Noninvasive Mean Arterial Pressure Research Articles

Accuracy of oscillometric blood pressure measurement using a Cardell Touch multiparameter monitor in anesthetized pigs.

To assess the accuracy of an oscillometric monitor in anesthetized pigs and its ability to track changes in mean arterial pressure (MAP) and to detect arterial hypotension and hypertension in reference to direct measurements. Mean arterial pressure was measured simultaneously from a catheter in a femoral artery and with an oscillometric cuff placed over the metatarsus in 9 anesthetized pigs (∼6 months old, 35 to 55 kg). Pigs were subjected to maneuvers to alter MAP. Paired values for invasive and noninvasive MAP (iMAP and NiMAP) were recorded every 2 minutes. Bland-Altman plots with bias, limits of agreement, and percentage error were constructed using each pair and the average of 5 consecutive values. Concordance was calculated using changes in MAP at 20-minute intervals. Receiver operating characteristics (ROC) curves were constructed to test NiMAP for detection of hypotension (< 70 mm Hg) and hypertension (≥ 120 mm Hg). Bias of NiMAP was -8.59 mm Hg for consecutive pairs and -8.85 mm Hg for averaged pairs, relative to iMAP. Limits of agreement and percentage error were reduced for averages (19%) over individual pairs (26%). Concordance was 82%. The area under the ROC curve for detecting hypotension with NiMAP was 0.936, with a best cutoff value of 63 mm Hg NiMAP. The area under the ROC curve for hypertension was 0.940, with a best cutoff value of 101 mm Hg NiMAP. Averaging several consecutive values improves the accuracy of NiMAP measurements. This device correctly tracked changes in MAP approximately 80% of the time and appears reliable for diagnosing arterial hypotension.

Comparison of the effects of intranasal and intramuscular midazolam–butorphanol–ketamine on intraocular pressure, tear production and sedation in New Zealand White rabbits

ObjectiveTo compare the effects of intranasal (IN) and intramuscular (IM) midazolam–butorphanol–ketamine on intraocular pressure (IOP), tear production (TP) and sedation in rabbits. Study designProspective, randomized, crossover experimental study. AnimalsFourteen male New Zealand White rabbits, aged 1–2 years, body mass 3.1 ± 0.8 kg (mean ± standard deviation). MethodsRabbits were administered midazolam (1 mg kg–1), butorphanol (1.5 mg kg–1) and ketamine (5 mg kg–1) via IN and IM routes. IOP, TP and sedation scores were assessed at 0 (before drug administration), 5, 15, 30, 45 and 60 minutes after drug administration. Heart rate (HR), respiratory rate (fR), rectal temperature (RT), noninvasive mean arterial blood pressure (MAP) and peripheral hemoglobin oxygen saturation (SpO2) were simultaneously recorded until 45 minutes after drug administration. The onset and duration of sedation and sedation scores were recorded. ResultsDrug delivery route had no significant impact on mean IOP (p = 0.271) or TP (p = 0.062), and there were no significant changes over time for IOP (p = 0.711) or TP (p = 0.372). Similarly, delivery route had no significant impact on HR (p = 0.747), fR (p = 0.872), RT (p = 0.379), MAP (p = 0.217) and SpO2 (p = 0.254). Sedation onset was faster with IN (3.0 ± 1.0 minutes) than with IM administration (4.9 ± 0.7 minutes) (p = 0.011), but sedation duration was significantly longer with IM (52.6 ± 7.2 minutes) than with IN delivery (30.7 ± 6.8 minutes) (p = 0.004). There was no significant difference in sedation scores between the two delivery routes at any of the recorded time points. Conclusions and clinical relevanceThe combination of midazolam–butorphanol–ketamine had minimal impact on physiological and ocular variables regardless of the route of administration, whereas IN drug administration led to a shorter onset and duration of action than IM administration.

Comparative Analysis of the Hemodynamic Effects of Remimazolam and Propofol During General Anesthesia: A Retrospective Study.

