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

IN VITRO EVALUATION OF A NOVEL AUTOMATIC INTRAOPERATIVE BLOOD LOSS MONITOR

ABSTRACT

Introduction: Accurate and real-time monitoring of surgical blood loss is essential for ensuring intraoperative safety. However, there is currently no standard way to assess the amount of blood lost in patients during surgery. This study aims to evaluate the accuracy and precision of a new automatic intraoperative blood loss monitor, which can measure both free blood volume and blood content in sponges in real time. Methods: The monitor uses an integrated photoelectric probe to gauge hemoglobin levels in both free blood and blood taken from surgical sponges. These data, combined with initial hemoglobin levels, are processed using specific calculations to determine blood volume. We created 127 diverse free blood samples and 160 blood-containing sponge samples by using fresh pig blood and physiological saline. The monitor then measured these samples. We subsequently compared its measurements with actual values acquired through physical measurements, detecting both agreement and measurement errors. Repeated measurements were performed to calculate the coefficient of variation, thereby evaluating the monitor's precision. Results: The estimated blood loss percentage error of the monitor was 5.2% for free blood, -5.7% for small sponge, -6.3% for medium sponge, and -6.6% for large sponge. The coefficient of variation of free blood with different hemoglobin concentrations measured by the monitor was less than 10%. Bland-Altman analysis showed that the limits of agreement between the monitor and the reference method were all within the acceptable clinical range. Conclusion: The new automatic intraoperative blood loss monitor is an accurate and reliable device for monitoring both free blood and surgical sponge blood, and shows high performance under various clinical simulation conditions.

Real-time and accurate estimation of surgical hemoglobin loss using deep learning-based medical sponges image analysis

Real-time and accurate estimation of surgical hemoglobin (Hb) loss is essential for fluid resuscitation management and evaluation of surgical techniques. In this study, we aimed to explore a novel surgical Hb loss estimation method using deep learning-based medical sponges image analysis. Whole blood samples of pre-measured Hb concentration were collected, and normal saline was added to simulate varying levels of Hb concentration. These blood samples were distributed across blank medical sponges to generate blood-soaked sponges. Eight hundred fifty-one blood-soaked sponges representing a wide range of blood dilutions were randomly divided 7:3 into a training group (n = 595) and a testing group (n = 256). A deep learning model based on the YOLOv5 network was used as the target region extraction and detection, and the three models (Feature extraction technology, ResNet-50, and SE-ResNet50) were trained to predict surgical Hb loss. Mean absolute error (MAE), mean absolute percentage error (MAPE), coefficient (R2) value, and the Bland-Altman analysis were calculated to evaluate the predictive performance in the testing group. The deep learning model based on SE-ResNet50 could predict surgical Hb loss with the best performance (R2 = 0.99, MAE = 11.09 mg, MAPE = 8.6%) compared with other predictive models, and Bland-Altman analysis also showed a bias of 1.343 mg with narrow limits of agreement (- 29.81 to 32.5 mg) between predictive and actual Hb loss. The interactive interface was also designed to display the real-time prediction of surgical Hb loss more intuitively. Thus, it is feasible for real-time estimation of surgical Hb loss using deep learning-based medical sponges image analysis, which was helpful for clinical decisions and technical evaluation.

Emerging technology for early detection and management of postpartum hemorrhage to prevent morbidity

Despite advances in hemorrhage detection and management, postpartum hemorrhage remains the single leading cause of maternal death worldwide. Within the United States, hemorrhage is the leading cause of maternal death on the day of delivery and within the first week after delivery. Blood transfusion after hemorrhage represents a large proportion of severe maternal morbidity during and after delivery. Blood loss during delivery has historically been assessed visually by inspecting soiled pads, linens, and laparotomy sponges. These methods underestimate the volume of blood loss by as much as 40%, becoming increasingly inaccurate as blood loss increases. Young, healthy obstetrical patients compensate for blood loss via peripheral vasoconstriction, maintaining heart rate and blood pressure in a normal range until over 1 L of blood has been lost. A significant decrease in blood pressure along with marked tachycardia (>120 bpm) may not be seen until 30% to 40% of blood volume has been lost, or 2.0 to 2.6 L in a healthy term pregnant patient, after which the patient may rapidly decompensate. In resource-poor settings especially, the narrow window between the emergence of significant vital sign abnormalities and clinical decompensation may prove catastrophic. Once hemorrhage is detected, decisions regarding blood product transfusion are routinely made on the basis of inaccurate estimates of blood loss, placing patients at risk of underresuscitation (increasing the risk of hemorrhagic shock and end-organ damage) or overresuscitation (increasing the risk of transfusion reaction, fluid overload, and alloimmunization). We will review novel technologies that have emerged to assist both in the early and accurate detection of postpartum hemorrhage and in decisions regarding blood product transfusion.

