A Statistical Analysis of Weekday Operating Room Anesthesia Group Staffing Costs at Nine Independently Managed Surgical Suites

At many surgical suites, surgeons and patients schedule elective cases on whatever future workday they choose, resulting in there being no limit on the number of cases performed each day. Staff are then scheduled in the manner that satisfies the marketing guarantee to the surgeons, satisfies labor contracts, and minimizes staffing costs. We assessed weekday nurse anesthesia group staffing at nine such suites to determine whether statistical methods can identify staffing solutions whereby all the cases are covered but for which staffing costs are less than those obtained using the staffing plans implemented by anesthesia groups' managers. Two years of operating room information system case duration and staffing data were analyzed. First- and second-shift staffing was assessed using previously published algorithms. The statistical methods identified staffing solutions with significantly decreased labor costs than those currently being used at eight of the nine surgical suites. The statistical methods relied more on overtime than second-shift staffing. The incremental decrease in staffing costs achievable by using overlapping 8-, 10-, and 13-h shifts was negligible. Overall, we found that statistical methods can identify, for some surgical suites, staffing solutions whereby all the cases are covered but for which costs are significantly less and productivity significantly more than those obtained using the plans developed by the managers based on their experience and the data.

IMPLICATIONS

Statistical methods can identify, for some surgical suites, anesthesia staffing solutions whereby all the cases are covered but for which labor costs are significantly less than those obtained using the staffing plans developed by the managers based on data and their experience.

Time course of 72-kilodalton heat shock protein induction and appearance of trifluoroacetyl adducts in livers of halothane-exposed rats

Previous studies have shown that exposure of phenobarbital-pretreated rats to halothane in 10% O2 causes centrilobular necrosis, induces expression of the 72-kDa heat shock protein (HSP72), and produces several trifluoroacetylated adducts. In the present study the time course of development of the centrilobular lesion, as measured by histochemistry, was compared with the time course of appearance of both trifluoroacetylated adducts and HSP72, as measured by Western blotting. One group of 20 rats was pretreated with phenobarbital for 5 days, whereas a second group of two rats was left as untreated controls. Ten phenobarbital-pretreated rats were exposed for 2 hr to 1% halothane in 10% O2 and 10 were exposed to 1% halothane in 20% O2. At either 2, 4, 6, or 24 hr after exposure, livers were excised and frozen without fixation. Thin sections stained with hematoxylin and eosin demonstrated that centrilobular lesions occurred at 6 hr and became extensive at 24 hr in rats pretreated with phenobarbital and exposed to 1% halothane in 10% O2. The time course of appearance of both trifluoroacetylated adducts and HSP72 was determined by Western blotting. Trifluoroacetylated adducts appeared in all rats exposed to halothane by 2 hr, lasted until 6 hr, and then diminished by 24 hr. In contrast, HSP72 was induced only in the rats pretreated with phenobarbital and exposed to 1% halothane in 10% O2. HSP72 appeared in both the nuclear and supernatant fractions at 6 hr after exposure and was intense 24 hr after exposure.

Nuclear translocation of heat shock protein 72 in liver cells of halothane-exposed rats

Immunocytochemical studies have revealed that one of the major heat shock proteins, HSP72, is induced in livers of rats that have been pretreated with phenobarbital and then administered halothane in a hypoxic gas mixture of 10% oxygen. To determine the sub-cellular localization of HSP72 in the livers of these rats 24 hr after halothane administration, cytoplasmic and nuclear fractions were prepared and separated by PAGE electrophoresis. Western blotting with a mouse monoclonal anti-HSP70 IgG antibody, which recognizes both the constitutive (HSP73) and inducible (HSP72) forms, revealed that HSP72 was induced and translocated into the nucleus in only those rats exposed to halothane under hypoxia following phenobarbital pretreatment. Nuclear translocation of HSP72 under the latter conditions was confirmed by immunocytochemical staining using gold-conjugated secondary antibodies followed by digital laser microscopy with Nomarski optics. Neither phenobarbital pretreatment alone nor phenobarbital plus hypoxia treatment induced HSP72. No alteration in amount of HSP73 was observed under any of these conditions.

Episodic central neurogenic hyperventilation in an awake child with systemic histiocytosis

A 3 year old boy with systemic histiocytosis, diabetes insipidus and a lytic parietal bone lesion experienced episodes of central neurogenic hyperventilation 3 weeks after radiation to the head but was conscious and alert at presentation. At admission, the PaO2 was 133 mmHg, PaCO2 was 8 mmHg and pH 7.65. Magnetic resonance imaging revealed a pontomedullary lesion that resolved during the ensuring year. Central neurogenic hyperventilation has not been described previously as a complication of systemic histiocytosis.

Prevention of infection in critically ill patients by selective decontamination of the digestive tract

OBJECTIVE

To determine whether selective decontamination of the digestive tract using oral and nonabsorbable antimicrobial agents and parenteral cefotaxime prevents infection in critically ill patients.

DESIGN

Randomized, controlled trial without blinding.

SETTING

Surgical trauma and medical intensive care units in a tertiary referral hospital.

PATIENTS

One hundred fifty patients admitted to surgical trauma and medical intensive care units during a 3-year interval, whose condition suggested a prolonged stay (greater than 3 days).

INTERVENTION

Patients were randomly allocated to an experimental group (n = 75) that received cefotaxime, 1 g intravenously every 8 hours for the first 3 days only, and oral, nonabsorbable antibiotics (gentamicin, polymyxin, and nystatin by oral paste and oral liquid) for the entire stay in the intensive care unit. Control patients (n = 75) received usual care.

MEASUREMENTS

The number of infections, total hospital days, and deaths, as well as the number of days in intensive care unit, were recorded.

