Shinji Kawahito

Blood trauma induced by clinically accepted oxygenators.

Hemolysis remains one of the most serious problems during cardiopulmonary bypass (CPB), extracorporeal membrane oxygenation (ECMO), and percutaneous cardiopulmonary support (PCPS). However, the hemolytic characteristics associated with oxygenators are not well defined. A specialized hemolysis test protocol for oxygenators was developed. A comparative study was performed following this protocol to determine the hemolytic characteristics of the clinically available oxygenators during CPB; pressure drop measurements in the blood chamber were also performed. Four oxygenators (Medtronic Affinity, Cobe Optima, Terumo Capiox SX25, and Bard Quantum) were evaluated. Fresh blood from healthy Dexter calves anticoagulated with citrate phosphate dextrose adenine solution was used. The blood flow was fixed at 5 L/min, similar to that used in CPB. The Normalized Index of Hemolysis for Oxygenators (NIHO) has been modified according to the American Society of Testing and Materials (ASTM) standards. The NIH value, which was obtained from the circuit without an oxygenator, was subtracted from the primary NIH value, obtained from the circuit with an oxygenator to eliminate the effects of a centrifugal pump or other artifacts. The NIHO value was the lowest in the Affinity (0.0116 ± 0.0017) and increased from Affinity < Optima (0.0270 ± 0.0038) < Capiox (0.0335 ± 0.0028) < Quantum (0.0416 ± 0.0015 g/100 L). The Optima and Capiox did not demonstrate a significant difference. In addition, this NIHO value has a close relationship to the pressure drop. In conclusion, this new evaluation method is suitable to compare the biocompatibility performance of different types of clinically available oxygenators for CPB usage.

Argon gas embolism in the application of laparoscopic microwave coagulation therapy

BACKGROUND A major concern in the use of the argon beam coagulator system is the potential risk of argon gas embolism. METHODS Seven cases with argon gas embolism in the English literature were reviewed along with the current case. The latter case was a 77-year-old female having laparoscopic hepatectomy after application of the microwave coagulation system on the cutting planes. RESULTS Immediately following shots of an argon beam to control local bleeding at the needle hole in the liver caused by microwave coagulation, the end-tidal carbon disappeared, followed by cardiovascular collapse. After 18 min of cardiovascular resuscitation, the tumors were resected under laparotomy. CONCLUSIONS After reviewing the cases, pneumoperitoneum (57.1%), hepatic needle punctures (42.8%) and direct application of the argon beam to the liver (28.6%) can be considered as risky processes in such events. Caution is necessary in the use of an argon beam in liver surgery to avoid life-threatening gas embolism.

Recurrent laryngeal nerve palsy after cardiovascular surgery: Relationship to the placement of a transesophageal echocardiographic probe☆

OBJECTIVE To examine the relationship between the incidence of recurrent laryngeal nerve palsy after cardiovascular surgery and the placement of a transesophageal echocardiographic probe. DESIGN A prospective clinical study. SETTING A single-institutional study in a university hospital. PARTICIPANTS One hundred sixteen patients undergoing cardiovascular surgery. INTERVENTIONS All patients were assigned into one of two groups: 64 patients in whom transesophageal echocardiography (TEE) was performed and 52 patients in whom TEE was not performed during surgery. The incidence of recurrent laryngeal nerve palsy was examined and compared between the two groups. MEASUREMENTS AND MAIN RESULTS Five of 64 patients (7.8%) in whom TEE was monitored and 3 of 52 patients (5.8%) in whom TEE was not monitored were diagnosed with recurrent laryngeal nerve palsy postoperatively. There was no statistically significant difference between the incidence of recurrent laryngeal nerve palsy in patients with intraoperative TEE monitoring, and patients without it. The durations of surgery, anesthesia, and cardiopulmonary bypass were significantly longer in patients with nerve palsy than those without it. CONCLUSION These results suggest that placement of the transesophageal echocardiographic probe is not responsible for postoperative recurrent laryngeal nerve palsy. It seems likely that surgical manipulation itself and the durations of surgery, cardiopulmonary bypass, and tracheal intubation are related to the incidence of laryngeal nerve palsy.

