High prevalence of abnormal circadian blood pressure regulation and impaired glucose tolerance in adults with hypopituitarism.

Patients with hypopituitarism have an increased mortality from cardiovascular events. Reduced nocturnal blood pressure decline (non-dipping) and impaired glucose tolerance are considered as cardiovascular risk factors. To evaluate the role of these risk factors in patients with hypopituitarism we determined the 24-hour blood pressure regulation and glucose tolerance status in hypopituitary patients with and without growth hormone (GH) deficiency. Sixty-one hypopituitary subjects 5 +/- 3 years after brain surgery because of macroadenoma, 61 patients with type 2 diabetes mellitus (T2DM), and 20 healthy controls were included. Forty-four hypopituitary patients were GH deficient and 28 of these on GH treatment. Non-dipping was observed in 41 % (n = 7) of hypopituitary subjects with normal GH release, in 46 % (n = 13) of patients on GH therapy, and in 69 % (n = 11) of untreated GH deficient patients. Untreated GH deficient patients had a higher systolic night/day ratio (1.00 +/- 0.03) compared to non GH deficient (0.92 +/- 0.02; p < 0.02) and GH treated hypopituitary patients (0.93 +/- 0.01; p < 0.02). The rate of non-dipping in hypopituitarism was comparable to that in T2DM. Pathologic glucose tolerance was diagnosed in 30 % of the hypopituitary patients. The prevalence of non-dipping was independent of glucose metabolism in hypopituitary patients. All controls had normal night time blood pressure fall and glucose metabolism. The high prevalence of nocturnal non-dipping and glucose intolerance detected in this cohort might contribute to the increased cardiovascular risk of hypopituitary patients.

Monitoring of neuromuscular transmission by electromyography (II). Evoked compound EMG area, amplitude and duration compared to mechanical twitch recording during onset and recovery of pancuronium-induced blockade in the cat.

The feasibility of the compound electromyogram (EMG) was evaluated during onset and recovery from pancuronium block in the tibialis anterior muscle of ten cats. The evoked EMG area, amplitude and duration of the total response and of the major negative deflection were evaluated and compared to the mechanomyogram during 0.1 Hz and train-of-four (TOF) stimulation. EMG areas and amplitudes were found to be linearly and similarly related to the mechanomyogram during onset and recovery. Slopes of the regression lines ranged between 1.00-1.02 and between 1.10-1.22 during onset and recovery, respectively, with high individual correlation coefficients (> 0.95). The TOF ratio of the mechanomyogram was linearly related to the EMG TOF ratio during onset and to the square root of the EMG TOF ratio during recovery, with no differences between EMG areas and amplitudes, suggesting a higher initial recovery of the TOF ratio of the mechanomyogram during recovery. EMG duration increased as the level of block increased but was unsuitable for neuromuscular monitoring. Evaluation of the agreement between the two methods showed that the EMG may be from 15% below to 10% above the mechanomyogram during onset and from 40% below to 45% above the mechanomyogram during recovery, in spite of high correlation coefficients. In contrast, agreement between EMG parameters was found to be high. In conclusion, EMG is more reliable than the mechanomyogram for evaluation of neuromuscular transmission in the cat. EMG amplitudes and areas both reflect the degree of neuromuscular blockade equally well.

Evaluation of three transportable multigas anesthetic monitors: the Bruel & Kjaer Anesthetic Gas Monitor 1304, the Datex Capnomac Ultima, and the Nellcor N-2500.

We compared the performance of three newly developed anesthetic agent (AA) monitors: the Bruel & Kjaer Anesthetic Agent Monitor 1304 (BK 1304), the Datex Capnomac Ultima (ULTIMA), and the Nellcor N-2500 (N-2500). The following were investigated: the linearity and accuracy in measuring AAs, oxygen, carbon dioxide, and nitrous oxide; the linearity and accuracy during warm-up time; the effect of increasing respiratory rate on the accuracy; the consequences of a difference between monitored and delivered AA and of delivering a mixture of AAs; and, finally, the effect of water vapor and alcohol. For all three monitors we found that the accuracy in determining the respiratory and anesthetic gases was sufficient for clinical use (the N-2500 does not measure oxygen). Because of the calibration mixture supplied with the device, however, the ULTIMA recorded values that were 10 to 12% (relative) less than the AA that was present. The BK 1304 had greater accuracy at higher respiratory rates than did the other two monitors, probably favoring its use in pediatric anesthesia. The N-2500 will detect which agent (isoflurane, enflurane, or halothane) is being used, alone or in a mixture. With the two other monitors the user must define which agent is given. In some situations a difference between this and the one actually delivered can theoretically lead to an overdose of AA, with the ULTIMA up to a 14.9 minimal alveolar concentration (MAC) overdose. No interference from alcohol or water vapor in the expired air was found.(ABSTRACT TRUNCATED AT 250 WORDS)

Methods to produce calibration mixtures for anesthetic gas monitors and how to perform volumetric calculations on anesthetic gases.

