Comparison of noninvasive oscillometric and intra-arterial blood pressure measurements in hyperacute stroke

Comparison of intraoperative blood pressure values measured by noninvasive versus invasive methods during normotension, hypertension, and hypotension

Background and Aims

Monitoring of intraoperative blood pressure (BP) is essential. We aimed to compare BP values simultaneously recorded by invasive and noninvasive methods under general anesthesia (GA) during normotension, hypertension, and hypotension. Mean arterial pressure (MAP) values calculated by the automated technique were also compared to the values obtained using predefined formula.

Material and Methods

An observational, prospective study was conducted in 250 adult patients undergoing elective surgeries under GA. Before induction, noninvasive blood pressure (NIBP) was measured in the arm in a supine position using an automated oscillometer. Radial artery in the opposite arm was cannulated. NIBP and arterial BP (ABP) were recorded simultaneously during normotension, hypotension, and hypertension.

Results

During normotension and hypertension, systolic BP (SBP) measured by NIBP and ABP were comparable. Diastolic BP (DBP) and MAP during normotension were significantly higher with NIBP (73.65 ± 7.73 vs. 65.69 ± 8.39 and 87.79 ± 8.43 vs. 84.24 ± 8.82, respectively). During hypertension, DBP and MAP were significantly higher with NIBP (90.44 ± 11.61 vs. 78.59 ± 11.09 and 111.67 ± 10.43 vs. 105.63 ± 11.06, respectively). During hypotension, SBP was significantly higher in ABP (91.14 ± 6.90 vs. 86.24 ± 6.06), and DBP and MAP were comparable. Comparison of MAP measured by ABP and NIBP techniques with the MAP calculated using predefined formula in normotension showed significantly higher values with the automated technique.

Conclusions

During normotension and hypertension, DBP and MAP showed significantly higher values with the NIBP technique compared to ABP, with comparable SBP values. During hypotension, SBP showed significantly higher values with the ABP technique, with comparable DBP and MAP. MAP obtained using predefined formula and automated method in normotension was significantly higher with the automated technique.

Intra-beat biomarker for accurate continuous non-invasive blood pressure monitoring

Accurate continuous non-invasive blood pressure (CNIBP) monitoring is the holy grail of digital medicine but remains elusive largely due to significant drifts in signal and motion artifacts that necessitate frequent device recalibration. To address these challenges, we developed a unique approach by creating a novel intra-beat biomarker (Diastolic Transit Time, DTT) to achieve highly accurate blood pressure (BP) estimations. We demonstrated our approach’s superior performance, compared to other common signal processing techniques, in eliminating stochastic baseline wander, while maintaining signal integrity and measurement accuracy, even during significant hemodynamic changes. We applied this new algorithm to BP data collected using non-invasive sensors from a diverse cohort of high acuity patients and demonstrated that we could achieve close agreement with the gold standard invasive arterial line BP measurements, for up to 20 min without recalibration. We established our approach's generalizability by successfully applying it to pulse waveforms obtained from various sensors, including photoplethysmography and capacitive-based pressure sensors. Our algorithm also maintained signal integrity, enabling reliable assessments of BP variability. Moreover, our algorithm demonstrated tolerance to both low- and high-frequency motion artifacts during abrupt hand movements and prolonged periods of walking. Thus, our approach shows promise in constituting a necessary advance and can be applied to a wide range of wearable sensors for CNIBP monitoring in the ambulatory and inpatient settings.

Systolic blood pressure measurements are unreliable for the management of acute spontaneous intracerebral hemorrhage

PURPOSE

Whether systolic blood pressure (SBP) is reliable in acute spontaneous intracerebral (sICH) by assessing agreement between simultaneous BP measurements obtained from cuff non-invasive blood pressure (NIBP) and radial arterial invasive blood pressure (AIBP) devices.

MATERIAL AND METHODS

Among 766 prospectively screened sICH subjects, 303 (39.5%) had NIBP and AIBP measurements. During the first 24 h, 2157 simultaneous paired measurement readings were abstracted. Paired NIBP/AIBP measurements were included in a Bland-Altman technique with 95% agreement limits and coefficients from regression analysis derived from a bootstrap procedure.

RESULTS

Variance for SBP was 66.1 mmHg, which was larger than the 44.3 mg Hg for diastolic blood pressure (DBP) or the 46.1 mmHg for mean arterial pressure (MAP). Pairwise comparison of mean biases showed a significant difference between SBP when compared to DBP (p < 0.0001) or MAP (p < 0.0001). The mean bias between DBP and MAP was not different (p = 0.68). Regression-based Bland Altman analysis found significant bias (slope -0.16, 95% CI -0.23, -0.09, p < 0.05) over the range of mean SBP. Bias over the range of mean DBP or MAP was not significant.

CONCLUSIONS

We concluded that SBP is an unreliable blood pressure measurement in patients with sICH.

Comparing Intra-Arterial, Auscultatory, and Oscillometric Measurement Methods for Arterial Blood Pressure

AIM

This study aimed to compare the measurement results of arterial blood pressure obtained through intra-arterial, auscultatory, and oscillometric methods.

METHOD

This prospective and descriptive study was conducted with 180 patients hospitalized in the intensive care units of cardiovascular surgery and anesthesia. Arterial blood pressures of the patients in the study were measured with 3 methods, and the mean arterial pressure values obtained by each method were analyzed to find out whether they were different or consistent.

RESULTS

The average systolic blood pressure value using the intra-arterial method was found to be 125.47 ± 21.39 mm Hg, and the average of diastolic blood pressure measurement obtained using the oscillometric method was the highest (73.91 ± 10.62 mm Hg). The highest correlation was seen between the arterial BP measurements of the intra-arterial and auscultatory methods (systolic [0.96] and diastolic [0.90]). According to the British and Irish Hypertension Society protocol, a very good agreement between the diastolic blood pressure values and a good agreement between the systolic blood pressure values were obtained.

CONCLUSION

The measurement results obtained through the auscultatory method more consistent with the results obtained through the intra-arterial method compared with those obtained using the oscillometric method.

Arterial or cuff pressure: Clinical predictors among patients in shock in a critical care resuscitation unit

OBJECTIVES

Blood pressure (BP) measurement is essential for managing patients with hypotension. There are differences between invasive arterial blood pressure (IABP) and noninvasive blood pressure (NIBP) measurements. However, the clinical applicability of these differences in patients with shock [need for vasopressor or serum lactate ≥ 4 millimole per liter (mmol/L)] has not been reported. This study investigated differences in IABP and NIBP as well as changes in clinical management in critically ill patients with shock.