Isoflurane activates sarcolemmal adenosine triphosphate-sensitive potassium channels in vascular smooth muscle cells: a role for protein kinase A.

Background:Recent evidence indicates that vascular adenosine triphosphate-sensitive potassium (KATP) channels in vascular smooth muscle cells are critical in the regulation of vascular tonus under both physiologic and pathophysiologic conditions. Studies of the interaction of volatile anesthetics with vascular KATP channels have been limited. In the current study, the authors investigated the molecular mechanism of isofluranes action on vascular KATP channels. Methods:Electrophysiologic experiments were performed using cell-attached and inside-out patch clamp techniques to monitor native vascular KATP channels, and recombinant KATP channels comprised of inwardly rectifying potassium channel subunits (Kir6.1) and the sulfonylurea receptor (SUR2B). Isometric tension experiments were performed in rat thoracic aortic rings without endothelium. Results:Application of isoflurane (0.5 mm) to the bath solution during cell-attached recordings induced a significant increase in KATP channel activity, which was greatly reduced by pretreatment with a selective inhibitor of protein kinase A (PKA), Rp-cAMPS (100 &mgr;m). In inside-out patches, isoflurane did not activate KATP channels. Isoflurane significantly activated wild-type recombinant SUR2B/Kir6.1 in cell-attached patches. Isoflurane-induced activation of wild-type channels was diminished in the PKA-insensitive mutant SUR2B-T633A/Kir6.1, SUR2B-S1465A/Kir6.1, and SUR2B/Kir6.1-S385A. In addition, the authors demonstrated that isoflurane-induced PKA activation was associated with isoflurane-induced decreases in isometric tension in the rat aorta. Conclusion:These results indicate that isoflurane activates KATP channels via PKA activation. PKA-dependent vasodilation induced by isoflurane also was observed in isometric tension experiments. Analysis of expressed vascular-type KATP channels suggested that PKA-mediated phosphorylation of both Kir6.1 and SUR2B subunits plays a pivotal role in isoflurane-induced vascular KATP channel activation.

Hemolytic characteristics of oxygenators during clinical extracorporeal membrane oxygenation.

A connection was previously reported between the hemolytic characteristics associated with oxygenators and the pressure drop measurements in the blood chamber under experimental conditions simulating their use in cardiopulmonary bypass. We examined this association during extracorporeal membrane oxygenation (ECMO) conditions. Three oxygenators for ECMO or pediatric cardiopulmonary bypass (Menox EL4000, Dideco Module 4000, and Mera HPO-15H) were evaluated. Fresh blood from healthy Dexter strain calves anticoagulated with citrate phosphate dextrose adenine solution was used. The blood flow was fixed at 1 L/min, similar to that in ECMO. The Normalized Index of Hemolysis for Oxygenators (NIHO) has been modified according to the American Society of Testing and Materials standards, as was previously reported. The NIHO value was the lowest in the Menox (0.0070 ± 0.0009) and increased from Menox to Dideco (0.0113 ± 0.0099) to Mera (0.0164 ± 0.0043); however, there were no significant differences among the oxygenators. This NIHO value has a close correlation to the pressure drop. In conclusion, this evaluation method is also applicable to comparison of the biocompatibility performance of different types of clinically available oxygenators for ECMO.

Preclinical evaluation of a hollow fiber silicone membrane oxygenator for extracorporeal membrane oxygenator application.

A silicone membrane hollow fiber oxygenator applicable for use as an extracorporeal membrane oxygenator (ECMO) has been developed in our laboratory. This silicone hollow fiber displays astonishing mechanical stability, is barely compressible or stretchable, and assembles easily while maintaining good gas permeability. The priming volume is 140 cc with a surface area of 0.8 m2. This study evaluated the gas transfer performances and biocompatibility of the oxygenator under ECMO and CPB conditions. In vitro studies that were performed at a blood flow rate of 2 L/min, and revealed O2 and CO2 gas transfer rates of 82.35 ± 0.56 ml/m2/L/min and 38.72 ± 2.88 ml/m2/L/min, respectively. The commercially available Kolobow (Avecor 1500) oxygenator was used as the control, and had O2 and CO2 gas transfer rates of 53.8 ± 0.5 ml/m2/L/min and 24.7 ± 2.0 ml/m2/L/min. To evaluate blood trauma, Normalized Index of Hemolysis (NIH) was measured according to American Society of Testing and Materials (ASTM) standards. The NIH findings were 0.0112 g/100L at a blood flow of 1 L/min, and 0.0152 g/100L at 5 L/min. Three ex vivo experiments, using a blood flow rate of 1 L/min, were performed with venoarterial bypass, and O2 transfer rate and CO2 transfer rate of the oxygenators were well maintained. This indicates that this preclinical silicone membrane hollow fiber oxygenator has superior efficiency, less blood trauma, and is smaller when compared with the only clinically available Kolobow oxygenator.

