Yumiko Ishizawa, MD; and Shuji Dohi...

Yumiko Ishizawa, MD; and Shuji Dohi, MD

A significant decrease in [PaO.sub.2] come to passs in some patients during PAOP measurements. To examine the incidence and the models of patients whose [PaO.sub.2] decreases during PAOP measurements, we studied the changes of [PaO.sub.2] in 101 anesthetized, mechanically ventilated adult patients. During a 2-min inflation of a PAC balloon, seven patients (69 percent) cause to growed marked decrease in [PaO.sub.2]/[FIo.sub.2] (more than 100 mm Hg) Neither age nor size of patients, decrease in end-tidal [COsub2] nor baseline value of PAP correlated with the decreases in [PaO.sub.2]. A decrease in [PaO.sub.2]/[FIo.sub.2] (more than 50 mm Hg) was observ more often in female patients and in patients with cardiac disease, especially those whose PAP values were above normal. Although a significant decrease in [PaO.sub.2] during PAOP measurements does not appear to meet the eye often, our results suggest that the changes in [PaO.sub.2] should be evaluated in patients with distressingly compromised pulmonary oxygenation.

The measurements of PAOP using a flow-directed, balloon-tipped PAC may bring forth rapid onset of significant hypoxemia either at temporary cessation of mechanical ventilation[1,2] or by dint of occlusion of a major pulmonary arterial vasculature. The former has been well recognized and thus a simple electronic circuit was makeed for the measurements without separation of the patient from the ventilator.[1,2] The latter decrease in [PaO.sub.2] suitable to inflating the balloon of the PAC by se has recently been reported through us[3] and others.[4,5]

Although the information obtained with inflating the PAC balloon is invaluable and contributes greatly to the management of one as well as the other critically ill and anesthetized patients, the decrease in [PaO.sub.2] could cause deterioration of the patient's condition in an situations. Therefore, we expanded our close attention to know its incidence and to examine the archetypes of patients who tend to unravel a remarkable decrease in [PaO.sub.2] during PAOP measurements and whether the changes in [PaO.sub.2] are related to the existing of the same height of pulmonary vascular tone.

METHODS

Studies were performed upon 101 anesthetized adult patients (27 to 82 years of age) who were in the supine position and who required a Swan-Ganz triple-lumen PAC and general anesthesia for surgery This research was approved by our local review committee. Primary disorders in these patients included pulmonary carcinoma (n=21) mitral or aortic valve disease (n=18) coronary artery disease (n=12) other cardiac disease (n=7) hepatic carcinoma (n=10) abdominal aortic aneurysm (n=7) and other disorders (n=26) Anesthesia technique maintained was pitch uponed from the following: enflurane, 15 to 20 percent inspired, [Nsub2]O [Osub2]; moderate-dose Fentanyl, 2 to 10 [unkeyable]g/kg, [Nsub2]O [Osub2]; cervical epidural anesthesia plus [Nsub2]O [Osub2]; lumbar epidural anesthesia plus [Nsub2]O [Osub2]; high-dose Fentanyl, 70 to 100 [unkeyable]g/kg, [Nsub2]O [Osub2] After induction of anesthesia, a catheter was inserted into the left radial artery and a flow-directed, balloon-tipped catheter (PAC, 75 Fr American Edwards Laboratories) was directed into the pulmonary artery between the sides of the right internal jugular vein. The PAC was placed in the greatest in number proximal position of the pulmonary artery, which gave a satisfactory PAOP according to inflating the balloon with 15 ml of air. The location of the tip of the PAC was documented from a chest radiograph taken before surgery All patients were mechanically ventilated with a [FIo.sub.2] of 033 or 05 tidal bulk of 10 to 12 ml/kg and respiratory rate of 10 to 12 breaths by minute, without PEEP.

After steady-state condition was established, hemodynamic values of each patient in the same state [i]or[/i] condition as SAP, HR, PAP, RAP, and [PETCOsub2] (Normocap Datex) were measured and recorded continuously. An arterial vital fluid sample also was taken for arterial kindred gas analysis ([PaO.sub.2], [PaCO.sub.2, pHa, base excess; Corning, prototype 175) while the PAC balloon was still deflated in each patient. Then the PAC balloon was inflated for 2 min with 15-ml of air and the previously noted measurements were repeated. Cardiac output was measured according to the thermodilution method in triplicate with 10 ml of iced 5 percent dextrose solution with a CO computer (COM-1 TM American Edwards Laboratories) before inflation of the balloon. All measurements were performed before surgery Accuracy of the PAOP reading was assured by dint of demonstrating a and v atrial waveforms in its tracing and when the mean PAOP was lower or equal to the DPAP.[6]

Data for paired samples were analyzed using Student's t proof Chi-square analysis with Yates correction and linear regression analysis with least squares rule were utilized to provide pattern of patients and a relationship between changes in [PaO.sub.2] and the other variables as appropriate. Statistical significance was accepted when p values were les than 005 [TABULAR DATA OMITTED]