Pressure Drainage Research Articles

Advances and perspective on animal models and hydrogel biomaterials for diabetic wound healing.

Diabetic wounds are a common complication in diabetes patients. Due to peripheral nerve damage and vascular dysfunction, diabetic wounds are prone to progress to local ulcers, wound gangrene and even to require amputation, bringing huge psychological and economic burdens to patients. However, the current treatment methods for diabetic wounds mainly include wound accessories, negative pressure drainage, skin grafting and surgery; there is still no ideal treatment to promote diabetic wound healing at present. Appropriate animal models can simulate the physiological mechanism of diabetic wounds, providing a basis for translational research in treating diabetic wound healing. Although there are no animal models that can fully mimic the pathophysiological mechanisms of diabetic wounds in humans, it is vital to explore animal simulation models used in basic research and preclinical studies of diabetic wounds. In addition, hydrogel materials are regarded as a promising treatment for diabetic wounds because of their good antimicrobial activity, biocompatibility, biodegradation and appropriate mechanical properties. Herein, we review and discuss the different animal models used to investigate the pathological mechanisms of diabetic wounds. We further discuss the promising future application of hydrogel biomaterials in diabetic wound healing.

Prevention and Control of Spontaneous Combustion of Residual Coals in Acid‐Soaked Goaf in Gas Drainage Condition

With the increase of mine mining intensity, the scope of goaf continues to expand, a large amount of coal remains in goaf, and the spontaneous combustion fire of coal is particularly serious. In addition, the spontaneous combustion of coal under the condition of gas mining is not clear. At once, spontaneous combustion can induce gas explosion, resulting in the waste of manpower and material resources, bringing hidden dangers to the mine safety production. In order to prevent and control the fire caused by spontaneous combustion of left coal under the condition of gas mining, in this paper by means of laboratory test, field measurement, and numerical simulation, the law of spontaneous combustion of residual coal under gas mining is studied. The index gas of coal spontaneous combustion was determined by temperature‐programmed experimental device. Secondly, the distribution of the stope working face, goaf, and O2 is discussed. It is of great significance to study the spontaneous combustion rule of three belts in goaf under acid leaching condition and then to discuss the best position of injection idling opening and put forward targeted precontrol measures, which is of great significance to guarantee the safety of mine production. The results show that CO begins to appear when the temperature rises to 40 °C, and its concentration increases exponentially with the increase of coal temperature, which can reflect the degree of coal oxidation in goaf. Therefore, CO should be selected as the indicator gas in the working face. Under the influence of negative drainage pressure, the dangerous area will be enlarged. The optimal drainage volume of high drainage roadway is 90 m3/min, and the optimal air intake volume of working face is 1400 m3/min. The area 0–34 m away from the working face is scattered zone, 34–135 m away is spontaneous combustion zone, and 135 m away is asphyxiation zone. When the position of the idler is 50 m behind the working face, the reduction of the oxidation zone is the largest.

Clinical effects of transplantation of turbocharged bipedicle deep inferior epigastric perforator flap in breast reconstruction

Objective: To explore the clinical effects of transplantation of turbocharged bipedicle deep inferior epigastric perforator (DIEP) flap in breast reconstruction. Methods: A retrospective observational study was used. From December 2008 to December 2016, 24 patients who met the inclusion criteria were treated in the Department of Plastic Surgery of Hunan Cancer Hospital, all patients were female, aged 28-51 (36.5±1.6) years. All cases received turbocharged bipedicle DIEP flap for two-staged breast reconstruction. According to the patterns of turbocharged vessels anastomosis, the turbocharged bipedicle DIEP flaps with length of (27.5±0.3) cm and width of (12.8±1.4) cm, were divided into three types: distal end of pedicle anastomosis type, main branch of pedicle anastomosis type, and muscular branch of pedicle anastomosis type. After complete hemostasis in the donor region, the anterior sheath was repaired with intermittent suture, and umbilical reconstruction was completed. Two negative pressure drainage tubes were indwelled, and subcutaneous tissue and skin were sutured layer by layer. The specific ways of vascular anastomosis of the flap pedicle with the internal thoracic vessels of recipient site included anastomosing the proximal end of one artery and one vein, anastomosing the proximal and distal end of one artery and one vein, and anastomosing the proximal end of one artery and two veins. Postoperatively, the survival and blood supply of flaps were observed. The patients were followed up to observe the reconstructed breast shape satisfaction, donor site complications, abdominal wall function, and scar hyperplasia. Results: All turbocharged bipedicle DIEP flaps for two-staged breast reconstruction survived well, with good blood supply. During follow-up for 14 to 56 (20±6) months, the shape of reconstructed breasts was satisfied. Only linear scar was left in the donor sites of abdomen with no complications, and the function of abdominal wall was not affected. Conclusions: For patients with clear indications, transplantation of free turbocharged bipedicle DIEP flap is a safe, reliable, and satisfactory choice for breast reconstruction with autologous tissue.

