Comparative effects of helium-oxygen and external positive end-expiratory pressure on respiratory mechanics, gas exchange, and ventilation-perfusion relationships in mechanically ventilated patients with chronic obstructive pulmonary disease

OBJECTIVE

To compare the effects of He/O(2) and external PEEP (PEEPe) on intrinsic PEEP (PEEPi), respiratory mechanics, gas exchange, and ventilation/perfusion (V(A)/Q) in mechanically ventilated COPD patients.

DESIGN AND SETTING

Prospective, interventional study in the intensive care unit of a university hospital.

INTERVENTIONS

Ten intubated, sedated, paralyzed, mechanically ventilated COPD patients studied in the following conditions: (a) baseline settings made by clinician in charge, air/O(2), ZEEP; (b) He/O(2), ZEEP; (c) air/O(2), ZEEP; (d) air/O(2), PEEPe 80% of PEEPi. Measurements at each condition included V(A)/Q by the multiple inert gas elimination technique (MIGET).

RESULTS

PEEPi and trapped gas volume were comparably reduced by He/O(2) (4.2+/-4 vs. 7.7+/-4 cmH(2)O and 98+/-82 vs. 217+/-124 ml, respectively) and PEEPe (4.4+/-1.3 vs. 7.8+/-3.6 cmH(2)O and 120+/-107 vs. 216+/-115 ml, respectively). He/O(2) reduced inspiratory and expiratory respiratory system resistance (15.5+/-4.4 vs. 20.7+/-6.9 and 19+/-9 vs. 28.8+/-15 cmH(2)O l(-1)s(-1), respectively) and plateau pressure (13+/-4 vs. 17+/-6 cmH(2)O). PEEPe increased airway pressures, including total PEEP, and elastance. PaO(2)/FIO(2) was slightly reduced by He/O(2) (225+/-83 vs. 245+/-82) without significant V(A)/Q change.

CONCLUSIONS

He/O(2) and PEEPe comparably reduced PEEPi and trapped gas volume. However, He/O(2) decreased airway resistance and intrathoracic pressures, at a small cost in arterial oxygenation. He/O(2) could offer an attractive option in COPD patients with PEEPi/dynamic hyperinflation.

Respiratory muscle workload in intubated, spontaneously breathing patients without COPD: pressure support vs proportional assist ventilation

OBJECTIVE

To compare the respiratory muscle workload associated with pressure support ventilation (PSV) and proportional assist ventilation (PAV) in intubated and spontaneously breathing patients without COPD.

DESIGN AND SETTING

Prospective study, intensive care unit university hospital.

INTERVENTIONS

Twenty intubated patients, during early weaning, PSV settings made by clinician in charge of the patient, and two levels of PAV, set to counterbalance 80% (PAV 80) and 50% (PAV 50) of both elastic and resistive loads, respectively. The patients were ventilated in the following order: 1) PSV; 2) PAV 50 or PAV 80; 3) PSV; 4) PAV 80 or PAV 50; 5) PSV. PSV settings were kept constant.

MEASUREMENTS

Arterial blood gases, breathing pattern and respiratory effort parameters at the end of each of the five steps.

MAIN RESULTS

PSV and PAV 80 had the same effects on work of breathing (WOB). The pressure-time product (PTP) was significantly higher during PAV 80 than during PSV (90+/-76 and 61+/-56 cmH(2)O.s.min(-1), respectively, P <0.05). Tidal volume was comparable, albeit more variable with PAV 80 than with PSV (variation coefficient, 43% vs 25%, respectively, P <0.05). PAV 50 entailed a higher respiratory rate, lower tidal volume, and higher WOB and PTP than PSV and PAV 80. PaO(2)/FiO(2) and SaO(2) were lower with PAV 50 than with PSV and PAV 80.

CONCLUSION

In a group of intubated spontaneously breathing non-COPD patients, PAV 80 and PSV were associated with comparable levels WOB, whereas PTP was higher during PAV 80. PAV 50 provided insufficient respiratory assistance.

Helium-oxygen versus air-oxygen noninvasive pressure support in decompensated chronic obstructive disease: A prospective, multicenter study

OBJECTIVE

To study whether noninvasive pressure support ventilation (NIPSV) with helium/oxygen (He/oxygen), which can reduce dyspnea, PaCO2, and work of breathing more than NIPSV with air/oxygen in decompensated chronic obstructive pulmonary disease, could have beneficial consequences on outcome and hospitalization costs.