Hypotension is common during anesthesia induction. However, minimal hemodynamic effects of remimazolam anesthesia have been reported. We hypothesized that remimazolam would have weaker hemodynamic effects than would propofol. To test this, we simultaneously evaluated the hemodynamics using the estimated continuous cardiac output (esCCO) system and heart rate variability (HRV) during anesthesia induction. This was a single-center, observational, retrospective study of patients undergoing dental surgery under general anesthesia between 2020 and 2022. Seventy patients were divided into two groups: remimazolam (R group; n=34) and propofol (P group; n=36). The information obtained from the anesthesia records, patient information, esCCO system parameters, and HRV were integrated and analyzed. The percentages of various parameters were set to 100% for the pre-induction phase as the baseline. The %MAP (noninvasive mean arterial blood pressure) decreased over a narrower range in the R compared to the P group (-17.8% (-26.3%, -11.9%) vs. -22.6% (-32.9%, -17.0%); P=0.039). The %HR (heart rate) increased significantly in the R group and decreased in the P group (+10.7% (+6.5%, +18.6%) vs. -6.5% (-14.5%, +8.4%); P<0.01). The %SVesCCO(stroke volume calculated using the esCCO system) decreased significantly in both groups, but the R group showed a smaller difference compared to the P group (- 5.1% (-7.7%, -2.1%) vs. -10.0% (-13.8%, -5.6%); P<0.01). The rates of change in %LF nu (normalized unit of low frequency) and %HF nu (normalized unit of high frequency) were lower for the R than for the P group, although the difference was not significant (+6.8% (-14.5%, 32.4%) vs. +9.2% (-7.2%, +59.7%), P=0.30; +7.9% (-51.0%, +66.9%) vs. +22.8% (-26.1%, +61.6%), P=0.57). Remimazolam demonstrated a lower MAP reduction rate than propofol. A compensatory increase in HR occurred with a decrease in stroke volume. However, the HR increase was not attributable to the autonomic nervous system.

A comparison of invasive arterial blood pressure measurement with oscillometric non-invasive blood pressure measurement in patients with sepsis.

This study aimed to compare non-invasive oscillometric blood pressure (NIBP) measurement with invasive arterial blood pressure (IBP) measurement in patients with sepsis. We conducted a retrospective study to evaluate the agreement between IBP and NIBP using the Medical Information Mart for Intensive Care IV (MIMIC-IV) database. Paired blood pressure measurements of mean arterial pressure (MAP), systolic blood pressure (SBP), and diastolic blood pressure (DBP) were compared using Bland-Altman analysis and paired Student's t test. We also focus on the effect of norepinephrine (NE) on the agreement between the two methods and the association between blood pressure and mortality during intensive care unit (ICU) stay. A total of 96,673 paired blood pressure measurements from 6060 unique patients were analyzed in the study. In Bland-Altman analysis, the bias (± SD, 95% limits of agreement) was 6.21mmHg (± 12.05mmHg, -17.41 to 29.83mmHg) for MAP, 0.39mmHg (± 19.25mmHg, -37.34 to 38.12mmHg) for SBP, and 0.80mmHg (± 12.92mmHg, -24.52 to 26.12mmHg) for DBP between the two techniques. Similarly, large limits of agreement were shown in different groups of NE doses. NE doses significantly affected the agreement between IBP and NIBP. SBP between the two methods gave an inconsistent assessment of patients' risk of ICU mortality. IBP and NIBP were not interchangeable in septic patients. Clinicians should be aware that non-invasive MAP was clinically and significantly underestimated invasive MAP.

Correlation between non-invasive measurements and intracardiac pressures using machine learning techniques

