Simulation of carbon dioxide insufflation via a diffuser in an open surgical wound model

Prophylactic use of incisional negative pressure wound therapy for groin incisions in vascular surgery: randomized clinical trial

BACKGROUND

The efficacy of incisional negative pressure wound therapy (iNPWT) in preventing surgical site infections (SSIs) after infrainguinal vascular surgery remains unclear. This study compared iNPWT with standard gauze dressings to determine the effects on SSI incidence and quality of life.

METHODS

Patients undergoing infrainguinal vascular surgery were recruited to a regional randomized clinical trial. All patients had a groin incision for either thromboendarterectomy only with a vein or synthetic patch or hybrid procedures with thromboendarterectomy and concurrent endovascular treatment. The control and intervention groups received sterile gauze and iNPWT dressings, respectively. The primary endpoint was the incidence of SSIs within 30 days, measured using the Additional treatment, Serous discharge, Erythema, Purulent exudates, Separation of the deep tissues, Isolation of bacteria and inpatient Stay (ASEPSIS) scoring protocol. Secondary endpoints were scores on the Wound Quality of Life and EQ-5D™ three-level (EQ-5D-3L™) questionnaires.

RESULTS

Of the 123 patients randomized, 109 (89%) completed the study. The incidence of SSI was similar in the intervention and control groups (15% versus 25%, respectively; P = 0.340), but was higher in patients with a body mass index (BMI) ≥ 25 kg/m2 than in those with a BMI < 25 kg/m2 (52% versus 21%, respectively). Wound Quality of Life mean scores were similar in the control and intervention groups (10.60 versus 12.85, respectively; P = 0.322); however, the intervention group reported a larger negative impact on everyday life than the control group (7.40 versus 4.91 for the everyday life domain, respectively; P = 0.048). There were no significant differences between the two groups in EQ-5D-3L™ scores.

CONCLUSION

The similar distribution of SSIs regardless of the type of wound dressing, in addition to the negative impact on everyday life, does not support the general use of iNPWT in this or similar patient cohorts. The unique aspect of this trial is the patient perspective on the use of iNPWT, revealing a divergence between the views of patients and healthcare providers regarding optimal wound care. In the setting of individualized care, there may be a place for iNPWT in selected patients with a high BMI and excessive perioperative bleeding, which are associated with a higher SSI risk.

REGISTRATION NUMBER

NCT03395613 (https://clinicaltrials.gov).

The Effect of Heated CO2 Insufflation in Minimising Surgical Wound Contamination During Open Surgery

The primary source of infections in open surgeries has been found to be bacteria and viruses carried into the surgical wound on the surfaces of skin particles shed by patients and surgical staff. In open cardiac surgeries, insufflation of the wound with carbon dioxide is used to limit the quantity of air able to enter into the heart, avoiding air embolisms when the heart is restarted. This surgical technique has been evaluated as a method of limiting the number of skin particles able to enter into the wound, using computational fluid dynamics (CFD) simulations and experimental testing. Spherical particles of 5.0 and 13.5 μm in diameter were used to simulate skin particles falling above a wound, travelling in air ventilation velocities of either 0.2 or 0.4 m/s, and with or without CO₂ insufflation. The CFD simulations with CO₂ included a diffuser placed in the wound and supplied with CO₂ at a rate of 10 L/min. Experimental testing was completed under similar conditions. The results of CFD simulations and experimental testing showed CO₂ insufflation can significantly limit the number of particles able to enter into the wound.

Increased visceral tissue perfusion with heated, humidified carbon dioxide insufflation during open abdominal surgery in a rodent model

