Michael M. Hirschl

Accuracy of oscillometric blood pressure measurement according to the relation between cuff size and upper-arm circumference in critically ill patients.

Objective: To evaluate the accuracy of oscillometric blood pressure measurement according to the relation between cuff size and upper‐arm circumference in critically ill patients. Design: Prospective data collection. Setting: Emergency department in a 2,000‐bed inner city hospital. Patients: Thirty‐eight patients categorized into three groups according to their upper‐arm circumference (group I: 18‐25 cm; group II: 25.1‐33 cm; and group III: 33.1‐47.5 cm) were enrolled in the study protocol. Interventions: In each patient, all three cuff sizes (Hewlett‐Packard Cuff 40401 B, C, and D) were used to perform an oscillometric blood pressure measurement at least within 3 mins until ten to 20 measurements for each cuff size were achieved. Invasive mean arterial blood pressure measurement was done by cannulation of the contralateral radial artery with direct transduction of the systemic arterial pressure waveform. The corresponding invasive blood pressure value was obtained at the end of each oscillometric measurement. Measurement and Main Results: Overall, 1,494 pairs of simultaneous oscillometric and invasive blood pressure measurements were collected in 38 patients (group I, n = 5; group II, n = 23; and group III, n = 10) over a total time of 72.3 hrs. Mean arterial blood pressure ranged from 35 to 165 mm Hg. The overall discrepancy between oscillometric and invasive blood pressure measurement was −6.7 ± 9.7 mm Hg (p < .0001), if the recommended cuff size according to the upper‐arm circumference was used (539 measurements). Of all the blood pressure measurements, 26.4% (n = 395) had a discrepancy of ≥10 mm Hg and 34.2% (n = 512) exhibited a discrepancy of ≥20 mm Hg. No differences between invasive and noninvasive blood pressure measurements were noted in patients either with or without inotropic support (−6.6 + 7.2 vs. −8.6 + 6.8 mm Hg; not significant). Conclusion: The oscillometric blood pressure measurement significantly underestimates arterial blood pressure and exhibits a high number of measurements out of the clinically acceptable range. The relation between cuff size and upper‐arm circumference contributes substantially to the inaccuracy of the oscillometric blood pressure measurement. Therefore, oscillometric blood pressure measurement does not achieve adequate accuracy in critically ill patients.

Factors influencing the accuracy of oscillometric blood pressure measurement in critically ill patients.

ObjectiveComparison of oscillometric blood pressure measurement with two different devices (M3000A using a new algorithm and M1008A using an established algorithm, both Hewlett Packard) and evaluation of current recommendations concerning the relation between cuff size and upper arm circumference in critically ill patients. DesignProspective data collection. SettingEmergency department in a 2000-bed inner-city hospital. PatientsA total of 30 patients categorized into three groups according to their upper arm circumference (I, 18–25 cm; II, 25.1–33 cm; III, 33.1–47.5 cm) were enrolled in the study protocol. InterventionsIn each patient, two noninvasive blood pressure devices with three different cuff sizes were used to perform oscillometric blood pressure measurement. Invasive mean arterial blood pressure measurement was done by cannulation of the radial artery. Measurement and Main ResultsOverall, 1,011 pairs of simultaneous oscillometric and invasive blood pressure measurements were collected in 30 patients (group I, n = 10; group II, n = 10; group III, n = 10). The overall discrepancy between both methods with the M3000A was −2.4 ± 11.8 mm Hg (p < .0001) and, with the M1008A, −5.3 ± 11.6 mm Hg (p < .0001) if the recommended cuff size according to the upper arm circumference was used (352 measurements). If smaller cuff sizes than recommended were used (308 measurements performed in group II and III), the overall discrepancy between both methods with the M3000A was 1.3 ± 13.4 mm Hg (p < .024) and, with the M1008A, −2.3 ± 11.5 mm Hg (p < .0001). ConclusionThe new algorithm reduced the overall bias of the oscillometric method but still showed a significant discrepancy between both methods of blood pressure measurement, primarily due to the mismatch between upper arm circumference and cuff size. The improvement of the algorithm alone could not result in a sufficient improvement of oscillometric blood pressure measurement. A reevaluation of the recommendations concerning the relation between upper arm circumference and cuff size are urgently required if oscillometric blood pressure measurement should become a reasonable alternative to intra-arterial blood pressure measurement in critically ill patients.