METHODS

This was a retrospective study involving adult patients admitted to the Critical Care Resuscitation Unit (CCRU). Adult patients who received IABP upon admission between 01/01/2017-12/31/2017 with non-hypertensive diseases were eligible. The primary outcome, clinically relevant difference (CRD), was defined as difference of 10 mm of mercury (mmHg) between IABP and NIBP and change of blood pressure management according to goal mean arterial pressure (MAP) ≥ 65 mmHg. We performed forward stepwise multivariable logistic regression to measure associations.

RESULTS

Sample size calculation recommended 200 patients, and we analyzed 263. 121 (46%) patients had shock, 23 (9%) patients had CRD. Each mmol/L increase in serum lactate was associated with 11% higher likelihood of having CRD (OR 1.11, 95%CI 1.002-1.2). Peripheral artery disease and any kidney disease was significantly associated with higher likelihood of MAP difference ≥ 10 mmHg.

CONCLUSION

Approximately 9% of patients with shock had clinically-relevant MAP difference. Higher serum lactate was associated with higher likelihood of CRD. Until further studies are available, clinicians should consider using IABP in patients with shock.

Association Between Central-Peripheral Blood Pressure Amplification and Structural and Functional Cardiac Properties in Children, Adolescents, and Adults: Impact of the Amplification Parameter, Recording System and Calibration Scheme

INTRODUCTION

Systolic blood pressure (SBPA) and pulse pressure amplification (PPA) were quantified using different methodological and calibration approaches to analyze (1) the association and agreement between different SBPA and PPA parameters and (2) the association between these SBPA and PPA parameters and left ventricle (LV) and atrium (LA) structural and functional characteristics.

METHODS

In 269 healthy subjects, LV and LA parameters were echocardiography-derived. SBPA and PPA parameters were quantified using: (1) different equations (n = 9), (2) methodological approaches (n = 3): brachial sub-diastolic (Mobil-O-Graph®) and supra-systolic oscillometry (Arteriograph®) and aortic diameter waveform re-calibration (RCD; ultrasonography), and (3) using three different calibration schemes: systo-diastolic (SD), calculated mean (CM) and oscillometric mean (OscM).

RESULTS

SBPA and PPA parameters obtained with different equations, techniques, and calibration schemes show a highly variable association level (negative, non-significant, and/or positive) among them. The association between SBPA and PPA with cardiac parameters were highly variable (negative, non-significant, or positive associations). Differences in BPA parameter data between approaches were more sensitive to the calibration method than to the device used. Both, SBPA and PPA obtained with brachial sub-diastolic technique and calibrated to CM or OscM showed higher levels of association with LV and LA structural characteristics.

CONCLUSIONS

Our data show that many of the parameters that assume to quantify the same phenomenon of BPA are not related to each other in the different age groups. Both, SBPA and PPA obtained with brachial sub-diastolic technique and calibrated to CM or OscM showed higher levels of association with LV and LA structural characteristics.

Microwave Ablation of Adrenal Tumors in Patients With Continuous Intra-Arterial Blood Pressure Monitoring Without Prior Alpha-Adrenergic Blockade: Safety and Efficacy

PURPOSE

Evaluate the safety and efficacy of adrenal microwave ablation performed with continuous intra-arterial blood pressure monitoring (IABPM) and without alpha-adrenergic blockade (AAB) as pretreatment.

MATERIAL AND METHODS

A single-center, retrospective review of all percutaneous adrenal microwave ablation performed between 2011 and 2018. Microwave ablation was completed on 11 patients, with a total of 15 adrenal tumors with a mean size of 3.3 cm (1.4-6.9 cm) treated metastatic RCC, HCC, esophageal carcinoma, adrenal adenoma. Cases were performed without prior AAB, but with continuous IABPM and rapid intervention using short-acting antihypertensive medications.

RESULTS

There were no post-procedural episodes of hypertension, no neurological or cardiovascular complications, and no SIR moderate or worse adverse event complications. Mean intraprocedural maximum systolic blood pressure (SBP) was 211 mmHg (range: 132-288), with an average increase in SBP of 100 mmHg (range: 23-180). A hypertensive crisis (SBP ≥ 180 and/or DBP ≥ 120) occurred in 9 of the 15 procedures (60%) with a mean length of 3.0 min (range: 1-12). The technical success rate was 100% (15/15 procedures). The mean follow-up time was 2.4 years (range: 0.9-7.7 years), with primary and secondary efficacy rates of 77% and 87%, respectively, and an overall survival of 82%.

CONCLUSION

In this single-center retrospective study, microwave ablation of adrenal tumors without AAB was safe and effective when performed with continuous arterial line monitoring of vital signs and the use of short-acting, rapid-onset antihypertensive medications.

LEVEL OF EVIDENCE

Level 4, Case Series.

Blood Pressure measurements are site dependent in a cohort of patients with neurological illness

Blood pressure (BP) management is a crucial part of critical care that directly affects morbidity and mortality. While BP has become a mainstay in patient care, the accuracy and precision of BP measures across commonly used sites (left upper arm, right upper arm, etc.) and methods have not been established. This study begins to fill this gap in literature by testing the null hypothesis that BP measurement does not vary according to site. This is a prospective, non-randomized, cross-sectional study of 80 neurocritical care unit patients. Near simultaneous non-invasive blood pressure (NIBP) readings from 4 different locations (bilateral upper arm, bilateral wrist) and, when available, intra-arterial blood pressure readings (IABP) were included. Pearson correlation coefficients and one-way repeated measures ANOVA were used to observe the systolic, diastolic, and mean arterial pressure (MAP) correlations. The BP measured at the four most common sites (left upper arm, left wrist, right upper arm, right wrist) had adequate correlation coefficients but were statistically significantly different and highly unpredictable. The median inter-site systolic variability was 10 mmHg (IQR 2 to 10 mmHg). The median inter-site MAP variability was 6mmHg with an interquartile range (IQR) of 3 to 9 mmHg. As expected, the values correlated to show that patients with high BP in one site tended to have high BP in another site. However, the unpredictable inter-site variability is concerning within the clinical setting where oftentimes BP measurement site is not standardized but resulting values are nevertheless used for treatment. There is prominent inter-site variability of BP measured across the 4 most common measurement sites. The variability persists across non-invasive (NIBP) and invasive (IABP) methods of assessment.

