Hypoxia inhibits activity and expression of transporters involved in alveolar Na reabsorption and fluid clearance. We studied whether this represents a mechanism for reducing energy consumption or whether it is the consequence of metabolic dysfunction. Oxygen consumption (JO2) of A549 cells and primary rat alveolar type II cells was measured by microrespirometry during normoxia, hypoxia (1.5% O2), and reoxygenation. In both cell types, acute and 24-h hypoxia decreased total JO2 significantly and reoxygenation restored JO2 after 5 min but not after 24 h of hypoxia in A549 cells, whereas recovery was complete in type II cells. In A549 cells under normoxia Na/K-ATPase accounted for approximately 15% of JO2, whereas Na/K-ATPase-related JO2 was decreased by approximately 25% in hypoxia. Inhibition of other ion transporters did not affect JO2. Protein synthesis-related JO2 was not affected by acute hypoxia, but decreased by 30% after 24-h hypoxia. Acute and 24-h hypoxia decreased JO2 of A549 cell mitochondrial complexes I, II, and III by 30-40%. Reoxygenation restored complex I activity after acute hypoxia but not after 24-h hypoxia. ATP was decreased 30% after 24-h hypoxia, but lactate production rate was not affected. Reduced nicotinamine adenine dinucleotide was slightly elevated in acute hypoxia. Our findings indicate that inhibition of the Na/K-ATPase by hypoxia contributes little to energy preservation in hypoxia. It remains unclear to what extent hypoxic inhibition of mitochondrial metabolism affects ATP-consuming processes.

Physical exertion is thought to exacerbate acute mountain sickness (AMS). In this prospective, randomized, crossover trial, we investigated whether moderate exercise worsens AMS in normobaric hypoxia (12% oxygen, equivalent to 4,500 m). Sixteen subjects were exposed to altitude twice: once with exercise [3 × 45 min within the first 4 h on a bicycle ergometer at 50% of their altitude-specific maximal workload (maximal oxygen uptake)], and once without. AMS was evaluated by the Lake Louise score and the AMS-C score of the Environmental Symptom Questionnaire. There was no significant difference in AMS between the exposures with and without exercise, neither after 5, 8, nor 18 h (incidence: 64 and 43%; LLS: 6.5 ± 0.7 and 5.1 ± 0.8; AMS-C score: 1.2 ± 0.3 and 1.1 ± 0.3 for exercise vs. rest at 18 h; all P > 0.05). Exercise decreased capillary Po(2) (from 36 ± 1 Torr at rest to 31 ± 1 Torr), capillary arterial oxygen saturation (from 72% at rest to 67 ± 2%), and cerebral oxygen saturation (from 49 ± 2% at rest to 42 ± 1%, as assessed by near-infrared spectroscopy; P < 0.05), and increased ventilation (capillary Pco(2) 27 ± 1 Torr; P < 0.05). After exercise, the increase in ventilation persisted for several hours and was associated with similar levels of capillary and cerebral oxygenation at the exercise and rest day. We conclude that moderate exercise at ~50% maximal oxygen uptake does not increase AMS in normobaric hypoxia. These data do not exclude that considerably higher exercise intensities exacerbate AMS.

PurposeBoth exercise and hypoxia cause complex changes in acid–base homeostasis. The aim of the present study was to investigate whether during intense physical exercise in normoxia and hypoxia, the modified physicochemical approach offers a better understanding of the changes in acid–base homeostasis than the traditional Henderson–Hasselbalch approach.MethodsIn this prospective, randomized, crossover trial, 19 healthy males completed an exercise test until voluntary fatigue on a bicycle ergometer on two different study days, once during normoxia and once during normobaric hypoxia (12% oxygen, equivalent to an altitude of 4500 m). Arterial blood gases were sampled during and after the exercise test and analysed according to the modified physicochemical and Henderson–Hasselbalch approach, respectively.ResultsPeak power output decreased from 287 ± 9 Watts in normoxia to 213 ± 6 Watts in hypoxia (−26%, P < 0.001). Exercise decreased arterial pH to 7.21 ± 0.01 and 7.27 ± 0.02 (P < 0.001) during normoxia and hypoxia, respectively, and increased plasma lactate to 16.8 ± 0.8 and 17.5 ± 0.9 mmol/l (P < 0.001). While the Henderson–Hasselbalch approach identified lactate as main factor responsible for the non-respiratory acidosis, the modified physicochemical approach additionally identified strong ions (i.e. plasma electrolytes, organic acid ions) and non-volatile weak acids (i.e. albumin, phosphate ion species) as important contributors.ConclusionsThe Henderson–Hasselbalch approach might serve as basis for screening acid–base disturbances, but the modified physicochemical approach offers more detailed insights into the complex changes in acid–base status during exercise in normoxia and hypoxia, respectively.Electronic supplementary materialThe online version of this article (doi:10.1007/s00421-017-3712-z) contains supplementary material, which is available to authorized users.