RESULTS

Control patients experienced more infections (36 compared with 12, P = 0.04), including bacteremias (14 compared with 4, P = 0.05) and pulmonary infections (14 compared with 4, P = 0.03). Although total hospital days, days in intensive care, and the overall death rate all were lower in the treatment group, these differences were not statistically significant. Clinically important complications of selective decontamination of the digestive tract were not encountered.

CONCLUSIONS

Selective decontamination of the digestive tract decreases subsequent infection rates, especially by gram-negative bacilli, in selected patients during long-term stays in the intensive care unit.

Hospital and posthospital survival in patients mechanically ventilated for more than 29 days

Experience with prolonged mechanical ventilation has improved over recent years. Retrospective analysis of the records of 104 patients older than 16 years of age who were mechanically ventilated for more than 29 days over a 29-month period from May 1986 to October 1988 revealed the following findings. The mean patient age was 66.3 +/- 15.7 years (SD). The mean number of in-hospital ventilator days was 59.9 +/- 36.7 days (range, 29 to 247 days). The mean number of days of oral or nasal endotracheal intubation prior to tracheostomy (96 patients) was 21.5 +/- 14.2 days. The mean length of hospital stay for the 104 patients was 79.9 +/- 45.4 days. The majority of the 104 patients (82.6 percent) were surgical patients. Nine patients left the hospital receiving extended mechanical ventilation. Mortality was highest in multiple organ system failure and lowest among the trauma patients. The total days of mechanical ventilation did not appear to be related to mortality if patients older than 16 years survived for seven days. Postdischarge survival of the 53 of 60 patients who survived and whom we were able to contact was 67 percent at one year and 56 percent at three years.

Immunocytochemical detection of the 72-kDa heat shock protein in halothane--induced hepatotoxicity in rats

Liver sections removed from phenobarbital induced rats 24 to 48 hours after a 2 hour exposure to 1.0% halothane with 10% oxygen and subjected to immunocytochemical treatment showed evidence of centrilobular damage as well as evidence of the production of a protein which has immunoreactivity with anti HSP 72 antibodies. The cells showing evidence of immunoreactivity were within the area of the centrilobular lesion. The level of immunoreactive protein varied directly with the intensity of the lesion. Liver sections from animals treated with phenobarbital alone, phenobarbital plus 10% oxygen, or phenobarbital plus 20% oxygen and 1.0% halothane all were without lesions as well as the immunoreactive protein.

Significance of mildly elevated creatine kinase (myocardial band) activity after elective abdominal aortic aneurysmectomy

The clinical significance of mildly elevated creatine kinase (CK) myocardial band (MB) enzyme levels in patients undergoing elective repair of an abdominal aortic aneurysm was evaluated retrospectively in 348 patients. For each patient, preoperative and postoperative electrocardiograms (ECGs) were interpreted blindly for left ventricular hypertrophy, ST segment abnormality, left bundle branch block, right bundle branch block, left axis deviation, atrial fibrillation, T wave abnormality, and Q waves. A total of 107 patients (31%) had postoperative CK-MB elevations of trace or greater; 37 had trace, 35 had 1% to 4%, and 35 had greater than or equal to 5% elevation. There was no difference in survival between those with trace and no CK-MB elevation. Patients with increased CK-MB (greater than or equal to 1%) values were more likely to have ECG abnormalities. The following ECG (either preoperative or postoperative) abnormalities were univariately related to decreased postoperative survival: left ventricular hypertrophy (P less than 0.001), ST segment abnormalities (P less than 0.001), left bundle branch block (P less than 0.001), the combination of right bundle branch block and left axis deviation (P = 0.006), Q wave infarction (P less than 0.001), and atrial fibrillation (P less than 0.001). There were 15 in-hospital deaths, and 333 patients were discharged and followed-up for a median of 4.6 years. There were 97 posthospitalization deaths, 61% of which were due to cardiac causes. Overall survival was associated with the degree of CK-MB elevation; the higher the CK-MB, the worse the survival.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of extracellular and net glucose oxidation measured isotopically and by indirect calorimetry during high and low glucose turnover

To determine the extent to which glucose oxidation measured by indirect calorimetry reflects glucose oxidation measured isotopically, subjects were studied during a 6-h hyperinsulinemic euglycemic clamp (1 mU.kg-1.min-1) and during infusion of saline. [6-14C]glucose was infused on both occasions. Breath was collected for determination of the specific activity of carbon dioxide, oxygen consumption, and carbon dioxide production. Glucose turnover during hyperinsulinemia was approximately eightfold higher than during saline infusion. During the final 1.5 h of the hyperinsulinemic glucose clamp, oxidation measured isotopically remained slightly but consistently lower (P less than 0.05) than that measured by indirect calorimetry (13.8 +/- 1.1 vs 16.5 +/- 1.7 mumol.kg-1.min-1, respectively). In contrast, during the saline infusion, glucose oxidation measured isotopically did not differ from that measured by indirect calorimetry (8.3 +/- 0.6 vs 7.2 +/- 2.8 mumol.kg-1.min-1, respectively). We conclude that although net glucose oxidation measured isotopically was slightly lower than that measured by indirect calorimetry, both techniques provide similar estimates of glucose oxidation over a wide range of glucose disposal.

