John C. McMichan

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 (S&OV0413;O2) 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 S&OV0413;O2 were closely related (r = 0.9516) to those obtained from a laboratory Co-oximeter. Continuous monitoring of S&OV0413;O2 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.

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 offentanyl (20 μg · 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 μg · 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.RésuméOn dit que l’hydrochlorure de nalbuphine, un morphinique agonisteantagoniste, peut contrecarrer la dépression respiratoire induite par des doses moyennes de fentanyl (20 μg · kg−1) tout en préservant l’analgésie. Nous avons injecté de. la nalbuphine (0,3, 0,1 ou 0,05 mg · kg−1) dans quatre cas de résection d’anévrysme de l’aorte abdominale où on avail utilisé de bonnes doses de fentanyl (50–75 μg · kg−1). La dépression respiratoire est disparue dans chaque cas, la fréquence respiratoire passant de 10 à 23 respiration/minute, le CO2 en fin d’expiration de 7,0 ± 0,3 à 5,6 ± 0,7 pour cent et la pression inspiratoire maximale à 0,1 seconde augmentant de 4 ± 1,4 à 13 ± 2,6 mmHg. Toutefois, cela s’est accompagné d’hypertension et d’une augmentation du pouls et de la douleur à l’échelle analogique et souvent, d’agitation, de nausées, de vomissements et d’arythmies cardiaques. Dans les cas de chirurgie de l’aorte abdominale où on a utilisé du fentanyl à dose élevée, il n’est pas approprié d’employer la nalbuphine pour favoriser une extubation précoce de la trachée.

Guide wire-sheath technique for pulmonary artery catheterization and central vein cannulation.

The combination of a spring guide wire with a sheath introducer system has been successfully used for the routine placement of pulmonary artery and central venous catheters. The method, which is described is simple, quick, and safe. It is applicable to the initial placement of the catheter, to any necessary alterations in its position and to its eventual replacement with a central venous cannula.

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.

Assessment of sterility of pulmonary arterial catheter sheaths

Since its description in 1970, the flow-directed balloon-tipped pulmonary arterial catheter (PAC) has become a cornerstone for hemodynamic monitoring in the intensive care unit. As the PAC is used more frequently, a subset of patients arises in which, after an initial monitoring success, the catheter fails to wedge. The best way to reposition the catheter in this circumstance is the subject of debate (1). Some physicians think that the catheter should not be advanced after the initial placement because of the possibility of introducing into the patient a part of the catheter that is no longer sterile (2). In an attempt to safely manipulate the PAC after placement, Kopman and Sandza (3 ) developed a plastic sleeve that was put over the catheter at the time of insertion. In 10 patients the sleeve was reported to preserve the sterility of that portion of the catheter that remained outside the patient but within the sheath. Several manufacturers now produce such ”contamination sheaths” that are promoted as a means of maintaining the sterility of the catheter and decreasing the infection rates of these catheters. In their initial study, Kopman and Sandza failed to report whether any of the catheters were manipulated within the sheath prior to the cultures being obtained. Furthermore, swabbing the PAC, as they did, may not be the most effective way to assess the sterilitv of the catheter. Finally, the number of catheters s.tudied may have been too small to adequately detect contamination. The purpose of this study then was to assess, by two different techniques, whether a currently marketed contamination sheath does indeed safeguard the sterility of the part of the PAC that lies outside the patient.

Percutaneous Transtracheal Ventilation Simplified

Percutaneous Transtracheal Ventilation Simplified Peter Cameron;John McMichan; Anesthesia & Analgesia