Acute mountain sickness (AMS) is a neurological disorder occurring when ascending too fast, too high. Remote ischemic preconditioning (RIPC) is a noninvasive intervention protecting remote organs from subsequent hypoxic damage. We hypothesized that RIPC protects against AMS and that this effect is related to reduced oxidative stress. Fourteen subjects were exposed to 18 hours of normoxia (21% oxygen) and 18 h of normobaric hypoxia (12% oxygen, equivalent to 4500 m) on different days in a blinded, randomized order. RIPC consisted of four cycles of lower limb ischemia (5 min) and 5 min of reperfusion, and was performed immediately before the study room was entered. A control group was exposed to hypoxia (12% oxygen, n = 14) without RIPC. AMS was evaluated by the Lake Louise score (LLS) and the AMS-C score of the Environmental Symptom Questionnaire. Plasma concentrations of ascorbate radicals, oxidized sulfhydryl (SH) groups, and electron paramagnetic resonance (EPR) signal intensity were measured as biomarkers of oxidative stress. RIPC reduced AMS scores (LLS: 1.9 ± 0.4 vs. 3.2 ± 0.5; AMS-C score: 0.4 ± 0.1 vs. 0.8 ± 0.2), ascorbate radicals (27 ± 7 vs. 65 ± 18 nmol/L), oxidized SH groups (3.9 ± 1.4 vs. 14.3 ± 4.6 μmol/L), and EPR signal intensity (0.6 ± 0.2 vs. 1.5 ± 0.4 × 106) after 5 h in hypoxia (all P < 0.05). After 18 hours in hypoxia there was no difference in AMS and oxidative stress between RIPC and control. AMS and plasma markers of oxidative stress did not correlate. This study demonstrates that RIPC transiently reduces symptoms of AMS and that this effect is not associated with reduced plasma levels of reactive oxygen species.

Background: Neck pain is a frequent reason for seeking medical advice. Neuroanatomical findings suggest a close connection between the pharynx and the trapezius region. Irritation of the pharynx may induce tenderness of this area. Specific tender points, called neck reflex points (NRPs), can be identified here with high reproducibility. We hypothesized that therapeutic local anesthesia (TLA; or neural therapy, NT) in the pharyngeal region can reduce tenderness in patients with therapy-resistant neck pain. Patients and Methods: 17 consecutive female patients with chronic cervical pain and positive trapezius NRPs received bilateral injections of 0.5 ml 1% procaine into the palatine velum. The NRPs were assessed using a 3-level pain index (PI = 0, 1, or 2) before and 3-5 min after each injection. Results: We found a significant reduction in tenderness of the NRP of the trapezius region (NRP C7) immediately after TLA/NT. 30 positive NRPs were found before therapy and only 13 after therapy (p < 0.01). The average PI of the NRP C7 was 1.24 ± 0.77 before and 0.35 ± 0.59 after therapy (right side), and 1.34 ± 0.59 before and 0.59 ± 0.69 after therapy (left side). The pre- and post-therapy PI values were significantly different on both the right and left sides of the trapezius region (p < 0.01). No adverse effects were observed. Conclusions: Pharyngeal irritation may induce and maintain therapy-resistant cervical pain in patients with chronic pharyngeal disease. These patients could benefit from remote TLA/NT injections in the pharyngeal region.

