PVR in both groups. Chronic cyanosis does not result in reduced pulmonary function after CPB with DHCA, and is associated with lower PVR. The mechanism may involve an increased NO production in cyanotic animals.

Effect of L-arginine or nitroglycerine during deep hypothermic circulatory arrest in neonatal lambs.

BACKGROUND The role of nitric oxide (NO) in ischemia-reperfusion injury remains controversial. This study evaluated the effects of L-arginine (NO precursor) or nitroglycerine (NO donor) on cardiac and lung function after deep hypothermic circulatory arrest in neonatal lambs. METHOD Three groups of anesthetized lambs underwent cardiopulmonary bypass, deep hypothermic circulatory arrest (120 minutes at 18 degrees C), and rewarming (40 minutes). During reperfusion, L-arginine (5 mg/kg per minute), nitroglycerine (2 microg/kg per minute), or saline (control group) was infused for 100 minutes. All animals were separated from cardiopulmonary bypass and observed for 3 additional hours. Preload recruitable stroke work, cardiac index, pulmonary vascular resistance, alveolar-arterial oxygen difference, and lung compliance plasma nitrate/nitrite levels (NO metabolites) were measured before and after cardiopulmonary bypass. Malondialdehyde in heart tissue and lung tissue was measured 3 hours after cardiopulmonary bypass. RESULTS Recovery of preload recruitable stroke work and cardiac index were significantly higher in the L-arginine and nitroglycerine groups than in the control group (p < 0.05). Pulmonary vascular resistance was significantly lower in the L-arginine and nitroglycerine groups than in the control group (p < 0.05). Levels of NO metabolites and issue malondialdehyde did not differ among groups. CONCLUSIONS L-arginine and nitroglycerine improved recovery of left ventricular function and reduced pulmonary vascular resistance after deep hypothermic circulatory arrest. The mechanism of beneficial action could involve increased NO levels, but we did not find higher levels of NO metabolites compared with controls. Tissue malondialdehyde levels were not affected by L-arginine or nitroglycerine. These results show that, at these dosage levels, provision of substrate for NO production or provision of an NO donor were beneficial to the recovery of myocardial and pulmonary vascular function.

Development of severe string sign in internal thoracic arterial graft during first month

In the present case, development of the string sign in an internal thoracic arterial graft was observed using transthoracic Doppler echocardiography. Following surgery, the diameter of the internal thoracic graft decreased; however, the diameter of the left anterior descending coronary artery did not change from 1.9 mm. Further, the flow velocity in the internal thoracic artery during the systolic phase became greater than that in the early phase and then decreased on postoperative day 19, and it was not detected on postoperative day 31. Coronary arteriography performed on postoperative day 31 revealed a severely stringed internal thoracic artery.