Serum Levels of Bupivacaine After Bilateral Ultrasound-Guided Deep Parasternal Intercostal Plane Block in Cardiac Surgery with Median Sternotomy.

OBJECTIVE: To evaluate systemic levels of bupivacaine after bilateral ultrasound-guided deep parasternal intercostal plan (PIP) block in cardiac surgical patients undergoing median sternotomy. DESIGN: Prospective, observational study SETTING: Single institution; academic university hospital PARTICIPANTS: Twenty-eight adult patients undergoing cardiac surgery with median sternotomy received a PIP block with 2.5 mg/kg bupivacaine with or without dexamethasone and dexmedetomidine. MEASUREMENTS: Arterial blood samples were analyzed for total serum bupivacaine concentration at 5, 15, 30, 45, 60, 90, 120, and 150 minutes after placement of PIP. Local anesthetic volume, local anesthetic adjuncts, time to extubation, postoperative pain scores, and opioid consumption were recorded. MAIN RESULTS: The mean peak bupivacaine concentration was 0.60 ± 0.62 µg/mL, and the mean time to maximum concentration (Tmax) was 16.92 ± 12.97 minutes. Two patients (7.1%) had a concentration >2.0 µg/mL within 15 minutes of block placement. The mean Tmax of bupivacaine was significantly greater in patients who did not receive additives compared to those patients who did (22.86 ± 14.77 minutes v 10.0 ± 5.22 minutes; p = .004). The times to extubation and postoperative pain were not improved with additives. CONCLUSIONS: Bilateral PIP placed at the end of cardiac surgery resulted in low systemic bupivacaine levels. The inclusion of additives shortened Tmax without improving outcome.

Hemodynamic Monitoring In The Cardiac Surgical Patient: Comparison of Three Arterial Catheters.

OBJECTIVE: Systemic systolic (SAP) and mean (MAP) arterial pressure monitoring is the cornerstone in hemodynamic management of the cardiac surgical patient, and the radial artery is the most common site of catheter placement. The present study compared 3 different arterial line procedures. It is hypothesized that a 20-G 12.7- cm catheter inserted into the radial artery will be equal to a 20-G 12.7- cm angiocath placed in the brachial artery, and superior to a 20-G 5.00 cm angiocath placed in the radial artery. DESIGN: A prospective randomized control study was performed. SETTING: Single academic university hospital. PARTICIPANTS: Adult patients ≥18 years old undergoing nonemergent cardiac surgery using cardiopulmonary bypass (CPB). INTERVENTIONS: After approval by the Rhode Island Hospital institutional review board, a randomized prospective control study to evaluate 3 different peripheral intraarterial catheter systems was performed: (1) Radial Short (RS): 20-G 5- cm catheter; (2) Radial Long (RL): 20-G 12- cm catheter; and (3) Brachial Long (BL): 20-G 12- cm catheter. MEASUREMENTS AND RESULTS: Gradients between central aortic and peripheral catheters (CA-P) were compared and analyzed before CPB and 2 and 10 minutes after separation from CPB. The placement of femoral arterial lines and administration of vasoactive medications were recorded. After exclusions, 67 BL, 61 RL, and 66 RS patients were compared. Before CPB, CA-P SAP and MAP gradients were not significant among the 3 groups. Two minutes after CPB, the CA-P SAP gradient was significant for the RS group (p = 0.005) and insignificant for BL (p = 0.47) and RL (p = 0.39). Two-group analysis revealed that CA-P SAP gradients are similar between BL and RL (p = 0.84), both of which were superior to RS (p = 0.02 and p = 0.04, respectively). At 10 minutes after CPB, the CA-P SAP gradient for RS remained significant (p = 0.004) and similar to the gradient at 2 minutes. The CA-P SAP gradients increased from 2 to 10 minutes for BL (p = 0.13) and RL (p = 0.06). Two minutes after CPB, the CA-P MAP gradients were significant for the BL (p = 0.003), RL (p < 0.0001), and RS (p < 0.0001) groups. Two-group analysis revealed that the CA-P MAP gradients were lower for the BL group compared with the RL (p = 0.054) and RS (p< 0.05) groups. Ten minutes after CPB, the CA-P MAP gradients in the RL and RS groups remained significant (p < 0.0001) and both greater than the BL group (p = 0.002). A femoral arterial line was placed more frequently in the RS group (8/66 = 12.1%) than in the RL group (3/61 = 4.9%) and the BL group (2/67 = 3.0%). Vasopressin was administered significantly more frequently in the RS group. CONCLUSION: Regarding CA-P SAP gradients, the RL group performed equally to the BL group, both being superior to RS. Regarding CA-P MAP gradients, BL was superior to RL and RS. Clinically, femoral line placement and vasopressin administration were fewer for the BL and RL groups when compared with the RS group. This study demonstrated the benefits of a long (12.7 cm) 20- G angiocath placed in the radial artery.

