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PubMed1987

Progressive neuropsychologic impairment and hypoxemia. Relationship in chronic obstructive pulmonary disease.

In previous work we showed that patients with chronic obstructive pulmonary disease (COPD) suffered decrements in neuropsychologic functioning suggestive of organic mental disturbance. This study combined data from two multicenter clinical trials to explore the nature and possible determinants of such neuropsychologic change. Three groups of patients with COPD whose hypoxemia was mild (N = 86), moderate (N = 155), or severe (N = 61) were compared with age- and education-matched nonpatients (N = 99). The rate of neuropsychologic deficit rose from 27% in mild hypoxemia to 61% in severe hypoxemia. Various neuropsychologic abilities declined at different rates, suggesting differential vulnerability of neuropsychologic functions to progress of COPD. Multivariate analyses revealed a consistent significant relationship between degree of hypoxemia and neuropsychologic impairment, but the amount of shared variance was small (7%). Increasing age and lower education were also associated with impairment.

Adult↗

PubMed2005

Continuous positive airway pressure for treatment of postoperative hypoxemia: a randomized controlled trial.

CONTEXT: Hypoxemia complicates the recovery of 30% to 50% of patients after abdominal surgery; endotracheal intubation and mechanical ventilation may be required in 8% to 10% of cases, increasing morbidity and mortality and prolonging intensive care unit and hospital stay. OBJECTIVE: To determine the effectiveness of continuous positive airway pressure compared with standard treatment in preventing the need for intubation and mechanical ventilation in patients who develop acute hypoxemia after elective major abdominal surgery. DESIGN AND SETTING: Randomized, controlled, unblinded study with concealed allocation conducted between June 2002 and November 2003 at 15 intensive care units of the Piedmont Intensive Care Units Network in Italy. PATIENTS: Consecutive patients who developed severe hypoxemia after major elective abdominal surgery. The trial was stopped for efficacy after 209 patients had been enrolled. INTERVENTIONS: Patients were randomly assigned to receive oxygen (n = 104) or oxygen plus continuous positive airway pressure (n = 105). MAIN OUTCOME MEASURES: The primary end point was incidence of endotracheal intubation; secondary end points were intensive care unit and hospital lengths of stay, incidence of pneumonia, infection and sepsis, and hospital mortality. RESULTS: Patients who received oxygen plus continuous positive airway pressure had a lower intubation rate (1% vs 10%; P = .005; relative risk [RR], 0.099; 95% confidence interval [CI], 0.01-0.76) and had a lower occurrence rate of pneumonia (2% vs 10%, RR, 0.19; 95% CI, 0.04-0.88; P = .02), infection (3% vs 10%, RR, 0.27; 95% CI, 0.07-0.94; P = .03), and sepsis (2% vs 9%; RR, 0.22; 95% CI, 0.04-0.99; P = .03) than did patients treated with oxygen alone. Patients who received oxygen plus continuous positive airway pressure also spent fewer mean (SD) days in the intensive care unit (1.4 [1.6] vs 2.6 [4.2], P = .09) than patients treated with oxygen alone. The treatments did not affect the mean (SD) days that patients spent in the hospital (15 [13] vs 17 [15], respectively; P = .10). None of those treated with oxygen plus continuous positive airway pressure died in the hospital while 3 deaths occurred among those treated with oxygen alone (P = .12). CONCLUSION: Continuous positive airway pressure may decrease the incidence of endotracheal intubation and other severe complications in patients who develop hypoxemia after elective major abdominal surgery.

Aged↗

PubMed1997

Percutaneous balloon catheter closure of a patent foramen ovale in a patient with pulmonary disease, profound hypoxemia, and normal right heart pressures.

