A lymphokine regulates expression of alpha-1-proteinase inhibitor in human monocytes and macrophages.

Biosynthesis and secretion of alpha-1-proteinase inhibitor (alpha 1 PI) has been demonstrated in primary cultures of human mononuclear phagocytes, making it possible to study regulation of alpha 1 PI in normal (PiMM) and homozygous-deficient (PiZZ) individuals. In this study, expression of alpha 1 PI by blood monocytes, bronchoalveolar, and breast milk macrophages decreased during 1 wk in culture whereas expression of other secreted proteins increased. The addition of crude supernatants from mitogen-stimulated peripheral blood mononuclear cells to confluent monolayers of mononuclear phagocytes after 1 wk in culture resulted in a 2- to 2.5-fold increase in alpha 1 PI expression. The increase in alpha 1 PI expression was dose- and time-dependent, and involved a mechanism acting at a pretranslational level as shown by an increase in specific messenger RNA content corresponding to the increase in synthesis and secretion of alpha 1 PI. Although alpha 1 PI was expressed in native form and in forms complexed with serine protease by monocytes early in culture, it was expressed in its native form alone when monocytes were incubated with the lymphokine after 1 wk in culture. The regulating factor had the characteristics of a polypeptide and was derived from T lymphocytes, but it was not interferon-alpha, -beta, -gamma, or interleukin 2. This lymphokine also stimulated synthesis of alpha 1 PI in monocytes of homozygous-deficient PiZZ individuals, but had minimal effect on secretion, thereby increasing the intracellular accumulation of the inhibitor and exaggerating the defect in secretion of alpha 1 PI in these individuals. Regulation of mononuclear phagocyte alpha 1 PI expression by a lymphokine provides a model for further analysis of the effect of enhanced synthesis on a defect in posttranslational processing/secretion and for analysis of differential regulation of protease and inhibitor expressed in the same cells.

Isolation and partial characterization of a human alveolar macrophage-derived neutrophil-activating factor.

Human alveolar macrophages (AM) were obtained from eight normal volunteers using fiberoptic bronchoscopic lavage to explore potential interrelationships among leukocytes in pulmonary defense against infection. AM placed in monolayer tissue cultures released material into culture supernatants with the capacity to enhance the bactericidal capacity of human neutrophils. Neutrophils preexposed to supernatants killed Pseudomonas aeruginosa from 70 to 90% more efficiently than control cells (P less than 0.02). AM culture supernatants contained this material by 4 h of incubation, and in vitro stimulation of AM cultures with heat-killed P. aeruginosa further increased its production. Gel filtration of AM culture supernatants with a G-50 Sephadex column allowed isolation of a 6,000-D neutrophil-activating factor (NAF) that was resistant to heat (56 degrees C, 30 min). The isoelectric point of NAF, as determined by chromatofocusing, was approximately 7.6. Enzyme digestion of NAF specimens, prepared sequentially by gel filtration and chromatofocusing, demonstrated 50-70% loss of activity after incubations with trypsin, chymotrypsin, and neuraminidase. NAF was only minimally chemotactic and eluted from Sephadex G-50 with particles of a different molecular size than those of AM-derived chemotactic factors (i.e., approximately 10,000 D and less than 500 D). Preincubation of neutrophils with NAF resulted in greater release of superoxide anion upon their subsequent stimulation by either bacterial phagocytosis or by phorbol myristate acetate, as compared with control neutrophils stimulated in a like manner. These studies indicate that human AM secrete a heat-stable, low molecular weight basic protein, with the capacity to enhance oxidative microbicidal activity of neutrophils.

Effects of frequency, tidal volume, and lung volume on CO2 elimination in dogs by high frequency (2-30 Hz), low tidal volume ventilation.