Interaction Between Platelet and Fibrinogen on Clot Strength in Healthy Patients.

OBJECTIVE: The purpose of this study was to explore the relationship between platelet concentration (PLT) (× 109/L) and clot strength measured by thromboelastography maximum amplitude (TEG-MA) in healthy volunteers without a history of coagulation abnormalities. Secondarily, the relationship between fibrinogen (mg/dL) and TEG-MA was analyzed. DESIGN: A prospective study. SETTING: At a university's tertiary-care center. MEASUREMENTS AND MAIN RESULTS: Using whole blood, PLT was reduced in the first part, and hematocrit was reduced in the second part of the study by hemodilution with platelet-rich and -poor plasma. Thromboelastography (TEG 5000 Haemonetics) was performed to measure clot formation and strength. Spearman correlation coefficients regression analyses and receiver-operating characteristics (ROC) were obtained to analyze the relationships among PLT, fibrinogen, and TEG-MA. Strong correlations were found in univariate analysis between PLT and TEG-MA (r = 0.88; p < 0.0001) and between Fibrinogen and TEG-MA (r = 0.70; p = 0.003). A biphasic relationship between PLT and TEG-MA was linear below a PLT 90 × 109/L, followed by a plateau above 100 × 109/L (p = 0.001). A linear relationship between fibrinogen (190-474 mg/dL) and TEG-MA (53-76 mm) was found (p = 0.0007). The ROC analysis found that PLT = 60 × 109/L was associated with a TEG-MA of 53.0 mm. The product of PLT and fibrinogen concentrations was more strongly correlated (r = 0.91) to TEG-MA than either PLT (r = 0.86) or fibrinogen (r = 0.71) alone. A ROC analysis revealed that a TEG-MA of 55 mm was associated with a PLT × fibrinogen of 16,720. CONCLUSION: In healthy patients, a PLT of 60 × 109/L was associated with normal clot strength (TEG-MA ≥53 mm), and there was little change in clot strength with PLT >90 × 109/L. Although prior analyses described the contributions of platelets and fibrinogen toward clot strength, they are presented and discussed independently. The data above described clot strength as an interaction among them. Future analyses and clinical care should evaluate and recognize the interplay.

Transesophageal echocardiographic imaging of the coronary sinus: a retrospective analysis of mid-esophageal views and a novel transgastric view.

BACKGROUND: Transesophageal echocardiographic imaging plays an important role in assessing coronary sinus anatomy prior to placement of a retrograde cardioplegia cannula. The coronary sinus can be imaged in the long axis by advancing the TEE probe from the mid-esophageal 4-chamber view or using a modified mid-esophageal bicaval view, while a short axis view can be obtained in the mid-esophageal 2-chamber view. While use of a transgastric view is only briefly mentioned in the literature as an alternative to mid-esophageal views, the authors commonly include it in our comprehensive transesophageal echocardiographic exam of the coronary sinus. This study examines the various imaging strategies. We hypothesize that the transgastric view offers comparable coronary sinus imaging to the mid-esophageal views. METHODS: After approval by our institutional review board, the intraoperative transesophageal echocardiographic exams for 50 consecutive elective cardiac surgical patients with a comprehensive echocardiographic assessment of the coronary sinus were retrospectively reviewed and analyzed to evaluate imaging of the coronary sinus in the various views. For each view, we noted and recorded if the coronary sinus and coronary sinus cannula were visualized. Statistical analysis required pairwise comparisons between each of the 4 views. P values were calculated using McNemar's Exact test. RESULTS: Both the coronary sinus and coronary sinus cannula were visualized a majority of the time for each view. There was no statistically significant difference between each view in its ability to visualize the coronary sinus, nor was there a statistically significant difference between each view in its ability to visualize the coronary sinus cannula. CONCLUSIONS: Use of a transgastric window provides the echocardiographer with an effective alternate modality for imaging the coronary sinus when mid-esophageal views are limited.