Right-to-left intracardiac shunting across a patent foramen ovale (PFO) has been reported in patients with pulmonary embolism, right ventricular (RV) infarction, positive pressure ventilation with positive end-expiratory pressure, heart failure with left ventricular assist devices, cardiac tamponade, and unilateral diaphragmatic paralysis. The primary driving force for these shunts is a reduction in the compliance of the pulmonary bed or right ventricle; right atrial pressure is usually elevated and pulmonary hypertension is frequently present. Significant shunting and hypoxemia are unusual in the absence of these diseases. We encountered a patient with normal pulmonary pressures, severe hypoxemia, pulmonary disease, and intracardiac shunting across a PFO in whom it was difficult to determine how great a role intracardiac shunting was playing in his hypoxemia. To assess this, we performed percutaneous balloon catheter occlusion of the PFO, using transthoracic echocardiography with contrast to confirm closure of the PFO. Therapeutic balloon occlusion has been reported in severe hypoxemia due to shunting across a PFO in a patient with RV infarction. Our case is unique, however, in two respects. First, this patient had normal right-sided cardiac pressures and normal RV function and, thus, no obvious driving force for a significant right-to-left shunt. Second, transthoracic echocardiography with contrast was used before and after balloon inflation to confirm closure of the PFO. This technique helped to answer the important clinical question of whether surgical closure of the PFO in this patient with both lung disease and intracardiac shunting would significantly improve his oxygenation.

Adult↗

PubMed2005

Episodes of hypoxemia during synchronized intermittent mandatory ventilation in ventilator-dependent very low birth weight infants.

Distinct patterns of asynchrony, and episodes of hypoxemia, may occur in a spontaneously breathing preterm infant during conventional intermittent mandatory ventilation (IMV) on traditional time-cycled, pressure-limited ventilators. Synchronized IMV (SIMV) and assist/control ventilation are frequent modes of patient-triggered ventilation used with infant ventilators. The objective of this study was to use computerized pulse oximetry to quantify the occurrence of episodes of hypoxemia (oxygen desaturation) during SIMV vs. IMV, in preterm infants < or = 1,250 g who required mechanical ventilation at > or = 14 days of age. We performed a randomized, crossover study with each infant being randomized to IMV or SIMV (Infant Star ventilator) for initial testing for a 1-hr period. Patients were subsequently tested on the alternate modality after a stabilization period of 10 min at the same ventilator and fractional inspired oxygen concentration (FiO2) settings. Pulse oximetry data were obtained with a Nellcor N-200 monitor, a microcomputer, and a software program (SatMaster). An investigator blinded to the randomized assignment evaluated all measurements. Eighteen very low birth weight (VLBW) infants with a birth weight of 777 +/- 39 g (mean +/- SEM) and gestational age 25.1 +/- 0.3 weeks were studied. The average pulse oximeter oxygen saturation (SaO2) was higher on SIMV than IMV (P < 0.01). During SIMV, these infants had significantly fewer episodes of hypoxemia (duration of episodes of oxygen desaturation as a percentage of scorable recording time) to 86-90% SaO2 (P < 0.01), 81-85% SaO2 (P < 0.01), and 76-80% SaO2 (P < 0.05) when compared to IMV. There was also a significant decrease in percentage of time of desaturation to SaO2 < 90% (P = 0.002), < 85% SaO2 (P = 0.003), and < 80% SaO2 (P = 0.02) during SIMV vs. IMV. Our preliminary findings indicate that the use of SIMV in a population of VLBW ventilator-dependent infants (> or = 14 days of age) results in better oxygenation and decreased episodes of hypoxemia as compared to IMV.

Cross-Over Studies↗

PubMed1988

The prevalence of hypoxemia detected by pulse oximetry during recovery from anesthesia.

Pulse oximetry was used to assess the prevalence of hypoxemia (arterial oxygen saturation of 90% or less) at various times in the immediate postoperative period: five minutes after arrival, 30 minutes later, and just before discharge. Among 149 inpatients studied, one or more hypoxemic measurements were made in 21 (14%) during their postoperative course. Of 92 outpatients, 1 (1%) was found to be hypoxemic. For inpatients, the prevalence of hypoxemia preoperatively, 5 minutes after arrival in recovery, 30 minutes later, and at discharge was 2%, 4%, 6%, and 9%, respectively. Patient factors associated with a significantly higher prevalence of hypoxemia were obesity (22%), body cavity surgical procedures (24%), age over 40 years (18%), American Society of Anesthesiologists physical status (I, 7%; II, 17%; III, 18%; IV, 100%), duration of anesthesia longer than 90 minutes (18%), and intraoperative administration of greater than 1,500 ml of fluid (20%). Unrecognized hypoxemia in postsurgical inpatients with or without these risk factors is common. Therefore routine monitoring of these patients with a pulse oximeter is suggested.