Predictors of clinically relevant differences between noninvasive versus arterial blood pressure

OBJECTIVE

Blood pressure (BP) measurements are important for managing patients with hypertensive emergencies (HE). Previous studies showed that there was significant difference between IABP and NIBP but no information whether these differences changed management. Our study investigated the factors associated with the differences affecting BP management of patients with HE.

METHODS

This was a retrospective study involving adult patients admitted to a resuscitation unit. We screened all patients who received IABP upon admission between 06/01/2017 and 12/31/2017 as sample size calculation recommended 64 patients. Primary outcome was the clinical relevance of the difference of IABP vs. NIBP, which was defined as having both: a) difference of 10 mm of mercury (mmHg), and b) resulting in possible change of blood pressure managements according to treatment guidelines. We performed backward stepwise multivariable logistic regression to measure associations.

RESULTS

We analyzed 147 patients whose mean age was 69 (±16) years and included 69 (47%) patients with spontaneous intracerebral hemorrhage (sICH). Mean difference between IABP and NIBP was 21 (±16) mmHg while 41 (28%) patients who had difference affecting managements. In multivariable regression, sICH (Odd Ratios 13.5, 95%CI 2.3-79.5, p-value < 0.001) was significantly associated with clinically relevant difference between the two modalities of BP monitoring.

CONCLUSIONS

There was a large difference between IABP and NIBP among patients with hypertensive emergencies. Up to 30% of patients had clinically relevant differences. Patients with sICH were more likely to have differences affecting BP management. Further studies are needed to confirm our observation.

Evaluation and management of elevated blood pressures in hospitalized children

Elevated blood pressures (BP) are common among hospitalized children and, if not recognized and treated promptly, can lead to potentially significant consequences. Even though we have normative BP data and well-developed guidelines for the diagnosis and management of hypertension (HTN) in the ambulatory setting, our understanding of elevated BPs and their relationship to HTN in hospitalized children is limited. Several issues have hampered our ability to diagnose and manage HTN in the inpatient setting including the common presence of physiologic conditions, which are associated with transient BP elevations (i.e., pain or anxiety), non-standard approaches to BP measurement, a lack of clarity regarding appropriate diagnostic and therapeutic thresholds, and marginal outcome data. The purpose of this review is to highlight the issues and challenges surrounding BP monitoring, assessment of elevated BPs, and the diagnosis of HTN in hospitalized children. Extrapolating from currently available clinical practice guidelines and utilizing the best data available, we aim to provide guidelines regarding evaluation and treatment of elevated BP in hospitalized children.

Accuracy of blood pressure monitoring devices: a critical need for improvement that could resolve discrepancy in hypertension guidelines

Hypertension is the most significant modifiable risk factor for cardiovascular disease and contributes to the highest global burden of disease. Blood pressure (BP) measurement is among the most important of all medical tests, and it is critical for BP monitoring devices to be accurate. Comprehensive new evidence from meta-analyses clearly shows that many BP monitoring devices (including oscillometric machines and "gold standard" mercury auscultation) do not accurately represent the BP within the arteries at the upper arm (brachial) or central aorta. Particular variability in the accuracy of BP devices compared with intra-arterial BP has been demonstrated in the cuff BP range from prehypertension to grade I hypertension (systolic BP 120-159 to diastolic BP 80-99 mmHg). This is within the BP range that is most common among people worldwide and, thus almost certainly, feeding confusion around optimal hypertension guideline thresholds. At the individual level, inaccurate BP devices have major potential consequences for best practice patient management, where underestimation of true BP is a missed opportunity to lower cardiovascular risk (with therapeutics or lifestyle) and overestimation of true BP could lead to overmedication. Each problem leads to increased cost from preventable cardiovascular events and unnecessary medications. Altogether, there is a critical need to improve the accuracy standards of BP monitoring devices. In the meantime, out-of-office BP (24 h of ambulatory BP and/or home BP monitoring) or automated, unobserved in-office BP monitoring that takes the average of multiple readings using validated devices are the best available options to determine BP control.

Sources of inaccuracy in the measurement of adult patients' resting blood pressure in clinical settings: a systematic review

BACKGROUND

To interpret blood pressure (BP) data appropriately, healthcare providers need to be knowledgeable of the factors that can potentially impact the accuracy of BP measurement and contribute to variability between measurements.

METHODS

A systematic review of studies quantifying BP measurement inaccuracy. Medline and CINAHL databases were searched for empirical articles and systematic reviews published up to June 2015. Empirical articles were included if they reported a study that was relevant to the measurement of adult patients' resting BP at the upper arm in a clinical setting (e.g. ward or office); identified a specific source of inaccuracy; and quantified its effect. Reference lists and reviews were searched for additional articles.

RESULTS

A total of 328 empirical studies were included. They investigated 29 potential sources of inaccuracy, categorized as relating to the patient, device, procedure or observer. Significant directional effects were found for 27; however, for some, the effects were inconsistent in direction. Compared with true resting BP, significant effects of individual sources ranged from -23.6 to +33 mmHg SBP and -14 to +23 mmHg DBP.

CONCLUSION

A single BP value outside the expected range should be interpreted with caution and not taken as a definitive indicator of clinical deterioration. Where a measurement is abnormally high or low, further measurements should be taken and averaged. Wherever possible, BP values should be recorded graphically within ranges. This may reduce the impact of sources of inaccuracy and reduce the scope for misinterpretations based on small, likely erroneous or misleading, changes.

Accuracy in Blood Pressure Monitoring: The Effect of Noninvasive Blood Pressure Cuff Inflation on Intra-arterial Blood Pressure Values

CONTEXT

Both invasive and noninvasive blood pressure (invasive arterial blood pressure [IABP] and noninvasive BP [NIBP]) monitors are used perioperatively; however, they often produce different values. The reason for this discrepancy is not clear, and it is possible that the act of cuff inflation itself might affect the IABP values, especially with the recurrent cycling of NIBP cuff.

AIM

The aim of this study was to determine the effect of ipsilateral NIBP cuff inflation on the contralateral IABP values.

SETTINGS AND DESIGNS

Prospective, observational study.

MATERIALS AND METHODS

One hundred consecutive patients were studied. The NIBP device was set to cycle every 5 min for a total of 6 times. During each cuff inflation cycle, changes in IABP values from the arterial line in the contralateral arm were recorded. A total of 582 measurements were included for data analysis.

STATISTICAL ANALYSIS

Chi-square, paired t-test, analysis of variance.

RESULTS

Mean (± standard deviation) changes in systolic BP (SBP), diastolic BP, and mean BP with cuff inflation were 6.7 ± 5.9, 2.6 ± 4.0, and 4.0 ± 3.9 mmHg, respectively. We observed an increase of 0-10 mmHg in SBP in majority (73.4%) of cuff inflations. The changes in IABP did not differ between the patients with or without hypertension or with the baseline SBP.