Abstract Background Solutions targeting early recognition of congestion in heart failure (HF) patients have the potential to prevent readmissions and can thus significantly reduce the burden on HF care. A gold standard measure of congestion is the invasively measured pulmonary capillary wedge pressure (PCWP). However, the invasive nature and accessibility of this measurement limits its clinical use. Non-invasive approximation of the PCWP using biosensing wearables could be a promising replacement for HF monitoring. Purpose The primary aim of this retrospective study was to create a model that estimates the PCWP based on non-invasive measurements of vital signs using both traditional statistics and machine learning (ML) techniques. Methods The study cohort consisted of right-sided heart catheterizations between 23/6/2017 and 19/8/2022. The following models were used: linear regression or classification, k-nearest neighbors, random forest, gradient boosting and multilayer perceptron. The outcome measure for the regression models was the continuous PCWP as measured during the catheterization. The two outcome classes for the classification models were low (&amp;lt;12 mmHg) and high (≥12 mmHg) PCWP. Non-invasive mean arterial blood pressure (MAP), saturation, heart rate, weight and temperature measured at most 72 hours before or after the catheterization were collected as the features for the models. Additionally, ECG-signals acquired during the catheterization were used to calculate the heart rate variability (HRV). The data was split in a validation (20%) and training (80%) data set. The models were built based on the training set and then applied on the validation set to determine the coefficient of determination (R2) for the regression models and the AUC of the ROC for the classification models. Results A total of 859 catheterizations were included of which 31.2% had HF as primary diagnosis. Average age of the cohort was 59 ± 14 years and 52.2% were male. In the HF group, the features with the highest correlation with the PCWP were the HRV and gender (Table 1). All the used regression techniques resulted in low R2 values of up to 0.10 and the classification techniques in AUC of the ROC values of up to 0.61 (Table 2). Conclusion In the current study, PCWP could not be approximated with non-invasive measurements using traditional statistics and ML techniques. These findings support the notion that traditional measures for monitoring HF are poorly correlated with hemodynamic parameters. Perhaps repeated measurements over time could overcome the shortcomings of a single vital signs measurement for congestion evaluation. Future prospective research is needed to evaluate the potential of wearable devices measuring trends over a longer period and their potential in predicting hemodynamics.

A prospective comparison of invasive and non-invasive blood pressure in children undergoing cardiac catheterization.

Blood pressure measurement is a standard of monitoring during general anesthesia. Invasive measurement is considered the gold standard but is less commonly used than non-invasive. Automated oscillometric blood pressure devices measure the mean arterial pressure (MAP) and use an algorithm to determine the systolic and diastolic pressures. Few devices have been validated in children, particularly during anesthesia. Few studies have assessed the agreement between invasive and non-invasive blood pressure measurements in children. This was a multi-center prospective observational study of children under 16 years undergoing cardiac catheterization with general anesthesia. Paired invasive and non-invasive blood pressure measurements were recorded for each patient during stable periods of the procedure. Correlation within and between sites was assessed with Pearson's correlation coefficient, and agreement was examined using Bland-Altman methodology to determine bias. Agreement during episodes of hypotension and for age and weight was also determined. Bias greater than 5 mmHg and standard deviation greater than 8 mmHg was considered clinically significant. The primary end point was agreement of MAP measurements. A total of 683 paired blood pressure values were collected from 254 children in three pediatric hospitals. Median [IQR] age and weight were 3 [1-7] years and 13.9 [8-23] Kg. The overall bias (SD) for mean arterial pressure values was 7.2 (11.4) mmHg. During hypotension (190 readings), the bias (SD) was 15 (11.0) mmHg. The non-invasive MAP was frequently higher than invasive MAP during infancy, and lower in older children. Automated oscillometric blood pressure measurement is unreliable in anesthetized children during cardiac catheterization. Invasive pressure measurement should be considered for high-risk cases.

Sedative and cardiopulmonary effects of intranasal butorphanol with midazolam or dexmedetomidine in New Zealand white rabbits.

This study aimed to compare the sedative and cardiopulmonary effects of intranasal (IN) administration of dexmedetomidine-butorphanol (DB) and midazolam-butorphanol (MB) combinations in New Zealand white rabbits. Eight New Zealand white rabbits were sedated by IN administration of a combination of 0.1mg/kg dexmedetomidine and 0.4mg/kg butorphanol (DB treatment) and 2mg/kg midazolam and 0.4mg/kg butorphanol (MB treatment). The electrocardiogram, pulse rate (PR), respiratory frequency (fR ), arterial haemoglobin oxygen saturation (SpO2 ), fraction of expired carbon dioxide (EtCO2 ), rectal temperature (RT), noninvasive mean arterial pressure (MAP), noninvasive systolic arterial pressure (SAP) and diastolic arterial pressure (DAP) were recorded. The onset of sedation, duration of sedation and sedation score (SS) were also noted. There were no significant differences in the EtCO2 , RT, MAP, SAP and DAP measurements between treatments. The PR significantly decreased in DB compared with MB over time (p = 0.001). Compared with baseline, SpO2 decreased over time in both treatments. The SS was significantly elevated over time in DB compared with MB (p = 0.002). No pharmacokinetic information was available for either treatment, so the findings should be interpreted cautiously. IN DB provides more effective sedation than MB, but cardiopulmonary impairment was observed in both treatments.

