Postoperative Gas Exchange Research Articles

Polysomnography parameters as predictors of respiratory adverse events following adenotonsillectomy in children

The first-line treatment of obstructive sleep apnea syndrome in children is adenotonsillectomy, but this may result in perioperative respiratory adverse events (PRAEs). The primary aim of this study is to examine whether the McGill oximetry score (MOS) and other polysomnography parameters can predict major PRAEs following adenotonsillectomy. We secondarily evaluated the MOS interrater reliability and correlation with other polysomnography parameters. This retrospective study included all children aged 0-18 years who underwent preoperative polysomnography between June 2010 and January 2016 prior to adenotonsillectomy at a tertiary pediatric institution. Oximetries from polysomnograms were assigned an MOS. Univariable and multivariable models for prediction of major PRAEs were constructed. MOS was correlated with polysomnography parameters and interrater reliability was evaluated. This study included 106 children; 15 had a major PRAE. A multivariable prediction model that combined MOS and age showed evidence for the ability to predict major PRAEs with an area under the receiver operating characteristic curve of 0.68 (95% confidence interval: 0.52, 0.84), whereby increased MOS and younger age were associated with PRAEs, but apnea-hypopnea index was not. MOS had excellent interrater reliability (κ = 0.95) and was highly correlated with oxygen saturation nadir and cumulative time percentage with oxygen saturation less than 90%. A prediction model including MOS and age may predict PRAEs following adenotonsillectomy. This suggests that nocturnal oximetry provides the most essential information of polysomnography measures to direct postoperative monitoring following adenotonsillectomy. Xiao L, Barrowman N, Momoli F, etal. Polysomnography parameters as predictors of respiratory adverse events following adenotonsillectomy in children. J Clin Sleep Med. 2021;17(11):2215-2223.

Effects of lowering inspiratory oxygen fraction during microvascular decompression on postoperative gas exchange: A pre-post study.

BackgroundDespite many previous studies, the optimal oxygen fraction during general anesthesia remains controversial. This study aimed to evaluate the effects of lowering intraoperative fraction of inspired oxygen on postoperative gas exchange in patients undergoing microvascular decompression (MVD).MethodsWe conducted a pre-post study to compare postoperative gas exchange with different intraoperative oxygen fractions. From April 2010 to June 2017, 1456 consecutive patients who underwent MVD were enrolled. Starting in January 2014, routine oxygen fraction was lowered from 1.0 to 0.3 during anesthetic induction/awakening and from 0.5 to 0.3 during anesthetic maintenance. Postoperative gas exchange, presented as the minimum value of PaO2/FIO2 ratio within 48 hours, were compared along with adverse events.ResultsAmong 1456 patients, 623 (42.8%) patients were stratified into group H (high FIO2) and 833 (57.2%) patients into group L (low FIO2). Intraoperative positive end-expiratory pressure was used in 126 (15.1%) patients in group H and 90 (14.4%) patients in group L (p = 0.77).The minimum value of PaO2/ FIO2 ratio within 48 hours after surgery was significantly greater in the group L (226.13 vs. 323.12; p < 0.001) without increasing any adverse events.ConclusionIn patients undergoing MVD, lowering routine FIO2 and avoiding 100% O2 improved postoperative gas exchange.

Remote Ischemic Preconditioning Decreases Oxidative Lung Damage After Pulmonary Lobectomy: A Single-Center Randomized, Double-Blind, Controlled Trial.