DESIGN

Prospective, randomized, multicenter study.

SETTING

Intensive care units of three tertiary care university hospitals.

PATIENTS

All patients with chronic obstructive pulmonary disease admitted to the intensive care units for NIPSV during a 24-month period.

INTERVENTIONS

Patients were randomized to NIPSV with air/oxygen or He/oxygen. NIPSV settings, number of daily trials, decision to intubate, and intensive care unit and hospital discharge criteria followed standard practice guidelines.

RESULTS

A total of 123 patients (male/female ratio, 71:52; age, 71 +/- 10 yrs, Acute Physiology and Chronic Health Evaluation II, 17 +/- 4) were included. Intubation rate (air/oxygen 20% vs. He/oxygen 13%) and length of stay in the intensive care unit (air/oxygen 6.2 +/- 5.6 vs. He/oxygen 5.1 +/- 4 days) were comparable. The post-intensive care unit hospital stay was lower with He/oxygen (air/oxygen 19 +/- 12 vs. He/oxygen 13 +/- 6 days, p < .002). Cost of NIPSV gases was higher with He/oxygen, but total hospitalization costs were lower by $3,348 per patient with He/oxygen. No complications were associated with the use of He/oxygen.

CONCLUSION

He/oxygen did not significantly reduce intubation rate or intensive care unit stay, but hospital stay was shorter and total costs were lower. He/oxygen NIPSV can be safely administered and could prove to be a cost-effective strategy.

Usefulness of helium-oxygen mixtures in the treatment of mechanically ventilated patients

The density of helium is markedly lower than that of air or any of its components, leading to a substantial decrease in airway resistance to flow when it is inhaled. In mechanically ventilated patients with obstructive airway disease, replacing the usual air-oxygen mixture with helium-oxygen has been shown to reduce dynamic hyperinflation and intrinsic positive end-expiratory pressure; to decrease lung inflation pressures, respiratory acidosis, and work of breathing; and to improve arterial blood gases. Aerosol delivery to distal airways is enhanced with helium-oxygen. Preliminary data also suggest that the use of helium-oxygen could be a valuable approach to decrease postextubation respiratory distress. However, interference with ventilator function and added costs are two major disadvantages of helium-oxygen. Hence, before its widespread use in mechanically ventilated patients can be recommended, studies are needed to determine whether these favorable short-term effects can influence patient outcome.

An improved porcine model of stable methacholine-induced bronchospasm

OBJECTIVE

To validate an animal model replicating the pathophysiological characteristics of severe induced bronchospasm observed in humans, with a high level of stability permitting measurements such as the assessment of ventilation-perfusion relationships with the multiple inert gas elimination technique.

DESIGN AND SETTING

Experimental study in an animal research laboratory.

SUBJECTS

13 piglets (age 3-4 months) were studied and 7 underwent the complete protocol

INTERVENTIONS

The animals were anesthetized and paralyzed. Mechanical ventilation was initiated in a volume-controlled mode. Ventilatory parameters were adjusted to obtain normocapnia and were maintained constant during the bronchospasm. Methacholine was administered via a synchronized nebulizer and progressively adjusted to obtain a stable twofold increase in peak inspiratory pressure.

MEASUREMENTS AND RESULTS

Cardiopulmonary physiological data including assessment of lung mechanics and measurement of ventilation-perfusion relationships were obtained before and during the bronchospasm. Peak inspiratory pressure increased from 19.7+/-2.9 to 44.4+/-7.1 cmH(2)O during the bronchospasm. The latter remained stable over 2 h. Respiratory mechanics, gas exchange, and ventilation-perfusion distribution changes typical of those observed in severe bronchospasm in humans were observed in all animals.

CONCLUSIONS

The present experimental model replicates some of the physiopathological characteristics of severe human bronchospasm, and its stability should facilitate studies of the effects of different ventilatory modes in the setting of acute severe asthma.

Position paper of the ESICM Working Group on Nutrition and Metabolism. Metabolic basis of nutrition in intensive care unit patients: ten critical questions

The metabolic changes associated with critical illness involve several pathways acting at different steps of the utilization of nutritive substrates. The understanding of the role of these pathways and of their complex regulation has led to the development of new strategies for the metabolic and nutritional management of critically ill patients, including the development of new products for nutritional support. The rationale for changing the profile of nutritional support solutions by adding novel substrates is also discussed. This review focuses on the metabolic specificities of critically ill patients and also includes an analysis of the adequacy of tools to monitor the metabolic status and the adequacy of the nutritional support.

