Monitoring cerebral oxygen saturation during cardiopulmonary bypass using near-infrared spectroscopy: the relationships with body temperature and perfusion rate

During cardiopulmonary bypass (CPB) because of weak arterial pulsation, near-IR spectroscopy (NIRS) is almost the only available method to monitor cerebral oxygenation noninvasively. Our group develops a NIRS oximeter to monitor regional cerebral oxygenation especially its oxygen saturation (rScO2). To achieve optimal coupling between the sensor and human brain, the distances between the light source and the detectors on it are properly chosen. The oximeter is calibrated by blood gas analysis, and the results indicate that its algorithm is little influenced by either background absorption or overlying tissue. We used it to measure the rScO2 of 15 patients during CPB. It is shown that rScO2 is negatively correlated with body temperature and positively with perfusion rate. There are two critical stages during CPB when rScO2 might be relatively low: one is the low-perfusion-rate stage, the other is the early rewarming stage. During cooling, the changes of total hemoglobin concentration (C(tHb)) compared with its original value is also monitored. It is shown that C(tHb) decreases to a small extent, which may mainly reflect cerebral vasoconstriction induced by cooling. All these results indicate that NIRS can be used to monitor cerebral oxygenation to protect cerebral tissue during CPB.     

Monitoring regional cerebral oxygen saturation using near-infrared spectroscopy during pulsatile hypothermic cardiopulmonary bypass in a neonatal piglet model

Impairment of cerebral oxygenation in neonates and infants after hypothermic nonpulsatile cardiopulmonary bypass (CPB) support is well documented. The objectives of this study were: 1) using a neonatal piglet model to continuously monitor the regional cerebral oxygen saturation (rSO2) by near-infrared spectroscopy during pulsatile hypothermic CPB; and 2) to quantify the pulsatile flow in terms of energy equivalent pressure (EEP). After initiation of CPB, all piglets (n = 5) were subjected to 15 minutes of core cooling, reducing the rectal temperature to 25 degrees C, followed by 60 minutes of hypothermic CPB, then 10 minutes of cold reperfusion, and 30 minutes of rewarming. During CPB, mean arterial pressures (MAPs) and pump flow rates were maintained at 40-45 mm Hg and 150 ml/kg/min, respectively. During normothermic CPB, the rSO2 was significantly increased, compared with the pre-CPB level (56.8 +/- 5.2% vs. 41.8 +/- 5.5%, p < 0.01). At the end of cooling, the rSO2 level was 76.8 +/- 8.6% (p < 0.001 vs. pre-CPB). After 60 minutes of hypothermic CPB and 30 minutes of rewarming, the rSO2 level was decreased to 38.6 +/- 4.2%, which was not significantly different compared with the pre-CPB level. The average increase in pressure (from MAP to EEP) was 5 +/- 1%, and the average increase in extracorporeal circuit pressure (from ECCP to EEP) was 13 +/- 2%. This extra pressure may help to provide better regional cerebral oxygen saturation. During pulsatile CPB, there was no rSO2 deficiency in this high flow model. Near-infrared spectroscopy responded well to changes in rSO2 during different stages of these experiments and might be a helpful tool for intraoperative monitoring.     

Shift of motor activation areas during recovery from hemiparesis after cerebral infarction: a longitudinal study with near-infrared spectroscopy

Motor functional recovery after stroke may be attributable to cerebral reorganization. We used near-infrared spectroscopy, which measures non-invasively the changes in oxy- and deoxy-hemoglobin concentrations in response to neural activation, for monitoring cerebral activation in stroke patients, and investigated the longitudinal changes in functional laterality of activations in the primary sensorimotor cortex during unilateral audio-paced (1 Hz) hand movement. We examined five ischemic stroke patients (4 females and 1 male, 52-67 years old) with mild to moderate hemiparesis at acute stages and chronic stages at least 1 month later. Normal subjects (3 females and 2 males, 47-63 years old) were also included. Unilateral hand movement activated predominantly the contralateral primary sensorimotor cortex in the normal subjects and the stroke patients when they moved unaffected hand. Affected hand movements activated bilateral sensorimotor cortices early after stroke (< 25 days of stroke onset), whereas the activation pattern returned toward normal at later periods (> 35 days). The contralaterality index (0.34 +/- 0.12 in normal control) was reduced at early periods (0.00 +/- 0.03, p < 0.01) after stroke, and returned to normal (0.35 +/- 0.24) as motor function recovered. These findings suggest that a transient increase in motor activation in the ipsilateral intact hemisphere within 1 month may play an important role in the recovery from motor dysfunction after stroke.     

