Chest pain early after percutaneous coronary intervention: incidence and relation to ECG changes, cardiac enzymes and follow-up events

To investigate the incidence of chest pain early after percutaneous coronary interventions and its correlation with ECG changes, cardiac enzymes, clinical and procedural variables and follow-up events, we prospectively studied 199 patients (84% male; mean age, 60.1 +/- 9.4 years) after primary successful percutaneous coronary interventions (21% PTCA; 79% additional stent implantation). During the first 16 hours following the intervention, the occurrence of chest pain was noted, ECGs were recorded and serial measurements of cardiac enzymes were performed. Seventy-six patients (38%) with elevated enzyme levels at time 0 were excluded. A clinical follow-up was obtained at 6 months. Forty patients (32.5%) experienced chest pain; new ECG changes were detected in 3 (2.5%). The mean levels of all enzymes were significantly higher in patients with chest pain 16 hours after the intervention. In patients with chest pain versus those without, CK-MB mass and troponin I levels higher than twice the upper normal limit were seen in 43.6% versus 11.0% (p < 0.0001) and 45.0% versus 17.3% (p < 0.002), respectively. Elevated troponin I (< 0.004) and CK-MB mass (< 0.04) as well as presumed ischemic chest pain (< 0.03) could be identified as risk factors for recurrent chest pain during follow-up. In conclusion, chest pain was common early after percutaneous coronary interventions and correlated with elevated cardiac enzymes, suggesting peri-interventional myocardial necrosis. Elevated levels of CK-MB mass and troponin I, as well as presumed ischemic chest pain, were associated with recurrent chest pain during follow-up.

Mental stress increases right heart afterload in severe pulmonary hypertension

Little is known about mental stress effects on the pulmonary circulation in health and disease. The current study was conducted to investigate whether pulmonary artery pressure (PAP) and pulmonary vascular resistance (PVR) would further increase during standardized mental stress testing in patients with severe pulmonary hypertension. The study was a prospective analysis of seven patients (average age: 40 years, range from 21 to 56 years) with severe pulmonary hypertension (primary: n = 4, secondary forms: n = 3; resting mean pulmonary artery pressure ranged between 48 and 65 mmHg). Right heart catheterization for the determination of PAP, pulmonary capillary wedge pressure (PCW) and cardiac output (CO) was clinically indicated (diagnostic workup, acute drug testing). Patients accomplished a standardized 10 min mental stress test (computer based, adaptive complex reaction-time task). Pulmonary haemodynamics during stress were compared to resting baseline. During mental stress mean PAP (+/- SEM) increased by 9.4 +/- 2.1 mmHg (P < 0.005). Pulmonary vascular resistance increased by 149 +/- 25 dyne s cm-5 (P < 0.001). Stroke volume decreased by 6.6 +/- 2.2 ml (P < 0.03). The data show that moderate mental stress increases right heart afterload in patients with severe pulmonary hypertension owing to elevation of PVR.

Pressure support and pressure assist/control: are there differences? An evaluation of the newest intensive care unit ventilators

BACKGROUND

Pressure support (PS) has been widely studied in both patients and lung models, but there is little data available evaluating pressure assist/control (P A/C, frequently referred to as PCV) and no data comparing the operational capabilities of these two modes on the newest generation of ICU ventilators. We used a spontaneously breathing lung model to evaluate the response of the following new generation ventilators to varying inspiratory demand in both PS and P A/C: Bear 1000, Dräger Evita 4, Hamilton Galileo, Nellcor Puritan-Bennett 840 and 740, Siemens Servo 300A, TBird AVS.

METHODS

A bellows-in-a-box lung model was set at a respiratory rate of 12 breaths/min, inspiratory time of 1.0 second, and peak inspiratory flows (modified square wave) of 40, 60, and 80 L/min. Each ventilator was set at three levels of PS and P A/C: 10, 15, and 20 cm H(2)O. On all ventilators, flow-triggering was set as sensitive as possible without causing self-triggering.

RESULTS

Trigger pressure, trigger pressure-time product, inspiratory trigger time delay, ventilator-delivered peak flow, inspiratory area as a percent of the ideal inspiratory area, expiratory time delay, supraplateau expiratory pressure change, and expiratory area all varied among ventilators and at different lung model peak flows (p < 0.01 and >/= 10% difference). However, PS and P A/C on a given ventilator only differed with regard to expiratory variables (p < 0. 01 and >/= 10% difference).