The Intraoperative Assessment of Right Ventricular Function During Cardiac Surgery.

The importance of right ventricular (RV) dysfunction in patients undergoing cardiac surgery is well recognized. There is extensive literature regarding the accurate assessment of RV dysfunction with both echocardiography and hemodynamic data, but the majority of these studies are with transthoracic echocardiography (TTE) and in awake patients. Many of the tools used to assess the RV with TTE are angle-dependent and, therefore, may be inaccurate with transesophageal echocardiography (TEE). Very few of these modalities have been validated either with TEE or in patients under general anesthesia. The purpose of this review is to discuss the intraoperative tools available to the cardiac anesthesiologist for the assessment of RV function. The authors review the available literature surrounding intraoperative RV assessment, from subjective assessment to traditional objective tools that were developed for TTE and newer technology that can be adapted to both TTE and TEE. Future work should focus on whether or not these intraoperative RV assessment tools predict outcome after cardiac surgery.

Echocardiographic Assessment of the Mitral Valve for Suitability of Repair: An Intraoperative Approach From a Mitral Center.

Intraoperative echocardiography of the mitral valve in the precardiopulmonary bypass period is an integral part of the surgical decision-making process for assessment of suitability for repair. Although there are comprehensive reviews in the literature regarding echocardiographic examination of the mitral valve, the authors present a practical stepwise algorithmic workflow to make objective recommendations. Advances in echocardiography allow for quantitative geometric analyses of the mitral valve, along with precise assessment of the valvular apparatus with three-dimensional echocardiography. In the precardiopulmonary bypass period, echocardiographers are required to diagnose and quantify valvular dysfunction, assess suitability for repair, assist in annuloplasty ring sizing, and determine the success or failure of the surgical procedure. In this manuscript the authors outline an algorithmic approach to intraoperative echocardiography examination using two-dimensional and three-dimensional modalities to objectively analyze mitral valve function and assist in surgical decision-making.

A Pilot Study to Assess the Clinical Onset of IV Heparin in Interventional Cardiology and Cardiac Surgery.

OBJECTIVES: To determine the onset of heparin anticoagulation, using 2 different measures of activated clotting times (ACT), thromboelastography (TEG; R-time), and anti-Xa levels, after administering low- (100 U/kg) and high- (300 U/kg) dose intravenous (IV) heparin to patients undergoing transcatheter aortic valve replacement (TAVR) and cardiac surgery, respectively. DESIGN: Prospective study. SETTING: Single academic institution. PARTICIPANTS: Patients with normal baseline coagulation presenting for TAVR or cardiac valve surgery. INTERVENTIONS: Coagulation studies were performed at baseline, 30 seconds, 90 seconds, and 180 seconds after IV heparin administration. The tests included iSTAT (iACT) and Hemochron ACT (hACT), TEG R-Time, and anti-Xa levels. At the authors' institution, anti-Xa is the preferred measure of heparin anticoagulation when time permits. ACT, a rapid point- of-care test, is used to assess intraprocedural anticoagulation. MEASUREMENTS AND MAIN RESULTS: After both low- and high-dose heparin, there are peak increases in ACT and anti-Xa at 30 seconds, followed by a decline at 90 seconds and plateau at 180 seconds. The TEG R-time remained elevated (>80 minutes) throughout. For TAVR cases, all anti-Xa was >1.5 IU/mL, and was associated with an iACT >180 seconds and an hACT >200 seconds. For cardiac valve surgery cases, all anti-Xa was >2.4 and associated with an iACT >420 seconds and and hACT >340 seconds. Compared with hACT, iACTs were significantly lower at all time points after low-dose heparin, but not after high-dose heparin. CONCLUSIONS: In this pilot study, heparin anticoagulation was detected as early as 30 seconds after IV administration, based on ACT, anti-Xa levels, and TEG R-time.