A simple procedure for making calibration mixtures of oxygen and the anesthetic gases isoflurane, enflurane, and halothane is described. One to ten grams of the anesthetic substance is evaporated in a closed, 11,361-cc glass bottle filled with oxygen gas at atmospheric pressure. The carefully mixed gas is used to calibrate anesthetic gas monitors. By comparison of calculated and measured volumetric results it is shown that at atmospheric conditions the volumetric behavior of anesthetic gas mixtures can be described with reasonable accuracy using the ideal gas law. A procedure is described for calculating the deviation from ideal gas behavior in cases in which this is needed.

Monitoring of the neuromuscular transmission by electromyography (I). Stability and temperature dependence of evoked EMG response compared to mechanical twitch recordings in the cat.

The stability over time and the effect of muscle temperature change were evaluated for the evoked compound EMG and for the mechanomyogram of the tibialis anterior muscle of 7 anaesthetized cats. Both EMG areas and amplitudes were recorded. During stimulation for 3 h with 0.1 Hz (one leg) and train-of-four (TOF) (the other leg), the EMG was stable while the mechanomyogram initially increased 35-50% in the first 7-8 min and then decreased 19-22% and 5-8% over the first and second 1.5-h period, respectively. During subsequent mean muscle temperature reduction to 28.8 degrees C (0.1 Hz) and 29.7 degrees C (TOF) and rewarming, an inverse linear relationship was found between temperature and both the EMG and the mechanomyogram. During temperature reduction EMG increased about 6% (areas) and 2% (amplitudes) per degrees C. During rewarming, parameters decreased about 4.5% and 2% per degrees C, respectively (P less than 0.05 comparing EMG areas during cooling and rewarming). TOF ratio of the EMG was not affected by temperature. A very large interindividual variation was observed for the effect of temperature on the mechanomyogram with changes ranging up to 15% per degrees C for some cats. TOF ratio of the mechanomyogram was reduced from 1.02 to 0.94 at lowest muscle temperature. It is concluded that the evoked EMG may be preferable to the mechanomyogram in cat experiments investigating the neuromuscular transmission.

Elimination of waste anaesthetic gases from operating theatres.

At present, waste anaesthetic gases in the operating theatre are eliminated by room ventilation and by additional measures such as scavenging by a double-mask system and a local exhaust system. A simple technique is proposed for measuring the capture efficiency (E) of different scavenging systems. E is the ratio of the waste anaesthetic gases captured by a system to the total quantity of waste anaesthetic gases produced. In a field study on existing unmodified system, E from a phantom pollutant source was measured using a portable measuring unit designed for displaying test results on location. The pollutant source was a leaking double-mask system. When scavenging from the double-mask system, E was 98% at an exhausted airflow of 28-33 m3/h. Using a local exhaust system at an airflow of 30 m3/h, E ranged from 20 to 96%, depending on the distance between the mask and the nozzle of the exhaust system.

Noninvasive detection of sublobar bronchial obstructions. An experimental study.

The objective of this study was to develop a noninvasive radiographic method for detection of sublobar bronchial obstructions. The study was primarily done in dogs, where the obstruction was made experimentally. Inspiratory and expiratory films did not show any obvious density difference between lung parenchyma distal to the obstruction and the surrounding lung. A short application of positive end-expiratory pressure immediately followed by a forced expiration, created localized air trapping with relative radiolucency of the lung tissue distal to the obstruction. This method, easily applicable to human studies, may prove useful in early diagnosis of lung cancer with intraluminal obstruction and in detecting non-radiopaque airway foreign bodies. As an example of human application a case of lung cancer in a 57-year-old man is presented.

A new nerve stimulator (Myotest).

The Myotest is a new nerve stimulator which can give train-of-four, single twitch (1 and 10 s) and tetanic stimuli. Power is supplied by standard batteries, which allow 200 h effective use. The impulse is unipolar constant current, and the amplitude can be adjusted between 0 and 40 mA. These factors, plus the electronic control of stimulus administration, make the nerve stimulator easy to use, and facilitate the interpretation of responses, especially to tetanic and post-tetanic stimulation.

Recruiting collapsed lung through collateral channels with positive end-expiratory pressure.