Operating point control system for a continuous flow artificial heart: In vitro study

We proposed and developed a practical and effective servo control system for rotary blood pumps. A rotary blood pump for assisting the failing natural heart should be operated only in physiologically acceptable conditions. The operation of a rotary blood pump is based on the rotational speed of the impeller and pressure head. If the pump flow and the pressure head are set within an acceptable range, the driving condition is deemed normal condition, and this control system maintains the preset operating point by applying proportional and detective control (PD control). If the pump flow or pressure head is outside the acceptable range, the driving condition is determined to be abnormal condition, and this system operates the pump in a recovery fashion. If the driving condition is kept under abnormal conditions of sudden decrease of the flow, the condition is termed a suction condition. The controller releases the pump from the suction condition and later returns it to the normal condition. In this study, we evaluated these servo control modes of the centrifugal pump and confirmed whether the performance of this proposed operating point control system was practical.

Anaesthesia for a patient with paraneoplastic limbic encephalitis with ovarian teratoma: relationship to anti‐N‐methyl‐d‐aspartate receptor antibodies

Paraneoplastic limbic encephalitis associated with ovarian teratoma has recently been related to the development of antibodies to specific heteromers of the N‐methyl‐d‐aspartate receptor and exhibits various manifestations including psychiatric symptoms, hypoventilation, seizures and derangement of autonomic nervous system function. Although recovery can sometimes occur spontaneously, early tumour resection with immunotherapy facilitates earlier recovery. Herein, we describe anaesthetic management of a 20‐year‐old woman who developed general convulsions and decreased level of consciousness, whom we suspected of having paraneoplastic limbic encephalitis and was scheduled for left ovarian tumour resection. Anaesthetic management was successful with no complications but the case acts as focus of discussion for the potential interaction of N‐methyl‐d‐aspartate receptors and anaesthetic sensitivity.

Phenylephrine increases pulmonary blood flow in children with tetralogy of Fallot

