Clinical Monitoring and Computing

Additional concerns for the scavenging of anesthetic agents used for ICU sedation

Intravenous administration of medications during an anesthetic: a deceptively simple process

Expanding the usefulness of hemodynamic waveform analysis in the critically Ill

Limitations of near infrared spectroscopy (NIRS) in neurosurgical setting: our case experience Abstract One of the primary goals of anaesthesia in neurosurgical procedures is prevention of cerebral hypoxia leading to secondary neurological injury. Cerebral oximetry detects periods of cerebral hypoxemia and allows intervention for prevention of secondary brain injury and its sequelae. This can be achieved by the use of Near Infrared Spectroscopy (NIRS). In this regard, we present two cases where erroneous values of NIRS were shown which hindered monitoring of cerebral oxygenation in the intraoperative setting. In a neurosurgical setting, the erroneous values on the operative side could be attributed to altered tissue boundary conditions resulting in a changed optical path, which is normally held as a constant in NIRS measurements. The altered tissue boundary conditions could be due to the presence of air or blood between the myocutaneous flapskull, skull-dura, dura-brain interphases. It could also be that the sensors' penetrating depth was inadequate to compensate for the increased distance between sensor and brain tissue, thereby resulting in inaccurately higher values (> 80%).

Post-extrasystolic characteristics in the arterial blood pressure waveform are associated with right ventricular dysfunction in intensive care patients Abstract Right ventricular dysfunction (RVD) is associated with end-organ dysfunction and mortality, but has been an overlooked condition in the ICU. We hypothesized that analysis of the arterial waveform in the presence of ventricular extrasystoles could differentiate patients with RVD from patients with a normally functioning right ventricle, because the 2nd and 3rd post-ectopic beat could reflect right ventricular state (pulmonary transit time) during the preceding ectopy. We retrospectively identified patients with echocardiographic evidence of moderate-to-severe RVD and patients with a normal functioning right ventricle (control) from the MIMIC database. We identified waveform records where ECG and arterial pressure were available in combination, simultaneously with echocardiographic evaluation. Ventricular extrasystoles were visually confirmed and the median systolic blood pressure (SBP) of the 2nd and 3rd post-ectopic beats compared with the median SBP of the ten sinus beats preceding the extrasystole. We identified 34 patients in the control group and 24 patients in the RVD group with ventricular extrasystoles. The mean SBP reduction at the 2nd and 3rd beat was lower in the RVD group compared with the control group [− 1.7 (SD: 1.9) % vs. − 3.6 (SD: 1.9) %, p < 0.001], and this characteristic differentiated RVD subjects from control subjects with an AUC of 0.76 (CI [0.64; 0.89]), with a specificity of 91% and sensitivity of 50%. In this proof-of-concept study, we found that post-extrasystolic ABP characteristics were associated with RVD.

Cerebrovascular assessment of patients undergoing shoulder surgery in beach chair position using a multiparameter transcranial Doppler approach Abstract Although the beach-chair position (BCP) is widely used during shoulder surgery, it has been reported to associate with a reduction in cerebral blood flow, oxygenation, and risk of brain ischaemia. We assessed cerebral haemodynamics using a multiparameter transcranial Doppler-derived approach in patients undergoing shoulder surgery. 23 anaesthetised patients (propofol (2 mg/kg)) without history of neurologic pathology undergoing elective shoulder surgery were included. Arterial blood pressure (ABP, monitored with a finger-cuff plethysmograph calibrated at the auditory meatus level) and cerebral blood flow velocity (FV, monitored in the middle cerebral artery) were recorded in supine and in BCP. All subjects underwent interscalene block ipsilateral to the side of FV measurement. We evaluated non-invasive intracranial pressure (nICP) and cerebral perfusion pressure (nCPP) calculated with a black-box mathematical model; critical closing pressure (CrCP); diastolic closing margin (DCM—pressure reserve available to avoid diastolic flow cessation); cerebral autoregulation index (Mxa); pulsatility index (PI). Significant changes occured for DCM [mean decrease of 6.43 mm Hg (p = 0.01)] and PI [mean increase of 0.11 (p = 0.05)]. ABP, FV, nICP, nCPP and CrCP showed a decreasing trend. Cerebral autoregulation was dysfunctional (Mxa > 0.3) and PI deviated from normal ranges (PI > 0.8) in both phases. ABP and nCPP values were low (< 60 mm Hg) in both phases. Changes between phases did not result in CrCP reaching diastolic ABP, therefore DCM did not reach critical values (≤ 0 mm Hg). BCP resulted in significant cerebral haemodynamic changes. If left untreated, reduction in cerebral blood flow may result in brain ischaemia and post-operative neurologic deficit.

Cerebral arterial time constant calculated from the middle and posterior cerebral arteries in healthy subjects Abstract The cerebral arterial blood volume changes (∆CaBV) during a single cardiac cycle can be estimated using transcranial Doppler ultrasonography (TCD) by assuming pulsatile blood inflow, constant, and pulsatile flow forward from large cerebral arteries to resistive arterioles [continuous flow forward (CFF) and pulsatile flow forward (PFF)]. In this way, two alternative methods of cerebral arterial compliance (Ca) estimation are possible. Recently, we proposed a TCD-derived index, named the time constant of the cerebral arterial bed (τ), which is a product of Ca and cerebrovascular resistance and is independent of the diameter of the insonated vessel. In this study, we aim to examine whether the τ estimated by either the CFF or the PFF model differs when calculated from the middle cerebral artery (MCA) and the posterior cerebral artery (PCA). The arterial blood pressure and TCD cerebral blood flow velocity (CBFVa) in the MCA and in the PCA were non-invasively measured in 32 young, healthy volunteers (median age: 24, minimum age: 18, maximum age: 31). The τ was calculated using both the PFF and CFF models from the MCA and the PCA and compared using a non-parametric Wilcoxon signed-rank test. Results are presented as medians (25th–75th percentiles). The cerebrovascular time constant estimated in both arteries using the PFF model was shorter than when using the CFF model (ms): [64.83 (41.22–104.93) vs. 178.60 (160.40–216.70), p < 0.001 in the MCA, and 44.04 (17.15–81.17) vs. 183.50 (153.65–204.10), p < 0.001 in the PCA, respectively]. The τ obtained using the PFF model was significantly longer from the MCA than from the PCA, p = 0.004. No difference was found in the τ when calculated using the CFF model. Longer τ from the MCA might be related to the higher Ca of the MCA than that of the PCA. Our results demonstrate MCA-PCA differences in the τ, but only when the PFF model was applied.