Negative pressure drainage relieves respiratory discomfort for patients with medical face masks under ocular surgeries during COVID-19

Negative pressure drainage relieves respiratory discomfort for patients with medical face masks under ocular surgeries during COVID-19

External Negative Pressure Drainage of the Pancreatic Duct in Pancreatogastrostomy Following Pylorus-Preserving Pancreaticoduodenectomy-Feasibility and Technique.

Background: Postoperative pancreatic fistula (POPF) is a major cause of morbidity after pancreaticoduodenectomy. There is no consensus on the best technique to protect the pancreato-enteric anastomosis and reduce the rate of POPF. This study investigated the feasibility and efficiency of external suction drainage of the pancreatic duct to improve the healing of pancreaticogastrostomy.Methods: Between July 2019 and June 2021, 21 consecutive patients undergoing elective pancreaticoduodenectomy were included. In all patients we performed a pancreaticogastrostomy and inserted a negative pressure drainage into the pancreatic duct. The length and diameter of the pancreatic duct were measured and the texture of the pancreas was evaluated. The daily secretion volume and the lipase value via pancreatic duct drainage were documented. The occurrence of POPF was evaluated.Results: None of the patients had drainage-related complications. In 4 patients we registered a dislocation of the drainage from the pancreas duct into the stomach. 17/21 Patients showed no signs of POPF. A biochemical leak was measured in one patient. Furthermore, 2 patients had a POPF grade B. In one patient, POPF grade C required reoperation and resection of the remnant pancreas. All 4 cases of POPF met the risk criteria soft pancreas, high volume and high lipase value in the duct drainage.Conclusion: The insertion of the pancreatic duct drainage was feasible and caused no drainage-related morbidity. POPF-rate was moderate in the risk population of soft pancreas and small duct.

Proposal of a new classification: "sealed type" postinfarction left ventricular free wall rupture.

Postinfarction leftventricular free wall rupture (FWR) has been classified into blow-out type and oozing type. However, considering past papers, oozing type included the cases in which the bleeding had spontaneously stopped or sealed, and the distinction between blow-out type and oozing type was not always clear. We classified FWR into the BO type (combination of blow-out type and oozing type) with continuous bleeding and sealed type and clarified the pathophysiology of the sealed type. Thirty-five patients who underwent surgical treatment for FWR during the past 21years were retrospectively evaluated. Twenty-one patients (60%) were sealed. Comparing the sealed type with the BO type, the incidence of sudden collapse with acute onset was significantly lower (sealed type; 62%, BO type; 100%, P = 0.0118), and there were more cases of transport from outside the hospital (76%, 43%, P = 0.0453). Significantly few cases had electro-mechanical dissociation immediately before surgery (10%, 71%, P = 0.0001). In the sealed type, median sternotomy was performed in 9 patients (43%), and subxiphoid drainage was performed in 12 (57%). Fifteen patients (71%) were supported by IABP postoperatively, and re-rupture occurred in 3 patients without IABP. Long-term outcomes were significantly better in the sealed type than in the BO type. Sixty percent of postinfarction ventricular free wall rupture was the sealed type. Median sternotomy and sutureless repair with postoperative IABP support were reliable treatments. Subxiphoid drainage and strict blood pressure control with IABP may be acceptable surgical strategies in elderly, frail patients.

The Efficacy of Pyogenic Cavity Aerobic Therapy with Negative Pressure Drainage in the Treatment of Deep Neck Space Infections.