Quantitative assessment of cerebral autoregulation from transcranial Doppler pulsatility: a computer simulation study

Transcranial Doppler (TCD) ultrasonography is largely used today to achieve non-invasive assessment of cerebral autoregulation and cerebrovascular reactivity in neurosurgical patients. Recent experimental and clinical studies suggest that not only the pattern of mean velocity, but also velocity pulse amplitude alterations during changes in cerebral perfusion pressure (CPP) contain information on autoregulation status. The aim of this work is to investigate the relationship between cerebral autoregulation and TCD pulsatility by means of a comprehensive mathematical model of intracranial dynamics and cerebrovascular regulation. Simulation results, performed using different values of the most important clinical parameters of the model (autoregulation strength, cerebrospinal fluid (CSF) outflow resistance and intracranial elastance coefficient) show that velocity pulse amplitude increases with a reduction in CPP in patients with intact autoregulation, whereas changes in velocity pulsatility are modest in patients with weak autoregulation. Finally, velocity pulse amplitude decreases during a CPP reduction in patients with impaired autoregulation. Moreover, the relationship between the velocity pulse amplitude changes and autoregulation strength is almost linear in a wide range of CPP values, and is scarcely affected by changes in CSF circulation and intracranial elasticity. Starting from these results, we suggest a new quantitative index to assess autoregulation strength, i.e. G(aut)% = (s-b)/a, where G(aut)% is autoregulation strength (100% means intact autoregulation, 0% means impaired autoregulation), a approximately -0.03; b approximately 1.5 and s is the slope of the relationship ' percentage changes of velocity pulse amplitude to arterial pressure pulse amplitude vs. CPP changes'.     

Impaired cerebral and systemic hemodynamics under cognitive load in young hypotensives: a transcranial Doppler study

Reduced sympathetic outflow and deficits in cerebral hemodynamics have been considered as possible factors mediating the impaired cognitive performance in essential hypotension. However, the relationship between systemic blood pressure (BP), cerebral blood flow and cognitive functioning is still poorly understood. The present study was aimed at clarifying the physiological processes underlying cerebral and systemic hemodynamics in young hypotensives during cognitive engagement. Doppler sonography blood flow velocities in both middle cerebral arteries were measured from 17 hypotensives and 15 normotensives during a working memory task. Impedance cardiographic and BP measures were also recorded continuously. Lower increases in systolic and diastolic BP were observed in hypotensives. However, no evidence of lower sympathetic control was found for this group, as assessed by pre-ejection period. Flow velocity in middle cerebral arteries showed a lower increase in hypotensives throughout the task. Moreover, significant positive correlations between BP changes and blood flow velocities in middle cerebral arteries during the task were obtained for this group only, suggesting a less effective cerebral autoregulation. No difference was found between groups in task performance. Results suggest that during cognitive challenge hypotensives show impaired hemodynamic adjustments, both central and peripheral. However, such alterations do not directly affect cognitive performance, at least under moderate cognitive load.     

Active regulation of cerebral venous tone: simultaneous arterial and venous transcranial Doppler sonography during a Valsalva manoeuvre

