In Vitro Evaluation of a Novel Image Processing Device to Estimate Surgical Blood Loss in Suction Canisters.

BACKGROUND: Clinicians are tasked with monitoring surgical blood loss. Unfortunately, there is no reliable method available to assure an accurate result. Most blood lost during surgery ends up on surgical sponges and within suction canisters. A novel Food and Drug Administration-cleared device (Triton system; Gauss Surgical, Inc, Los Altos, CA) to measure the amount of blood present on sponges using computer image analysis has been previously described. This study reports on performance of a complementary Food and Drug Administration-cleared device (Triton Canister System; Gauss Surgical, Inc, Los Altos, CA) that uses similar image analysis to measure the amount of blood in suction canisters. METHODS: Known quantities of expired donated whole blood, packed red blood cells, and plasma, in conjunction with various amounts of normal saline, were used to create 207 samples representing a wide range of blood dilutions commonly seen in suction canisters. Each sample was measured by the Triton device under 3 operating room lighting conditions (bright, medium, and dark) meant to represent a reasonable range, resulting in a total of 621 measurements. Using the Bland-Altman method, the measured hemoglobin (Hb) mass in each sample was compared to the results obtained using a standard laboratory assay as a reference value. The analysis was performed separately for samples measured under each lighting condition. It was expected that under each separate lighting condition, the device would measure the various samples within a prespecified clinically significant Hb mass range (±30 g per canister). RESULTS: The limits of agreement (LOA) between the device and the reference method for dark (bias: 4.7 g [95% confidence interval {CI}, 3.8-5.6 g]; LOA: -8.1 g [95% CI, -9.7 to -6.6 g] to 17.6 g [95% CI, 16.0-19.1 g]), medium (bias: 3.4 g [95% CI, 2.6-4.1 g]; LOA: -7.4 g [95% CI, -8.7 to -6.1 g] to 14.2 g [95% CI, 12.9-15.5 g]), and bright lighting conditions (bias: 4.1 g [95% CI, 3.2-4.9 g]; LOA: -7.6 g [95% CI, -9.0 to -6.2 g] to 15.7 g [95% CI, 14.3-17.1 g]) fell well within the predetermined clinically significant limits of ±30 g. Repeated measurements of the samples under the various lighting conditions were highly correlated with intraclass correlation coefficient of 0.995 (95% CI, 0.993-0.996; P < .001), showing that lighting conditions did not have a significant impact on measurements. Hb mass bias was significantly associated with hemolysis level (Spearman ρ correlation coefficient, -0.137; P = .001) and total canister volume (Spearman ρ correlation coefficient, 0.135; P = .001), but not ambient illuminance. CONCLUSIONS: The Triton Canister System was able to measure the Hb mass reliably with clinically acceptable accuracy in reconstituted blood samples representing a wide range of Hb concentrations, dilutions, hemolysis, and ambient lighting settings.

Real-time evaluation of an image analysis system for monitoring surgical hemoglobin loss.

Monitoring blood loss is important for management of surgical patients. This study reviews a device (Triton) that uses computer analysis of a photograph to estimate hemoglobin (Hb) mass present on surgical sponges. The device essentially does what a clinician does when trying to make a visual estimation of blood loss by looking at a sponge, albeit with less subjective variation. The performance of the Triton system is reported upon in during real-time use in surgical procedures. The cumulative Hb losses estimated using the Triton system for 50 enrolled patients were compared with reference Hb measurements during the first quarter, half, three-quarters and full duration of the surgery. Additionally, the estimated blood loss (EBL) was calculated using the Triton measured Hb loss and compared with values obtained from both visual estimation and gravimetric measurements. Hb loss measured by Triton correlated with the reference method across the four measurement intervals. Bias remained low and increased from 0.1 g in the first quarter to 3.7 g at case completion. The limits of agreement remained narrow and increased proportionally from the beginning to the end of the cases, reaching a maximum range of -15.3 to 22.7 g. The median (IQR) difference of EBL derived from the Triton system, gravimetric method and visual estimation versus the reference value were 13 (74), 389 (287), and 4 (230) mL, respectively. Use of the Triton system to measure Hb loss in real-time during surgery is feasible and accurate.

Clinical evaluation of a novel system for monitoring surgical hemoglobin loss.