Sedative and cardiorespiratory effects of intranasal atomized alfaxalone in Japanese White rabbits

ObjectiveTo investigate the sedative and cardiorespiratory effects of intranasal atomization (INA) of alfaxalone using a mucosal atomization device in Japanese White rabbits. Study designRandomized, prospective, crossover study. AnimalsA total of eight healthy female rabbits, weighing 3.6–4.3 kg and aged 12–24 months. MethodsEach rabbit was randomly assigned to four INA treatments administered 7 days apart: Control treatment, 0.15 mL 0.9% saline in both nostrils; treatment INA0.3, 0.15 mL 4% alfaxalone in both nostrils; treatment INA0.6, 0.3 mL 4% alfaxalone in both nostrils; treatment INA0.9, 0.3 mL 4% alfaxalone in left, then right, then left nostril. Sedation was scored 0–13 using a composite measure scoring system for rabbits. Simultaneously, pulse rate (PR), respiratory rate (fR), noninvasive mean arterial pressure (MAP), peripheral hemoglobin oxygen saturation (SpO2) and arterial blood gases were measured until 120 minutes. The rabbits breathed room air during the experiment and were administered flow-by oxygen when hypoxemia (SpO2 <90% or PaO2 <60 mmHg; 8.0 kPa) developed. Data were analyzed using the Fisher's exact test and the Friedman test (p < 0.05). ResultsNo rabbit was sedated in treatments Control and INA0.3. All rabbits in treatment INA0.9 developed loss of righting reflex for 15 (10–20) minutes [median (25th–75th percentile)]. Sedation score significantly increased from 5 to 30 minutes in treatments INA0.6 and INA0.9 with maximum scores of 2 (1–4) and 9 (9–9), respectively. fR decreased in an alfaxalone dose-dependent manner and one rabbit developed hypoxemia in treatment INA0.9. No significant changes were observed in PR and MAP. Conclusions and clinical relevanceINA alfaxalone resulted in dose-dependent sedation and respiratory depression in Japanese White rabbits to values considered not clinically relevant. Further investigation of INA alfaxalone in combination with other drugs is warranted.

Effects of alfaxalone on induction quality of inhalation anesthesia in domestic pigeons (Columba livia domestica).

Several studies have documented the effects of anesthesia on pigeons. However, previous studies using pigeons have not examined a combination of injection and inhalation anesthesia. This study aimed to evaluate the effects of intramuscular (IM) administration of alfaxalone in conjunction with mask induction on the quality of isoflurane anesthesia in healthy domestic pigeons (Columba livia domestica). In a randomized, double-blind, crossover study consisting of two phases, six healthy adult pigeons were anesthetized twice with a washout period of 7 days. In each phase, the pigeons were randomly assigned IM administration of either alfaxalone (4 mg/kg) or an equal volume of normal saline. After 20 min, anesthesia was induced with isoflurane through a face mask. Once voluntary movement of the limbs and eyelids ceased, the face mask was removed, and the trachea was intubated. The quality of anesthesia was assessed by scoring sedation prior to anesthetic induction, induction, and recovery. Heart rate, respiratory rate, cloacal temperature, and noninvasive systolic, diastolic, and mean arterial pressure were recorded before the IM injection (baseline) and during the procedure. The minimum anesthetic concentration of isoflurane was determined using the "bracketing" method. Moderate sedation (sedation scores of 2 and 3) was observed only with alfaxalone administration. In the alfaxalone group, the induction score was significantly higher (better induction quality) than in the control group (P=0.041). The combination of alfaxalone and mask induction was effective for inhalation anesthesia in pigeons.

Validity and success rate of noninvasive mean arterial blood pressure measurements in cf-LVAD patients: A technical review.