CONCLUSION

In a given ventilator little difference exists in gas delivery and response variables between PS and P A/C, but performance differences do exist among the ventilators evaluated. Ventilator performance is diminished at high lung model peak flows and low pressure settings. (I)), whereas PS gives control over ending inspiration to the patient. What has not been clearly defined is the gas delivery and ventilator response differences, if any, between these two (PS and P A/C) pressure targeted assist modes. Most new generation intensive care unit (ICU) ventilators provide both pressure support (PS) and pressure assist/control (P A/C) ventilation.19,20 The specific operational difference between these two modes is the mechanism that transitions inspiration to expiration. With pressure support the primary mechanism is a decrease in peak inspiratory flow to a predetermined level, whereas with P A/C mechanical T(I) is preset.19,20 We compared the operation of seven of the newest generation ICU ventilators in a spontaneously breathing lung model in both PS and P A/C. We hypothesized that there would be no difference in variables assessed between PS and P A/C except for the transition to expiration and that there would be no difference in response among ventilators evaluated.

Disordered calcium homeostasis of sepsis: association with calcitonin precursors

BACKGROUND

Hypocalcemia and increased serum levels of calcitonin precursors are common in critically ill patients, especially in those with sepsis. We investigated calcium homeostasis in such patients.

PATIENTS AND METHODS

Serum concentrations of total and ionized calcium and known factors influencing or reflecting calcium homeostasis were measured in 101 consecutive patients of a medical intensive care unit. Calcitonin precursor levels were determined using a highly sensitive radioimmunoassay.

RESULTS

Critical illness per se was associated with decreased serum total and ionized calcium levels, which correlated with the severity of the underlying disease as measured by the APACHE II score. In addition, total and ionized hypocalcemia was more pronounced with increasing severity of infection (P < 0.02), and occurred in parallel with a marked increase of calcitonin precursors (P < 0.001). Mature calcitonin levels, however, remained normal. Changes of serum ionized calcium concentrations from admission to discharge correlated significantly with changes in the serum calcitonin precursor concentration (r2 = - 0.14, P < 0.001). Circulating vitamin D levels, parathyroid hormone levels and other markers reflecting calcium homeostasis did not correlate with the severity of infection.

CONCLUSIONS

In critically ill patients with sepsis, markedly elevated circulating calcitonin precursors might play a role in the development of the pronounced hypocalcemia. The specific calcitonin precursor(s) responsible for this effect and the pathophysiological mechanism remain to be elucidated.

Calcitonin precursors are reliable markers of sepsis in a medical intensive care unit

OBJECTIVE

The diagnosis of infection in critically ill patients is challenging because traditional markers of infection are often misleading. For example, serum concentrations of calcitonin precursors are increased in patients with infections. However, their predictive accuracy for the diagnosis of sepsis in unselected patients in a medical intensive care unit (ICU) is unknown. Therefore, we compared the usefulness of serum concentrations of calcitonin precursors, C-reactive protein, interleukin-6, and lactate for the diagnosis of sepsis in consecutive patients suffering from a broad range of diseases with an anticipated stay of > or =24 hrs in a medical ICU.

DESIGN

Prospective cohort study.

SETTING

Medical intensive care unit in a university medical center.

PATIENTS

101 consecutive critically ill patients.

INTERVENTION

None.

MEASUREMENTS AND MAIN RESULTS

Blood samples were collected at various time points during the course of the disease. Systemic inflammatory response syndrome, sepsis, severe sepsis, and septic shock were diagnosed according to standardized criteria, and patients were reclassified daily without prior knowledge of the serum concentrations of calcitonin precursors or interleukin-6. At admission, 99% of the patients had systemic inflammatory response syndrome, 53% had sepsis, and 5% developed sepsis during their stay in the ICU. Calcitonin precursors, C-reactive protein, interleukin-6, and lactate levels increased with the severity of infection (p < .01, one-way analysis of variance). In a receiver operating characteristic curve analysis, calcitonin precursors were found to be the most reliable laboratory variable for the diagnosis of sepsis as compared with C-reactive protein, interleukin-6, and lactate (p < .01, for each comparison). Calcitonin precursor concentrations of >1 ng/mL had sensitivity of 89% and specificity of 94% for the diagnosis of sepsis. High serum concentrations of calcitonin precursors were associated with poor prognosis (p = .01).