Tissue perfusion during surgery is important in reducing surgical site infections and promoting healing. This study aimed to determine if insufflation of the open abdomen with heated, humidified (HH) carbon dioxide (CO2) increased visceral tissue perfusion and core body temperature during open abdominal surgery in a rodent model. Using two different rodent models of open abdominal surgery, visceral perfusion and core temperature were measured. Visceral perfusion was investigated using a repeated measures crossover experiment with rodents receiving the same sequence of two alternating treatments: exposure to ambient air (no insufflation) and insufflation with HH CO2. Core body temperature was measured using an independent experimental design with three treatment groups: ambient air, HH CO2 and cold, dry (CD) CO2. Visceral perfusion was measured by laser speckle contrast analysis (LASCA) and core body temperature was measured with a rectal thermometer. Insufflation with HH CO2 into a rodent open abdominal cavity significantly increased visceral tissue perfusion (2.4 perfusion units (PU)/min (95% CI 1.23-3.58); p<0.0001) compared with ambient air, which significantly reduced visceral blood flow (-5.20 PU/min (95% CI -6.83- -3.58); p<0.0001). Insufflation of HH CO2 into the open abdominal cavity significantly increased core body temperature (+1.15 ± 0.14°C) compared with open cavities exposed to ambient air (-0.65 ± 0.52°C; p = 0.037), or cavities insufflated with CD CO2 (-0.73 ± 0.33°C; p = 0.006). Abdominal visceral temperatures also increased with HH CO2 insufflation compared with ambient air or CD CO2, as shown by infrared thermography. This study reports for the first time the use of LASCA to measure visceral perfusion in open abdominal surgery and shows that insufflation of open abdominal cavities with HH CO2 significantly increases visceral tissue perfusion and core body temperature.

Carbon dioxide insufflation deflects airborne particles from an open surgical wound model

BACKGROUND

Surgical site infections remain a significant burden on healthcare systems and may benefit from new countermeasures.

AIM

To assess the merits of open surgical wound CO₂ insufflation via a gas diffuser to reduce airborne contamination, and to determine the distribution of CO₂ in and over a wound.

METHODS

An experimental approach with engineers and clinical researchers was employed to measure the gas flow pattern and motion of airborne particles in a model of an open surgical wound in a simulated theatre setting. Laser-illuminated flow visualizations were performed and the degree of protection was quantified by collecting and characterizing particles deposited in and outside the wound cavity.

FINDINGS

The average number of particles entering the wound with a diameter of <5μm was reduced 1000-fold with 10L/min CO₂ insufflation. Larger and heavier particles had a greater penetration potential and were reduced by a factor of 20. The degree of protection was found to be unaffected by exaggerated movements of hands in and out of the wound cavity. The steady-state CO₂ concentration within the majority of the wound cavity was >95% and diminished rapidly above the wound to an atmospheric level (∼0%) at a height of 25mm.

CONCLUSION

Airborne particles were deflected from entering the wound by the CO₂ in the cavity akin to a protective barrier. Insufflation of CO₂ may be an effective means of reducing intraoperative infection rates in open surgeries.

Intra-operative tissue oxygen tension is increased by local insufflation of humidified-warm CO2 during open abdominal surgery in a rat model

INTRODUCTION

Maintenance of high tissue oxygenation (PtO2) is recommended during surgery because PtO2 is highly predictive of surgical site infection and colonic anastomotic leakage. However, surgical site perfusion is often sub-optimal, creating an obstructive hurdle for traditional, systemically applied therapies to maintain or increase surgical site PtO2. This research tested the hypothesis that insufflation of humidified-warm CO2 into the abdominal cavity would increase sub-peritoneal PtO2 during open abdominal surgery.

MATERIALS AND METHODS

15 Wistar rats underwent laparotomy under general anesthesia. Three sets of randomized cross-over experiments were conducted in which the abdominal cavity was subjected to alternating exposure to 1) humidified-warm CO2 & ambient air; 2) humidified-warm CO2 & dry-cold CO2; and 3) dry-cold CO2 & ambient air. Sub-peritoneal PtO2 and tissue temperature were measured with a polarographic oxygen probe.

RESULTS

Upon insufflation of humidified-warm CO2, PtO2 increased by 29.8 mmHg (SD 13.3; p<0.001), or 96.6% (SD 51.9), and tissue temperature by 3.0°C (SD 1.7 p<0.001), in comparison with exposure to ambient air. Smaller, but significant, increases in PtO2 were seen in experiments 2 and 3. Tissue temperature decreased upon exposure to dry-cold CO2 compared with ambient air (-1.4°C, SD 0.5, p = 0.001).

CONCLUSIONS

In a rat model, insufflation of humidified-warm CO2 into the abdominal cavity during open abdominal surgery causes an immediate and potentially clinically significant increase in PtO2. The effect is an additive result of the delivery of CO2 and avoidance of evaporative cooling via the delivery of the CO2 gas humidified at body temperature.