Abstract
Background: The liver is the most frequently injured abdominal organ after blunt injury; sometimes it may be very difficult to achieve haemostasis. In this study we examined the use of InLine radiofrequency ablation (RFA) for the coagulation and haemostasis of simulated liver injury. Materials and methods: Six pigs were tested in this study. We created two types of grade III to IV liver injury: peripheral and central. Then treatment with InLine RFA was compared to conventional diathermy and suture. A total of 32 surgeries were performed: peripheral injury (12 InLine versus 6 diathermy + suture); central injury (8 InLine versus 6 diathermy + suture). Results: The reduction of blood loss was 63.88% in peripheral injury and 53.57% in central injury, respectively. There were significant differences in both types of injuries as regards blood loss (p<0.05) and blood loss per cm2 (p <0.05). Conclusions: InLine RFA is efficacious in treating liver injuries in pigs and may have a significant potential for some human liver injuries.
Keywords: liver injury, InLine radiofrequency ablation (RFA), blood loss
Introduction
The liver is the most frequently injured abdominal organ after blunt trauma; stabbing and gunshot wounds can also affect the liver 1. Haemorrhage is often the major cause of death after liver injury 2. However, sometimes it may be very difficult to achieve haemostasis. Gauze packing is the most common method used to control haemorrhage in severe liver trauma 3, but some injuries cannot be controlled by packing. Liver resection is occasionally required in the trauma setting, often in a patient with deep liver lacerations involving major vessels or bile ducts 4.
We have reported that using the InLine radiofrequency (RFA) device reduces blood loss significantly in both animal experiments and clinical studies 5,6,7. The principle of the InLine RFA device is that it seals small arterial and venous vessels after deployment into the liver parenchyma; haemostasis can then be achieved. In this study we examined the use of this technology in the entirely different setting of simulated liver trauma where the injury is actively bleeding prior to an attempt at surgical control. We are not aware of previous reports of this approach.
Materials and methods
Animals
Six Landrace pigs weighing around 40–50 kg were studied. All animals received care in compliance with the ACEC Animal Usage and Monitoring Guidelines (http://www.ro.unsw.edu.au/ethics/acecmonitor.rtf). Approval for this study was obtained from the University of New South Wales Animal Ethics Committee (ACE no. 04/82). These were non-recovery experiments conducted under general anaesthesia; the animals were euthanized with a lethal injection of barbiturate after surgery.
Equipment
The InLine RFA probe consists of a linear array of six electrodes, each 4 cm long, mounted on a 5 cm long plastic base (Figure 1). The InLine probe is compatible with a range of RFA generators; we used a RITA® 1500 Generator (RITA Medical Systems, Mountain View, CA, USA). This machine generates radiofrequency current at 460 KHz with a maximum power output of 150 W. The amount of power applied depended on the depth of resection 6.
Figure 1. .
InLine RFA probe.
Anaesthesia
Induction of anaesthesia was achieved by administration of ketamine (6 mg/kg) and acepromazine (0.05 mg/kg) and pigs were intubated with a cuffed endotracheal tube using a stilette method, then anaesthesia was maintained with halothane in oxygen. A catheter was placed for vascular access in an accessible ear vein and 0.9% sodium chloride solution was administered at a rate of 10 ml/kg/h for the first hour, and then turned down to half for the remaining surgery time. Monitoring devices were attached as appropriate immediately after commencement of controlled ventilation. Operative analgesia was provided by incremental doses of methadone during the procedure. Blood pressure was maintained throughout these procedures.
Surgical procedures
We created two types of injury: peripheral (cut off the edge of one lobe) and central (cut an incision on the central part) (Figure 2). According to the Liver Injury Scale of the American Association for the Surgery of Trauma (1994 revision), peripheral injury was total parenchymal disruption involving 30% of hepatic lobe and corresponded to grade IV injury. The model of central injury was >3 cm parenchymal depth or involving 30% disruption of hepatic lobe, which corresponded to grade III to IV. Grade III and VI are generally considered severe liver injuries 8.
Figure 2. .
Simulated liver injuries.
The surgery was performed with the pigs in a supine position. After a midline incision, the liver was exposed. Using a scalpel, the edge of the liver lobe was resected, then InLine RFA (Figure 2) was deployed just 1 cm behind the incision surface, the generator was turned on and the power was applied. Sponges were used to compress the incision surface. As the coagulative ablation began, the resistance increased, and with complete coagulative ablation the generator monitor demonstrated a rise in impedance (Figures 3 and 4). The model of central injury was created by penetrating the liver more centrally. Then the InLine RFA probe was inserted into this incision; after the generator was turned on, sponges were used to squeeze liver together (Figure 5). The RFA power setting was shown onTable I. For the control studies, we used conventional diathermy and suture to control bleeding.