ObjectiveTo determine the effectiveness of pyogenic cavity aerobic therapy with negative pressure drainage in the treatment of deep neck space infections (DNSI).MethodsThe study was a prospective, observational analysis of 36 cases of DNSI at a tertiary care center. The patients were divided into two groups according to the treatment method. Group A was treated with pyogenic cavity aerobic therapy with negative pressure drainage and included 13 patients (6 males and 7 females), while group B was treated with traditional incision debridement drainage and included 23 patients (12 males and 11 females). The average hospitalization days and doctors’ workload (ie, average days of postoperative dressing changes) were analyzed and compared between the two groups.ResultsThe mean hospitalization days in the traditional dressing group were 26.74 ± 3.39 days, while the average days of postoperative dressing change were 25.91 ± 3.43 days. In contrast, the averages for hospitalization days and days of postoperative dressing changes in the pyogenic cavity aerobic therapy plus negative pressure drainage were 11.08 ± 2.11 and 3.69 ± 0.21 days, respectively. All 36 patients were cured. Compared with the group B, group A had a shorter hospital stays and lower doctor workloads (P < 0.001).ConclusionPyogenic cavity aerobic therapy is an effective and simple method for changing dressings after DNSI. This therapy, when combined with negative pressure drainage, shortens hospitalization days and days that require a dressing change. This has reduced the workload of clinical doctors and pain experienced by patients. This therapy also has a high degree of safety and a very satisfactory curative effect.

Usefulness of Closed Negative Pressure Drainage for Deep Neck Abscesses

Usefulness of Closed Negative Pressure Drainage for Deep Neck Abscesses

Application and Analysis of Continuous Negative Pressure Drainage Technology in Nursing of Patients with Severe Limb Trauma

Application and Analysis of Continuous Negative Pressure Drainage Technology in Nursing of Patients with Severe Limb Trauma

A Thermodynamic Analysis of the Impact of Temperature on the Capillary Pressure in Porous Media

AbstractA thermodynamic analysis of the capillary drainage, imbibition and hysteresis pressure in two‐phase porous media systems at different temperatures has been performed. Expressions for the work required or gained when the fluid saturations change, proportional to the capillary pressures, are presented. The expressions are determined using the criterion that changes in Helmholtz free energy equals zero at equilibrium. From these expressions, the variation of capillary drainage, imbibition and hysteresis pressures for increasing temperature are determined without calculating the actual capillary pressure values. The temperature dependency results show that the capillary drainage pressure declines with a fractional rate for increasing temperature with contribution from two terms, the air‐water interfacial tension and the entropy term, which give a total fractional reduction of −0.0082 K−1, close to the value −0.0084 K−1 found experimentally. The capillary imbibition pressure increases with a total fractional rate versus temperature equal +0.004 K−1 in line with the observation that water tables in soils are lifted upon day‐time heating. The total fractional temperature variation of the hysteresis capillary pressure term declines with a rate of −0.0143 K−1 for increasing temperature in qualitative agreement with experimental data. The results support the hypothesis that the thermodynamic approach applied under given assumptions can account for the major effects determining the temperature dependency of two‐phase capillary pressure in porous media. Furthermore, the entropy term adds an additional hysteresis term to the conventional term, even under isothermal conditions. The capillary pressure hysteresis phenomenon is therefore caused by two effects: Differences in interfacial areas including contact angle hysteresis plus the entropic contribution.

Brachial muscle injury resulting in acute compartment syndrome of the upper arm: a case report and literature review

BackgroundAcute compartment syndrome (ACS) is a potentially devastating condition. ACS is rare in the upper arm.Case presentationWe report a case of acute compartment syndrome of the anterior compartment of the upper arm due to brachial muscle injury. The patient experienced abnormal progressive swelling and pain in his right upper arm, and passive pulling pain of the right wrist and right hand. It was highly suspected to be right upper arm compartment syndrome, and was confirmed by surgery. The patient transferred to the emergency operating room for fasciotomy that was performed under general anesthesia using the anterolateral approach. The brachial muscle was found to be heavily swollen and had the greatest tension. The brachial muscle fibers were split lengthwise, and a large amount of hematoma was cleared. The brachial muscles were injured and partly ruptured. After full decompression, a negative pressure drainage device was used to cover the wound in the first stage. Ten days after injury, the swelling of the affected limb subsided and the wound was sutured. The patient’s limbs completely recovered to normal. The shoulder and elbow joints could move freely and the patient resumed normal farming work ability.ConclusionClinicians should fully recognize the fact that acute compartment syndrome can occur in the upper arm, rather than only the forearm and leg, and therefore avoid serious consequences caused by missed diagnosis and misdiagnosis.