The Left Ventricular Outflow Tract Changes in Size and Shape From Pre- to Post-Cardiopulmonary Bypass: Three-Dimensional Transesophageal Echocardiography.

OBJECTIVES: To compare two-dimensional (2D) and 3D imaging of the left ventricular outflow tract (LVOT) and to evaluate geometric changes pre- to post-cardiopulmonary bypass (CPB). DESIGN: Retrospective review of intraoperative transesophageal echocardiographic examinations. SETTING: Single academic medical center. PARTICIPANTS: The study comprised 69 cardiac surgical patients-27 with aortic valve stenosis (AS) and 42 without AS. INTERVENTIONS: Two-dimensional and 3D analysis of the LVOT pre- and post-CPB. MEASUREMENTS AND MAIN RESULTS: Pre- and post-CPB 2D assessment of LVOT diameter (2D LVOTd) was compared with 3D analysis of the minor (3D LVOTd-min) and major diameters. LVOT areas (LVOTa) were calculated using LVOTd to yield 2D LVOTa and 3D LVOTa-min. These were compared with LVOTa measured by planimetry (3D LVOTa-plan). An ellipticity ratio (ER) (ER = 3D minor/major axes) was calculated. The 2D LVOTd was larger than the 3D LVOTd-min before (2.12 v 2.02 cm respectively (resp); p < 0.001) and after (1.96 v 1.85 cm resp; p = 0.04) CPB. Compared with pre-CPB, there were significant decreases in the 2D LVOTd (p = 0.003) and the 3D LVOTd-min (p < 0.001) post-CPB. Ellipticity increased after CPB (ER 0.80 v 0.75; p = 0.004), and the 2D LVOTa was larger than the 3D LVOTa-min before CPB (3.60 cm2v 3.28 cm2; p < 0.001) and less so after CPB (3.11 cm2v 2.79 cm2; p = 0.053). Compared with pre-CPB, all LVOTa measurements decreased significantly after CPB (p < 0.001). The 3D LVOTa-plan decreased after CPB by approximately 10% (4.05 cm2v 3.61 cm2; p < 0.001). The 2D LVOTa and 3D LVOTa-min underestimated the 3D LVOTa-plan before and after CPB (p < 0.001) by 11% to 14% and 19% to 23%, respectively. When compared with non-AS patients, patients with AS had a smaller LVOTa pre- and post-CPB (p < 0.05). CONCLUSIONS: The LVOT is smaller and more elliptical after CPB. Patients with AS have a smaller LVOT compared with non-AS patients. LVOTa calculated using LVOTd underestimates the 3D LVOTa-plan by as much as 23% depending on patient type and timing of measurement. Accurate assessment of the LVOT requires 3D imaging.

The Mitral Coaptation to Ventricular Septal Space: Two- and Three-Dimensional Transesophageal Echocardiographic Assessment.

