Visceral lipid peroxidation occurs at reperfusion after supraceliac aortic cross-clamping.

PURPOSE: Recently, we have reported that lipid peroxidation specific to oxygen free radical-mediated injury increased immediately after reperfusion of human liver allografts. However, in the human liver transplantation setting it was impossible to disassociate the contributions to lipid peroxidation caused by the warm and cold ischemic phases from those caused by reperfusion. Therefore we now have studied lipid peroxidation at reperfusion after supraceliac aortic cross-clamping in patients with normal livers. METHODS: Ethane, a noninvasive biomaker of lipid peroxidation, was measured in exhaled breath of patients before and during cross-clamping of the thoracic aorta and at sequential time intervals after visceral reperfusion. RESULTS: Approximately a two-fold transient increase in the ethane level was observed at around 15 minutes after reperfusion in those patients whose aortas were cross-clamped for more than 18 minutes. CONCLUSIONS: These results indicate that free radical-mediated lipid peroxidation occurs at reperfusion of warm ischemic viscera in the clinical setting of aortic repair. This observation supports the hypothesis that substantial lipid peroxidation occurs when tissues are subjected to cold or warm ischemia followed by reperfusion.

Absorption characteristics of human fetal hemoglobin at wavelengths used in pulse oximetry.

The absorption characteristics of fetal and adult human hemoglobin samples were determined for the range of 600 to 1,050 nm. Over this range, fetal hemoglobin absorption is nearly identical to that of adult hemoglobin. Since currently available two-wavelength pulse oximeters base their calculations of arterial oxyhemoglobin saturation on absorption at the wavelengths of 660 and 920 nm, we conclude that the accuracy of two-wavelength pulse oximetry previously demonstrated in adults can be extrapolated to infants with high concentrations of fetal hemoglobin.

Accuracy of pulse oximetry during arterial oxyhemoglobin desaturation in dogs.

An animal model was developed to evaluate the accuracy of pulse oximetry over a wide range of oxyhemoglobin desaturation. The fractional inspired oxygen concentration was varied from 0.03-1.0 in five anesthetized dogs. One hundred and twelve simultaneous pulse oximeter oxygen saturation measurements (SpO2) and IL 282 CO-Oximeter arterial oxygen saturation (SaO2) measurements were made. Variance of SpO2 was increased for SaO2 less than 22%. Linear regression analysis of the data for SaO2 greater than 22% produced the equation y = 0.93x + 9.8 (r2 = 0.97). The mean difference between SpO2 and SaO2 was +5.5% +/- 4.2% (SD) over the range of 22-100%. Spectral analyses of oxygenated (O2Hb) and reduced (RHb) canine and human hemoglobins were performed. The absorption spectra of canine O2Hb and RHb were nearly identical to those of human O2Hb and RHb. Therefore, 1) SpO2 measurements in dogs at SaO2 greater than 22% are relatively accurate, and 2) hemoglobin absorption characteristics support the contention that such canine pulse oximeter studies can be extrapolated to humans.

Monitoring the resuscitation of preterm infants in the delivery room using pulse oximetry.

The first few minutes after birth are a critical time of adaptation of the newborn infant to extrauterine life. The adequacy of that adaptation has been evaluated by means of the summed Apgar score. In preterm infants, Apgar score may correlate less with adequacy of cardiopulmonary function because of developmental immaturity. Measurement of arterial oxygen saturation by means of pulse oximetry offers a physiologic, real time method of monitoring the progress of cardiopulmonary adaptation by which the clinician can evaluate the need for and success of resuscitative efforts. Four preterm infants are reported in whom pulse oximetry was useful in assessing the changes in oxygen saturation during resuscitation.

Pneumocephalus: effects of patient position on the incidence and location of aerocele after posterior fossa and upper cervical cord surgery.

The incidence of pneumocephalus and factors contributing to its occurrence were studied retrospectively in 100 consecutive patients who underwent posterior fossa or cervical cord surgery in the sitting, park-bench, and prone positions. Supine skull x-ray films taken immediately postoperatively were used to determine the presence of intracranial air. Surgery in the sitting position uniformly resulted in pneumocephalus (32/32 patients). Pneumocephalus also occurred frequently among patients in the park-bench (29/40) and prone positions (16/28). Intraventricular air occurred more frequently when patients were in the sitting position (25/32) than in the two other surgical positions (3/29 and 4/16, respectively, P less than 0.001). The high incidence of pneumocephalus and of intraventricular air that occurred when patients were in the sitting position is attributed to the large amount of cerebrospinal fluid drained due to gravitational effect. When surgical position is considered one of the contributing factors, only positions significantly affected the frequencies of pneumocephalus and intraventricular air accumulation. None of the 77 patients with pneumocephalus suffered neurologic change related to the presence of intracranial air. We conclude the following: pneumocephalus commonly occurs after posterior fossa or cervical cord surgeries, particularly when the surgery is performed in the sitting position; neurologic change caused by pneumocephalus is a rare complication after posterior fossa craniotomy; when a patient with coexisting hydrocephalus undergoes surgery, if the patient is in the sitting position, there is an increased risk of trapping a large amount of intracranial air.

Tension pneumocephalus after posterior fossa craniotomy: report of four additional cases and review of postoperative pneumocephalus.

Four cases of tension pneumocephalus after either posterior fossa craniotomy or translabyrinthine resection of acoustic neuroma with or without nitrous oxide anesthesia are described. Three of the operations were performed with the patient in the sitting position, and one was done with the patient in the lateral position. Of the three cases operated in the sitting position, no nitrous oxide was used at any time during anesthesia in one. Two patients failed to regain consciousness after the termination of anesthesia, and the other two developed the sudden onset of neurological symptoms 1 to 1.5 hours after the operation. In all cases computed tomography disclosed a large subdural collection of air. Re-exploration of the surgical wound or twist drill aspiration of the subdural air resulted in prompt recovery of neurological status in three patients, whereas the other patient's neurological status improved gradually without any specific treatment. The role played by nitrous oxide, the mechanisms by which air enters the intracranial space, the contributory factors, and the predisposing surgical conditions of tension pneumocephalus are reviewed and discussed. Dependent drainage of the cerebrospinal fluid, especially in a patient with coexisting hydrocephalus, seems to be the most important factor for the development of this complication.

Rationale and indications for microfiltration of blood in emergency medicine.

Documentation in the literature shows that massive transfusions for severe, nonthoracic trauma contribute to development of progressive pulmonary failure in some patients. Further review shows embolic phenomena in cardiopulmonary bypass procedures contribute to a number of postoperative complitions. These complications are related to the numbers and physical characteristics of aggregates in banked whole blood and to the morphology of the pulmonary circulation. Many of these complications can be prevented or markedly attenuated by microfiltration of banked blood. It is concluded that all transfusions of banked whole blood and blood products should be administered through microfiltration units.

Pulmonary shunting during anaesthesia in man.

Qs/Qt was determined during halothane and oxygen anaesthesia in 22 patients. All were believed to have no pulmonary dysfunction. A surgical operation was in progress and respiration was controlled. Qs/Qt was minimal in 15 of these patients (means 3.9 plus or minus 0.3%), indicating that anaesthesia and operation can be conducted in man without a significant increase of pulmonary shunting. The level of shunting was increased in the other seven patients. In neither group was Qs/Qt altered by the passage of time. Age varied between 23 and 61 years and was directly and significantly correlated to Qs/Qt (r=0.57,P less than0.01).