Toshihito Tsubo

The relationship between pneumatic tourniquet time and the amount of pulmonary emboli in patients undergoing knee arthroscopic surgeries.

Near-fatal pulmonary embolism can occur immediately after tourniquet release after orthopedic surgeries. In this study, we determined the relationship between tourniquet time and the occurrence of pulmonary emboli in 30 patients undergoing arthroscopic knee surgeries, by using transesophageal echocardiography. The right atrium (RA) was continuously monitored by transesophageal echocardiography, and the number of emboli present was assessed with the following formula: Amount of emboli = 100 × [(total embolic area in the RA after tourni-quet release) − (total area of emboli or artifact in the RA before tourniquet release)]/(RA area). The area was assessed 0–300 s after tourniquet release by using image-analysis software. The peak amount of emboli appeared approximately 50 s after tourniquet release. In addition, there was a significant correlation between amount of emboli (Ae [%]) and tourniquet time (Ttq [min]): (Ae = 0.1 × Ttq − 1.0, r = 0.795, P < 0.01). This study suggests that acute pulmonary embolism may occur within 1 min of tourniquet release and that the number of emboli is dependent on Ttq.

A new non-invasive continuous cardiac output trend solely utilizing routine cardiovascular monitors.

Objective. Three of the us developed a new non-invasive continuous cardiac output (CCO) measurement method utilizing routine clinical monitors based on the pulse-contour analysis combined with pulse wave transit time (PWTT). Using pulmonary artery catheter (CCOpa), we compared this estimated CCO (esCO) with the thermodilution CCO early after cardiac surgery, and tested whether the esCO method has potential of being an alternative measure of CCO. Methods. Thirty-six patients without continued arrhythmias were studied. esCO was computed using electrocardiogram (ECG) monitor, arterial pressure monitor and pulse-oximetry system. Both sets of data (esCO and CCOpa), by averaging the results of the preceding 10 min, were compared at 30-min intervals throughout the 15.8± 3.3 h (S.D.) of study. Bland–Altman plots and correlation analysis were used for statistical comparison. Results. A total of 981 paired sets of data (89.9%) among 1093 measurements were compared in the absence of displacement of either pulse-oximetry or ECG probes and/or inaccurate detection of R wave. The difference between esCO and CCOpa results was −0.06 ± 0.82 L/min (S.D.), and there was a linear correlation between them (r = 0.80, p < 0.0001). The difference between them was 0.00± 0.48 L/min at the first 1 h, which remained unchanged throughout 20 h after the start of measurement. Conclusions. The results demonstrate that esCO has a close correlation with the CCOpa, even though the two methods are not interchangeable. The results suggest that esCO method has potential of being an alternative non-invasive cardiac output trend, unless there are apparent arrhythmias.

Detection of capillary protein leakage by glucose and indocyanine green dilutions during the early post-burn period

Overestimation of the plasma volume determined by the indocyanine green (ICG) dilution method (PV-ICG) may occur after burns, since this dye has the potential of extravasation in the presence of the capillary protein leakage. Assuming that the initial distribution volume of glucose (IDVG) consistently indicates the extracellular fluid volume of highly perfused organs including plasma, overestimation of the PV-ICG can be detected by a higher PV-ICG/IDVG ratio. The present study was designed to test whether a higher PV-ICG/IDVG ratio is observed within 24 h post-burn compared to the subsequent days. Ten severely burned adult patients admitted to the ICU were studied through the 2nd post-burn day. The daily IDVG and PV-ICG were calculated using a one compartment model by simultaneous administration of glucose, 5 g, and ICG, 25 mg. Although the IDVG increased on the 1st post-burn day (p < 0.05), the PV-ICG remained unchanged. The PV-ICG/IDVG ratio within 24 h post-burn was significantly higher than that on the 1st post-burn day (p < 0.01). Results indicate that overestimation of the PV-ICG can occur within 24 h post-burn and suggest that simultaneous measurement of the IDVG and the PV-ICG would help predict the generalized capillary protein leakage after burns.

