Elevation of cardiac troponins in exacerbation of chronic obstructive pulmonary disease

Objectives: To investigate the prevalence of serum troponin elevation in patients admitted to hospital with an exacerbation of chronic obstructive pulmonary disease (COPD). Methods: We examined the records of all patients admitted to hospital for treatment of COPD for serum troponin measurement, clinical features of myocardial ischaemia, oxygenation (pulse oximetry, arterial blood gas analysis), spirometry, and duration of admission. Results: Troponin elevation was observed in 58 of 235 (25%) presentations in which troponin was measured. Despite the troponin result, only seven of these 58 patients had been diagnosed with an acute coronary syndrome. New ECG evidence of ischaemia was uncommon. Patients with raised troponins tended to be older (75.7 vs 70.0 years, P = 0.001), had lower pulse oximetry (85.6% vs 89.6%, P = 0.003), were more acidotic (pH 7.34 vs 7.40, P= 0.002) and more hypercapnoeic (pCO₂ 58.0 vs 49.1, P = 0.04). There were no significant differences in serum creatine kinase. Patients with raised troponins had significantly longer admissions (5 vs 3 days, P = 0.001). Conclusions: Serum troponins are commonly raised in acute exacerbations of COPD and appear to reflect the severity of the exacerbation. In the majority of patients there is insufficient evidence to support the diagnosis of an acute coronary syndrome.     

Heel skin hyperaemia: direct compression versus vascular occlusion

Vulnerability of the heel to ulceration in bed-bound persons is related to direct pressure-induced blood flow decreases. Periodic pressure reduction is a clinical strategy to help prevent ulcers by allowing flow-repayment hyperaemia that has a magnitude and duration thought to be related to the duration of the prior interval of ischaemia. However, there are reasons to question whether effects of flow stoppages caused by direct tissue loading are similar to those because of ischaemia without superimposed direct pressure. This question was investigated by comparing posterior heel skin blood flow responses via laser-Doppler perfusion monitoring of 27 supine-lying subjects in whom blood flow was reduced by 5-min of direct heel loading on a support surface and by 5-min of ankle-cuff compression. Results showed that blood flow reductions were the same for both methods but the hyperaemia was significantly greater when flow reduction was produced by direct heel loading. This was true for ratio of peak hyperaemic flow to baseline (8.20 +/- 1.32 s versus 4.68 +/- 0.80 s, P< or =0.001), hyperaemic to baseline 3-min flow-time area ratios (4.70 +/- 0.65 s versus 1.95 +/- 0.29 s, P< or =0.001) and for total hyperaemia durations (352 +/- 39 s versus 181 +/- 14 s, P<0.001). These findings raise new questions regarding the precise physiological effects of heel and tissue loading in general, the factors that contribute to the hyperaemic response and their clinical impact and interpretation. Possible sources of the observed greater post-loading hyperaemia responses are discussed.     

Reduction of postoperative pain and swelling by ultrasound treatment: a placebo effect

Ultrasound (US) therapy is used to reduce pain and inflammation and to accelerate healing after soft tissue injury. However, there is little objective evidence of its effectiveness and the mechanisms which may cause these effects are unknown. In a placebo-controlled double-blind clinical trial we examined the contribution of placebo and massage effects in ultrasound therapy following bilateral surgical extraction of lower third molars. Four to 6 h after surgery the patients (25 per group) received either no therapy, US (0.1 W/cm2), 'mock' US with massage, 'mock' US without massage, or 'self-massage' with a dummy applicator. Facial swelling, trismus, serum C-reactive protein, serum cortisol, pain and anxiety were measured 24 h postoperatively. The results showed that the beneficial analgesic and anti-inflammatory effects of US therapy were placebo-mediated, with maximum effect in the placebo ('mock' US) group without circular massaging with the applicator). Self-massage by the patient produced no significant effect. This placebo action was independent of changes in serum cortisol or patient anxiety state. US therapy can significantly reduce postoperative morbidity, but by placebo-mediated mechanisms which are unrelated to the US itself.     

Relationship between decreased function and O2 consumption caused by cyclic GMP in cardiac myocytes and L-type calcium channels

We tested the hypothesis that part of the decreased function and metabolism caused by cyclic guanosine monophosphate (GMP) in beating cardiac myocytes is related to inhibition of L-type calcium channels. The steady state oxygen consumption (VO₂) of a suspension of ventricular myocytes isolated from hearts of New Zealand white rabbits was measured using oxygen electrodes. Cellular cyclic GMP levels were determined by radioimmunoassay. Cell shortening was measured with a video edge detector. The VO₂ was obtained after: (1) adding sodium nitroprusside (NP 10^{?8,?6, ?4} M), (2) pretreatment by BAY K8644 10^?5 M (BAY, L-type calcium channel activator), nifedipine 10^?4 M (NF, L-type calcium channel blocker) or forskolin 10^?7 M (FK, adenylate cyclase activator), then adding NP10^?8,?6,?4 M, (3) pretreatment with both FK 10^?7 M and NF 10^?4 M and subsequently adding NP 10^{?8, ?6, ?4} M. NP 10^?4 M decreased VO₂ from 707±34 to 410±13 (nl O₂/min per 10⁵ myocytes), decreased the percentage of shortening (Pcs) from 5.7±0.6 to 3.7±0.5 and the rate of shortening (Rs) from 65.5±4.5 (µm/s) to 46.2±5.5. NP 10^?4 M also increased cyclic GMP from 264±70 (fmol/10⁵ myocytes) to 760±283. Both BAY and FK increased VO₂, Pcs and Rs without changing cyclic GMP. NF decreased Pcs, Rs and VO₂. Similar metabolic and functional effects of NP were observed with pretreatment with these agents separately, compared to NP alone, and the elevation of cyclic GMP level was not different from the control group. With FK alone, NP 10^?4 M decreased VO₂ by 51%, Pcs by 44% and Rs by 39%. In the presence of both FK and NF, the negative effects of NP were diminished significantly. NP 10^?4 M decreased VO₂ by 37%, Pcs by 25% and Rs 20%. Thus, in beating cardiac myocytes, the negative metabolic and functional effects of cyclic GMP were related to inhibition on L-type calcium channels only when adenylate cyclase was stimulated.     