Recent studies have shown that effective pulmonary ventilation is possible with tidal volumes (VT) less than the anatomic dead-space if the oscillatory frequency (f) is sufficiently large. We systematically studied the effect on pulmonary CO2 elimination (VCO2) of varying f (2-30 Hz) and VT (1-7 ml/kg) as well as lung volume (VL) in 13 anesthetized, paralyzed dogs in order to examine the contribution of those variables that are thought to be important in determining gas exchange by high frequency ventilation. All experiments were performed when the alveolar PCO2 was 40 +/- 1.5 mm Hg. In all studies, VCO2 increased monotonically with f at constant VT. We quantitated the effects of f and VT on VCO2 by using the dimensionless equation VCO2/VOSC = a(VT/VTo)b(f/fo)c where: VOSC = f X VT, VTo = mean VT, fo = mean f and a, b, c, are constants obtained by multiple regression. The mean values of a, b, and c for all dogs were 2.12 X 10(-3), 0.49, and 0.08, respectively. The most important variable in determining VCO2 was VOSC; however, there was considerable variability among dogs in the independent effect of VT and f on VCO2, with a doubling of VT at a constant VOSC causing changes in VCO2 ranging from -13 to +110% (mean = +35%). Increasing VL from functional residual capacity (FRC) to the lung volume at an airway opening minus body surface pressure of 25 cm H2O had no significant effect on VCO2.

Treatment of acute asthma. Is combination therapy with sympathomimetics and methylxanthines indicated?

The role of bronchodilator regimens combining a sympathomimetic and a methylxanthine in the treatment of acute exacerbations of asthma remains controversial. This report describes the outcome of 157 emergency room visits for asthma in which patients were randomly assigned to single-drug therapy with intravenous aminophylline, subcutaneous epinephrine, or inhaled isoproterenol or to one of three regimens combining a sympathomimetic and a methylxanthine. The increase in one-second forced expiratory volume after one hour of treatment with the two-drug combinations (0.79 +/- 0.07 liter) was significantly greater than for epinephrine alone (0.57 +/- 0.08 liter; p less than 0.05) but did not differ significantly from that occurring with therapy with isoproterenol alone (0.72 +/- 0.09 liter; p = NS). This disparity reflects the greater bronchodilation effected by isoproterenol as a single agent than by epinephrine, in the dosing schedules and routes of administration chosen. Among patients presenting with severe airflow obstruction (one-second forced expiratory volume 35 percent or less of normal), the bronchodilator response to isoproterenol alone was 0.88 +/- 0.14 liter versus 0.51 +/- 0.11 for epinephrine alone (p less than 0.05). It is concluded that the observed benefit derived from use of combination therapy depends on the dosage and potency of the particular sympathomimetic to which a methylxanthine is added, and on the severity of the airflow obstruction at presentation.

Glucocorticoids in acute asthma. A critical controlled trial.

In order to determine objectively the efficacy of corticosteroids in relieving severe acute episodes of asthma, we administered infusions of hydrocortisone or placebo in a random, double-blind manner to 20 asthmatic subjects after they had been documented to be refractory to eight hours of conventional therapy. Eleven subjects received hydrocortisone (2 mg/kg bolus, then 0.5 mg/kg per hour for 24 hours) and nine received saline. All were given identical bronchodilator treatment during the study period, and all had multiple aspects of lung function serially recorded along with plasma cortisol levels. Although subjects in both groups had severe obstruction of similar magnitude at the beginning of treatment (one-second forced expiratory volume [FEV1] in placebo-treated group = 32 +/- 3 [SEM] percent of predicted, and 25 +/- 3 percent of predicted in steroid-treated group, p = NS), at the end of 24 hours, the subjects given corticosteroids had significantly greater resolution of airway obstruction (FEV1 in steroid-treated group increased 118 +/- 25 percent from control value, versus 35 +/- 22 percent with placebo). In five of nine subjects treated with placebo, pulmonary mechanics either were unchanged or deteriorated during the period of observation. There was no effect of the glucocorticoids on arterial blood gases, and no significant correlation could be found between plasma cortisol levels and the improvement in pulmonary mechanics and clinical status. These results provide objective documentation of the time course over which administration of parenteral corticosteroids speeds the recovery of asthmatic patients who are unresponsive to standard therapy.

