Intra-operative monitoring--many alarms with minor impact.

Alarms are key components of peri-operative monitoring devices, but a high false-alarm rate may lead to desensitisation and neglect. The objective of this study was to quantify the number of alarms and assess the value of these alarms during moderate-risk surgery. For this purpose, we analysed documentation of anaesthesia workstations during 38 surgical procedures. Alarms were classified on technical validity and clinical relevance. The median (IQR [range]) alarm density per procedure was 20.8 (14.5-34.2 [3.7-85.6]) alarms.h⁻¹ (1 alarm every 2.9 min) and increased during induction and emergence of anaesthesia, with up to one alarm per 0.99 min during these periods (p < 0.001). Sixty-four per cent of all alarms were clinically irrelevant, whereas 5% of all alarms required immediate intervention. The positive predictive value of an alarm during induction and emergence was 20% (95% CI 16-24%) and 11% (95% CI 8-14%), respectively. This study shows that peri-operative alarms are frequently irrelevant, with a low predictive value for an emerging event requiring clinical intervention.

Effect of fluid loading with saline or colloids on pulmonary permeability, oedema and lung injury score after cardiac and major vascular surgery.

BACKGROUND: The optimal type of fluid for treating hypovolaemia without evoking pulmonary oedema is still unclear, particularly in the presence of pulmonary vascular injury, as may occur after cardiac and major vascular surgery. METHODS: In a single-centre, prospective, single-blinded clinical trial 67 mechanically ventilated patients were randomly assigned to receive saline, gelatin 4%, HES 6% or albumin 5%, according to a 90 min fluid loading protocol with target central venous pressure of 13 and pulmonary capillary wedge pressure of 15 mm Hg, within 3 h after cardiac or major vascular surgery. Before and after the protocol, we recorded haemodynamics and ventilatory variables and took chest radiographs. The pulmonary vascular injury was evaluated using the 67Ga-transferrin pulmonary leak index (PLI) and extravascular lung water (EVLW). Plasma colloid osmotic pressure (COP) was determined and the lung injury score (LIS) was calculated. RESULTS: More saline was infused than colloid solutions (P<0.005). The COP increased in the colloid groups and decreased in patients receiving saline. Cardiac output increased more in the colloid groups. At baseline, PLI and EVLW were above normal in 60 and 30% of the patients, with no changes after fluid loading, except for a greater PLI decrease in HES than in gelatin-loaded patients. The oxygenation ratio improved in all groups. In the colloid groups, the LIS increased, because of a decrease in total respiratory compliance, probably associated with an increase in intrathoracic plasma volume. CONCLUSIONS: Provided that fluid overloading is prevented, the type of fluid used for volume loading does not affect pulmonary permeability and oedema, in patients with acute lung injury after cardiac or major vascular surgery, except for HES that may ameliorate increased permeability. During fluid loading, changes in LIS (and respiratory compliance) do not represent changes in pulmonary permeability or oedema.

Anesthesiological hazards during laparoscopic transhiatal esophageal resection: a case control study of the laparoscopic-assisted vs the conventional approach.

BACKGROUND: Interest for minimal invasive approach of esophagus resection is increasing. Today, a minimally invasive transhiatal esophagectomy is possible and is accepted widespread. Since cardiopulmonary changes during laparoscopic dissection of the mediastinum has not been studied yet we assessed the anesthesiological consequences of pneumothorax during laparoscopic mediastinal dissection. METHODS: In this case control study, 25 laparoscopically assisted transhiatal espohagus resections were compared with a control group consisting of 20 open transhiatal esophagus resections. Patient characteristics and intraoperative haemodynamic, respiratory, and ventilatory parameters were assessed. RESULTS: The laparoscopic assisted procedure was performed successfully in 12 of the 20 patients. The duration of the laparoscopic assisted procedure, compared to the open group was significantly longer (p<0.05). Intraoperative blood loss was significantly less in the laparoscopic group (p<0.05). Mediastinal dissection resulted in entry of the pleura in 84% of the open and 93% of the laparoscopic assisted procedure. Carbonedioxide pneumothorax resulted in increased end-tidal CO2)and airway pressure levels and decreased lung compliance. Airway pressure showed a significant difference between the groups (p<0.05). Hemodynamic parameters did not differ between groups significantly. There were no differences in postoperative cardiopulmonary complications. CONCLUSIONS: Laparoscopic assisted transhiatal esophagectomy is a safe procedure and has no increased risk of postoperative cardiopulmonary complications compared to thr conventional approach. The anesthesiologist and the surgeon must be aware of the potential risk of pleural injury to manage cardiopulmonary compromises and minimize complications.