CONCLUSIONS

In a medical ICU, serum calcitonin precursor concentrations are more sensitive and are specific markers of sepsis as compared with serum C-reactive protein, interleukin-6, and lactate levels.

[Value of German Hospital Diagnosis Statistics in epidemiology-- an analysis with subarachnoid hemorrhage as an example]

Due to the Hospital Statistics Regulations of the 10th April 1990, the German Hospital Diagnosis Statistics were introduced in 1993 with the intention to serve as a database of health care decisions. This purpose requires a high-quality collection of epidemiologically relevant data. From 1993 to 1996 we analysed the datasets obtainable for subarachnoid haemorrhage which is coded with ICD 430. A subset concerning the data of 1996 and the Saarland region was compared to the data of the Saarland medical school at Homburg/Saar. Cases treated in the neurosurgical department were critically reviewed. About 20% of the cases coded with ICD 430 showed no subarachnoid haemorrhage. On the other hand, again about 20% of subarachnoid haemorrhage cases were not coded with ICD 430. The statistics comprise duplicates due to transfers between hospitals. The calculation of incidence is not possible because new bleeding cases cannot be outlined. In the present form the German Hospital Diagnosis Statistics are not suitable as a reliable base of health care decisions. This is partly caused by the inadequacy of the ICD-classification but, also, by the criteria for collecting data. We propose several modifications which can improve data quality in order to meet the intended requirements.

Effect of midazolam on transfer function between beat-to-beat arterial pressure and inter-beat interval length

Arterial pressure (AP) and inter-beat interval (IBI) length are under autonomic nervous system control. The control mechanisms can be investigated by transfer function analysis. It is not known if this type of analysis may be helpful in monitoring depth of sedation. In an open-label, uncontrolled investigation, the effect of midazolam on the transfer function between AP and IBI, and on spectral indices of AP and heart rate (HR) variability (APV, HRV) were assessed in the absence and presence of the benzodiazepine antagonist flumazenil. We studied 11 healthy male volunteers. After an initial control period of 60 min, we studied three consecutive periods, each of 60 min duration, with progressively increasing concentrations of midazolam (0.02, 0.06, 0.14 mg kg-1 h-1). A final 60-min period during administration of flumazenil 0.004 mg kg-1 h-1 and while the agonist was still present was also studied. To confirm midazolam-induced central nervous system effects, electroencephalography was performed and Ramsay sedation scores were determined. With increasing dose of midazolam, the high frequency (0.15-0.4 Hz) component of the transfer function between AP and IBI decreased progressively (mean 26.5 (SEM 3.7), 19.2 (2.9), 12.8 (1.7), 8.4 (1.6) ms mm Hg-1). This effect was antagonized by flumazenil (21.5 (3.2) ms mm Hg-1). Other indices (e.g. HRV, APV) did not reveal such a clear response to midazolam dose and flumazenil application. Thus in healthy male volunteers, the transfer function between AP and IBI in the parasympathetically dominated high frequency range varies according to benzodiazepine agonism and antagonism. This finding has potential implications for monitoring the effects of benzodiazepines.

[Effect of spongiosa density on load bearing of the lumbar spine.A finite element analysis]

OBJECTIVE

Different parts of the human spine have to accomplish different functions. But little is known about the exact distribution of forces within the spine and whether this is influenced by bone quality. The purpose of this study was to predict fields and extent of greatest load in compression in a human lumbar spine motion segment using a finite element model.

METHODS

A three dimensional isotrophic finite element model was generated using the software ANSYS 5.4. Spinal loading was performed in axial compression (600 N). The model was validated by biomechanical analysis using 12 human spinal segments that were loaded with the same forces. Prediction was done with different E-modulus for cancellous bone, representing a wide range of bone quality between osteoporotic and strong bone quality.

RESULTS

Load-sharing was influenced by bone quality: the weaker bone quality is, the higher is the extent of load that is passed through the posterior part of the spine.

CONCLUSION

This finite element model predicts that load-sharing in a lumbar spine segment with decreased bone mineral density is different from that in healthy segments. A decrease of bone mineral density is resulting in an increase of load that is passed through the posterior part of the lumbar spine. Keeping in mind the simplifications of this model, the results may influence surgical treatment of patients suffering from osteoporosis or osteolytic destructions of the lumbar spine.