Differential effects of prednisone and growth hormone on fuel metabolism and insulin antagonism in humans

Human growth hormone (hGH) and prednisone cause insulin resistance and glucose intolerance. However, it is unknown whether hGH and prednisone antagonize insulin action on protein, fat, and carbohydrate metabolism by a common or independent mechanism. Therefore, protein, fat, and carbohydrate metabolism was assessed simultaneously in four groups of eight subjects each after 7 days of placebo, recombinant DNA hGH (rhGH; 0.1 mg.kg-1.day-1), prednisone (0.8 mg.kg-1.day-1), or rhGH and prednisone administration after an 18-h fast and during gut infusion of glucose and amino acids (fed state). Fasting plasma glucose concentrations were similar during placebo and rhGH but elevated (P less than 0.001) during combined treatment, whereas plasma insulin concentrations were higher (237 +/- 57 pmol/ml, P less than 0.001) during combined than during placebo, rhGH, or prednisone treatment (34, 52, and 91 pM, respectively). In the fed state, plasma glucose concentrations were elevated only during combined treatment (11.3 +/- 2.1 mM, P less than 0.001). Plasma insulin concentrations were elevated during therapy with prednisone alone and rhGH alone (667 +/- 72 and 564 +/- 65 pmol/ml, respectively, P less than 0.001) compared with placebo (226 +/- 44 pmol/ml) but lower than with the combined rhGH and prednisone treatment (1249 +/- 54 pmol/ml, P less than 0.01). Protein oxidation [( 14C]leucine) increased (P less than 0.001) with prednisone therapy, decreased (P less than 0.001) with rhGH treatment, and was normal during the combined treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of prediction of mortality by using the APACHE II scoring system in intensive-care units;

Some investigators have suggested that information on quality of care in intensive-care units (ICUs) may be inferred from mortality rates. Specifically, the ratio of actual to predicted hospital mortality (A/P) has been proposed as a valid measure for comparing ICU outcomes when predicted mortality has been derived from data collected during the first 24 hours of ICU therapy with use of a severity scoring tool, APACHE II (acute physiology and chronic health evaluation). We present a comparison of mortality ratios (A/P) in four ICUs under common management, in two hospitals within a single institution. Significant differences in A/P were detected for nonoperative patients (0.99 versus 0.67;P = 0.014) between the two hospitals. This variation was traced to uneven representation of a subset of patients who had chronic health problems related to diseases that necessitated admission to the hematology-oncology or hepatology service. No differences in A/P were seen between the two hospitals for operative patients or for nonoperative patients on services other than hematology-oncology or hepatology. Thus, differences in A/P detected by using the APACHE II system not only may reside in operational factors within the ICU organization but also may be related to weaknesses in the APACHE II model to measure factors intrinsic to the disease process in some patients. We suggest that case-mix must be examined in detail before concluding that differences in A/P are caused by differences in quality of care.

Metabolic integrity of specific organ systems

This short review will address the potential uses for quantitative analyses of organ function in the critically ill patient. Multiple system failure is common in the critical-care unit, and the ability to measure reserves of organ function may enable earlier detection and treatment of this problem and provide a more accurate prognosis for such patients.

Metabolic integrity of specific organ systems

This short review will address the potential uses for quantitative analyses of organ function in the critically ill patient. Multiple system failure is common in the critical-care unit, and the ability to measure reserves of organ function may enable earlier detection and treatment of this problem and provide a more accurate prognosis for such patients.

Differences between prebreakfast and late afternoon glycemic responses to exercise in IDDM patients

Little information is available regarding the optimal timing of exercise in insulin-dependent diabetes mellitus (IDDM) patients. In this study, six IDDM patients receiving ultralente-based intensive insulin therapy were studied during 30 min of exercise (approximately 60% VO2max), before breakfast, and at 1600. On two other occasions, they were studied at rest. Plasma glucose increased from 6.7 +/- 0.4 to 9.1 +/- 0.4 mM during morning exercise (P less than 0.01). In contrast, mean plasma glucose did not change during afternoon exercise (delta = 0.3 +/- 0.5 mM, NS); however, there was a 0.3- to 1.0-mM decrease in three subjects. The observed difference in the glycemic response to exercise could not be explained on the basis of changes in plasma glucagon, growth hormone, norepinephrine, or epinephrine. Plasma cortisol was higher (P less than 0.02) in the morning than in the afternoon, and plasma free-insulin concentrations were lower (P less than 0.05). These data indicate that the risk of exercise-induced hypoglycemia is lowest before breakfast. The reason for the divergent glycemic responses to exercise is not entirely clear but may be related to the observed differences in free-insulin concentrations. Because of the lower risk of hypoglycemia, our results suggest prebreakfast exercise may be preferable for some IDDM patients receiving intensive insulin therapy. Whether these findings are relevant to patients receiving other types of insulin therapy will require further investigation.

Glucocorticosteroids increase leucine oxidation and impair leucine balance in humans

High-dose glucocorticoid treatment results in protein wasting. To determine whether such therapy affects leucine oxidation in the postabsorptive state and the disposal of dietary amino acids, eight normal subjects were studied twice in random order, once after 5 days of prednisone (20 mg three times daily) and on a second occasion without prednisone as a control. In the postabsorptive state prednisone therapy increased (P less than 0.05) plasma concentrations of leucine, alpha-ketoisocaproate, glucose, insulin, and C-peptide, as well as leucine carbon flux and oxidation calculated by means of isotope dilution techniques and [1-13C]leucine. During infusion of a chemically defined meal, total leucine carbon flux and oxidation increased similarly on both study days, but leucine oxidation was greater (P less than 0.01) during prednisone treatment; net leucine balance became positive on the control day but remained negative or zero on the prednisone study day despite higher (P less than 0.05) plasma insulin concentrations. These studies demonstrate that high-dose glucocorticoid treatment impairs the balance of the essential amino acid leucine in both the postabsorptive and absorptive states in humans.

Timing of tracheostomy in the critically ill patient

The decision for timing of tracheostomy remains controversial. The relative complication rates in two retrospective series, in which 79 and 150 critically ill patients were examined, respectively, showed increased incidence of late complications with tracheostomy and led Petty's group to conclude "The value of tracheotomy when an artificial airway is required for periods as long as 3 weeks is not supported by data obtained in this study."