The life expectancy of patients with a continuous flow left ventricular assist device (cf-LVAD) is increasing. Adequate determination and regulation of mean arterial pressure (MAP) is important to prevent adverse events. Given the low pulsatility characteristics in these patients, standard blood pressure equipment is inadequate to monitor MAP and not recommended. We provide an overview of currently available noninvasive techniques, using an extensive search strategy in three online databases (Pubmed, Scopus and Google Scholar) to find validation studies using invasive intra-arterial blood pressure measurement as a reference. Mean differences with the reference values smaller than 5 ± 8 mm Hg were considered acceptable. After deduplication, screening, and exclusion of incorrect sources, eleven studies remained with 3139 successful MAP measurements in 386 patients. Four noninvasive techniques, using Doppler, pulse oximetry, finger cuff volume clamp, or slow upper arm cuff deflation, were identified and evaluated for validity and success rate in cf-LVAD patients. Here, a comprehensive technical background of the blood pressure measurement methods is provided in combination with a clinical use comparison. Of the reported noninvasive techniques, slow cuff devices performed most optimally (mean difference 1.3 ± 5.2 mm Hg). Our results are encouraging and indicate that noninvasive blood pressure monitoring options with acceptable validity and success rate are available. Further technical development and validation is warranted for the growing population of patients on long-term cf-LVAD support.

Sevoflurane Sparing Effect of Morphine in Tegus (Salvator merianae) – A Preliminary Study

This study aimed to determine the minimum anesthetic concentration (MAC) of sevoflurane in tegus (Salvator merianae) and the morphine-sparing effect on this variable. In a prospective, non-blinded, crossover study, MAC was first determined in 6 tegus under sevoflurane anesthesia alone (MACSEVO) and then following intramuscular administration of morphine (10 mg/kg), administered 3 hour before sevoflurane anesthesia (MACSEVO+MOR). A standard bracketing technique was applied to determine the MAC by an electrical supramaximal noxious stimulus (50 Hz, 30 mA) delivered at the base of the tail of the tegus. The end-tidal sevoflurane fraction was reduced or increased by 10% in any evidence of negative or positive motor responses, respectively. The MAC was calculated as the mean of the 2 highest successive sevoflurane concentrations that permitted positive responses and the 2 lowest that prevented positive responses. Heart rate, esophageal temperature, and noninvasive mean arterial blood pressure were assessed every 10 minutes. The MAC was significantly different between MACSEVO (2.41 ± 0.06%) and MACSEVO+MORF (1.88 ± 0.43%) (P = .007), with a mean ± SD morphine-induced reduction in the sevoflurane MAC of 22 ± 18% (P = .0158). Heart rate, mean arterial blood pressure, and esophageal temperature did not differ between groups or within groups over time. Results showed that intramuscular premedication with 10 mg/kg morphine produced a sevoflurane sparing effect in tegus with no significant impact on cardiovascular variables.

Dynamic cerebral autoregulation during early orthostatic exercise in patients with severe traumatic brain injury: Further exploratory analyses from a randomized clinical feasibility trial

In patients with severe traumatic brain injury, there is limited evidence of the clinical effect of early orthostatic exercise, although such exercise may strengthen systemic or cerebral hemodynamic responses to head-up tilt, thereby minimizing orthostatic intolerance. We measured dynamic cerebral autoregulation (dCA) and the occurrence of orthostatic intolerance after four weeks of regular orthostatic exercise by head-up tilt using a tilt table with integrated stepping using the ERIGO® tilt-table and comparing it to standard care. Thirty-four patients with severe traumatic brain injury admitted to a neurocritical care unit were included in this randomized clinical trial. Middle cerebral artery blood flow velocity (MCAv), non-invasive mean arterial pressure, heart rate and PaCO2 were recorded; dCA was measured by the non-invasive mean flow index (nMxa). Transition from the supine position to head-up tilt triggered a 10–16% decrease in MCAv and increased nMxa in both groups at all time points (P < 0.05), with no differences between groups. There was no difference in the number of episodes with orthostatic intolerance (5 vs 3; 1 vs 2; 1 vs 0) at baseline, two weeks and four weeks, respectively, and no association between changes in PaCO2-adjusted nMxa and the occurrence of orthostatic reactions (P = 0.35). Early orthostatic exercise does not affect dynamic cerebral autoregulation and does not protect against orthostatic intolerance in patients with severe traumatic brain injury. Trial registration: ClinicalTrials.gov identifier: NCT02924649. Registered on 3rd October 2016.

