Paul J. Feustel

Effect of Hyperventilation, Mannitol, and Ventriculostomy Drainage on Cerebral Blood Flow after Head Injury

Therapies to lower intracranial pressure (ICP) after traumatic brain injury (TBI) include hyperventilation (HV), intravenous mannitol (IM), and cerebrospinal fluid drainage from a ventriculostomy (DV). To determine the effects of these therapies on cerebral blood flow (CBF), fiberoptic oximetry was used to measure jugular venous O2 saturation (SjvO2) as an index of the CBF to cerebral metabolic rate for O2 (CMRO2) ratio after IM (25 g IV for more than 5 min), DV (3 min), or HV (increase respiratory rate by 4) therapy for elevated ICP. Assuming CMRO2 is constant, changes in SjvO2 reflect changes in CBF. Continuous measurements of SjvO2, ICP, blood pressure, arterial O2 saturation, and end-tidal CO2 were obtained in 22 patients with a Glasgow Coma Scale score of 5.3 +/- 0.4 (mean +/- SD) in the first 5 days after TBI. Therapy was initiated a total of 196 times when ICP was > 15 mm Hg for > 5 minutes, and measurements made at 20 minutes after treatment were compared with those made just before. After DV, ICP fell in 90% of the observations by 8.6 +/- 0.7 mm Hg (mean +/- SEM, n = 119); after IM, ICP fell in 90% of the observations by 7.4 +/- 0.7 mm Hg (n = 43); and after HV, ICP fell in 88% of the observations by 6.3 +/- 1.2 mm Hg (n = 14). In patients where ICP fell, SjvO2 increased by 2.49 +/- 0.7% saturation (from 68.0 +/- 1.3%) with IM, but only by 0.39 +/- 0.4% saturation (from 67.2 +/- 0.9%) with DV.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of hematocrit on cardiopulmonary function after acute hemorrhage.

The ‘optimal’ hematocrit to which patients should be resuscitated after shock and trauma is controversial. To test the hypothesis that sufficient oxygen delivery can be provided at a lower hematocrit without impairing oxygen consumption or hemodynamic function, 25 patients were prospectively studied

CEREBRAL BLOOD FLOW AND BLOOD VOLUME IN RESPONSE TO O2 AND CO2 CHANGES IN NORMAL HUMANS

Changes in cerebral blood volume (CBV) after head injury may be an important determinant of intracranial pressure (ICP). To determine the normal response of CBV to hypoxemia, hypercapnia, and hypocapnia, eight normal subjects (5 males and 3 females; ages 25 to 43) were studied under these conditions. Cerebral blood volume was measured using an external collimated gamma detector to determine 99m-Tc-labeled red blood cell (RBC) activity in the intracranial vascular pool, and cerebral blood flow (CBF) was determined by internal carotid artery duplex scanning. Hypocapnia (Paco2 = 26.0 +/- 1.7 mm Hg, mean +/- SE) was achieved by hyperventilation, hypercapnia (Paco2 = 47.8 +/- 1.5 mm Hg) was achieved by inhalation of 6% CO2, and hypoxemia (Pao2 = 38.1 +/- 1.1 mm Hg, O2 saturation = 76.7 +/- 2.0%) was achieved by inhalation of 10% O2. Changes in CBF and CBV were determined by comparing the values in each condition to the immediately preceding period of normoxia and normocapnia. For conditions of hypocapnia, hypercapnia, and hypoxemia, the percentage of change in CBV was: -7.2 +/- 0.01, 12.8 +/- 0.01, and 5.2 +/- 0.03, respectively. The simultaneous percentage of change in CBF for the same conditions was -30.7 +/- 4.0, 29.5 +/- 9.2, and 18.4 +/- 6.9, respectively. For all conditions, changes in CBF were greater than changes in CBV; however, this was most pronounced during hypocapnia induced by hyperventilation. Because the change in CBV reflects the potential change in ICP in response to treatment, therapeutic hyperventilation may impair CBF to a greater degree than it reduces ICP.(ABSTRACT TRUNCATED AT 250 WORDS)