Carboxyhemoglobin Elevation, a Marker for Hemolysis, Is Common in Veno-venous Extracorporeal Membrane Oxygenation.

To the Editor: Giani et al.1 found low levels of carboxyhemoglobin (COHb) in a cohort of patients supported on veno-venous extracorporeal membrane oxygenation (VV ECMO) at their center. It is noteworthy that even on ECMO support, COHb values were below average levels found in general intensive care unit population (1.3–1.9%) without extracorporeal support.2 Moreover, in observational studies of VV ECMO, severe hemolysis occurs between 10% and 23%.3,4 Thus, as a surrogate for hemolysis, one would expect COHb levels to be higher during VV ECMO support. Hence, we speculate if their experience is generalizable. We are in agreement with Giani et al. that excessive negative drainage pressures from high-blood flow rates can lead to elevated COHb. At our institution, an inline compliant bladder on the venous drainage cannula allows noninvasive monitoring and volume displacement to reduce cavitation.5 Additionally, we favor fewer circuit connections to reduce clotting at junctions. However, we would like to add a few additional points that may explain differences between our cohorts. First, 25% of our VV ECMO cohort were supported by single site double lumen cannula. The mobile membrane and smaller effective luminal radius may increase hemolysis at comparable flow rates. In our cohort, this group had the most frequent and highest levels of COHb. Second, our baseline rate of COHb before initiation of ECMO was nearly fourfold higher. Likely, there are other unaccounted factors beyond extracorporeal support that are contributing to elevated COHb in our patients. Finally, hypovolemia, vasodilation, and cannula position also contribute to excessive negative pressures.6 In our retrospective cohort, we were unable to capture the details of these potential causes. Thus, we believe that COHb elevation is a prevalent phenomenon in patients supported on VV ECMO. Causes include but are not limited to excessive negative pressure and high-blood flow.

Modified tibial transverse transport technique for the treatment of ischemic diabetic foot ulcer in patients with type 2 diabetes.

BackgroundIschemic diabetic foot ulcer is one of the terminal complications of diabetes. The high amputation rate, recurrence rate, and treatment cost have caused a huge burden on patients and society. This study designed the modified tibial transverse transport (mTTT) technology to treat diabetic ischemic diabetic foot ulcers in patients with type 2 diabetes and investigated the effectiveness and safety of this technique.MethodsThis was a retrospective analysis of patients with type 2 diabetes and ischemic diabetic foot ulcers at two hospitals during January 2016–October 2019. These patients underwent mTTT surgery combined with wound debridement and vacuum sealing drainage negative pressure drainage treatment. In-hospital follow-up was performed at 1 month after the operation, while outpatient follow-up was performed at 3, 6, and 12 months after the operation. The ulcer healing time, recurrence rate, major amputation rate, and complications were analysed.ResultsA total of 201 patients were enrolled in this study, including 107 males and 94 females (mean age: 68.3 ​± ​7.1 years). The wounds of all patients healed completely (mean healing time: 4.6 ​± ​1.6 months). There was no occurrence of major amputation, recurrence, and treatment-related complications in the patients.ConclusionmTTT can effectively and safely treat ischemic diabetic foot ulcers in patients with type 2 diabetes. This technology is an important part of the ischemic diabetic foot ulcer treatment system and warrants further research.The Translational Potential of this ArticleThis study introduced a new method to treat the ischemic diabetic foot ulcer which was called modified tibial transverse transport. The promising outcomes of patients indicated that this surgical method had great potential for clinical application and was worthy of further clinical research with high evidence level.

