A new approach to quantifying vehicle induced turbulence for complex traffic scenarios

Traffic-related pollutants adversely affect air quality, especially in regions near major roadways. The vehicleinduced turbulence(VIT) is a significant factor that controls the initial dilution, dispersion, and ultimately the chemical and physical fate of pollutants by altering the conditions in the microenvironment. This study used a computational fluid dynamics(CFD) software FLUENT to model the vehicle-induced turbulence(VIT) generated on roadways, with a focus on impact of vehicle-vehicle interactions, traffic density and vehicle composition on turbulent kinetic energy(TKE). We show, for the first time, that the overall TKE from multiple vehicles traveling in series can be estimated by superimposing the TKE of each vehicle, without considering the distance between them while the distance is greater than one vehicle length. This finding is particularly significant since it enables a new approach to VIT simulations where the overall TKE is calculated as a function of number of vehicles. We found that the interactions between vehicles traveling next to each other in adjacent lanes are insignificant,regardless the directions of the traffic flow. Consequently, simulations of different traffic scenarios can be substantially simplified by treating two-way traffic as one-way traffic, with less than 5% difference in the overall volume-averaged TKE. We also developed equations that allow the estimation of the overall volume-averaged TKE as a function of the number and the type of vehicles.

Paradoxical carbon dioxide embolism during laparoscopic hepatectomy without intracardiac shunt:A case report

BACKGROUND Laparoscopic hepatectomy has recently become popular because it results in less bleeding than open hepatectomy.However,CO_(2)embolism occurs more frequently.Most CO_(2)embolisms during laparoscopic surgery are self-resolving and non-symptomatic;however,severe CO_(2)embolism may cause hypotension,cyanosis,arrhythmia,and cardiovascular collapse.In particular,paradoxical CO_(2)embolisms are highly likely to cause neurological deficits.We report a case of paradoxical CO_(2)embolism found on transesophageal echocardiography(TEE)during laparoscopic hepatectomy,although the patient had no intracardiac shunt.CASE SUMMARY A 71-year-old man was admitted for laparoscopic left hemihepatectomy.During left hepatic vein ligation,the inferior vena cava was accidentally torn.We observed a sudden drop in oxygen saturation to 85%,decrease in systolic blood pressure(SBP)below 90 mm Hg,and reduction in end-tidal CO_(2)to 24 mm Hg.A“mill-wheel”murmur was auscultated over the precordium.The fraction of inspired oxygen was increased to 100%with 5 cm H2O of positive end-expiratory pressure(PEEP)and hyperventilation was maintained.Norepinephrine infusion was increased to maintain SBP above 90 mm Hg.A TEE probe was inserted,revealing gas bubbles in the right side of the heart,left atrium,left ventricle,and ascending aorta.The surgeon reduced the pneumoperitoneum pressure from 17 to 14 mm Hg and repaired the damaged vessel laparoscopically.Thereafter,the patient’s hemodynamic status stabilized.The patient was transferred to the intensive care unit,recovering well without complications.CONCLUSION TEE monitoring is important to quickly determine the presence and extent of embolism in patients undergoing laparoscopic hepatectomy.

Acute lower extremity arterial thrombosis after intraocular foreign body removal under general anesthesia: A case report and review of literature

BACKGROUND Surgery,which is a major risk factor for venous thrombosis,has rarely been considered a risk factor for arterial thrombosis.Recent studies have suggested that venous and arterial thromboses share common risk factors and have a bidirectional relationship.Accordingly,there is a growing interest in the risk of arterial thrombosis after surgery.We report a case of acute bilateral lower extremity arterial thromboses that developed after a prolonged surgery.CASE SUMMARY A 59-year-old man was hospitalized for intraocular foreign body removal surgery.He was a heavy-drinking smoker and had untreated hypertension and varicose veins in both legs.The operation was unexpectedly prolonged,lasting 4 h and 45 min.Immediately after emergence from general anesthesia,the patient complained of extreme pain in both legs.After the surgical drape was removed,cyanosis was evident in both feet of the patient.The pulse was not palpable,and continuous-wave Doppler signals were inaudible in the bilateral dorsalis pedis and posterior tibial arteries.Computed tomography angiography confirmed acute bilateral thrombotic occlusion of the popliteal arteries,proximal anterior tibial arteries,and tibioperoneal trunks.Arterial pulse returned in both lower limbs after 6 h of heparin initiation.The patient was discharged on postoperative day 26 without any sequelae.CONCLUSION Acute lower extremity arterial thrombosis can occur after surgery.Anesthesiologists should pay particular attention to patients with risk factors for thrombosis.

Transient involuntary movement disorder after spinal anesthesia: A case report

BACKGROUND Spinal anesthesia is commonly used for various surgeries.While many complications occur after induction of spinal anesthesia,involuntary movement is an extremely rare complication.CASE SUMMARY Herein,we report the case of a 54-year-old healthy male patient who experienced involuntary movements after intrathecal injection of local anesthetics.This patient had undergone metal implant removal surgery in both the lower extremities;7 h after intrathecal hyperbaric bupivacaine administration,involuntary raising of the left leg began to occur every 2 min.When the movement disorder appeared,the patient was conscious and cooperative.No other specific symptoms were noted in the physical examination conducted immediately after the involuntary leg raising started;moreover,the patient's motor and sensory assessments were normal.The symptom gradually subsided.Twelve hours after the symptom first occurred,its frequency decreased to approximately once every three hours.Two days postoperatively,the symptoms had completely disappeared without intervention.CONCLUSION Anesthesiologists should be aware that movement disorders can occur after spinal anesthesia and be able to identify the cause,such as electrolyte imbalance or epilepsy,since immediate action may be required for treatment.Furthermore,it is crucial to know that involuntary movement that develop following spinal anesthesia is mostly self-limiting and may not require additional costly examinations.