Creatine kinase-MB fraction and cardiac troponin T to diagnose acute myocardial infarction after cardiopulmonary resuscitation

OBJECTIVES This study sought to evaluate the diagnostic value of the biochemical markers creatine kinase (CK), creatine kinase-MB fraction (CK-MB) and cardiac troponin T (cTNT) to diagnose acute myocardial infarction (AMI) after cardiopulmonary resuscitation (CPR). BACKGROUND Elevations of CK and CK-MB after CPR are a frequent finding and might be associated with ischemic myocardial injury, as well as physical trauma to the chest. METHODS Patients who had cardiac arrest and primary successful resuscitation were included in the study. The diagnosis of AMI was confirmed or ruled out by means of typical electrocardiographic findings, thallium-201 myocardial scintigraphy or autopsy, if death occurred during the hospital period, in 39 primary survivors of sudden cardiac death. In 24 patients (62%) the diagnosis of AMI was established. Serum cTNT, CK and CK-MB were measured, and the CK-MB/CK ratio was calculated on admission and after 12 h. RESULTS On admission all markers of myocardial injury proved to be weak methods for the diagnosis of AMI. After 12 h cTNT as well as CK-MB exhibited a similar diagnostic performance; CK and the CK-MB/CK ratio proved to be worthless. Sensitivity and specificity for a cTNT cutoff value of 0.6 ng/ml, 12 h after cardiac arrest, were 96% and 80%, respectively. For a CK-MB cutoff value of 26 U/liter, sensitivity was 96% and specificity was 73%. CONCLUSIONS Cardiac TNT and CK-MB are valuable tools in detecting AMI as the cause of sudden cardiac death. However, there is a considerable lack of sensitivity and specificity. Cardiac injury is probably caused not only by AMI, but also by myocardial damage related to CPR efforts.

Noninvasive assessment of cardiac output in critically ill patients by analysis of the finger blood pressure waveform.

OBJECTIVE To assess whether the measurement of cardiac output by computer-assisted analysis of the finger blood pressure waveform can substitute for the thermodilution method in critically ill patients. DESIGN Prospective data collection. SETTING Emergency department in a 2000-bed inner city hospital PATIENTS Forty-six critically ill patients requiring invasive monitoring for clinical management were prospectively studied. INTERVENTIONS Under local anesthesia a 7-Fr pulmonary artery catheter was inserted via the central subclavian or jugular vein. Cardiac output was determined by the use of a cardiac output computer and injections of 10 mL ice-cold glucose 5%. Noninvasive cardiac output was calculated from the finger blood pressure waveform by the use of the test software program. MEASUREMENTS AND MAIN RESULTS Three hundred twenty-three pairs of invasive and noninvasive hemodynamic measurements were collected in intervals of 30 mins from 46 patients (mean age 61.9 +/- 12.4 yrs; 35 male, 11 female). The average cardiac index during the study period was 2.83 L/min/m2 (range 0.97 to 5.56). The overall discrepancy between both measurements was 0.14 L/min/m2 (95% confidence interval: 0.10-.018, p < .001). Seventy-five (23.2%) measurements had an absolute discrepancy > +/- 0.50 L/min/m2. Noninvasive and invasive comparisons of mean differential cardiac output were out of phase for 9.7% of all readings. CONCLUSION Computer-assisted analysis of finger blood pressure waveform to assess cardiac output is not a substitute for the thermodilution method due to a high percentage (23.2%) of inaccurate readings; however, it may be a useful tool for the detection of relative hemodynamic trends in critically ill patients.

Simultaneous comparison of thoracic bioimpedance and arterial pulse waveform-derived cardiac output with thermodilution measurement.