Comparative bench study of triggering, pressurization, and cycling between the home ventilator VPAP II and three ICU ventilators

OBJECTIVE

To compare triggering, pressurization, and cycling of the home ventilator VPAP II with those of three ICU ventilators (Evita 4, Galileo, and Servo 300).

DESIGN AND SETTING

Two-compartment lung model study in a research laboratory, university hospital.

METHODS

One compartment was driven by an ICU ventilator to mimic "patient" inspiratory effort, while the other was connected to the tested ventilator. Pressure support of 10, 15, 20, and 25 cmH2O, and inspiratory efforts of 5, 10, 15, 20, and 25 cmH2O (inspiratory time 1 s) were used in normal, obstructive, and restrictive conditions. Triggering delay (Td), triggering workload, pressurization at 300 and 500 ms, and difference between the "patient's" inspiratory time and that of the ventilator were analyzed.

RESULTS

No difference was noted in triggering workload between VPAP II, Evita 4, and Galileo while Servo 300 had a lower value. Pressurization at 300 ms on Evita 4 and Servo 300 reached 75% of the ideal value, on Galileo 35%, and on VPAP II 45%. Pressurization at 500 ms on Evita 4 and Servo 300 reached 85% of the ideal value, on Galileo 50%, and on VPAP II 55%. Cycling was delayed in obstructive conditions and premature in restrictive conditions with each of the devices.

CONCLUSIONS

The VPAP II performed as well as one ICU ventilator and less well than two. Home devices for noninvasive ventilation in acute respiratory failure outside the ICU could prove attractive as they are smaller, less costly, and easier to use than ICU machines.

[Mechanism of action of antidepressants and therapeutic perspectives]

Depression is an incapacitating disease which needs appropriate treatment. This article reviews the pharmacology of antidepressant drugs and the future perspectives of treating mood disorders such as depression. The foremost theory for explaining the biological basis of depression has been the monoamine hypothesis. Depression is due to a deficiency in one or other biogenic monoamines (serotonin, 5-HT; noradrenaline, NA; dopamine, DA). Antidepressant drugs are therefore classified according to their ability to improve monoaminergic transmission. Since this first theory, other explanations based on abnormal function of monoamine receptors or associated with impaired signalling pathways have been suggested. Notable progress has been accomplished in the treatment of major depressive disorders with new compounds recently discovered (selective serotonin reuptake inhibitors: SSRI; serotonin noradrenaline reuptake inhibitors: SNRI). Behavioural, electrophysiological and microdialysis studies have shown that serotonin (5-HT) receptors, mainly 5-HT1A, 5-HT1B and 5-HT2C sub-types, exert a key role in modulating antidepressant activity. Indirect activation of neurotransmitter receptors by antidepressants may also lead, via increases in endogenous levels of serotonin in synapses in specific brain regions, to activation of various G proteins coupled to a receptor, signal of transduction, transcription factors and neurotrophic factors such as brain-derived neurotrophic factor (BDNF). Thus, depression may be considered as a transduction mechanism anomaly. This hypothesis needs to be clarified by molecular biology. Although antidepressants have improved the therapeutic potential compared to tricyclics (TCA) in terms of reduced side effects, a number of problems still occur with these drugs. Clinical effects are not always observed until after this time has elapsed (4-6 weeks) and a substantial proportion of depressed patients show only partial or no response to antidepressants. Knowledge of the existence of links between neurotransmitter systems and the discovery of the most specific target, 5-HT receptors, should lead to improvements in antidepressant therapy. Developing drugs using innovative mechanisms such as directly acting on 5-HT receptors (5-HT1A agonists or 5-HT2 antagonists), would appear to be useful in the treatment of depression. The use of antidepressants in anxiety disorders such as obsessional compulsive disorders and even generalised anxiety, highlights the distinction between antidepressants and classic anxiolytics such as benzodiazepines, or even buspirone.

