Laryngeal mask airway in anesthetic care: clinical cases and discussion.

The laryngeal mask airway (LMA) is rapidly becoming an essential tool in the anesthetist's armamentarium for airway management. Approved for use in the United States in 1992, the LMA has several uses, notably anesthesia traditionally administered by mask. It can be used in a variety of clinical situations including prolonged surgery, management of the difficult airway, and control of the airway in emergency situations. Techniques are described for the use and maintenance of the LMA. Two illustrative clinical cases are presented.

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.

Side effects of nalbuphine while reversing opioid-induced respiratory depression: report of four cases.

Nalbuphine hydrochloride, an agonist-antagonist opioid, is reported to reverse the respiratory depression of moderate doses of fentanyl (20 micrograms.kg-1) and still provide good analgesia. We report four patients having abdominal aortic aneurysm repair in which we attempted to reverse the respiratory depression of large doses of fentanyl (50-75 micrograms.kg-1) with nalbuphine (0.3 mg.kg-1, 0.1 mg.kg-1 or 0.05 mg.kg-1). Nalbuphine reversed respiratory depression in all four patients and the respiratory rate increased from 10 to 23 breaths per minute, end-tidal CO2 decreased from 7.0 +/- 0.3 per cent to 5.6 +/- 0.7 per cent, and peak inspiratory pressure after 0.1 seconds increased from 4 +/- 1.4 to 13 +/- 2.6 mmHg. However, hypertension, increased heart rate, and significant increase in analogue pain scores accompanied reversal of respiratory depression. Agitation, nausea, vomiting, and cardiac dysrhythmias also were observed frequently. We do not recommend the use of nalbuphine to facilitate early extubation of the trachea after large doses of fentanyl for abdominal aortic surgery.

Catheter-induced lesions of the right side of the heart. A one-year prospective study of 141 autopsies.

We examined prospectively for one year the hearts from 141 consecutive autopsy cases in which a central catheter was present at the time of death. Three deaths were attributable to catheter use, two to perforation. Furthermore, mural thrombi were present in 33 (33%) of 99 patients with pulmonary arterial catheters and in 12 (29%) of 42 patients with central venous catheters. The incidence of pulmonary emboli or bacteremia was no greater in patients with thrombi than in those without. The use of central catheters may thus be complicated by perforation or the development of mural thrombi. Although the thrombi may embolize or may become infected, the incidence and clinical significance appear to be low. The incidence of catheter-related deaths in our autopsy population does not necessarily reflect the incidence in a population of living patients.

Insertion of pulmonary artery catheters--a comparison of fiberoptic and nonfiberoptic catheters.

Fiberoptic (FO) pulmonary artery catheters were compared prospectively to the conventional type to observe the degree of insertion difficulty, the rate of complications, and the amount of technical faults. The inclusion of fiberoptic bundles in pulmonary artery catheters potentially altered their stiffness, thus influencing their passage from the central venous system to the pulmonary artery. Records were kept on the insertion of 287 consecutive pulmonary artery catheters, 44 of which contained fiberoptics for the continuous measurement of mixed-venous oxygen saturation ( SvO2 ). Results showed that the FO catheter was similar to the nonfiberoptic ( NFO ) model and could thus serve as an alternative to the conventional catheter when continuous monitoring of SvO2 was indicated.

Continuous monitoring of mixed venous oxygen saturation.

Continuous monitoring of arterial oxygen tension is not sufficiently accurate for practical use in adults. Because of the shape of the hemoglobin dissociation curve, fluctuations at higher levels of oxygen tension are not reflected by corresponding changes in saturation; consequently, measurement of saturation at these levels also lacks sensitivity in detecting physiologic instability. However, at the lower levels of oxygen present in venous blood, a linear relationship exists between saturation and tension. The use of improved fiberoptic oximetry systems in conventional pulmonary artery flotation catheters has made the bedside application of this relationship of practical value in the continuous assessment of mixed venous oxygen saturation. Our own experience with it extends to more than 630 patients. Changes predictive of cardiorespiratory instability and instantaneous response to nursing or therapeutic maneuvers make this technique highly effective in the care of the critically ill.

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.

Acute toxicity after excessive ingestion of colchicine.

A 15-year-old girl was admitted to a hospital in Rochester, Minnesota, 40 hours after the ingestion of 24 mg of colchicine. She suffered severe cardiovascular, pulmonary, hematologic, gastrointestinal, renal, metabolic, and neuromuscular complications but ultimately survived. Colchicine is an uncommon but potentially serious source of acute toxicity. An overdose warrants prompt attention in a setting where intensive medical support is available.

Avoidance of aggravated hypoxemia during measurement of mean pulmonary artery wedge pressure in ARDS.

A marked drop occurs in mixed venous oxygen saturation during temporary interruption of mechanical ventilation. To avoid this potentially dangerous problem and eliminate possible errors induced by associated hemodynamic changes, a simple electronic circuit was constructed for measurement of mean pulmonary artery wedge pressure without separation of the patient from the ventilator. Its 12-second time constant was sufficient to cover two to four respiratory cycles. In 50 ventilator-supported patients with the adult respiratory distress syndrome, it was shown that the value obtained from the circuit was not different from the instantaneous value obtained at the end of expiration during temporary cessation of mechanical ventilation, but was different from the pulmonary artery diastolic pressure. The circuit value was not affected by positive end-expiratory pressures up to 10 cm H2O. The method is sufficiently accurate for its intended purpose, improves the care of these severely-ill patients, and can be safely used without a physician being present.

Respiratory failure in Guillain-Barré syndrome: a 6-year experience.

Seventy-nine patients with acute Guillain-Barré syndrome were seen during a 6-year period. Twenty-one were admitted to a respiratory intensive care unit, where they remained for 58 +/- 26 days (range 14 to 105 days). Thirteen patients required nasotracheal intubation followed by tracheostomy and mechanical ventilation. The tracheostomy tube was in place for an average of 50 +/- 27 days (range 10 to 104 days). Four patients had complications of tracheostomy; two of these were significant, and one of them led directly to the patient's death. There were no complications due to mechanical ventilation, from which 11 patients were successfully weaned after a mean period of 37 +/- 29 days (range 7 to 93 days). Three of the 79 patients (3.8%) died of complications of their disease or its treatment. Respiratory failure in this condition is protracted and its complications are mainly those of prolonged endotracheal intubation with a tracheostomy tube.

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.

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.

Pulmonary dysfunction following traumatic quadriplegia. Recognition, prevention, and treatment.

A prospective study of the pulmonary complications occurring in 22 consecutive patients admitted to hospital within 24 hours after acute traumatic quadriplegia was compared with the findings of a retrospective survey of 22 comparable patients. Patients in the prospective group received therapy designed to prevent or reverse secretion retention. All patients in this group survived. In the retrospective group there were nine deaths; pulmonary complications and the need for tracheal intubation and mechanical ventilation were three times more frequent. Serial pulmonary function testing in the prospective group demonstrated a greater compromise of expiration than inspiration and progressive improvement in diaphragm function with time. It is concluded that vigorous pulmonary therapy in the prospective group was associated with increased survival, a decreased incidence of pulmonary complications, and a decreased need for ventilatory support.

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.