Auditory and electroencephalographic effects of midazolam and alpha-hydroxy-midazolam in healthy subjects

AIMS

Whereas cortical EEG effects of benzodiazepines are well characterized, information about benzodiazepine effects in other areas of the central nervous system is sparse. This study investigated the action of midazolam and its active metabolite alpha-hydroxy-midazolam on different parts of the auditory pathway in six healthy volunteers in a randomized, double-blind, three-way cross-over study.

METHODS

Acoustically evoked short (SLP) and middle (MLP) latency potentials, transitory evoked otoacoustic emissions (TEOAE), and EEG power spectra were analysed after short i. v. injections of placebo, or 0.15 mg kg-1 midazolam, or alpha-hydroxy-midazolam, respectively.

RESULTS

All subjects fell asleep during the 4 min infusion of active drug. SLP showed a significant transient increase of Jewett wave V 10 min after injection for midazolam and alpha-hydroxy-midazolam while the latency of wave I was unchanged. Both benzodiazepines induced a marked and long-lasting MLP amplitude decrease for 240 min with slow recovery over the following 360 min. No changes of TEOAE were observed. In agreement with earlier reports, increases in EEG beta activity and decreases in alpha activity were observed after administration of either drug.

CONCLUSIONS

Systemically administered benzodiazepines modulate the auditory pathway above the level of the cochlea. While SLP changes were closely associated with sedation and high plasma benzodiazepine concentrations, MLP effects persisted for hours after sedation even at low benzodiazepine plasma levels. Evoked potentials may therefore be more sensitive than EEG as a tool to monitor benzodiazepine effects.

Additional inspiratory work of breathing imposed by tracheostomy tubes and non-ideal ventilator properties in critically ill patients

OBJECTIVE

To determine the tracheostomy tube-related additional work of breathing (WOBadd) in critically ill patients and to show its reduction by different ventilatory modes.

DESIGN

Prospective, clinical study.

SETTING

Medical ICU of a university teaching hospital.

INTERVENTION

Standard tracheostomy due to prolonged respiratory failure.

MEASUREMENTS AND RESULTS

Ten tracheostomized, spontaneously breathing patients were investigated. As the tube resistance depends on gas flow, patients were subdivided according to minute ventilation into a low ventilation group (= 10 l/min; n = 5) and a high ventilation group (> 10 l/min; n = 5). The WOBadd due to tube resistance and non-ideal ventilator properties was calculated on the basis of the tracheal pressure measured. Ventilatory modes investigated were: continuous positive airway pressure (CPAP), inspiratory pressure support (IPS) of 5, 10, and 15 cm H2O above PEEP, and automatic tube compensation (ATC). In the low ventilation group, WOBadd during CPAP was 0.382+/-0.106 J/l. It was reduced to below 15% of that value by ATC or IPS more than 5 cm H2O. In the high ventilation group WOBadd during CPAP increased to 0.908+/-0.142 J/l. In this group, however, only ATC was able to reduce WOBadd below 15% of the value observed in the CPAP mode.

CONCLUSIONS

The results indicate that, depending on respiratory flow rate, (1) tracheostomy tubes can cause a considerable amount of WOBadd, and (2) ATC, in contrast to IPS, is a suitable mode to compensate for WOBadd at any ventilatory effort of the patient.

Midazolam effects on prepulse inhibition of the acoustic blink reflex

AIMS

The eye-blink response following sudden acoustic noise bursts is part of the startle reflex. The magnitude of the startle response can be attenuated by presentation of a weak stimulus before the 'startle-eliciting' stimulus (prepulse inhibition, PPI). PPI is a stable finding in awake humans but may be altered by anaesthetic drugs. We investigated whether the application of benzodiazepines altered the magnitude of PPI in healthy male volunteers.

METHODS

In an open-label noncontrolled investigation, the effect of the benzodiazepine agonist midazolam on PPI was assessed in the absence and presence of the antagonist flumazenil. After an initial control period of 60 min three consecutive periods, each of 60 min, with progressively increasing concentrations of midazolam were studied (0. 02, 0.06, 0.14 mg kg-1 h-1 ). A final 60 min period during the administration of flumazenil (0.004 mg kg-1 h-1 ) and while the agonist was still present was also studied. Drug was administered intravenuously as a combination of bolus, 50% of total dose and continuous infusion over the 60 min period. Electromyographic (EMG) response of the right orbicularis oculi muscle was used to assess the startle response to noise bursts of 50 ms duration (95 dB(A)). Noise bursts were randomly preceded by nonstartling prepulses (800 Hz sinus, 50 ms duration, 65 dB(A), prepulse to noise interval 120 ms). The magnitude of PPI was calculated by dividing the EMG response to nonprepulsed stimuli by the response to prepulsed stimuli for each individual and period. Eleven subjects participated in the study, two of them were excluded from the statistical analysis because startle responses could not be reliably elicited (final sample size n=9).