Effect of outpatient treatment of asthma with beta agonists on the response to sympathomimetics in an emergency room.

It has been suggested that tolerance to the bronchodilating effects of sympathomimetics may develop in asthmatic patients after long-term use of these agents. In an emergency room setting, the effects of inhaled and injected sympathomimetic therapy in 58 patients who had pretreated themselves with beta agonists were compared with the results observed in 38 patients who had not used such drugs. The two groups had similar degrees of obstruction on presentation and were also well-matched with respect to the clinical features of their illness. Both populations showed equal responses to treatment; no significant differences were found in either the amount of bronchodilation or the incidence of adverse effects in those who had or had not taken sympathomimetics as outpatients. These findings indicate that drug resistance does not account for outpatient treatment failures with sympathomimetics and that beta agonists can be usefully employed in the treatment of acute asthma, irrespective of a patient's medication history.

Emergency room of treatment of asthma. Relationships among therapeutic combinations, severity of obstruction and time course of response.

In an effort to determine the optimal emergency therapy for acute episodes of asthma, we randomly, assigned 102 acute ill patients to 60 minutes of treatment with inhaled isoproterenol alone, isoproterenol plus intravenous aminophylline or isoproterenol plus a single oral dose of an elixir of theophylline. Patients requiring treatment beyond this time were given an injectable sympathomimetic agent in addition. The combination of isoproterenol and a methylxanthine was not found to be better than isoproterenol alone, and the route of administration of methylxanthine was not an important determinant of either the serum theophylline level or the therapeutic response. A major variable that influenced the duration of therapy needed to produce a remission was the severity of the obstruction at presentation. Persons whose initial 1-second forced expiratory volumes were less than 30 percent of predicted and who did not improve 35 percent or more to at least 40 percent of predicted at the end of 60 minutes of intense treatment were those who ultimately required prolonged emergency room therapy and/or hospital admission for control of their symptoms. Thus, simple objective assessment of the degree of impairment at presentation coupled with the response to initial treatment will serve to identify early a high-risk group of asthmatic patients in whom the usual emergency room therapeutic modalities will often prove ineffective.

Prevalence of abnormal thyroid function test results in patients with acute medical illnesses.

We measured serum total and free thyroxine (T4) and triiodothyronine (T3) concentrations, free T4 and T3 indexes, thyroid-stimulating hormone (TSH), thyroxine-binding globulin (TBG) and thyroxine-binding prealbumin (TBPA) concentrations in 98 patients hospitalized for acute medical illnesses. The free thyroxine index (FT4I) or TSH level was abnormal in 16 percent, but only 3 percent had thyroid disease. Serum fre T4 measurements by equilibrium dialysis were abnormal in 25 percent, but no additional patients who initially had abnormal concentrations of serum free T4 were subsequently proved to have thyroid disease. Patients with supranormal serum free T4 concentrations (21 percent) ahd higher serum T4, lower serum T3, and higher serum reverse T3 (rT3) concentrations than other patients, but the measured changes in serum T4, TBG and TBPA levels could only partly account for the magnitude of the free T4 elevation. In these acutely ill patients, an accurate diagnosis of thyroid disease could be achieved by determination of FT4I and TSH level and a history of medication usage. We conclude that other tests are rarely necessary for this purpose in a patient population such as this.

Practice patterns in the treatment of acutely ill hospitalized asthmatic patients at three teaching hospitals. Variability in resource utilization.