The visually estimated blood volume in scaled canisters based on a simulation study

BACKGROUND

The most common technique used worldwide to quantify blood loss during an operation is the visual assessment by the attending intervention team. In every operating room you will find scaled suction canisters that collect fluids from the surgical field. This scaling is commonly used by clinicians for visual assessment of intraoperative blood loss. While many studies have been conducted to quantify and improve the inaccuracy of the visual estimation method, research has focused on the estimation of blood volume in surgical drapes. The question whether and how scaling of canisters correlates with actual blood loss and how accurately clinicians estimate blood loss in scaled canisters has not been the focus of research to date.

METHODS

A simulation study with four "bleeding" scenarios was conducted using expired whole blood donations. After diluting the blood donations with full electrolyte solution, the sample blood loss volume (SBL) was transferred into suction canisters. The study participants then had to estimate the blood loss in all four scenarios. The difference to the reference blood loss (RBL) per scenario was analyzed.

RESULTS

Fifty-three anesthetists participated in the study. The median estimated blood loss was 500 ml (IQR 300/1150) compared to the RBL median of 281.5 ml (IQR 210.0/1022.0). Overestimations up to 1233 ml were detected. Underestimations were also observed in the range of 138 ml. The visual estimate for canisters correlated moderately with RBL (Spearman's rho: 0.818; p < 0.001). Results from univariate nonparametric confirmation statistics regarding visual estimation of canisters show that the deviation of the visual estimate of blood loss is significant (z = - 10.95, p < 0.001, n = 220). Participants' experience level had no significant influence on VEBL (p = 0.402).

CONCLUSION

The discrepancies between the visual estimate of canisters and the actual blood loss are enormous despite the given scales. Therefore, we do not recommend estimating the blood loss visually in scaled suction canisters. Colorimetric blood loss estimation could be a more accurate option.

Do we visually estimate intra-operative blood loss better with white or green sponges and is the deviation from the real blood loss clinically acceptable? Results from a simulated scenario study

BACKGROUND

The intraoperative blood loss is estimated daily in the operating room and is mainly done by visual techniques. Due to local standards, the surgical sponge colours can vary (e.g. white in US, green in Germany). The influence of sponge colour on accuracy of estimation has not been in the focus of research yet.

MATERIAL AND METHODS

A blood loss simulation study containing four "bleeding" scenarios each per sponge colour were created by using expired whole blood donation samples. The blood donations were applied to white and green surgical sponges after dilution with full electrolyte solution. Study participants had to estimate the absorbed blood loss in sponges in all scenarios. The difference to the reference blood loss was analysed. Multivariate linear regression analysis was performed to investigate other influence factors such as staff experience and sponge colour.

RESULTS

A total of 53 anaesthesists participated in the study. Visual estimation correlated moderately with reference blood loss in white (Spearman's rho: 0.521; p = 3.748*10-16) and green sponges (Spearman's rho: 0.452; p = 4.683*10-12). The median visually estimated blood loss was higher in white sponges (250ml IRQ 150-412.5ml) than in green sponges (150ml IQR 100-300ml), compared to reference blood loss (103ml IQR 86-162.8). For both colour types of sponges, major under- and overestimation was observed. The multivariate statistics demonstrates that fabric colours have a significant influence on estimation (p = 3.04*10-10), as well as clinician's qualification level (p = 2.20*10-10, p = 1.54*10-08) and amount of RBL to be estimated (p < 2*10-16).

