Noninvasive Hemodynamic Monitoring System Research Articles

Non-Invasive Hemodynamic Monitoring System Integrating Spectrometry, Photoplethysmography, and Arterial Pressure Measurement Capabilities.

Minimally invasive and non-invasive hemodynamic monitoring technologies have recently gained more attention, driven by technological advances and the inherent risk of complications in invasive techniques. In this article, an experimental non-invasive system is presented that effectively combines the capabilities of spectrometry, photoplethysmography (PPG), and arterial pressure measurement. Both time- and wavelength-resolved optical signals from the fingertip are measured under external pressure, which gradually increased above the level of systolic blood pressure. The optical channels measured at 434-731 nm divided into three groups separated by a group of channels with wavelengths approximately between 590 and 630 nm. This group of channels, labeled transition band, is characterized by abrupt changes resulting from a decrease in the absorption coefficient of whole blood. External pressure levels of maximum pulsation showed that shorter wavelengths (<590 nm) probe superficial low-pressure blood vessels, whereas longer wavelengths (>630 nm) probe high-pressure arteries. The results on perfusion indices and DC component level changes showed clear differences between the optical channels, further highlighting the importance of wavelength selection in optical hemodynamic monitoring systems. Altogether, the results demonstrated that the integrated system presented has the potential to extract new hemodynamic information simultaneously from macrocirculation tomicrocirculation.

Choosing the Best Method for Hemodynamic Monitoring

Optimizing hemodynamics improves patient outcomes in critically ill patients. There are many types of hemodynamic monitoring. When choosing the monitoring type, factors include accuracy, invasiveness, the desired hemodynamic variables, and potential complications. For example, the Pulmonary Artery Catheter is invasive and can be associated with catheter-related complications. Still, the values it provides have been validated and may be more useful when treating patients with heart problems. New minimally invasive and noninvasive hemodynamic monitoring systems, such as the Flo Trac and the ClearSight, deliver functional hemodynamic values that can be used to evaluate the real-time response to fluid administration. Minimally invasive and noninvasive devices’ ease of use, availability, and relative lack of patient complications make them appealing. However, they may lack accuracy in some situations.

Blood circulation changes associated with switching to non-invasive ventilation in COVID-19 patients

Background. Various methods of respiratory support in combination with prone positioning have been used during the COVID-19 pandemic. The effects of combination of these two factors on hemodynamics are of interest for clinical practitioners.The aim: to evaluate the effect of prone positioning on hemodynamics in COVID-19 patients depending on the method of respiratory support.Materials and methods. The study included 17 patients of both sexes diagnosed with COVID-19-associated community-acquired polysegmental viral and bacterial pneumonia with progressive respiratory failure. The study consisted of two stages. During the first stage, the patients were receiving respiratory support with humidified oxygen (3–7 liters per minute). The second stage was initiated after switching to noninvasive ventilation (NIV). The measurements were performed using a technique of volumetric compression oscillometry on a non-invasive hemodynamic monitoring system KAP CGosm-Globus (Russia).Results. The study showed that prone positioning in patients with severe COVID-19 when switching from oxygen therapy to NIV resulted in a change in the diastolic blood pressure difference module from 2.5 (1.0; 8.2) to 8.0 (5.7; 14.0) (p = 0.016). Escalation of respiratory support led to the changes in the left ventricular outflow tract velocity difference module from 11.5 (9.5; 34.2) to 31.0 (15.7; 42.0) (p = 0.049).Conclusions. Patients with community-acquired polysegmental viral and bacterial pneumonia associated with COVID-19 demonstrated changes in diastolic blood pressure and left ventricular outflow tract velocity as a result of prone positioning following switching from oxygen therapy to NIV.