The aim of this study was to analyse the cerebral venous outflow in relation to the arterial inflow during a Valsalva manoeuvre (VM). In 19 healthy volunteers (mean age 24.1 ± 2.6 years), the middle cerebral artery (MCA) and the straight sinus (SRS) were insonated by transcranial Doppler sonography. Simultaneously the arterial blood pressure was recorded using a photoplethysmographic method. Two VM of 10 s length were performed per participant. Tracings of the variables were then transformed to equidistantly re-sampled data. Phases of the VM were analysed regarding the increase of the flow velocities and the latency to the peak. The typical four phases of the VM were also found in the SRS signal. The relative flow velocity (FV) increase was significantly higher in the SRS than in the MCA for all phases, particularly that of phase IV (p < 0.01). Comparison of the time latency of the VM phases of the MCA and SRS only showed a significant difference for phase I (p < 0.01). In particular, there was no significant difference for phase IV (15.8 ± 0.29 vs. 16.0 ± 0.28 s). Alterations in venous outflow in phase I are best explained by a cross-sectional change of the lumen of the SRS, while phases II and III are compatible with a Starling resistor. However, the significantly lager venous than the arterial overshoot in phase IV may be explained by the active regulation of the venous tone.     

Enhancing effect of cerebral blood volume by mild exercise in healthy young men: a near-infrared spectroscopy study

A mechanism by which exercise improves brain function may be attributed to increase in cerebral blood volume (CBV) with physical activity. However, the exact exercise intensity that influences CBV is still uncertain. To clarify this issue, 10 healthy young male participants were asked to perform a graded cycling exercise to the point of exhaustion while their prefrontal cortex CBVs are being monitored using near-infrared spectroscopy. Overall responsive cerebral oxygenation showed a non-linear pattern with three distinct phases. The CBV-threshold (CBVT), an event where rapid oxygenation takes place, occurred at approximately 42% of the V O2max. The CBVT preceded the lactate threshold (LT), which was at approximately 55% of the V O2max. The V O2max was not predictive of the CBVT in among the subjects. Our results indicate that oxygenation of the prefrontal cortex increases during graded cycling even at exercise intensities below the LT, suggesting the potential role of mild exercise in enhancing CBV.     

Deactivation and activation of left frontal lobe during and after low-frequency repetitive transcranial magnetic stimulation over right prefrontal cortex: A near-infrared spectroscopy study

The effects of low-frequency repetitive transcranial magnetic stimulation (rTMS) over the right frontal lobe on the function of the left frontal lobe were examined by near-infrared spectroscopy (NIRS) in eleven healthy subjects. rTMS applied 5 cm anterior to the motor cortex at 1 Hz and approximately 50% of the motor threshold intensity (MT) for 60 s resulted in a significantly larger decrease in the concentration of oxygenated hemoglobin ([oxy-Hb]) during the stimulation period followed by a significantly larger increase in [oxy-Hb] and a smaller decrease in the concentration of deoxygenated hemoglobin ([deoxy-Hb]) during the poststimulation baseline period than sham stimulation. These findings are interpreted as demonstrating the deactivation and activation of the left frontal cortex during and after rTMS of the right frontal cortex, respectively. If replicated in depressed patients, NIRS can be employed for monitoring rTMS effects as brain [Hb] changes in vivo, and may be helpful for determining therapeutic parameters of rTMS for individual patients.     

Tibolone, oral or transdermal hormone replacement and colour Doppler analysis: a prospective, randomised pilot study

Objective: To compare the plasma thromboxane, the plasma viscosity and the Doppler flow modifications induced by tibolone and by oral or transdermal continuous combined hormone replacement therapy. Methods: Forty-two post-menopausal patients underwent either on: oral daily treatment with tibolone (2.5 mg) (Group I; n=14); or continuous oral administration of 0.625 mg conjugated equine estrogens + medroxyprogesterone 5 mg per day (Group II; n=14); or continuous estradiol transdermal supplementation, at a dose of 50 μg per day, + medroxyprogesterone 5 mg per day (Group III; n=14). The duration of the study was 6 months and the patients were submitted to transvaginal ultrasonographic evaluation of pelvic organs; Doppler analysis of the uterine, internal carotid and ophthalmic arteries; thromboxane and plasma viscosity assays in basal condition, and at 1, 3 and 6 months from the beginning of the study. Results: Although the endometrial thickness increased significantly, there were no cases in which it exceeded the normal range (≤5 mm). In all the three groups, the pulsatility index of the uterine, internal carotid and ophthalmic arteries significantly decreased during the therapy showing a reduced impedance since the first month of treatment. Similar variations were observed for the peak systolic blood flow velocity of the internal carotid and ophthalmic arteries. Hormone replacement therapy and tibolone induced a deep, significant and rapid decrease in plasma thromboxane and plasma viscosity levels. Conclusions: Hormone replacement therapy and tibolone seem to have beneficial effects on vascular and hemorrheological parameters.     