OBJECTIVES: To assess the dimensions and changes in the CSEPT (space between the ventricular septum and mitral coaptation point) before and after cardiopulmonary bypass (CPB) and to compare patients with and without aortic valve stenosis (AS) undergoing cardiac surgery. DESIGN: Retrospective review of intraoperative transesophageal echocardiographic examinations. SETTING: Single academic medical center. PARTICIPANTS: The study comprised 91 elective cardiac surgical patients-30 with AS scheduled for aortic valve replacement and 61 without AS (non-AS). INTERVENTIONS: Two- and 3-dimensional (2D and 3D) analysis of the CSEPT before and after CPB. MEASUREMENTS AND MAIN RESULTS: Assessment of the CSEPT distances and areas was performed using 2D and 3D imaging before and after CPB. Two-dimensional measures of CSEPT distances were performed using midesophageal 5-chamber and long-axis windows. Three-dimensional measures were performed offline using multiplanar reconstruction. The CSEPT space was smaller after CPB (p < 0.01). Before and after CPB, the midesophageal 5-chamber and long-axis windows were similar to each other, and both were larger than the pre-CPB 3D CSEPT distance. Patients with AS had smaller before and after CPB distances and areas compared with non-AS patients (p < 0.05). The change in CSEPT area in AS patients was 24%. CONCLUSIONS: The CSEPT space is smaller after CPB and more so for patients with AS undergoing aortic valve replacement. Two-dimensional CEPT distances vary compared with 3D CSEPT distances. Additional study using Doppler analysis will elucidate the added value of 3D assessment of the CSEPT space.

A Case of Prolonged Angioedema After Cardiac Surgery.

Angioedema (AE) is a transient capillary leak syndrome, caused by either histamine or bradykinin, that presents as an acute nonpitting swelling of the skin, subcutaneous tissues, and mucous membranes of the face, lips, tongue, upper airways, and gastrointestinal tract, with or without a rash. A lack of response to antihistamines, steroids, and epinephrine suggests a bradykinin-mediated AE. Bradykinin-AE may be inherited, acquired, or drug related. Mechanism of increased bradykinin can include decreased C1-esterase inhibitor (C1-INH) levels or activity, increased bradykinin production, or decreased bradykinin breakdown, the latter occurring during angiotensin converting enzyme inhibitor (ACEi). A 65-year-old woman had coronary artery bypass grafting, which was complicated by prolonged bradykinin-AE owing to ACEi, requiring prolonged endotracheal tube intubation. Treatment with a C1-esterase inhibitor (Berinert) on postoperative day 7 resulted in a dramatic improvement in airway edema and tongue swelling within 7 hours, and the patient was subsequently extubated. The case is unusual because of the prolonged course of AE and the benefit of late administration of C1-INH concentrate.

Artificial Intelligence-Based Assessment of Indices of Right Ventricular Function.

OBJECTIVES: Echocardiographic assessment of right ventricular (RV) function is based largely on visual estimation of tricuspid annulus and motion of the free wall. Regional strain analysis has provided an objective measure of myocardial performance assessment, but is limited in use by vendor-specific software. The study was designed to investigate statistical correlation between RV region-specific strain and echocardiographic parameters of RV function using a vendor-neutral RV-specific strain assessment program. DESIGN: This is a retrospective study. SETTING: Tertiary hospital. PARTICIPANTS: One hundred seven patients undergoing coronary artery bypass graft, valve repair or replacement, or a combination of procedures. INTERVENTION: None. MEASUREMENTS AND MAIN RESULTS: One hundred seven patients underwent comprehensive echocardiographic of RV function intraoperatively. Off-line analysis of global, longitudinal, and septal strain was performed using a vendor-neutral software. The 2 values were compared statistically. All pairs demonstrated strong statistical significance; the strongest relationships were between (1) RV fractional area change (FAC) (%)-RV longitudinal strain (r2 = 0.83, p < 0.001), and (2) tricuspid annular plane systolic excursion (mm)-lateral S' velocity (cm/s) (r2 = 0.80, p < 0.001). The weakest correlations were (1) RV FAC (%)-lateral S' velocity (cm/s) (r2 = 0.37, p < 0.001), and (2) lateral S' velocity (cm/s)-RV longitudinal strain (r2 = 0.40, p < 0.001). CONCLUSION: RV function can be assessed objectively by strain analyses across different platforms using the artificial intelligence-based vendor-neutral strain analysis software. There is a statistically significant correlation between strain values and conventional 2-dimensional echocardiographic parameters of RV function.

Echocardiographic Predictors of Tricuspid Ring Annuloplasty Repair Failure for Functional Tricuspid Regurgitation.