During lobectomy in patients with lung cancer, the operated lung is often collapsed and hypoperfused. Ischemia/reperfusion injury may then occur when the lung is re-expanded. We hypothesized that remote ischemic preconditioning (RIPC) would decrease oxidative lung damage and improve gas exchange in the postoperative period. We conducted a single-center, randomized, double-blind trial in patients with nonsmall cell lung cancer undergoing elective lung lobectomy. Fifty-three patients were randomized to receive limb RIPC immediately after anesthesia induction (3 cycles: 5 minutes ischemia/5 minutes reperfusion induced by an ischemia cuff applied on the thigh) and/or control therapy without RIPC. Oxidative stress markers were measured in exhaled breath condensate (EBC) and arterial blood immediately after anesthesia induction and before RIPC and surgery (T0, baseline); during operated lung collapse, immediately before resuming two-lung ventilation (TLV) (T1); immediately after resuming TLV (T2); and 120 minutes after resuming TLV (T3). The primary outcome was 8-isoprostane levels in EBC at T1, T2, and T3. Secondary outcomes included the following: NO2+NO3, H2O2 levels, and pH in EBC and in blood (8-isoprostane, NO2+NO3) and pulmonary gas exchange variables (PaO2/FiO2, A-aDO2, a/A ratio, and respiratory index). Patients subjected to RIPC had lower EBC 8-isoprostane levels when compared with controls at T1, T2, and T3 (differences between means and 95% confidence intervals): -15.3 (5.8-24.8), P = .002; -20.0 (5.5-34.5), P = .008; and -10.4 (2.5-18.3), P = .011, respectively. In the RIPC group, EBC NO2+NO3 and H2O2 levels were also lower than in controls at T2 and T1-T3, respectively (all P < .05). Blood levels of 8-isoprostane and NO2+NO3 were lower in the RIPC group at T2 (P < .05). The RIPC group had better PaO2/FiO2 compared with controls at 2 hours, 8 hours, and 24 hours after lobectomy in 95% confidence intervals for differences between means: 78 (10-146), 66 (14-118), and 58 (12-104), respectively. Limb RIPC decreased EBC 8-isoprostane levels and other oxidative lung injury markers during lung lobectomy. RIPC also improved postoperative gas exchange as measured by PaO2/FiO2 ratio.

Unexplained cyanosis revealing hepatopulmonary syndrome in a child with asymptomatic congenital hepatic fibrosis: a case report

IntroductionHepatopulmonary syndrome is a rare disease that affects patients of any age with acute or chronic liver disease. Liver transplantation is the only therapeutic option of proved benefit, and can result in substantial improvement or total improvement in postoperative gas exchange abnormalities.Case presentationWe report the case of a cyanotic 13-year-old Pakistani boy whose chest computed tomography scan showed normal lung fields and mediastinum with incidental findings of a prominent liver surface with a collateral vein connecting a portal cavernoma to the dilated terminal inferior vena cava. Sonography of his abdomen along with a portal venous Doppler study showed multiple collateral veins replacing the portal vein. A liver biopsy revealed congenital hepatic fibrosis. Contrast-enhanced echocardiography with agitated saline and a 99m Technetium-macroaggregated albumin perfusion lung scan confirmed intrapulmonary shunting. The patient underwent a successful liver transplantation that resulted in improved gas exchange.ConclusionsHepatopulmonary syndrome should be included in the differential diagnosis of unexplained hypoxemia with an evaluation of possible portal hypertension or liver disease even in the absence of other clinical symptoms.

Mini-extracorporeal circulation minimizes coagulation abnormalities and ameliorates pulmonary outcome in coronary artery bypass grafting surgery

Hemostasis is impaired during CABG and coagulation abnormalities often result in clinically relevant organ dysfunctions, eventually increasing morbidity and mortality rates. Fifteen consecutive patients with coronary artery disease submitted to conventional extracorporeal circulation (cECC) have been compared with 15 matched patients, using mini-ECC (MECC). Postoperative lung function was evaluated according to gas exchange, intubation time and lung injury score. In the MECC group, thrombin-antithrombin complex levels (TaTc), prothrombin fragments (PF1+2) formation and thromboelastography (TEG) clotting times were lower compared to the cECC group (p=0.002 and p<0.001, respectively) whereas postoperative blood loss was higher in the cECC group (p=0.030) and more patients required blood transfusion (p=0.020). In the MECC group, postoperative gas exchange values were better, intubation time shorter and lung injury score lower (p<0.001 for all comparisons). Our study suggests that MECC induces less coagulation disorders, leading to lower postoperative blood loss and better postoperative lung function. This approach may be advantageous in high-risk patients.

Is there benefit in smoking cessation prior to cardiac surgery?