STUDY OBJECTIVE: Our objective was to determine the extent to which patterns of diagnostic and therapeutic practice differ among hospitals caring for acutely ill hospitalized asthmatic patients in a single city. DESIGN: Our study comprised a retrospective review of the records of patients admitted to the hospital for the treatment of acute asthma. SETTING: Three large teaching hospitals in Boston were the setting. PATIENTS: One hundred twenty-seven patients between 18 and 50 years of age who were admitted to the medical services specifically for the treatment of asthma were studied. INTERVENTIONS: There were no interventions. MEASUREMENTS AND MAIN RESULTS: For this group of patients with similar histories of asthma, clinical presentation, and severity of asthma, the diagnostic tests used within 12 hours of admission and the frequency and volume of diagnostic laboratory testing throughout the admission differed significantly among the three hospitals. Spirometry, the test bearing most directly on the severity of the asthmatic attack, was not used routinely as a criterion for admission or discharge at any of the hospitals. Other tests of uncertain efficacy, such as chest x-ray films, were used frequently at some of the hospitals. Patients at all three hospitals were treated similarly with intensive combined regimens of methylxanthines, sympathomimetics, and corticosteroids and had similar mean lengths of stay. The use of chest physical therapy, which has not yet been demonstrated to be effective in acute asthma, differed significantly among the three hospitals. CONCLUSIONS: We conclude that considerable variability exists in the diagnostic evaluation of acutely ill hospitalized asthmatic patients in the three hospitals; little variability exists in the pharmacologic treatment of these patients. In the absence of data on outcome regarding functional improvement and reductions in morbidity, we are unable to recommend a preferred pattern of practice from this study.

Acid-base effects of altering plasma protein concentration in human blood in vitro.

We altered the concentration of plasma proteins in human blood in vitro by adding solutions with [Na+], [K+], and [Cl-] resembling those in normal blood plasma, either protein-free or with a high concentration of human albumin. After equilibrating the samples with a gas containing 5% CO2-12% O2-83% N2 at 37 degrees C, we measured pH, PCO2, and PO2; in separated plasma, we determined the concentrations of total plasma proteins and albumin and of the completely dissociated electrolytes (strong cations Na+, K+, Mg2+ and anions Cl-, citrate3-). With PCO2 nearly constant (mean = 35.5 Torr; coefficient of variation = 0.02), lowering plasma protein concentration produced a metabolic alkalosis, whereas increasing plasma albumin concentration gave rise to a metabolic acidosis. These acid-base disturbances occurred independently of a minor variation in the balance between the sums of strong cations and anions. We quantified the dependence of several acid-base variables in plasma on albumin (or total protein) concentration. Normal plasma proteins are weak nonvolatile acids. Although their concentration is not regulated as part of acid-base homeostasis, hypoproteinemia and hyperalbuminemia per se produce alkalosis and acidosis, respectively.

Expiratory flow limitation and dynamic pulmonary hyperinflation during high-frequency ventilation.

Dynamic hyperinflation of the lungs occurs during high-frequency oscillatory ventilation (HFOV) and has been attributed to asymmetry of inspiratory and expiratory impedances. To identify the nature of this asymmetry, we compared changes in lung volume (VL) observed during HFOV in ventilator-dependent patients with predictions of VL changes from electrical analogs of three potential modes of impedance asymmetry. In the patients, when a fixed oscillatory tidal volume was applied at a low mean airway opening pressure (Pao), which resulted in little increase in functional residual capacity, progressively greater dynamic hyperinflation was observed as HFOV frequency, (f) was increased. When mean Pao was raised so that resting VL increased, VL remained at this level during HFOV as f was increased until a critical f was reached; above this value, VL increased further with f in a fashion nearly parallel to that observed when low mean Pao was used. Three modes of asymmetric inspiratory and expiratory impedance were modeled as electrical circuits: 1) fixed asymmetric resistance [Rexp greater than Rinsp]; 2) variable asymmetric resistance [Rexp(VL) greater than Rinsp, with Rexp(VL) decreasing as VL increased]; and 3) equal Rinsp and Rexp, but with superimposed expiratory flow limitation, the latter simulated using a bipolar transistor as a descriptive model of this phenomenon. The fixed and the variable asymmetric resistance models displayed a progressive increase of mean VL with f at either low or high mean Pao. Only the expiratory flow limitation model displayed a dependence of dynamic hyperinflation on mean Pao and f similar to that observed in our patients. We conclude that expiratory flow limitation can account for dynamic pulmonary hyperinflation during HFOV.