OBJECTIVE: Significant tricuspid regurgitation (TR) recurs after tricuspid valve repair of functional TR in 15% to 20% within the first year, and 30% to 70% within 5 years. Prior investigations report leaflet tethering, and not tricuspid valve annular diameter (TVAD), as predictive of recurrent TR. The authors hypothesize that pre-repair TVAD is predictive of repair failure for functional TR. PARTICIPANTS: Fifty-four patients with functional TR scheduled for left heart surgery and tricuspid valve repair with ring annuloplasty. DESIGN: Retrospective study design. Pre- and post-repair transthoracic and intraoperative transesophageal echocardiographic data included left and right ventricular functions, tricuspid leaflet tethering height, TVAD, and TR severity. Successful repair was defined as ≤2+ TR. SETTING: Tertiary care medical center. INTERVENTIONS: None. MEASUREMENTS: Forty-five patients had a successful repair and 9 did not. Preoperative and intraoperative TVAD in diastole (TVADdiast) ≥4.2 cm, and preoperative systole (TVADsyst) ≥3.7 cm, but not leaflet tethering, were predictive of repair failure. Right ventricular (RV) width >4.88 cm was associated with repair failure. Neither pre- nor post-repair pulmonary artery systolic pressures (PASP) were predictors of repair failure. However, PASP did not change nor did RV function improve in the nonsuccessful repair group. CONCLUSION: For patients with functional TR undergoing primary left heart surgery, preoperative TVAD (systole and diastole), RV width, and postoperative RV function were predictors of repair outcome. Earlier TV repair and optimizing right heart function may improve repair outcome.

Assessment of Heparin Anticoagulation Measured Using i-STAT and Hemochron Activated Clotting Time.

OBJECTIVE: Adequate anticoagulation, measured using activated clotting time (ACT), is important during vascular and cardiac surgeries. Unfractionated heparin is the most common anticoagulant used. The purpose of this analysis was to compare the i-STAT ACT (iACT) to the Hemochron ACT (hACT), both of which were then compared to anti-factor Xa (anti-Xa) assay, a representation of heparin level and activity. DESIGN: Prospective study. SETTING: Tertiary care cardiovascular center. PARTICIPANTS: Eleven consecutive elective adult cardiac surgical patients. INTERVENTIONS: Prior to cardiopulmonary bypass, ACTs were measured using i-STAT and Hemochron technologies and compared to each other and to anti-Xa assay prior to and during a cumulative administration of heparin. Data were compared using bias analyses. MEASUREMENTS AND MAIN RESULTS: Heparin (300 U/kg) was administered in quarterly doses. Coagulation labs were collected prior to and 3 minutes after each quarterly dose of heparin. The baseline ACTs for i-STAT and Hemochron were 147 and 142 seconds, respectively. A significant association was found between iACT and hACT (p = 0.002). The iACT measurements underestimated hACT at ACT levels >180 seconds or anti-Xa levels >0.75 U/mL. No significant difference was found between ACT data at anti-Xa levels <0.5 U/mL. CONCLUSION: There was a good association between the iACT and hACT; however, the 2 tests are not equivalent. Overall, the iACT underestimated the hACT. Agreement between the ACT technologies was good at lower ACTs and anti-Xa levels, but declined with an anti-Xa >0.75 U/mL.

Heterogeneity in the Structure of the Left Ventricular Outflow Tract: A 3-Dimensional Transesophageal Echocardiographic Study.

