Venous air-embolism (VAE) potentially catastrophic complication surgery. Based on previous data using changes in end-tidal nitrogen as an indicator of VAE, we surmised that changes in end-tidal argon (EtAr) may be an indicator of VAE. We sought to determine if a commercial mass-spectrometer (PCT Proline Analyzer 61700-8 Class 85, Ametek, Pittsburgh, PA 15238) could be used to detect changes in EtAr in an invitro model. A Drager Apollo™ (Drager, Lubeck, Germany) anesthesia machine was used to ventilate a dummy lung (2 L bag) with a minute ventilation of 6 L/min in 100% oxygen. The quadrupole mass-spectrometer (sampling at 0.0004 atm-cc/sec) was attached to the end-tidal inlet of the machine. Room air (1–60 mL) was injected into the dummy lung to simulate VAE. A strong baseline ion-current (1.2 × 10−12 amps) of argon was noted. Due to this contamination we were unable to detect “VAE” events of injected air. Argon represents approximately 0.93% of room air, or about 9300 parts per million (ppm). We detected about 2000 ppm argon in medical-grade oxygen (or 0.2%), limiting our ability to detect changes in EtAr. This is a USP-accepted contaminant, rendering this technology is insensitive for early, rapid detection of VAE. We assumed medical grade oxygen was pure and were surprised to learn otherwise. We want to share this likely largely unknown finding with the medical community.
Hypotension in patients under general anesthesia is prevalent and causes unfavorable outcomes. Carotid intima-media thickness (CIMT) is a surrogate marker for atherosclerosis and useful for evaluating the risk of cardiovascular diseases. We investigated the usefulness of preoperative CIMT measurement as a predictor of post-induction hypotension (PIH). The ultrasonographic measurement of CIMT was performed preoperatively on 82 patients scheduled for elective surgery under general anesthesia in a prospective, observational study. Mean blood pressure (MBP) was recorded before induction. Hypotension was defined as a 20% decrease in MBP from baseline. The ultrasonographic measurement of CIMT was unsuccessful in 2 (2.43%) patients, leaving 80 patients for analyses. Hypotension developed in 41 patients. CIMT was higher in the patient group with PIH than in the group without PIH (p < 0.001). There was statistically significant correlation between MBP decrease after induction and CIMT (r = 0.529, p < 0.0001). CIMT correlated positively with age (r = 0.739, p < 0.0001). The area under curve for CIMT was 0.753 [95% confidence interval (CI) 0.642–0.863]. The optimal cutoff value of CIMT was 0.65 mm with a sensitivity of 75.6% and a specificity of 74.4%. CIMT was an independent predictor of PIH after adjusting other factors with an odds ratio of 1.833 (95% CI 1.23–2.72; p = 0.003). The ultrasonographic imaging and measurement of CIMT can reliably predict hypotension with a 0.65-mm threshold level. We believe that the ultrasonographic measurements of CIMT may be included in point-of-care application in anesthesiology.
Neurodevelopment of newborns can be impaired by many “stressful” events, with long-term consequences: pain, discomfort, hypoxia, even maternal stress has a negative impact. Experimental and clinical studies have shown that stress and/or pain during the perinatal period could negatively influence the long-term programming of the hypothalamic–pituitary–adrenal (HPA) axis, which could account for abnormal responses to stress later in life, and may increase the risk of developing metabolic and cardiovascular diseases in adulthood [1, 2]. Perinatal stressful events are probably related to impaired autonomic nervous system (ANS) activity and a decreased parasympathetic activity in particular, which can easily be measured by modern monitors using e.g. heart rate variability analysis (HRV) [3, 4]. The University Hospital of Lille, France, has been part of several clinical studies evaluating how an HRV based index, the Analgesia Nociception Index (ANI, MDMS, Loos, France) could help evaluate the analgesia/nociception balance during general anesthesia [5] but also how ANI evidenced a decreased parasympathetic activity during a procedural pain in children [6].
A similar HRV evaluation of the ANS has been adapted to the specific case of newborns: the Newborn Infant Parasympathetic Evaluation (NIPE, MDMS, France) reflects continuously and non-invasively the parasympathetic tone, which has been shown to decrease significantly in newborn infants after a painful surgical procedure [7] or after instrumental assisted delivery [8]. Even if the clinical benefit of increasing the parasympathetic activity cannot be fully grasped yet, we showed that NIPE was significantly higher after facilitated tucking [9] or skin to skin contact in neonates [10]. Continuous assessment of comfort is quite challenging in the newborn infant, especially in neonatal intensive care units. Adapted scales, such as the EDIN [11], are routinely used in NICU to assess pain/discomfort at the bedside. However, EDIN is usually measured every 4 to 8 h in clinical practice, whereas NIPE can be used continuously as a monitoring tool to alert healthcare providers in case of stress or pain. When used in NICU, the nurses have to be aware that NIPE is highly sensitive to environmental factors such as noise, light, feeding and sleep status, which should be controlled for a reliable interpretation of any NIPE change.
In this issue, Valencia-Ramos et al. used the NIPE measurements in parallel with the COMFORT behavioral scale (CBS) during nebulization in order to quantify pain and/or discomfort related to the use of two different nebulizers in children with bronchiolitis. They observed significant variations in CBS and NIPE during nebulization. Moreover, CBS variations were significantly different between the two nebulizers whereas NIPE showed similar reactions of the ANS to nebulization, and didn’t show any superiority of one nebulizer versus the other. These results also underline the fact that HRV analysis is independent from heart rate variations which are not specific of any given factor in the context of a Pediatric Intensive Care Unit (PICU). Variations of HRV measurements should be taken as information per se, as clinical assessment and behavioral scales—even if clinically validated—cannot easily be related to a given status of the ANS, that is either a parasympathetic prevalence (comfort) or a sympathetic activation (pain/stress). Only well conducted, prospective randomized clinical trials will show the benefit of “optimizing” the state of the ANS. The presented observational study illustrates only too well the difficulties clinicians are confronted to when “measuring” the well-being of their patients. As stated in the discussion chapter, NIPE and CBS were not evaluated in the same way: CBS was evaluated before (T1), during (T2) and after (T3) nebulization whereas NIPE variations were only measured in terms of absolute magnitude during the whole procedure. Such a difference in the way data were collected could explain in itself the lack of correlation between both.
Notes
Compliance with ethical standards
Conflict of interest
JDJ is shareholders of and scientific consultant for Mdoloris Medical Systems (that commercializes NIPE monitor). LS reports no conflict of interest.
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