Limited usefulness of quantitative culture of blood drawn through the device for diagnosis of intravascular-device-related bacteremia

The use of a differential quantitative blood culture technique (Isolator) to diagnose intravascular-device-related bacteremia (IDRB) was studied prospectively. During septic episodes in 44 patients, blood was obtained simultaneously through the suspected infected device and from a peripheral venipuncture. The blood samples were processed by the Isolator technique, which enables easy quantification of microorganisms. The cannula was removed, and its tip was cultured semiquantitatively. Of the 52 cannulas studied, 15 were the cause of IDRB, but only 7 of these showed a significantly higher bacterial count in blood obtained through the device compared with peripheral blood. The bacterial count was higher in blood drawn through the device than in peripheral blood in four of six cases that did not fulfill the definition of IDRB. Some blood cultures obtained through the device were positive despite negative cultures of peripheral blood and cannula tips (six cannulas). Quantitative blood cultures were not useful in diagnosing IDRB in this study.

Effects of basal insulin supplementation on disposition of mixed meal in obese patients with NIDDM

Basal insulin supplementation has been used as a therapy for patients with non-insulin-dependent diabetes mellitus (NIDDM) who require insulin. To determine whether basal insulin supplementation in addition to lowering postabsorptive plasma glucose concentration also improves the postprandial pattern of glucose disposition, glucose metabolism after ingestion of a solid mixed meal was assessed in obese patients with NIDDM before and after treatment with ultralente and compared with glucose metabolism observed in nondiabetic subjects. Splanchnic uptake of ingested glucose clearance was assessed by including [2-3H]glucose (a tracer that only minimally cycles through glycogen) in a solid mixed meal. Postprandial gluconeogenesis was estimated by measuring the rate of incorporation of carbon dioxide into glucose. Net glucose and lipid oxidation were measured by indirect calorimetry. Both splanchnic uptake of ingested glucose (27 +/- 1 vs. 14 +/- 2 g) and postprandial hepatic glucose release (51 +/- 5 vs. 24 +/- 3 g) were greater (P less than .001) in diabetic than in nondiabetic subjects. Although the percentage of postprandial hepatic glucose release accounted for by glucose synthesis from bicarbonate was similar in the two groups (25 +/- 2 vs. 35 +/- 5%), the absolute rate was greater in the diabetic patients (13 +/- 1 vs. 8 +/- 1 g; P less than .05). Postprandial glucose oxidation and glucose disposal (measured either isotopically or by the forearm-catheterization technique) were similar in both groups. However, total lipid oxidation was increased in the diabetic patients. (P less than .05). Two weeks of basal insulin supplementation lowered fasting glucose concentrations (from 219 +/- 22 to 144 +/- 21 mg/dl; P less than .01) and integrated postprandial glycemic response (from 814 +/- 68 to 621 +/- 72 min.mg.ml-1) but not to normal. Although circulating insulin concentrations were two- to threefold greater (P less than .02) after 3 mo of basal insulin supplementation, the postprandial pattern of glucose metabolism remained essentially the same. Basal insulin supplementation decreased (P less than .05) both splanchnic uptake of ingested glucose and hepatic glucose release. The addition of a preprandial injection of soluble insulin to basal insulin supplementation further suppressed (P less than .05) postprandial hepatic glucose release, thereby further improving postprandial glucose tolerance. These studies indicate that initial splanchnic glucose clearance, hepatic glucose release, and new glucose synthesis, as well as extrahepatic substrate metabolism, are altered in NIDDM after ingestion of a mixed meal.(ABSTRACT TRUNCATED AT 400 WORDS)

Fundamental considerations in pacing of the diaphragm for chronic ventilatory insufficiency: a multi-center study

Records were reviewed of 477 patients who had diaphragm pacemakers implanted for treatment of chronic hypoventilation. Three groups were established for comparison. (1) Center group: 165 patients operated on in six medical centers participating in a cooperative study; (2) Noncenter group, sufficient data available: 203 patients operated on by surgeons with experience limited to a few cases; (3) Nonstudy group, minimal data available: 109 patients operated on as in group 2; vital statistics only were contributed. The protocol for data gathering was comprised of 154 major variables. Basic data on age, sex, diagnosis and etiology were analyzed for homogenicity of data among the groups. A comprehensive analysis of the pacing methods, complication and results from the Center group yielded information on the early experience with diaphragm pacing important to its future application.

Nutritional assessment of intensive-care unit patients

The decision about whether to institute aggressive nutritional support, with its attendant expense and potential morbidity, in critically ill patients remains controversial. We studied numerous commonly used variables for assessment of nutrition to identify critically ill patients at increased risk for the development of infection, for becoming ventilator dependent, and for mortality. We enrolled 111 patients in this study on their third day in the intensive-care unit (ICU). No attempt was made to influence nutritional support, nor was adequacy of such support studied. Although several measurements correlated with outcome, the serum albumin correlated with number of ICU days (r = -0.38; P less than 0.001), with the number of days on a ventilator, and with the number of hospital days. It was the only measurement that correlated with the development of both a new infection (P less than 0.05) and ventilator dependency (P = 0.002). Although the use of the serum albumin concentration in this setting has limitations, it is still the best, most commonly used measurement of nutrition available.