The role of noninvasive hemodynamic monitoring in the evaluation of acute and severe pesticide poisoning

Objective: To explore the method of noninvasive hemodynamic monitoring system (NICaS) in monitoring the hemodynamics of patients with acute pesticide poisoning, and to analyze the clinical guiding value of NICaS in hemodynamics of patients with severe pesticide poisoning. Methods: In August 2019, 200 patients with severe acute organophosphorus pesticide poisoning (AOPP) or moderate severe acute paraquat pesticide poisoning (APP) admitted to Harrison international peace hospital from January 2017 to August 2019 were randomly divided into NICaS group (n=68) , transpulmonary thermodilution method (n=67) and empirical treatment group (n=65) . The relationship between acute physiology and chronic health score (APACHE Ⅱ) , heart rate, hemodynamic indexes, survival rate and complications were analyzed. Results: There were no significant differences in age, sex ratio, body mass index, heart rate, systolic blood pressure, no treatment period and admission APACHE II score between NICaS group, Picco group and experience group (P>0.05) ; Compared with the experience group, the mortality of AOPP and app in NICaS group and Picco group were lower, and the differences were statistically significant (P<0.05) .The cardiac output (CO) had a significant correlation in the interval of 2.8-6.7 L·min(-1) (r=0.738, r(2)=0.545, P<0.01) , and peripheral vascular resistance index (SVRI) had a significant correlation in the interval of 410-1 950 d·s·cm(-5)·m(2) (r=0.792, r(2)=0.627, P<0.01) . Bland Altman analysis showed that CO and SVRI measured by Picco and NICaS had 97.01% and 95.52% consistency, respectively. Compared with the experience group, the average daily infusion volume and daily colloid infusion volume of NICaS group and Picco group were lower, the differences were statistically significant (P<0.05) . Conclusion: NICaS can effectively monitor the hemodynamic indexes of patients with acute pesticide poisoning.

Intraoperative systemic vascular resistance is associated with postoperative nausea and vomiting after laparoscopic hysterectomy.

BACKGROUNDThe incidence of postoperative nausea and vomiting (PONV) in patients undergoing laparoscopic hysterectomy is very high compared with other surgeries, even when many prophylactic measures have been taken. However, the pathogenesis of PONV is multifactorial. Female sex, a history of motion sickness or PONV, nonsmokers, and perioperative opioid use are the most closely related factors. Among the multiple risk factors, suboptimal gastrointestinal (GI) perfusion may be attributed to some cases of PONV, and increased systemic vascular resistance (SVR) may lead to GI ischemia. The hypothesis of this research was that SVR is related to PONV.AIMTo investigate the relationship between SVR and PONV in patients undergoing laparoscopic hysterectomy.METHODSA total of 228 patients who underwent elective laparoscopic hysterectomy were included in this prospective observational study. SVR was monitored using a noninvasive hemodynamic monitoring system. Four indices of SVR, the baseline, mean, area under the curve (AUC), and weighted AUC, were used for analysis. The incidence and severity of nausea and vomiting were evaluated while patients were awake and throughout the intervals from 0 to 2 h, 2 to 6 h, and 6 to 24 h starting upon arrival at the post-anesthesia care unit. The associations between various SVR indices and PONV were investigated by logistic regression. P < 0.05 was considered statistically significant.RESULTSThe incidence of PONV in the study was 56.14% (128/228), and PONV tended to appear within 6 h after surgery. Five variables were significant in univariate analyses, however, only SVR mean [odds ratio (OR) = 1.015, 95%CI: 1.005-1.109, P = 0.047] and duration of surgery (OR = 1.316, 95%CI: 1.003-2.030, P = 0.012) were associated with PONV after logistic regression analysis. Furthermore, patients with high SVR mean were more likely to suffer from PONV after laparoscopic hysterectomy. On average, patients who developed PONV needed more time to tolerate diet and demonstrated poorer sleep quality on the first night after surgery. CONCLUSIONIn this study, PONV was a common complication after laparoscopic hysterectomy. SVR was associated with PONV, and high SVR mean was associated with a significantly increased risk of PONV.

