Liver abscess due to <Emphasis Type="Italic">Fusobacterium</Emphasis> species detected on ultrasonography: a case report

An oral infection harboring Fusobacterium species can gain entrance to the liver via hematogenous spread in the form of septic embolus, and can thereby cause abscesses. Such spread, described as Lemierre syndrome, is life threatening. We present such a case history of a man in his mid-40s, who presented with infection and Fusobacterium liver abscess with an acute fulminant disease course. The initial diagnosis was arrived at by ultrasound imaging and blood investigations. He was treated with antibiotics, ultrasound-guided liver abscess drainage, and extraction of the infected molar tooth. He was discharged 6 weeks after admission. To date, there have been no reports describing the ultrasound images of a Fusobacterium liver abscess in detail. Hence, we herein present the ultrasound images of a Fusobacterium liver abscess.     

Velocity–pressure loops for continuous assessment of ventricular afterload: influence of pressure measurement site

VPloop, the graphical representation of pressure versus velocity, and its characteristic angles, GALA and β, can be used to monitor cardiac afterload during anesthesia. Ideally VPloop should be measured from pressure and velocity obtained at the same arterial location but standard of care usually provide either radial or femoral pressure waveforms. The purpose of this study was to look at the influence of arterial sites and the use of a transfer function (TF) on VPloop and its related angles. Invasive pressure signals were recorded in 25 patients undergoing neuroradiology intervention under general anesthesia with transesophageal flow velocity monitoring. Pressures were recorded in the descending thoracic aorta, abdominal aorta, femoral and radial arteries. We compared GALA and β from VPloops generated from each location and in high and low risk patients. GALA was similar in the central locations (55°[49–63], 52°[47–61] and 54°[45–62] from descending thoracic to femoral artery, median[interquartile], p?=?0.10), while there was a difference in β angle (16°[4–27] to 8°[3–15], p?<?0.0001). GALA and β obtained from radial waveforms were different (39°[31–47] compared to 46°[36–54] and 6°[2–14] compared to 16°[4–27] for GALA and β angles respectively, p?<?0.001) which was corrected by the use of a TF (45°[32–55] and 17°[5–28], p?=?ns). GALA and β are underestimated when measured with a radial catheter. Using pressure waveforms from femoral locations alters VPloops, GALA and β in a smaller extend. The use of a TF on radial pressure allows to correctly plot VPloops and their characteristic angles for routine clinical use.     

ADARRI: a novel method to detect spurious R-peaks in the electrocardiogram for heart rate variability analysis in the intensive care unit

We developed a simple and fully automated method for detecting artifacts in the R-R interval (RRI) time series of the ECG that is tailored to the intensive care unit (ICU) setting. From ECG recordings of 50 adult ICU-subjects we selected 60 epochs with valid R-peak detections and 60 epochs containing artifacts leading to missed or false positive R-peak detections. Next, we calculated the absolute value of the difference between two adjacent RRIs (adRRI), and obtained the empirical probability distributions of adRRI values for valid R-peaks and artifacts. From these, we calculated an optimal threshold for separating adRRI values arising from artifact versus non-artefactual data. We compared the performance of our method with the methods of Berntson and Clifford on the same data. We identified 257,458 R-peak detections, of which 235,644 (91.5%) were true detections and 21,814 (8.5%) arose from artifacts. Our method showed superior performance for detecting artifacts with sensitivity 100%, specificity 99%, precision 99%, positive likelihood ratio of 100 and negative likelihood ratio <0.001 compared to Berntson’s and Clifford’s method with a sensitivity, specificity, precision and positive and negative likelihood ratio of 99%, 78%, 82%, 4.5, 0.013 for Berntson’s method and 55%, 98%, 96%, 27.5, 0.460 for Clifford’s method, respectively. A novel algorithm using a patient-independent threshold derived from the distribution of adRRI values in ICU ECG data identifies artifacts accurately, and outperforms two other methods in common use. Furthermore, the threshold was calculated based on real data from critically ill patients and the algorithm is easy to implement.     

Performance of a second generation pulmonary capnotracking system for continuous monitoring of cardiac output

Technologies for minimally-invasive cardiac output measurement in patients during surgery remain little used in routine practice. We tested a redeveloped system based on CO₂ elimination (VCO₂) by the lungs for use in ventilated patients, which can be seamlessly integrated into a modern anesthesia/monitoring platform, and provides automated, continuous breath-by-breath cardiac output monitoring. A prototype measurement system was constructed to measure VCO₂ and end-tidal CO₂ concentration with each breath. A baseline measurement of non-shunt cardiac output was made during a brief oscillating change in ventilator rate, according to the differential CO₂ Fick approach and repeated at 5–10 min intervals. Continuous breath-by-breath monitoring of cardiac output was performed between these intervals from measurement of VCO₂, using a derivation of the Fick equation applied to pulmonary CO₂ elimination and cardiac output displayed in real time. Measurements were compared with simultaneous measurements by thermodilution in 50 patients undergoing cardiac surgery or liver transplantation. Overall mean bias [sd] for agreement in cardiac output measurement was ??0.3 [1.1] L/min, percentage error?±?38.7%, intraclass correlation coefficient?=?0.91. Concordance in measurement of changes of at least 15% in cardiac output was 81.4%, with a mean angular bias of ??1.7°, and radial limits of agreement of ±?76.2° on polar plot analysis. The accuracy and precision compared favourably to other clinical techniques. The method is relatively seamless and automated and has potential for continuous, cardiac output monitoring in ventilated patients during anesthesia and critical care.     