Figure 3. .
InLine deployment in the peripheral injury.
Figure 4. .
Coagulated peripheral incision surface.
Figure 5. .
Bleeding totally stopped after InLine treatment. Star symbols, peripheral injury; arrows, central injury.
Table I. Comparison of blood loss in InLine RFA treatment and conventional diathermy and suture.
| Animal no. | Traumatic type | Surgery | Blood loss (g) | Surface (length×depth) | Power setting/RFA time |
|---|---|---|---|---|---|
| 1 | Peripheral | ILRFA | 157 | 8×3 | 2 cm/9 min |
| ILRFA | 211 | 10×2.7 | 2 cm/10.2 min | ||
| D + S | 405 | 8×3 | |||
| Central | ILRFA | 224 | 10×3 | 2 cm/6 min + 3 cm/3 min | |
| D + S | 456 | 9×2.5 | |||
| 2 | Peripheral | ILRFA | 99 | 6×3 | 2 cm/6 min + 45 W/1.6 min |
| ILRFA | 153 | 6×2.7 | 2 cm/6 min + 3 cm/3 min | ||
| D + S | 315 | 5×3 | |||
| Central | ILRFA | 207 | 6×3 | 3 cm/3 min + 50 W/0.8 min | |
| D + S | 389 | 5×3 | |||
| 3 | Peripheral | ILRFA | 94 | 7×2.5 | 2 cm/4.4 min + 3 cm/1.7 min |
| ILRFA | 255 | 7×2.5 | 2 cm/4.1 min + 2 cm/5 min | ||
| D + S | 512 | 6×3 | |||
| Central | ILRFA | 287 | 8×3 | 2 cm/3 min + 2 cm/3 min | |
| D + S | 423 | 7×3 | |||
| 4 | Peripheral | ILRFA | 92 | 6×2.5 | 2 cm/6 min |
| ILRFA | 85 | 6×2.5 | 2 cm/7.2 min | ||
| D + S | 399 | 7×3 | |||
| Central | ILRFA | 149 | 6.5×3 | 2 cm/3 min + 2 cm/5.1 min | |
| ILRFA | 134 | 7×3 | 2 cm/3 min + 3 cm/2.8 min | ||
| D + S | 366 | 5.2×3 | |||
| 5 | Peripheral | ILRFA | 247 | 7×3 | 2 cm/4.5 min + 2 cm/4.5 min |
| ILRFA | 87 | 8×3 | 2 cm/4 min + 3 cm/3 min | ||
| D + S | 402 | 7×3 | |||
| Central | ILRFA | 214 | 6×3 | 2 cm/3 min + 3 cm/3 min | |
| D + S | 423 | 6×2.7 | |||
| 6 | Peripheral | ILRFA | 103 | 7×3 | 2 cm/6 min + 3 cm/3 min |
| ILRFA | 102 | 6.5×3 | 3 cm/4.1 min + 2 cm/6 min | ||
| D + S | 299 | 7×2.5 | |||
| Central | ILRFA | 122 | 7×3 | 2 cm/5 min + 2 cm/6.2 min | |
| ILRFA | 134 | 6×2.5 | 2 cm/6 min + 3 cm/3 min | ||
| D + S | 426 | 6×2.8 |
ILRFA, InLine RFA; D + S, diathermy + suture.
Measurement of blood loss
Blood loss was measured by determining the difference in the weights of dry sponges and blood-stained sponges after resection. The weight difference was expressed as the blood loss in grams.
Data analysis
Data analysis was performed based on the data collected prospectively from the information recorded in the standardized data sheets. All data were expressed as the mean±standard error. Student's t test was used to analyse the differences in blood loss and blood loss per cm2. A p value < 0.05 was considered to be statistically significant. The results were analysed using SPSS for Windows (Version 12.0; SPSS Inc., Chicago, IL, USA).
Results
Six pigs were tested in this study. No massive bleeding occurred and no animal died during the experiment. After surgery, pigs were euthanized immediately.
RFA power setting and time
The RFA power settings and times are shown in Table I. The InLine RFA probe deployment was set to 3 cm or 4 cm power algorithm; some deployments needed two or three applications to complete the coagulative ablation. The average total RFA time for peripheral injury was 8 min; the average total RFA time for central injury was 7 min.