Clearsight Use for Hemodynamic Monitoring During the Third Trimester of Pregnancy: A Validation Study

(Int J Obstet Anesth. 2018;36:85–95) Monitoring cardiac output (CO) in pregnant patients has been suggested as a means to improve outcomes for mother and child as blood pressure and clinical signs may not be sufficient proxys for CO. Currently, the gold standard for CO measurement is the thermodilution technique via a pulmonary artery catheter or transthoracic echocardiography (TTE). This study aimed to evaluate the Clearsight, a noninvasive hemodynamic monitoring system that uses “volume clamp” technology to produce a continuous arterial BP wave, as a valid monitor of CO and stroke volume (SV) in parturients compared with TTE.

Anesthetic management for cesarean section in a patient receiving transplacental treatment of fetal tachyarrhythmia: a case report

BackgroundAlthough rare, long-lasting fetal tachyarrhythmia often leads to fetal heart failure and hydrops. Some mothers receive transplacental treatment of fetal tachyarrhythmia (TTFT), which can potentially worsen maternal hypotension and bradycardia. Moreover, the use of rescue cardiovascular agents intraoperatively can worsen fetal tachycardia. However, reports of the anesthetic management of patients receiving TTFT are rare.Case presentationA 31-year-old woman who was receiving digoxin and sotalol for TTFT underwent planned elective cesarean section. The fetus had hypoplastic left heart syndrome, hydrops, and tachycardia. We used combined spinal-epidural anesthesia with a reduced dose of local anesthetic. We also employed a non-invasive continuous hemodynamic monitoring system. The mother’s systolic blood pressure remained at ≥ 90% of the baseline value; intraoperative administration of rescue cardiovascular agents was not required.ConclusionsWe successfully anesthetized a woman for cesarean section, who was receiving TTFT for fetal tachyarrhythmia, using combined spinal-epidural anesthesia and non-invasive continuous hemodynamic monitoring.

Passive Leg Raise: Feasibility and Safety of the Maneuver in Patients With Undifferentiated Shock.

Passive leg raise (PLR), in combination with technologies capable of capturing stroke volume changes, has been widely adopted in the management of shock. However, dedicated evaluation of safety, feasibility, and receptiveness of patients and nursing staff to PLR maneuver is missing. A noninterventional, prospective trial recruited adult patients with onset of undifferentiated shock within 24 hours with persistent vasopressor requirements despite fluid resuscitation. A standardized PLR maneuver was used to compare two noninvasive hemodynamic monitoring systems, each without significant impact on the performance of the maneuver. Safety and efficacy of the PLR were evaluated via subjective and objective measures. Objective measures of patient comfort and tolerance were evaluated through changes in vital signs, sedation, and analgesia requirements. Nurses and awake patients completed surveys on their experience. Seventy-nine patients were enrolled. Testing was aborted in 2 cases for medical reasons (one patient developed rapid atrial fibrillation, second had profound desaturation). Of all, 5.4% of patients required additional vasopressor support after completion of the PLR maneuver due to persistent hypotension and 4.1% of patients required additional sedation. Among awake patients (N = 35), 6% reported pain and 29% reported discomfort. A total of 11% of nurses reported minor technical difficulties with the maneuver. Passive leg raise maneuver leads to a few serious but reversible complications in a selected population of hemodynamically unstable patients. Although it provides relevant diagnostic information, it may impact patient care. Treating physician should be aware of infrequent but possible complications and appreciate the impact of the maneuver on patients' comfort and nursing workload.

Prediction of fluid responsiveness in mechanically ventilated cardiac surgical patients: the performance of seven different functional hemodynamic parameters