Relationship of steady state and ambulatory blood pressure variability to left ventricular mass and urinary albumin excretion in essential hypertension.

A relationship exists between blood pressure and cardiovascular morbidity and mortality. Recent data suggest that the variability of blood pressure is also related to hypertensive target organ damage. We studied the relationship of ambulatory daytime and night-time and supine beat-to-beat Finapres blood pressure variability to left ventricular mass index (LVMI) and urinary albumin excretion (albumin/creatinine ration: ACR) in 33 hypertensive patients, untreated for more than 3 months. In a multiple stepwise regression model the strongest relationship with the LVMI existed for night-time systolic pressure (R = 0.46, multiple regression coefficient: 0.90 +/- 0.26 P < .01) and daytime diastolic blood pressure variability (multiple R increased to 0.60, multiple regression coefficient 3.16 +/- 1.18, P < .05). Log ACR had the strongest relationship to ambulatory systolic daytime pressure (R = 0.40, multiple regression coefficient 0.0093 +/- 0.0040, P < .05) and the variability of diastolic Finapres blood pressure (multiple R increased to 0.52, multiple regression coefficient 0.081 +/- 0.0036, P < .05). Both ambulatory and steady state blood pressure variability are related to early hypertensive target organ damage. This relationship exists independent of the height of blood pressure .

Office, nurse, basal and ambulatory blood pressure as predictors of hypertensive target organ damage in male and female patients.

The objective of this study was to assess the value of two substitutes for ambulatory blood pressure (BP) monitoring: nurse-measured BP and BP measured by an automated device during 1 h resting in the clinic (basal BP). Hypertensive patients in an academic out-patients clinic were selected consecutively. We compared the relation of indices of early target organ damage (echocardiographically determined left ventricular mass index (LVMI) and urinary albumin excretion (expressed as albumin/creatinine ratio: ACR) to physician measured and nurse measured basal and ambulatory BP. The relation of BP to LVMI and the logACR were also studied for both sexes separately. Sixty-two patients (28 men, 34 women) were included, all untreated for >3 months. Systolic office BP was not significantly related to the LVMI (r2 = 0.04, P > 0.05), whereas nurse measured (r2 = 0.11, P < 0.05), basal (r2 = 0.13, P < 0.01) and ambulatory daytime (r2 = 0.13, P < 0.05) and night time (r2 = 0.17, p < 0.001) SBP did have a significant relation to LVMI. There was no difference in the relation of office, nurse, basal or ambulatory BP to logACR. In contrast to the highly significant relation of SBP to LVMI for male patients (day: r2 = 0.29, P < 0.01, night: r2 = 0.46, P < 0.001) this relation was non-existent for female patients (day: r2 = 0.09, P > 0.05, night: r2 = 0.02, P > 0.05). The relation between BP and logACR did not differ between the sexes. We conclude that: (1) to some degree nurse measured and basal BP may be considered as better predictors of early hypertensive target organ damage than physician measured BP; and (2) there is a pronounced sex difference in the relation of BP to left ventricular mass.

Effects of acute and chronic angiotensin converting enzyme inhibition by spirapril on cardiovascular regulation in essential hypertensive patients. Assessment by spectral analysis and haemodynamic measurements.