Changes in hemoglobin concentration in the lateral occipital regions during shape recognition: a near-infrared spectroscopy study

By using near-infrared spectroscopy (NIRS), we measured the changes in the oxygenated and deoxygenated hemoglobin (oxy-Hb and deoxy-Hb, respectively) concentrations while performing visual tasks. We conducted experiments using two tasks: a shape recognition task and a position recognition task. It was found that the oxy-Hb concentration was substantially higher in the lateral occipital regions during shape recognition than during position recognition. The changes in the oxy-Hb concentration were considered to reflect the activation difference between the two tasks. No difference was observed in the oxy-Hb concentration during the memorization of shape and memorization of position. The deoxy-Hb concentration was different between the two tasks only when different stimuli were used but not when identical stimuli were used. In addition, it was suggested that the deoxy-Hb concentration is more sensitive to activation difference between the hemispheres and the activation at some regions. Measurements of the oxy-Hb and deoxy-Hb concentrations would reflect different aspects of cortical activations. The present results showed that measuring the oxy-Hb and deoxy-Hb concentrations separately can differentiate the activation of the regional cortical functions.     

Brain perfusion monitoring with frequency-domain and continuous-wave near-infrared spectroscopy: a cross-correlation study in newborn piglets

The newborn piglet brain model was used to correlate continuous-wave (CW) and frequency-domain (FD) near-infrared spectroscopy. Six ventilated and instrumented newborn piglets were subjected to a series of manipulations in blood oxygenation with the effects on brain perfusion known to be associated with brain hypoxia-ischaemia. An excellent agreement between the CW and FD was demonstrated. This agreement improved when the scattering properties (determined by the FD device) were employed to calculate the differential pathlength factor, an important step in CW data processing.     

Time courses of brain activation and their implications for function: a multichannel near-infrared spectroscopy study during finger tapping

The time courses of brain activation were monitored during a finger tapping task using multichannel near-infrared spectroscopy with a time resolution of 0.1s in 30 healthy volunteers. Task-induced brain activations were demonstrated as significant increases in oxygenated hemoglobin concentration ([oxy-Hb]) in a broad area around the motor cortex and significant decreases in deoxygenated hemoglobin concentration ([deoxy-Hb]) in a more restricted area, with a large degree of activation in the contralateral hemisphere. The time courses of the [oxy-Hb] changes varied depending on channel location: sustained activation across the task period in the motor cortex, transient activation during the initial segments of the task period in the somatosensory cortex, and accumulating activation along the task period in the frontal lobe. These characteristics are assumed to reflect the functional roles of the brain structures during the task period, that is, the execution, sensory monitoring, and maintenance of finger tapping.     

Auditory brainstem response in postmenopausal women treated with hormone replacement therapy: a pilot study

OBJECTIVE: To research the nongenital audiological target for gonadal steroids in postmenopausal women who are treated with hormone replacement therapy. DESIGN: Fifty postmenopausal volunteers were treated with hormone replacement therapy. Women with an intact uterus had sequential weekly transdermal estradiol plus nomegestrole acetate 5 mg orally for 12 days per month or a continuous daily oral dose of conjugated estrogen 0.625 mg and medroxyprogesterone acetate 5 mg tablet. Eighteen surgically postmenopausal women received a weekly transdermal estradiol system. Twenty-five postmenopausal volunteers-5 with a natural menopause and 10 with a surgical menopause-and 20 premenopausal normally cycling women were used as a control group. Each woman performed auditory brainstem response by auditory-evoked potentials for waves I, III, and V and for interpeak I-III, I-V, and III-V intervals. RESULTS: Women who were treated with hormone replacement therapy showed wave latencies and interpeak latencies shorter than those for postmenopausal women in the control group (p < or = 0.05), overlapping those of the premenopausal women (p > 0.05). Women who were treated with estrogen replacement therapy showed shorter time latencies than those treated with combined hormone replacement therapy (p < or = 0.05). CONCLUSIONS: Our data suggest that fluctuating hormone levels cause changes in auditory brain-stem response waves, even if the exact mechanism of activity of the gonadal steroids is not clear. However, we believe that estrogen may influence the neuronal plasticity, the metabolic levels of neurotransmitters, and thus the neuronal conduction time into the audiological system.     