A best evidence topic was written according to a structured protocol. The question addressed was whether smoking cessation prior to cardiac surgery would result in a greater freedom from postoperative complications. A total of 564 papers were found using the reported searches, of which five represented the best evidence to answer the clinical question. The authors, date, journal, study type, population, main outcome measures and results are tabulated. Reported measures were operative mortality, pulmonary complications, infective complications, neurological complications, transfusion requirements, duration of ventilation, intensive care unit and hospital stay, intensive care unit re-admission, postoperative gas exchange parameters and postoperative pulmonary function. The largest of the best evidence studies demonstrated a significant reduction in pulmonary complications in non-smokers (P < 0.001); however, there was an increased requirement for transfusion in this cohort (P = 0.002). There were non-significant reductions in neurological complications, infective complications and re-admissions to intensive care. Another large cohort study demonstrated significant reductions in non-smokers in mortality (P < 0.0001), pulmonary complications (P = 0.0002), infection (P < 0.0007), intensive care unit re-admission (P = 0.0002), duration of mechanical ventilation (P = 0.026) and intensive care unit stay (P = 0.002). A larger cohort study again demonstrated significant reductions in non-smokers in pulmonary complications (P < 0.002), duration of mechanical ventilation (P < 0.012) and intensive care unit stay (P < 0.005). A smaller prospective cohort study reported significantly raised PaO(2) (P = 0.0091) and reduced PaCO(2) (P < 0.0001) levels in the non-smokers as well as improved FVC and FEV(1) (P < 0.0001). There were also reductions in duration of intubation (P < 0.0001), intensive care unit stay (P < 0.0001) and hospital stay (P < 0.0013). Another small cohort study reporting outcomes of heart transplantation demonstrated significant improvement in non-smokers in terms of survival (P = 0.031), duration of intubation (P = 0.05) and intensive care unit stay (P = 0.021). We conclude that there is strong evidence demonstrating superior outcomes in non-smokers following cardiac surgery and advocate the necessity of smoking cessation as soon as possible prior to cardiac surgery.

EZ - PAP in the Postoperative Period: A Pilot Study

Induction of general anesthesia impairs gas exchange in the lungs, persists postoperatively, and may contribute to significant postoperative morbidity and health care cost. Laparoscopic surgery has been associated with an increased incidence of ventilatory complications. Multiple factors, including cardiac and respiratory comorbidities, surgical procedure and incision site, and body habitus contribute to these risks. The purpose of this study is to compare the effect of EZ PAP (a noninvasive positive airway pressure device) versus passive oxygen delivery via nasal cannula (conventional postoperative care) on postoperative ventilator status in patients scheduled to undergo laparoscopic surgery. A theoretical framework for ventilatory status with an emphasis on assessment of the patient with potential postoperative gas exchange impairment guided this study. Patients with body mass index (BMI) ≥ 35 having non-emergent laparoscopic abdominal surgery were recruited and randomly assigned to either the EZ PAP or the control group. Noninvasive pulse oximetry, capnography, oxygen liter flow, EZ PAP pressure, vital signs, and post operative opioids use were recorded at baseline, initiation of EZ PAP, 1 hour, 2 hours and 4 hours postoperatively.

Alveolar Recruitment Strategy During Cardiopulmonary Bypass Does Not Improve Postoperative Gas Exchange and Lung Function

Pulmonary dysfunction with impairment of lung function and oxygenation is one of the most serious problems in the early postoperative period after cardiac surgery. In this study we investigated the effect of alveolar recruitment strategy during cardiopulmonary bypass on postoperative gas exchange and lung function. This prospective randomized study included 32 patients undergoing elective myocardial revascularization with cardiopulmonary bypass. In 16 patients 5 cm H(2)O of positive end-expiratory pressure was applied after intubation and maintained until extubation (Group I). In the other 16 patients (group II) a positive end expiratory pressure (PEEP) of 5 cm H(2)O was maintained as well but was increased to 14 cm H(2)O every 20 min for 2 min during cross clamp. Measurements were taken preoperatively, before skin incision, before and after (3, 24, 48 h) cardiopulmonary bypass and before discharge (6th postoperative day). Postoperative gas exchange, extravascular lung water and lung function showed no significant difference between the groups. Postoperative pulmonary function variables were lower in both groups compared to baseline values. In patients with normal preoperative pulmonary function, application of an alveolar recruitment strategy during cardiopulmonary bypass does not improve postoperative gas exchange and lung function after cardiac surgery.