RESULTS

The magnitude of PPI was inversely related to the concentration of midazolam. This relationship was described by a sigmoidal Emax model, giving an Emax of 0.65+/-0.13, an ED50 of 33.9+/-10.9 ng ml-1 and gamma of 3.5+/-1.0. During infusion of flumazenil and in the presence of midazolam, the magnitude of PPI increased by 0.11 (95% CI, 0-0.22, P</=0.04), which is consistent with its mode of action as a benzodiazepine antagonist.

CONCLUSIONS

In healthy male volunteers the magnitude of PPI varies according to agonism and antagonism of benzodiazepine receptors, suggesting that the assessment of PPI may be potentially useful to monitor the sedative effect of benzodiazepines in the clinical setting.

Effect of beta blockade with and without sympathomimetic activity (ISA) on sympathovagal balance and baroreflex sensitivity

Beta blockers increase heart rate variability (HRV) and improve survival in coronary artery disease (CAD). The benefit of beta blockers with intrinsic sympathomimetic activity (ISA) in CAD still remains a matter of debate, and their effect on HRV has not yet been investigated. Therefore, we measured HRV, systolic blood pressure variability (BPV) and baroreflex sensitivity (BRS) under propranolol (PROP, without ISA, 160 mg q.d.), pindolol (PIN, with potent ISA, 15 mg q.d.) and placebo (PLA, q.d.) in 30 healthy subjects, aged 21-39 years, during controlled frequency breathing (0.30 Hz) in supine and tilt positions. PROP increased HRV in the high-frequency (0.15-0.40 Hz) band (PROP 7.4 +/- 1.0; PLA 6.9 +/- 1.4; PIN 6.8 +/- 1.0 ln MI2; P = 0.003), decreased BPV in the low-frequency band (at 0.1 Hz, Mayer waves) (PROP 0.6 +/- 0.7; PLA 1.3 +/- 1.1; PIN 1.2 +/- 1.2 ln mmHg2; P = 0.001) and enhanced BRS (PROP 14.6 +/- 9.5; PLA 8.0 +/- 6.8; PIN 8.7 +/- 6.8 ms mmHg-1; P = 0.001) in the supine position. After passive tilt, PROP decreased HRV in the low-frequency band (PROP 6.1 +/- 0.9; PLA 6.5 +/- 1.1; PIN 6.9 +/- 0.7 ln MI2; P < 0.001) and decreased Mayer waves (PROP 1.8 +/- 0.8; PLA 2.4 +/- 1.0; PIN 2.7 +/- 0.8 ln mm Hg2; P < 0.001). PIN increased the low-frequency HRV response, which is induced by passive tilt (PIN + 0.9 +/- 1.0; PLA + 0.3 +/- 1.3, PROP + 0.3 +/- 1.0 ln MI2; P = 0.026). Our results prove that beta-adrenergic blockade with potent ISA does not increase HRV, has no beneficial effect on autonomic balance and even exaggerates sympathetic responses to passive tilt.

Reversible cerebral ischemia in patients with pheochromocytoma

Cerebral ischemia and symptoms of stroke can occur as a rare manifestation in patients with pheochromocytoma. We describe a 45-year-old woman who was admitted because of a right-sided hemiparesis due to an ischemic lesion in the left hypothalamus. The clinical diagnosis of a pheochromocytoma was proven by highly elevated urinary catecholamines and confirmed histologically after operation. The successful removal of the tumor led to the almost complete recovery of the neurological deficiencies. It is of vital importance to know this atypical presentation of pheochromocytoma. The diagnosis of pheochromocytoma should be suspected in patients with focal cerebral symptoms, particularly in the presence of intermittent hypertension or other paroxysmal symptoms suggestive of pheochromocytoma.

Expiratory phase and volume-adjusted tracheal gas insufflation: a lung model study

OBJECTIVE

To evaluate in a lung model the effects of expiratory-phase tracheal gas insufflation (expiratory-phase TGI) with both volume and pressure control ventilation, and tidal volume-adjusted continuous flow TGI (volume-adjusted TGI) on system pressures and volumes.