CONCLUSION

The deviation of correct blood loss estimation was smaller with white surgical sponges compared to green sponges. In general, deviations were so severe for both types of sponges, that it appears to be advisable to refrain from visually estimating blood loss whenever possible and instead to use other techniques such as e.g. colorimetric estimation.

Comparison of common perioperative blood loss estimation techniques: a systematic review and meta-analysis

Estimating intraoperative blood loss is one of the daily challenges for clinicians. Despite the knowledge of the inaccuracy of visual estimation by anaesthetists and surgeons, this is still the mainstay to estimate surgical blood loss. This review aims at highlighting the strengths and weaknesses of currently used measurement methods. A systematic review of studies on estimation of blood loss was carried out. Studies were included investigating the accuracy of techniques for quantifying blood loss in vivo and in vitro. We excluded nonhuman trials and studies using only monitoring parameters to estimate blood loss. A meta-analysis was performed to evaluate systematic measurement errors of the different methods. Only studies that were compared with a validated reference e.g. Haemoglobin extraction assay were included. 90 studies met the inclusion criteria for systematic review and were analyzed. Six studies were included in the meta-analysis, as only these were conducted with a validated reference. The mixed effect meta-analysis showed the highest correlation to the reference for colorimetric methods (0.93 95% CI 0.91–0.96), followed by gravimetric (0.77 95% CI 0.61–0.93) and finally visual methods (0.61 95% CI 0.40–0.82). The bias for estimated blood loss (ml) was lowest for colorimetric methods (57.59 95% CI 23.88–91.3) compared to the reference, followed by gravimetric (326.36 95% CI 201.65–450.86) and visual methods (456.51 95% CI 395.19–517.83). Of the many studies included, only a few were compared with a validated reference. The majority of the studies chose known imprecise procedures as the method of comparison. Colorimetric methods offer the highest degree of accuracy in blood loss estimation. Systems that use colorimetric techniques have a significant advantage in the real-time assessment of blood loss.

Quantification of Intraoperative Blood Loss in a Simulated Scenario Using a Novel Device

BACKGROUND

Particularly for protracted bleeding situations, the realization of a relevant blood loss is necessary for early initiation of therapy to avoid hemodynamic instability and shock. The frequently used visual assessment of blood loss is known to be incorrect. An innovative option to address this problem is a mobile application using colorimetric image correction and analysis.

METHODS

The objective of this study was to evaluate the clinical applicability and accuracy of a novel mobile device application using colorimetric image correction and analysis for blood loss estimation. Scenarios of blood-filled surgical sponges were created to evaluate the accuracy of colorimetric-based blood loss estimation and visual and gravimetric blood loss estimation.

RESULTS

Fifty-three anesthesiologists ran through the scenarios. The estimated blood loss correlated the least with the reference blood loss in the visual technique (Rho: 0.52; P < 3.7×10-16), followed by the gravimetric technique (Rho: 0.73; P = 2.8×10-05). The best correlation was found in the colorimetric blood loss measurement (Rho: 0.77; P = 3.53×10-06). A median overestimation per scenario of 133.0 mL (interquartile range [IQR] 33.0 mL-283.0 mL) was observed when using the visual method, whereas 32.5 mL (IQR 10.8 mL-44.0 mL) was overestimated with the gravimetric method and 31 mL (IQR 17.0 mL-42.8 mL) with the colorimetric method. Especially in the case of blood loss underestimation, the application has the least deviation from the reference.

CONCLUSION

The blood loss measured in the sponges correlated strong with the reference blood loss, showing the smallest median overestimation and the smallest deviation in underestimation. The visual estimation shows serious errors, where the gravimetric method is prone to errors, especially in dilution. The colorimetric method offers an easily implementable possibility to monitor blood loss in real time and to initiate early diagnostic and therapeutic measures in case of persistent blood loss. The influence of real-time estimation of colorimetric blood loss on transfusion decisions should be the subject of future studies.

Perioperative blood loss: estimation of blood volume loss or haemoglobin mass loss?

