Comparison of outcomes following complex posterior fossa surgery performed in the sitting versus lateral position

The sitting position during surgery is thought to provide important advantages, yet it remains controversial. We compared surgical and neurological outcomes for patients operated on in the sitting versus lateral position. Technically difficult procedures performed from the years 2001-2008 for complex lesions in the posterior fossa (vestibular schwannomas, other cerebellopontine angle tumors, foramen magnum meningiomas, brainstem cavernomas, pineal region tumors) were included. Outcomes in the two surgical positions were compared for all 243 patients (93 sitting, 38.3%; 150 lateral, 61.7%) and for 130/243 patients with vestibular schwannomas (50 sitting, 38.5%; 80 lateral, 61.5%). Sitting and lateral patient subgroups were clinically comparable. There were no surgical mortalities. The extent of removal and surgical and neurological outcomes were comparable. We found no advantage in surgical or neurological outcomes for use of the sitting or lateral surgical positions in technically difficult posterior fossa procedures. In vestibular schwannoma surgeries facial nerve preservation (House-Brackmann score 1-2) was related to extent of resection but not to surgical position. The choice of operative position should be based on lesion characteristics and the patient's preoperative medical status as well as the experience and preferences of the surgeons performing the procedure.

Visual failure and recovery after thrombosis of a giant carotid ophthalmic aneurysm following vascular bypass and carotid artery ligation

Thrombosis via Hunterian ligation, with or without high-flow bypass, is the definitive treatment for unclippable giant aneurysms; however, secondary deterioration may occur. We present a 67-year-old woman with an unclippable giant (33mm) carotid ophthalmic aneurysm. High-flow external carotid artery to middle cerebral artery bypass and proximal cervical internal carotid artery Hunterian ligation achieved complete thrombosis. Subsequent expansion of the thrombosed aneurysm created mass effect with hydrocephalus, leading to marked cognitive and visual decline. Aneurysmal decompression led to improved vision and near-normal neurological function.

Modeling of frequency doubling and tripling with measured crystal spatial refractive-index nonuniformities

Efficient frequency doubling and tripling are critical to the successful operation of inertial confinement fusion laser systems such as the National Ignition Facility currently being constructed at the Lawrence Livermore National Laboratory and the Omega laser at the Laboratory for Laser Energetics. High-frequency conversion efficiency is strongly dependent on attainment of the phase-matching condition. In an ideal converter crystal, one can obtain the phase-matching condition throughout by angle tuning or temperature tuning of the crystal as a whole. In real crystals, imperfections in the crystal structure prohibit the attainment of phase matching at all locations in the crystal. We have modeled frequency doubling and tripling with a quantitative measure of this departure from phase matching in real crystals. This measure is obtained from interferometry of KDP and KD*P crystals at two orthogonal light polarizations.

[First experiences with retroperitoneoscopic lumbar sympathectomy]

We present our initial experience with retroperitoneoscopic lumbar sympathectomy in a series of 5 men aged 25-45 years. 3 suffered from ischemia of the lower limbs due to Buerger's disease, 1 had severe reflex sympathetic dystrophy and 1 had vasculitis with severe, non-healing lower leg ulcers. The right retroperitoneal space was developed with a dissecting balloon-trocar introduced via a small lateral muscle-splitting flank incision. 2 additional 5 mm trocars were used for instrumentation and clipping. L2-L3 or L3-L4 ganglia were resected; mean operating time was 120 minutes. Only oral analgesics were needed for postoperative pain control and oral food intake was resumed the following morning. The procedure was successful in all and was without complications. Mean hospital stay was 2 days. All patients reported significant relief of ischemia or dystrophic pain and/or improvement in trophic changes in the extremities. In the patient with leg ulcers, the largest was successfully covered with a skin graft. The retroperitoneoscopic approach to lumbar sympathectomy successfully combines the advantages of minimal invasive surgery and the reliability and effectiveness of well-established open sympathectomy.

[Video-assisted thoracoscopic surgery for diagnosis of pulmonary lesions]

23 patients (age 11-66 years) underwent video-assisted thoracoscopic biopsy for diffuse disease or peripheral nodular lesions of the lung. 12 had been previously treated for extrapulmonary malignancy and lung biopsy was done for suspicious metastases. In all cases except 1, lesions were identified and biopsied by thoracoscopy. The postoperative course was easier and shorter as compared to thoracotomy and the mean hospital stay was only 2.5 days. Thoracoscopic lung biopsy is a safe, effective and accurate diagnostic modality for diffuse lung disease and peripheral lesions. It is associated with minimal postoperative pain and discomfort, short hospital stay, early return to normal activity, and gives good cosmetic results.

