The association of hemodynamic parameters and clinical demographic variables with acute postoperative pain in female oncological breast surgery patients: A retrospective cohort study.

OBJECTIVES: Appropriate administration of intraoperative analgesia is an essential factor in care and reasonable recovery times. Inappropriate intraoperative analgesia puts the patient at risk of acute postoperative pain (APOP). The absence of an objective standard for intraoperative nociceptive monitoring complicates pain care. Heart rate (HR) and mean arterial blood pressure (MABP) have been suggested as useful parameters during general anesthesia for nociceptive monitoring. However, studies focusing on whether intraoperative heart rate variability (HRv) and mean arterial blood pressure variability (MABPv) during general anesthesia can accurately monitor nociception in patients have remained inconclusive. The current study aimed to (1) identify the association of intraoperative heart rate and blood pressure variability in patients undergoing low-risk surgery with the incidence of APOP in the immediate postoperative setting and (2) evaluate the associations of clinical demographic factors with the incidence of APOP. METHODS: A retrospective observational cohort study was conducted. The outcome was moderate-to-severe APOP, defined as a numeric rating scale score of ≥ 4. HRv, MABPv, and potential confounders, such as age, body mass index, duration of surgery, smoking, depression, preoperative use of analgesics, and type of surgery, were used as independent variables. RESULTS: Data from 764 female oncological breast surgery patients were analyzed. No statistically significant association of HRv and MABPv with APOP was found. Lower age was associated with higher odds of APOP (odds ratio [OR] 0.978, p = 0.001). Increased length of surgery (OR 1.013, p = 0.022) and a history of depression were associated with increased odds of APOP (OR 2.327, p = 0.010). The subtype of surgery was statistically significantly associated with APOP (p = 0.006). CONCLUSIONS: Our results suggest that heart rate and blood pressure variability intraoperatively, in female patients undergoing low-risk surgery, are not associated with, and thus not predictive of, APOP in the immediate postoperative setting.

Towards continuous non-invasive blood pressure measurements-interpretation of the vasculature response to cuff inflation.

Blood pressure (BP) surrogates, such as pulse transit time (PTT) or pulse arrival time (PAT), have been intensively explored with the goal of achieving cuffless, continuous, and accurate BP inference. In order to estimate BP, a one-point calibration strategy between PAT and BP is typically used. Recent research focuses on advanced calibration procedures exploiting the cuff inflation process to improve calibration robustness by active and controlled modulation of peripheral PAT, as measured via plethysmograph (PPG) and electrocardiogram (ECG) combination. Such methods require a detailed understanding of the mechanisms behind the vasculature's response to cuff inflation; for this, a model has recently been developed to infer the PAT-BP calibration from measured cuff-induced vasculature changes. The model, while promising, is still preliminary and only partially validated; in-depth analysis and further developments are still needed. Therefore, this work aims to improve our understanding of the cuff-vasculature interaction in this model; we seek to define potential opportunities and to highlight which aspects may require further study. We compare model behaviors with clinical data samples based on a set of observable characteristics relevant for BP inference and calibration. It is found that the observed behaviors are qualitatively well represented with the current simulation model and complexity, with limitations regarding the prediction of the onset of the distal arm dynamics and behavior changes at high cuff pressures. Additionally, a sensitivity analysis of the model's parameter space is conducted to show the factors that influence the characteristics of its observable outputs. It was revealed that easily controllable experimental variables, such as lateral cuff length and inflation rate, have a significant impact on cuff-induced vasculature changes. An interesting dependency between systemic BP and cuff-induced distal PTT change is also found, revealing opportunities for improved methods for BP surrogate calibration. However, validation via patient data shows that this relation does not hold for all patients, indicating required model improvements to be validated in follow up studies. These results provide promising directions to improve the calibration process featuring cuff inflation towards accurate and robust non-invasive blood pressure estimation.

Modulation of pulse travel and blood flow during cuff inflation- An experimental case study.

The blood pressure (BP) cuff can be used to modulate blood flow and propagation of pressure pulse along the artery. In our previous work, we researched methods to adapt cuff modulation techniques for pulse transit time vs. BP calibration and for measurement of other hemodynamic indices of potential interest to critical care, such as arterial compliance. A model characterized the response of the vasculature located directly under the cuff, but assumed that no significant changes occur in the distal vasculature.This study has been tailored to gain insights into the response of distal BP and pulse transit time to cuff inflation. Invasive BP data collected downstream from the cuff demonstrates that highly dynamic processes occur in the distal arm during cuff inflation. Mean arterial pressure increases in the distal artery by up to 20 mmHg, leading to a decrease in pulse transit time of up to 20 ms. Clinical Relevance: Such significant changes need to be taken into account in order to improve non-invasive BP estimations and to enable inference of other hemodynamic parameters from vasculature response to cuff inflation. A simple model is developed in order to reproduce the observed behaviors. The lumped-parameter model demonstrates opportunities for cuff modulation measurements which can reveal information on parameters such as systemic resistance, distal arterial, venous compliances and artery-vein interaction.