DESIGN

Single-compartment lung model.

SETTING

Research laboratory in a university medical center.

INTERVENTIONS

Expiratory-phase TGI was established, using a solenoid valve activated by the ventilator. Volume-adjusted TGI was applied by reducing tidal volume (VT) by the product of TGI flow and inspiratory time. Ventilation was provided with pressure control of 20 cm H2O or volume control ventilation with VT similar to that with pressure control ventilation. A rate of 15 breaths/min and positive end-expiratory pressure (PEEP) of 10 cm H2O were used throughout. Inspiratory time periods of 1.0, 1.5, 2.0, and 2.5 secs were used with TGI flows of 0, 4, 8, and 12 L/min. Lung model compliance (mL/cm H2O) and resistance (cm H2O/L/sec) combinations of 20/20, 20/5, and 50/20 were used.

MEASUREMENTS AND MAIN RESULTS

In expiratory-phase TGI with pressure control ventilation, peak alveolar pressure remained constant, PEEP increased (p < .01) and VT decreased (p < .01). In expiratory-phase TGI with volume control ventilation and volume-adjusted TGI, there were significant increases in peak alveolar pressure and PEEP (p < .01). Readjustment of VT in volume-adjusted TGI was impossible with longer inspiratory time (> or = 2 secs) and higher TGI flows (> or = 8 L/min).

CONCLUSIONS

The marked increases in system pressures and volumes observed with continuous-flow TGI can be avoided with expiratory-phase TGI and volume-adjusted TGI.

[Intensive monitoring of patients with acute cerebral ischemia within the scope of a coordinated stroke treatment concept: initial experiences]

QUESTIONS UNDER STUDY

It has been shown that the prognosis of patients with stroke can be improved by specialized stroke units. Whether any additional benefit can be achieved by use of intensive care resources is unknown. Therefore, it was the purpose of this study to analyze our first experience of management of patients with acute ischaemic stroke in an intensive care unit, as part of a newly implemented coordinated stroke concept.

METHODS

A consecutive series of 88 patients with acute ischemic stroke (age 64.4 +/- 14.2 years, 28% females) hospitalized in a medical intensive care unit according to predefined criteria formed the study population. The goals were to monitor vital functions, to complete diagnostic studies in timely fashion and to prevent and treat complications.

RESULTS

The patients were hospitalized in the intensive care unit for a mean period of 34.4 +/- 19.5 hours. Relevant pathologic findings included systolic hypertension > 220 mm Hg in 5% and permanent or intermittent relative systolic hypotension < 150 mm Hg in 25% and 98% of patients respectively. One patient (1%) died during the stay. Additional diagnostic studies were performed more often in patients with progressive or fluctuating symptoms (100% of patients in each group) than in those with improving or stable symptoms (50% of patients in each group). Fourteen percent of patients were treated for hypertension and 30% for hypotension. Antithrombotic therapy with aspirin was started in 34%, prophylaxis for venous thrombosis with low dose heparin in 39% and systemic anticoagulation in 40% of patients respectively. No cardiac or pulmonary complications requiring treatment were observed and no specific therapies for neurologic complications were utilized. At the time of discharge from the intensive care unit, 88% of patients showed improved or stable neurologic findings.

CONCLUSIONS

In the present analysis, an unexpectedly high incidence of relative arterial hypotension was observed in patients hospitalized in an intensive care unit for acute ischaemic stroke. Therapeutic measures were restricted mainly to blood pressure control and anticoagulation/antithrombotic treatment. Specific therapies for neurologic complications or interventions requiring the resources of an intensive care unit were not used. Whether defined patient groups with ischaemic stroke will benefit from specific treatment in an intensive care unit needs to be tested by controlled, randomized studies.

Treatment with N-acetylcysteine during acute respiratory distress syndrome: a randomized, double-blind, placebo-controlled clinical study

PURPOSE

Intravenous N-acetylcysteine (NAC) has been reported to improve systemic oxygenation and reduce the need for ventilatory support in patients with an acute lung injury. In the more serious form, namely established adult respiratory distress syndrome (ARDS) (PaO2/FIO2 < or = 200 mm Hg), we tested the hypothesis that treatment with intravenous NAC may be beneficial.