Comparison of anesthetic effects of tiletamine–zolazepam–medetomidine or ketamine–medetomidine in captive Amur leopard cats (Prionailurus bengalensis euptailurus)

ObjectiveTo evaluate the effects and utility of tiletamine–zolazepam–medetomidine (TZM) and ketamine–medetomidine (KM) for anesthesia of Amur leopard cats (Prionailurus bengalensis euptailurus). Study designProspective, randomized experimental trial. AnimalsA total of six female (3.70 ± 0.49 kg) and six male (5.03 ± 0.44 kg; mean ± standard deviation) Amur leopard cats aged 2–6 years. MethodsEach animal was administered four protocols separated by ≥3 weeks. Each protocol included medetomidine (0.05 mg kg–1) combined with tiletamine–zolazepam (1 mg kg–1; protocol MTZLO); tiletamine–zolazepam (2 mg kg–1; protocol MTZHI); ketamine (2 mg kg–1; protocol MKLO); or ketamine (4 mg kg–1; MKHI) administered intramuscularly. At time 0 (onset of lateral recumbency) and 30 minutes, heart rate (HR), respiratory rate (fR), rectal temperature, noninvasive mean arterial pressure (MAP) and hemoglobin oxygen saturation (SpO2) were recorded. Times to onset of lateral recumbency, duration of anesthesia and time to standing were recorded. ResultsOverall, animals were anesthetized with all protocols within 10 minutes, anesthesia was maintained ≥57 minutes, and recovery (time from the first head lift to standing) was completed within 5 minutes. During anesthesia with all protocols, HR, fR, rectal temperature, SpO2 and MAP were 99–125 beats minute–1, 33–44 breaths minute–1, 37.6–39.4 °C, 90–95% and 152–177 mmHg, respectively. No adverse event was observed. Conclusions and clinical relevanceTZM and KM at various dosages resulted in rapid onset of anesthesia, duration of >57 minutes and rapid recovery without administration of an antagonist. Accordingly, all these combinations are useful for anesthetizing Amur leopard cats and for performing simple procedures. However, the low doses of the anesthetic agents are recommended because there was no difference in duration of anesthesia between the dose rates studied.

Predicting hypotension in the ICU using noninvasive physiological signals

Hypotension frequently occurs in Intensive Care Units (ICU), and its early prediction can improve the outcome of patient care. Trends observed in signals related to blood pressure (BP) are critical in predicting future events. Unfortunately, the invasive measurement of BP signals is neither comfortable nor feasible in all bed settings. In this study, we investigate the performance of machine-learning techniques in predicting hypotensive events in ICU settings using physiological signals that can be obtained noninvasively. We show that noninvasive mean arterial pressure (NIMAP) can be simulated by down-sampling the invasively measured MAP. This enables us to investigate the effect of BP measurement frequency on the algorithm's performance by training and testing the algorithm on a large dataset provided by the MIMIC III database. This study shows that having NIMAP information is essential for adequate predictive performance. The proposed predictive algorithm can flag hypotension with a sensitivity of 84%, positive predictive value (PPV) of 73%, and F1-score of 78%. Furthermore, the predictive performance of the algorithm improves by increasing the frequency of BP sampling.

Cerebrovascular responses to graded exercise in young healthy males and females.

Although systemic sex‐specific differences in cardiovascular responses to exercise are well established, the comparison of sex‐specific cerebrovascular responses to exercise has gone under‐investigated especially, during high intensity exercise. Therefore, our purpose was to compare cerebrovascular responses in males and females throughout a graded exercise test (GXT). Twenty‐six participants (13 Females and 13 Males, 24 ± 4 yrs.) completed a GXT on a recumbent cycle ergometer consisting of 3‐min stages. Each sex completed 50W, 75W, 100W stages. Thereafter, power output increased 30W/stage for females and 40W/stage for males until participants were unable to maintain 60‐80 RPM. The final stage completed by the participant was considered maximum workload(W max). Respiratory gases (End‐tidal CO2, EtCO2), middle cerebral artery blood velocity (MCAv), heart rate (HR), non‐invasive mean arterial pressure (MAP), cardiac output (CO), and stroke volume (SV) were continuously recorded on a breath‐by‐breath or beat‐by‐beat basis. Cerebral perfusion pressure, CPP = MAP (0. 7,355 distance from heart‐level to doppler probe) and cerebral vascular conductance index, CVCi = MCAv/CPP 100mmHg were calculated. The change from baseline (Δ) in MCAv was similar between the sexes during the GXT (p = .091, ω p 2 = 0.05). However, ΔCPP (p < .001, ω p 2 = 0.25) was greater in males at intensities ≥ 80% W max and ΔCVCi (p = .005, ω p 2 = 0.15) was greater in females at 100% W max. Δ End‐tidal CO2 (ΔEtCO2) was not different between the sexes during exercise (p = .606, ω p 2 = −0.03). These data suggest there are sex‐specific differences in cerebrovascular control, and these differences may only be identifiable at high and severe intensity exercise.

