Effects of hypoxemia on the electroretinogram in diabetics

Purpose: To identify any relationship between retinal dependence on oxygen and the presence or absence of retinopathy in a group of patients with the same duration of diabetes, based on the proposal that diabetic retinopathy results from long-term adaptation to the Crabtree effect, i.e., reduction of oxidative phosphorylation caused by increased intracellular glucose concentrations. Methods: Electroretinograms were recorded on 17 patients with insulin-dependent diabetes (of 15 to 17 years duration) and 10 healthy controls. Recordings were made under normal conditions and then after 4 min of hypoxemia (oxygen saturation, 80%). Retinopathy status was assessed from fundus photographs. Results: Electroretinogram b-wave amplitudes of seven patients without retinopathy were reduced to 69% by the hypoxemia compared to a reduction to 88% for 10 patients with retinopathy (p = 0.039). Conclusions: The relative sensitivity to hypoxemia of patients without retinopathy suggests greater dependence on oxidative phosphorylation than in patients with retinopathy. The results appear to be consistent with the Crabtree effect hypothesis. Downregulation of tissue oxygen consumption by the Crabtree effect would lead to a reduction of retinal blood flow by autoregulation and to a reduced concentration of adenosine triphosphate in the retina.     

无创正压通气治疗术后低氧血症的临床分析

目的:探讨无创正压通气(NPPV)在术后发生低氧血症治疗中的作用.方法:采用回顾性分析的方法,按不同病因将26例术后低氧血症病人分为2组,一组为心源性肺水肿15例,另一组为急性呼吸窘迫综合征(ARDS)11例.均采用鼻(面)罩行NPPV治疗,模式为双水平气道正压通气(BiPAP),设置参数吸气压(IPAP)及呼气压(EPAP).观察并比较两组病人治疗后呼吸(RR)、心率(HR)、氧合指数(OI=PaO2/FiO2)及NPPV治疗时间.结果:两组病人比较在通气治疗后2小时RR、HR、OI等变化均有显著性差异(P＜0.05).每组病例在NPPV治疗前后RR、HR、OI的差异有显著性(P＜0.05).心源性肺水肿组使用NPPV时间明显短于ARDS组,差异有显著性(P＜0.05).结论:NPPV治疗能改善术后低氧血症.与ARDS相比,心源性肺水肿所致低氧血症更容易纠正.     

Release of xanthine oxidase to the systemic circulation during resuscitation from severe hypoxemia in newborn pigs

Xanthine oxidase may contribute to oxygen free radical formation during reoxygenation after hypoxia, but in humans the enzyme is present in substantial amounts only in the liver and intestine. We developed a sensitive assay for xanthine oxidase using ¹⁴C–xanthine as substrate and investigated whether xanthine oxidase was released into the systemic circulation when 19 newborn pigs were resuscitated after severe hypoxemia. In five piglets plasma xanthine oxidase concentrations increased from undetectable levels to a median value of 8 (range 4–18) μU/ml after 30 min of reoxygenation. In these pigs serum aspartate aminotransferase increased from 45 to 148 U/l, while alanine aminotransferase was unchanged (28–31 U/l). The release of xanthine oxidase did not seem to correlate with the severity of the histological brain damage after 4 days. We conclude that only low levels of xanthine oxidase are released to the systemic circulation after severe hypoxemia in newborn pigs.     

Morphology,immunohistochemistry and morphometry of the thyroid gland in cases of sudden infant death syndrome (SIDS)

The thyroid glands of 107 SIDS victims (sudden infant death syndrome) have been studied. Controls consisted of 20 thyroid glands from infants who died of other causes (accidents, pneumonia etc.). The thyroid glands were investigated histologically, immunohistologically and morphometrically. Immunohistochemistry (S100 protein and calcitonin) and morphometry showed no significant results. Histologically, hyperemia (severe: 34 cases = 31.8%; mild: 23 cases = 21.5%), and fibrosis (45 cases = 42.1%; mild: 26 cases = 24.3%) were found. A large number of cases showed depleted follicles (87 cases 81.3%), little colloid (little: 37 cases = 34.6%; none: 9 cases = 8.4%) and desquamation (severe: 21 cases = 19.6%; abundant: 20 cases = 18.7%). Only fibrosis and depleted follicles were found more often in SIDS than in the controls (conditional logistic regression: rise of incidence for SIDS 2.9 times,P = 0.028, and 1.2 times,P = 0.051, respectively), a commoner occurrence of hyperemia in SIDS was of limited significance (P = 0.105). The alterations found can be taken as stress reactions to current or recurrent hypoxemia and the mild fibrosis indicates recurrent hypoxemia. All alterations indicate that the victims had previously suffered near death episodes. Even though the glands were handled with care, artefacts and autolysis must be taken into consideration. Neither the histological, immunohistological nor morphometrical studies of the thyroid gland gave an explanation as to the cause of death or showed any changes providing explicit help in diagnosing SIDS.     