Pulmonary injury after cardiopulmonary bypass: Beneficial effects of low-frequency mechanical ventilation

Pulmonary dysfunction is a frequent postoperative complication after cardiac surgery with cardiopulmonary bypass, and atelectasis is thought to be one of the main causes. The aim of this study was to evaluate whether low-frequency ventilation and continuous positive airway pressure during cardiopulmonary bypass reduce postcardiopulmonary bypass lung injury. Eighteen Yorkshire pigs were subjected to 120 minutes of cardiopulmonary bypass (1 hour of cardioplegic arrest) followed by 90 minutes of recovery before being sacrificed. Six animals served as control with the endotracheal tube open to atmosphere during cardiopulmonary bypass. The remaining animals were divided into 2 groups of 6: One group received continuous positive airway pressure of 5 cm H(2)O, and one group received low-frequency ventilation (5/minutes) during cardiopulmonary bypass. Lung tissue biopsy and bronchoalveolar lavage samples were obtained before and 90 minutes after discontinuation of cardiopulmonary bypass for measurement of adenine nucleotide (adenosine-5'-triphosphate, adenosine diphosphate, adenosine monophosphate), lactate dehydrogenase, DNA levels, and histology. Hemodynamic data and arterial blood gases were also collected through the study. The hemodynamic parameters were similar in the 3 groups. After cardiopulmonary bypass, the low-frequency ventilation group showed significantly better oxygen tension and alveolar arterial oxygen gradient, higher adenine nucleotide, lower lactate dehydrogenase levels, and reduced histologic damage in lung biopsy, as well as lower DNA levels in bronchoalveolar lavage compared with the control group. The continuous positive airway pressure group showed only significantly reduced lactate dehydrogenase levels compared with control. Low-frequency ventilation during cardiopulmonary bypass in a pig experimental model reduces tissue metabolic and histologic damage in the lungs and is associated with improved postoperative gas exchange.

CPAP at 10 cm H2O during cardiopulmonary bypass does not improve postoperative gas exchange

To compare postoperative (PO) pulmonary gas exchange indexes in patients submitted to myocardial revascularization (MR) with or without the application of continuous positive airway pressure (CPAP) during cardiopulmonary bypass (CPB). Thirty adult patients submitted to MR with CPB between March and September 2005 were randomly allocated to two groups: CPAP (n=15), patients that received CPAP at 10 cm H2O during CPB, and control (n=15), patients that didn't receive CPAP. PaO(2)/FiO2 and P(A-a)O2 were analyzed at four moments: Pre (just before CPB, with FiO2=1.0 ); Post (30 min post-CPB, with FiO2=1.0); immediate PO period (12h post-surgery, with FiO2=0.4 by using a Venturi(R) facial mask) and first PO day (24h post-surgery, with FiO2=0.5 by a facial mask). PaO2/FiO2 and P(A-a)O2 tend to get significantly worst as time elapsed during the postoperative period in both groups, but no differences were observed between them at any moment. When PaO2/FiO2 was subdivided into three categories, a greater prevalence of patients with values between 200 mmHg and 300 mmHg were observed in CPAP group only at moment Post (30 min post-CPB; p = 0.02). CPAP at 10 cm H2O administered during CPB, although had lightly improved PaO2/FiO2 at 30 minutes post-CPB, had no significant sustained effect on postoperative pulmonary gas exchange. We concluded that in patients submitted to MR, application of 10 cmH2O CPAP does not improve postoperative pulmonary gas exchange.

Pulmonary artery perfusion during cardiopulmonary bypass improves postoperative gas exchange in a swine model

Pulmonary artery perfusion during cardiopulmonary bypass improves postoperative gas exchange in a swine model

Administration of oxygen before tracheal extubation worsens gas exchange after general anesthesia in a pig model.

