Red Blood Cell Transfusion in the Intensive Care Unit.

Importance: Red blood cell (RBC) transfusion is common among patients admitted to the intensive care unit (ICU). Despite multiple randomized clinical trials of hemoglobin (Hb) thresholds for transfusion, little is known about how these thresholds are incorporated into current practice. Objective: To evaluate and describe ICU RBC transfusion practices worldwide. Design, Setting, and Participants: International, prospective, cohort study that involved 3643 adult patients from 233 ICUs in 30 countries on 6 continents from March 2019 to October 2022 with data collection in prespecified weeks. Exposure: ICU stay. Main Outcomes and Measures: The primary outcome was the occurrence of RBC transfusion during ICU stay. Additional outcomes included the indication(s) for RBC transfusion (consisting of clinical reasons and physiological triggers), the stated Hb threshold and actual measured Hb values before and after an RBC transfusion, and the number of units transfused. Results: Among 3908 potentially eligible patients, 3643 were included across 233 ICUs (median of 11 patients per ICU [IQR, 5-20]) in 30 countries on 6 continents. Among the participants, the mean (SD) age was 61 (16) years, 62% were male (2267/3643), and the median Sequential Organ Failure Assessment score was 3.2 (IQR, 1.5-6.0). A total of 894 patients (25%) received 1 or more RBC transfusions during their ICU stay, with a median total of 2 units per patient (IQR, 1-4). The proportion of patients who received a transfusion ranged from 0% to 100% across centers, from 0% to 80% across countries, and from 19% to 45% across continents. Among the patients who received a transfusion, a total of 1727 RBC transfusions were administered, wherein the most common clinical indications were low Hb value (n = 1412 [81.8%]; mean [SD] lowest Hb before transfusion, 7.4 [1.2] g/dL), active bleeding (n = 479; 27.7%), and hemodynamic instability (n = 406 [23.5%]). Among the events with a stated physiological trigger, the most frequently stated triggers were hypotension (n = 728 [42.2%]), tachycardia (n = 474 [27.4%]), and increased lactate levels (n = 308 [17.8%]). The median lowest Hb level on days with an RBC transfusion ranged from 5.2 g/dL to 13.1 g/dL across centers, from 5.3 g/dL to 9.1 g/dL across countries, and from 7.2 g/dL to 8.7 g/dL across continents. Approximately 84% of ICUs administered transfusions to patients at a median Hb level greater than 7 g/dL. Conclusions and Relevance: RBC transfusion was common in patients admitted to ICUs worldwide between 2019 and 2022, with high variability across centers in transfusion practices.

Patterns in the parathyroid response to sodium bicarbonate infusion test in healthy volunteers.

BACKGROUND: The sodium bicarbonate infusion test evaluates the function of the parathyroid glands. The present study aims to evaluate the range of parathyroid response in healthy individuals and the potential influence of various factors. METHODS: Fifty healthy volunteers were subjected to the test. Levels of vitamin D, calcium, albumin, and PTH were measured before infusion. PTH was measured at 3, 5, 10, 30, and 60 minutes after infusion. RESULTS: A curve describing the response of parathyroids to the test was drawn. Twenty percent of the subjects had blunted PTH response. No significant difference was observed between normal and blunted responders concerning age, BMI, baseline PTH, or calcium levels. Nonetheless, there was a significant difference in vitamin D levels (P = 0.024). INTERPRETATION: The test is easy to perform and may be used for everyday screening. It has to be clarified whether our observations are, at least partly, produced due to the presence of individuals with a constitutively blunted response or if low levels of vitamin D decrease the ability of the parathyroids to respond. Whichever the case, PTH response of normal individuals to sodium bicarbonate infusion test is more varied than previously thought and vitamin D levels influence it.

Secretory capacity of the parathyroid glands after total thyroidectomy in normocalcemic subjects.

CONTEXT: Hypocalcemia, transient or permanent, represents a common complication after total thyroidectomy, but data on the secretory capacity of the parathyroid glands in thyroidectomized patients without clinical or biochemical hypocalcemia are limited. STUDY DESIGN: To address this issue, we studied the parathyroid response to acute hypocalcemia induced by iv infusion of sodium bicarbonate in normocalcemic patients submitted to total thyroidectomy at the early postoperative period and 3 months later. PATIENTS AND METHODS: Sixty patients who underwent total thyroidectomy for benign thyroid disease and did not develop clinical or biochemical hypocalcemia and hypoparathyroidism postoperatively and 50 healthy volunteers were included in the study. Patients (at 48 h and 3 months after surgery) and controls (after overnight fast) were subjected to a sodium bicarbonate infusion test. RESULTS: In healthy volunteers plasma intact PTH increased significantly at 3 min after infusion (4.42 ± 0.15 ng/ml vs. 11.22 ± 0.5 ng/ml, P < 0.001) and gradually returned to baseline values. In the thyroidectomized patients, mean PTH levels were also increased after sodium bicarbonate infusion but to a significantly lesser degree compared with healthy controls (1.77 mean fold increase vs. 2.57 mean fold increase, respectively, P < 0.001). Using as criterion the lowest fold increase of plasma PTH levels at 3 min after infusion observed in healthy volunteers, 38% of the thyroidectomized patients at 48 h after surgery and 6.6% of the patients at 3 months after surgery demonstrated a diminished PTH response to acute hypocalcemia induced by sodium bicarbonate infusion. CONCLUSION: In thyroidectomized patients, normal postoperative calcium and PTH values do not exclude a reduced secretory response of the parathyroids to hypocalcemic stimuli.