Role of arterial blood gas (ABG) as a valuable assessment tool of disease severity in SARS-CoV-2 patients

BackgroundCOVID-19 is caused by a novel coronavirus, named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The foremost predominant complication of SARS-CoV-2 is arterial hypoxemia thereby disturbing lung compliance, requiring mechanical ventilation. The aim of the current research study is to analyze role of ABG as a valuable assessment tool of disease severity in SARS-CoV-2 patients.Methods170 arterial blood samples were collected from patients admitted in Intensive Care Unit (ICU) of Sri Guru Ram Das Charitable Hospital, Amritsar. They were analyzed for arterial blood gas using ABG analyzer. Parameters of ABG such as pH, pCO2, HCO3, O2 saturation, ionized calcium (iCa) and calculated ionized calcium (at pH 7.4) was calculated for all the samples.ResultsContinuous variables were described as medians with interquartile ranges (IQRs) and categorical variables as percentages and frequencies. Spearman correlation test was done for calculation of correlation between pH and other ABG parameters. Analysis of arterial blood gas revealed significant negative correlation (p<0.05) between pH and pCO2 and significant positive correlation (p<0.05) between pH and HCO3 and between pH and delta ionized calcium. Low levels (98.2%) of ionized calcium were observed while monitoring the ABG findings though weak negative correlation (p<0.05) was observed between pH and iCa.ConclusionsOur study suggests that ABG analysis acts as a momentous indicator for critically ill patients admitted in Intensive Care Unit (ICU). Estimation of iCa in this critical care setting acts as a distinctive biochemical feature of SARS-CoV-2 disease, as an initial assessment tool, for hypocalcemia.     

Interleukin-6 Induced Suppression of Bovine Parathyroid Hormone Secretion

Calcium disturbances in the critically ill coincide with elevations of proinflammatory cytokines. The effects of tumor necrosis factor- (TNF-) and interleukin-6 (IL-6) on parathyroid hormone (PTH) secretion were investigated. IL-6 and TNF- had no acute effect on PTH secretion in extracellular Ca²⁺ concentrations of 0.5, 1.25 and 3.0 mM. In contrast to TNF-, cultures for 24 h in the presence of l0 ng/mL of IL-6 showed decreased PTH secretion by 51% and 29% in 0.5 mM and 1.25 mMCa²⁺ respectively. Neither IL-6 nor TNF-, affected cytoplasmic Ca²⁺ of the cells. We conclude that PTH secretion in vitro can be suppressed by IL-6 at clinically relevant concentrations. This suppression may aggravate hypocalcemia of the critically ill and attenuate the conventionally strong stimulation of the PTH release by reduction in serum calcium.     

Cataracts in a laboratory colony of African green monkeys (Chlorocebus aethiops)

Three cases of spontaneous cataracts were investigated in a colony of African green monkeys (Chlorocebus aethiops). Clinical, pathological and microbiological investigations were conducted in two cases of juvenile cataracts and in one case of a mature cataract. These investigations revealed no indication of an infection as the cause of cataract development. A genetic correlation existed between the affected individuals. Clinical chemistry gave a hint that calcium might be a "key factor" in the development of these cataracts: in both cases of the juvenile cataracts, the calcium content in the serum and in the aqueous humor was clearly decreased in the affected babies. The calcium uptake in the affected baby itself was not altered but the calcium content in the mother's milk was low.     

Hypocalcemia-Induced Seizure: Demystifying the Calcium Paradox

Calcium is essential for both neurotransmitter release and muscle contraction. Given these important physiological processes, it seems reasonable to assume that hypocalcemia may lead to reduced neuromuscular excitability. Counterintuitively, however, clinical observation has frequently documented hypocalcemia’s role in induction of seizures and general excitability processes such as tetany, Chvostek’s sign, and bronchospasm. The mechanism of this calcium paradox remains elusive, and very few pathophysiological studies have addressed this conundrum. Nevertheless, several studies primarily addressing other biophysical issues have provided some clues. In this review, we analyze the data of these studies and propose an integrative model to explain this hypocalcemic paradox.     

Dietary supplementation of essential oils in dairy cows: evidence for stimulatory effects on nutrient absorption

Results of recent in vitro experiments suggest that essential oils (EO) may not only influence ruminal fermentation but also modulate the absorption of cations like Na⁺, Ca²⁺ and NH₄⁺ across ruminal epithelia of cattle and sheep through direct interaction with epithelial transport proteins, such as those of the transient receptor potential family. The aim of the current study was to examine this hypothesis by testing the effect of a blend of essential oils (BEO) on cation status and feed efficiency in lactating dairy cows. In the experiment, 72 dairy cows in mid-to-end lactation were divided into two groups of 36 animals each and fed the same mixed ration with or without addition of BEO in a 2×2 cross-over design. Feed intake, milk yield and composition, plasma and urine samples were monitored. Feeding BEO elevated milk yield, milk fat and protein yield as well as feed efficiency, whereas urea levels in plasma and milk decreased. In addition, plasma calcium levels increased significantly upon BEO supplementation, supporting the hypothesis that enhanced cation absorption might contribute to the beneficial effects of these EO.     