BACKGROUND

Perioperative blood loss is an essential parameter in research into Patient Blood Management. However, currently there is no "gold standard" method to quantify it. Direct measurements of blood loss are considered unreliable methods, and the formulae to estimate it have proven to be significantly inaccurate. Given the need for better research tools, this study evaluated an estimation of haemoglobin mass loss as an alternative approach to estimate perioperative blood loss, and compared it to estimations based on blood volume loss.

MATERIAL AND METHODS

We studied one hundred consecutive patients undergoing urological laparoscopic surgery. Both haemoglobin mass loss and blood volume loss were directly measured during surgery, under highly controlled conditions for a reliable direct measurement of blood loss. Three formulae were studied: 1) a haemoglobin mass loss formula, which estimated blood loss in terms of haemoglobin mass loss, 2) the López-Picado's formula and 3) an empirical volume formula that estimated blood loss in terms of blood volume loss. The empirical volume formula was developed within the study with the aim of providing the best possible estimation of blood volume loss in the studied population. The formulae were evaluated and compared by assessing their agreements with their respective direct measurements of blood loss.

RESULTS

The haemoglobin mass loss formula met the predefined agreement criterion of ±71 g, with 95% limits of agreement ranging from 0.6 to 44.1 g and a moderate overestimation of 22.4. In comparison to both blood volume loss formulae, the haemoglobin mass loss formula was superior in every agreement parameter evaluated.

DISCUSSION

In this study, the estimation of haemoglobin mass loss was found to be a more accurate method to estimate perioperative blood loss. This estimation method could be a robust research tool, although more studies are needed to establish its reliability.

Association between perioperative surgical home implementation and transfusion patterns in adolescents with idiopathic scoliosis undergoing spinal fusion

BACKGROUND

Blood transfusions in patients with adolescent idiopathic scoliosis after fusion have been associated with increased morbidity, mortality, and cost.

OBJECTIVE

The aim of this study was to evaluate the association between implementation of blood-conservation strategies within the perioperative surgical home on transfusion rates for patients with adolescent idiopathic scoliosis undergoing spinal fusion.

METHODS

Two hundred and thirteen patients (44 preperioperative surgical home, 169 postperioperative surgical home) who underwent posterior spine fusion for adolescent idiopathic scoliosis between 23 June 2014, and 30 July 2017, were enrolled in this case control study. The perioperative surgical home implemented in March 2015 involved evidence-based perioperative interventions to create a standardized clinical pathway including judicious use of crystalloid management, restrictive transfusion strategy, routine use of cell saver, and standardized administration of anti-fibrinolytics. The primary outcome was odds of perioperative transfusion. Secondary outcomes included volumes of crystalloid, albumin, cell saver, packed red blood cells as well as calculated blood loss. Other variables that were documented included antibrinolytic total dose, mean arterial pressure, temperature, laboratory values, intrathecal morphine dosing, and surgical time. Statistical methods included t test and logistic regression.

RESULTS

For the postperioperative surgical home, the odds of perioperative transfusion were 0.30 (95% CI 0.13-0.70), as compared to preperioperative surgical home. In terms of secondary outcomes, calculated blood loss was significantly lower in the postperioperative surgical home patients (27.0 mL/kg preperioperative surgical home vs 22.8 mL/kg postperioperative surgical home; mean difference = -0.24 [-0.44, -0.04]). Although no difference was noted in the amount of intraoperative cell saver or albumin administered, a reduction was noted in mean intraoperative crystalloid given postperioperative surgical home (41.4 mL/kg ± 20.4 mL/kg preperioperative surgical home vs 28.0 mL/kg ± 13.7 mL/kg postperioperative surgical home; log mean difference = 0.37 [95% CI 0.21-0.53], P < 0.001). Postperioperative surgical home patients also had a significantly higher temperature nadir (mean difference = -0.47 [95% CI -0.70 to -0.23]; P < 0.001), received a significantly higher total anti-fibrinolytic dose (mean difference = -3939 [95% CI -5364 to -2495]; P < 0.001), and were exposed to shorter surgical times (mean difference = 0.72 [95% CI 0.36-1.09]; P < 0.001).

CONCLUSIONS

Implementation of blood-conservation strategies as part of a perioperative surgical home for patients with adolescent idiopathic scoliosis undergoing posterior spine fusion resulted in significant decrease in perioperative blood transfusions.