1. The effects of a first dose and of chronic treatment with spirapril, a novel angiotensin converting enzyme (ACE) inhibitor, on short-term blood pressure and heart rate fluctuations were assessed by fast Fourier spectral analysis. The effects on systemic haemodynamics in supine and standing position were also studied. We treated 11 patients with 3 mg and 13 patients with 12 mg spirapril for 8 weeks. 2. Overall blood pressure variability was not changed by spirapril. By spectral analysis the changes in blood pressure and heart rate variability in various frequency bands can be assessed, which may be related to changes in activity of the autonomic nervous system. The relative power in the mid-frequency band (0.08-0.12 Hz) of supine systolic pressure was 23 +/- 10% during placebo and decreased during treatment with 12 mg to 11 +/- 4% (P < 0.01 vs placebo, first dose) and to 13 +/- 6% (P < 0.01, chronic treatment). Standing systolic mid-frequency power was 38 +/- 12% during placebo and decreased to 27 +/- 9% (P < 0.01 vs placebo) after the first dose of 12 mg, but it did not decrease after chronic treatment (29 +/- 13%). Treatment with 3 mg induced no changes in mid-frequency blood pressure variability. A decrease in power of the mid-frequency band may point to a decrease in sympathetic vascular drive. The power in the high-frequency band (0.15-0.40 Hz) of heart rate did not change after treatment, suggesting that there is no change in the vagal cardiac drive. 3. Supine blood pressure decreased by a decrease in vascular resistance by 16 +/- 23% (3 mg) and 14 +/- 19% (12 mg) after 8 weeks treatment. Heart rate, stroke volume and cardiac output did not change. No orthostatic hypotension occurred after the first dose. In the 12 mg group the orthostatic induced rise in heart rate (compared with supine) increased from + 9 +/- 5 beats min-1 (placebo) to + 14 +/- 4 beats min-1 (P < 0.05) after the first dose. No changes in the orthostatic heart rate increase occurred in the 3 mg group. The orthostatic changes in stroke volume, cardiac output and vascular resistance were not influenced by spirapril. 4. In conclusion, the decrease in mid-frequency blood pressure variability may suggest an inhibitory effect of acute and chronic ACE inhibition upon sympathetic vasomotor control. Vagal activity was not influenced as high-frequency heart rate variability did not change. Acute and chronic ACE inhibition did not blunt important cardiovascular reflexes, as the haemodynamic response to orthostasis remained intact.

Circadian profile of systemic hemodynamics.

We determined the continuous 24-hour profile of mean arterial pressure, heart rate, stroke volume, cardiac output, and total peripheral resistance in eight healthy ambulatory volunteers. Beat-to-beat intra-arterial blood pressure was recorded with the Oxford system; subjects were ambulant during daytime and slept at night. Beat-to-beat stroke volume was determined by the pulse contour method from the arterial pulse wave. During the nighttime, compared with the daytime average, there was a decrease in blood pressure (9 mm Hg), heart rate (18 beats per minute), and cardiac output (29%); stroke volume showed a small decrease (7%), and total peripheral resistance increased unexpectedly by 22%. When subjects arose in the morning a steep increase in cardiac output and decrease in total peripheral resistance were found. Comparable changes were seen during a period of supine resting in the afternoon, whereas physical exercise caused opposite changes in hemodynamics. This pattern was observed in all subjects. We conclude that the circadian pattern of cardiac output and total peripheral resistance originates from the day-night pattern in physical activity: during the nighttime, blood flow to the skeletal muscles is decreased through local autoregulation, which increases total peripheral resistance and decreases cardiac output compared with the daytime.

Effects of aging on blood pressure variability in resting conditions.