BackgroundFunctional hemodynamic parameters such as stroke volume and pulse pressure variation (SVV and PPV) have been shown to be reliable predictors of fluid responsiveness in mechanically ventilated patients. Today, different minimally- and non-invasive hemodynamic monitoring systems measure functional hemodynamic parameters. Although some of these parameters are described by the same name, they differ in their measurement technique and thus may provide different results. We aimed to test the performance of seven functional hemodynamic parameters simultaneously in the same clinical setting.MethodsHemodynamic measurements were done in 30 cardiac surgery patients that were mechanically ventilated. Before and after a standardized intravenous fluid bolus, hemodynamics were measured by the following monitoring systems: PiCCOplus (SVVPiCCO, PPVPiCCO), LiDCOrapid (SVVLiDCO, PPVLiDCO), FloTrac (SVVFloTrac), Philips Intellivue (PPVPhilips) and Masimo pulse oximeter (pleth variability index, PVI). Prediction of fluid responsiveness was tested by calculation of receiver operating characteristic (ROC) curves including a gray zone approach and compared using Fisher’s Z-Test.ResultsFluid administration resulted in an increase in cardiac output, while all functional hemodynamic parameters decreased. A wide range of areas under the ROC-curve (AUC’s) was observed: AUC-SVVPiCCO = 0.91, AUC-PPVPiCCO = 0.88, AUC-SVVLiDCO = 0.78, AUC-PPVLiDCO = 0.89, AUC-SVVFloTrac = 0.87, AUC-PPVPhilips = 0.92 and AUC-PVI = 0.68. Optimal threshold values for prediction of fluid responsiveness ranged between 9.5 and 17.5%. Lowest threshold values were observed for SVVLiDCO, highest for PVI.ConclusionAll functional hemodynamic parameters tested except for PVI showed that their use allows a reliable identification of potential fluid responders. PVI however, may not be suitable after cardiac surgery to predict fluid responsiveness.Trial registrationNCT02571465, registered on October 7th, 2015 (retrospectively registered).

Effects of rhBNP after PCI on non-invasive hemodynamic in acute myocardial infarction patients with left heart failure.

To investigate the effects of exogenous recombinant human brain natriuretic peptide (rhBNP) after primary percutaneous coronary intervention (PCI) on non-invasive hemodynamic in acute myocardial infarction patients with left ventricular failure. A number of 96 acute myocardial infarction patients accompanied with heart failure after PCI hospitalized in the People's Hospital of Sanya during February 2012 to October 2015 were selected. They were randomly divided into the therapy group (n=50) and control group (n=46). On the basis of routine treatment, patients in the therapy group were treated with intravenous rhBNP (1.5μg/kg was intravenous injection with uniform speed of 3min, followed by continuous infusion 0.0075μg/kg·min for 72h), while the control group received conventional treatment. BioZ-2011 non-invasive hemodynamic real-time monitoring system was used to monitor the hemodynamic parameters changes and the leaves of plasma pro-BNP, serum creatinine, serum potassium, serum sodium and urine volume of each group before and after treating for 30min, 1h, 3h, 6h, 12h, 24h, 48h, 72h. Patients in the therapy group showed no effect on heart rate, while after 30min of intravenous injection of rhBNP, CO, CI, SV, and SI increased significantly and LVET and TFC reduced at the same time, which had certain effect on blood pressure (SBP/DBP). Compared with the control group, the therapy group showed a faster and more effective improvement on hemodynamics. Acute myocardial infarction patients complicated with left heart failure after primary PCI can significantly improve hemodynamics by treating with rhBNP.

Shuangshen Ningxin Capsule, a Traditional Chinese Medicinal Preparation, Alleviates Myocardial Ischemia through Autophagy Regulation.