Peripartum Ca and P homeostasis in multiparous sows fed adequate or excess dietary Ca

The recent increased prevalence of uterine prolapses in sows around parturition has led to inferences that the prolapses may be associated with hypocalcemia. However, limited data are available to support that hypocalcemia occurs in sows. Hypocalcemia in dairy cows is associated with feeding excess dietary Ca during late gestation. The excess Ca is assumed to suppress homeostatic mechanisms critical to maintain serum Ca concentrations as the Ca demand increases during the early stages of lactation. In this experiment, sows were fed diets with excess Ca during late gestation and early lactation to assess the potential development of hypocalcemia in the peripartum period. Twelve crossbred (Large White × Landrace) multiparous gestating sows were fed a control diet (CON), 0.65% Ca to 0.38% standardized total tract digestible P (STTD P) and 0.67% Ca to 0.38% STTD P in gestation and lactation diets, respectively) or a high Ca diet (HCa, 1.75% Ca to 0.46% STTD P and 1.75% Ca to 0.45% STTD P in gestation and lactation diets, respectively). The diets were fed from gestation day 86 þ ± 1 until the end of lactation (27 þ ± 2 days period). On day 112 of gestation, indwelling venous catheters were placed in each sow. Blood samples were collected at 15-min intervals within four designated times (0700, 1000, 1300 and 1700 h) on gestation day 113 and lactation days 1, 3 and 5. Venous blood pH, gases (pO₂, pCO₂ and HCO₃⁻), electrolytes (K⁺, Na⁺ and Cl⁻), ionized Ca (iCa), metabolites (glucose and lactate), plasma total Ca (tCa), and P were analyzed. Overall, sows fed HCa diet had greater (P < 0.001) concentrations of blood iCa and plasma tCa than sows fed CON diets. No clinical signs of Ca metabolism disorders were observed. Unexpectedly, concentrations of plasma P in sows fed HCa diets were lower (P < 0.001) than in sows fed CON diets. Plasma P tended to decrease (P = 0.057) as day of lactation increased. Differences between dietary treatments for blood pH, gases, electrolytes and metabolites were not detected (P > 0.05). No evidence for hypocalcemia was detected in peripartum sows fed CON or HCa diets. These data imply that excess Ca in late gestation diets did not result in hypocalcemia during the peripartum period. Future experiments should focus on factors other than hypocalcemia to identify causes of uterine prolapses in sows.     

Radiographic diagnosis of metabolic bone disease in captive bred mountain chicken frogs (Leptodactylus fallax)

Asymptomatic captive bred and wild-caught mountain chicken frogs (Leptodactylus fallax) were radiographed for evidence of metabolic bone disease (MBD). All 22 captive bred frogs had multiple folding fractures of long bones, decreased bone density, and cortical thinning, whereas none of the 11 wild-caught frogs had any radiographic evidence of MBD. These findings suggest that the nutritional requirements of L. fallax need to be examined for captive management purposes.     

Effect of boron on vitamin D deficient rats

The effects of different levels of dietary boron were determined in vitamin D deficient rats. Vitamin D deficient diets containing either 0.158 ppm or 2.72 ppm of boron were fed to rats for 11 w, and calcium, magnesium, and phosphorus apparent absorption and balance were measured in the twelfth week. Higher apparent absorption and balance values for calcium and phosphorus were observed in the rats with higher dietary boron, but very few differences were seen in body wt, organ wt, and bone parameters. Balance measurements represented the present status of the rats after 12 w on the diets, but other measurements represented an accumulation over the lifetime of the rat, including a suckling period with ample vitamin D and boron. The data demonstrated that when rats are vitamin D deficient, as indicated by hypocalcemia, the level of boron in the diet affects mineral balance.     

The Optimal Parathyroid Hormone Cut-Off Threshold for Early and Safe Management of Hypocalcemia After Total Thyroidectomy

ObjectiveTo define optimal intact parathyroid hormone (iPTH) cut-off threshold predictive of hypocalcemia after total thyroidectomy for safe and effective postoperative management.MethodsThis prospective single center study was done in 2 phases. In phase I, predictors of symptomatic hypocalcemia were analyzed and the receiver operating characteristic curve was used to define the optimal iPTH cut-off threshold predictive of hypocalcemia. Phase II studied giving prompt prophylactic supplemental calcium and vitamin D to all patients who had iPTH levels below the calculated threshold, while phase I patients were given prompt selective supplementation if they had postoperative hypocalcemia or symptoms.ResultsUnivariate analysis of patients in phase I showed that postoperative iPTH was the only significant variable that can predict symptomatic hypocalcemia. Using receiver operating characteristic curve and Youden index, the confirmed optimal cut-off threshold predictive of hypocalcemia was iPTH 19.95 pg/mL, with area under the curve of 0.903, 100% sensitivity, negative predictive value, and highest Youden index, while iPTH 15 pg/mL and iPTH 10 pg/mL were less optimal. Symptomatic hypocalcemia occurred in 30% of the phase I cohort who received selective supplementation versus 3% of those in the phase II cohort who received prophylactic supplementation. Return to emergency department and need for intravenous calcium were also significantly better in phase II.ConclusioniPTH cut-off for post-thyroidectomy hypocalcemia was 19.95 pg/mL. Low-risk patients were discharged with no supplementation while all high-risk patients received prompt calcium and vitamin D supplementation, which led to effective hypocalcemia management and safe 24-hour discharge.