[Preliminary experience with laparoscopic repair of inguinal hernias]

During 1992-1996 we performed 163 laparoscopic hernia repairs in 100 men and 2 women. The mean age was 50.6; and in 61 the operation was bilateral, 66 were by transabdominal preperitoneal approach and 36 by total extra-peritoneal approach. There were only a few minor complications and total recurrence rate was only 4.3%, partly attributable to our learning curve. Laparoscopic inguinal herniorrhaphy reduces postoperative incisional and muscular pain and causes less disruption in the postoperative period than open repair. Return to normal activity and work is faster for laparoscopic than for open repair, but operating room costs are higher (time and equipment). However, economic advantages for the national economy should be considered.

Multicrystal designs for efficient third-harmonic generation

Efficient frequency tripling of high-fluence, narrow-band laser pulses is routinely accomplished with a doubling crystal and a sum-frequency mixer. The addition of a second mixer can dramatically improve conversion efficiencies for the large bandwidths of interest for inertial confinement fusion. Designs that involve two doublers similarly offer a higher dynamic range of conversion efficiency versus intensity than the usual two-crystal design.

Perturbation theory for electric-field amplitude and phase ripple transfer in frequency doubling and tripling

A theory is presented for the transfer of a perturbation of the electric field from the input to the output of a frequency converter. The transfer relationship for the field ripple is shown to depend on the plane-wave operating parameters of the converter. Predictions of the theory are shown to be in excellent agreement with full numerical simulations of doubling and tripling and experiments measuring ripple transfer in frequency doubling.

Postischemic intestinal motility in rat is inversely correlated to length of ischemia. An in vivo animal model

An inverse correlation between postischemic gastrointestinal motility and the length of intestinal ischemia was found in an animal model. Intestinal ischemia was caused without concurrent laparotomy and for a predetermined time period (ischemia time) by pulling on an external nylon thread that was threaded through a double-lumen catheter. This catheter was passed into the abdominal cavity to encircle the superior mesenteric artery. Gastrointestinal motility was determined by the introduction of a color-marked meal into the animal's stomach and the measurement of the proportionate length of the small bowel filled with it (transit index). This simple and reliable animal model can also be used for the evaluation of techniques and pharmacological manipulations aimed at modulation of the effects of intestinal ischemia on intestinal motility and its consequences.

[Laparoscopic colonic resection]

We present our initial experience with laparoscopic colonic resection in 15 patients: adenocarcinoma of the colon, 10 cases, giant villous adenoma (2), arteriovenous malformation (2), and a case of benign stricture. Mean operating time was 190 minutes and there were no intraoperative complications. The margins of resection and number of resected lymph nodes in patients with malignancy were comparable to those in the conventionally operated. Mean postoperative hospital stay was 6.1 days. During a maximum follow-up of 15 months there were no wound or trocar-site recurrences. We conclude that laparoscopic colonic resection is technically feasible and safe. However, its use for treating malignant diseases of the colon needs further study.

Epidural anesthesia accelerates the recovery of postischemic bowel motility in the rat

BACKGROUND

Intestinal ischemia is associated with derangement of gastrointestinal motility. Uncontrolled clinical observations that bupivacaine injected into the epidural space causes faster recovery of bowel motility after various abdominal operations led us to assess the hypothesis that epidural anesthesia can hasten the recovery of gastrointestinal motility in the immediate postischemic period.

METHODS

Gut motility studies were performed in rats in which epidural anesthesia and intestinal ischemia could be initiated without the need to provoke surgical trauma. Epidural lidocaine was compared to epidural saline in their effect on intestinal motility after a 30-min period of bowel ischemia.

RESULTS

Total ischemia to the small bowel resulted in pronounced postischemic adynamic ileus as evidenced by only 0.7% of the total length of the small bowel filled with a marker meal at the end of the study period (transit index) compared with 84.4% in the control group. Lidocaine epidural anesthesia caused significantly more rapid resolution of the adynamic ileus (60.3% of the bowel filled with the marker meal vs. 30.9% in the controls in which saline was injected).