Impact of Pump Speed on Hemodynamics With Exercise in Continuous Flow Ventricular Assist Device Patients.

At fixed speed, the spontaneous increase in pump flow accompanying exercise in patients with continuous flow left ventricular assist devices (cfLVADs) is slight in comparison to normal physiologic response, limiting exercise capacity. We systematically exercised 14 patients implanted with an isolated HeartWare HVAD undergoing routine right heart catheterization at baseline and at maximal safe pump speed. In addition to hemodynamics, mixed venous oxygen saturation (SvO2), echocardiography and noninvasive mean arterial pressure, and heart rate were measured. Significantly greater pump flows were achieved with maximum pump speed compared with baseline speed at rest (mean ± standard deviation [SD]: 5.0 ± 0.7 vs. 4.6 ± 0.8 L/min) and peak exercise (6.7 ± 1.0 vs. 5.9 ± 0.9 L/min, p = 0.001). Pulmonary capillary wedge pressure was significantly reduced with maximum pump speed compared to baseline pump speed at rest (10 ± 4 vs. 15 ± 5 mmHg, p < 0.001) and peak exercise (27 ± 8 vs. 30 ± 8 mmHg, p = 0.002). Mixed venous oxygen saturation decreased with exercise (p < 0.001) but was unaffected by changes in pump speed. In summary, although higher pump speeds synergistically augment the increase in pump flow associated with exercise and blunt the exercise-induced rise in left heart filling pressures, elevated filling pressures and markedly diminished SvO2 persist at maximal safe pump speed, suggesting that physiologic flow increases are not met by isolated cfLVADs in the supported failing heart.

Effect of phentolamine mesylate on regression of lidocaine–epinephrine epidural anaesthesia in sheep

ObjectiveTo determine the impact of epidural phentolamine on the duration of anaesthesia following epidural injection of lidocaine–epinephrine. Study designBlinded randomized experimental study. AnimalsA group of 12 adult ewes weighing 25.7 ± 2.3 kg and aged 8–9 months. MethodsAll sheep were administered epidural lidocaine (approximately 4 mg kg–1) and epinephrine (5 μg mL–1). Of these, six sheep were randomized into three epidural treatments, separated by 1 week, administered 30 minutes after lidocaine–epinephrine: SAL: normal saline, PHE1: phentolamine (1 mg) and PHE2: phentolamine (2 mg). The other six sheep were administered only epidural lidocaine–epinephrine: treatment LIDEP. Each injection was corrected to 5 mL using 0.9% saline. Noxious stimuli were pinpricks with a hypodermic needle and skin pinch with haemostatic forceps to determine the onset and duration of sensory and motor block. Heart rate, noninvasive mean arterial pressure (MAP), respiratory rate and rectal temperature were recorded. ResultsThe onset times were not different among treatments. Duration of sensory block was significantly shorter in SAL (57.5 ± 6.2 minutes), PHE1 (60.7 ± 9.0 minutes) and PHE2 (62.0 ± 6.7 minutes) than in LIDEP (81.7 ± 13.4 minutes) (p < 0.05). Duration of motor blockade was significantly shorter in PHE1 (59.4 ± 5.4 minutes) and PHE2 (54.3 ± 4.0 minutes) than in SAL (84.8 ± 7.0 minutes) and LIDEP (91.5 ± 18.2 minutes) (p < 0.01). MAP in PHE2 was decreased at 10 minutes after administration of phentolamine (p < 0.05). Conclusion and clinical relevanceEpidural administration of 5 mL normal saline after epidural injection of lidocaine–epinephrine reduced the duration of sensory but not motor block in sheep. Epidural administration of phentolamine diluted to the final volume of 5 mL diminished both the duration of sensory and motor block in sheep administered epidural lidocaine–epinephrine.