Prediction Model for Spontaneous Combustion of Coal around Boreholes Using Bedding Gas Drainage

To accurately and reliably predict the time of spontaneous combustion of fractured coal around a borehole induced by gas drainage along the seam, this study performed an orthogonal test taking the No. 10 Coal Mine of Pingdingshan as the research object, in terms of the suction negative pressure and coal seam buried depth. COMSOL Multiphysics was used to model the orthogonal test results, and a multielement statistical analysis of four factors and their relationships with the spontaneous combustion of coal around the borehole and a single-factor analysis in line with the site conditions were performed on the modeling results through multiple regression. The results showed a nonlinear regression relationship between the sealing hole length, sealing hole depth, negative pressure, and coal seam depth and the spontaneous combustion of the coal around the gas drainage borehole; the prediction regression model is significant. Taking the field gas drainage in the No. 10 Coal Mine of Pingdingshan as an example, the relationship between the time of spontaneous combustion of gas drainage and the drainage pressure follows a power of two. When the drainage negative pressure is less than 45 kPa, the coal around the borehole is more likely to undergo spontaneous combustion with increasing pressure, and the sealing hole length has a positive linear correlation with the time of spontaneous combustion of the coal around the borehole. When the sealing hole length is 23 m, the time of spontaneous combustion of the coal around the gas drainage hole is &gt;500 days, and the coal around the borehole does not easily undergo spontaneous combustion. When the sealing depth is 15 m, the time of spontaneous combustion of the coal around the gas drainage hole is 76 days, which is most likely to cause spontaneous combustion.

A comparative study of subcutaneous negative pressure versus simple closure of skin incision following surgery for hollow viscus perforation

Background: Surgical site infection (SSI) is a significant problem associated with open abdominal surgery resulting in increased morbidity, mortality, and cost of treatment. Surgical site infection is one of the most common post-operative complications, occurring in at least 5% of all patients undergoing surgery and 30-40% of patients undergoing abdominal surgery, depending on the level of contamination. This study compares the subcutaneous single closed suction drain and simple conventional closure of skin incision in emergency laparotomy for hollow viscus perforation.Aim: The aim of the study is to determine whether the insertion of a subcutaneous closed suction drain at the incisional site reduces the incidence of post-operative surgical site infection in emergency laparotomy for hollow viscus perforation.Methodology: This is a prospective study. Fifty patients was enrolled, Patients diagnosed to have acute abdomen clinically and radiologically were planned for emergency exploratory laparotomy. They were further allocated alternately to Group I with subcutaneous closed suction drain and Group II without drain. All the patients underwent laparotomy. Postoperatively wound complications and hospital stay was recorded.Conclusion: Our study shows that subcutaneous negative pressure drainage significantly reduces the post- operative surgical site infection and duration of hospital stay following surgery for hollow viscus perforation. This helps in early recovery, better wound healing, and decreases the financial burden on patients by decreasing hospital stay and infection. As post-operative complications depend on the level of contamination, we recommend use of closed negative pressure subcutaneous drain in all patients with contaminated or dirty wounds.

Continuous Negative Pressure Drainage with Intermittent Irrigation Leaded to a Risk Reduction of Perineal Surgical Site Infection Following Laparoscopic Extralevator Abdominoperineal Excision for Low Rectal Cancer.

PurposeHigh rate of perineal surgical site infection (SSI) is the most common complication following abdominoperineal resection (APR), especially for extralevator abdominoperineal excision (ELAPE). The purpose of this study was to investigate the effect of continuous negative pressure drainage combined with intermittent irrigation (CNPDCII) in the presacral space on the perineal SSI following laparoscopic ELAPE for low rectal cancer.Patients and MethodsThe clinical data of 99 patients with low rectal cancer who underwent laparoscopic ELAPE surgery were retrospectively analyzed. Among the 99 patients, 46 patients received CNPDCII and 53 patients received conventional drainage in the presacral space after ELAPE. Self-made irrigation drainage tube: took a silicone drainage tube, cut 3 side holes at every 2cm intervals at the front end, and fixed a flexible tube of an intravenous needle at the front end of the silicone drainage tube. The conventional drainage tube or self-made irrigation drainage tube was placed in the presacral space and poked out from the inside of the ischial tuberosity. The incidence of SSI and other perioperative indicators between the two groups was compared within 30 days after surgery.ResultsThere was no statistical difference in clinicopathological features between the two groups of patients (p>0.05). A statistically lower rate of SSI was found in CNPDCII group (17.4%, 8/46) than the conventional drainage group (35.8%, 19/53). The drainage tube retention time (7.8±1.2 d VS 9.4±1.6 d) and the postoperative hospital stay (9.7±1.4 d VS 11.9±2.3 d) in CNPDCII group were significantly shortened than the conventional drainage group. There was no statistical difference in operating theatre time and intraoperative blood loss between the two groups. Multivariate analysis confirmed that CNPDCII was an independent protective factor for SSI after ELAPE.ConclusionCNPDCII can effectively reduce the incidence of SSI following laparoscopic ELAPE, which is simple, safe and effective.