Relationship between cerebral pharmacokinetics and anxiolytic activity of diazepam and its active metabolites after a single intra-peritoneal administration of diazepam in mice

The relationship between the cerebral pharmacokinetics of diazepam and its active metabolites (desmethyldiazepam, oxazepam) and the anxiolytic effect evaluated by the four-plates test and the light/dark test were investigated after a single intra-peritoneal injection of diazepam (1 mg/kg or 1.5 mg/kg). For up to 30 min after administration, the sedative effect interfered with the anxiolytic effect, thus the results of the anxiolytic effect were not interpretable. From 30 min to 60 min after administration, this interference disappeared, the cerebral level of benzodiazepines was stable (the brain elimination of diazepam was compensated for by the appearance of desmethyldiazepam followed by oxazepam) but the anxiolytic effect decreased dramatically in all the tests with diazepam 1 mg/kg or 1.5 mg/kg. The acute tolerance to benzodiazepines and the difference of affinity for subtypes of GABA(A) receptors between diazepam, desmethyldiazepam, oxazepam could explain this result.

Helium-oxygen ventilation

Because of its low density, the He/O2 mixture markedly affects the dynamics of gas-flow, increasing inspiratory and expiratory flows, reducing WOB and respiratory acidosis, and relieving dyspnea in various clinical situations associated with obstructive airway disease. The magnitude of these changes varies according to the proportion of turbulent, transitional, and laminar flow conditions. These effects, however, last only as long as the patient breathes the He/O2 mixture, because it has no curative effect on the cause of airway obstruction. Thus, He/O2 ventilation is mostly useful while awaiting the effects of more definitive treatment. Evidence shows that He/O2 ventilation can improve pathophysiologic and clinical parameters in spontaneously breathing patients with upper airway obstruction, asthma. COPD, bronchopulmonary dysplasia. and bronchiolitis. Furthermore. He/O2 ventilation may prove to be a valuable adjunct in decompensated COPD patients, during both NIV and conventional mechanical ventilation. Despite promising results, however, there are two primary pitfalls to He/O2 ventilation. First, the consequences of the physical properties of the He/O2 mixture on various ventilator functions, the major differences between machines, and the correction factors to apply (if necessary) should be known. Second, in this age of cost control, particular attention should be paid to the cost-benefit ratio of He/O2 ventilation. Indeed, despite clinical evidence that the pathophysiologic principles on which He/O2 ventilation rests can be translated into favorable short-term physiologic and subjective effects, there is presently no evidence of a significant effect on patient outcome. Hence, before He/O2 ventilation can be recommended for widespread use, prospective outcome studies should be conducted in patients who suffer from the conditions discussed in this article to identify which, if any, are most likely to receive a benefit. Meanwhile, the authors recommend that He/O2 ventilation be reserved for patients who have a severe condition and who do not respond to the classic validated treatment modalities.

[Characteristics of hypersensitivity syndrome to lamotrigine: review of one case reported in the Regional Center of Pharmacovigilance of Nantes]

Drug-induced hypersensitivity syndrome is an uncommon but potentially life-threatening idiosyncratic drug reaction. In the literature, about five cases have been reported concerning hypersensitivity syndrome with lamotrigine. Most cases concern aromatic anticonvulsants but we report a case induced by lamotrigine which is a non aromatic anticonvulsant. A 73-year-old man was treated with lamotrigine for epilepsy due to a cerebrovascular stroke for 5 weeks. After 2 weeks with a single oral dose of 50 mg lamotrigine, the patient received 100 mg. Quickly thereafter fever, erythema and edema involving the periorbital area appeared. He was then admitted to hospital and lamotrigine was immediately discontinued. He developed acute hepatic and renal failure. During his hospital stay, he was treated with systemic and topical corticosteroids. After slow improvement, he was discharged 4 weeks later. Concerning this typical case, we review the characteristics of hypersensitivity syndrome and the different etiopathogenesis. The hypersensitivity syndrome typically develops two to six weeks after a drug is first administered, later than most other serious skin reactions. This syndrome manifests as rash, fever, tender lymphadenopathy, hepatitis and eosinophilia. The mechanism of hypersensitivity syndrome is unknown. Several theories have been proposed. The reaction is secondary to circulating antibodies or concerns toxic metabolities. On the other hand, association of human herpes virus 6 infection may play a role in the development of hypersensitivity syndrome. Hypersensitivity reactions to the aromatic antiepileptic drugs appear to have an immune etiology much like lamotrigine: bioactivation, detoxification, covalent adduct formation, processing and presentation of antigen to the immune system, and consequent formation of antibody and T-cell immune effectors. Another theory involves toxic metabolites; the aromatic antiepileptic agents are metabolised by cytochrome P-450 to an arene oxide metabolite. This is normally detoxified by epoxide hydrolase. This enzyme may be lacking or mutated in persons that develop the syndrome, and this is genetically determined. Lamotrigine is mainly metabolised by hepatic glucuronidation, but hypersensitivity may involve similar processes such aromatic antiepileptic drugs, except that the toxic metabolite has not yet been found. Because of slow evolution and clinical similarity to many infectious illnesses, the diagnosis of hypersensitivity syndrome may be delayed. Prompt recognition and withdrawal of the suspected drug is essential. The goal of research is to describe a "susceptibility profile" identifying individuals at risk for these forms of drug toxicity.