Pharmacokinetics of midazolam in sevoflurane-anesthetized cats

ObjectiveTo estimate the pharmacokinetics of midazolam and 1-hydroxymidazolam after midazolam administration as an intravenous bolus in sevoflurane-anesthetized cats. Study designProspective pharmacokinetic study. AnimalsA group of six healthy adult, female domestic cats. MethodsAnesthesia was induced and maintained with sevoflurane. After 30 minutes of anesthetic equilibration, cats were administered midazolam (0.3 mg kg–1) over 15 seconds. Venous blood was collected at 0, 1, 2, 4, 8, 15, 30, 45, 90, 180 and 360 minutes after administration. Plasma concentrations for midazolam and 1-hydroxymidazolam were measured using high-pressure liquid chromatography. The heart rate (HR), respiratory rate (fR), rectal temperature, noninvasive mean arterial pressure (MAP) and end-tidal carbon dioxide (Pe′CO2) were recorded at 5 minute intervals. Population compartment models were fitted to the time–plasma midazolam and 1-hydroxymidazolam concentrations using nonlinear mixed effect modeling. ResultsThe pharmacokinetic model was fitted to the data from five cats, as 1-hydroxymidazolam was not detected in one cat. A five-compartment model best fitted the data. Typical values (% interindividual variability where estimated) for the volumes of distribution for midazolam (three compartments) and hydroxymidazolam (two compartments) were 117 (14), 286 (10), 705 (14), 53 (36) and 334 mL kg–1, respectively. Midazolam clearance to 1-hydroxymidazolam, midazolam fast and slow intercompartmental clearances, 1-hydroxymidazolam clearance and 1-hydroxymidazolam intercompartment clearance were 18.3, 63.5 (15), 22.1 (8), 1.7 (67) and 3.8 mL minute–1 kg–1, respectively. No significant changes in HR, MAP, fR or Pe′CO2 were observed following midazolam administration. Conclusion and clinical relevanceIn sevoflurane-anesthetized cats, a five-compartment model best fitted the midazolam pharamacokinetic profile. There was a high interindividual variability in the plasma 1-hydroxymidazolam concentrations, and this metabolite had a low clearance and persisted in the plasma for longer than the parent drug. Midazolam administration did not result in clinically significant changes in physiologic variables.

Comparative effects of open-lung positive end-expiratory pressure (PEEP) and fixed PEEP on respiratory system compliance in the isoflurane anaesthetised healthy dog

This study was performed to assess the effects of open-lung positive end-expiratory pressure (OL-PEEP) following stepwise recruitment manoeuvre (RM) and those of a fixed PEEP of 5 cm H2O without previous RM on respiratory system compliance (Crs) and selected cardiovascular variables in healthy dogs under general anaesthesia. Forty-five healthy client-owned dogs undergoing surgery were anaesthetised and mechanically ventilated (tidal volume, VT = 10–12 mL/kg; PEEP = 0 cm H2O) for 1 min (baseline) and randomly allocated into zero positive end-expiratory pressure (ZEEP), PEEP (5 cm H2O) and OL-PEEP treatment groups. In the OL-PEEP group, a stepwise RM was performed and the individual OL-PEEP was subsequently applied. The Crs, heart rate (HR) and non-invasive mean arterial pressure (NIMAP) were registered at baseline and then every 10 min during 60 min.In the ZEEP group, Crs decreased from baseline. In the PEEP group, Crs was not different from either baseline or ZEEP group values. In the OL-PEEP group, Crs was higher than both baseline and ZEEP group values at all time points as well as of those in the PEEP group during at least 20 min after RM. There were no differences for HR and NIMAP between groups. A clinically relevant hypotension following RM was observed in 40% of dogs. Therefore, an individually set OL-PEEP following stepwise RM improved Crs in anaesthetised healthy dogs, although transient but clinically relevant hypotension was observed during RM in some dogs. Fixed PEEP of 5 cm H2O without previous RM did not improve Crs, although it prevented it from decreasing.

A Study of Systolic, Diastolic Blood Pressure and Non-Invasive Mean Arterial Pressure with Regard to Adverse Events in Acute Hemorrhagic Stroke in A Rural Tertiary Care Hospital

A Study of Systolic, Diastolic Blood Pressure and Non-Invasive Mean Arterial Pressure with Regard to Adverse Events in Acute Hemorrhagic Stroke in A Rural Tertiary Care Hospital