MATERIALS AND METHODS

Respiratory dysfunction was graded daily according to the need for mechanical ventilation and FIO2 and to the evolution of the lung injury score (LIS) and the PaO2/FIO2 ratio in 42 patients with established ARDS receiving either NAC 190 mg/kg/day or placebo as a continuous intravenous infusion over the first 3 days of their clinical course.

RESULTS

NAC and placebo groups (22 and 20 patients, respectively) were comparable for demographic characteristics, ARDS categories, severity of illness (simplified acute physiology score [SAPS II]) LIS and PaO2/FIO2 ratio. Mortality rate was 32% for the NAC and 25% for the placebo group (difference not significant). At admission (day 1), 91% of patients in the NAC and 95% in the placebo group required ventilatory support; at days 2, 3, 5, and 7 after admission, the percentage of patients receiving ventilatory support was not significantly reduced for both groups in comparison with day 1. Moreover, there were no differences between the two groups at the same observation days. In both groups, the FIO2 was significantly lower and the PaO2/FIO2 ratio was significantly higher than the initial values during the evolution (FiO2 at day 3, P < .01 for NAC and P < .05 for placebo; PaO2/FIO2 at day 3: P < .01 for NAC and P < .02 for placebo), but this improvement was similar for both groups and, moreover, the between-group comparison was never significantly different at the various collection days. The LIS decreased significantly in NAC group between days 1 and 3 (2.23 +/- 0.62 v 1.76 +/- 0.17; P < .05), whereas no changes were observed in the placebo group; at day 5, there was a significant difference between the two groups (1.53 +/- 0.21 for the NAC v 2.15 +/- 0.19 for the placebo group; P < .05). In the prevalent sepsis category (10 patients in the NAC and 9 in the placebo group), the mortality rate, the need of ventilatory support, the intensive care unit stay, and the PaO2/FIO2 evolution did not differ significantly in both subgroups.

CONCLUSIONS

In this relatively small group of patients presenting with an established ARDS subsequent to a variety of underlying diseases, intravenous NAC treatment during 72 hours neither improved systemic oxygenation nor reduced the need for ventilatory support.

Delivery systems for inhaled nitric oxide

From a practical standpoint, technical issues related to NO delivery are as important as therapeutic issues. The benefits can be appreciated only if a reliable delivery system is used. Further, hazards and toxicity may be more problematic with an unreliable delivery system. It is incumbent on clinicians using inhaled NO to ensure that the delivery system is safe and reliable.

Synchronous oscillatory activity in sensory systems: new vistas on mechanisms

The origin and nature, as well as the functional role, of synchronous oscillatory activity in the cortex are among the major unresolved issues in systems neurobiology. Recent advances in understanding the mechanisms underlying oscillations include the description of intrinsically bursting pyramidal cells in striate cortex in vivo and the discovery of inhibitory interneurons that fire spike doublets to induce synchrony. The behavioral consequences of coordinated activity in cortical neurons remain poorly understood.

Assessment of errors when expiratory condensate PCO2 is used as a proxy for mixed expired PCO2 during mechanical ventilation

OBJECTIVES

We designed a series of experiments to determine whether expiratory water condensate (PconCO2) can be used as a proxy for mixed expired gas collection.

METHODS

In 18 adult mechanically ventilated patients with ARDS (40 samples), simultaneous collections of arterial blood, expiratory water trap condensate, mixed expired gas, and minute ventilation were used to calculate VCO2 and VD/VT. To assess the effect of temperature, a constant gas flow (PCO2 10-30 mm Hg) was bubbled through water at temperatures of 19.5-37 degrees C. Gas and water samples were collected, immediately analyzed for PCO2, and a temperature correction factor was calculated. A lung model was constructed using a 5 L anesthesia bag connected to a mechanical ventilator with a heated humidifier. Temperature at the Y-piece was set to approximately 37 degrees C and CO2 was injected into the bag to establish an end-tidal PCO2 of 20-70 mm Hg. After equilibration, condensate was collected, PCO2 was measured, and the temperature-corrected PCO2 was compared to PECO2. The capnogram at points along the expiratory limb circuit was used to evaluate gas mixing.

RESULTS

There was an over-estimation of PECO2 by PconCO2 (p < 0.001) for the patient data, resulting in an underestimation of VD/VT (p < 0.001) and an overestimation of VCO2 (p < 0.001). The temperature correction factor for PCO2 in water was -0.010 (about half of the factor used for whole blood). The bias between temperature-corrected PconCO2 and PECO2 was 0.3 +/- 3.2 mm Hg in the lung model. Mixing in the expiratory limb was poor, as evaluated by the capnogram.