CONCLUSIONS

Epidural lidocaine compared to epidural saline hastens the recovery of gastrointestinal motility in rats after a 30-min period of bowel ischemia. This effect may be elicited by attenuation of sympathetic efferent inhibitory pathways or by vasodilatation caused by the sympathetic block. These results suggest that lidocaine epidural block not only alleviates pain in situations of ischemic injury to the bowel but may also hasten the recovery from postischemic paralytic ileus.

Plasma concentrations of methadone during postoperative patient-controlled extradural analgesia

Plasma concentrations of methadone were measured by gas chromatography in 16 patients receiving extradural methadone by continuous infusion for relief of postoperative pain. Venous blood samples were taken after a loading dose of extradural methadone 2 mg and during infusion of 0.46 mg h-1 plus patient-controlled increments of 0.2-1 mg. Mean (SD) plasma concentration of methadone was 9.8 (2.1) ng ml-1 at 15 min; this did not change significantly during the first 2 h, after which it increased gradually to 32.2 (4.6) ng ml-1 (P less than 0.001) at the end of 24 h. The mean quantity of extradural methadone required to produce effective analgesia was 10.3 (1.8) mg during the first 12 h after operation and 6 (1.0) mg for the subsequent 12 h. The mean amount of methadone for effective analgesia on the second day was 7.6 (1.1) mg. No adverse effects were detected during the 2-3 days of methadone therapy. Plasma concentration of methadone increased significantly during patient-controlled infusion of extradural methadone in the first 24 h after operation, suggesting rapid vascular uptake. Systemic activity of the drug contributes to the analgesic effect of extradural methadone.

One-lung high-frequency ventilation in the management of traumatic tear of bronchus in a child

An 8-yr-old child suffered traumatic bilateral pneumothoraces and a ruptured right main bronchus. Surgical repair of the bronchus was postponed for 18 h after a definite diagnosis was established due to severe hypoxemia and hypercarbia. Only left endobronchial high-frequency ventilation with muscle relaxation corrected this pulmonary dysfunction sufficiently to enable surgical intervention.

Interaction of hypoxia and hypercapnia on cerebral hemodynamics and brain electrical activity in dogs

The interaction of hypoxic hypoxia, hypercapnia, and mean arterial blood pressure (MABP) was studied in 15 pentobarbital-anesthetized ventilated dogs. In one group of animals (n = 5) hypercapnia [arterial CO2 partial pressure (PaCO2) approximately 50 Torr] was added to both moderate hypoxia and severe hypoxia. Moderate hypoxia [arterial O2 partial pressure (PaO2) = 36 mmHg] increased MABP and cerebral blood flow (CBF) without changes in cerebral O2 uptake (CMRO2). Superimposed hypercapnia increased CBF and MABP further with no change in CMRO2. In another group of animals (n = 5), a MABP increase of approximately 40 mmHg during moderate hypoxia without hypercapnia did not further increase CBF, suggesting intact autoregulation. Thus, during moderate hypoxia, hypercapnia is capable of increasing CBF. Severe hypoxia (PaO2 = 22 mmHg) increased CBF, but MABP and CMRO2 declined. Superimposed hypercapnia further decreased MABP and decreased CBF from its elevated level and further decreased CMRO2. Raising MABP under these circumstances in another animal group (n = 5) increased CBF above the level present during severe hypoxia alone and increased CMRO2. The change in CBF and CMRO2 during severe hypoxia plus hypercapnia with MABP elevation were not different from that severe hypoxia alone. We conclude that, during hypoxia sufficiently severe to impair CMRO2, superimposed hypercapnia has a detrimental influence due to decreased MABP, which causes a decrease in CBF and cerebral O2 delivery.

Epidural capsaicin produces prolonged segmental analgesia in the rat

The effect of epidural capsaicin injections on the thermal nociceptive threshold of unrestrained freely moving adult rats was examined. Capsaicin solution (1% 0.05 ml, 0.1 ml) was injected in a single dose or in two consecutive doses through an indwelling lumbar epidural catheter. Effects were compared with 1 ml 1% capsaicin injected intraperitoneally. Twelve rats served as sham-treated and vehicle controls. Nociceptive thermal stimuli were brief pulses of CO2 laser radiation directed at three body areas, hind limb, forelimb, and pinna. Capsaicin caused prolonged, segmental thermal analgesia. Maximal nociceptive threshold values in the hind limbs, attained within 24 h of epidural injection, were 2.5 (P less than or equal to 0.006) and 5.3 (P less than or equal to 0.0005) time control values for the 0.05-ml and 0.1-ml doses, respectively. Response thresholds in the forelimbs and pinna were unaffected. Two-stage epidural injection of capsaicin led to a roughly twofold elevation of threshold, as well as prolongation of the analgesia to about 14 days. Intraperitoneal injection of capsaicin resulted in elevation of nociceptive threshold which included all body areas tested. These results indicate that epidural application of capsaicin at the lumbar spinal level produced a profound and long-lasting segmental analgesia.