Shuangshen Ningxin capsule (SSNX), a modern Chinese formula, has been used to treat cardiovascular diseases in Eastern Asia. Our study focuses on the autophagy regulation of SSNX against coronary artery injuries. Myocardial infarction model was established in Chinese miniswines (CMS) by coronary artery balloon injury. SSNX was administered to the CMS for 8 weeks with 4 mg/kg or 16 mg/kg. Myocardial cells were incubated with 20% SSNX medicated serum for 2 hours. Assays were performed to detect the effects of SSNX on (i) coronary artery diameter by angiography, (ii) hemodynamics by noninvasive hemodynamic monitoring system, (iii) plaque burden and plaque volume by intravenous ultrasound (iv) coronary artery histology by H&E staining, (v) autophagosome by transmission electron microscopy, (vi) lactate dehydrogenase (LDH) leakage, and (vii) Beclin-1 and LC3-I/II expressions by Western blot. The results showed that CMS treated with SSNX exhibited the correction for the disturbed cardiac hemodynamics, increase of coronary artery diameter, reduction of high plaque burden and plaque volume, and decrease of LDH. The inhibitory effect of SSNX on CMS autophagy was demonstrated by the reduction of autophagosome and the downregulation of beclin-1 and LC3-I/II. SSNX may protect coronary artery and increase the stability of plaque through the suppression of myocardial cellular autophagy, which suggests the potentially therapeutic effect of SSNX on ischemic cardiovascular disease.

Refractory acute decompensated heart failure: an observational study on a noninvasive hemodynamic monitoring system aimed at improving the therapeutic approach

Inotropic agents should only be administered in acute decompensated heart failure (ADHF) refractory to vasodilators at optimal doses because they are associated with adverse outcome. In this setting a noninvasive hemodynamic monitoring system (NHMS) could be useful for optimizing treatment. advanced chronic heart failure, ejection fraction 30% or less, admission for ADHF with systolic blood pressure 115 mmHg or less and inadequate response at 48 h of therapy. Patients were evaluated with a NHMS: with vascular systemic resistance (VSR) greater than 1500 dyne x s/cm we used vasodilators at increasing doses, with VSR less than 1500 and cardiac index (CI) less than 2.4 l/min per m inotropic agents were used. The study population consisted of 20 patients (mean age 67 + or - 12 years) with ejection fraction 20 + or - 7%. After 48 h of clinical-guided therapy, none of the patients achieved VSR 1500 or less, and 12 patients had a CI less than 2.4 l/min per m. After hemodynamic-guided therapeutic optimization there was a significant reduction of dyspnea at rest (7.7 + or - 1.25 versus 2.44 + or - 1.33 on the 10-point Likert scale, P < 0.001) and 'cold' presentation (12 patients before and 1 patient after, P = 0.0004). Daily urinary volume was higher (1217 + or - 369 versus 2260 + or - 797 ml, P = 0.001) without renal function deterioration (creatinine 1.56 + or - 0.52 versus 1.34 + or - 0.61 mg/dl, P = 0.012).The nitroprusside dosing was increased after NHMS (0.13 + or - 0.19 versus 0.4 + or - 0.310 microg/kg per min, P = 0.044), whereas doses of inotropic agents, diuretics and beta-blockers did not change significantly. In refractory ADHF a NHMS improves significantly symptoms and renal function, with a better use of vasodilators.

Evaluation of Invasive and Noninvasive Hemodynamic Monitoring in Trauma Patients

The aim of this study was to compare a recently developed and improved noninvasive hemodynamic monitoring system with the conventional invasive monitoring by pulmonary artery catheterization (PAC) in acute emergency trauma patients. In a large, university-run, inner city public hospital, we monitored 993 trauma patients noninvasively; 262 of these were simultaneously monitored with both noninvasive hemodynamic and invasive PAC monitoring. The noninvasive monitoring was begun shortly after admission to the emergency department and the invasive PAC monitoring was started in the operating room, or as soon as the patient arrived in the intensive care unit. Noninvasive monitoring included cardiac index (CI) by the IQ or Physio Flow bioimpedance device, together with mean arterial blood pressure, heart rate, pulse oximetry (SapO2), transcutaneous oxygen (PtcO2), and carbon dioxide (PtcCO2) tensions. We compared CI by simultaneous measurements with both invasive and noninvasive methods 907 times in 262 patients. The CI by thermodilution (CItd) correlated well with simultaneous measurements with the bioimpedance (CIbi), r2 = 0.915, r2 = 0.84, p < 0.001. The bias and precision of simultaneous measurements was -0.070 +/- 0.47 L/min/m2; agreement was considered satisfactory. In the initial resuscitation period of both monitoring systems, the CI, mean arterial blood pressure, SapO2, and tissue perfusion (reflected by invasive DO2 and VO2, and by noninvasive PtcO2/FiO2 ratio) were higher in survivors than in nonsurvivors, whereas heart rate values were higher in the nonsurvivors. We concluded that noninvasive hemodynamic monitoring provided a feasible, safe, inexpensive, accurate, continuous, on-line real-time graphic displays that are equivalent to the essential features of invasive pulmonary artery catheter monitoring.