Diphtheria immunity in Massachusetts--a study of three urban patient populations.

To determine the status of diphtheria immunity among our patients, we measured diphtheria antitoxin levels in three separate patient populations. The technique used was toxin neutralization in rabbit skin, which allowed us to evaluate the immune status of individual patients. We studied an emergency room population, a sampling of inpatients from an urban teaching hospital, and a group of older patients from a chronic care hospital. Overall, approximately 80% of patients had adequate diphtheria antitoxin levels in their serum. However, two subgroups emerged with lower levels, with potential nonimmunity. These were certain young patients, either foreign born or with a potentially "immunocompromising disorder," and the elderly chronically ill. We conclude that while overall diphtheria immunity in our patients appears adequate, subgroups with increased risks do exist and immunization for these subgroups should be undertaken.

Effects of milrinone on contractile responses of guinea pig trachea, lung parenchyma and pulmonary artery.

The effects of milrinone, a bipyridine with known vasodilator activity, on guinea pig tracheal-spirals, lung parenchymal strips and pulmonary artery rings in vitro were compared with the effects of isoproterenol and aminophylline on these tissues. The concentration of milrinone that produced 50% relaxation (IC50) of tracheal spirals constricted by carbachol was 3.6 X 10(-5) M. Isoproterenol (IC50, 9.5 X 10(-8) M) was significantly (P less than .001) more potent and aminophylline (IC50, 1.2 X 10(-4) M) was significantly (P less than .001) less potent than milrinone in this effect. The IC50 for milrinone for lung parenchymal strips contracted by histamine was 3.2 X 10(-5) M, whereas the IC50 for isoproterenol was significantly (P less than .001) less, 1.4 X 10(-7) M; aminophylline produced only limited relaxation of lung parenchymal strips. Milrinone relaxed pulmonary artery rings constricted by norepinephrine with an IC50 of 3.8 X 10(-6) M, whereas neither isoproterenol nor aminophylline produced a 50% relaxation. Pretreatment of tracheal spirals, lung parenchymal strips and pulmonary artery rings with 1.6 X 10(-4) M milrinone inhibited subsequent contraction by carbachol, histamine and norepinephrine, respectively. The relaxant effects of milrinone were not influenced by treatment with atropine, cimetidine, mepyramine, phentolamine or propranolol. However, indomethacin blocked milrinone's relaxant effects on tracheal spirals effectively, but not on pulmonary artery rings or lung parenchymal strips, suggesting distinct modes of action on various tissue types.

Acid-base disorders in critical care medicine.

In critically ill patients, nonrespiratory (metabolic) alkalosis is the most common acid-base disturbance; it is caused by hypochloremia and/or by hypoproteinemia. Information on the concentration of plasma proteins should be included when evaluating acid-base status.

Survival in lung cancer. An analysis of the effects of age, sex, resectability, and histopathologic type.

Records of 6,686 patients with primary lung malignancies were retrieved from a tumor registry. Survival curves according to histopathologic type demonstrated that patients with anaplastic tumors have a lower cumulative survival than those with either squamous cell cancers or adenocarcinomas (p less than 0.001), but survival for the latter two histologic types is similar. Age at diagnosis influences survival, and women with squamous or anaplastic tumors have a better prognosis than men with the same cell types (p less than 0.001). Although selection for resection is strongly associated with lower early mortality, all patients alive 2 yr after diagnosis have a similar prognosis is regardless of initial resectability. Each survival curve shows a high early mortality and a lower late mortality, indicating that each group can be considered to consist of 2 subgroups with different risks of dying of lung cancer. A mathematical model is described that closely approximates the actuarial survival.