Amplified spontaneous emission in Cassegrainian amplifiers

We consider all possible paths for amplified spontaneous emission (ASE) in multipass laser amplifiers using a Cassegrainian telescope geometry. In particular, we study ASE which is reflected back into the medium off the telescope mirrors themselves. These ASE components are unavoidable in this amplifier geometry. We show that there is a component of the ASE which makes approximately double the number of passes through the amplifier as the laser signal makes. We also show that these high order ASE components are also present in amplifiers which are almost Cassegrainian. They cannot be eliminated by changing the ratio of the scraper and hole radii or the separation of the mirrors. It is likely that these ASE components will be more significant in pulsed lasers than cw lasers.

Research on nonlinear optical materials: an assessment

The seven papers making up this assessment are based on the Workshop on Nonlinear Optical Materials held in April 1986.

Effects of alfentanil on cerebral vascular reactivity in dogs

The effects of high dose alfentanil on the cerebral vascular responses to alterations in mean arterial pressure (MAP), arterial oxygen tension (PaO2) and arterial carbon dioxide tension (PaCO2) were studied in 17 dogs, using the cerebral venous outflow technique. In six animals anaesthetized with sodium pentobarbitone 30 mg kg-1 i.v., bolus injection of alfentanil 0.32 mg kg-1 i.v. decreased MAP without a change in cerebral blood flow (CBF). In another group of animals(n = 5) anaesthetized with pentobarbitone 30 mg kg-1 i.v. the CBF responses to changes in MAP, PaO2, and PaCO2 were studied. In a third group of animals (n = 6) anaesthetized with alfentanil 0.32 mg kg-1 i.v. plus pentobarbitone 1-2 mg kg-1 i.v. and an infusion of alfentanil 0.32 mg kg-1 h-1, the CBF response to alterations in MAP, PaO2, and PaCO2 were studied and compared with the barbiturate-anaesthetized animals. The CBF responses to hypercapnia and hypoxia in the alfentanil-anaesthetized animals were not different from those observed in animals anaesthetized with barbiturate only. The lower and upper limits of cerebral autoregulation in alfentanil-anaesthetized animals were not different from those observed in animals anaesthetized with barbiturate only. The data suggest that alfentanil, in doses sufficient to cause profound analgesia and anaesthesia, does not alter cerebral reactivity to changes in PaO2, PaCO2 and MAP.

Pulmonary complications following endotracheal intubation for anesthesia in breech extraction

A 28-year-old, healthy pregnant patient developed bilateral pneumothorax, subcutaneous emphysema, pneumomediastinum, pneumoretroperitoneum and pneumoperitoneum following endotracheal intubation and manual ventilation during general anesthesia for breech extraction. It is likely that positive-pressure ventilation was the cause for this very rare combination of complications. Early recognition and treatment may prevent such a catastrophe.

Large aperture harmonic conversion experiments at Lawrence Livermore National Laboratory

Large aperture harmonic conversion experiments to 2 omega (532 nm), 3 omega (355 nm), and 4 omega (266 nm) on the Argus laser at the Lawrence Livermore National Laboratory are described. Harmonically converted energies of up to 346 J have been generated at external conversion efficiencies of 83%. A discussion of the harmonic conversion experiments and a brief summary of enhanced 2 omega and 3 omega inertial confinement fusion target performances are provided.

Observations on extradural morphine analgesia in various pain conditions

We report the extradural administration of low-dose morphine in 10 ml of 10% dextrose (2-3 mg) to 98 adult patients with various types of acute and chronic pain. Extradural morphine injections were given either via a Tuohy needle (single or repeat injection) or via an extradural catheter. Pain relief was evaluated by subjective scoring and by the subsequent need for systemic analgesics. In 56% of patients, pain relief was considered good or excellent, in 24% it was fair, and in 20%, poor. The best results were after surgery and trauma and in patients with advanced peripheral vascular disease. The analgesia of each dose of extradural morphine lasted for 8 h (mean range 4-36 h). There was no motor, sensory or sympathetic blockade and no respiratory or haemodynamic complications. Dizziness and vomiting occurred in two patients, and urinary retention for about 12 h in three.