Blood loss
The values for weight of blood loss and incision surface are shown in Table I. Data comparison is shown in Table II, including mean blood loss, mean surface area and mean blood loss per cm2. Six pigs underwent 32 surgeries: peripheral injury (12 InLine versus 6 diathermy + suture); central injury (8 InLine versus 6 diathermy + suture). In the treatment of peripheral injury, the data from the InLine RFA were as follows: mean blood loss was 140.41±36.16 g, mean surface area was 19.64±2.18 cm2, blood loss per cm2 was 7.21±1.81 g/cm2. For the control group: mean blood loss was 388.67±61.18 g, mean surface area was 19.42±2.56 cm2, mean blood loss per cm2 was 20.26±3.43 g/cm2. The reduction of blood loss was 63.88% in peripheral injury and 53.57% in central injury, respectively. There were highly significant differences between these two groups as regards blood loss (p < 0.05) and blood loss per cm2 (p < 0.05). In the treatment of central injury, the data from InLine RFA were: mean blood loss was 183.88±40.33 g, mean surface area was 17.56±5.11 cm2, blood loss per cm2 was 12.00±3.95 g/cm2. For the control group: mean blood loss was 413.83±25.30 g, mean surface area was 15.12±5.03 cm2, mean blood loss per cm2 was 33.37±15.19 g/cm2. There were significant differences between these two groups as regards blood loss (p<0.05) and blood loss per cm2 (p < 0.05).
Table II. Comparison of different techniques.
| Parameter | Peripheral trauma | Central trauma | ||
|---|---|---|---|---|
| No. of surgeries | 12 | 6 | 8 | 6 |
| Treatment | ILRFA | D + S | ILRFA | D + S |
| RFA time (min) | 8.3 | 7 | ||
| Mean blood loss (g) | 140.41±36.16 | 388.67±61.18 | 183.88±40.33 | 413.83±25.30 |
| p<0.001 | p<0.001 | |||
| Reduction of blood loss (%) | 63.88% | 55.57% | ||
| Mean surface (cm2) | 19.64±2.18 | 19.42±2.56 | 17.56±5.11 | 15.12±5.03 |
| Mean blood loss per cm2 (g/cm2) | 7.21±1.81 | 20.26±3.43 | 12.00±3.95 | 33.37±15.19 |
| p<0.001 | p=0.01 | |||
ILRFA, InLine RFA; D + S, diathermy + suture.
Discussion
The liver, despite protection by overlying ribs of the lower chest, is often injured in blunt trauma 9; stabbing and gunshot wounds can also affect the liver. It has been shown that conservative management of blunt hepatic trauma is safe and effective, being successful in 94% of cases 10. However, liver trauma has been the major cause of death in patients with severe abdominal injuries; the mortality of grade IV and V injuries has been estimated to range between 35% and 80% 11. Failure to control haemorrhage is the most crucial problem in managing liver injury. A number of methods have been used to control haemorrhage from major liver injuries 12,13,14, such as packing, microwave and even liver resection. The surgical technique of packing has the advantage of most commonly used methods, but it requires pack removal and introduces a foreign body with risk of sepsis and a risk of producing abdominal compartment syndrome 15. Thermal techniques of controlling liver bleeding have been attempted previously, including the use of microwave, but microwave might induce higher bile leakage and abscess formation postoperatively 16. Resection is best avoided in the acute situation because of the increased risk of operation on a hypothermic, coagulopathic and often multiply injured patient. The control of bleeding from liver injury can be technically very demanding and a surgeon with little experience of liver surgery may be faced with a very difficult and dangerous situation.
RFA is one of the methods used in the multimodal treatment of liver tumours 17; the InLine bipolar RFA probe was designed to rapidly pre-coagulate the liver parenchyma of a liver resection plane. It has achieved significant reductions in blood loss in animal models and liver resection in patients in normal, post chemotherapy, steatosis and cirrhotic livers 5,6,7. We have also shown that blood loss can be reduced in the partial resection of spleen and kidney 18,19. However, the potential use of the InLine RFA probe in trauma was novel, and the performance of the device in a freely bleeding liver injury was unknown.
In this study we examined the use of this technology for the coagulation and haemostasis of simulated liver trauma. Six pigs were used to simulate a total of 32 liver trauma injuries. This resulted in 20 simulated liver injuries which were then treated with the InLine device and 12 controls which were treated by conventional diathermy and suture. After the InLine RFA device is deployed into the liver parenchyma, it seals small arterial and venous vessels; therefore haemostasis was finally achieved with a significant reduction of blood loss (63.88% in peripheral injury and 53.57% in central injury) compared with conventional diathermy plus suture. We accept the obvious limitation of this study, i.e. that this was sharp rather than blunt injury, and we are well aware that bleeding in liver injury can be from large vessels which cannot be coagulated by this present device. However, we believe that the InLine RFA coagulator is inherently a very useful device for evaluation in certain liver injuries in man.
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