Noninvasive Hemodynamic Monitoring for Combat Casualties

The aims of this study were to develop and to test a noninvasive hemodynamic monitoring system that could be applied to combat casualties to supplement conventional vital signs, to use an advanced information system to predict outcomes, and to evaluate the relative effectiveness of various therapies with instant feedback information during acute emergency conditions. In a university-run inner city public hospital, we evaluated 1,000 consecutively monitored trauma patients in the initial resuscitation period, beginning shortly after admission to the emergency department. In addition to conventional vital signs, we used noninvasive monitoring devices (cardiac index by bioimpedance with blood pressure and heart rate to measure cardiac function, arterial hemoglobin oxygen saturation by pulse oximetry to reflect changes in pulmonary function, and tissue oxygenation by transcutaneous oxygen tension indexed to fractional inspired oxygen concentration and carbon dioxide tension to evaluate tissue perfusion). The cardiac index, mean arterial pressure, pulse oximetry (arterial hemoglobin oxygen saturation), and transcutaneous oxygen tension/fractional inspired oxygen concentration were significantly higher in survivors, whereas the heart rate and carbon dioxide tension were higher in nonsurvivors. The calculated survival probability was a useful outcome predictor that also served as a measure of severity of illness. The rate of misclassification of survival probability was 13.5% in the series as a whole but only 6% for patients without severe head injuries and brain death. Application of noninvasive hemodynamic monitoring to acute emergency trauma patients in the emergency department is feasible, safe, and inexpensive and provides accurate hemodynamic patterns in continuous, on-line, real-time, graphical displays of the status of cardiac, pulmonary, and tissue perfusion functions. Combined with an information system, this approach provided an early outcome predictor and evaluated, with an objective individualized method, the relative efficacy of alternative therapies for specific patients.

Multicenter Study of Noninvasive Monitoring Systems as Alternatives to Invasive Monitoring of Acutely III Emergency Patients

Recent reports showed lack of effectiveness of pulmonary artery catheterization in critically ill medical patients and relatively late-stage surgical patients with organ failure. Since invasive monitoring requires critical care environments, the early hemodynamic patterns may have been missed. Ideally, early noninvasive hemodynamic monitoring systems, if reliable, could be used as the "front end" of invasive monitoring to supply more complete descriptions of circulatory pathophysiology. To evaluate the accuracy and reliability of noninvasive hemodynamic monitoring consisting of a new bioimpedance method for estimating cardiac output combined with arterial BP, pulse oximetry, and transcutaneous PO2 and PCO2; we compared this system of noninvasive monitoring with simultaneous invasive measurements to evaluate circulatory deficiencies in acutely ill patients shortly after hospital admission where invasive monitoring was not readily available. We also preliminarily explored early differences in temporal hemodynamic patterns of survivors and nonsurvivors. Prospective comparison of simultaneous invasive and noninvasive measurements of circulatory function with retrospective analysis of data in university-run county hospitals, university hospitals and affiliated teaching hospitals, and a community private hospital. We studied 680 patients, including 139 severely injured or hemorrhaging patients in the emergency department (ED), 129 medical (nontrauma) patients on admission to the ED, 274 high-risk surgical patients intraoperatively, and 138 patients recently admitted to the ICU. A new noninvasive impedance device provided cardiac output estimations under conditions in which invasive thermodilution measurements were not usually applied. There were 2,192 simultaneous bioimpedance and thermodilution cardiac index measurements; the correlation coefficient, r = 0.85, r2 = 0.73, p < 0.001. The precision and bias was -0.124+/-0.75 L/min/m2. Both invasive and noninvasive monitoring systems provide similar information and identified episodes of hypotension, low cardiac index, arterial hemoglobin desaturation, low transcutaneous O2, high transcutaneous CO2, and low oxygen consumption before and during initial resuscitation. The limitations of noninvasive systems were described. Noninvasive monitoring systems gave continuous displays of physiologic data that provided information allowing early recognition of low flow and poor tissue perfusion that were more pronounced in the nonsurvivors. Noninvasive systems may be acceptable alternatives where invasive monitoring is not available.