Slow oscillating transcranial direct current stimulation during sleep has a sleep‐stabilizing effect in chronic insomnia: a pilot study

Recent evidence suggests that lack of slow‐wave activity may play a fundamental role in the pathogenesis of insomnia. Pharmacological approaches and brain stimulation techniques have recently offered solutions for increasing slow‐wave activity during sleep. We used slow (0.75 Hz) oscillatory transcranial direct current stimulation during stage 2 of non‐rapid eye movement sleeping insomnia patients for resonating their brain waves to the frequency of sleep slow‐wave. Six patients diagnosed with either sleep maintenance or non‐restorative sleep insomnia entered the study. After 1 night of adaptation and 1 night of baseline polysomnography, patients randomly received sham or real stimulation on the third and fourth night of the experiment. Our preliminary results show that after termination of stimulations (sham or real), slow oscillatory transcranial direct current stimulation increased the duration of stage 3 of non‐rapid eye movement sleep by 33 ± 26 min (P = 0.026), and decreased stage 1 of non‐rapid eye movement sleep duration by 22 ± 17.7 min (P = 0.028), compared with sham. Slow oscillatory transcranial direct current stimulation decreased stage 1 of non‐rapid eye movement sleep and wake time after sleep‐onset durations, together, by 55.4 ± 51 min (P = 0.045). Slow oscillatory transcranial direct current stimulation also increased sleep efficiency by 9 ± 7% (P = 0.026), and probability of transition from stage 2 to stage 3 of non‐rapid eye movement sleep by 20 ± 17.8% (P = 0.04). Meanwhile, slow oscillatory transcranial direct current stimulation decreased transitions from stage 2 of non‐rapid eye movement sleep to wake by 12 ± 6.7% (P = 0.007). Our preliminary results suggest a sleep‐stabilizing role for the intervention, which may mimic the effect of sleep slow‐wave‐enhancing drugs.     

Changes in regional cerebral blood volume in frontal cortex during mental work with and without caffeine intake: functional monitoring using near-infrared spectroscopy

Near-infrared spectroscopy (NIRS) was used to measure frontal regional cerebral blood volume (rCBV) in a person whose brain was under the influence of pharmacological agents while the person was performing a complex task. Fourteen healthy participants were administered Uchida-Kraepelin psychodiagnostic (UKP) tests before and after caffeine intake, and the concentration of caffeine in the urine was measured. The average number of answers and the average number of correct answers given by the participants improved significantly following caffeine intake. During the UKP testing, changes in the rCBV in the inferior frontal cortex were continuously measured using NIRS. The volume during the rest periods decreased as a result of caffeine-induced constriction of the cerebral arteriola. The volume increased during the mental work, but the degree of the increase was the same before and after caffeine intake. Although the performance of the mental work improved following caffeine intake, the improvement was not reflected in the rCBV in the inferior frontal cerebral cortex. These results suggest that caffeine helps to protect the brain from excessive hyperemia in addition to activating the neurons in the prefrontal cortex.     

Laser speckle contrast imaging of cerebral blood flow in humans during neurosurgery: a pilot clinical study

Monitoring cerebral blood flow (CBF) during neurosurgery can provide important physiological information for a variety of surgical procedures. CBF measurements are important for assessing whether blood flow has returned to presurgical baseline levels and for assessing postsurgical tissue viability. Existing techniques for intraoperative monitoring of CBF based on magnetic resonance imaging are expensive and often impractical, while techniques such as indocyanine green angiography cannot produce quantitative measures of blood flow. Laser speckle contrast imaging (LSCI) is an optical technique that has been widely used to quantitatively image relative CBF in animal models in vivo. In a pilot clinical study, we adapted an existing neurosurgical operating microscope to obtain LSCI images in humans in real time during neurosurgery under baseline conditions and after bipolar cautery. Simultaneously recorded ECG waveforms from the patient were used to develop a filter that helped reduce measurement variabilities due to motion artifacts. Results from this study demonstrate the feasibility of using LSCI to obtain blood flow images during neurosurgeries and its capability to produce full field CBF image maps with excellent spatial resolution in real-time with minimal disruption to the surgical procedure.     