Objective To compare the accuracy and reliability of thoracic electrical bioimpedance (TEB) and the arterial pulse waveform analysis with simultaneous measurement of thermodilution cardiac output (TD-CO) in critically ill patients. Design Prospective data collection. Setting Emergency department and critical care unit in a 2,000-bed inner-city hospital. Patients A total of 29 critically ill patients requiring invasive hemodynamic monitoring for clinical management were prospectively studied. Interventions Noninvasive cardiac output was simultaneously measured by a TEB device and by analysis of the arterial pulse waveform derived from the finger artery. Invasive cardiac output was determined by the thermodilution technique. Measurements and Main Results A total of 175 corresponding TD-CO and noninvasive hemodynamic measurements were collected in 30-min intervals. They revealed an overall bias of 0.34 L/min/m2 (95% confidence interval, 0.24–0.44 L/min/m2;p < .001) for the arterial pulse waveform analysis and of 0.61 L/min/m2 (95% confidence interval, 0.50–0.72 L/min/m2;p < .001) for the TEB. In 39.4% (n = 69) of all measurements, the discrepancy between arterial pulse waveform analysis and TD-CO was >0.50 L/min/m2. The discrepancies of the arterial pulse waveform analysis correlated positively with the magnitude of the cardiac index (r2 = 0.29;p < .001). In 56.6% (n = 99) of all measurements, the discrepancy between TEB and TD-CO was >0.50 L/min/m2. The magnitude of the discrepancies of the TEB was significantly correlated with age (r2 = 0.17;p = .02). Measurements were in phase in 93.2% of all arterial pulse waveform analysis and in 84.9% of all TEB readings (p < .001). Conclusions The arterial pulse waveform analysis exhibits a greater accuracy and reliability as compared with the TEB with regard to overall bias, number of inaccurate readings, and phase lags. The arterial pulse waveform analysis may be useful for the monitoring of hemodynamic changes. However, both methods fail to be a substitute for the TD-CO because of a substantial percentage of inaccurate readings.

Evaluation of a point-of-care system for quantitative determination of troponin T and myoglobin.

Abstract We present the results of a multicenter evaluation of a new point-of-care system (Cardiac Reader) for the quantitative determination of cardiac troponin T (CARDIAC T Quantitative test) and myoglobin (CARDIAC M test) in whole blood samples. The Cardiac Reader is a CCD camera that optically reads the immunochemical test strips. The measuring range is 0.1 to 3 μg/l for CARDIAC T Quantitative and 30 to 700 μg/l for CARDIAC M. Both tests are calibrated by the manufacturer. The reaction times of the tests are 12 or 8 minutes, respectively. Method comparisons were performed with 281 heparinized blood samples from patients with suspected acute coronary syndromes. The results obtained with CARDIAC T Quantitative showed a good agreement compared with cardiac troponin T ELISA (r = 0.89; y = 0.93x + 0.02). The method comparison between CARDIAC M and Tina-quant Myoglobin also showed a good agreement between both assays (r = 0.98; y = 0.92x + 1.6). Test lot-to-lot comparisons yielded differences of 2% and 6% for CARDIACT Quantitative and of 0 to 11% for CARDIACM. The within-run imprecision with blood samples and control materials was acceptable for CARDIAC T Quantitative (CV 10 to 15%) and good for CARDIAC M (CV 5 to 10%). The between-instrument CV was below 7% for CARDIACT Quantitative and below 5% for CARDIACM. The cross-reactivity of CARDIAC T Quantitative with skeletal troponin T was approximately 0.003%. No significant analytical interference was detected for any of the assays in investigations with biotin (up to 100 μg/l), hemoglobin (up to 0.125 mmol/l), hematocrit (26 to 52%), bilirubin (up to 340 μmol/l), triglycerides (up to 5.0 mmol/l), and 18 standard drugs. With the Cardiac Reader reliable quantitative results can be easily obtained for both cardiac markers. The system is, therefore, particularly suitable for use in emergency rooms, coronary care units and small hospitals.