BACKGROUND: Accurate measurement of intraoperative blood loss is an important clinical variable in managing fluid resuscitation and avoiding unnecessary transfusion of blood products. In this study, blood lost onto laparotomy sponges during surgical cases was measured using a tablet computer programmed with a unique algorithm modeled after facial recognition technology. In this study, we assessed the accuracy and performance of the system in surgical cases. METHODS: In this prospective, multicenter study, 46 patients undergoing surgery with anticipated significant blood loss contributed laparotomy sponges for hemoglobin (Hb) loss measurement using the Triton System with Feature Extraction Technology (Gauss Surgical, Inc., Los Altos, CA). The Hb loss measured by the new system was compared with that measured by manual rinsing of the sponges. Accuracy was evaluated using linear regression and Bland-Altman analysis. In addition, the new system's calculation of blood volume loss was compared with the gravimetric method of estimating blood loss from intraoperative sponge weights. RESULTS: A significant positive linear correlation was noted between the new system's measurements and the rinsed Hb mass (r = 0.93, P < 0.0001). Bland-Altman analysis revealed a bias of 9.0 g and narrow limits of agreement (-7.5 to 25.5 g) between the new system's measures and the rinsed Hb mass. These limits were within the clinically relevant difference of ±30 g, which is approximately half of the Hb content of a unit of allogeneic whole blood. Bland-Altman analysis of the estimated blood loss on sponges using the gravimetric method demonstrated a bias of 466 mL (overestimation) with limits of agreement of -171 and 1103 mL, due to the presence of contaminants other than blood on the laparotomy sponges. CONCLUSIONS: The novel mobile monitoring system provides an accurate measurement of Hb mass on surgical sponges as compared with that of manual rinsing measurements and is significantly more accurate than the gravimetric method. Further study is warranted to assess the clinical use of the technology.

Does a delay in performing an activated clotting (ACT) test really matter? A study in nonheparinized blood and a single ACT machine.

Activating clotting time (ACT) is a point-of-care, blood clotting test used to monitor anticoagulation. Recently, institutional requirements have required that ACT testing be completed outside the operating room with trained, certified personnel other than anesthesia staff. For this reason, in this study, we looked at whether a delay in processing an ACT makes a significant difference to the ACT results. Twenty patients between 18 and 65 years of age consented to the study, each undergoing non-cardiac surgery, with no intraoperative administration of heparin. The study was approved by our Institutional Review Board. A blood sample was taken from the patient's arterial line in the operating room. Immediately afterward, 1 mL was placed into each of two ACT cartridges and the measurement was done in a Medtronic ACT2 machine. The first ACT value was 126.9 +/- 14.5 seconds. The ACT value at approximately 30 minutes was 108.3 +/- 20.3 seconds (p < .0001). The time between the first and last measurements was 29.4 +/- 3.0 minutes. The results suggest that the ACT values decrease over time between sampling all measurements. At approximately 30 minutes, the ACT values average 15% less than the control measurements. Therefore, it would seem prudent to determine ACT values immediately in the operating room without any delay, using point-of-care testing.

Ketamine does not increase pulmonary vascular resistance in children with pulmonary hypertension undergoing sevoflurane anesthesia and spontaneous ventilation.

BACKGROUND: The use of ketamine in children with increased pulmonary vascular resistance is controversial. In this prospective, open label study, we evaluated the hemodynamic responses to ketamine in children with pulmonary hypertension (mean pulmonary artery pressure >25 mm Hg). METHODS: Children aged 3 mo to 18 yr with pulmonary hypertension, who were scheduled for cardiac catheterization with general anesthesia, were studied. Patients were anesthetized with sevoflurane (1 minimum alveolar anesthetic concentration [MAC]) in air while breathing spontaneously via a facemask. After baseline catheterization measurements, sevoflurane was reduced (0.5 MAC) and ketamine (2 mg/kg IV over 5 min) was administered, followed by a ketamine infusion (10 microg x kg(-1) x min(-1)). Catheterization measurements were repeated at 5, 10, and 15 min after completion of ketamine load. Data at various time points were compared (ANOVA, P < 0.05). RESULTS: Fifteen patients (age 147, 108 mo; median, interquartile range) were studied. Diagnoses included idiopathic pulmonary arterial hypertension (5), congenital heart disease (9), and diaphragmatic hernia (1). At baseline, median (interquartile range) baseline pulmonary vascular resistance index was 11.3 (8.2) Wood units; 33% of patients had suprasystemic mean pulmonary artery pressures. Heart rate (99, 94 bpm; P = 0.016) and Pao2 (95, 104 mm Hg; P = 007) changed after ketamine administration (baseline, 15 min after ketamine; P value). There were no significant differences in mean systemic arterial blood pressure, mean pulmonary artery pressure, systemic or pulmonary vascular resistance index, cardiac index, arterial pH, or Paco2. CONCLUSIONS: In the presence of sevoflurane, ketamine did not increase pulmonary vascular resistance in spontaneously breathing children with severe pulmonary hypertension.

Prolonged infusion of dexmedetomidine for sedation following tracheal resection.

Dexmedetomidine is a centrally acting alpha-2 adrenergic agonist that is currently approved by the US Food and Drug Administration for short-term use (< or = 24 h) to provide sedation in adults in the ICU. This drug has been shown to be efficacious in adult medical and surgical patients in providing sedation, anxiolysis, and analgesia. Dexmedetomidine has been associated with rapid onset and offset, hemodynamic stability, and a natural, sleep-like state in mechanically ventilated adults. To date, there are few publications of the use of this drug in children, and prolonged infusion has not been described. We report our use of dexmedetomidine in a child during a 4-day period of mechanical ventilation following tracheal reconstruction for subglottic stenosis.