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Purpose: To describe the reliability of blood bicarbonate pharmacokinetics in response to sodium bicarbonate (SB) supplementation across multiple occasions and assess, using putative thresholds, whether individual variation indicated a need for individualized ingestion timings., Methods: Thirteen men (age 27 ± 5 yr; body mass [BM], 77.4 ± 10.5 kg; height, 1.75 ± 0.06 m) ingested 0.3 g·kg BM SB in gelatine capsules on three occasions. One hour after a standardized meal, venous blood was obtained before and every 10 min after ingestion for 3 h, then every 20 min for a further hour. Time to peak (Tmax), absolute peak (Cmax), absolute peak change ([INCREMENT]Cmax), and area under the curve were analyzed using mixed models, intraclass correlation coefficient, coefficient of variation and typical error. Individual variation in pharmacokinetic responses was assessed using Bayesian simulation with multilevel models with random intercepts., Results: No significant differences between sessions were shown for blood bicarbonate regarding Cmax, [INCREMENT]Cmax or area under the curve (P > 0.05), although Tmax occurred earlier in SB2 (127 ± 36 min) than in SB1 (169 ± 54 min, P = 0.0088) and SB3 (159 ± 42 min, P = 0.05). Intraclass correlation coefficient, coefficient of variation, and typical error showed moderate to poor reliability. Bayesian modeling estimated that >80% of individuals from the population experience elevated blood bicarbonate levels above +5 mmol·L between 75 and 240 min after ingestion, and between 90 and 225 min above +6 mmol·L., Conclusions: Assessing SB supplementation using discrete values showed only moderate reliability at the group level, and poor reliability at the individual level, whereas Tmax was not reproducible. However, when analyzed as modeled curves, a 0.3-g·kg BM dose was shown to create a long-lasting window of ergogenic potential, challenging the notion that SB ingestion individualized to time-to-peak is a necessary strategy, at least when SB is ingested in capsules.

Objectives: To examine: a) the rate and extent of delivery of radioactive tracers to the central circulation from the tibial, medial malleolar, distal femoral, and humeral intraosseous sites, as well as from a peripheral intravenous site; and b) the end-tidal CO2 response to injected sodium bicarbonate at these sites., Design: Prospective, descriptive study., Setting: Animal laboratory at a university medical center., Subjects: Twenty anesthetized and mechanically ventilated piglets were cannulated with 18-gauge bone marrow needles at intraosseous sites and 22-gauge Teflon catheters in peripheral veins. A 22-gauge angiocath was placed in the right carotid artery of each subject. Drug kinetics were studied in the normovolemic and hypovolemic (acute bleeding of 25 mL/kg) states., Interventions: Sodium bicarbonate (1 mEq/kg) was injected into each of the three intraosseous and one intravenous sites with simultaneous monitoring of end-tidal CO2. A 10-min period for stabilization was allowed between injections. Aliquots of 99mtechnetium were injected at randomly selected sites and blood samples were obtained at 1.5-sec intervals via carotid artery for radioactive counts. Experiments were repeated after withdrawal of 25 mL/kg of blood., Measurements and Main Results: Assessment by end-tidal CO2 monitoring after 1-mEq/kg injections of bicarbonate demonstrated a mean initial end-tidal CO2 increase at 12.8 secs and a mean maximal end-tidal CO2 increase of 8 torr (1.06 kPa), with no significant site differences noted. Radioactive tracer injections were detected in the carotid artery after 15.4 secs in normovolemic animals and after 21.4 secs in hypovolemic animals, with no significant site differences detected. The proportion of injected tracer at 2, 5, 10, 20, 30, and 40 mins identified no significant differences between various intraosseous and intravenous sites., Conclusions: Our study demonstrated similar rapid transit and proportion of bicarbonate and radioactive tracers, reaching the central circulation from multiple intraosseous sites and a peripheral intravenous site. This finding suggests that adjustments in drug dosage may not be required, using various intraosseous locations as an alternative to peripheral intravenous drug therapy.