Comparable postoperative pulmonary atelectasis in patients given 30% or 80% oxygen during and 2 hours after colon resection.

BACKGROUND: High concentrations of inspired oxygen are associated with pulmonary atelectasis but also provide recognized advantages. Consequently, the appropriate inspired oxygen concentration for general surgical use remains controversial. The authors tested the hypothesis that atelectasis and pulmonary dysfunction on the first postoperative day are comparable in patients given 30% or 80% perioperative oxygen. METHODS: Thirty patients aged 18-65 yr were anesthetized with isoflurane and randomly assigned to 30% or 80% oxygen during and for 2 h after colon resection. Chest radiographs and pulmonary function tests (forced vital capacity and forced expiratory volume) were obtained preoperatively and on the first postoperative day. Arterial blood gas measurements were obtained intraoperatively, after 2 h of recovery, and on the first postoperative day. Computed tomography scans of the chest were also obtained on the first postoperative day. RESULTS: Postoperative pulmonary mechanical function was significantly reduced compared with preoperative values, but there was no difference between the groups at either time. Arterial gas partial pressures and the alveolar-arterial oxygen difference were also comparable in the two groups. All preoperative chest radiographs were normal. Postoperative radiographs showed atelectasis in 36% of the patients in the 30%-oxygen group and in 44% of those in the 80%-oxygen group. Relatively small amounts of pulmonary atelectasis (expressed as a percentage of total lung volume) were observed on the computed tomography scans, and the percentages (mean +/- SD) did not differ significantly in the patients given 30% oxygen (2.5% +/- 3.2%) or 80% oxygen (3.0% +/- 1.8%). These data provided a 99% chance of detecting a 2% difference in atelectasis volume at an alpha level of 0.05. CONCLUSIONS: Lung volumes, the incidence and severity of atelectasis, and alveolar gas exchange were comparable in patients given 30% and 80% perioperative oxygen. The authors conclude that administration of 80% oxygen in the perioperative period does not worsen lung function. Therefore, patients who may benefit from generous oxygen partial pressures should not be denied supplemental perioperative oxygen for fear of causing atelectasis.

Use of abciximab-modified thrombelastography in patients undergoing cardiac surgery.

UNLABELLED: Thrombelastography (TEG) is a reliable coagulation monitoring system that can guide blood product transfusion in cardiac surgery. The maximum amplitude (MA) of TEG measures clot strength, which is dependent on both fibrinogen level and platelet function. Inhibition of platelet function with abciximab-fab is suggested to permit quantitative assessment of the contribution of fibrinogen to clot strength. We hypothesized that abciximab-modified TEG permits prediction of plasma fibrinogen levels and that the difference of standard MA and abciximab-modified MA (deltaMA) is a correlate for platelet function. We correlated abciximab-modified MA with plasma fibrinogen levels and deltaMA with platelet count in patients undergoing coronary revascularization. Correlation between plasma fibrinogen levels and abciximab-modified MA was significant (adjusted r2: 0.8; P < 0.0001). Correlation of deltaMA with platelet count was not significant when calculated in millimeters (adjusted r2: 0.04; P = 0.73). However, when deltaMA was calculated in dynes per square centimeter (deltaGMA), it correlated significantly with platelet count (adjusted r2: 0.51; P < 0.0001). We conclude that abciximab-modified TEG may therefore help to discriminate between hypofibrinogenemia and platelet dysfunction as a cause of decreased MA. IMPLICATIONS: We examined the use of abciximab-modified thrombelastography in patients undergoing cardiac surgery. Modification of thrombelastography with abciximab-fab allows prediction of fibrinogen levels, despite coagulation altered by cardiac surgery. The difference of standard maximum amplitude and abciximab-modified maximum amplitude correlates with platelet function when expressed in dynes per square centimeter.

Shivering and shivering-like tremor during labor with and without epidural analgesia.

BACKGROUND: Effective treatment and prevention of hyperthermia and shivering-like tremor during labor is hindered by a poor understanding of their causes. The authors sought to identify the incidence of nonthermoregulatory shivering-like tremor and the factors associated with this activity. METHODS: The authors studied women in spontaneous full-term labor who chose epidural analgesia (n = 21) or opioid sedation (n = 31). Shivering-like tremor and sweating were evaluated by observation. Core temperature was recorded in the external auditory canal using a compensated infrared thermometer. Arteriovenous shunt tone was evaluated with forearm minus fingertip skin temperature gradients; gradients less than 0 were considered evidence of vasodilation. Tremor was considered nonthermoregulatory when core temperature exceeded 37 degrees C and the arms were vasodilated. Pain was evaluated using a visual analog scale. RESULTS: Shivering-like tremor was observed in 18% of 290, 30-min data-acquisition epochs before delivery. The patients were both normothermic and vasodilated during 15% of these epochs. Shivering was observed in 16% of 116 postdelivery epochs and was nonthermoregulatory in 28%. Sweating was observed in 30% of predelivery epochs, and the patients were both hypothermic and vasoconstricted during 12%. The mean core temperature in patients given epidural analgesia was approximately 0.2 degrees C greater than in those given sedation. Hyperthermia was observed during 10 epochs (38.4+/-0.3 degrees C) during epidural analgesia and during 10 epochs (38.4+/-0.3 degrees C) with sedation. The patients were vasoconstricted in more than 50% of these epochs in each group. Multivariate mixed-effects modeling identified high pain scores and vasoconstriction as significant predictors of shivering. There were no predictors for shivering epochs in patients who were simultaneously normothermic and vasodilated. Significant predictors of sweating were time before delivery, high pain scores, hypothermia with vasoconstriction, high thermal comfort, and low mean skin temperature. There were no predictors for sweating epochs in patients who were simultaneously hypothermic and vasoconstricted. CONCLUSIONS: This study confirms the clinical impression that some peripartum shivering-like tremor is nonthermoregulatory. The authors also identified nonthermoregulatory sweating. These data indicate that shivering-like tremor and sweating in the peripartum period is multifactorial.