Detection of capillary protein leakage by indocyanine green and glucose dilutions in septic patients.

Objective: To determine whether indocyanine green (ICG) and glucose dilutions can detect generalized capillary protein leakage in septic patients without requiring repeated measurements. Design: Prospective, clinical study. Setting: General intensive care unit. Patients: Twelve consecutive patients who met the criteria of sepsis and 16 consecutive acute myocardial infarction (AMI) patients without any underlying pathology inducing generalized protein capillary leakage. Interventions: Both ICG 25 mg and glucose 5 g were administered simultaneously, to calculate the plasma volume determined by the ICG dilution method (PV‐ICG) and the initial distribution volume of glucose (IDVG), on day 1 of sepsis or on day 1 of hospitalization for the AMI patients. The relationship between these two volumes and the PV‐ICG/IDVG ratio was evaluated in two patient groups. Measurements and Main Results: Although the IDVG of the two patient groups was not statistically different, the PV‐ICG in the septic patients was higher than that in the AMI patients (p < .01). Consequently, the PV‐ICG/IDVG ratio in the septic patients was higher than that in the AMI patients (p < .01). Eight of the 12 septic patients had a PV‐ICG/IDVG ratio of >0.45, which was not observed in any of the AMI patients. The PV‐ICG/IDVG ratio in the septic patients correlated inversely with the total plasma protein concentration (r2 = .46, p < .025) and mean arterial pressure (r2 = .42, p < .05). Conclusions: Our results indicate that overestimation of the PV‐ICG can occur in septic patients and, further, suggest that simultaneous measurement of the two distribution volumes would help predict generalized capillary protein leakage in septic patients without repeated measurement.

Quantification and comparison of pulmonary emboli formation after pneumatic tourniquet release in patients undergoing reconstruction of anterior cruciate ligament and total knee arthroplasty

The amount of emboli formed (percentage of total emboli area to the right atrial area [%Ae]) after tourniquet release in invasive procedures of the medullary cavity is empirically much larger than that in noninvasive procedures, even if the tourniquet duration is similar. Thus, we compared %Ae between arthroscopic reconstruction of the anterior cruciate ligament (ACL, n = 20) and total knee arthroplasty (TKA, n = 20). The right atrium was continuously monitored by transesophageal echocardiography to assess %Ae. Peak %Ae ± sd (ACL, 4.1% ± 3.4%; TKA, 20.7% ± 16.7%) appeared 30–40 s after tourniquet release in both groups. However, %Ae in the TKA group was always larger than the peak %Ae in the ACL group. In addition, although the ETco2 significantly increased after tourniquet release in both groups, increase of ETco2 (1.1% ± 0.3%) in the ACL group was significantly larger than that in the TKA group (0.5% ± 0.2%). An increase in ETco2 was inversely proportional to peak %Ae (P < 0.01;r = 0.703). Therefore, the present data suggest that the risk of acute pulmonary embolism after tourniquet release may be more frequent during TKA than ACL.

Density Detection in Dependent Left Lung Region Using Transesophageal Echocardiography

Background Densities in dependent lung regions worsen oxygenation in patients with acute respiratory distress syndrome. Identification of these densities requires examination using computed tomography (CT). In this study, the authors evaluated the use of transesophageal echocardiography (TEE) to estimate densities in the dependent lung. Methods Forty consecutive patients with acute lung injury or acute respiratory distress syndrome who underwent CT and TEE examination were included in this study. Densities in the lower left lung area were detected through the descending aorta by TEE. Density areas observed by TEE were compared with those obtained by CT. The effect of positive end-expiratory pressure (PEEP) application on density area was also evaluated. Results Density areas in the dependent lung region measured by TEE were 12.0 ± 6.1 cm2 (mean ± SD) at mid esophageal position. Density areas evaluated using TEE in the left lung correlated significantly with those estimated with CT in the left and right lungs (P < 0.01 in both lungs). In addition, the authors observed a significant correlation between Pao2/Fio2 and density areas estimated using TEE (P < 0.05). During positive end-expiratory pressure application, the area of density estimated with TEE decreased and Pao2 improved. Conclusions The authors clearly demonstrated that it is possible to estimate the density area of the dependent left lung regions in patients with acute lung injury or acute respiratory distress syndrome using TEE. It is also possible to observe the changes of density areas during application of positive end-expiratory pressure.

