A Pathophysiological Perspective on COVID-19's Lethal Complication: From Viremia to Hypersensitivity Pneumonitis-like Immune Dysregulation

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the coronavirus responsible for our recent coronavirus disease 2019 pandemic, is driving a lung immunopathology that strongly resembles a severe form of hypersensitivity pneumonitis (HP). A review of recent Severe acute respiratory syndrome-related coronavirus (SARS-CoV) and SARS-CoV-2 medical reports, as well as described characteristics of HP, lead us to postulate a theory for SARS-CoV-2 severe disease. We propose that the novel SARS-CoV-2 can act as a trigger and substrate of an HP-like severe immune reaction especially in genetically vulnerable individuals in addition to those with immune senescence and dysregulation. Accordingly, the purpose of our letter is to shift the emphasis of concern surrounding immune activity from viral infection to an HP-like severe immune reaction. We review similarities in disease presentation between infection and allergy, relevant immunopathology, and outline phases of SARS-CoV-2 disease with perspectives on therapy and critical care. Altogether, the favored course is to begin treatments that address the disease at the earliest phase before immune dysregulation leading to uncontrolled pulmonary inflammation.

Use of intraoperative transesophageal echocardiography to predict atrial fibrillation after coronary artery bypass grafting

BACKGROUND

Postoperative atrial fibrillation in coronary artery bypass graft surgery occurs in 10-40% of patients. It is associated with a significant degree of morbidity and results in prolonged lengths of stay in both the intensive care unit and hospital.

METHODS

The authors prospectively evaluated patients undergoing coronary artery bypass with detailed transesophageal echocardiography examinations conducted before and after cardiopulmonary bypass to study whether risk factors for atrial fibrillation could be identified. Demographic and surgical parameters were also included in the analysis. Selected variables were subjected to univariate and subsequent multivariate analyses to test for their independent or joint influence on atrial fibrillation.

RESULTS

Seventy-nine patients had assessable transesophageal echocardiography examinations. Significant univariate predictors of atrial fibrillation included advanced age (P = 0.002), pre-cardiopulmonary bypass left atrial appendage area (P = 0.04), and post-cardiopulmonary bypass left upper pulmonary vein systole/diastole velocity ratio (P = 0.03). When these three factors were considered together in a multiple logistic regression analysis, left upper pulmonary vein systole/diastole velocity ratio was a significant predictor (P < 0.05), as was the joint effect of age plus pre-cardiopulmonary bypass left atrial appendage area (P = 0.005). The probability of developing atrial fibrillation for the combination of age = 75 yr, post-cardiopulmonary bypass left upper pulmonary vein systole/diastole velocity ratio = 0.5, and left atrial appendage area = 4.0 cm was 0.83 (95% confidence interval, 0.51-0.96).

CONCLUSIONS

Early identification of patients at risk for postoperative atrial fibrillation may be feasible using the parameters identified in this study.

Anatomy of the spinal cord in patients with meningomyelocele with and without hypoplasia or hydromyelia

We compared the cross-sectional areas of spinal cords of patients with normal cords to the area of patients with meningomyelocele. The control group consisted of examinations of 27 patients with normal spinal cords providing 1547 axial images at 20 levels, C2-L2. The meningomyelocele group consisted of 67 MRI examinations of 41 patients, providing 4,095 axial images at 23 levels C2 to S1. Thirty-four examinations were of 21 patients with minimal hydromyelia, 7 examinations were of 3 patients with operable hydromyelia, and 26 examinations were of 17 patients without hydromyelia. In an additional analysis, we selected those meningomyelocele patients with cord tethering but without hydromyelia or hypoplasia (53 examinations of 30 patients) and compared them to symptomatic hypoplasia cases (9 examinations of 6 patients). The symptomatic hypoplasia cases were chosen because of progressive loss of muscle strength and worsening spasticity not relieved by surgical adhesiolysis. The test, retest error was 5.6% with differences between the means of repeated readings not being significant. All tests for significance were paired T test. The areas of spine levels C7-L2 for the controls were significantly larger than for the meningomyelocele patients (p = 0.000007). Including all levels C2-S1, the minimal hydromyelia cases were not significantly different from those without hydromyelia (p = 0.5). The areas C2-S1 of operable hydromyelia cases were larger than both non-shunted minimal hydromyelia (p = 0.00009) and of meningomyelocele patients without hydromyelia (p = 0.00003). The areas C7-L2, of hypoplasia cases were significantly smaller compared to the "normal" meningomyelocele cases (p = 0.0004). These data suggest that hydromyelia stimulates overgrowth of the cord, as does hydrocephalus of the brain, and that adhesiolysis procedures are of no value with hypoplasia of the spinal cord.