强迫症患者言语流畅性任务脑激活时间特征的近红外光谱成像研究

目的:探讨强迫症患者言语流畅性任务(VFT)下前额叶及颞叶激活的时间特征。方法:选取70例符合DSM-IV强迫症诊断标准的患者和70例正常对照,应用52通道的近红外光谱成像技术(NIRS)测评完成VFT时前额叶及颞叶血流的变化。比较两组完成任务时氧合血红蛋白(oxy-Hb)、脱氧血红蛋白(deoxy-Hb)及总血红蛋白(total-Hb)浓度达峰时间的差异。结果:与正常对照组相比,强迫症患者52个通道oxy-Hb、deoxy-Hb和total-Hb浓度的平均达峰时间明显延迟[(61±12)s vs.(52±11)s,(64±10)s vs.(58±10)s,(59±13)s vs.(51±13)s,均P<0.01]。强迫症组oxy-Hb和total-Hb在眶额叶、额极、前额下回、颞中回及颞上回等脑区达峰时间明显延迟(均P<0.05,FDR校正)。结论:强迫症患者执行言语流畅性任务时前额叶及颞叶皮质激活可能有延迟。     

GP referral of patients with osteoarthritis for consideration of total joint replacement: a longitudinal study

Background

Individuals with hip or knee osteoarthritis (OA) are referred to orthopaedic surgeons if considered by their GP as potential candidates for total joint replacement (TJR). It is not clear which patients end up having this surgery.

Aim

The aim of the study was to investigate symptom variation in individuals with OA newly referred by GPs to an orthopaedic surgeon for consideration for TJR, and to determine the predictors of having this procedure.

Design and setting

A longitudinal study of patients at a regional orthopaedic centre with follow-up at 3, 6, and 12 months by postal questionnaire.

Method

GP referrals of patients with OA to orthopaedic surgeons were consecutively sampled. Of the 431 eligible patients, 257 (59.6%) were recruited. Validated measurement tools were used to measure pain, physical functioning, severity of OA, and health-related quality of life.

Results

Over half the participants were in constant pain, taking pain medication more than once per day. Only 67 of 134 (50%) hip and 40 of 123 (33%) knee patients had a TJR within 12 months. Those who had a replacement had been diagnosed with OAfora shorter time, reported more frequent pain, were more likely to use a walking stick, and had worse pain, stiffness, and physical functioning.

Conclusion

Many individuals considered for TJR ultimately may not have surgery, and more effective strategies of management need to be developed between primary and secondary care to achieve better outcomes and to improve quality of care.     

Evaluation of continuous aspiration of subglottic secretions in prevention of microaspiration during general anesthesia: a randomized controlled pilot study

AimTo assess the difference between endotracheal tubes (ETT) with continuous suction of subglottic secretions (CASS) and standard ETT in preventing secretions movement from the pharynx into the trachea, past the inflated cuff during general anesthesia.MethodsThis randomized, controlled trial enrolled 50 patients who underwent general anesthesia for elective abdominal surgery lasting longer than two hours. They received either ETT with CASS: Teleflex ISIS HVT (GISIS, n = 17) or Mallinckrodt TaperGuard Evac (GEvac, n = 17), or ETT without suction: Mallinckrodt Intermediate Hi-Lo (GStand, n = 16). Methylene blue dye solution (10 mL) was delivered into the hypopharynx every 60 minutes. Subglottic secretions were continuously suctioned. Fiberoptic bronchoscopy was performed every 20 minutes and during tracheal extubation to evaluate the dye location.ResultsThe groups did not differ in age, sex, body mass index, race, American Society of Anesthesiologists status, and surgery type. Dye migrated past the inflated cuff into the distal trachea in no patient with ETT with CASS and in 13% of patients with standard ETT. On tracheal extubation, dye migrated into the distal trachea more often in the GStand group (56%), compared with the GEvac (13%) and GISIS group (29%) (P = 0.045). The GISIS group had 26 ± 19 mL of secretions suctioned from above the inflated cuff, while the GEvac group had 13 ± 10 mL (P = 0.05).ConclusionCompared with standard ETT, ETT with CASS efficiently removed secretions during general anesthesia, prevented secretions from migrating past the inflated cuff, and significantly reduced the amount of secretions that reached the distal airways on tracheal extubation.ClinicalTrial.gov identification number{"type":"clinical-trial","attrs":{"text":"NCT01386879","term_id":"NCT01386879"}}NCT01386879