Patient-ventilator interactions during partial ventilatory support: a preliminary study comparing the effects of adaptive support ventilation with synchronized intermittent mandatory ventilation plus inspiratory pressure support

OBJECTIVE

To compare the effects of adaptive support ventilation (ASV) and synchronized intermittent mandatory ventilation plus pressure support (SIMV-PS) on patient-ventilator interactions in patients undergoing partial ventilatory support.

DESIGN

Prospective, crossover interventional study.

SETTING

Medical intensive care unit, university tertiary care center.

PATIENTS

Ten patients, intubated and mechanically ventilated for acute respiratory failure of diverse causes, in the early weaning period, ventilated with SIMV-PS and clinically detectable sternocleidomastoid activity suggesting increased inspiratory load and patient-ventilator dyssynchrony.

INTERVENTIONS

Measurement of respiratory mechanics, P0.1, sternocleidomastoid electromyographic activity, arterial blood gases, and systemic hemodynamics in three conditions: 1) after 45 mins with SIMV-PS (SIMV-PS 1); 2) after 45 mins with ASV, set to deliver the same minute-ventilation as during SIMV-PS; 3) 45 mins after return to SIMV-PS (SIMV-PS 2), with settings identical to those of the first SIMV-PS period.

MAIN RESULTS

The same minute ventilation was observed during ASV (11.4 +/- 3.1 l/min [mean +/- sd]) as during SIMV-PS 1 (11.6 +/- 3.5 L/min) and SIMV-PS 2 (10.8 +/- 3.4 L/min). No parameter was significantly different between SIMV-PS 1 and 2, hence subsequent results refer to ASV vs. SIMV-PS 1. During ASV, tidal volume increased (538 +/- 91 vs. 671 +/- 100 mL, p <.05) and total respiratory rate decreased (22 +/- 7 vs. 17 +/- 3 breaths/min, p <.05) vs. SIMV-PS. However, spontaneous respiratory rate increased in six patients, decreased in four, and remained unchanged in one. P0.1 decreased during ASV in all patients except three in whom no change was noted (1.8 +/- 0.9 vs. 1.1 +/- 1 cm H2O, p <.05). During ASV, sternocleidomastoid electromyogram activity was markedly reduced (electromyogram index, where SIMV-PS 1 = 100, ASV 34 +/- 41, SIMV-PS 2 89 +/- 36, p <.02) as was palpable muscle activity. No changes were noted in arterial blood gases, pH, or mean systemic pressure during the trial.

CONCLUSION

In patients undergoing partial ventilatory support, with clinical and electromyographic signs of increased respiratory muscle loading, ASV provided levels of minute ventilation comparable to those of SIMV-PS. However, with ASV, central respiratory drive and sternocleidomastoid activity were markedly reduced, suggesting decreased inspiratory load and improved patient-ventilator interactions. These preliminary results warrant further testing of ASV for partial ventilatory support.

[Results of a French nationwide survey of cutaneous side effects of ketoprofen gel reported between September 1996 and August 2000]

A French nation-wide pharmacovigilance survey of ketoprofen topic collated, from September 1996 to August 2000, 770 cutaneous side-effects. The frequency varies from 0.013@1000 to 0.028@1000 according to the commercial gel. Analysis concerns spontaneous notifications of French nation-wide pharmacovigilance. Sex ratio is well distributed, population is young. Treatment lasted about 12 days, the side-effects appearing after about 13 days, 25 per cent of cases are delayed to discontinuance of treatment, mainly after exposure to sunlight. Co-administered drugs are in most cases systemic or topical NSAIDs and/or fibrates and then increase the seriousness of the iatrogenic pathology. 75 per cent of cutaneous side-effects appear in summer, 50 per cent have been reported as "photosensitivity". Reactions are severe in 30 per cent of the cases. More than 80 per cent of cases present an extension beyond the site of application. The course is usually favourable and neither topical nor systemic corticosteroid treatment influence the duration of evolution. Photopatchtests testing in 23 per cent of cases show evidence of photoallergy to ketoprofen and crossed photoallergy with tiaprofenic acid, fenofibrate, oxybenzone and benzophenone. These results confirm that photoallergy is due to the common benzoylketone structure but not to their arylpropionic function. Some cases of persistent or recurrent photosensitivity must be more explored. The results lead to request a modification of marketing authorizations.