CONCLUSIONS

Even with temperature correction, we failed to precisely predict PECO2 from PconCO2. For measurement of VD/VT and VCO2, we do not recommend methods that use PconCO2.

Assessment of depth of midazolam sedation using objective parameters

OBJECTIVE

To determine the relationship between the clinically evaluated depth of midazolam-induced sedation and the cardiac beat-to-beat variability (RR variability) in ICU patients in the intensive care unit (ICU).

DESIGN

Prospective study.

SETTING

ICU of a university hospital.

PATIENTS

20 consecutive patients studied during weaning from mechanical ventilation and withdrawal of midazolam-induced sedation.

MEASUREMENTS AND RESULTS

After clinical evaluation of depth of sedation according to the Ramsay sedation score, the RR variability over 512 RR intervals and predominant respiratory rate were measured. The power spectrum of RR variability was calculated by a fast Fourier transformation and the resulting total frequency band (0.016-0.35 Hz) was subdivided into a very low, a low, and a high frequency band. Stepwise multiple regression analysis in the first 10 patients (group 1) showed a significant relationship between depth of sedation and measures of RR variability combined with respiratory rate (r2 = 0.59; F = 12.1; p < 0.001). The more effective sedation was, the more depressed were both RR variability and predominant respiratory rate. Mean heart rate, mean respiratory rate, median deviation of RR intervals from the mean, and the ratio between spectral power density in the high and the low frequency bands proved to be the most important predictors of the Ramsay score (+/-1 level accuracy: 87%, p < 0.001). Using this regression equation, the Ramsay score was predicted in the remaining 10 patients (group 2) with a +/-1 level of accuracy of 81% (p < 0.001).

CONCLUSION

In ICU patients, a significant correlation is found between the depth of midazolam-induced sedation as assessed by the Ramsay sedation score and RR variability, with a clinically sufficient prediction accuracy. RR variability can serve as an objective, continuously available, and non-invasive measurement to monitor midazolam-induced sedation in intubated and mechanically ventilated patients.

[Clinico-pharmacological case (4). Epileptic seizure as an unwanted drug effect on theophylline poisoning]

In spite of the better understanding of the pharmacokinetics and optimized galenics of oral theophylline formulations, therapy with this bronchodilator still bears risks because of its narrow therapeutic window combined with substantial inter- and intra-individual variability of theophylline metabolism. In particular, the comedication with a variety of drugs inhibiting theophylline metabolism requires consideration as a potential source of toxicity. Besides mild, self-limited adverse effects, potentially life-threatening toxic manifestations such as ventricular tachyarrhythmias, shock, and seizures can occur especially with high plasma concentrations. We report the case of a 72-year-old patient with chronic obstructive pulmonary disease who was admitted for surgical treatment of an ulcer of the foot. During combined therapy with theophylline and ciprofloxacin he developed signs of theophylline toxicity with a single episode of partial seizures. These symptoms rapidly improved with repetitive application of activated charcoal and sorbitol. Clinically relevant drug-drug interactions with theophylline and the role and mechanism of action of activated charcoal in intoxicated patients are discussed.

Vigabatrin dosing during haemodialysis

The antiepileptic drug vigabatrin has shown efficacy in the treatment of patients with refractory epilepsy. Unlike many other antiepileptics it is not bound to plasma protein and mainly eliminated by the kidney. Although the therapeutic and toxic serum concentration range is not clearly defined and efficacy and toxicity are not closely correlated with the dose, factors decreasing vigabatrin elimination such as advanced age or renal failure may pose risk of untoward effects. Thus far there are no dose recommendations available for patients on haemodialysis. We report on an epileptic patient who experienced severe, partially reversible renal failure as a consequence of near-drowning. In this patient serum concentrations of vigabatrin were measured repeatedly both during haemodialysis and after partial recovery of renal function. The terminal elimination half-life in this patient was 41 hours during the period of severe renal failure (creatinine clearance < 5 ml/min). As about 60% of vigabatrin was removed from the blood pool by haemodialysis in these patients the antiepileptic should be administered after dialysis. To maintain serum concentrations in the usual range and to control seizure activity only 500 mg vigabatrin every 3 days were necessary.