Administration of 100% oxygen before tracheal extubation is common clinical practice. We determined the effect of this technique on postoperative gas exchange in a porcine model using the multiple inert gas elimination technique. After general anesthesia with mechanical ventilation for a period of 30 min (inspiratory fraction of oxygen of 0.3), anesthesia was discontinued, and the pigs were randomized to an inspiratory fraction of oxygen of 0.3 or 1.0 until they could be safely extubated. Thirty minutes after extubation while breathing air, blood flow to poorly ventilated units had significantly increased in pigs that had been administered 100% oxygen as compared with those receiving 30% oxygen (17% +/- 15% versus 7% +/- 5%; P = 0.009). We conclude that exposure to 100% oxygen before extubation may cause an undesirable alteration in gas exchange. Blood flow to lung units with a low V(A)/Q ratio was significantly larger in pigs that had been exposed to 100% oxygen before extubation as compared with those exposed to 30% oxygen before extubation.

The automatic lung parameter estimator (ALPE) system: non-invasive estimation of pulmonary gas exchange parameters in 10-15 minutes.

Clinical measurements of pulmonary gas exchange abnormalities might help prevent hypoxaemia and be useful in monitoring the effects of therapy. In clinical practice single parameters are often used to describe the abnormality e.g., the "effective shunt." A single parameter description is often insufficient, lumping the effects of several abnormalities. A more detailed picture can be obtained from experiments where FiO2 is varied and two parameters estimated. These experiments have previously taken 30-40 minutes to complete, making them inappropriate for routine clinical use. However with automation of data collection and parameter estimation, the experimental time can be reduced to 10-15 minutes. A system has been built for non-invasive, Automatic, Lung Parameter Estimation (ALPE). This system consists of a ventilator, a gas analyser with pulse oximeter, and a computer. Computer programs control the experimental procedure, collect data from the ventilator and gas analyser, and estimate pulmonary gas exchange parameters. Use of the ALPE system, i.e. in estimating gas exchange parameters and reducing experimental time, has been tested on five normal subjects, two patients before and during diuretic therapy, and on 50 occasions in patients before and after surgical intervention. The ALPE system provides estimation of pulmonary gas exchange parameters from a simple, clinical, non-invasive procedure, automatically and quickly. For normal subjects and in patients receiving diuretic therapy, data collection by clinicians familiar with ALPE took (mean +/- SD) 13 min 40 sec +/- 1 min 23 sec. For studies on patients before and after surgery, data collection by an intensive care nurse took (mean +/- SD) 10 min 47 sec +/- 2 min 14 sec. Parameter estimates were: for normal subjects, shunt = 4.95% +/- 2.64% and fA2 = 0.89 +/- 0.01; for patients with heart failure prior to diuretic therapy, patient 1, shunt = 11.50% fA2 = 0.41, patient 2 shunt = 11.61% fA2 = 0.55; and during therapy: patient 1, shunt = 11.51% fA2 = 0.71, patient 2, shunt = 11.22% fA2 = 0.49. The ALPE system provides quick, non-invasive estimation of pulmonary gas exchange parameters and may have several clinical applications. These include, monitoring pulmonary gas exchange abnormalities in the ICU, assessing post-operative gas exchange abnormalities, and titrating diuretic therapy in patients with heart failure.

Continuous Positive Airway Pressure at 10 cm H2O During Cardiopulmonary Bypass Improves Postoperative Gas Exchange

Continuous Positive Airway Pressure at 10 cm H2O During Cardiopulmonary Bypass Improves Postoperative Gas Exchange

Continuous Positive Airway Pressure at 10 cm H2O During Cardiopulmonary Bypass Improves Postoperative Gas Exchange

Postbypass pulmonary dysfunction including atelectasis and increased shunting is a common problem in the intensive care unit. Negative net fluid balance and continuous positive airway pressure (CPAP) have been used to reduce the adverse effects of cardiopulmonary bypass (CPB) on the lung. To determine whether CPAP at 10 cm H2O during CPB results in improved postoperative gas exchange in comparison with deflated lungs during CPB, we examined 14 patients scheduled for elective cardiac surgery. Seven patients received CPAP at 10 cm H2O during CPB, and in the other seven patients, the lungs were open to the atmosphere (control). Measurements were taken before and after CPB, after thoracic closure, and 4 h after CPB in the intensive care unit. CPAP at 10 cm H2O resulted in significantly more perfusion of lung areas with a normal ventilation/perfusion distribution (VA/Q) and significantly less shunt and low VA/Q perfusion 4 h after CPB in comparison with the control group. Consequently, arterial oxygen partial pressure was significantly higher and alveolar-arterial oxygen partial pressure difference was significantly smaller. We conclude that CPAP at 10 cm H2O during CPB is a simple maneuver that improves postoperative gas exchange. Implications Inflation of the lungs at a pressure of 10 cm H2O as compared with leaving the lungs deflated during cardiopulmonary bypass was examined. Lung inflation during bypass resulted in significantly improved postoperative gas exchange.