Measurement of body potassium with a whole-body counter: relationship between lean body mass and resting energy expenditure

We conducted studies to determine whether the Mayo whole-body counter could be used to measure body potassium, and thus lean body mass (LBM), and whether moderate obesity alters resting energy expenditure when corrected for LBM. Twenty-four nonobese and 18 moderately obese adults underwent body potassium (40K) counting, as well as tritiated water space measurement and indirect calorimetry. LBM values predicted from 40K counting and tritiated water space measurements were highly correlated (P = 0.001; r = 0.88). Resting energy expenditure was closely related to LBM (P less than 0.0001; r = 0.78): kcal/day = 622 kcal + (LBM.20.0 kcal/kg LBM). In this relationship, the obese subjects did not differ from nonobese subjects. In summary, the Mayo whole-body counter can accurately measure LBM, and moderate obesity has no detectable effect on corrected resting energy expenditure.

Pulmonary alveolar phospholipoproteinosis: experience with 34 cases and a review

A retrospective review of Mayo Clinic records through 1983 revealed 84 patients (24 male and 10 female; mean age, 41 years) with the diagnosis of pulmonary alveolar phospholipoproteinosis. The major clinical features were dyspnea, cough, fever, and chest pain. Chest roentgenograms usually showed bilateral symmetric alveolar infiltrates, but asymmetric, unilateral, and chronic patchy patterns were also noted. Diagnosis was established by thoracotomy-lung biopsy in 26 patients. Histologic analysis revealed uniform filling of the alveoli by periodic acid-Schiff-positive material and maintenance of normal alveolar architecture. Electron microscopy showed enlarged alveolar macrophages with lamellar osmiophilic inclusions, dense granules, and myeloid bodies. Of the 21 patients who underwent therapeutic bronchoalveolar lavage, 13 had no recurrence of the disease during a mean follow-up of 8.8 years. In patients who underwent pulmonary function testing both before and after lavage, significant restrictive dysfunctions present before the procedure were alleviated afterward. Three deaths occurred among the 34 patients. Pulmonary alveolar phospholipoproteinosis may result from defective clearance of phospholipids by the alveolar macrophages, excessive production of phospholipids by type II pneumocytes, or both. It is likely a nonspecific response to a variety of injuries to the alveolar macrophage or type II pneumocyte or both, including exposure to certain dusts and chemicals and occurrence of hematologic diseases or infections. The uncommon occurrence of this disorder suggests individual susceptibility.

Clinical outcome of respiratory failure in patients requiring prolonged (greater than 24 hours) mechanical ventilation

Patients requiring prolonged (greater than 24 hours) mechanical ventilation have various conditions that result in respiratory failure. All patients requiring prolonged mechanical ventilation were subdivided into the following six groups: uncomplicated acute lung injury; respiratory failure complicated by multisystem failure; previous lung disease; trauma; other medical causes; and routine postoperative ventilation. During a one-year period, 327 patients required prolonged mechanical ventilation; acute lung injury and chronic obstructive pulmonary disease were the predominant conditions. Sepsis was both the major predisposing factor for and complication of acute lung injury. Mortality for patients with acute lung injury was 40 percent in the uncomplicated group and 81 percent in patients with acute lung injury complicated by multisystem failure. Acute respiratory failure in association with acute renal failure had a mortality of 89 percent. Number of organ systems involved also correlated with mortality. In patients with chronic obstructive pulmonary disease and pneumonitis or retained secretions, mortality was lower (30 percent), but a significant percentage of these patients (43 percent) became ventilator-dependent. Ventilator dependence did not significantly increase mortality during the course of respiratory failure.

Postprandial hyperglycemia in patients with noninsulin-dependent diabetes mellitus. Role of hepatic and extrahepatic tissues

Patients with noninsulin-dependent diabetes mellitus (NIDDM) have both preprandial and postprandial hyperglycemia. To determine the mechanism responsible for the postprandial hyperglycemia, insulin secretion, insulin action, and the pattern of carbohydrate metabolism after glucose ingestion were assessed in patients with NIDDM and in matched nondiabetic subjects using the dual isotope and forearm catheterization techniques. Prior to meal ingestion, hepatic glucose release was increased (P less than 0.001) in the diabetic patients measured using [2-3H] or [3-3H] glucose. After meal ingestion, patients with NIDDM had excessive rates of systemic glucose entry (1,316 +/- 56 vs. 1,018 +/- 65 mg/kg X 7 h, P less than 0.01), primarily owing to a failure to suppress adequately endogenous glucose release (680 +/- 50 vs. 470 +/- 32 mg/kg X 7 h, P less than 0.01) from its high preprandial level. Despite impaired suppression of endogenous glucose production during a hyperinsulinemic glucose clamp (P less than 0.001) and decreased postprandial C-peptide response (P less than 0.05) in NIDDM, percent suppression of hepatic glucose release after oral glucose was comparable in the diabetic and nondiabetic subjects (45 +/- 3 vs. 39 +/- 2%). Although new glucose formation from meal-derived three-carbon precursors (53 +/- 3 vs. 40 +/- 7 mg/kg X 7 h, P less than 0.05) was greater in the diabetic patients, it accounted for only a minor part of this excessive postprandial hepatic glucose release. Postprandial hyperglycemia was exacerbated by the lack of an appropriate increase in glucose uptake whether measured isotopically or by forearm glucose uptake. Thus as has been proposed for fasting hyperglycemia, excessive hepatic glucose release and impaired glucose uptake are involved in the pathogenesis of postprandial hyperglycemia in patients with NIDDM.

Calculation of mean airway pressure during mechanical ventilation in neonates

Mean airway pressure (Paw) calculated by 4 methods was compared with measured Paw, using 833 observations on 16 infants requiring constant-flow, pressure-limited mechanical ventilation. Measured Paw was most accurately predicted by determining a waveform constant for each infant every 12 h, and then using the waveform constant in a general Paw equation for the ensuing 12 h. However, this method is impractical for clinical use. A square-waveform equation more accurately predicted Paw than did triangular or sine-like waveform equations. Because there was considerable interindividual variation in the accuracy of all methods, due to different individual respiratory waveforms and waveform constants, Paw should be measured and not calculated.