Clinical application of negative-pressure wound therapy in uncomplicated cardiac pacemaker pocket infection

Objective: To investigate the feasibility of negative-pressure wound therapy (NPWT) in the treatment of uncomplicated cardiac pacemaker pocket infection. Methods: From January 2013 to March 2020, 35 patients with uncomplicated cardiac pacemaker pocket infection were admitted to the Department of Cardiology of Peking University First Hospital, including 21 males and 14 females, aged 27 to 84 years. The retrospective cohort study was conducted. After a complete debridement followed by continuous NPWT (with negative pressure of -16.67 kPa), the pulse-generator was inserted into the new pocket between the musculus pectoralis major and pectoralis minor. Pressure drainage tube was put into the old pocket space. NPWT with the same mode was used again for 5 to 7 days after the wound was closed. The removed pocket tissue of patients was observed with hematoxylin-eosin staining. The wound healing on 10 to 12 days after the operation of pacemaker replacement was observed, and the recurrence of infection was observed during 6 to 42 months follow-up after operation. Results: The fibrous sac wall was observed in pocket tissue of the patients, and the tissue was partially covered with stratified epithelium, with many chronic inflammatory cells infiltration. Multinucleated giant cell reaction was observed in the tissue of some patients. Ten to twelve days after the operation of pacemaker replacement, 35 patients had good wound healing, and sutures were removed. After 6 to 42 months follow-up after operation, 31 patients were cured with no recurrence of infection and the wounds were well-healed; 4 patients who had recurrent infection received whole system of pacemaker removal after the operation. Conclusions: On the premise of complete debridement, NPWT is an alternative treatment for patients with uncomplicated cardiac pacemaker pocket infection.

Recombinant human epidermal growth factor combined with vacuum sealing drainage for wound healing in Bama pigs

BackgroundVacuum sealing drainage (VSD) and epidermal growth factor (EGF) both play an important role in the treatment of wounds. This study aims to explore the effects of the combination of VSD and EGF on wound healing and the optimal concentration and time of EGF.MethodsWe tested the proliferation and migration capacity of HaCaT and L929 cells at different EGF concentrations (0, 1, 5, 10, and 100 ng/ml) and different EGF action times (2, 10, and 30 min). A full-thickness skin defect model was established using male, 30-week-old Bama pigs. The experiment included groups as follows: routine dressing change after covering with sterile auxiliary material (Control), continuous negative pressure drainage of the wound (VSD), continuous negative pressure drainage of the wound and injection of EGF 10 min followed by removal by continuous lavage (V + E 10 min), and continuous negative pressure drainage of the wound and injection of EGF 30 min followed by removal by continuous lavage (V + E 30 min). The wound healing rate, histological repair effect and collagen deposition were compared among the four groups.ResultsAn EGF concentration of 10 ng/ml and an action time of 10 min had optimal effects on the proliferation and migration capacities of HaCaT and L929 cells. The drug dispersion effect was better than drug infusion after bolus injection effect, and the contact surface was wider. Compared with other groups, the V + E 10 min group promoted wound healing to the greatest extent and obtained the best histological score.ConclusionsA recombinant human epidermal growth factor (rhEGF) concentration of 10 ng/ml can promote the proliferation and migration of epithelial cells and fibroblasts to the greatest extent in vitro. VSD combined with rhEGF kept in place for 10 min and then washed, can promote wound healing better than the other treatments in vivo.