The role of serum proteins in acid-base equilibria.

Serum proteins act as weak acids and participate in acid-base balance. Their effects are imprecisely quantified; in particular, the roles of albumin and globulins need reevaluation. We approached the problem in three steps. First, in artificial solutions resembling serum but with human serum albumin as the only protein moiety, we varied the strong ion difference (SID), partial pressure of carbon dioxide (Pco2) and the concentration of albumin [( Alb]) and fixed the concentration of inorganic phosphate [( Pi]). We measured pH and derived the charges on albumin. Second, extending the work of Stewart (Stewart PA. How to understand acid-base. A quantitative acid-base primer for biology and medicine. New York: Elsevier, 1981:1-286), we developed a mathematical model that solves for pH and for the charges on albumin as functions of SID, Pco2, [Pi], and [Alb]. The calculated values fit the observed values well; that is, the model describes well the behavior of these solutions over a wide range of simulated complex acid-base disturbances. Finally, in human serum samples containing both albumin and globulins, we varied SID, Pco2, and total protein concentration [( TP]); we fixed [Pi] and then measured pH and derived the charges on proteins as above. When we applied to these data the computer model developed for albumin alone, the calculated pH and derived charges on albumin values agreed well with the observed pH and derived charges on proteins. We conclude first that human serum globulins play a negligible role in acid-base equilibria, and second, that in normal human serum at pH 7.40 with [TP] = 7 and [Alb] = 4.3 gm/dl, the charges attributed to proteins are approximately 12 mEq/L; this is substantially less than the value of approximately 17 mEq/L given by many contemporary texts, based on work of van Slyke et al. (van Slyke DD, Hastings AB, Hiller A, Sendroy J Jr. Studies of gas and electrolyte equilibria in blood. XIV. Amounts of alkali bound by serum albumin and globulin. J Biol Chem 1928;79:769-80). These findings should be considered when evaluating acid-base balance in patients with abnormal serum albumin concentration, for example, when interpreting values of the anion gap.

The tuberculin test. Studies of the dynamics of reactivity to tuberculin and Candida antigen in institutionalized patients.

To determine the importance of the recall phenomenon ("booster effect") in chronically hospitalized patients, we performed three sequential tuberculin and Candida antigen skin tests in patients at two hospitals. Twenty of 162 patients (12.3%) demonstrated a significant reaction on the initial tuberculin test, and 9 additional patients (5.5%) showed a significant reaction (booster response) to a second tuberculin test administered 3 wk later. Five patients (3.1%) demonstrated a significant reaction only when a third tuberculin test was administered 6 wk after the initial test. Only 1 patient (0.6%) with a significant tuberculin reaction on the first 2 tests was nonreactive on the third test. Nineteen patients (11.7%) demonstrated a significant response to Candida antigen on the initial test and a booster effect was noted in 11 (6.2%) and 6 (3.7%) patients, respectively, on subsequent tests. Four patients (2.5%) appeared to lose reactivity to Candida antigen on each of the 2 repeat tests. Only 25% of patients who demonstrated a tuberculin booster response had a significant reaction to the initial Candida skin test. Serial skin tests may be necessary to reliably determine the ability of a chronically hospitalized patient to demonstrate a response to tuberculin.

Comparative oxidative microbicidal activity of human blood monocytes and alveolar macrophages and activation by recombinant gamma interferon.