Decreased glucose utilization during prolonged anaesthesia and surgery

We studied the influence of prolonged anaesthesia and surgery on glucose metabolism by means of the euglycaemic insulin clamp method in eight patients who underwent prolonged surgery. Eleven patients who underwent surgery of short duration served as a control group. Plasma concentrations of catabolic hormones were measured simultaneously. Glucose utilization during prolonged anaesthesia, (PA) group, was lower than that in the control group (P < 0.01) (glucose utilization 7.59 ± 0.73 mg · kg−1 · hr−1 in the control group vs 4.03 ± 0.71 mg · kg−1 hr−1 in PA group respectively). There were no significant differences in plasma catecholamine and glucagon concentrations between the PA and control groups. Plasma-free fatty acid levels increased significantly in the PA group before the euglycaemic insulin clamp (free fatty acid level: 0.496 ± 0.053 mmol·L−1 in the control group, vs 0.834 ± 0.103 mmol·L−1 in the PA group at the pre-clamp period, P < 0.01). Tissue resistance to exogenous insulin increased during prolonged anaesthesia and surgery although there were no significant changes in plasma catabolic hormone levels.RésuméOn a étudié l’influence de l’anesthésie prolongée et la chirurgie sur le métabolisme du glucose en utilisant le lest «Euglycaemic insulin clamp method» chez huit patients devant subir une chirurgie prolongée. Onze patients devant subir une chirurgie de courte durée ont servi comme groupe contrôle. Les concentrations plasmatiques des hormones de catabolisme ont été mesurées simultanément. l’utilisation du glucose durant l’anesthésie prolongée (PA), dans le groupe PA, était plus basse que celle du groupe contrôle (P < 0.01) (l’utilisation du glucose 7,59 ± 0,73 mg · kg−1 · hre−1 pour le groupe contrôle versus 4,03 ± 0,71 mg · kg−1 · hre−1 dans le groupe PA). Il n’y avail aucune différence significative dans les catécholamines plasmatiques et les contractions de glucagon entre le groupe PA et le groupe contrôle. Le taux d’acide gras plasmatique libre a augmenté significativement dans le groupe PA avant le test de «Eu glycaemic insulin clamp» (taux d’acide gras libre: 0,496 ± 0,053 mmol · L−1 pour le groupe contrôle versus 0,834 ± 0.103 mmol · L−1 dans le groupe PA pour la période pré-clampage, P < 0,01). La résistance tissulaire à l’insuline exogène a augmenté durant l’anesthésie prolongée et la chirurgie même s’il n’y avait aucun changement significatif dans le niveau des hormones de catabolisme.

The initial distribution volume of glucose and cardiac output in the critically ill