The marked myocardial depressant effect of verapamil

An experiment was designed to measure accurately the primary effect of verapamil on myocardial contractility by infusion of the drug directly into the coronary artery of open-chested anesthetized dogs. A marked myocardial depressant effect, which was dose and time dependent, was noted during verapamil infusion at the infused area only. The percent decrease in contractile force ranged from 8.8 at an infusion rate (mg/min) of 0.55 X 10(-2) to 36.8 at 5.5 X 10(-2). Similar changes were observed in the first derivative of the contractile force. No changes were observed in the left ventricular systolic or end-diastolic pressure and only a mild increase in contractile force was noted in the control (noninfused) area. The depressant effect of verapamil was sustained. Recovery time after 5 min of verapamil infusion was dose dependent, ranging from 10 to 45 min. During the recovery period, an overshoot of the contractile force was observed in dogs on the higher doses only. We concluded that verapamil in clinically relevant doses has a marked negative inotropic effect of long duration and therefore should be used with caution in patients with depressed left ventricular function. Cessation of the verapamil treatment may cause a transient increase in myocardial contractility, which might be hazardous in patients with angina pectoris who have compromised coronary blood flow.

Aberrant position of a central venous catheter: a cause for inadequate fluid replacement in septic shock

An unusual placement of a "central" venous catheter in the porto-hemiazygous system of a cirrhotic patient in septic shock is described. The catheter was misinterpreted as being located in a central vein and served initially as a guide for volume replacement. The high central venous pressure recorded (22 cm H2O) in spite of signs of hypovolemia led to the introduction of a Swan-Ganz catheter which confirmed the presence of hypovolemia. The proper position of the central venous catheter, especially in cirrhotic patients, should not only be confirmed by plain chest x-ray but also by injection of contrast medium.

Preservation of myocardial contractility in hemorrhagic shock with methylprednisolone

The left anterior descending or left circumflex coronary artery was cannulated selectively in 10 dogs. Methylprednisolone, 1 mg per kilogram of body weight, was injected into the artery and the cannula was withdrawn. The animals were then subjected to hemorrhagic shock for 90 minutes. Retransfusion to prestudy blood pressure was then accomplished. The electrocardiogram, arterial blood pressure, contractile force, and first derivative of contractile force were recorded continously both from the areas that were pretreated and those that were not, the controls. Contractile force in the control area was reduced to 32 +/- 3.2% of the preshock period after 90 minutes of shock, whereas in the pretreated area it was twice as high at the same time. Ten minutes after transfusion, the contractile force of the pretreated area exceeded the preshock level, whereas the recovery of contractile force in the control area reached only 70% of the preshock level. This study shows that intracoronary infusion of methylpredisolone can afford myocardial protection in hemorrhagic shock to a significant degree.

The variable effect of PEEP in acute respiratory failure associated with multiple trauma

Both short and longterm effects of positive end-expiratory pressure (PEEP) on oxygenating capacity (OC) were investigated in three groups of patients with acute respiratory failure following multiple trauma (MT). Group A consisted of six patients with "uncomplicated" MT; Group B, eight patients with MT and generalized sepsis; Group C, nine patients with MT and lung contusion. OC was evaluated in terms of PaO2/FIO2 and P(A-a)DO2 on FIO 2 = 1.0. OC was markedly and equally reduced in the three patient groups before use of PEEP. The use of a mean PEEP of 6-7 cm H2O resulted in an initial improvement in mean PaO2/FIO2 of 152.5, 36.1, and 59.2 mm Hg, and an overall improvement of 196.8, 57.5, and 107.0 mm Hg in Groups A, B, and C, respectively. There was a similar improvement in both the initial and the overall effect of PEEP on P(A-a)DO2 in the three groups. The difference in the improvement in OC due to PEEP was statistically significant between Groups A and B. It is concluded that acute respiratory failure following MT includes a wide spectrum of clinical syndromes, and that the improvement in OCT due to PEEP depends on the clinical sydrome that is responsible for the respiratory failure associated with MT.