PurposeAlthough it has been reported that the increase in blood pressure improves arterial oxygen saturation (SaO2) in children with tetralogy of Fallot, no prospective study has demonstrated that an increase in blood pressure induces an increase in pulmonary blood flow in these patients. The purpose of this study was to see whether a phenylephrine-induced increase in systemic blood pressure increased pulmonary blood flow, resulting in improved arterial oxygénation in tetralogy of Fallot.MethodsIn 14 consecutive children with tetralogy of Fallot (2–32 months old), transesophageal pulsed Doppler signals of left upper pulmonary venous flow (PVF) velocity were recorded before and four minutes after 10/μg · kg−1 of phenylephrine iv. Simultaneously, arterial blood gas analysis and hemodynamic measurements were performed. The minute distance (MD) was calculated as the product of the heart rate and the sum of time-velocity integrals of PVF.ResultsPhenylephrine iv increased mean arterial blood pressure from 54 ± 8 mmHg to 73 ± 10 mmHg. This phenylephrineinduced hypertension significantly increased SaO2 and MD (92.0 ± 7.5 vs 95.0 ± 5.0% and 1318 ± 344 vs 1533 ± 425 cm · min−1, respectively). There was a significant correlation (r = 0.72) between the change in MD and the change in SaO2.ConclusionOur results suggest that the phenylephrine-induced increase in systemic blood pressure produces an increase in pulmonary blood flow in tetralogy of Fallot. Our results further suggest that this increase in pulmonary blood flow is involved in the mechanism of phenylephrine-induced improvement of arterial oxygenation in tetralogy of Fallot.RésuméObjectifOn a déjà montré qu’une augmentation de la tension artérielle améllore la saturation en oxygène du sang artériel (SaO2), chez les enfants qui présentent une tétralogie de Fallot, mais aucune étude prospective n’a démontré qu’une augmentation de la tension artérielle pouvait induire une élévation du débit sanguin pulmonaire chez ces patients. Nous voullons vérifier si une augmentation de la tension artérielle générale induite par la phényléphrine fait augmenter le débit sanguin pulmonaire et améliore l’oxygénation artérielle dans le contexte d’une tétralogie de Fallot.MéthodeChez 14 enfants porteurs d’une tétralogie de Fallot et traités consécutivement (âgés de 2–32 mois), les signaux Doppler pulsés transœsophagiens de la vitesse du flux de la veine pulmonaire gauche supérieure (DVP) ont été enregistrés avant, puis quatre minutes après l’administration iv de 10 μg · kg−1 de phényléphrine. Une analyse des gaz du sang artériel et des mesures hémodynamiques ont été réalisées simultanément. La distance minute (DM) a été calculée comme le produit de la fréquence cardiaque et de la somme des intégrales de temps-vélocité du DVR.RésultatsLa phényléphrine iv a augmenté la tension artérielle moyenne de 54 ± 8 mmHg à 73 ± 10 mmHg. L’hypertension induite par la phényiéphrine a augmenté la SaO2 et la DM de façon significative (92,0 ± 7,5 vs 95,0 ± 5,0 % et 1318 ± 344 vs 1533 ± 425 cm · min−1, respectivement). Il y avait une corrélation significative (r = 0,72) entre les modifications de la DM et celles de la SaO2.ConclusionNos résultats suggèrent que, chez les patients atteints d’une tétralogie de Fallot, l’augmentation du débit sanguin général induite par la phényiéphrine produit une élévation du débit sanguin pulmonaire. De plus, il apparaît que cette augmentation du débit sanguin pulmonaire contribue à l’amélioration de l’oxygénation artérielle induite par la phényiéphrine.

Roles of neuronal nitric oxide synthase, oxidative stress, and propofol in N-methyl-d-aspartate-induced dilatation of cerebral arterioles

BACKGROUND It remains unclear whether N-methyl-D-aspartate (NMDA) receptors contribute to cerebral parenchymal vasodilatation, and any effects of clinically used anaesthetics on the dilatation. The present study was designed to examine whether NMDA induces neuronal nitric oxide synthase (NOS)-mediated dilatation, in the cerebral parenchymal arterioles, and whether propofol and superoxide modulate the dilatation in relation to the NMDA receptor activation. METHODS The cerebral parenchymal arterioles within rat brain slices were monitored by a computer-assisted microscopy, and the vasodilatation in response to NMDA (10(-7) to 10(-5) M) was evaluated. Immunofluorescence analysis to neuronal and endothelial NOS and measurement of levels of superoxide and nitric oxide within the arteriole were simultaneously performed. RESULTS Propofol, an NMDA receptor antagonist MK801, and a neuronal NOS antagonist S-methyl-l-thiocitrulline (SMTC) reduced NMDA-induced dilation, whereas a superoxide inhibitor, Tiron, and NADPH oxidase inhibitor, gp91ds-tat, augmented NMDA-induced dilatation. Immunofluorescence analysis revealed distribution of neuronal NOS in both endothelial and smooth muscle cells in addition to neuronal cells. NMDA-induced superoxide and nitric oxide within the parenchymal arterioles. The increased superoxide within the arteriole was similarly inhibited by MK801, SMTC, gp91ds-tat, propofol, and a neuronal NOS antagonist vinyl-l-NIO, whereas the level of nitric oxide was reduced by MK801, SMTC, propofol, and vinyl-l-NIO, and it was augmented by gp91ds-tat. CONCLUSIONS NMDA dilates cerebral parenchymal arterioles possibly via neuronal NOS activation, whereas it produces superoxide via NADPH oxidase. In these arterioles, propofol reduces both the dilatation and superoxide production in response to NMDA.