Acute fluid shifts influence the assessment of serum vitamin D status in critically ill patients

Introduction Recent reports have highlighted the prevalence of vitamin D deficiency and suggested an association with excess mortality in critically ill patients. Serum vitamin D concentrations in these studies were measured following resuscitation. It is unclear whether aggressive fluid resuscitation independently influences serum vitamin D. Methods Nineteen patients undergoing cardiopulmonary bypass were studied. Serum 25(OH)D3, 1α,25(OH)2D3, parathyroid hormone, C-reactive protein (CRP), and ionised calcium were measured at five defined timepoints: T1 - baseline, T2 - 5 minutes after onset of cardiopulmonary bypass (CPB) (time of maximal fluid effect), T3 - on return to the intensive care unit, T4 - 24 hrs after surgery and T5 - 5 days after surgery. Linear mixed models were used to compare measures at T2-T5 with baseline measures. Results Acute fluid loading resulted in a 35% reduction in 25(OH)D3 (59 ± 16 to 38 ± 14 nmol/L, P < 0.0001) and a 45% reduction in 1α,25(OH)2D3 (99 ± 40 to 54 ± 22 pmol/L P < 0.0001) and i(Ca) (P < 0.01), with elevation in parathyroid hormone (P < 0.0001). Serum 25(OH)D3 returned to baseline only at T5 while 1α,25(OH)2D3 demonstrated an overshoot above baseline at T5 (P < 0.0001). There was a delayed rise in CRP at T4 and T5; this was not associated with a reduction in vitamin D levels at these time points. Conclusions Hemodilution significantly lowers serum 25(OH)D3 and 1α,25(OH)2D3, which may take up to 24 hours to resolve. Moreover, delayed overshoot of 1α,25(OH)2D3 needs consideration. We urge caution in interpreting serum vitamin D in critically ill patients in the context of major resuscitation, and would advocate repeating the measurement once the effects of the resuscitation have abated.

Vascular access, fluid resuscitation, and blood transfusion in pediatric trauma.

Trauma care in the general population has largely become protocol-driven, with an emphasis on fast and efficient treatment, good team communication at all levels of care including prehospital care, initial resuscitation, intensive care, and rehabilitation. Most available literature on trauma care has focused on adults, allowing the potential to apply concepts from adult care to pediatric care. But there remain issues that will always be specific to pediatric patients that may not translate from adults. Several new devices such as intraosseous (IO) needle systems and techniques such as ultrasonography to cannulate central and peripheral veins have become available for integration into our pre-existing trauma care system for children. This review will focus specifically on the latest techniques and evidence available for establishing intravenous access, rational approaches to fluid resuscitation, and blood product transfusion in the pediatric trauma patient.

Assessment of resuscitation skills of Foundation Year 1 hospital doctors

An objective and subjective assessment of performance of CPR by 38 foundation year 1 doctors in a major teaching hospital. The study clearly demonstrated that males are more effective than females, BMI has a significant effect on chest compression depth and that females, especially those with a BMI of <24 are more effective at CPR when using a 15:2 rather than a 30:2 ratio of chest compressions to ventilations.

The Utility of Cardiopulmonary Exercise Testing in Difficult Asthma

Background: Unexplained persistent breathlessness in patients with difficult asthma despite multiple treatments is a common clinical problem. Cardiopulmonary exercise testing (CPX) may help identify the mechanism causing these symptoms, allowing appropriate management.

Methods: This was a retrospective analysis of patients attending a specialist-provided service for difficult asthma who proceeded to CPX as part of our evaluation protocol. Patient demographics, lung function, and use of health care and rescue medication were compared with those in patients with refractory asthma. Medication use 6 months following CPX was compared with treatment during CPX.

Results: Of 302 sequential referrals, 39 patients underwent CPX. A single explanatory feature was identified in 30 patients and two features in nine patients: hyperventilation (n = 14), exercise-induced bronchoconstriction (n = 8), submaximal test (n = 8), normal test (n = 8), ventilatory limitation (n = 7), deconditioning (n = 2), cardiac ischemia (n = 1). Compared with patients with refractory asthma, patients without “pulmonary limitation” on CPX were prescribed similar doses of inhaled corticosteroid (ICS) (median, 1,300 µg [interquartile range (IQR), 800-2,000 µg] vs 1,800 µg [IQR, 1,000-2,000 µg]) and rescue oral steroid courses in the previous year (median, 5 [1-6] vs 5 [1-6]). In this group 6 months post-CPX, ICS doses were reduced (median, 1,300 µg [IQR, 800-2,000 µg] to 800 µg [IQR, 400-1,000 µg]; P < .001) and additional medication treatment was withdrawn (n = 7). Patients with pulmonary limitation had unchanged ICS doses post CPX and additional therapies were introduced.

Conclusions: In difficult asthma, CPX can confirm that persistent exertional breathlessness is due to asthma but can also identify other contributing factors. Patients with nonpulmonary limitation are prescribed inappropriately high doses of steroid therapy, and CPX can identify the primary mechanism of breathlessness, facilitating steroid reduction.

Cardiopulmonary function in two human disorders of the hypoxia-inducible factor (HIF) pathway: von Hippel-Lindau disease and HIF-2 alpha gain-of-function mutation

The hypoxia-inducible factors (HIFs; isoforms HIF-1 alpha, HIF-2 alpha, HIF-3 alpha) mediate many responses to hypoxia. Their regulation is principally by oxygen-dependent degradation, which is initiated by hydroxylation of specific proline residues followed by binding of von Hippel-Lindau (VHL) protein. Chuvash polycythemia is a disorder with elevated HIF. It arises through germline homozygosity for hypomorphic VHL alleles and has a phenotype of hematological, cardiopulmonary, and metabolic abnormalities. This study explores the phenotype of two other HIF pathway diseases: classic VHL disease and HIF-2 alpha gain-of-function mutation. No cardiopulmonary abnormalities were detected in classic VHL disease. HIF-2 alpha gain-of-function mutations were associated with pulmonary hypertension, increased cardiac output, increased heart rate, and increased pulmonary ventilation relative to metabolism. Comparison of the HIF-2 alpha gain-of-function responses with data from studies of Chuvash polycythemia suggested that other aspects of the Chuvash phenotype were diminished or absent. In classic VHL disease, patients are germline heterozygous for mutations in VHL, and the present results suggest that a single wild-type allele for VHL is sufficient to maintain normal cardiopulmonary function. The HIF-2 alpha gain-of-function phenotype may be more limited than the Chuvash phenotype either because HIF-1 alpha is not elevated in the former condition, or because other HIF-independent functions of VHL are perturbed in Chuvash polycythemia.-Formenti, F., Beer, P. A., Croft, Q. P. P., Dorrington, K. L., Gale, D. P., Lappin, T. R. J., Lucas, G. S., Maher, E. R., Maxwell, P. H., McMullin, M. F., O'Connor, D. F., Percy, M. J., Pugh, C. W., Ratcliffe, P. J., Smith, T. G., Talbot, N. P., Robbins, P. A. Cardiopulmonary function in two human disorders of the hypoxia-inducible factor (HIF) pathway: von Hippel-Lindau disease and HIF-2 alpha gain-of-function mutation. FASEB J. 25, 2001-2011 (2011). www.fasebj.org