Adult↗

PubMed1981

Relationship between postoperative hypoxemia and the operative site.

The effect of the site of operation on postoperative hypoxemia was studied in 104 patients undergoing thoraco-abdominal, thoracic, upper abdominal, lower abdominal, extra-abdominal and non-thoracic operations. The degree of postoperative hypoxemia was the most extensive in patients undergoing thoraco-abdominal, moderate in thoracic and upper abdominal operations, and minimal in lower abdominal and other operations. On the other hand, the duration of hypoxemia also differed with the surgical procedures. Arterial oxygen tension returned to almost control values by the 3rd postoperative day in cases of lower abdominal and extremity operations and by the 7th postoperative day in those undergoing thoracic and upper abdominal surgery. Postoperative hypoxemia, however, remained throughout the fourteen day study period, in patients undergoing thoraco-abdominal operation. True shunt was measured in 27 patients with thoraco-abdominal, thoracic and upper abdominal operations. An increase in true shunt was evident postoperatively in the entire group of patients. The increase was significantly larger and longer lasting in cases of thoraco-abdominal incision than that in cases of thoracic and upper abdominal incision alone. Differences in postoperative true shunt between cases of thoracic and upper abdominal incisions were nil.

Abdomen↗

PubMed2003

Alarming hypoxemia during one-lung ventilation in a patient with respiratory bronchiolitis-associated interstitial lung disease.

PURPOSE: To report a patient with respiratory bronchiolitis-associated interstitial lung disease (RB-ILD) who developed severe hypoxemia during one-lung ventilation (OLV). CLINICAL FEATURES: A 27-yr-old female, ex-smoker presented with productive cough and dyspnea of 18-month duration. The chest x-ray revealed diffuse abnormalities involving both lungs consisting of interstitial emphysema with irregular shadowing. Preoperative PaO(2) was 88 mmHg and pulmonary function tests showed moderate obstructive disease. The patient underwent right open lung biopsy. After induction of anesthesia, a left double lumen tube was inserted and its position verified with auscultation and fibreoptic bronchoscopy. Upon initiation of OLV, the patient developed severe hypoxemia and the PaO(2) dropped from 500 mmHg during two-lung ventilation (TLV) to 50 mmHg. Hypoxemia was readily corrected by resuming TLV. CONCLUSION: The severe hypoxemia during OLV in this patient with RB-ILD may be attributed to impaired hypoxic pulmonary vasoconstriction. Other causes were not excluded. Caution is warranted when initiating OLV in these patients.

Adult↗

PubMed1987

Hypoxemia during ambulatory gynecologic surgery as evaluated by the pulse oximeter.

Pulse oximetry was used to determine the incidence of intraoperative hypoxemia in 108 patients undergoing ambulatory gynecologic operation. Eleven (10%) experienced moderate desaturation (arterial oxygen saturation less than 90%), and 5 (5%) suffered severe hypoxemic episodes (arterial oxygen saturation less than 85%). Among patient risk factors--including operation, body habitus, smoking habits, history of asthma, age, and airway characteristics--an association with moderate hypoxemia was found only with nonlaparoscopic gynecologic operation, obesity, and age over 35 years, and an association with severe hypoxemia was found only with obesity and age over 35. Among operative events--including inspired oxygen concentration, position, mode of ventilation, and anesthesia phase--an association with moderate hypoxemia was found only with the lithotomy position, manual ventilation, and arousal. The cost per patient of monitoring with a pulse oximeter is about +1.35. A cost-benefit analysis reveals that a mortality rate of 1 in 40,000 among patients who actually become moderately hypoxemic would justify the cost of monitoring arterial oxygen saturation. We conclude that pulse oximetry should be part of routine anesthetic monitoring.

Adult↗

PubMed1975

Effects of hypoxemia on the extent of myocardial necrosis after experimental coronary occlusion.