Is elevated creatinine level a contraindication to endovascular aneurysm repair

PURPOSE It is widely believed that chronic renal insufficiency (CRI) greatly increases the risk associated with endovascular abdominal aortic aneurysm repair (EVAR) and is a relative contraindication to the procedure and to the use of intra-arterial contrast agents (IACA). We reviewed a 5-year EVAR experience to determine whether the procedure and use of IACA have an important deleterious effect on renal function in patients with and without pre-existing CRI. METHODS Endovascular aneurysm repair (EVAR) was performed in 200 patients with a variety of endografts, with intra-arterial contrast agents. The patients were retrospectively assigned to three groups on the basis of preoperative serum creatinine concentration (Cr): group 1 (n = 108), Cr less than 1.5 mg/dL (normal range); group 2 (n = 65), Cr 1.5 to 2.0 mg/dL; group 3 (n = 27), Cr 2.1 to 3.5 mg/dL. No patients had undergone hemodialysis. In groups 2 and 3, patients received hydration perioperatively, and received mannitol intraoperatively; no nephrotoxic drugs were administered during the procedure, other than nonionic contrast agent (Omnipaque 350). RESULTS The incidence of postoperative complications between the three study groups was not statistically different. In group 1 a transient increase in serum Cr (>30% over baseline and >1.4 mg/dL) was noted in three patients (2.7%), two of whom (1.9%) required temporary hemodialysis and one (0.9%) who died of renal failure. In group 2 a transient increase in serum Cr was noted in two patients (3.1%); both patients (3.1%) required temporary hemodialysis, and one patient (1.5%) died of renal failure. In group 3 a transient increase in serum Cr was noted in two patients (7.4%); one patient (3.7%) required temporary hemodialysis, and one patient (3.7%) died of renal failure. Perioperative hypotension significantly increased the risk for elevated serum Cr and death (P <.05), and larger contrast volume was associated with an increase in serum Cr (P <.05) during the postoperative period. CONCLUSIONS EVAR with intra-arterial contrast agents can be accomplished in patients with chronic renal insufficiency who do not require dialysis, with limited and acceptable morbidity and mortality, similar to that observed with open aneurysm repair. Contrary to other reports in which perioperative precautions were not used, our study shows that with EVAR the risk for worsening renal failure, dialysis, and death is only slightly, and not significantly, greater in patients with preoperative chronic renal insufficiency compared with patients with normal renal function. Perioperative hypotension and increased contrast volume are significant risk factors for postoperative increase in serum Cr and death. With appropriate precautions such as averting perioperative hypotension and limiting the volume of nonionic contrast agents, elevated Cr need not be a contraindication to EVAR with intra-arterial contrast agents.

Remote distal arteriovenous fistula to improve infrapopliteal bypass patency

The results of the use of prosthetic materials for femorocrural bypass surgery have been less than optimal. The creation of a distal anastomotic arteriovenous fistula to augment blood flow and velocity through the graft is well known. However, it may create turbulence at the anastomosis and steal blood flow away from the distal artery. A canine model was developed to evaluate the effect of fistula size on graft/arterial hemodynamics. In 16 patients we have constructed a distal arteriovenous fistula, which is remote from the distal anastomosis, and we studied the effect of such fistulas on bypass patency and distal arterial hemodynamics. Patients selected for this procedure had multiple previously failed reconstructions and limb-threatening ischemia and did not have usable autogenous vein. Femorotibial bypass graft reconstructions were performed with polytetrafluoroethylene followed by the creation of a side-to-side arteriovenous fistula 5 to 15 cm below the distal anastomosis in the same artery and accompanying veins. We have achieved a 1-year patency of 67% with a 75% limb salvage rate. We also serially measured blood flow and velocity within the bypass, the arteriovenous fistula, and the distal outflow vessel using duplex scanning after surgery. Mean estimated blood flow through the bypass during the immediate postoperative period was 264 ml/min, the arteriovenous fistula was 157 ml/min, and the distal artery was 19 ml/min. Unlike an arteriovenous fistula created at the distal anastomosis, a remote distal arteriovenous fistula not only increases graft blood flow but also augments native arterial blood flow between the distal anastomosis and fistula and thus may improve distal limb perfusion.

Plasma fibronectin synthesis in normal and injured humans as determined by stable isotope incorporation.