CONCLUSIONS

This study showed that there is a transient reactive rise in IABP values with NIBP cuff inflation. This is important information in the perioperative and intensive care settings, where both these measurement techniques are routinely used. The exact mechanism for this effect is not known but may be attributed to the pain and discomfort from cuff inflation.

Importance of Calibration Method in Central Blood Pressure for Cardiac Structural Abnormalities

BACKGROUND

Central blood pressure (CBP) independently predicts cardiovascular risk, but calibration methods may affect accuracy of central systolic blood pressure (CSBP). Standard central systolic blood pressure (Stan-CSBP) from peripheral waveforms is usually derived with calibration using brachial SBP and diastolic BP (DBP). However, calibration using oscillometric mean arterial pressure (MAP) and DBP (MAP-CSBP) is purported to provide more accurate representation of true invasive CSBP. This study sought to determine which derived CSBP could more accurately discriminate cardiac structural abnormalities.

METHODS

A total of 349 community-based patients with risk factors (71±5years, 161 males) had CSBP measured by brachial oscillometry (Mobil-O-Graph, IEM GmbH, Stolberg, Germany) using 2 calibration methods: MAP-CSBP and Stan-CSBP. Left ventricular hypertrophy (LVH) and left atrial dilatation (LAD) were measured based on standard guidelines.

RESULTS

MAP-CSBP was higher than Stan-CSBP (149±20 vs. 128±15mm Hg, P < 0.0001). Although they were modestly correlated (rho = 0.74, P < 0.001), the Bland-Altman plot demonstrated a large bias (21mm Hg) and limits of agreement (24mm Hg). In receiver operating characteristic (ROC) curve analyses, MAP-CSBP significantly better discriminated LVH compared with Stan-CSBP (area under the curve (AUC) 0.66 vs. 0.59, P = 0.0063) and brachial SBP (0.62, P = 0.027). Continuous net reclassification improvement (NRI) (P < 0.001) and integrated discrimination improvement (IDI) (P < 0.001) corroborated superior discrimination of LVH by MAP-CSBP. Similarly, MAP-CSBP better distinguished LAD than Stan-CSBP (AUC 0.63 vs. 0.56, P = 0.005) and conventional brachial SBP (0.58, P = 0.006), whereas Stan-CSBP provided no better discrimination than conventional brachial BP (P = 0.09).

CONCLUSIONS

CSBP is calibration dependent and when oscillometric MAP and DBP are used, the derived CSBP is a better discriminator for cardiac structural abnormalities.

The accuracy of blood pressure measured by arterial line and non-invasive cuff in critically ill children

BACKGROUND

The accuracy of arterial lines (AL) using the flush test or stopcock test has not been described in children, nor has the difference between invasive arterial blood pressure (IABP) versus non-invasive cuff (NIBP) blood pressure.

METHODS

After ethics approval and consent, we performed the flush test and stopcock test on AL (to determine over damping, under damping, and optimal damping), and determined the difference (NIBP-IABP) in systolic, diastolic, and mean blood pressure (ΔSBP, ΔDBP, and ΔMAP). The primary outcome was incidence (95 % CI) of optimally damped AL. Predictors of ΔBP (effect size (95 % CI)) were determined using multiple linear regression.

RESULTS

There were 147 AL tests in 100 enrolled patients with mean age 44.7 (SD 56) months, weight 16.8 (SD 18.3) kg, male 59 %, postoperative-cardiovascular 52 %, peripheral-AL 78 %, inotropes 29 %, vasodilators 15 %, and ventilated 73 %. The flush test performed in 66 patients (45 %) showed optimal damping in 30 (46 %; 95 % CI 34, 57 %), over damping in 25 (38 %) and under damping in 11 patients (17 %). The stopcock test was over-damped in 128/146 patients (88 %), with the same damping as the flush test in 24/64 (38 %). In optimally damped (flush test) AL, ΔSBP, ΔDBP, and ΔMAP were 0.8 (SD 12.2), -5.2 (SD 8.7), and -4.9 (7.6) respectively. A second set of AL tests was done 2 h later on the same day in 62 patients; AL damping often changed (10/28 flush tests) and ΔBPs correlated poorly (r = 0.31-0.55). Predictors (effect size) of ΔDBP were vasodilator infusion (15.6 (2.9 to 28.3); p = 0.016) and optimal damping (-7.2 (-12.2 to 2.2); p = 0.005); and of ΔMAP were vasodilator infusion (10.0 (-0.3 to 20.4); p = 0.057) and optimal damping (-4.0 (-8 to 0.1); p = 0.058). There were no independent predictors of damping category (n = 66 flush tests).

CONCLUSIONS

Optimally damped AL occur in half of critically ill children, and this is not predictable. There is much variability in ∆BP between NIBP and the gold standard IABP, and this varies even in the same patient on the same day, and is not easily predictable. In critically ill children, NIBP may not be accurate enough to guide management, and more attention to ensuring the AL is optimally damped is needed.

Assessment of systolic aortic pressure and its association to all cause mortality critically depends on waveform calibration

BACKGROUND

The aim of this study is the prospective investigation of the association of brachial SBP (bSBP) and aortic SBP (aSBP) to all-cause mortality, with special emphasis on different calibration methods for central pressure estimates, in particular, brachial systolic and diastolic, as well as brachial mean and diastolic pressures.

METHOD

One hundred and fifty-nine patients were enrolled in a longitudinal, prospective study of arterial stiffness and cardiovascular risk in a chronic kidney disease stages 2-4 cohort. Office measurements of bSBP and aSBP were assessed by a validated oscillometric device. Prognostic factors of survival were identified by use of Cox proportional-hazards regression models.

RESULTS

After a mean follow-up duration of 42 months (range 30-50 months), 13 patients died. In univariate Cox analysis, bSBP and aSBP calibrated using bSBP and bDBP did not significantly predict mortality, only aSBP assessed using measured mean and diastolic pressure calibration was significantly associated with mortality (hazard ratio 1.027, P = 0.008). This remained significant in multivariate analysis after adjustment for age, sex, and anthropometric measures. More important, adding bSBP to the multivariate model (hazard ratio 0.91, P = 0.003) lead to a significantly increased prognostic power of aortic systolic pressure (hazard ratio 1.097, P < 0.001) and indicated that differences between bSBP and aSBP are of potential interest.