We studied reinflation of collapsed parts in excised normal human lungs through both the ordinary bronchial route and through collateral channels. A model of atelectasis was made either by simple collapse or by applying a positive pressure to the pleura and a negative to the airway. Five different ventilatory patterns were used for reinflation: simulated normal breathing with and without continuous positive airway pressure (CPAP), simulated deep breathing and mechanical ventilation with and without positive end-expiratory pressure (PEEP). All methods, except normal breathing without CPAP, reinflated the collapsed part with pressures well within the range used clinically. The most effective way of re-expanding collapsed lung was the application of CPAP during simulated normal breathing or PEEP during mechanical ventilation, which required smaller transpulmonary pressure swings than the other methods. A comparison between CPAP and PEEP showed CPAP to be preferable. Collateral reinflation occurred just as readily as normal reinflation and the results suggest that collateral reinflation is the primary choice. This route of reexpansion also has a potential secretion clearing effect in that pressure is built up distal to an obstruction.

A new transducer for respiratory monitoring. A description of a hot-wire anemometer and a test procedure for general use.

A respiratory transducer based on the constant temperature anemometry principle has been developed for respiratory monitoring, and as a tool for bedside evaluation of pulmonary function. The transducer is characterized by a dynamic range from 0-2.5 1/s and an upper limiting frequency of 50 Hz. It is designed with a view to a low pressure drop of 2.5 mbar/1/s and a minimum dead space of 5 ml. The transducer has been tested using a generally applicable procedure which includes both static and dynamic test set-ups. The influence of variation in gas composition, temperature and pressure, together with variations in tidal volume and respiration rate, have been investigated. The results show that the transducer registers the immediate value of gas flow-rate with a mean error less than 5-10% in all situations which are predictable in clinical use. The mean error can be reduced to less than 5% when systematic errors are eliminated.

Resistive breathing training in severe chronic obstructive pulmonary disease. A pilot study.

We studied the effects of resistive breathing in 10 patients with long-standing, severe disabling COPD. Small increases in inspiratory resistive load resulted in diaphragmatic fatigue and failure in all patients. Fatigue was detected using the frequency spectrum analysis of an EMG signal obtained with surface electrodes. Failure was defined as an inward displacement of the abdomen during inspiration, i.e. incoordination of thoracoabdominal motion. The patients trained for one half hour daily for 4 weeks, breathing into a simple device, where they inspired against a resistive load that produced some incoordinated breaths. After 4 weeks this load was increased, if possible, and another 4-week training period started. All patients improved with training, i.e. higher resistances could be tolerated without signs of fatigue and failure. In addition most patients claimed that training had helped them in their daily living; they were able to do more without getting short of breath. The device helped expectoration, possibly owing to the effect of the small expiratory resistance.

Supraphysiological glucocorticoid treatment in hypoxic stress in dogs.

Effects of supraphysiologic methylprednisolone succinate doses on systolic time intervals, hemodynamic performance, and metabolism were studied in normal dogs during normoxia, after 60 min of normocapnic hypoxemia (PAO2 = 30 mm Hg), and reoxygenation. Bolus injections of 30 or 100 mg/kg methylprednisolone did not exert any positive inotropic action during normoxia. Cardiovascular and metabolic changes induced by hypoxia were modified only to a modest and statistically insignificant degree by sustained high levels of methylprednisolone.

Changes in systolic time intervals during stepwise increasing hypoxia.

Determinations of the reciprocal value of the square of the pre-ejection period (1/PEP-2) and the pre-ejection period/left ventricular ejection time-ratio (PEP/LVET-ratio) during stepwise increasing hypoxia showed in seven mongrel dogs in a decrease in PEP/LVET-ratio and an increase in 1/PEP-2 as an expression of a stimulation of the cardiac function. Significant changes were not observed before the arterial oxygen tension (Pao2) was below 40 mmHg. During severe hypoxia (Pao2 15-20 mmHg), some deterioration in the systolic time intervals occurs with time, but a stimulation persists at the time of death compared to the prehypoxic values.

Evaluation of impedance cardiography as a non-invasive means of measuring systolic time intervals and cardiac output.

Impedance cardiography was used for non-invasive determinations of systolic time intervals (STI) and cardiac output. The results were compared with simultaneously obtained invasive measurements of STI from central aortic pressure curves and of cardiac output using the dye-dilution technique. The study was performed on eight dogs during increasing halothane concentration. A close correlation was found between non-invasively and invasively measured left ventricular ejection time = LVET (r = 0.986) and pre-ejection period - PEP (r - 0.948). Measurements of cardiac output derived from changes in thoracic impedance were determined 1) using a fixed value of p (p - the resistivity of blood) and 2) using an individual value of p based on the actual hematocrits. When compared to cardiac outputs obtained by dye-dilution the correlation coefficients were r = 0.806 and r = 0.816, respectively. Impedance cardiography is a useful method of evaluating changes in cardiac output. The method permits simultaneous observations of changes in STI and cardiac output as an index of cardiac function.