Respiratory dysfunction after cardiac surgery: effects of avoiding cardiopulmonary bypass and the use of bilateral internal mammary arteries.

The quantitative contribution of cardiopulmonary bypass (CPB) to respiratory dysfunction after cardiac surgery is not documented and the effect of the use of bilateral internal mammary artery (IMA) grafts is not clear. One hundred and seventy-five patients undergoing CABG with (CPB, n=150) and without (NOCPB, n=25) CPB were studied. PMN elastase (as a marker of the systemic inflammatory response) and serial arterial oxygen (paO(2)) and carbon dioxide (paCO(2)) tension, alveolar arterial oxygen (AaO(2)) gradient and percent saturation were measured. The CPB group was subdivided into three groups by the number of IMA grafts used: 0IMA (n=12), 1IMA (n=82) and 2IMA (n=51). The NOCPB group was younger, had significantly better preoperative blood gases, received fewer grafts and had lower PMN elastase levels than the CPB group. In both groups maximum respiratory dysfunction occurred at 48 h (paO(2), percentage saturation and Aa gradient all P<0.001 versus baseline) with partial recovery by 5 days. The percentage decline and subsequent recovery in all blood gas parameters was near identical in the CPB and NOCPB groups. Amongst the three IMA groups the percentage changes in all blood gas parameters were similar, as was the duration of postoperative ventilation and time to discharge. There was no correlation between blood gas parameters at 48 h with age, CPB time, blood loss, duration of ventilation or peak PMN elastase level. Changes in postoperative gas exchange are similar in patients undergoing CABG with and without CPB even although PMN elastase levels indicate that CPB produces a more marked inflammatory response. The use of 2IMA compared with 1IMA does not increase respiratory dysfunction.

Pulmonary abnormalities after coronary arterial bypass grafting operation: cardiopulmonary bypass versus mechanical stabilization

Background. Cardiopulmonary bypass has been implicated in causing poor pulmonary gas exchange postoperatively in patients undergoing coronary artery bypass grafting procedures. This randomized prospective study was conducted to determine whether patients undergoing coronary artery bypass grafting operations using cardiac stabilization and thereby avoiding cardiopulmonary bypass will have improved pulmonary function postoperatively.Methods. Fifty-eight patients were randomized to one of two groups: coronary artery bypass grafting operation with stabilization or coronary artery bypass grafting operation with cardiopulmonary bypass. Preoperative and postoperative pulmonary gas exchange measurements were performed on intubated patients, including the arterial partial pressure of oxygen on 100% inspired oxygen, the alveolar–arterial oxygen gradient, and pulmonary shunt. Static and dynamic lung compliance measurements were performed postoperatively. Hemodynamic variables (including creatine kinase-MB and troponin levels), intubation time, postoperative bleeding, and blood transfusions were compared.Results. Both study groups had a large decrease in arterial partial pressure of oxygen on 100% inspired oxygen (p < 0.0001) and a significant postoperative increase in the alveolar–arterial oxygen gradient (p < 0.0001). There was no statistical difference in the postoperative gas exchange between the two groups; however, the postoperative pulmonary shunt was significantly better in the stabilization group (24% versus 31%, p = 0.03). The patients were extubated in the intensive care unit earlier in the stabilization group (8.2 hours versus 9.2 hours, not significant). The mean static and dynamic lung compliance postoperatively was lower in the stabilization group, although not statistically significant (p = 0.06).Conclusions. Coronary artery bypass grafting operation using cardiac stabilization technique is safe and avoids the risk of cardiopulmonary bypass. The pulmonary gas exchange postoperatively is comparable to standard cardiopulmonary bypass procedures, but a reduced postoperative pulmonary shunt was seen in the stabilization group.

Maximizing the utilization of donor organs offered for lung transplantation.