CONCLUSION

Within our cohort, only aSBP assessed with measured mean and diastolic pressure independently predicted mortality and provided additional prognostic value on top of bSBP readings. Therefore, the method of calibration plays an important role for predictive power of aSBP.

Detecting central-venous oxygen desaturation without a central-venous catheter: Utility of the difference between invasively and noninvasively measured blood pressure

OBJECTIVE

The objective was to determine whether central-venous oxygen saturation (ScvO2<70%) can be detected from the difference between invasively and noninvasively measured systolic blood pressure (BP) (ie, ΔBP defined as arterial BP minus noninvasive BP).

METHODS

This is a cross-sectional study at a single medical and surgical intensive care unit in Japan. All hypotensive patients admitted to intensive care unit were eligible. Arterial BP was measured via a radial-artery catheter, and noninvasive BP on the same side was measured via a brachial cuff. ScvO2 was measured by gas analysis of blood sampled from a central-venous chatheter (CVC). We calculate the area under the curve for ΔBP as an indicator of ScvO2<70%.

RESULTS

Usable data were obtained from the records of 111 patients. The median and interquartile range of ΔBP and ScvO2 were -4mm Hg (-11, 6) and 67% (60.9, 73.9), respectively. The area under the curve of ΔBP as an indicator of ScvO2<70% was 0.81 (95% confidence interval [CI], 0.73-0.89). With a cutoff ΔBP of 0, sensitivity was 65.7% (95% CI, 53.1-76.8), specificity was 97.7% (95% CI, 88.0-99.8), and positive predictive value was 97.8 (95% CI, 88.2-99.9).

CONCLUSIONS

ΔBP can indicate whether ScvO2 is lower than 70%. When that difference is greater than 0, ScvO2 is very likely to be lower than 70%.

A survey of blood pressure parameters after aneurysmal subarachnoid hemorrhage

Purpose/aim: Blood pressure (BP) regulation is recommended following aneurysmal subarachnoid hemorrhage (aSAH) to prevent re-bleeding and to treat delayed cerebral ischemia. However, optimal BP thresholds are not well established. There is also variation with regard to the BP component (e.g. systolic vs. mean) that is targeted or manipulated.

MATERIALS AND METHODS

An 18-question survey was distributed to physicians and advanced practitioner members of the Neurocritical Care Society. Respondents were asked which BP parameter they manipulated and what their thresholds were in different clinical scenarios. They were also asked whether they were influenced by the presence of incidental aneurysms. Answers were analyzed for differences in training background and treatment setting.

RESULTS

There were 128 responses. The majority were neurointensivists (47 neurology and 37 non-neurology) and treated patients in dedicated neurointensive care units (n = 98). Systolic BP (SBP) was preferred over mean arterial pressure (MAP). Prior to aneurysm treatment, SBP limits ranged from 140 to 180 mm Hg. After aneurysm treatment, SBP limits ranged from 160 to 240 mm Hg. The maximum and minimum MAPs varied by as much as 50%. Nearly two-thirds of the respondents were influenced by the presence of incidental aneurysms. Training background influenced tolerance to BP limits with neurology-trained neurointensivists accepting higher BP limits when treating delayed ischemia ( p = .018). They were also more likely to follow SBP ( p = .018) and have a limit of 140 mm Hg prior to aneurysm treatment ( p = .001).

CONCLUSIONS

There is large practice variability in BP management following aSAH. There is also uncertainty over the importance of incidental aneurysms. Further research could evaluate whether this variability has clinical significance.

Blood Pressure Management Controversies in Neurocritical Care

Blood pressure (BP) management is essential in neurocritical care settings to ensure adequate cerebral perfusion and prevent secondary brain injury. Despite consensus on the importance of BP monitoring, significant practice variations persist regarding optimal methods for monitoring and treatment of BP values among patients with neurologic injuries. This article provides a summary of research investigating various approaches for BP management in neurocritical care. Evidence-based recommendations, areas for future research, and current technological advancements for BP management are discussed.

Comparison of a continuous noninvasive arterial pressure device with invasive measurements in cardiovascular postsurgical intensive care patients: a prospective observational study

BACKGROUND

Arterial pressure monitoring using the a continuous noninvasive arterial pressure (CNAP) device during general anaesthesia is known to be interchangeable with continuous invasive arterial pressure (CIAP) monitoring. Agreement with invasive measurements in cardiovascular postsurgical intensive care patients has not been assessed.

OBJECTIVE

The objective of this study is to assess the agreement and interchangeability of CNAP with CIAP in cardiovascular postsurgical patients and to determine the effects of cardiac arrhythmia, catecholamine dosage, respiratory weaning and calibration intervals on agreement.

DESIGN

A prospective observational study.

SETTING

German university hospital cardiovascular ICU. Data were collected from April 2010 to December 2011.

PATIENTS

From 110 enrolled patients, 104 were included. Inclusion criteria were American Society of Anaesthesiologists (ASA) physical status III or IV patients undergoing controlled ventilation. Exclusion criteria included emergencies, complete heart block and marked arterial pressure differences greater than 10 mmHg in the two arms.

MAIN OUTCOME MEASURES

Bland-Altman plots, bias, precision, 95% limits of agreement, percentage error and agreement : tolerability indexes (ATIs) were estimated to determine clinical agreement.

RESULTS

From 11 222 arterial pressure readings, biases (SD) for CIAP-CNAP for systolic arterial pressure (SAP), diastolic arterial pressure (DAP) and mean arterial pressure (MAP) for all patients were 4.3 (11.6), -9.4 (8) and -6 (7.6) mmHg, respectively. Cardiac arrhythmia (4.1 (13.1), -14.4 (8.3), -9.5 (8.9) mmHg) and long interval to last calibration [4.5 (15), -9.8 (9.5), -6.4 (9.1) mmHg] impaired the accuracy of CNAP with failed interchangeability criteria defined by the percentage error. In contrast, use of catecholamines (epinephrine or norepinephrine infusions >0.1 μg kg min), short calibration intervals and weaning conditions did not affect accuracy, interchangeability and agreement, especially of MAP. Agreement was defined as acceptable for MAP for all data and subgroups (ATI 0.8 to 1.0) and at worst, marginal for SAP and DAP (ATI 0.9 to 1.6).

CONCLUSION

CNAP showed acceptable agreement defined by the ATI with invasive measurements for MAP and partially for DAP, but there was considerable variability for SAP. MAP should be preferred for clinical decision making. Cardiac arrhythmia, in contrast to catecholamine dosage or weaning procedures, impaired the accuracy, agreement and interchangeability of CNAP.