Postoperative pulmonary complications (PPC) commonly lead to morbidity and mortality in patients managed with general anesthesia for major surgery. In a systematic review of PPC after non-cardiothoracic surgery, the average incidence was 3.4% with a range from 1% to over 40% (1). Elderly and diabetic patients had the highest incidence. The incidence in abdominal surgery was 14.2% (1). A prospective multicenter study with a heterogeneous surgical population of almost 2500 patients revealed a 5.0% incidence of PPC; with a high mortality in patients who developed PPC (2). Patients with evidence of microaspiration have about three times higher incidence of postoperative pneumonia compared with patients without microaspiration (40% vs 12%), with mortality rate of 19.2% if they develop pneumonia (3).Endotracheal tubes (ETT) with continuous aspiration of subglottic secretions (CASS) are recommended in intensive care unit (ICU) patients requiring prolonged mechanical ventilation to prevent ventilator-associated pneumonia (4). A meta-analysis showed almost a 50% reduction of ventilator-associated pneumonia in patients receiving ETT with CASS in the ICU compared with standard ETT (5). It is unknown if using an ETT with CASS intraoperatively reduces the incidence of PPC in patients undergoing prolonged general anesthesia, and are extubated at the end of surgery.We hypothesized that a subglottic suction ETT with CASS would effectively remove secretions that accumulate above the inflated cuff and decrease the volume of secretions aspirated into the distal trachea during general anesthesia with mechanical ventilation and during tracheal extubation. The primary aim of the study was to evaluate whether there is a difference between three types of ETT in preventing the movement of methylene blue dye from the pharynx into the trachea, past the inflated cuff. The secondary objectives were to evaluate whether there is a difference in the volume, pH, and bacterial load of the secretions aspirated from above the subglottic suction ETT cuff.     

Accuracy of a real-time continuous glucose monitoring system in children with septic shock: A pilot study

Aims:

The aim of this prospective, observational study was to determine the accuracy of a real-time continuous glucose monitoring system (CGMS) in children with septic shock.

Subjects and Methods:

Children aged 30 days to 18 years admitted to the Pediatric Intensive Care Unit with septic shock were included. A real-time CGMS sensor was used to obtain interstitial glucose readings. CGMS readings were compared statistically with simultaneous laboratory blood glucose (BG).

Results:

Nineteen children were included, and 235 pairs of BG-CGMS readings were obtained. BG and CGMS had a correlation coefficient of 0.61 (P < 0.001) and a median relative absolute difference of 17.29%. On Clarke''s error grid analysis, 222 (94.5%) readings were in the clinically acceptable zones (A and B). When BG was < 70, 70–180, and > 180 mg/dL, 44%, 100%, and 76.9% readings were in zones A and B, respectively (P < 0.001). The accuracy of CGMS was not affected by the presence of edema, acidosis, vasopressors, steroids, or renal replacement therapy. On receiver operating characteristics curve analysis, a CGMS reading <97 mg/dL predicted hypoglycemia (sensitivity 85.2%, specificity 75%, area under the curve [AUC] =0.85). A reading > 141 mg/dL predicted hyperglycemia (sensitivity 84.6%, specificity 89.6%, AUC = 0.87).

Conclusion:

CGMS provides a fairly, accurate estimate of BG in children with septic shock. It is unaffected by a variety of clinical variables. The accuracy over extremes of blood sugar may be a concern. We recommend larger studies to evaluate its use for the early detection of hypoglycemia and hyperglycemia.