Accuracy and reliability of noninvasive continuous finger blood pressure measurement in critically ill patients

OBJECTIVE To evaluate the accuracy and reliability of noninvasive continuous finger blood pressure measurement in critically ill patients. DESIGN Prospective data collection. SETTING Emergency department in a 2,000-bed hospital. PATIENTS Thirty-nine patients admitted to the emergency department requiring invasive arterial blood pressure monitoring were enrolled to the study protocol. INTERVENTIONS Continuous noninvasive blood pressure measurement was performed on the middle phalanx of the second and third finger, using a test instrument which provides continuous arterial waveform display with the use of a finger cuff. Invasive mean arterial blood pressure measurement was done by cannulation of the radial artery and direct transduction of the systemic arterial pressure waveform. MEASUREMENTS AND MAIN RESULTS Three thousand one hundred eighteen pairs of simultaneous finger cuff and intra-arterial blood pressure measurements were collected in 1-min intervals from 39 patients over a total of 51.8 hrs. The overall discrepancy between both measurements was 0.10 mm Hg. The standard deviation of the differences was +/- 5.02 mm Hg. The mean bias in patients treated with catecholamines was 0.01 mm Hg and was not different from the bias observed in patients without catecholamines (mean bias: 0.23 mm Hg; p > .22). Whereas 95% of all comparisons between finger cuff and intra-arterial measurement had a discrepancy < or = +/- 10 mm Hg, 4.7% had a discrepancy between +/- 10.1 to 15 mm Hg and 0.3% exhibited a discrepancy > +/- 15 mm Hg. In 29 (74%) patients, the duration of errors > 10 mm Hg was < or = 1 min. In seven (18%) patients, the duration of errors > 10 mm Hg was between 2 to 3 mins and in three (8%) patients, the errors lasted for > 3 mins. CONCLUSIONS Our data provide a guide to the accuracy and reliability of noninvasive finger blood pressure measurements in critically ill patients. Although most test instrument measurements were reliable, in 8% of all patients large discrepancies (> 10 mm Hg) between both measurements with a duration of > 3 mins were noted. Concerning the considerable risk for arterial cannulation, our preliminary data demonstrate that the test instrument (PORTAPRES, TNO Biomedical Instrumentation Research Unit; The Netherlands) is an advance in noninvasive monitoring of critically ill patients and may be useful in most emergency clinical settings.

Association between hypertensive urgencies and subsequent cardiovascular events in patients with hypertension.

Objective To determine whether patients with hypertensive urgency have a higher risk for subsequent cardiovascular events compared with hypertensive patients without this event. Methods Overall, 384 patients with hypertensive urgency and 295 control patients were followed up for at least 2 years. Hypertensive urgency was defined as a systolic blood pressure above 220 mmHg and/or a diastolic blood pressure above 120 mmHg without any evidence of acute end-organ damage. The control group consisted of patients admitted to the emergency department with a systolic blood pressure between 135 to 180 mmHg and a diastolic blood pressure between 85–110 mmHg. The number of cardiovascular events defined as acute coronary syndrome, acute stroke, atrial fibrillation, acute left ventricular failure and aortic aneurysm were consecutively analyzed during follow-up. The median follow-up time was 4.2 years (interquartile range 2.9–5.7 years). Twenty-six patients of the urgency group and 23 patients of the control group were lost for follow-up. Results Overall, 117 (17%) patients had nonfatal clinical cardiovascular events and 13 had (2%) fatal cardiovascular events. The frequency of cardiovascular events was significantly higher in patients with hypertensive urgencies (88 vs. 42; P = 0.005). The Cox regression analysis identified age (P < 0.001) and hypertensive urgencies (P = 0.035) as independent predictors for subsequent cardiovascular events. Conclusions Hypertensive urgencies are associated with an increased risk for subsequent cardiovascular events in patients with arterial hypertension.