TRIAL REGISTRATION

Clinical trials.gov identifier NCT01003665.

Accuracy of invasive arterial pressure monitoring in cardiovascular patients: an observational study

INTRODUCTION

Critically ill patients and patients undergoing high-risk and major surgery, are instrumented with intra-arterial catheters and invasive blood pressure is considered the "gold standard" for arterial pressure monitoring. Nonetheless, artifacts due to inappropriate dynamic response of the fluid-filled monitoring systems may lead to clinically relevant differences between actual and displayed pressure values. We sought to analyze the incidence and causes of resonance/underdamping phenomena in patients undergoing major vascular and cardiac surgery.

METHODS

Arterial pressures were measured invasively and, according to the fast-flush Gardner's test, each patient was attributed to one of two groups depending on the presence (R-group) or absence (NR-group) of resonance/underdamping. Invasive pressure values were then compared with the non-invasive ones.

RESULTS

A total of 11,610 pulses and 1,200 non-invasive blood pressure measurements were analyzed in 300 patients. Ninety-two out of 300 (30.7%) underdamping/resonance arterial signals were found. In these cases (R-group) systolic invasive blood pressure (IBP) average overestimation of non-invasive blood pressure (NIBP) was 28.5 (15.9) mmHg (P <0.0001) while in the NR-group the overestimation was 4.1(5.3) mmHg (P < 0.0001). The mean IBP-NIBP difference in diastolic pressure in the R-group was -2.2 (10.6) mmHg and, in the NR-group -1.1 (5.8) mmHg. The mean arterial pressure difference was 7.4 (11.2) mmHg in the R-group and 2.3 (6.4) mmHg in the NR-group. A multivariate logistic regression identified five parameters independently associated with underdamping/resonance: polydistrectual arteriopathy (P = 0.0023; OR = 2.82), history of arterial hypertension (P = 0.0214; OR = 2.09), chronic obstructive pulmonary disease (P = 0.198; OR = 2.61), arterial catheter diameter (20 vs. 18 gauge) (P < 0.0001; OR = 0.35) and sedation (P = 0.0131; OR = 0.5). The ROC curve for the maximal pressure-time ratio, showed an optimum selected cut-off point of 1.67 mmHg/msec with a specificity of 97% (95% CI: 95.13 to 99.47%) and a sensitivity of 77% (95% CI: 67.25 to 85.28%) and an area under the ROC curve by extended trapezoidal rule of 0.88.

CONCLUSION

Physicians should be aware of the possibility that IBP can be inaccurate in a consistent number of patients due to underdamping/resonance phenomena. NIBP measurement may help to confirm/exclude the presence of this artifact avoiding inappropriate treatments.

Variation of arterial and central venous catheter use in United States intensive care units

BACKGROUND

Arterial catheters (ACs) and central venous catheters (CVCs) are common in intensive care units (ICUs). Few data describe which patients receive these devices and whether variability in practice exists.

METHODS

The authors conducted an observational cohort study on adult patients admitted to ICU during 2001-2008 by using Project IMPACT to determine whether AC and CVC use is consistent across U.S. ICUs. The authors examined trends over time and patients more (mechanically ventilated or on vasopressors) or less (predicted risk of hospital mortality ≤2%) likely to receive either catheter.

RESULTS

Our cohort included 334,123 patients across 122 hospitals and 168 ICUs. Unadjusted AC usage rates remained constant (36.9% [2001] vs. 36.4% [2008]; P = 0.212), whereas CVC use increased (from 33.4% [2001] to 43.8% [2008]; P < 0.001 comparing 2001 and 2008); adjusted AC usage rates were constant from 2004 (35.2%) to 2008 (36.4%; P = 0.43 for trend). Surgical ICUs used both catheters most often (unadjusted rates, ACs: 56.0% of patients vs. 22.4% in medical and 32.6% in combined units, P < 0.001; CVCs: 46.9% vs. 32.5% and 36.4%, P < 0.001). There was a wide variability in AC use across ICUs in patients receiving mechanical ventilation (median [interquartile range], 49.2% [29.9-72.3%]; adjusted median odds ratio [AMOR], 2.56), vasopressors (51.7% [30.8-76.2%]; AMOR, 2.64), and with predicted mortality of 2% or less (31.7% [19.5-49.3%]; AMOR, 1.94). There was less variability in CVC use (mechanical ventilation: 63.4% [54.9-72.9%], AMOR, 1.69; vasopressors: 71.4% (59.5-85.7%), AMOR, 1.93; predicted mortality of 2% or less: 18.7% (11.9-27.3%), AMOR, 1.90).

CONCLUSIONS

Both ACs and CVCs are common in ICU patients. There is more variation in use of ACs than CVCs.

Noninvasive techniques for blood pressure measurement are not a reliable alternative to direct measurement: a randomized crossover trial in ICU

INTRODUCTION

Noninvasive blood pressure (NIBP) monitoring methods are widely used in critically ill patients despite poor evidence of their accuracy. The erroneous interpretations of blood pressure (BP) may lead to clinical errors.

OBJECTIVES

To test the accuracy and reliability of aneroid (ABP) and oscillometric (OBP) devices compared to the invasive BP (IBP) monitoring in an ICU population.

MATERIALS AND METHODS

Fifty adult patients (200 comparisons) were included in a randomized crossover trial. BP was recorded simultaneously by IBP and either by ABP or by OBP, taking IBP as gold standard.

RESULTS

Compared with ABP, IBP systolic values were significantly higher (mean difference ± standard deviation 9.74 ± 13.8; P < 0.0001). Both diastolic (-5.13 ± 7.1; P < 0.0001) and mean (-2.14 ± 7.1; P=0.0033) IBP were instead lower. Compared with OBP, systolic (10.80 ± 14.9; P < 0.0001) and mean (5.36 ± 7.1; P < 0.0001) IBP were higher, while diastolic IBP (-3.62 ± 6.0; P < 0.0001) was lower. Bland-Altman plots showed wide limits of agreement in both NIBP-IBP comparisons.

CONCLUSIONS

BP measurements with different devices produced significantly different results. Since in critically ill patients the importance of BP readings is often crucial, noninvasive techniques cannot be regarded as reliable alternatives to direct measurements.

Methods of blood pressure measurement in the ICU

OBJECTIVE

Minimal clinical research has investigated the significance of different blood pressure monitoring techniques in the ICU and whether systolic vs. mean blood pressures should be targeted in therapeutic protocols and in defining clinical study cohorts. The objectives of this study are to compare real-world invasive arterial blood pressure with noninvasive blood pressure, and to determine if differences between the two techniques have clinical implications.