Epidemiology of tethered cord with meningomyelocele

This paper describes the epidemiology of tethered cord syndrome and its etiologies and co-morbidities following initial repair of both meningomyeloceles and lipomeningomyelocele. A review of the pertinent literature and data from 654 cases of meningomyelocele and 118 cases of lipomeningomyelocele has been drawn from a computerized database, Patient Data Management System/fx. Only cases born since 1964 were analyzed for the etiologies, co-morbidities, spinal cord abnormalities detected by contrast studies or MRI and for significant symptoms and signs. Tethered cord symptoms were related to an attachment to a rigid tether for all 31 cases following lipomeningomyelocele repair but 62 (75%) of the 83 post meningomyelocele repair patients developed the symptoms of tethered cord. Causes other than, or in addition to, tethering included an obstructed cerebrospinal fluid shunt, syringohydromyelia, benign tumor and spinal cord hypoplasia. Quantitative differentiation between asymptomatic thin spinal cords and symptomatic spinal cord hypoplasia as well as between central canal enlargement and symptomatic syringohydromyelia could not be demonstrated. Collaborative, multi-center studies of larger numbers of patients are recommended.

Hospital and emergency medical services system interaction during the implementation of chest pain emergency rooms

Knowledgeable personnel at 23 hospitals with chest pain emergency rooms (CPERs) served by nonhospital-based emergency health services (EMS) systems were surveyed. Although few hospitals had involved EMS in the planning stages of the CPER, there were no reports of a poor relationship with the local EMS system, and surveyed personnel perceived neither deterioration nor improvement in their hospital's relationship with EMS after opening the CPER. Hospitals where EMS was considered important to the functioning of the CPER were significantly more likely to have involved EMS in the CPER planning process.

Natriuresis associated with elevated plasma atrial natriuretic hormone during supraventricular tachycardia

Elevated plasma levels of atrial natriuretic hormone (ANH) have been found in patients during paroxysmal supraventricular tachycardia (SVT) and other clinical syndromes. However, physiologic effects of this endogenous ANH have not been demonstrated. To determine whether the rise in ANH during SVT is associated with either a natriuresis or kaliuresis, urine sodium and potassium levels were measured in five patients at baseline and during SVT simulated by rapid atrioventricular pacing. Plasma ANH levels increased from 149 +/- 35 pmol/L at baseline to 187 +/- 31 pmol/L (p = 0.007) during SVT. Plasma vasopressin and renin levels were unchanged. Urine sodium levels increased 49% from 1.54 +/- 0.66 mEq/hr at baseline to 2.29 +/- 0.89 mEq/hr (p = 0.044) during SVT, and urine potassium levels increased 22% from 4.14 +/- 0.10 mEq/hr to 5.04 +/- 1.25 mEq/hr (p = 0.018). Urine sodium and potassium levels returned to baseline values 1 hour after pacing. Thus elevated plasma levels of ANH during SVT are associated with both a natriuresis and kaliuresis, which may represent physiologic effects of the endogenously secreted hormone.

A new in vivo method for repeatedly studying gastric acid secretion and other secretory parameters in awake guinea pig

A new model for measuring gastric secretory parameters in awake guinea pigs is described. A chronic cannula was surgically implanted in the stomach of each guinea pig. The rates of gastric secretion and changes in intragastric volume were measured using a dye dilution technique. In contrast to previous techniques in small laboratory animals, there was no collection of gastric juice via drainage, no oral intubation for aspiration was involved, no special or sophisticated equipment was used, no anesthesia was employed, and there was no stress associated with acute surgery. This method offers a valuable advantage by combining the chronic gastric cannula with a dye dilution technique in that the same animal can be used several times and finally, several gastric secretory parameters can be measured simultaneously. The animals were used from 3 weeks to 10 months after surgery and as many as 15 studies were performed on the same guinea pig. Samples were collected at 10-min intervals and analyzed for acid and dye concentration from which the onset and kinetics of gastric secretion were followed. Basal gastric secretion (11.8 +/- 1.6 mueq/kg/min; all mean +/- 1 SEM) was increased within 20 min after subcutaneous infusion of histamine (30 micrograms/kg/hr) and peaked by 40-60 min at a mean acid output rate of 41 +/- 3 mueq/kg/min. Histamine also increased the intragastric volume from 6.3 to 13.4 ml as it increased fluid output from 1.6 +/- 0.1 ml/10 min to 3.4 +/- 0.2 ml/10 min. The increase in acid output caused by histamine was inhibited by the H2-antagonists cimetidine (3 mumole/kg) and ranitidine at 0.5 mumole/kg. Omeprazole (1.2 mumole/kg), an H-K-ATPase inhibitor, almost abolished acid output under both basal and histamine-stimulated conditions. Thus, the present method is simple and suitable to study the physiology and pharmacology of gastric secretion in the guinea pig with a particular emphasis on the action of histamine. Furthermore, because of the species involved, there is also a significant economical advantage and the guinea pig can also be used as a potential model for studying experimental ulcer.