Bladder Agenesis and Bilateral Ectopic Ureters in an Infant Male With Cystic Renal Dysplasia, Imperforate Anus, and Penoscrotal Transposition

Bladder agenesis is a rare congenital anomaly infrequently reported in the literature, with an incidence of 1/600,000 patients.1 Commonly associated with other fatal malformations, the condition is often incompatible with life.2 Prior reports estimate that over 90% of living children born with this malformation are female, owing to renal preservation resulting from low pressure drainage of urine into the vagina, uterus, and vestibule.3,4 Herein we report a rare case of an infant male born with penoscrotal transposition and end stage renal disease secondary to bilateral cystic renal dysplasia found to have concurrent bladder agenesis and bilateral ureteral ectopia.

Carboxyhemglobin and Drainage Pressure During Venovenous Extracorporeal Membrane Oxygenation.

To the Editor: We read with interest the article1 recently published by Nisar et al. on ASAIO Journal. The authors describe the frequent development of carboxyhemoglobinemia in patients treated with venovenous (V-V) extracorporeal membrane oxygenation (ECMO). As highlighted in the article, high carboxyhemoglobin levels cause significant discrepancies between pulse oximetry and actual oxyhemoglobin levels. This may lead to erroneous interpretation of patient oxygenation when the latter is assessed noninvasively. Carboxyhemoglobinemia has been described since 19492 as a marker for hemolysis. Hemolysis during V-V ECMO occurs in up to 18% of patients.3 The principal causes of mechanical hemolysis during ECMO support include circuit components (oxygenator, pump,4 cannula size) as well as patient’s characteristics.5 Centrifugal pump could be a major source of hemolysis when rotating in unsuitable conditions. High rotation speed (e.g., >3000 rpm) may result in high negative pressures at the pump head, thus promoting hydrodynamic cavitation and a high level of hemolysis.6 We performed a retrospective analysis of prospectively collected data of our historical cohort of acute respiratory distress syndrome patients treated with V-V ECMO, to compare our findings with Nisar et al. We included adult patients admitted to our ECMO unit (Rianimazione Generale, ASST Monza, Italy) between 2014 and 2020. We excluded patients with veno-venoarterial ECMO and COVID-19 patients, who may present coagulopathy as a part of the underlying disease.7 Arterial blood gas (ABG) analysis was performed with the RAPIDPoint 500e System (Siemens Healthcare, Erlangen, Germany). Elevated carboxyhemoglobin was defined according to the authors’ threshold (i.e., >3%).1 Eighty-four patients (39% females, 53 ± 10 years) were included in our analysis. ECMO configuration was femoro-femoral (86% of patients) or femoro-jugular. Median duration of ECMO support was 20 days, ranging from 3 to 83 days. Average blow flow was 3.5 ± 0.5 (2,520 ± 287 rpm), whereas mean drainage pressure was −42 ± 14 mm Hg. Overall, mean carboxyhemoglobin level was 1.1 ± 0.8%. Carboxyhemoglobin level at ECMO connection was 0.6 ± 0.5%%, and its average increase was 0.011% for each ECMO day. Among 1,653 ABG analyses, carboxyhemoglobin was >3% in only 23 samples (1.4%). A carboxyhemoglobin higher than 3% occurred at least once in eight (9.5%) patients. In our study, we found a lower incidence of hemolysis compared with Nisar et al.1 This finding may have different explanations. First, at our institution, we are used to carefully monitor the drainage pressure and adjusting the ECMO blood flow to avoid drainage pressures lower than −60/−70 mm Hg. This may limit hemolysis due to hydrodynamic cavitation. Moreover, a minor difference due to technical reason (i.e., two different blood gas analyzers) cannot be excluded. In absence of recirculation, a BF of 3–4 L/min usually allows achieving a safe oxygenation in adult patients.8 If adequate drainage cannulae are used (i.e., 21–25 Fr), this blood flow range can be usually achieved with drainage pressure of −30 to −60 mm Hg.9,10 Therefore, we hypothesize that limiting the blood flow rate to maintain “safe” drainage pressures may help in reducing the increase of carboxyhemoglobinemia during the ECMO course.