DESIGN

We conducted a retrospective study comparing invasive arterial blood pressure and noninvasive blood pressure measurements using a large ICU database. We performed pairwise comparison between concurrent measures of invasive arterial blood pressure and noninvasive blood pressure. We studied the association of systolic and mean invasive arterial blood pressure and noninvasive blood pressure with acute kidney injury, and with ICU mortality.

SETTING

Adult intensive care units at a tertiary care hospital.

PATIENTS

Adult patients admitted to intensive care units between 2001 and 2007.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Pairwise analysis of 27,022 simultaneously measured invasive arterial blood pressure/noninvasive blood pressure pairs indicated that noninvasive blood pressure overestimated systolic invasive arterial blood pressure during hypotension. Analysis of acute kidney injury and ICU mortality involved 1,633 and 4,957 patients, respectively. Our results indicated that hypotensive systolic noninvasive blood pressure readings were associated with a higher acute kidney injury prevalence (p = 0.008) and ICU mortality (p < 0.001) than systolic invasive arterial blood pressure in the same range (≤70 mm Hg). Noninvasive blood pressure and invasive arterial blood pressure mean arterial pressures showed better agreement; acute kidney injury prevalence (p = 0.28) and ICU mortality (p = 0.76) associated with hypotensive mean arterial pressure readings (≤60 mm Hg) were independent of measurement technique.

CONCLUSIONS

Clinically significant discrepancies exist between invasive and noninvasive systolic blood pressure measurements during hypotension. Mean blood pressure from both techniques may be interpreted in a consistent manner in assessing patients' prognosis. Our results suggest that mean rather than systolic blood pressure is the preferred metric in the ICU to guide therapy.

Increasing sleep duration to lower beat-to-beat blood pressure: a pilot study

Strong evidence has accumulated over the last several years, showing that low sleep quantity and/or quality plays an important role in the elevation of blood pressure. We hypothesized that increasing sleep duration serves as an effective behavioral strategy to reduce blood pressure in prehypertension or type 1 hypertension. Twenty-two participants with prehypertension or stage 1 hypertension, and habitual sleep durations of 7 h or less, participated in a 6-week intervention study. Subjects were randomized to a sleep extension group (48 ± 12 years, N = 13) aiming to increase bedtime by 1 h daily over a 6-week intervention period, or to a sleep maintenance group (47 ± 12 years, N = 9) aiming to maintain habitual bedtimes. Both groups received sleep hygiene instructions. Beat-to-beat blood pressure was monitored over 24 h, and 24-h urine and a fasting blood sample were collected pre- and post-intervention. Subjects in the sleep extension group increased their actigraphy-assessed daily sleep duration by 35 ± 9 min, while subjects in the sleep maintenance condition increased slightly by 4 ± 9 min (P = 0.03 for group effect). Systolic and diastolic beat-to-beat blood pressure averaged across the 24-h recording period significantly decreased from pre- to post-intervention visit in the sleep extension group by 14 ± 3 and 8 ± 3 mmHg, respectively (P < 0.05). Though the reduction of 7 ± 5 and 3 ± 4 mmHg in the sleep maintenance group was not significant, it did not differ from the blood pressure reduction in the sleep extension group (P = 0.15 for interaction effect). These changes were not paralleled by pre- to post-intervention changes in inflammatory or sympatho-adrenal markers, nor by changes in caloric intake. While these preliminary findings have to be interpreted with caution due to the small sample size, they encourage future investigations to test whether behavioral interventions designed to increase sleep duration serve as an effective strategy in the treatment of hypertension.

Comparison of non-invasive and invasive blood pressure in aeromedical care

Blood pressure measurement is an essential physiological measurement for all critically ill patients. Previous work has shown that non-invasive blood pressure is not an accurate reflection of invasive blood pressure measurement. In a transport environment, the effects of motion and vibration may make non-invasive blood pressure less accurate. Consecutive critically ill patients transported by a dedicated aeromedical retrieval and critical care transfer service with simultaneous invasive and non-invasive blood pressure measurements were analysed. Two sets of measurements were recorded, first in a hospital environment before departure (pre-flight) and a second during aeromedical transport (in-flight). A total of 56 complete sets of data were analysed. Bland-Altman plots showed limits of agreement (precision) for pre-flight systolic blood pressure were -37.3 mmHg to 30.0 mmHg, and for pre-flight mean arterial pressure -20.5 mmHg to 25.0 mmHg. The limits of agreement for in-flight systolic blood pressure were -40.6 mmHg to 33.1 mmHg, while those for in-flight mean blood pressure in-flight were -23.6 mmHg to 24.6 mmHg. The bias for the four conditions ranged from 0.5 to -3.8 mmHg. There were no significant differences in values between pre-flight and in-flight blood pressure measurements for all categories of blood pressure measurement. Thus, our data show that non-invasive blood pressure is not a precise reflection of invasive intra-arterial blood pressure. Mean blood pressure measured non-invasively may be a better marker of invasive blood pressure than systolic blood pressure. Our data show no evidence of non-invasive blood pressures being less accurate in an aeromedical transport environment.

Measurement Accuracy of Non-invasively Obtained Central Blood Pressure: A Systematic Review and Meta-analysis

BACKGROUND

Blood pressures determined at different sites vary considerably. Non-invasive methods are available to estimate central aortic blood pressure, the blood pressure at the origin of all arterial pulses. These methods obtain estimated central blood pressure by calibration and/or mathematical calculations for peripheral pulse waveforms. However, the accuracy of these methods has not been systematically examined.

OBJECTIVES

The review aimed to synthesise the best evidence on the accuracy of non-invasive measurement methods for central blood pressure.

INCLUSION CRITERIA

Types of participantsStudies with adult patients receiving invasive and non-invasive measurements of central blood pressure were considered.

PHENOMENA OF INTEREST

Studies were considered for inclusion if the focus was accuracy of non-invasive central BP estimating methods compared to invasively obtained corresponding values.

TYPES OF STUDIES

Studies examining agreement between measurements using non-invasive central blood pressure estimating methods compared to invasive corresponding values were considered.

TYPES OF OUTCOMES

This review included the means and standard deviation of differences between estimated and invasively measured central blood pressure.

SEARCH STRATEGY

The search sought to identify any relevant published or unpublished studies with a three-step search strategy.

METHODOLOGICAL QUALITY

Two independent reviewers assessed methodological quality of studies by a critical appraisal tool modified from Cochrane Diagnostic Test Accuracy Working Group.