BACKGROUND: The left ventricular outflow tract (LVOT) is a composite of adjoining structures; therefore, a circular or elliptical shape at one point may not represent its entire structure. The purpose of this study was to evaluate the presence of heterogeneity in the LVOT. METHODS: Patients with normal valvular and ventricular function undergoing elective coronary revascularization surgery were included in the study. Intraoperative R-wave gated 3-dimensional (3D) transesophageal echocardiographic imaging of the LVOT was performed at end-systole, with the midesophageal long axis as the reference view. Acquired data were analyzed with the Philips Q-Lab software with multiplanar reformatting in the sagittal (minor axis), transverse (major axis), and coronal (cross-sectional area by planimetry) views of the LVOT. These measurements were made on the left ventricular side or proximal LVOT, aortic side, or distal LVOT and mid-LVOT. RESULTS: Fifty patients were included in the study. The LVOT minor (sagittal) axis dimension did not differ across the mid-LVOT, proximal LVOT, and distal LVOT (P = .11). The major axis diameter of LVOT differed among the 3 regions of the LVOT (P < .001). A difference in major axis diameter was observed between the proximal and the distal LVOT (median difference of 0.39 cm; Bonferroni-adjusted 95% confidence interval [CI] of the difference = 0.31-0.48 cm; Bonferroni-adjusted P < .001). Planimetry of the LVOT area differed significantly (P < .001) between the regions analyzed, and we found a difference between the distal and the proximal LVOT (median difference = 0.65 cm, Bonferroni-adjusted 95% CI of the difference = 0.44-0.88 cm, Bonferroni-adjusted P < .001). The LVOT area calculated from minor axis diameter differed significantly from the area obtained by planimetry (P < .001). CONCLUSIONS: There was heterogeneity in the major axis diameter and cross-sectional area for the different regions of the LVOT. The distal LVOT (aortic side) was more circular, whereas the proximal LVOT (left ventricular side) was more elliptical in shape. This change in shape from circular to elliptical was accounted for by a difference in the major axis diameter from proximal to distal LVOT and a relatively similar minor axis diameter. Although the clinical significance of this finding is unknown, the assumption of a uniform structure of LVOT is incorrect. Three-dimensional imaging may be useful for assessing the LVOT shape and size at a specific region of interest.

Point-of-Care Hemoglobin/Hematocrit Testing: Comparison of Methodology and Technology.

OBJECTIVE: Point-of-care (POC) testing allows rapid assessment of hemoglobin (Hgb) and hematocrit (Hct) values. This study compared 3 POC testing devices--the Radical-7 pulse oximeter (Radical-7, Neuchȃtel, Switzerland), the i-STAT (Abbott Point of Care, Princeton, NJ), and the GEM 4000 (Instrumentation Laboratory, Bedford, MA)--to the hospital reference device, the UniCel DxH 800 (Beckman Coulter, Brea, CA) in cardiac surgery patients. DESIGN: Prospective study. SETTING: Tertiary care cardiovascular center. PARTICIPANTS: Twenty-four consecutive elective adult cardiac surgery patients. INTERVENTIONS: Hgb and Hct values were measured using 3 POC devices (the Radical-7, i-STAT, and GEM 4000) and a reference laboratory device (UniCel DxH 800). Data were collected simultaneously before surgery, after heparin administration, after heparin reversal with protamine, and after sternal closure. Data were analyzed using bias analyses. POC testing data were compared with that of the reference laboratory device. MEASUREMENTS AND MAIN RESULTS: Hgb levels ranged from 6.8 to 15.1 g/dL, and Hct levels ranged from 20.1% to 43.8%. The overall mean bias was lowest with the i-STAT (Hct, 0.22%; Hgb 0.05 g/dL) compared with the GEM 4000 (Hct, 2.15%; Hgb, 0.63 g/dL) and the Radical-7 (Hgb 1.16 g/dL). The range of data for the i-STAT and Radical-7 was larger than that with the GEM 4000, and the pattern or slopes changed significantly with the i-STAT and Radical-7, whereas that of the GEM 4000 remained relatively stable. The GEM 4000 demonstrated a consistent overestimation of laboratory data, which tended to improve after bypass and at lower Hct/Hgb levels. The i-STAT bias changed from overestimation to underestimation, the latter in the post-cardiopulmonary bypass period and at lower Hct/Hgb levels. By contrast, the Radical-7 biases increased during the surgical procedure and in the lower ranges of Hgb. CONCLUSION: Important clinical differences and limitations were found among the 3 POC testing devices that should caution clinicians from relying on these data as sole determinants of when or when not to perform transfusion in patients. Even though a low bias might support the use of POC data, further analysis of the bias plots demonstrates pattern changes during the surgical procedure and across the range of Hct/Hgb data.