Outcome of mechanical ventilation for acute respiratory failure in patients with pulmonary fibrosis

OBJECTIVE

During the course of idiopathic pulmonary fibrosis patients may need invasive mechanical ventilation because of acute respiratory failure. We reviewed the charts of all patients with idiopathic pulmonary fibrosis admitted to our ICU for mechanical ventilation to describe their ICU course and prognosis.

DESIGN AND SETTING

Retrospective, observational case series, from December 1996 to March 2001, in an 18-bed medical ICU in a tertiary university hospital.

PATIENTS

Fourteen consecutive patients with idiopathic ( n=11) or secondary ( n=3) pulmonary fibrosis admitted to the medical ICU for mechanical ventilation.

MEASUREMENTS AND RESULTS

Relevant factors of history and hospital course such as diagnostic and therapeutic interventions were retrieved as well as laboratory and radiological results. All patients were admitted for severe acute hypoxemic respiratory failure (PaO(2)/FIO(2) 111+/-64 mmHg), with a high clinical suspicion of lower respiratory tract infection. Despite ventilatory support and adjunctive therapies (antibiotics, steroids, or immunosuppressive drugs), all patients gradually worsened and eventually died in the ICU after a mean stay of 7.6+/-4.6 days.

CONCLUSIONS

In this study mechanical ventilation for acute respiratory failure in pulmonary fibrosis patients was associated with a 100% mortality, despite aggressive therapeutic and diagnostic procedures.

First report of mirtazapine-induced arthralgia

OBJECTIVE

The aim of our work is to describe the first two cases of arthralgia associated with the antidepressant drug mirtazapine.

METHOD

Descriptive analysis of two iatrogenic cases. The review of the literature was achieved by the traditional electronic methods. The French database of iatrogenic cases was consulted.

RESULTS

A 53-year-old man presented with gonalgia after some weeks of mirtazapine treatment. The intensity of the arthralgia was correlated with the dosage and the adverse effect rapidly disappeared after the antidepressant therapy was stopped. A 38-year-old woman received mirtazapine for 3 months and complained of arthralgia and myalgia. This clinical picture was suspended as the drug was stopped and a positive reintroduction was observed. No other cause was found in these two patients.

DISCUSSION

No similar case has been reported in the international literature, but several observations of arthralgia with mianserin are mentioned. As mirtazapine is the 6-aza derivative of the tetracyclic antidepressant mianserin, the similarities of their chemical structures begs the responsibility of mirtazapine for arthralgia.

A follow-up study of a population of schizophrenic patients treated with clozapine

1. Clozapine is a dibenzodiazepine neuroleptic which presents the advantage of not having undesirable neurological side-effects. Its efficacy for the treatment of the symptoms of schizophrenia is known, but the use of clozapine is limited to treatment-resistant schizophrenic patients as it induces agranulocytosis with a higher incidence than that of other neuroleptic drugs. 2. The present study was designed in order to evaluate the benefit/risk of chronic treatment. The analysis was performed using the files of schizophrenic patients. These patients were not stabilized by a classical neuroleptic treatment and/or presented individual secondary effects. 3. Clozapine induced neutropenia and 1 case of agranulocytosis in 3 females. Analysis of leukocyte expression highlighted some premonitory symptoms in patients who presented neutropenia. The observation of 2 to 3 early successive peaks in leukocyte expression (between the third and tenth week of treatment) could be predictive of neutropenia in the 3 to 4 months of treatment. 4. The patients who presented a lower leukocyte base-line following a peak had a higher risk, of developing neutropenia. This might explain some late accidents beyond the first six months of treatment. 5. The present study confirmed the advantages of clozapine treatment and demonstrated that the risk of neutropenia may be diminished by the detection of premonitory symptoms and the early monitoring of patients at risk i.e. female patients and subjects with a lower leukocyte base-line.