The objective of this study was to determine the effect of aging on beat-to-beat blood pressure and pulse interval variability in resting conditions and to determine the effect of aging on the sympathetic and vagal influence on the cardiovascular system by power spectral analysis of blood pressure and pulse interval. We studied three groups of healthy, normotensive subjects: young (10 to 15 years, n = 16), adult (20 to 40 years, n = 16), and elderly (70 to 90 years, n = 25). Beat-to-beat blood pressure was measured by Finapres during 20 minutes supine and 10 minutes standing. Overall systolic and diastolic blood pressures and pulse interval variability were determined as SD and as coefficient of variation. Also, relative powers of the mid-frequency (0.08 to 0.12 Hz) and high-frequency bands (0.15 to 0.40 Hz) were determined by spectral analysis. In these subjects no differences in blood pressure variability (either as SD or coefficient of variation) were found between age groups, except for the coefficient of variation of standing diastolic blood pressure, which decreased with aging. Pulse interval variability decreased with aging. Power of the mid-frequency band of systolic and diastolic blood pressures was markedly decreased in the elderly, especially in the standing position. Power of the high-frequency band of pulse interval was also decreased in the elderly. Baroreflex sensitivity calculated by fast Fourier transformation spectral analysis was decreased in the elderly subjects compared with the younger groups. In conclusion, we found no change in the overall variability of blood pressure with aging. Mid-frequency spectral power of blood pressure and mid- and high-frequency spectral powers of pulse interval variability were decreased in the elderly. These results suggest that aging does not merely influence the magnitude of blood pressure and pulse interval variability but causes a complex rearrangement of the variability pattern by changes in neurocardiovascular regulation.

24-hour ambulatory blood pressure monitoring and spirapril in mild to severe essential hypertension: a randomized dose comparison.

This was a multicentre randomized, double-blind, parallel-group study to compare the antihypertensive efficacy of spirapril at 3 mg with 12 mg once daily, as determined by 24-hour ambulatory blood pressure monitoring (ABPM), in patients with mild to severe essential hypertension. Following a 4-week placebo run-in phase, 52 male and female outpatients, aged 23-67 years with mild to severe essential hypertension [diastolic blood pressure (DBP) > or = 100 mmHg and < 120 mmHg] were randomized to receive spirapril at either 3 mg or 12 mg once daily for 8 weeks. At the end of active treatment and using the standard mercury sphygmomanometer, the number of responders (sitting DBP < 90 mmHg, but decrease > or = 10 mmHg) was the same in both groups (32% and 37%). There were mean decrease in both systolic blood pressure (SBP) and DBP at trough with both 3 mg and 12 mg doses: -9/-7 mmHg and -12/-7 mmHg, respectively. The rate of normalization (trough DBP < or = 90 mmHg) was 12% and 30% with the 3 mg and 12 mg doses, respectively. Of the 44 patients whose daytime ABPM could be compared, one of 20 patients taking 3 mg of spirapril, and 9 of 24 taking 12 mg of spirapril achieved a DBP < or = 90 mmHg for all time intervals while awake. The differences in blood pressure-lowering were significant with both SBP and DBP during the day and at the end of the dosing interval (p < 0.001 and p < 0.01, respectively). The changes from baseline at 24 hours postdose for SBP/DBP were -3/-6 mmHg with 3 mg and -14/-12 mmHg with 12 mg of spirapril.(ABSTRACT TRUNCATED AT 250 WORDS)

LAM 100/Marshall F-88: accuracy and precision of a new device for discontinuous finger blood pressure measurement.

We tested the performance of the LAM 100 (also known as the Marshall F-88), a semiautomated oscillometric device for discontinuous BP measurement at the finger, which could be very suitable for self-recording of BP because of its small size and convenient mode of operation. The LAM 100 was compared with the random zero sphygmomanometer and with BP measured by the Finapres for beat-to-beat measurement of finger arterial pressure in 40 patients following guidelines of the AAMI. Compared with the random zero sphygmomanometer the LAM 100 underestimated SBP by 9 mmHg (SD 12) and DBP by 7 mmHg (SD 9). These differences exceed the limits set by the AAMI. The differences between the LAM 100 and the random zero spghymomanometer could not be explained by physiological peripheral pulse wave changes because Finapres SBP was underestimated by 4 mmHg (SD 15) and DBP was overestimated by the LAM 100 by 8 mmHg (SD 10). We conclude that the LAM 100 is not suitable for the diagnosis and management of hypertension.