Modulation of Pulse Propagation and Blood Flow via Cuff Inflation-New Distal Insights.

In standard critical care practice, cuff sphygmomanometry is widely used for intermittent blood pressure (BP) measurements. However, cuff devices offer ample possibility of modulating blood flow and pulse propagation along the artery. We explore underutilized arrangements of sensors involving cuff devices which could be of use in critical care to reveal additional information on compensatory mechanisms. In our previous work, we analyzed the response of the vasculature to occlusion perturbations by means of observations obtained non-invasively. In this study, our aim is to (1) acquire additional insights by means of invasive measurements and (2) based on these insights, further develop cuff-based measurement strategies. Invasive BP experimental data is collected downstream from the cuff in two patients monitored in the OR. It is found that highly dynamic processes occur in the distal arm during cuff inflation. Mean arterial pressure increases in the distal artery by 20 mmHg, leading to a decrease in pulse transit time by 20 ms. Previous characterizations neglected such distal vasculature effects. A model is developed to reproduce the observed behaviors and to provide a possible explanation of the factors that influence the distal arm mechanisms. We apply the new findings to further develop measurement strategies aimed at acquiring information on pulse arrival time vs. BP calibration, artery compliance, peripheral resistance, artery-vein interaction.

Trauma care before and after optimisation in a level I trauma Centre: Life-saving changes.

BACKGROUND: The implementation of trauma systems has led to a significant reduction in mortality and length of hospital stay. In our level I trauma centre, 24/7 in-hospital coverage was implemented, and a renovation of the trauma room took place to improve the trauma care. The aim of the present study was to examine the effect of the optimised in-hospital infrastructure in terms of mortality, processes and clinical outcomes. METHODS: We performed a retrospective cohort study of prospectively collected data. All adult trauma patients admitted to our trauma centre directly during two time periods (2010-2012 and 2014-2016) were included. Any patients below the age of 18 years and patients who underwent primary trauma screening in another hospital were excluded. Logistic and linear regression were used and adjusted for demographics and characteristics of trauma. The primary endpoint was mortality. The secondary endpoints were subgroups of earlier mortality rates and severely injured patients, processes and clinical outcomes. RESULTS: In period I, 1290 patients were included, and in period II, 2421. The adjusted mortality in the trauma room (odds ratio (OR): 0.18; CI: 0.05-0.63) and the total in-hospital mortality (OR: 0.63 CI: 0.42-0.95) showed a significant reduction in period II. The trauma room (TR) time decreased by 30 min (p < 0.001), and the time until CT decreased by 22 min (p < 0.001). The number of delayed diagnoses and complications were significantly lower in the second period, with an OR of 0.2 (CI: 0.1-0.2) and 0.4 (CI: 0.3-0.6), respectively. The hospital length of stay and ICU length of stay decreased significantly, -1.5 day (p = 0.010) and -1.8 days (p = 0.022) respectively. CONCLUSIONS: Optimisation of the in-hospital infrastructure related to trauma care resulted in improved survival rates in both severely injured patients as well as in the whole trauma population. Moreover, the processes and clinical outcomes improved, showing a shorter hospital length of stay, shorter TR time, fewer complications and fewer delayed diagnoses.

Finger and forehead photoplethysmography-derived pulse-pressure variation and the benefits of baseline correction.

To non-invasively predict fluid responsiveness, respiration-induced pulse amplitude variation (PAV) in the photoplethysmographic (PPG) signal has been proposed as an alternative to pulse pressure variation (PPV) in the arterial blood pressure (ABP) signal. However, it is still unclear how the performance of the PPG-derived PAV is site-dependent during surgery. The aim of this study is to compare finger- and forehead-PPG derived PAV in their ability to approach the value and trend of ABP-derived PPV. Furthermore, this study investigates four potential confounding factors, (1) baseline variation, (2) PPV, (3) ratio of respiration and heart rate, and (4) perfusion index, which might affect the agreement between PPV and PAV. In this work, ABP, finger PPG, and forehead PPG were continuously recorded in 29 patients undergoing major surgery in the operating room. A total of 91.2 h data were used for analysis, from which PAV and PPV were calculated and compared. We analyzed the impact of the four factors using a multiple linear regression (MLR) analysis. The results show that compared with the ABP-derived PPV, finger-derived PAV had an agreement of 3.2 ± 5.1%, whereas forehead-PAV had an agreement of 12.0 ± 9.1%. From the MLR analysis, we found that baseline variation was a factor significantly affecting the agreement between PPV and PAV. After correcting for respiration-induced baseline variation, the agreements for finger- and forehead-derived PAV were improved to reach an agreement of - 1.2 ± 3.8% and 3.3 ± 4.8%, respectively. To conclude, finger-derived PAV showed better agreement with ABP-derived PPV compared to forehead-derived PAV. Baseline variation was a factor that significantly affected the agreement between PPV and PAV. By correcting for the baseline variation, improved agreements were obtained for both the finger and forehead, and the difference between these two agreements was diminished. The tracking abilities for both finger- and forehead-derived PAV still warrant improvement for wide use in clinical practice. Overall, our results show that baseline-corrected finger- and forehead-derived PAV may provide a non-invasive alternative for PPV.