SummaryBackground: Vulvodynia often occurs with unexplained vulvar pain and hyperesthesia, sexual dysfunction, and psychological disability, lacking an organic or microbiological substrate. Case Report: A 25-year-old woman with generalized, unprovoked vulvodynia for 12 years was treated repeatedly with procaine 1% for 14 sessions after she had previously had numerous unsatisfying multidisciplinary treatments. We observed a decrease in pain scores on the visual analogue scale (VAS) from initially 8-9 to presently 0-2. Injection sites were: Head's zones and trigger points of the lower abdomen, regional hypogastric ganglia, bilateral maxillary sinus, and scars of the lower jaw. No major adverse events were observed. Injections to remote sites improved symptoms more strongly than local or regional therapy. After a 3-year follow-up the patient is free of symptoms. Conclusion: Therapy with local anesthetics (TLA, neural therapy) can be a useful additional therapy in complicated cases of vulvodynia. Further studies on the underlying mechanism of injections into remote foci (interference field, stoerfeld) and the effectiveness of TLA in chronic pain syndromes should be performed.

Background: Neck reflex points (NRP) are tender soft tissue areas of the cervical region that display reflectory changes in response to chronic inflammations of correlated regions in the visceral cranium. Six bilateral areas, NRP C0, C1, C2, C3, C4 and C7, are detectable by palpating the lateral neck. We investigated the inter-rater reliability of NRP to assess their potential clinical relevance. Methods: 32 consecutive patients with chronic neck pain were examined for NRP tenderness by an experienced physician and an inexperienced medical student in a blinded design. A detailed description of the palpation technique is included in this section. Absence of pain was defined as pain index (PI) = 0, slight tenderness = 1, and marked pain = 2. Findings were evaluated either by pair-wise Cohen's kappa (ĸ) or by percentage of agreement (PA). Results: Examiners identified 40% and 41% of positive NRP, respectively (PI > 0, physician: 155, student: 157) with a slight preference for the left side (1.2:1). The number of patients identified with >6 positive NRP by the examiners was similar (13 vs. 12 patients). ĸ values ranged from 0.52 to 0.95. The overall kappa was ĸ = 0.80 for the left and ĸ = 0.74 for the right side. PA varied from 78.1% to 96.9% with strongest agreement at NRP C0, NRP C2, and NRP C7. Inter-rater agreement was independent of patients' age, gender, body mass index and examiner's experience. Conclusion: The high reproducibility suggests the clinical relevance of NRP in women.

We previously demonstrated that intratracheally administered S-ketamine inhibits alveolar fluid clearance (AFC), whereas an intravenous (IV) bolus injection had no effect. The aim of the present study was to characterize whether continuous IV infusion of S-ketamine, yielding clinically relevant plasma concentrations, inhibits AFC and whether its effect is enhanced in acute lung injury (ALI) which might favor the appearance of IV S-ketamine at the alveolar surface. AFC was measured in fluid-instilled rat lungs. S-ketamine was administered IV over 6 h (loading dose: 20 mg/kg, followed by 20 mg/kg/h), or intratracheally by addition to the instillate (75 µg/ml). ALI was induced by IV lipopolysaccharide (LPS; 7 mg/kg). Interleukin (IL)-6 and cytokine-induced neutrophil chemoattractant (CINC)-3 were measured by ELISA in plasma and bronchoalveolar lavage fluid. Isolated rat alveolar type-II cells were exposed to S-ketamine (75 µg/ml) and/or LPS (1 mg/ml) for 6 h, and transepithelial ion transport was measured as short circuit current (ISC). AFC was 27±5% (mean±SD) over 60 min in control rats and was unaffected by IV S-ketamine. Tracheal S-ketamine reduced AFC to 18±9%. In LPS-treated rats, AFC decreased to 16±6%. This effect was not enhanced by IV S-ketamine. LPS increased IL-6 and CINC-3 in plasma and bronchoalveolar lavage fluid. In alveolar type-II cells, S-ketamine reduced ISC by 37% via a decrease in amiloride-inhibitable sodium transport. Continuous administration of IV S-ketamine does not affect rat AFC even in endotoxin-induced ALI. Tracheal application with direct exposure of alveolar epithelial cells to S-ketamine decreases AFC by inhibition of amiloride-inhibitable sodium transport.