基于新冠肺炎病理生理机制的治疗策略

自新型冠状病毒肺炎(coronavirus disease 2019,COVID-19)发生以来,疫情迅速蔓延,截至2020年3月11日,全国累计确诊病例80 955例,累计死亡病例3 162例。鉴于COVID-19对公众健康的危害极大,各级政府、卫生防疫、医疗、科研部门高度重视,围绕病原体鉴定、溯源、病例筛查、人群隔离、疾病诊断、疫苗和新药,以及治疗方案等开展了大量研究。国家卫生健康委员会制定了《新型冠状病毒肺炎诊疗方案》,并已修订至第七版,对指导临床诊治发挥了积极作用[1]。由于该病为新发传染病,对其发病机制缺乏深入认识,尚缺乏特异有效的药物和疫苗,治疗措施多为对症和支持治疗。     

Hypoxemia in patients on chronic opiate therapy with and without sleep apnea

Objective  Animal models have shown a quantal slowing of respiratory pattern when exposed to opioid agonist, in a pattern similar to that observed in central sleep apnea. We postulated that opioid-induced hypoventilation is more likely to be associated with sleep apnea rather than hypoventilation alone. Since we did not have a direct measure of hypoventilation we used hypoxemia as an indirect measure reasoning that significant hypoventilation would not occur in the absence of hypoxemia. Methods  We conducted a retrospective analysis of 98 consecutive patients on chronic opioid medications who were referred for overnight polysomnography. All patients on chronic opioids seen in the chronic pain clinic were referred for a sleep study regardless of whether they had sleep symptoms or not. Sleep-related hypoxemia was defined as arterial oxyhemoglobin saturation of less than 90% for more than 5 min with a nadir of ≤85%, or greater than 30% of total sleep time at an oxyhemoglobin saturation of less than 90%. Results  Of the 98 patients, 36% (95% CI 26–46%) had obstructive sleep apnea, 24%, (95% CI 16–33%) had central sleep apnea, 21% (95% CI 14–31%) had combined obstructive and central sleep apnea, in 4% (95% CI 0–10%) sleep apnea was classified as indeterminate, and 15% (95% CI 9–24%) had no sleep apnea. Opioids were potentially responsible for hypoxemia during wakefulness in 10% of patients (95% CI 5–18%) and for hypoxemia during sleep not clearly associated with apneas/hypopneas in 8% of patients (95% CI 4–15%). Two patients (2%, 95% CI 0–7%) had sleep-related hypoxemia in the absence of sleep apnea or hypoxemia during wakefulness. Conclusions  Patients on chronic opiate therapy for chronic pain have an extremely high prevalence of sleep apnea and nocturnal hypoxemia. Hypoxemia can occur during quiet wakefulness in patients on chronic opioid medications with and without sleep apnea. In patients on chronic opioid therapy, isolated nocturnal hypoxemia without coexisting sleep apnea or daytime hypoxemia is very uncommon.     

66例肝硬变患者的血氧变化

目的:了解肝炎后肝硬变患者的动脉血氧水平并探讨其临床意义。方法:应用自动血气分析仪检测66例肝炎后肝硬变患者和20例正常人的动脉血氧分压、血二氧化碳分压及血氧饱和度。结果:肝硬吏患者的动脉血氧分压为10.55±2.61kPa,明显低于正常人(P<0.05)。低氧血症发生率为56.0％(37/66),与腹水、门静脉增宽、皮肤蜘蛛痣及肝贮备功能降低密切相关,好发于并发急性上消化道出血、肝性脑病,肝肾综合征和自发性腹膜炎的患者。结论:动脉血氧水平检测有助于肝硬变的预后判断。