Arterial oxygen tension is variable in patients with acute myocardial infarction, and the effect of hypoxemia on the extent of myocardial necrosis after coronary occlusion has not been defined. In 11 anesthetized open chest dogs the left anterior descending coronary artery or one of its major branches was occluded for 20 minutes, and 10 to 15 epicardial electrocardiographic leads were recorded in the distribution and vicinity of the site of occlusion. Average S-T segment elevation and the number of sites showing S-T segment elevation greater than 2 mv, 15 minutes after occlusion were used as indexes of the severity and extent of ischemic injury. After occlusion with an inspired oxygen concentration of 20 percent these indexes were, respectively, 2.0 plus or minus 0.5 mv (mean plus or minus standard error) and 3.6 plus or minus 0.8 sites; the respective values increased to 3.3 plus or minus 0.5 mv (P smaller than 0.01) and 6.7 plus or minus 0.7 sites (P smaller than 0.01) after occlusion with an inspired oxygen concentration of 10 percent, and arterial partial pressure of oxygen decreased from 92 plus or minus 5 to 45 plus or minus 3 mm Hg. In 23 dogs the occlusion was maintained for 24 hours and the S-T segment elevation 15 minutes after occlusion was compared with myocardial creatine phosphokinase (CPK) activity and histologic appearance 24 hours later. In control dogs (inspired oxygen concentration of 20 percent) sites with no S-T segment elevation 15 minutes after occlusion showed normal myocardial CPK activity 24 hours later, whereas in sites with S-T segment elevation exceeding 2 mv there was an inverse relation between S-T segment elevation in each site and its myocardial CPK activity 24 hours later. Histologic examination revealed early myocardial necrosis in 98 percent (82 of 84) of sites with S-T segment elevation greater than 2 mv. In experimental dogs (inhaling a 10 percent oxygen concentration for the first 8 of the 24 hours of occlusion) many sites that showed no S-T segment elevation before hypoxemia was induced exhibited S-T segment elevation before hypoxemia was induced exhibited S-T segment elevations 30 minutes later and showed abnormally low CPK activity and histologic evidence of early necrosis. We conclude that after experimental coronary occlusion, hypoxemia is deleterious because it substantially increases myocardial damage.

Animals↗

PubMed1981

Effect of acute hypoxemia and respiratory acidosis on the fetal heart rate in monkeys.

The fetal heart rate (FHR) response to acute nonacidemic hypoxemia and to acute respiratory acidosis was studied in unanesthetized pregnant monkeys by means of chronically implanted catheters and electrodes. Average FHR and short- and long-term FHR variability were analyzed separately. The FHR response to either hypoxemia or hypercapnia consisted of slowing and increased variability. The slowing was more consistent with hypercapnia than with hypoxemia. Long-term FHR variability increased with both test stresses. The increase in short-term FHR variability was much greater in response to hypoxemia than to hypercapnia. Both the FHR slowing and the increases in variability in response to the test stresses were reduced by prior administration of atropine to the fetus.

Acidosis, Respiratory↗

PubMed1982

The effect of beta-adrenergic stimulation on fetal cardiovascular function during hypoxemia.

The effect of beta-adrenergic stimulation on fetal cardiovascular function during hypoxemia was studied in six lamb fetuses with gestational ages of 119 to 140 days. In chronic preparations, we determined fetal heart rate, umbilical blood flow (by electromagnetic flowmeter), PO2, PCO2, and pH and calculated fetal cardiac output and organ blood flows (using 15 mu nuclide-labeled microspheres). Observations were made during control periods and periods of hypoxemia, beta-adrenergic blockade by propranolol, and hypoxemia superimposed upon the beta-adrenergic blockade. Beta blockade effected a decrease in fetal heart rate both at rest and with hypoxemic stress. Propranolol produced a fall in cardiac output with hypoxemia, but the meaning of this in regard to beta-adrenergic effects is unclear. Beta blockade did not alter fetal arterial pressure or general blood flow distribution. However, we observed a decrease in umbilical blood flow in response to propranolol under both normoxic and hypoxemic conditions.

Animals↗

PubMed1990

Effects of hypoxemia with and without acidemia on the isometric contraction time and the electromechanical delay of the fetal myocardium: an experimental study on the ovine fetus.