The number of patients awaiting lung transplantation (LT) and waiting time for surgery is increasing. In Australia, LT rates are 4. 6/million population/yr, which despite low organ donation rates, are the highest published in the world. The Australian organ allocation system allows identification of marginal donors and therapeutic manipulation where appropriate. This study aims to assess the impact of utilization of marginal donors and aggressive donor management. A comparison between published donor criteria and local practice is made, allowing assessment of the effect of using marginal donors on outcome. Donor management included antibiotic therapy, strict fluid management, physiotherapy, bronchoscopy and bronchial toilet, and alteration of ventilatory settings including initiation of pressure support. Blood gases were repeated to assess the results of interventions. Between January 1, 1995 and May 31, 1998, we performed 140 transplants from 112 of 219 (51%) lung donor offers. Of these donors, 48 (43%) satisfied all published criteria for suitable donor organs (Group 1 = ideal donors) and 64 (57%) did not (Group 2 = marginal donors). Criteria breached by the marginal donors were: an initial ratio of arterial oxygen pressure to fraction of inspired oxygen (PaO2/FIO2) < 300 mm Hg (n = 20), abnormal radiology (n = 39), pulmonary infection (n = 24), 20 pack-years smoking (n = 5) and age > 55 yr (n = 4). Therapeutic manipulation resulted in improvement in the PaO2/FIO2 ratio in 20 donors (Group 3) who would not otherwise have been used. Immediate and 24 h postoperative gas exchange and length of intensive care unit (ICU) stay was not different for recipients from donors from all three groups. Overall survival was 94% at 30 d, 83% at 1 yr, 70% at 2 yr, and 62% at 3 yr and was not significantly different from the three groups. We conclude that organ utilization can be maximized by therapeutic manipulation and utilization of marginal donors without compromising results from transplantation.

EFFECT OF INTRAOPERATIVE INSPIRED GAS MIXTURES ON POSTOPERATIVE NOCTURNAL OXYGEN SATURATION

Continuous postoperative nocturnal pulse oximetry was performed in 20 patients undergoing elective cholecystectomy to examine if the composition of anaesthetic gas mixtures affects postoperative gas exchange. The patients were allocated randomly to receive either nitrogen or nitrous oxide during anaesthesia, and oximetry was performed on the night before operation and the first and third nights after operation. Considerable oxygen desaturation was seen in both groups. During the first night after operation the proportion of the night during which oxygen saturation was less than 85% was greater in the nitrogen group than in the nitrous oxide group, but there was no significant difference between the mean overnight saturation values of the two groups.

Pulmonary oxygen transfer deficits of diabetic origin in patients undergoing coronary artery bypass grafting.

The objective of this study was to determine the effects of a diabetic disposition on pulmonary gas exchange by examining 72 patients who underwent coronary artery bypass grafting (CABG), using the arterial/alveolar oxygen tension ratio [(a/A)PO2] as a criterion. Patients were divided into a diabetic (DM) group and a nondiabetic (non-DM) group. The postoperative blood gases and hemodynamic data measured when the blood glucose level was at a maximum on the day of CABG were used as the postoperative pulmonary gas exchange indices, and the physicians who managed these patients were unaware of this study. The preoperative (a/A)PO2 ratio was 0.66 +/- 0.03 (SE) in the DM group and 0.78 +/- 0.02 in the non-DM group (P < 0.01), while the postoperative ratios were 0.42 +/- 0.03 and 0.52 +/- 0.03, respectively (P = 0.01). The correlation coefficient (r) for regression analysis of the relation between the postoperative PaO2/FIO2 ratio and the postoperative (a/A)PO2 ratio was 0.99 in the DM group (P < 0.01) and 0.88 in the non-DM group (P < 0.01). The r values of the relation between (a/A)PO2 and (A-a)PO2 were -0.68 (P < 0.00) and -0.84 (P < 0.01), while those for the respiratory index were -0.87 (P < 0.01), and -0.93 (P < 0.01), respectively. Thus, pulmonary oxygen transfer was compromised before and after CABG in the DM group compared to the non-DM group. Moreover, the PaO2/FIO2, being the simplest pulmonary gas exchange index to calculate, was a reliable substitute for the (a/A)PO2 ratio during the early postoperative management of CABG patients.