Cardiopulmonary effects of volume loading in patients in septic shock

The effect of volume loading in 20 patients with clinical and bacteriological evidence of generalized sepsis was studied. The patients were divided into two groups according to their response to volume loading. Group A included 9 patients in whom the initial pulmonary capillary wedge pressure (PWP)was lower than the central venous pressure (CVP). In this group the intravenous administration of 5089+/-409ml/24 hr fluids was accompanied by a significant rise in blood pressure from 94.4+/-9.3mm Hg to 118.9+/-6.3 MM Hg with no significant change in pulse rate or CVP. PWP rose from 5.7 +/- 1.8 to 10.0 +/- 1.4. The rise in cardiac output from 8.0+/-1.3 liter/min to 9.7+/-1.1 liter/min was not statistically significant. Group B included 11 patients in whom the initial PWP was higher than the CVP. In this group, signs of fluid overloading appeared after administration of 3151+/-540ml/24 hr. There was no significant change in blood pressure, pulse rate, CVP, PWP or cardiac output. Urine output was adequate in both groups. This volume load did not affect pulmonary oxygenating capacity (PaO2/F1O2) and effective lung compliance in both groups, but the maintenance of an unchanged oxygenating capacity necessitated an increase in PEEP in some patients. Thus, synchronous monitoring of PWP and CVP in septic shock is helpful in selecting patients (Group A) who will best respond to fluid loading without deterioration of pulmonary oxygenating capacity. PEEP ventilation may be necessary in some patients to maintain the favorable effect of volume loading.

Direct positive inotropic effect of mannitol on the intact canine heart

Infusion of 25% mannitol into either the circumflex or left anterior descending coronary artery caused a significant increase in myocardial force development, measured by means of strain gauge in 10 anesthetized dogs. The changes were confined to the area perfused. The increase in developed force was dose-dependent, 20% at an infusion rate of 0.55 ml/min, 28% at 1.4 ml/min, 32% at 2.8 ml/min and 57% at 5.5 ml/min. There was a similar increase in dF/dt. The increase in developed force in the first minute was also dose-dependent, being 9% at 0.55 ml/min and 40% at 5.5 ml/min. No change in developed force occurred in the control (non-perfused) area or during saline infusion of the same artery at similar rates. A decrease in developed force of 10.5% was observed after the initial rise when mannitol was infused at 5.5 ml/min. This effect did not completely abolish the initial increase. No change in blood pressure, heart rate, LV systolic and diastolic pressure of LV dp/dt occurred during the experiment. It is concluded that doses of mannitol which are in clinical use have a direct positive inotropic effect on the intact canine heart.

The effect of PEEP on oxygenating capacity in acute respiratory failure with sepsis

We report an evaluation of the effect of postive-end-expiratory-pressure (PEEP) on improving pulmonary oxygenating capacity in the adult respiratory distress syndrome (ARDS), when the latter is associated with generalized gram-negative sepsis. Fifty-seven cases treated in our RICU with PEEP ventilation (April 1972 to January 1975) were retrospectively reviewed. Oxygenating capacity improvement was evaluated in terms of the changes in PaO2/FIO2 and AaDO2 (FIO2 = 1.0). Both the short term (2-3 hours from the initiation of PEEP) and the overall effects of PEEP were evaluated. A mean PEEP of 5.6 cm H2O initially increased PaO2/FIO2 by a mean of 94 torr and decreased AaDO2 (FIO2 = 1.0) by 105 torr in the 28 nonseptic patients. In the 29 septic patients, 5.1 cm H2O PEEP initially increased PaO2/FIO2 by 32 torr and decreased AsDO2 (FIO2 = 1.0) by 38 torr. The differences between the septic and nonseptic patients were statistically significant (P less than 0.001). Likewise, the long-term effect of similar levels of PEEP was in increasing PaO2/FIO2 by 142 torr and by 75 torr in the nonseptic and septic patients, respectively. The final reduction in AaDO2 (FIO2 = 1.0) was 163 torr and 87 torr in the nonseptic and septic patients, respectively. These differences between patient groups were also statistically significant (P less than 0.02). Mortality during PEEP was 15/29 and 3/28 in the septic and nonseptic patients, respectively. Overall mortality in the septic and nonseptic groups was 18/29 and 5/28, respectively. We conclude that ARDS with sepsis constitutes a more severe pulmonary insult than ARDS without sepsis, and/or that generalized sepsis creates a more prolonged pulmonary insult that makes it less amenable to PEEP. Thus, high levels of PEEP may be needed to treat ARDS associated with sepsis.