Stimulation of inositol trisphosphate and diacylglycerol production in renal tubular cells by parathyroid hormone

Parathyroid hormone (PTH) produced a dose-dependent immediate stimulation of inositol triphosphate and diacylglycerol production in the opossum kidney cell line, primary culture proximal tubular cells, and basolateral membranes from canine proximal tubular segments. The increase in inositol triphosphate production was accompanied by a minor increase in inositol phosphate and no significant increase in inositol bisphosphate production. Associated with the changes in inositol triphosphate and diacylglycerol, there was an immediate hydrolysis of phosphatidylinositol 4'5-bisphosphate. The effect on phospholipid hydrolysis was followed by stimulation of phosphorylation of phosphatidylinositol 4' monophosphate and phosphatidylinositol. PTH produced a sudden increase in cytoplasmic Ca2+ in opossum kidney cells that persisted for approximately 1 min. Inositol triphosphate transiently increased cytoplasmic Ca2+ in saponin-treated opossum kidney and primary culture proximal tubule cells. The effects of PTH were not mimicked by cyclic nucleotides. In fact, cyclic AMP appeared to diminish inositol triphosphate production. These results demonstrate that PTH may activate renal tubular epithelial cells by the production of inositol triphosphate and diacylglycerol.

Effects of parathyroid hormone on cytosolic calcium in renal proximal tubular primary cultures

The effects of parathyroid hormone on the cytoplasmic Ca2+ concentration of canine renal proximal tubule cells grown in primary culture were determined using the fluorescent Ca2+ indicator quin 2. The cultured cells exhibited responses to hormones, enzyme activities, transport functions, and morphology characteristic of the proximal convoluted tubule. Parathyroid hormone stimulated an immediate rise in cytoplasmic Ca2+, both in suspended cells and cells studied as a monolayer on Nuclepore filters. The rise in cytoplasmic Ca2+ induced by the hormone was sustained for 15-30 min, was dose dependent, and was not mimicked by cyclic AMP. Removing Ca2+ from the extracellular media markedly decreased cytoplasmic Ca2+ and abolished the effects of parathyroid hormone on cytosolic Ca2+. 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate blocked the effects of the hormone on cytosolic Ca2+, but mitochondrial uncouplers failed to inhibit the effects of the hormone to increase cytoplasmic Ca2+. These studies support a role of Ca2+ in the activation of proximal renal tubule cells by parathyroid hormone.

Steroid use in idiopathic sudden sensorineural hearing loss

Few studies have investigated the effect of steroids on idiopathic sudden hearing loss (ISHL). Recently, Wilson, et al., reported a double blind study demonstrating a statistically significant improvement of hearing using steroids is ISHL. This report, fashioned after the Wilson study, confirms his findings and analyzes the relationship of several factors to the probability of hearing recovery.

Foreign-body aspiration. Potential misdiagnosis

Clandestine aspiration of foreign bodies lodged high in tracheal airway can mimic subglottic croup. Although this relationship is emphasized in textbooks of otolaryngology, documentation in the recent literature is lacking. This report underscores our awareness of a potentially lethal diagnosis masquerading as a more benign viral infection of the laryngotracheal airway.

Gaseous exchange and acid-base balance in premature lambs during liquid ventilation since birth

Nine distressed premature lambs were studied before, during, and after ventilation with fluorocarbon liquid (FC-80). It was found that premature lambs, delivered by cesarean section, could be adequately ventilated with oxygenated liquid for period up to 3 hr. Using fluarocarbon liquid in conjunction with the described liquid breathing system, it was possible to maintain remarkably good pulmonary gas exchange and acid-base balance during normothermic conditions. In addition, peak intratracheal pressures measured during recovery from liquid ventilation were significanly reduced (P is less than 0.001) as compared with preliquid ventilation values. This improvement in lung function is in direct contrast to the deterioration in that of the adult animal following liquid ventilation as reported previously.