Nurse-measured or ambulatory blood pressure in routine hypertension care.

OBJECTIVE: Nurses are considered to evoke less white-coat hypertension, and might therefore be able to estimate average blood pressure as well as and more conveniently than ambulatory monitoring. The objective of the present study was to determine the correspondence between blood pressure measured by a doctor or a nurse and ambulatory blood pressure. DESIGN: Hypertensive patients seen in an academic outpatients clinic were selected consecutively. Blood pressure measurements taken under different situations and by different persons were subjected to cross-sectional comparison. METHODS: Average daytime ambulatory blood pressure was compared to blood pressure measured in triplicate by a nurse and by a physician in 110 patients. The value of nurse-measured diastolic blood pressure as a diagnostic test for the detection of white-coat hypertension was compared with ambulatory monitoring as the standard. RESULTS: Physician-measured diastolic pressure was 3 +/- 11 mmHg (P < 0.05) higher on average than ambulatory pressure, but the difference between nurse-measured and ambulatory diastolic pressure was 0 +/- 12 mmHg (not significant). Systolic pressure measured either by a physician or by a nurse overestimated daytime ambulatory blood pressure by the same amount. For the identification of white-coat hypertension, the sensitivity and specificity of nurse-measured blood pressure were 0.32 and 0.92, respectively, and the positive and negative predictive values were 0.53 and 0.82, respectively. CONCLUSIONS: Nurse-measured blood pressure was not a very reliable indicator of white-coat hypertension, as a negative test was 18% in error. Thus, nurses rather than doctors should routinely measure blood pressure, but nurse-measured blood pressure is not an acceptable substitute for ambulatory monitoring.

Disparities in circulatory adjustment to standing between young and elderly subjects explained by pulse contour analysis.

1. The circulatory adjustment to standing was investigated in two age groups. Young subjects consisted of 20 healthy 10-14-year-old girls and boys. Elderly subjects consisted of 40 70-86-year-old healthy and active females and males. Continuous responses of blood pressure and heart rate were recorded by Finapres. A pulse contour algorithm applied to the finger arterial pressure waveform was used to assess stroke volume responses. 2. During the first 30s (initial phase), an almost identical drop in mean blood pressure was found in both age groups (young, 16 +/- 10 mmHg; old, 17 +/- 10 mmHg), but the initial heart rate increase was attenuated in the elderly subjects (young, 29 +/- 7 beats/min; old, 17 +/- 7 beats/min). 3. During the period from 30 s to 10 min of standing, mean blood pressure increased from 96 +/- 12 to 106 +/- 12 mmHg in the elderly subjects compared with almost no change in the young subjects (from 82 +/- 8 to 84 +/- 7 mmHg). In the elderly subjects a progressive increase in total peripheral resistance (from 114 +/- 14% to 146 +/- 29%) was found, compared with an initial rapid increase in total peripheral resistance (126 +/- 18% after 30 s) with no further change during prolonged standing (124 +/- 17% after 10 min) in the young subjects. In this age group the decrease in stroke volume and the increase in heart rate after 10 min of standing were large (young, -37 +/- 11% and 27 +/- 11 beats/min; old, -31 +/- 9% and 7 +/- 6 beats/min, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

[Increased risk of heart and vascular diseases in fisherman from Urk]. / Vergroot risico van hart- en vaatziekten bij Urker vissers.