On algorithms for calculating arterial pulse pressure variation during major surgery.

OBJECTIVE: Arterial pulse pressure variation (PPV) is widely used for predicting fluid responsiveness and supporting fluid management in the operating room and intensive care unit. Available PPV algorithms have been typically validated for fluid responsiveness during episodes of hemodynamic stability. Yet, little is known about the performance of PPV algorithms during surgery, where fast changes of the blood pressure may affect the robustness of the presented PPV value. This work provides a comprehensive understanding of how various existing algorithmic designs affect the robustness of the presented PPV value during surgery, and proposes additional processing for the pulse pressure signal before calculating PPV. APPROACH: We recorded arterial blood pressure waveforms from 23 patients undergoing major abdominal surgery. To evaluate the performance, we designed three clinically relevant metrics. Main results and Significance: The results show that all algorithms performed well during episodes of hemodynamic stability. Moreover, it is demonstrated that the proposed processing helps improve the robustness of PPV during the entire course of surgery.

A ventilation technique for oxygenation and carbon dioxide elimination in CPR: Continuous insufflation of oxygen at three levels of pressure in a pig model.

AIM: Pulmonary ventilation remains an important part of cardiopulmonary resuscitation, affecting gas exchange and haemodynamics. We designed and studied an improved method of ventilation for CPR, constructed specifically to support both gas exchange and haemodynamics. This method uses continuous insufflation of oxygen at three levels of pressure, resulting in tri-level pressure ventilation (TLPV). We hypothesized that TLPV improves gas exchange and haemodynamics compared to manual gold standard ventilation (GSV). METHODS: In 14 pigs, ventricular fibrillation was induced and automated CPR performed for 10 min with either TLPV or GSV. After defibrillation, CPR was repeated with the other ventilation method. Gas exchange and haemodynamics were monitored. Data are presented as mean±standard error of the mean. RESULTS: TLPV was superior to GSV for PaO2 (163±36 mmHg difference; P=0.001), and peak AWP (-20±2 cmH2O difference; P=0.000) and higher for mean AWP (8±0.2 cmH2O difference; P=0.000). TLPV was comparable to GSV for CPP (5±3 mmHg difference; P=0.012), VCO2 (0.07±0.3 mL/min/kg difference; P=0.001), SvO2 (4±3%-point; P=0.001), mean carotid flow (-0.5±4 mL/min difference; P=0.016), and pHa (0.00±0.03 difference; P=0.002). The PaCO2 data do not provide a conclusive result (4±4 mmHg difference). CONCLUSION: We conclude that the ventilation strategy with a tri-level pressure cycle performs comparable to an expert, manual ventilator in an automated-CPR swine model.

Outpatient cataract surgery: incident and procedural risk analysis do not support current clinical ophthalmology guidelines.

OBJECTIVE: To evaluate whether an ophthalmologist-led, non-anesthesia-supported, limited monitoring pathway for phacoemulsification/intraocular lens cataract surgery, can be performed safely with only a medical emergency team providing support. DESIGN: Retrospective, observational, cohort study. PARTICIPANTS: All patients who underwent elective phacoemulsification/intraocular lens surgery under topical anesthesia in the ophthalmology outpatient unit between January 1, 2011, and December 31, 2012. METHODS: Cataract surgery was performed by phacoemulsification under topical anesthesia. The intake process mainly embraced ophthalmic evaluation, obtaining a medical history, and proposing the procedure. A staff ophthalmologist performed the procedure assisted by 2 registered nurses in an independent outpatient clinic operating room within the hospital. The clinical pathway was without dedicated presence of or access to anesthesia service. Perioperative monitoring was limited to blood pressure and plethysmography preoperatively and intraoperatively. Patients were offered supportive care and instructed to avoid fasting and continue all their chronic medication. MAIN OUTCOME MEASURES: The primary outcome measure was the incidence of adverse events requiring medical emergency team (MET) interventions throughout the pathway. Secondary outcome measures were surgical ocular complication rates, use of oral sedatives, and reported reasons to perform the surgery in the classical operation room complex. RESULTS: Within the cataract pathway, 6961 cases (4347 patients) were eligible for analysis. Three MET interventions related to the phacoemulsification/intraocular lens pathway occurred in the 2-year study period, resulting in an intervention rate of 0.04%. None of the interventions was intraoperative. All 3 patients were diagnosed as vasovagal collapse and recuperated uneventfully. No hospital admittance was required. Eight other incidents occurred within the general ophthalmology outpatient unit population during the study period. CONCLUSIONS: Cataract surgery can be safely performed in an outpatient clinic, in the absence of the anesthesia service and with limited workup and monitoring. Basic first aid and basic life support skills seem to be sufficient in case of an adverse event. An MET provides a generous failsafe for this low-risk procedure.