This study assessed the response of the preejection period during hypoxemia with and without acidemia. In five pregnant ewes, hypoxemia was created during 1 hour followed by fetal infusion of lactic acid during 2 hours. A micromanometer catheter positioned above the fetal aortic valve, an endocavitary phonocardiogram, and a fetal electrocardiogram allowed measurements of the two components of the preejection period--the isometric contraction time and the electromechanical delay. At the onset of hypoxemia, because of changes in isometric contraction time, the preejection period began to shorten. When acidemia was induced, the preejection period modified slowly in the opposite direction and lengthened, initially because of a prolongation of electromechanical delay and later because of an increase in the already shortened isometric contraction time. This process developed slowly and at the end of 2 hours of acidemia, preejection period were back to preexperimental values. It can be concluded that systolic time intervals can be normal and misleading when acidosis complicates hypoxemia.

Acids↗

PubMed1990

Effect of hypoxemia on pharmacokinetics of endotracheal lidocaine in dogs.

Endotracheal administration is an effective alternative method for giving drugs in the many clinical situations in which it is difficult or impossible to quickly obtain an intravenous line. Yet whether various clinical conditions such as hypoxemia have any effect on endotracheal drug therapy is not known. Sixteen sets of plasma lidocaine levels were measured at 5, 15, 30, and 60 min after endotracheal lidocaine administration in eight dogs. Each dog was given the same dose of endotracheal lidocaine by the same technique of administration while in both a normal control state (Group I = 'Non-hypoxemia', mean Po2 = 98) and during hypoxemia (Group II = "Hypoxemia", mean Po2 = 36). Significantly higher plasma lidocaine levels occurred in the hypoxemic state (Group II) at time = 5 min while there was no significant difference in plasma lidocaine levels at time = 15, 30, and 60 min. Mean plasma lidocaine levels (micrograms/ml) at 5 min were: Group I = 1.38, Group II = 2.36 (significant at P less than 0.05). Plasma lidocaine levels were: Group I = 1.61 vs. Group II = 1.63 at time = 15 min, Group I = 1.11 vs. Group II = 1.10 at time = 30 min, and Group I = 0.54 vs. Group II = 0.51 at time = 60 min. Thus, there was a higher peak plasma lidocaine level and a shorter time to peak plasma lidocaine levels in the hypoxemic dogs.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

Hypoxemia does not affect the strength of the inspiration-inhibiting Breuer-Hering reflex.

Several studies were focused on the consequences of reduced PaO2 (hypoxemia) on the Breuer-Hering inspiration-inhibiting vagal reflex. However, these data are often contradictory and do not allow us to decide whether hypoxemia interacts with the central integration of pulmonary vagal afferents and/or exerts peripheral influence on pulmonary stretch receptor (PSR) activity. The present study was performed in anesthetized rabbits breathing different gas mixtures containing O2, N2 and CO2. Intravenous injection of bicarbonates and CO2 addition in the inspired mixture maintained pHa and PaCO2 within their physiological ranges. The Breuer-Hering reflex, assessed from the changes in diaphragmatic EMG activity, was elicited either by inflating the lungs at different volumes above the functional residual capacity (PSR activation) or by direct electrical stimulation of vagal afferents (central stimulation). Hypoxemia never significantly modified the strength of the reflex or its threshold. Thus, acute hypoxemia present at high altitude does not seem to modify the key role played by PSR afferents in the ventilatory control.

Animals↗

PubMedDate not supplied

Effects of acute hypoxemia on umbilical arterial Doppler indices in a fetal ovine model.

Changes in umbilical arterial Doppler waveform in response to acute maternal hypoxemia were assessed in a chronic ovine model. Maternal heart rate, blood gases, fetal heart rate and umbilical arterial Doppler indices measured at baseline conditions and during periods of maternal hypoxemia were compared. The indices measured were systolic-diastolic ratio (S/D), pulsatility index (PI) and resistance index (RI). Fetal heart rate decreased (less than 80 beats/min) and umbilical arterial Doppler indices increased (P less than 0.001) during the periods of hypoxemia. Furthermore, the Doppler indices were highly but negatively correlated with alterations in the fetal heart rate (FHR) (P less than 0.001). Analysis of the Doppler waveform phase intervals revealed nearly constant systolic intervals while diastolic intervals varied inversely with the heart rate alterations. Moreover, the umbilical arterial Doppler indices, when corrected for FHR changes, were relatively unchanged from baseline measurements. This study indicates that maternal hypoxemia induced changes in the umbilical arterial Doppler indices may be primarily attributable to the changes in FHR.