Hemodynamic response to positive end-expiratory pressure following right atrium-pulmonary artery bypass (Fontan procedure)

Thirteen patients were studied in the early postoperative period to determine the hemodynamic response to increasing levels of positive end-expiratory pressure (PEEP) following right atrium-pulmonary artery bypass (Fontan procedure). Hemodynamic data and arterial oxygen and carbon dioxide tensions were measured without PEEP and with PEEP = 3, 6, 9, and 12 cm H2O. Cardiac index decreased progressively with increasing levels of PEEP compared to PEEP = 0 (cardiac index = 2.7 +/- 1.2 L/min/m2), and the decrease was significant at PEEP = 9 (cardiac index = 2.2 +/- 0.8 L/min/m2, p less than 0.05) and 12 cm H2O (cardiac index = 2.0 +/- 0.7 L/min/m2, p less than 0.05). Both arterial oxygen tension and pulmonary vascular resistance index increased significantly at all levels of PEEP studied compared to PEEP = 0. Significant positive trends were demonstrated for arterial oxygen tension and pulmonary vascular resistance index and a significant negative trend was shown for cardiac index with increasing PEEP. Heart rate, right atrial pressure, left atrial pressure, mean arterial blood pressure, and arterial carbon dioxide tension did not change significantly nor consistently with increasing PEEP. From these data it appears that PEEP is an effective means of raising arterial oxygen tension after right atrium-pulmonary artery bypass. A progressive fall in cardiac index occurs with increasing PEEP, and the fall becomes significant at PEEP greater than 6 cm H2O. The fall in cardiac index appears to be mediated by a significant rise in pulmonary vascular resistance index.

Clinical implications of variation in total venoarterial shunt fraction calculated by different methods during severe acute respiratory failure

Ventilation-perfusion imbalance is the major physiologic disturbance that produces hypoxemia in acute respiratory failure, and total venoarterial shunt fraction is frequently used as a measure of its severity. Ninety-one total venoarterial shunt fractions were calculated from 29 patients with severe acute respiratory failure. Four different methods were used for each estimation, only two of which considered the influence of cardiac output and tissue oxygen uptake. The differences among the results were statistically significant and rendered invalid those that were calculated independently of mixed venous oxygen values. Lack of uniformity of the methods that have been used for calculating shunts in respiratory failure makes it difficult to compare individual patients or groups of them from previous reports. Use of a standard method is desirable so that statistical evaluation of severity and response to treatment can be undertaken. Older data on which therapeutic decisions may be based can have misleading variability from those derived from currently accepted techniques and could appreciably influence patient care.

Outcome of anesthesia and surgery in hypothyroid patients

We retrospectively examined the outcome of anesthesia and surgery in 59 hypothyroid patients and in 59 paired euthyroid matched controls. Hypothyroid patients had more preoperative risk factors but did not differ as a group from controls with regard to duration of surgery or anesthesia, lowest temperature and BP recorded during surgery, need for vasopressors, time to extubation, fluid and electrolyte imbalances, incidence of arrhythmias, pulmonary and myocardial infarction, sepsis, need for postoperative respiratory assistance, bleeding complications, or time to hospital dismissal. Analysis of subsets of hypothyroidism (thyroxine level, less than 1.0, less than 3.0, and greater than or equal to 3.0 micrograms/dL) also failed to disclose any significant differences compared with matched controls. Among patients with mild or moderate hypothyroidism, we found no evidence to justify deferring needed surgery until the hypothyroidism has been corrected.

The hemodynamic response to dopamine and nitroprusside following right atrium-pulmonary artery bypass (Fontan procedure)

Cardiac output is critically dependent upon pulmonary vascular resistance after right atrium-pulmonary artery bypass (Fontan procedure), since there is no pulmonary ventricle in the circulation. Inotropic agents, including dopamine, may increase pulmonary vascular resistance and, therefore, might have an adverse effect on cardiac output. The present study determined the hemodynamic responses to dopamine and nitroprusside of 9 patients following right atrium-pulmonary artery bypass. Particular attention was given to effects on cardiac output (CI), pulmonary vascular resistance, and right atrial pressure (RAP). Baseline hemodynamic data were measured without drugs, with dopamine at 7.5 micrograms/kg/min, with sodium nitroprusside up to 5.0 micrograms/kg/min, and with a combination of dopamine, 7.5 micrograms/kg/min, and sodium nitroprusside, 1.0 micrograms/kg/min. Right and left atrial pressures (LAP), mean arterial blood pressure (BP), heart rate (HR), and CI were measured. Stroke volume index and pulmonary arteriolar resistance index were calculated. The increase in CI from baseline (1.98 +/- 0.86 liters per minute) was significant for infusions of dopamine (2.75 +/- 1.05, p less than 0.001), sodium nitroprusside (2.57 +/- 0.78, p less than 0.001), and both drugs (2.74 +/- 0.84, p less than 0.001). The increased CI was achieved primarily by a significant increase in HR with dopamine and by an increase in stroke volume index with sodium nitroprusside. With a similar increment in CI, the RAP was significantly decreased from baseline (21 +/- 4 torr) with sodium nitroprusside (15 +/- 3, p less than 0.001) but was unchanged with dopamine. Pulmonary arteriolar resistance index decreased significantly from baseline (375 +/- 230 dynes sec cm-5/m2) with sodium nitroprusside (169 +/- 132, p less than 0.001), and, interestingly, with dopamine as well (273 +/- 165, p less than 0.05). Both dopamine and sodium nitroprusside in these dosages have favorable effects on CI and pulmonary arteriolar resistance index in patients after right atrium-pulmonary artery bypass. Whenever feasible, sodium nitroprusside is preferred for increasing CI after such a bypass procedure, since lower RAP decreases the severity of fluid retention, ascites, and chest tube drainage.