Variation in intraocular pressure caused by repetitive positional changes during laparoscopic colorectal surgery: a prospective,randomized, controlled study comparing propofol and desflurane anesthesia

Laparoscopic surgery is often prolonged and requires positional changes to facilitate surgical access. Previous studies reported intraocular pressure (IOP) changes in one fixed position. This study investigated the effect of desflurane and propofol anesthesia on IOP during repeated positional changes. A total of 46 patients undergoing laparoscopic colorectal surgery were randomized into desflurane or propofol groups. IOP was measured using a handheld tonometer at seven time points: before induction (baseline), after endotracheal intubation, after pneumoperitoneum, after the first Trendelenburg and right tilt position, after reverse Trendelenburg and right tilt position, after the second Trendelenburg and right tilt position and before endotracheal extubation. Trendelenburg positioning raised IOP in both groups. In the desflurane group, IOP at the first Trendelenburg position was 6.27 and 8.48 mmHg higher than baseline IOP in left and right eye, respectively; IOP at the second Trendelenburg position was 7 and 9.44 mmHg higher than baseline in left and right eye, respectively. In the propofol group, IOP at the first Trendelenburg position was 2.04 and 4.04 mmHg higher than baseline in left and right eyes, respectively. It was 3.04 and 4.87 mmHg higher than baseline in left and right eye, respectively, at the second Trendelenburg position. In the desflurane group, 56.52% patients exhibited high IOP (≥?25 mmHg) compared with 13.04% in the propofol group at the second Trendelenburg position in the right eyes (P?=?0.005). There was a positive correlation between IOP and peak inspiratory pressure (P?<?0.001). Propofol anesthesia mitigated wide variations in IOP caused by repetitive positional changes during laparoscopic colorectal surgery.     

Low minute ventilation episodes during anesthesia recovery following intraperitoneal surgery as detected by a non-invasive respiratory volume monitor

An electrical impedance-based noninvasive respiratory volume monitor (RVM) accurately reports minute volume, tidal volume and respiratory rate. Here we used the RVM to quantify the occurrence of and evaluate the ability of clinical factors to predict respiratory depression in the post-anesthesia care unit (PACU). RVM generated respiratory data were collected from spontaneously breathing patients following intraperitoneal surgeries under general anesthesia admitted to the PACU. Respiratory depression was defined as low minute ventilation episode (LMVe, <?40% predicted minute ventilation for at least 2 min). We evaluated for associations between clinical variables including minute ventilation prior to opioid administration and LMVe following the first PACU administration of opioid. Also assessed was a low respiratory rate (<?8 breaths per minute) as a proxy for LMVe. Of 107 patients, 38 (36%) had LMVe. Affected patients had greater intraoperative opioid dose, P?=?0.05. PACU opioids were administered to 45 (42.1%) subjects, of which 27 (25.2%) had LMVe (P?=?0.42) within 30 min following opioid. Pre-opioid minute ventilation <?70% of predicted normal value was associated with LMVe, P?<?0.01, (sensitivity?=?100%, specificity?=?81%).Low respiratory rate was a poor predictor of LMVe (sensitivity?=?11.8%). Other clinical variables (e.g., obstructive sleep apnea) were not found to be predictors of LMVe. Using RVM we identified that mild, clinically nondetectable, respiratory depression prior to opioid administration in the PACU was associated with the development of substantial subsequent respiratory depression during the PACU stay.     

In vivo investigation of ear canal pulse oximetry during hypothermia

Pulse oximeters rely on the technique of photoplethysmography (PPG) to estimate arterial oxygen saturation (SpO\(_2\)). In conditions of poor peripheral perfusion such as hypotension, hypothermia, and vasoconstriction, the PPG signals detected are often weak and noisy, or in some cases unobtainable. Hence, pulse oximeters produce erroneous SpO\(_2\) readings in these circumstances. The problem arises as most commercial pulse oximeter probes are designed to be attached to peripheral sites such as the finger or toe, which are easily affected by vasoconstriction. In order to overcome this problem, the ear canal was investigated as an alternative site for measuring reliable SpO\(_2\) on the hypothesis that blood flow to this central site is preferentially preserved. A novel miniature ear canal PPG sensor was developed along with a state of the art PPG processing unit to investigate PPG measurements from the bottom surface of the ear canal. An in vivo study was carried out in 15 healthy volunteers to validate the developed technology. In this comparative study, red and infrared PPGs were acquired from the ear canal and the finger of the volunteers, whilst they were undergoing artificially induced hypothermia by means of cold exposure (10 \(^\circ\)C). Normalised Pulse Amplitude (NPA) and SpO\(_2\) was calculated from the PPG signals acquired from the ear canal and the finger. Good quality baseline PPG signals with high signal-to-noise ratio were obtained from both the PPG sensors. During cold exposure, significant differences were observed in the NPA of the finger PPGs. The mean NPA of the red and infrared PPGs from the finger have dropped by >80%. Contrary to the finger, the mean NPA of red and infrared ear canal PPGs had dropped only by 0.2 and 13% respectively. The SpO\(_2\)s estimated from the finger sensor have dropped below 90% in five volunteers (failure) by the end of the cold exposure. The ear canal sensor, on the other hand, had only failed in one volunteer. These results strongly suggest that the ear canal may be used as a suitable alternative site for monitoring PPGs and arterial blood oxygen saturation at times were peripheral perfusion is compromised.