Diagnostic utility of invasive EEG for epilepsy surgery: Indications,modalities, and techniques

Many patients with medically refractory epilepsy now undergo successful surgery based on noninvasive diagnostic information, but intracranial electroencephalography (IEEG) continues to be used as increasingly complex cases are considered surgical candidates. The indications for IEEG and the modalities employed vary across epilepsy surgical centers; each modality has its advantages and limitations. IEEG can be performed in the same intraoperative setting, that is, intraoperative electrocorticography, or through an independent implantation procedure with chronic extraoperative recordings; the latter are not only resource intensive but also carry risk. A lack of understanding of IEEG limitations predisposes to data misinterpretation that can lead to denying surgery when indicated or, worse yet, incorrect resection with adverse outcomes. Given the lack of class 1 or 2 evidence on IEEG, a consensus‐based expert recommendation on the diagnostic utility of IEEG is presented, with emphasis on the application of various modalities in specific substrates or locations, taking into account their relative efficacy, safety, ease, and incremental cost‐benefit. These recommendations aim to curtail outlying indications that risk the over‐ or underutilization of IEEG, while retaining substantial flexibility in keeping with most standard practices at epilepsy centers and addressing some of the needs of resource‐poor regions around the world.     

Automated alignment of perioperative MRI scans: A technical note and application in pediatric epilepsy surgery

Conventional image registration utilizing brain voxel information may be erroneous in a neurosurgical setting due to pathology and surgery‐related anatomical distortions. We report a novel application of an automated image registration procedure based on skull segmentation for magnetic resonance imaging (MRI) scans acquired before, during and after surgery (i.e., perioperative). The procedure was implemented to assist analysis of intraoperative brain shift in 11 pediatric epilepsy surgery cases, each of whom had up to five consecutive perioperative MRI scans. The procedure consisted of the following steps: (1) Skull segmentation using tissue classification tools. (2) Estimation of rigid body transformation between image pairs using registration driven by the skull segmentation. (3) Composition of transformations to provide transformations between each scan and a common space. The procedure was validated using locations of three types of reference structural landmarks: the skull pin sites, the eye positions, and the scalp skin surface, detected using the peak intensity gradient. The mean target registration error (TRE) scores by skull pin sites and scalp skin rendering were around 1 mm and <1 mm, respectively. Validation by eye position demonstrated >1 mm TRE scores, suggesting it is not a reliable reference landmark in surgical scenarios. Comparable registration accuracy was achieved between opened and closed skull scan pairs and closed and closed skull scan pairs. Our procedure offers a reliable registration framework for processing intrasubject time series perioperative MRI data, with potential of improving intraoperative MRI‐based image guidance in neurosurgical practice. Hum Brain Mapp 37:3530–3543, 2016. © 2016 Wiley Periodicals, Inc.     

Carbon dioxide contributes to the beneficial effect of pressurization in a portable hyperbaric chamber at high altitude

Regional cerebral oxygenation (rSO2) and peripheral oxygen saturation (SpO2) have been studied in subjects inside a portable hyperbaric chamber at altitude during pressurization. The effects of the accumulation of carbon dioxide within the chamber on rSO2 and SpO2 have also been investigated. Three studies of cerebral regional oxygenation were undertaken, using near-IR spectroscopy, in subjects who had ascended to 3475 m in the Alps, 4680 m in the Andes or 5005 m in the Himalayas. At 3475 m and 5005 m the effects of the removal of inspired carbon dioxide by a soda lime scavenger were also studied. On pressurization of the chamber to 19.95 kPa, inspired carbon dioxide rose within the chamber from 0.03% (0.06 kPa) ambient to over 1% (1.3 kPa). At 5005 m, SpO2 rose from a baseline of 79.5% (S.D. 4.5%) to 95.9% (2.0%) (P<0.0001), and cerebral rSO2 rose from 64.6% (3.4%) to 69.4% (3.6%) (P<0.0001). The introduction of a soda lime CO2 scavenger into the breathing circuit resulted in a drop in SpO2 from 95.9% (2.03%) to 93.6% (2.07%) (P<0.001) and a fall in rSO2 from 69.4% (3.64%) to 68.5% (3.5%) (P<0.01). Chamber pressure was maintained throughout at 19.95 kPa. Similar changes were seen at the other altitudes. Cerebral rSO2 increased rapidly following pressurization at all three altitudes. Scavenging of inspired carbon dioxide was associated with a significant fall in cerebral rSO2 and SpO2, and we estimate that the contribution of carbon dioxide may account for up to one-third of the beneficial effect of the portable hyperbaric chamber.