Continuous monitoring of mixed venous oxygen saturation in critically ill patients

A new pulmonary artery balloon flow-directed catheter combines a fiberoptic photometric system for continuous display of mixed venous blood oxygen saturation (SvO2) with the capacity for hemodynamic measurements including thermodilution cardiac output estimation. This oximetry system was studied to determine its accuracy, reliability, and usefulness in the surgical intensive care unit (ICU). Twenty-two catheters were tested, but only 17 were successfully placed in 16 patients. There were technical problems associated with 10 catheters and on six occasions these necessitated the use of another catheter. The catheter values for SvO2 were closely related (r = 0.9516) to those obtained from a laboratory Co-oximeter. Continuous monitoring of SvO2 is accurate and valuable as a warning system for deterioration in cardiopulmonary function and as an indicator of the effects of various therapeutic maneuvers in critically ill patients.

Central neurogenic hyperventilation in an awake patient with brainstem astrocytoma

A patient had the rare combination of central neurogenic hyperventilation (PaCO2 of 9 torr) and a normal level of consciousness for eight days. Morphine attenuated but never corrected the hyperventilation. Experimental effects of hypocapnia, which decreases both cerebral blood flow and metabolism in humans, are at odds with the normal mentation initially seen in this patient despite her marked and persistent hypocapnia. Death occurred after progressive brainstem dysfunction. Pathological study showed a well-differentiated astrocytoma involving primarily the medulla and pons, with scattered tumor foci throughout the entire neuraxis. Possible mechanisms for central neurogenic hyperventilation are discussed briefly in relation to the pathological findings and the observed response to morphine.

Respiratory timing and depth of breathing in dogs anesthetized with halothane or enflurane

Tidal volume (VT) and inspiratory (TI) and expiratory (TE) times were measured during enflurane and halothane anesthesia in 12 prone dogs before and after bilateral vagotomy. "Elastic" loading or airway occlusion was used to obtain a VT-to-TI relationship in each state and to examine the rate of change in airway pressure. VT, TI, and TE were significantly (P less than 0.05) larger during enflurane than during halothane anesthesia, both before and after bilateral vagotomy. Before vagotomy, the rate of change in airway pressure during airway occlusion was similar for the two agents, as was an index of impedance of the respiratory system (Z'rs). Thus the difference in maximal pressure generated and in VT was most likely due to the difference in TI. Before vagotomy, TI increased as VT decreased with loading during enflurane but not halothane anesthesia, demonstrating a different effect of the two agents on the phasic vagal inspiratory inhibitory mechanism. After bilateral vagotomy, TI was unaltered during elastic loading with both agents but was still significantly longer during enflurane than halothane anesthesia. Thus it was concluded that TI was longer in the enfluraneanesthetized dogs than in the halothane-anesthetized dogs because of a different effect of these two agents on the bulbopontine "pacemaker" mechanism and not because of different effects on the phasic vagal inspiratory inhibitory mechanism.

The effect on heart rate of neuromuscular blockade reversal by pyridostigmine

Pyridostigmine without atropine, pyridostigmine with atropine or neostigmine with atropine were used to antagonise neuro-muscular blockade induced by d-tubocurarine in forty otherwise healthy, female patients recovering from gynaecological surgery. Pulse rates fell significantly (P less than 0.01, control heart rate 72 +/- 18 beats/min (M +/- SD) to 55 +/- 13 beats/min) at ten minutes after pyridostigmine (10 mg/70 kg), necessitating administration of atropine (1.25 mg/70 kg) by fifteen minutes after pyridostigmine. After an initial rise in rate, pulse rates also fell significantly (P less than 0.01, control heart rate 70 +/- 12 beats/min to 44 +/- 11 beats/min) at fifteen minutes after injection of neostigmine (2.5 mg/70 kg) with atropine (1.25 mg/70 kg). By contrast when pyridostigmine and atropine were used together, pulse rates rose and then fell, but mean values never fell below control during a twenty-minute observation period. It was concluded that pyridostigmine should not be given alone, but requires the use of atropine to prevent bradycardia. This combination may, however, provide a more stable heart rate than that seen with neostigmine and atropine in usual doses, when these drugs are used to antagonise d-tubocurarine.

Infection of pulmonary artery catheters in critically ill patients

Bacteriologic cultures were performed on the tips of pulmonary artery catheters removed from 153 critically ill patients, who had required pulmonary artery catheterization for management of hypovolemic or septicemic shock or for hemodynamic monitoring during mechanical ventilation with positive end-expiratory pressure. Positive results were obtained in 29 (19%) of the cases. Infection of indwelling pulmonary artery catheters may result from contamination during placement or removal or from transient or persistent bacteremia. Colonization was probable in 17 cases, and contamination in 12. There were no instances of sepsis definitely attributable to the catheter. Positive catheter-tip culture was associated significantly with known presence of a focus of infection before catheter insertion and with periods exceeding four days that the catheter remained in place.

Measurement of ventilatory reserve as an indicator for early extubation after cardiac operation

The decision to perform tracheal extubation in 44 patients who underwent cardiac operation was based on an assessment of mental alertness, recovery of muscle strength, hemodynamic stability, and adequacy of pulmonary gas exchange. No patients required reintubation. Concomitant measurements of vital capacity (VC) and maximal inspiratory pressure (PImax) were made before a trial of spontaneous ventilation was commenced, after 45 minutes of spontaneous ventilation, and after tracheal extubation. By generally accepted criteria, these measurements suggested the need for continuing mechanical ventilation in 14 patients at the time mechanical ventilatory support was removed and in eight patients at the time of tracheal extubation. In this study, consideration of measurements of VC and PImax would have led to longer trachael intubation, especially in those patients who were extubated within 10 hours of the completion of anesthesia.