In humans, plasma fibronectin decreases early after operative injury, burn, or trauma, followed by a rapid restoration with a secondary decline typically observed if such patients become septic. We determined the rate of plasma fibronectin and plasma fibrinogen synthesis in normal subjects and injured patients using a stable isotope incorporation technique with [15N]glycine. During a constant 14-h infusion of [15N]glycine, the enrichment of [15N]glycine in both the free plasma glycine precursor pool as well as the urinary hippurate pool was determined; the latter used as an estimate of intracellular hepatic precursor enrichment. [15N]Glycine enrichment in both plasma fibronectin and fibrinogen was also quantified. The synthesis rate (Js/V) expressed in micrograms per milliliter of plasma per hour and the fractional synthesis rate (FSR) expressed as percentage of the plasma pool produced per day were determined. In normal subjects, the FSR for plasma fibronectin using 15N enrichment into urinary hippurate was 35.35 +/- 1.46%/d, whereas the Js/V was 4.45 +/- 0.19 micrograms/ml plasma per h. In normal subjects, the FSR for plasma fibronectin using 15N enrichment into free plasma glycine was 14.73 +/- 0.63%/d, whereas the Js/V was 1.98 +/- 0.09 micrograms/ml plasma per h. Early (2-3 d) after burn injury, fibronectin synthesis was increased (Js/V = 5.74 +/- 0.36; P less than 0.05), whereas later after injury, fibronectin synthesis began to decline (Js/V = 3.52 +/- 0.24; P less than 0.05) based on 15N enrichment of urinary hippurate. In contrast, the Js/V and FSR of plasma fibrinogen, a well-documented acute-phase plasma protein, revealed a sustained elevation (P less than 0.05) after injury in both the trauma and burn patients. Thus, plasma fibronectin synthesis is elevated early postinjury, which may contribute to the rapid restoration of its blood level. However, once fibronectin levels have normalized, the synthesis of plasma fibronectin appears to decline.

A pediatric trauma center without a pediatric surgeon: a four-year outcome analysis.

Approximately 25% of all injury victims are in the pediatric age group, and one in four injured children will require a pediatric trauma center. According to the American College of Surgeons as well as many state guidelines, a level I pediatric trauma team should be directed by a pediatric surgeon. In 1986, the pediatric surgeon left our pediatric trauma center, but the center remained open under a cooperative effort by the adult trauma surgeons and pediatric intensivists. We have retrospectively reviewed the charts of all pediatric trauma patients (age less than or equal to 15 years) for the subsequent 4 years to determine the outcome of treatment without a pediatric surgeon. During this period, we treated 303 pediatric patients with multiple or serious single-system injuries. The mean age was 6.9 +/- 0.3 (SEM) years and 66% were boys. Falls were the cause of injury in 31% of the patients, with pedestrian/bicycle, motor vehicle crashes, and penetrating injuries resulting in 26%, 19%, and 3% of the injuries, respectively. The mean ISS was 15.6 +/- 0.8, and 73% of the patients had at least one AIS greater than or equal to 3. Surgical procedures were required in 48% of the patients. There were 27 deaths in this group, most commonly related to head injury (89%). The mean Pediatric Trauma Score of the patients who died was 1.6 +/- 0.8 and no patient with a Pediatric Trauma Score greater than 7 died.(ABSTRACT TRUNCATED AT 250 WORDS)

Outcome of adolescent trauma admitted to an adult surgical intensive care unit versus a pediatric intensive care unit.