The influence of chest compressions and external defibrillation on the release of creatine kinase-MB and cardiac troponin T in patients resuscitated from out-of-hospital cardiac arrest

OBJECTIVES This study sought to determine the influence of resuscitative procedures, such as chest compressions and external defibrillation, on the release of creatine kinase (CK)-MB and cardiac troponin T (cTnT). METHODS In 87 patients with out-of-hospital cardiac arrest and successful cardiopulmonary resuscitation (CPR), the initial ECG rhythm, the duration of cardiac arrest and CPR, and the number of defibrillations were assessed on arrival in the hospital. The serum CK-MB and cTnT were measured 12 h after the event. We also assessed whether the patient developed cardiogenic shock within 12 h, and if the patient had acute myocardial infarction (AMI), which was confirmed or eliminated by of typical ECG findings, thallium-201 myocardial scintigraphy, or autopsy within the hospital stay. A backward stepwise linear regression model was applied to assess the association between the markers of myocardial injury (CK-MB and cTnT) and the above clinical variables. RESULTS CK-MB concentrations were independently associated with the presence of AMI [B 68.5 (SE 28.5, P = 0.018)], the duration of CPR (as a measure of trauma to the chest by means of chest compressions) [B 2.07 (SE 1.01, P = 0.045)] and cardiogenic shock [B 52.3 (SE 23.4, P = 0.03)]. The remaining clinical variables listed were excluded by the model. Cardiac troponin T concentrations were only associated with the presence of AMI [B 4.86 (SE 1.34, P = 0.0005)]. There was a non-significant association between increasing serum cTnT concentrations and the presence of cardiogenic shock [B 2.51 (SE 1.46, P = 0.09)]. The remaining clinical variables were excluded by the model. CONCLUSION The release of CK-MB appears to be influenced by the duration of resuscitation and the presence of cardiogenic shock. This has to be considered when interpreting serum CK-MB concentrations after CPR. The release of cTnT seems to be only associated with acute myocardial infarction, but not with the duration of chest compressions, or with the number of defibrillations administered.

Predictors of survival in unselected patients with acute myocardial infarction requiring continuous catecholamine support

BACKGROUND Several predictors of survival have been described in selected subgroups of patients suffering from acute myocardial infarction. However, data on unselected patients with acute myocardial infarction and cardiogenic shock, including patients with out-of hospital cardiac arrest, are missing. We aimed to assess predictors of survival for an unselected cohort of patients representative of clinical practice who experienced acute myocardial infarction and required continuous catecholamine support for circulatory failure. METHODS The study was performed at a 2000 bed university hospital. All consecutive patients admitted to our emergency department with acute myocardial infarction were prospectively enrolled in a clinical trial from 1993 to 2000. DESIGN A retrospective cohort study was performed on patients with myocardial infarction requiring catecholamine support within the first 24 h. Primary endpoint was in-hospital mortality. RESULTS The analysis was carried out on 262 patients, 189 men (72%), median age 65 years (IQR 53-73). Out-of-hospital cardiac arrest was reported in 47% (122/262). In-hospital mortality was 53% (138/262). Survivors as compared to non-survivors exhibited significant differences with respect to age (60 vs. 68 years, P<0.0001), systolic and diastolic blood pressure on admission (110 vs. 102 mmHg, P=0.01 and 64 vs. 58 mmHg, P=0.006, respectively), initial blood serum lactate (6.8 vs. 8.3, P=0.01), peak CKMB level (93 vs. 138 U/l, P=0.005), use of adrenaline (epinephrine) (38 vs. 68%, P<0.0001) and any attempt of revascularisation (76 vs. 63%, P=0.03). In a multivariate model younger age [OR 1.06 (CI 1.03-1.10), P<0.001], no use of adrenaline [OR 2.63 (CI 1.35-5.26) P=0.005] and lower peak CKMB [OR 1.01 (CI 1.01-1.01), P<0.0001] were independently associated with in-hospital survival. CONCLUSION In unselected patients including CPR survivors with acute myocardial infarction requiring continuous catecholamine support, younger age, the absence of continuous adrenaline administration and a lower peak CKMB were independently associated with increased in-hospital survival.