UNLABELLED: In order to assess physicians' preconceived ideas about unhealthy lifestyle of North Sea fishermen from Urk, the prevalence of five important risk factors for cardiovascular disease: hypertension, hypercholesterolaemia, smoking, obesity and diabetes mellitus was determined in a cross-sectional study in this population. In addition, the use of the Primetest device, a newly developed desk top analyser, was evaluated. Out of 646 people invited at the community centre at Urk, Flevoland, 384 (59%) fishermen were investigated using Primetest, which contains an electronic sphygmomanometer and colometrically determines total cholesterol and glucose levels. 87 laboratory determinations (with HDL-cholesterol and triglyceride determinations) were used when Primetest cholesterol determination proved insufficiently reliable. Male cardiovascular mortality in Urk was also compared with mortality in the Netherlands. Hypertension prevalence (last of six readings) corresponded with that of the nearby town of Lelystad, 6% and 8% respectively. The average total:HDL-cholesterol ratio was not higher than recent values from elsewhere in the Netherlands. Fifty per cent of the fishermen had a high risk (ratio greater than 4.5). Of these, 18% had hypertriglyceridaemia (greater than or equal to 2.3 mmol/l). Smoking rates were very high (58%) and 60% had moderate to severe obesity (Body Mass Index greater than or equal to 26 kg/m2). 2% had diabetes mellitus, corresponding with the prevalence in the Netherlands. Absolute and proportional male cardiovascular mortality in Urk did not differ from the Netherlands. CONCLUSION: two risk factors had a high prevalence among Urk fishermen. Blood pressure measurements and glucose determination with Primetest are simple and reliable. For technical reasons reliable cholesterol determination was not yet possible.

Initial circulatory responses to changes in posture: influence of the angle and speed of tilt.

To assess if changes in the angle or speed of tilt could account for the differences between the initial (first 30 s) circulatory responses induced by active and passive changes in posture, as found in previous studies, we investigated the initial heart rate and blood pressure responses induced by stand up from supine and various head-up tilt manoeuvres in 12 healthy, male subjects. Comparison was made between 70 degrees head-up tilt in 3 s, 90 degrees head-up tilt also in 3 s and 70 degrees head-up tilt in 1.5 s, using an automatic pneumatic-driven tilt table with foot support. It was found that the initial heart rate and blood pressure responses induced by the three tilt manoeuvres were almost identical in time course and amplitude, but significantly different from those induced by stand up. The results of this study prove that regardless of the angle and speed of tilt, the initial circulatory responses induced by passive changes in posture are essentially different from the responses induced by active changes in posture.

Effects of cuff inflation on self-recorded blood pressure.

Changes in continuously recorded 'Finapres' finger blood pressure in ten normotensive and seven hypertensive subjects induced by self-inflation of the cuff or just wearing the inflated cuff were studied. Inflating the cuff caused an instantaneous rise in systolic blood pressure of 13 and 12 mm Hg (hypertensive and normotensive subjects, respectively). Wearing the inflated cuff did not change blood pressure. Thus the rise in pressure was related to the muscular activity required for cuff inflation. Systolic blood pressure took on average 7 s and at most 21 s to return to baseline level after stopping cuff inflation. Since first Korotkoff sounds may already be heard after 10-15 s when following recommended procedures, self-recorded systolic blood pressure may be recorded as too high when subjects inflate their cuff at too low a pressure or deflate it too fast.

Inflating one's own cuff does not increase self-recorded blood pressure.

To determine whether the muscular activity required to inflate a blood pressure cuff for self-recording influences the blood pressure at the instant of the subsequent measurement, finger blood pressure was recorded continuously during cuff inflation. Ten normotensive and seven untreated hypertensive subjects used their dominant hands to inflate, in 5 s, an occluding cuff on the same arm up to 200 mmHg. Blood pressure in the middle finger of the other arm was measured continuously by the Finapres device. Korotkoff sounds were determined by a microphone in the arm cuff, and the speed of deflation was kept constant by the investigator at 2-3 mmHg/s. Systolic pressure rose at the onset of inflation, with an average peak of 13 +/- 6 (s.d.) and 12 +/- 8 mmHg above baseline in the normotensive and hypertensive subjects, respectively. Five seconds after the onset of deflation both systolic and diastolic pressures in both groups had returned to baseline levels. Thus, self-inflation of a blood pressure cuff allows a valid measurement of blood pressure provided the recommended guidelines are strictly followed.