Electrophrenic respiration: report of six cases

The development of electrophrenic respiration has permitted freedom from mechanical ventilation for patients who have irreversible respiratory failure in association with high-cervical spinal cord or brainstem lesions. There are three basic criteria for successful diaphragm pacing: (1) the need for long-term mechanical ventilatory assistance, (2) a functionally intact phrenic nerve-diaphragm axis, and (3) chest wall stability. Inability to achieve satisfactory pacing can be due to malfunction of equipment, instability of the chest wall, or inadequate neuromuscular responsiveness. These features of diaphragm pacing are exemplified in a series of six patients. Three achieved independence from mechanical ventilatory assistance with full-time phrenic pacing. In one patient, only limited electrophrenic respiration was achieved, and in another the method was entirely unsuccessful. Although functioning well, pacing systems were removed from the sixth patient because of infection. Diaphragm pacing can be a valuable form of respiratory support for carefully selected patients.

Closing capacity in awake and anesthetized-paralyzed man

Functional residual capacity (FRC), closing capacity (CC), and (FRC--CC) were determined in 61 supine patients using the 133Xe bolus test. In 28 of the 61 patients measurements were made both while the patients were awake and during anesthesia-paralysis. Both FRC and CC decreased significantly after induction of anesthesia-paralysis. The magnitude of the reduction in CC, but not of FRC, was dependent on the relationship between FRC and CC in the awake state. Patients whose FRC was larger than their CC while awake (group I) showed less decrease in CC than FRC, i.e., (FRC--CC) decreased. By contrast, those patients whose CC was larger than their FRC while awake (group II) showed a greater decrease in CC than in FRC, i.e., (FRC--CC) became less negative. The reduction in CC after induction of anesthesia-paralysis may result from an increased elastic recoil of the lung. The larger reduction in CC in group II patients may have been due to a larger increase in elastic recoil, possibly due to the development of atelactasis.

New tests for the detection of obstructive pulmonary disease

Abnormalities in small airways appear to be important in the evolution of chronic obstructive pulmonary disease. Patients with these pathologic lesions may have normal values for airway resistance and forced expiratory volume in one second. Two new tests, the closing volume (CV) and the dependence of maximal flow on density, are believed to be sensitive to abnormalities in the peripheral airways. The CV test detects an increased nonuniformity of changes in volume of pulmonary units. Reduced dependence of flow on density is believed to result from an increase in the peripheral component of the losses of driving pressure which determine maximal expiratory flow. Both tests differentiate smokers with normal conventional spirometric data from age-matched nonsmokers. Although this evidence suggests that these tests can be used to detect abnormalities in small airways, there is very little pathologic confirmation of this belief. The clinical significance of abnormalities in the results of either of these tests in an otherwise normal person has not yet been determined.

Improved oxygenation in patients with acute respiratory failure: the prone position

To assess the potential benefits of the prone position for gas exchange in patients with acute respiratory failure, we turned 6 patients from supine to prone, supporting the upper thorax and pelvis and allowing the abdomen to protrude. Arterial PO2 increased by a mean of 69 mm Hg (range, 2 to 178 mm Hg) at the same tidal volume, same inspired oxygen concentration, and same level of positive end-expiratory pressure. The maneuver made it possible to reduce the inspired oxygen concentration in 4 of the 5 patients who required mechanical ventilation of the lungs and to defer intubation in the patient who was breathing spontaneously. After subsequent turns from supine to prone, arterial PO2 increased by a mean of 35 mm Hg (range, 4 to 110 mm Hg), permitting a decrease in inspired oxygen concentration or positive end-expiratory pressure when prone (4 patients); arterial PO2 decreased in 12 of 14 instances after the patient was turned from prone to supine. No significant change in mean arterial carbon dioxide tension, respiratory frequency, or effective compliance was observed.

The effects of anesthetic drugs and disease on the chemical regulation of ventilation

The anesthesiologist uses a wide spectrum of drugs, including inhalational general anesthetics, barbiturates, benzodiazepines, narcotics analgesics and their antagonists, and neuromuscular blocking drugs. All of these drugs in sufficient dose impair the ventilatory response to chemical stimuli, and may cause inadequate gas exchange. The effect of depression of ventilatory control depends on the magnitude of depression and the coexistence of functional abnormalities in the respiratory system. The functional abnormalities are the result of preexistent pulmonary disease or other disease processes that impair respiratory function, the anticipated effects of major surgery (e.g., pulmonary resection), and the complications of anesthesia and surgery. From a functional viewpoint, the mechanisms of the effects of these disease processes on ventilatory control are: (1) interference with the neurophysiological control of automatic ventilation; (2) impairment of peripheral or central chemoreceptor function; (3) impairment of respiratory muscle function; (4) increase in the mechanical load to breathing as a result of increased resistance or decreased compliance of the respiratory system; and (5) increase in the ventilatory requirements as a result of ventilation/blood flow maldistribution, metabolic acidosis, or increased metabolic rate. As a result of current trends in the use of multiple drugs and controlled ventilation during anesthesia, the patient is at greatest risk during the early postoperative period in the recovery room. In addition to the functional abnormalities described above, the probability of impaired gas exchange and respiratory failure is increased as a result of impaired metabolism and elimination of drugs as a result of hepatic and renal insufficiency, and acute changes in acidbase status, which alter the ionization and distribution of drugs.