BACKGROUND Institutional protocol designates the adult trauma service as the primary manager of all adolescent traumas (age 14-18 years) unless admission to the pediatric intensive care unit (PICU) occurs. In the PICU, primary care becomes the responsibility of the pediatric intensivist, with trauma service as a consultant. The purpose of this study was to identify differences in the management of adolescent trauma between the pediatric intensivist in the PICU, and the adult trauma team in the surgical intensive care unit (SICU). METHODS From January 1993 to January 1998, the medical records of all adolescent trauma patients requiring intensive care unit (ICU) management were reviewed. Depending on bed availability, patients younger than 16 were admitted to the PICU, and those 16 or older to the SICU. Demographic data obtained were age, sex, race, mechanism of injury, length of stay (LOS), ICU length of stay, days on mechanical ventilation, intubation, tracheotomy, intracranial pressure monitor, and Swan-Ganz catheter placement. Home discharge, rehabilitation placement, and death were recorded. Morbidity was measured using Injury Severity Score methodology, Pediatric Trauma Score, and Pediatric Risk of Mortality. RESULTS One hundred nine completed records were reviewed (SICU, n = 58; PICU, n = 51). There was no statistical difference in sex, race, mechanism of injury, ICU LOS, tracheotomy, and intracranial pressure monitor placements. There was no difference in morbidity, as measured by Injury Severity Score, Pediatric Trauma Score, and Pediatric Risk of Mortality score or in outcome measurements (death, rehabilitation placement). SICU patients were older (SICU, 16.9 +/- 1.0 years; PICU, 15.4 +/- 1.0 years; p < or = 0.1 Mann-Whitney U test), more likely to be intubated (SICU, n = 42; PICU, n = 24; p < or = 0.05 Fishers exact test), more likely to have pulmonary artery catheter placement (SICU, n = 7; PICU, n = 0), and had longer LOS (SICU, 12.2 +/- 10.6; PICU, 9.8 +/- 14.1; p < or = 0.03 Mann-Whitney U test). CONCLUSION Adolescent trauma patients admitted to the PICU were less likely to be intubated or have a Swan-Ganz catheter placed. They had decreased LOS and days of mechanical ventilation. There was no difference in outcome measurements.

OXYGEN DELIVERY AND CONSUMPTION IN HEAD-INJURED AND MULTIPLE TRAUMA PATIENTS

Critically ill patients often demonstrate that whole body oxygen consumption (VO2) is dependent on oxygen delivery (DO2). In this retrospective study, the relationship of VO2 to DO2 in patients with isolated head injury (HI, n = 18) was compared to that in patients with multiple trauma (MT, n = 60) without serious head injury. Mean pulmonary capillary wedge pressure, central venous pressure, arterial PCO2, cardiac index, and oxygen delivery were significantly lower in HI, but oxygen consumption was not different in the groups. In both groups, changes in DO2 (delta DO2) within each patient were significantly correlated with changes in VO2 (delta VO2) in that same patient. This relationship was not different between the HI patients, (delta VO2 = (0.20 +/- 0.02) delta DO2), and the MT patients (delta VO2 = (0.17 +/- 0.01) delta DO2). When these groups were further divided into those with high hematocrit (greater than 32%) and low hematocrit (less than 32%), HI patients with a low hematocrit demonstrated a steeper regression slope, with 26 +/- 3% of the DO2 change being reflected in the VO2 change. This was significantly greater than the slope in HI patients with high hematocrit (13 +/- 3%) and the MT patients at high (19 +/- 2%) or low (16 +/- 2%) hematocrits. These data show a correlation between changes in oxygen delivery and consumption that is similar in both head-injury patients and multiple trauma patients without serious head injury. This relationship was greatest in head-injured patients at low hematocrit. This relationship of VO2 and DO2 in both groups suggests an influence of neurohumoral factors rather than local tissue phenomena.(ABSTRACT TRUNCATED AT 250 WORDS)

Reorganization of a burn unit in response to underutilization: a critical assessment.

The incidence of burn injury in the United States has declined over the past few years, resulting in a dramatic decrease in the number of admissions to burn centers. This decrease has generated considerable concern, leading to a variety of proposals to modify burn units to control the cost of inpatient care. In 1986 Albany Medical Center Hospital, a 654-bed regional academic health sciences center, closed its burn unit and implemented a program to manage thermally injured patients in the intensive and progressive care areas of the medical center. A retrospective study was performed to compare patient outcomes and length of stay for the dedicated burn unit and the integrated burn program. Between the year before and the year after this change there was no significant difference in mortality rate, length of stay, or number of positive blood cultures. The relationship between burn severity and length of stay was unaltered by the burn program change. A comparison of data collected just after the change to those collected 2 years later again showed no difference, except that the annual census had dropped more than 50%. The results suggest that burn units can be converted to integrated burn programs without compromising patient care outcomes, although the lack of a cohesive burn team and the unavailability of beds designated for patients with burns ultimately resulted in a deemphasis of the burn program and consequent marked reduction in the number of patients with burns seen in the institution.