Analysis of Variance↗

PubMedDate not supplied

Continuous monitoring of oxygen saturation in prehospital patients with severe illness: the problem of unrecognized hypoxemia.

The continuous measurement of arterial oxygen saturation using pulse oximetry (SpO2) has become popular for critically ill hospitalized patients. Its use in the ambulance transfer of similarly ill patients has been infrequently documented. This study examines the use of prehospital pulse oximetry, with special reference to the ability of ambulance attendants to recognize hypoxemia. Using a prospective single-blind case series method, a convenience sample of adult patients transferred by ambulance designated Code 3 (serious but not life threatening) or Code 4 (serious and life threatening) to a regional base hospital were examined for the presence of hypoxemia. An Ohmeda finger pulse oximeter probe was attached to all patients. Prior to the study, oxygen treatment was reviewed and ambulance personnel were instructed on the use of the instrument. The continuous oxygen saturation record was not revealed to the attendant(s) during the cell. Administration of oxygen was monitored, and a study form was completed by the attendant at the completion of the call. Overall, 50 patients were included in the study. The most common complaints were chest pain 21 (37%) and shortness of breath 15 (27%). The average age was 64 years, with a range of 32-82. Hypoxemia, defined as SpO2 of less than 90% for more than 1 minute, was detected in 14 patients. Attendants recognized hypoxemia on clinical grounds in only 4 patients (sensitivity = 28%). Forty-one (82%) patients received various amounts of supplemental oxygen; many patients remained hypoxemic despite therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMedDate not supplied

Effect of general anesthesia and major versus minor surgery on late postoperative episodic and constant hypoxemia.

STUDY OBJECTIVE: To evaluate the relative contribution of general anesthesia alone and in combination with the surgical procedure to the pathogenesis of late postoperative hypoxemia. DESIGN: Open, controlled study. SETTING: University hospital. PATIENTS: 60 patients undergoing major abdominal surgery and 16 patients undergoing middle ear surgery, both with comparable general anesthesia. MEASUREMENTS AND MAIN RESULTS: Patients were monitored with continuous pulse oximetry on one preoperative night and the second postoperative night. Significant episodic or constant hypoxemia did not occur on the second postoperative night following middle ear surgery and general anesthesia, but severe episodic and constant hypoxemia did occur on the second postoperative after major abdominal surgery and general anesthesia. CONCLUSIONS: General anesthesia in itself is not an important factor in the development of late postoperative constant and episodic hypoxemia, which instead may be related to the magnitude of trauma and/or opioid administration.

Abdomen↗

PubMedDate not supplied

Effect of pulsatile oxytocin administration to the pregnant ewe in the last third of gestation on fetal ACTH and cortisol response to acute hypoxemia.

OBJECTIVE: The aim of this study was to examine the effect of increased myometrial contractility throughout the last third of pregnancy on the ovine fetal response to short-term hypoxemia. METHODS: Oxytocin (600 microU/kg/minute, n = 5) or saline (n = 7) was infused for 5 minutes every 20 minutes into the maternal jugular vein starting at 95-99 days of gestation and continuing throughout the last third of gestation. Fetuses were subjected to a hypoxemic challenge (1 hour) at 131 days of gestation while fetal plasma ACTH and cortisol levels and nuchal muscle electromyogram activity were monitored. RESULTS: The fetal plasma ACTH concentration before and during the hypoxemic challenge was similar in the control and oxytocin groups. The fetal plasma cortisol concentration in the oxytocin group was significantly lower before and during the hypoxemia than in the controls. During hypoxemia, fetal nuchal muscle activity was significantly reduced only in the control group. CONCLUSION: Increased myometrial contracture frequency throughout the last third of pregnancy alters both the neuroendocrine and behavioral responses of fetal sheep to short-term hypoxemia.

Adrenocorticotropic Hormone↗