Impact of predictive analytics based on continuous cardiorespiratory monitoring in a surgical and trauma intensive care unit Abstract Predictive analytics monitoring, the use of patient data to provide continuous risk estimation of deterioration, is a promising new application of big data analytical techniques to the care of individual patients. We tested the hypothesis that continuous display of novel electronic risk visualization of respiratory and cardiovascular events would impact intensive care unit (ICU) patient outcomes. In an adult tertiary care surgical trauma ICU, we displayed risk estimation visualizations on a large monitor, but in the medical ICU in the same institution we did not. The risk estimates were based solely on analysis of continuous cardiorespiratory monitoring. We examined 4275 individual patient records within a 7 month time period preceding and following data display. We determined cases of septic shock, emergency intubation, hemorrhage, and death to compare rates per patient care pre-and post-implementation. Following implementation, the incidence of septic shock fell by half (p < 0.01 in a multivariate model that included age and APACHE) in the surgical trauma ICU, where the data were continuously on display, but by only 10% (p = NS) in the control Medical ICU. There were no significant changes in the other outcomes. Display of a predictive analytics monitor based on continuous cardiorespiratory monitoring was followed by a reduction in the rate of septic shock, even when controlling for age and APACHE score.

Respiratory measurement using infrared thermography and respiratory volume monitor during sedation in patients undergoing endoscopic urologic procedures under spinal anesthesia Abstract We aimed to evaluate changes in respiratory pattern after sedation by simultaneously applying a respiratory volume monitor (ExSpiron1Xi, RVM) and infrared thermography (IRT) to patients undergoing spinal anesthesia during endoscopic urologic surgeries. After spinal anesthesia was performed, the patient was placed in a lithotomy position for surgery. Then, we established the baseline of the RVM, and started monitoring the mouth and nose with the infrared camera. SpO2 was continuously measured throughout these processes. Once the baseline was set, 0.05 mg/kg midazolam was administered for sedation. Apnea was defined as cessation of airflow for ≥ 10 s with respiratory rate of < 6 breaths/min; hypopnea was defined as a decrease in oxygen hemoglobin of > 4%, compared to baseline. We measured the time at which apnea was detected by IRT, the time at which hypopnea was detected by RVM, and the time at which hypoxia was detected by SpO2. Twenty patients (age: 68.9 ± 11.2 years, body mass index: 24.2 ± 2.6 kg/min2) completed the study. Before sedation, the baseline correlation coefficient of respiratory rate detection between RVM and IRT was 0.866. After midazolam administration, apnea was detected in all subjects within the first 5 min by IRT; the median time required to detect apnea was 102.5 [interquartile range (IQR) 25–75%: 80–155] s. Hypopnea was detected in all subjects within the first 5 min by RVM: the median time required to detect hypopnea was 142.5 (IQR 115–185.2) s. The median time required for SpO2 to decrease > 4% from baseline was 160 (IQR 125–205) s. Our results suggest that IRT can be useful for rapid detection of respiratory changes in patients undergoing sedation following spinal anesthesia for endoscopic urologic procedures.

Pediatric blood pressures during anesthesia assessed using normalization and principal component analysis techniques Abstract Expected values for blood pressure are known for both unanesthetized and anesthetized children. The statistics of changes in blood pressure during anesthesia, which may have important diagnostic significance, have not been reported. The purpose of this study was to report the variation in changes in blood pressure in four pediatric age groups, undergoing both cardiac and non-cardiac surgery. An analysis of the changes in blood pressure using normalization and principal component analysis techniques was performed using an existing electronic dataset of intra-arterial pediatric blood pressure values during anesthesia. Cardiac and noncardiac cases were analyzed separately. For 1361 non-cardiac cases, the average systolic blood pressure increased from 55.2 (17.6) mmHg in the first month of life to 85.4 (17.7) mmHg at 5–6 years. For 912 cardiac cases, the average systolic blood pressure increased from 55.7 (16.7) to 71.8 (24.8) mmHg in these cohorts. For non-cardiac cases in the first month, the mean (SD) for change in blood pressure over a 30 s period was 0.00 (8.8), for 5–6 year olds 0.0 (7.4); for cardiac cases, 0.1 (9.2) to − 0.1 (9.2). Variations in systolic blood pressure over a 5-min period were wider: in non-cardiac from 0.1 (12.2) mmHg (first month) to 0.4 (11.5) mmHg (5–6 year old) and from 0.2 (12.5) to 0.4 (14.2) mmHg in cardiac cases. Absolute blood pressures and changes in blood pressure during anesthesia in pediatric cardiac and non-cardiac surgical cases have been analyzed from a population database. Using these values, the quantitative methods of normalization and principal component analysis allow the identification of statistically significant changes.

Alexandros Sfakianakis
Anapafseos 5 . Agios Nikolaos
Crete.Greece.72100
2841026182

6948891480

alsfakia@gmail.com