Study on Crystalloid Volume versus Catecholamine Strategies for Managing Hemorrhagic Shock during Esophagectomy

Academic Background

Esophageal cancer is a common malignant tumor worldwide, and surgical resection is one of the primary treatment methods. However, esophagectomy is a complex procedure involving two body cavities (thoracic and abdominal), with a high risk of complications and mortality. Intraoperative hemorrhage is a common and severe complication during esophagectomy, particularly in anatomically complex regions (e.g., near the azygos vein), which may lead to massive bleeding. Currently, there is no consensus on the ideal anesthetic management strategy for intraoperative hemorrhage, especially regarding how to maintain microcirculatory perfusion and tissue oxygenation of the gastric conduit.

The gastric conduit is a critical structure for digestive tract reconstruction in esophagectomy, and its poor perfusion may lead to anastomotic leakage, one of the most severe complications after esophageal surgery, significantly increasing patient mortality. Therefore, how to quickly and effectively restore microcirculatory perfusion and tissue oxygenation of the gastric conduit during intraoperative hemorrhage is a key issue in improving surgical outcomes. This study aims to evaluate the effects of different anesthetic management strategies on tissue oxygenation of the gastric conduit using hyperspectral imaging (HSI), providing scientific evidence for managing intraoperative hemorrhage.

Source of the Paper

This paper was co-authored by Alexander Studier-Fischer, Berkin Özdemir, and other scholars from Heidelberg University Hospital, the German Cancer Research Center (DKFZ), and other institutions. The paper was published online on July 8, 2024, in the International Journal of Surgery, titled Crystalloid volume versus catecholamines for management of hemorrhagic shock during esophagectomy: assessment of microcirculatory tissue oxygenation of the gastric conduit in a porcine model using hyperspectral imaging – an experimental study.

Research Process

1. Study Design and Animal Model

This study utilized an established porcine model to simulate gastric conduit formation and intraoperative hemorrhage during esophagectomy. A total of 32 pigs with an average weight of 35.1 kg were used. The pigs were randomly divided into four groups, with eight pigs in each group, receiving different anesthetic management strategies: - Group I: Permissive hypotension, i.e., no additional hemodynamic intervention. - Group II: Catecholamine therapy using noradrenaline. - Group III: Crystalloid volume supplementation. - Group IV: Combined crystalloid volume supplementation and noradrenaline therapy.

2. Surgical Procedure and Hemorrhage Simulation

All pigs underwent a standardized surgical procedure, including laparotomy, gastric conduit construction, and simulation of a linear stapler application. After surgery, approximately 500 ml of blood was drawn through a central venous catheter to simulate intraoperative hemorrhage, reducing the mean arterial pressure (MAP) to 40±5 mmHg and maintaining it for 60 minutes.

3. Hyperspectral Imaging and Data Collection

Hyperspectral imaging (HSI) was used to assess tissue oxygenation (StO2) of the gastric conduit. The HSI system (TIVITA Tissue Halogen System) provided spectral resolution in the range of 500 to 995 nm, quantifying tissue oxygenation levels by calculating the hyperspectral oxygenation index (StO2). Data collection time points included: - T0: Before laparotomy. - T1: After laparotomy (divided into T1a: before gastric conduit construction; T1b: after gastric conduit construction; T1c: after simulated stapler application). - T2: 60 minutes after hemorrhage. - T3: 60 minutes after intervention. - T4: 120 minutes after intervention.

4. Hemodynamic Monitoring and Data Analysis

The study also monitored hemodynamic parameters such as heart rate, mean arterial pressure, hemoglobin concentration, and venous carbon dioxide partial pressure (pCO2), and validated the reliability of StO2 using systemic lactate levels. Data analysis was performed using Python and GraphPad Prism software, with statistical methods including one-way ANOVA and principal component analysis (PCA).

Main Results

1. Changes in Gastric Conduit Tissue Oxygenation

HSI results showed that StO2 values of the gastric conduit significantly decreased in all groups after hemorrhage (T2) but exhibited significant differences after intervention (T4): - Group I (Permissive hypotension): StO2 of 63.3% ± 7.6%. - Group II (Catecholamine therapy): StO2 of 45.9% ± 6.4%. - Group III (Crystalloid volume supplementation): StO2 of 70.5% ± 6.1%. - Group IV (Combined therapy): StO2 of 69.0% ± 3.7%.

2. Hemodynamic Parameters

The crystalloid volume supplementation group (Group III) exhibited hemodynamic parameters closer to physiological states after intervention, such as lower heart rate (80.5 beats/min) and higher mean arterial pressure (57.8 mmHg). In contrast, the catecholamine therapy group (Group II) showed significantly increased heart rate (192.3 beats/min) and lower mean arterial pressure (34.8 mmHg).

3. Correlation Between Systemic Lactate and StO2

StO2 values were significantly negatively correlated with systemic lactate levels (r = -0.67), indicating that StO2 is an effective indicator for assessing tissue perfusion. Lactate levels in the crystalloid volume supplementation group significantly decreased after intervention (2.0 mmol/L), while those in the catecholamine therapy group significantly increased (6.9 mmol/L).

Conclusions and Significance

This study demonstrates that crystalloid volume supplementation (Group III) performs best in restoring gastric conduit tissue oxygenation and reducing systemic lactate levels, making it the preferred strategy for managing hemorrhagic shock during esophagectomy. In contrast, the use of catecholamines alone (Group II) may further worsen gastric conduit perfusion and increase the risk of tissue hypoxia. Hyperspectral imaging provides a new tool for intraoperative microcirculatory monitoring, enabling real-time assessment of tissue oxygenation and offering critical support for anesthetic management and surgical decision-making.

Research Highlights

1. Application of Hyperspectral Imaging: This study is the first to apply hyperspectral imaging to assess gastric conduit perfusion during esophagectomy, providing a new method for microcirculatory monitoring.
2. Superiority of Crystalloid Volume Supplementation: The study confirms that crystalloid volume supplementation outperforms catecholamine therapy alone in restoring tissue oxygenation and improving hemodynamics.
3. Clinical Translation Potential: The results are highly consistent with human data, indicating the high clinical translation value of this porcine model.

Additional Valuable Information

This study also demonstrates the potential clinical applications of hyperspectral imaging, such as intraoperative identification of gastric conduit malperfusion (e.g., hypoxic regions due to arterial compression). Furthermore, the study proposes future research directions, including exploring the effects of other fluid resuscitation strategies (e.g., hydroxyethyl starch or blood transfusion) on gastric conduit perfusion.

Through this study, scientists have provided new insights into managing hemorrhagic shock during esophagectomy and laid a scientific foundation for improving patient outcomes.