Blood or plasma glucose concentration can be measured accurately and rapidly. However, after a glucose challenge metabolism may modify glucose kinetics, so that glucose has not been used as an indicator for dilution volumetry. To test the hypothesis that the initial distribution volume of glucose (IDVG) reflects cardiac output rather than glucose metabolism in the critically ill, the relationship between IDVG and thermodilution cardiac output was evaluated at 27 points in 13 non-surgical, critically ill patients without congestive heart failure. The IDVG was calculated from incremental plasma glucose concentrations using a one compartment model. Correlations were obtained between the IDVG and cardiac output (r = 0.89, n = 27, P < 0.001), and between the incremental plasma glucose concentrations three minutes after the injection and the IDVG (r = 0.94, n = 27, P < 0.001). No difference was found between the IDVG with or without continuous insulin infusions. The results indicate that the IDVG reflects cardiac output rather than glucose metabolism in patients without congestive heart failure.RésuméIl est possible de mesurer la concentration plasmatique du glucose avec précision et rapidité. Cependent, après un test d’hyperglycémie provoquée, le métabolisme peut modifier le cynétique du glucose. Pour cette raison le glucose n’est pas employé comme indicateur pour l’analyse volumétrique par la méthode de dilution. Pour vérifier l’hypothèse selon laquelle le volume de distribution initial du glucose (VDIG) reflète le débit cardiaque plutôt que le métabolisme glucidique chez le grand malade, la relation entre VDIG et débit cardiaque est comparée à 27 moments chez 13 grands malades non chirurgicaux sans insuffisance cardiaque. Le VDIG est calculé à partir de concentrations plasmatiques croissantes dans un modèle à compartiment unique. On détermine la corrélation entre VDIG et débit cardiaque (r = 0,89, n = 27, P <0,001), et entre les concentrations croissantes de glucose plasmatique trois minutes après l’injection et le VDIG (r = 0,94, n = 27, P < 0,001). Il n’y a pas de différence entre le VDIG mesuré avec ou sans perfusions d’insuline. Les résultats démontrent que le VDIG reflète plus le débit cardiaque que le métabolisme glucidique chez le malade qui ne présente pas d’insuffisance cardiaque.

Evaluation of density area in dorsal lung region during prone position using transesophageal echocardiography

ObjectiveTo evaluate the changes of density area in the dorsal lung regions of acute respiratory distress syndrome patients during prone position using transesophageal echocardiography. DesignRetrospective clinical study. SettingGeneral intensive care unit in a university hospital. PatientsTen patients with acute respiratory distress syndrome who underwent prone position therapy. InterventionsDensity areas in the left dorsal lung region were observed using transesophageal echocardiography before and after patients were in the prone position for 2 hrs. In five patients, a pediatric transesophageal echocardiography probe was left in the esophagus and used for observation during the prone procedure. Measurements and Main ResultsChanges of density area and Pao2/Fio2 were observed. The density areas decreased after prone position compared with those of preprone position (preprone 11.4 ± 5.1 cm2, after prone 5.6 ± 3.5 cm2, mean ± sd, p < .01, respectively). There was also a significant correlation between the percentage change of density area and Pao2/Fio2 (r = .47, p < .05) after prone position. During prone position, the density area decreased; however, there was no correlation between the percent changes of density area and Pao2/Fio2. ConclusionIt was possible to observe the change in density area during prone position using transesophageal echocardiography. The change of density area estimated with transesophageal echocardiography during prone position was useful to estimate the effectiveness of the procedure.

Does Indocyanine Green Accurately Measure Plasma Volume Early After Cardiac Surgery

Potential overestimation of plasma volume (PV) determination by the conventional indocyanine green (ICG) dilution method (PV-ICG) can occur when generalized capillary protein leakage is present, because ICG binds to proteins. We recently reported that this overestimation can be recognized by simultaneous measurement of the initial distribution volume of glucose (IDVG). We examined whether overestimation of PV-ICG and further ICG-pulse dye densitometry-derived plasma volume (PV-PDD) can occur early after cardiac surgery by using the PV-ICG/IDVG ratio as an indicator. Possible overestimation was defined as a ratio higher than 0.45. Twenty-four consecutive postcardiac surgical patients were enrolled. PV-ICG, PV-PDD, and IDVG were calculated simultaneously after admission to the intensive care unit and on the first postoperative day. The mean ± sd PV-ICG/IDVG ratio for 47 recordings was 0.38 ± 0.05. Four had a PV-ICG/IDVG ratio higher than 0.45, and the highest was 0.48. The mean PV-PDD/IDVG ratio for a total of 47 recordings was 0.39 ± 0.10. There were extremely high or low ratios observed in PV-PDD determinations, but they were not observed in PV-ICG determinations. Results suggest that most of the PV-ICG measurements are accurate, but inaccuracy of PV-PDD can occur early after cardiac surgery.