What should be monitored? The past, present, and future of physiological monitoring

The status of conventional monitoring by vital signs and present concepts of invasive monitoring with the balloon-tipped pulmonary artery (Swan-Ganz) catheter are reviewed. Survivors of high-risk general surgery were observed to have cardiac index (CI) values averaging 4.5 L/min.m2, oxygen delivery (DO2) greater than 600 mL/min.m2, and oxygen consumption (VO2) greater than 170 mL/min.m2. By contrast, those who subsequently died during their hospitalization maintained relatively normal CI, DO2, and VO2 values. However, in the immediate postoperative period, values for other hemodynamic variables were not greatly different for survivors and nonsurvivors or different from the normal range. A predictive index based on these observations predicted outcome correctly in 94% of the subjects in a subsequent prospective study. The use of survivor values as appropriate therapeutic goals was tested in prospective randomized clinical trials and was found to reduce mortality and morbidity significantly. Simultaneous invasive and noninvasive hemodynamic and oxygen-transport monitoring systems were evaluated in high-risk postoperative patients to describe unanticipated adverse circulatory events. Before the monitored event, about three-fourths of the patients exhibited normal function. At the nadir, cardiac functions decreased in about two-thirds, perfusion decreased in more than one-half, and paO2 fell in only one-fourth. Two-thirds recovered with increased cardiac function, more than one-half had improved perfusion, and paO2 increased in fewer than one-fifth of monitored events. These data provide an information base for criteria needed to develop therapeutic decision rules for noninvasive monitoring systems. When noninvasive data are continuously displayed early in the course of critical illness and high-risk conditions, therapy may be instituted early, while physiological deficits are still minimal and easily reversible.

Incidence, physiologic description, compensatory mechanisms, and therapeutic implications of monitored events

We described 663 unanticipated monitored circulatory events in 247 high-risk surgical patients by simultaneous invasive and noninvasive hemodynamic and oxygen transport monitoring systems. Unanticipated monitored events were defined as sudden reductions (greater than 20%) in cardiac index (CI), PaO2, SaO2, transcutaneous PO2 (PtcO2), and PtcO2/PaO2 index, or decreases to the lower limits of satisfactory values, specifically: PaO2 less than 70 torr, SaO2 less than 95%, PtcO2 less than 50 torr, and PtcO2/PaO2 less than 0.6. Essentially, monitored events are the small variations superimposed on the overall physiologic patterns that describe the entire course of critical illnesses. Monitored events are described by their baseline values just before each event, at the nadir of the event, and at the recovery from the event. To simplify presentation of complex changes in many variables, the circulatory changes were evaluated in terms of cardiac, pulmonary, and peripheral perfusion functions. Common patterns of these monitored events and the incidence of these patterns in high-risk surgical patients were described. Before the unanticipated monitored event, there were normal or increased heart, lung, and perfusion functions in about three fourths of the events. At the nadir, cardiac functions decreased in about two thirds, perfusion decreased in over half, and lung function fell in only one quarter of the events. Recovery occurred with increased cardiac function in two thirds, improved perfusion in over half, and increased lung function in less than one fifth of these monitored events. Noninvasive and invasive hemodynamic and oxygen transport variables were measured simultaneously to evaluate compensatory and decompensatory patterns.(ABSTRACT TRUNCATED AT 250 WORDS)