DATA COLLECTION

We used an original form to extract from included studies all study characteristics possibly related to agreement.

DATA SYNTHESIS

Inverse variance weighted approach and DerSimonian-Laird weights for the random effects model, which incorporates a between-study variance, were used to obtain pooled estimates of systematic and random error from individual study estimates of the mean and standard deviation of differences between the paired measurements. Heterogeneity was assessed using Cochran Q. All analyses were performed in Microsoft Excel 2003.

RESULTS

Twenty eight studies were eligible for inclusion and critically appraised in this review. Appropriate data for agreement were extracted from papers or authors in 20 studies, which were further included in meta-analysis. Acquired peripheral waveforms in these studies were directly measured, calibrated to match invasively obtained aortic mean blood pressure and diastolic blood pressure, or calibrated using brachial blood pressure measured by sphygomomanometer, the cuff blood pressure. Estimated central blood pressure of the studies using the last totally non-invasively methods (real world practices) were subject to meta-analysis separately from studies with the former two invasive methods (theoretical practice). Of the invasive methods, mean difference of the estimated central blood pressure was small (-1.2 ± 4.2mmHg for central systolic blood pressure, -0.6 ± 2.1mmHg for central diastolic blood pressure, and -1.1 ± 5.3 mmHg for central pulse pressure). However, the errors of the non-invasive method inflated considerably (-8.1 ± 10.7mmHg for central systolic blood pressure, 8.8 ± 9.5mmHg for central diastolic blood pressure, and -11.8 ± 13.3 mmHg for central pulse pressure). The findings were similar in subgroup analysis by different central blood pressure methods and by validated cuff monitors.

CONCLUSIONS

Current central blood pressure estimating methods are acceptable in theory with small systematic and random error. However, the error of these methods was evident when cuff blood pressure was used for calibration and probably made them clinically inapplicable.

Results of a survey of blood pressure monitoring by intensivists in critically ill patients: a preliminary study

OBJECTIVES

Maintenance of mean arterial pressure>65 mm Hg has been associated with improved clinical outcomes in many studies of critically ill patients. Current guidelines for the management of septic shock and guidelines for managing other critical illnesses suggest intra-arterial blood pressure measurement is preferred over automated oscillometric noninvasive blood pressure measurement. Despite these recommendations, anecdotal experience suggested that the use of noninvasive blood pressure measurement in our institution and others in preference to intra-arterial blood pressure measurement remained prevalent.

DESIGN

We designed an online survey and sent it by e-mail.

SETTING

Intensive care units.

PATIENTS AND SUBJECTS

A randomly selected group from the membership of the Society for Critical Care Medicine.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Use of non-invasive and invasive blood pressure devices. Eight hundred eighty individuals received an invitation to complete the survey and 149 responded. We found that 71% (105 of 149) of intensivists estimated the correct cuff size rather than measuring arm circumference directly. In hypotensive patients, 73% of respondents (108 of 149) reported using noninvasive blood pressure measurement measurements for patient management. In patients on a vasopressor medication, 47% (70 of 149) of respondents reported using noninvasive blood pressure measurement for management.

CONCLUSIONS

The use of noninvasive blood pressure measurement measurements in critically ill patients is common despite the paucity of evidence validating its accuracy in critically ill patients. Given this widespread use, accuracy and precision validation studies comparing noninvasive blood pressure measurement with intra-arterial blood pressure measurement in critically ill patients should be performed.

A poor correlation exists between oscillometric and radial arterial blood pressure as measured by the Philips MP90 monitor

In anesthesia and critical care, invasive arterial blood pressure monitoring is the gold standard against which other methods of monitoring are compared. In this assessment of the Philips MP90 monitor, the objective was to determine whether or not oscillometric measurements were within the accuracy standards set by the Association for the Advancement of Medical Instrumentation (AAMI) and the British Hypertension Society (BHS). Three hundred and one invasive and noninvasive paired measurements were obtained from eleven adult patients on the neurosurgical service at Stanford University Medical Center. Bland-Altman plots were created to assess agreement between the two measurement systems. Paired correlation analysis, bias and precision calculations were performed. Oscillometric blood pressure measurements correlated with arterial measurements yielding Pearson r values of 0.68, 0.67 and 0.62 for systolic, diastolic and mean pressures, respectively (P < 0.01.) Mean differences with 95% confidence intervals were -3.8 mmHg +/- 13.6, -2.4 mmHg +/- 10.0, and 4.0 mmHg +/- 13.1 for systolic, diastolic and mean pressures, respectively. The mean difference for these measurements was <or=5 mmHg as stipulated by the AAMI guidelines, but the standard deviation was greater than the 8 mmHg allowed by the AAMI guidelines. When the BHS guidelines were applied, the device merited a grade "D" for systolic and mean arterial pressure, and a grade "C" for diastolic pressure, with the highest possible grade level being "A." There was a poor correlation between noninvasive and invasive measurements of arterial blood pressure as measured with a cuff and radial arterial cannula using the Philips MP90 monitor. These inaccuracies could lead to unnecessary interventions, or lack of appropriate interventions in anesthetic management. Further study is needed to specify the absolute inaccuracy of the monitor, and to determine if accuracy between the two methods varies with patient co-morbidities, surgical procedures, or anesthetic management.

Noninvasive assessment of arterial pressure

PURPOSE OF REVIEW

To briefly review recent advances in the noninvasive assessment of arterial pressure (indirect methods) in the field of critical care.

RECENT FINDINGS

Automated oscillometric measurements underestimate intraarterial systolic blood pressure. Digital photoplethysmography has led to conflicting results, although the obtained respiratory pulse pressure variation correlates with the fluid-challenge-induced changes in stroke volume. The pulse oximetry photoplethysmographic signal recorded at the digital or ear level may be useful in monitoring respiratory arterial pressure variations, although technical improvements and clarifications are needed. Arterial tonometry is increasingly used in the cardiovascular field to reconstruct central aortic pressure. A recent study has shown that radial artery tonometry is feasible in hemodynamically stable patients and that peripheral pulse pressure reflects the combined influences of arterial stiffness and stroke volume, especially in elderly patients. The limitations of this technique include the potential bias related to the use of a generalized transfer function and the difficulty in obtaining reliable recordings in hemodynamically unstable patients.

SUMMARY

Intraarterial blood pressure must be preferred over noninvasive blood pressure recordings when critical decisions are required. In hemodynamically stable patients, valuable information may be obtained by using noninvasive techniques, amongst which arterial tonometry seems especially promising.