The relative oxidative and microbicidal activities of human blood monocytes compared with those of alveolar macrophages (AM) are poorly defined. Furthermore, the comparative efficiency of recombinant gamma interferon (rIFN gamma) to enhance microbicidal function of these 2 cell populations is uncertain. In this study, blood monocytes and AM were obtained concomitantly from 10 healthy, nonsmoking human subjects. Cells were adjusted to equivalent cell concentrations and assayed for respiratory burst activity (superoxide anion production) during soluble (Concanavalin A) or particulate (bacteria) stimulation. Microbicidal activity against Pseudomonas aeruginosa, Listeria monocytogenes, and Candida albicans was also determined for each cell type. Finally, the capacity of rIFN gamma treatment (200 U/ml for 24 h) to enhance these cellular activities was determined. Oxidative activity of AM was greater than that of blood monocytes (p less than 0.01, bacteria; p less than 0.02, Con A). Likewise, AM exhibited greater killing of P. aeruginosa (p less than 0.01) and L. monocytogenes (p less than 0.01) than did monocytes. Neither cell killed C. albicans. Treatment with rIFN gamma greatly enhanced both respiratory burst and microbicidal activity of blood monocytes, but had no effect on AM respiratory burst. Despite this, rIFN gamma-treated AM did exhibit some enhanced killing of L. monocytogenes (p less than 0.05). We conclude that oxidative microbicidal activity of resident AM greatly exceeds that of blood monocytes, but that blood monocytes are relatively more susceptible to activation by rIFN gamma.

Effects of milrinone on contractility of the rat diaphragm in vitro.

We studied the effects of the phosphodiesterase inhibitor, milrinone, on isometric force production in the isolated, directly stimulated rat diaphragm. Milrinone (500 micrograms/ml) significantly increased force during twitch stimulation and submaximal tetanic stimulation (p less than 0.05); force during maximal tetanic stimulation was significantly reduced by milrinone (p less than 0.05). The force-augmenting effects of milrinone were not abolished by pretreatment with indomethacin (10(-5)M). Baseline force production decreased when diaphragmatic strips were placed in a calcium-free bathing solution; force potentiation by milrinone, however, persisted in this medium. Pretreatment with milrinone more than doubled the mean time to fatigue (10.8 +/- 1.0 versus 5.1 +/- 0.6 min) during repetitive submaximal stimulation (p less than 0.01). In diaphragmatic strips fatigued by repetitive submaximal stimulation until force production was 60% of baseline, milrinone promptly improved force production; the magnitude of force potentiation after milrinone was quite similar in fresh and fatigued muscle. In conclusion, milrinone enhances diaphragmatic contractility during the most forms of direct stimulation, and delays and reverses diaphragmatic fatigue.

Hyperventilation with hypoproteinemia.

Hypoproteinemia by itself produces a metabolic alkalosis. It is not clear whether a respiratory compensation (hypercapnia) develops with this alkalosis; patients with liver cirrhosis, most of them with hypoproteinemia, are known to hyperventilate. We studied 23 clinically stable patients with hypoproteinemia, with very low albumin-to-globulin ratios (range 0.4 to 1.1), who had either liver cirrhosis (n = 12) or other medical conditions (n = 11). In both groups, there was marked hypocapnia, accompanied by alkalemia (PaCO2 values (mean +/- SD) 31 +/- 2 and 32 +/- 3 torr; pH (mean +/- SD) 7.45 +/- 0.03 and 7.47 +/- 0.03, for the patients with cirrhosis and those without, respectively). Hypoxemia was not the stimulus provoking hyperventilation. The lowering of PaCO2 was proportional to the reduction of serum albumin and total protein concentrations; no detectable difference was seen between the patients with cirrhosis and those without cirrhosis in this apparent dependence of PaCO2 on the concentration of serum proteins. Many of these clinically stable patients with hypoproteinemia, with or without liver cirrhosis, had appreciable concentrations of unidentified anions in plasma (inappropriately high anion gap). Whatever the nonrespiratory acid-base status of the patients with hypoproteinemia, their pulmonary ventilation (hypocapnia) appeared excessive when compared with subjects (presumably) without proteinemia who had similar nonrespiratory acid-base states. The mechanism responsible for the hyperventilation in hypoproteinemia and the nature of the unidentified anions in this condition are obscure.