Timing of withdrawal of life-sustaining therapy in traumatic brain injury: exploring indicators of poor prognosis in adult and geriatric populations

OBJECTIVE

The lack of objective prognostication tools for severe traumatic brain injury (TBI) causes variability in the application of withdrawal of life-saving treatment (WLST). We aimed to determine whether WLST in persons with severe TBI is associated with known indicators of poor prognosis.

METHODS

This retrospective descriptive study focused on adult (18-64 years) and geriatric (≥65 years) patients with severe TBI who were admitted between August 1, 2018 and July 31, 2021 at a Level I trauma center and subsequently underwent WLST. The data collected from the Trauma Registry and electronic health records included information regarding demographic characteristics, injury severity, clinical variables, and length of hospital stay and were used to examine the indicators of poor prognosis and WLST.

RESULTS

Among the 164 participants with TBI who met the inclusion criteria, 61.0% were geriatric, and 122 (74.4%) patients had 0 or only 1 of the poor prognostic indicators prior to WLST. The non-geriatric group had more indicators of poor prognosis than the geriatric group. Participants with fewer indicators of poor prognosis had a longer length-of-stay.

CONCLUSION

In severe TBI cases, standardized prognostication tools can help guide informed WLST decisions, particularly in geriatric patients, improving care consistency.

When Should the Appropriateness of PEG be Questioned?

PURPOSE OF REVIEW

This review aims to analyze the evidence regarding the appropriateness of PEG placement in the following clinical situations: short bowel syndrome, head and neck cancer, dementia and palliative use in malignant bowel obstruction.

RECENT FINDINGS

Percutaneous endoscopic gastrostomy (PEG) tubes are placed for a variety of clinical indications by numerous different specialties. First described in 1980, PEG tubes are now the dominant method of enteral access. Typically, PEG tubes are technically feasible procedures that can come with significant risk for both minor and major complications. Therefore, it is important to perform an in-depth, patient specific risk-benefit analysis when considering insertion. By analyzing the current evidence regarding benefits in these situations, superimposed by the lens of biomedical ethics, we make recommendations that are accessible to any provider who may be a consultant or proceduralist, helping to provide informed care that is in the patient's best interest.

A core outcome set for damage control laparotomy via modified Delphi method

OBJECTIVES

Damage control laparotomy (DCL) remains an important tool in the trauma surgeon's armamentarium. Inconsistency in reporting standards have hindered careful scrutiny of DCL outcomes. We sought to develop a core outcome set (COS) for DCL clinical studies to facilitate future pooling of data via meta-analysis and Bayesian statistics while minimizing reporting bias.

METHODS

A modified Delphi study was performed using DCL content experts identified through Eastern Association for the Surgery of Trauma (EAST) 'landmark' DCL papers and EAST ad hoc COS task force consensus.

RESULTS

Of 28 content experts identified, 20 (71%) participated in round 1, 20/20 (100%) in round 2, and 19/20 (95%) in round 3. Round 1 identified 36 potential COS. Round 2 achieved consensus on 10 core outcomes: mortality, 30-day mortality, fascial closure, days to fascial closure, abdominal complications, major complications requiring reoperation or unplanned re-exploration following closure, gastrointestinal anastomotic leak, secondary intra-abdominal sepsis (including anastomotic leak), enterocutaneous fistula, and 12-month functional outcome. Despite feedback provided between rounds, round 3 achieved no further consensus.

CONCLUSIONS

Through an electronic survey-based consensus method, content experts agreed on a core outcome set for damage control laparotomy, which is recommended for future trials in DCL clinical research. Further work is necessary to delineate specific tools and methods for measuring specific outcomes.

LEVEL OF EVIDENCE

V, criteria.

PEP uP (Enhanced Protein-Energy Provision via the Enteral Route Feeding Protocol) in Surgical Patients-A Multicenter Pilot Randomized Controlled Trial

BACKGROUND

The Enhanced Protein-Energy Provision via the Enteral Route Feeding Protocol (PEP uP) has been shown to be feasible, safe, and effective in delivering significantly more energy/protein, though it has not been well studied in surgical/trauma patients. We hypothesized that PEP uP will effectively increase energy/protein delivery to critically ill surgical/trauma patients.

METHODS

This multicenter, prospective, randomized pilot study included adult patients admitted to surgical service who were expected to require mechanical ventilation for >24 hours and intensive care unit (ICU) care for >72 hours. Subjects were randomized to PEP uP or standard care. The PEP uP protocol includes initiation at goal rate, semi-elemental formula, prophylactic prokinetic agents, 24-hour volume-based goals, and modular protein supplementation. The primary outcome was nutrition adequacy over the first 12 ICU days.

RESULTS

Thirty-six subjects were enrolled. Slow recruitment resulted in early trial termination by the sponsor. There were no baseline differences between groups. PEP uP patients received more protein (106.8 ± 37.0 vs 78.5 ± 30.3 g/d, P = 0.02). Energy delivery was not significantly different (1400.0 ± 409.5 vs 1237.9 ± 459.1 kcal, P = 0.25). Vomiting was more common in the PEP uP patients (32% vs 12%, P = 0.03). PEP uP protocol violations included 2 patients (15.4%) not receiving pro-motility medications, 3 (23.1%) not receiving volume-based feeds as ordered, and 4 (30.8%) not receiving supplemental protein.

CONCLUSIONS

In surgical/trauma patients, PEPuP seemed to improve protein delivery but was difficult to implement successfully and may increase vomiting rates.

Impact of a TeamSTEPPS Trauma Nurse Academy at a Level 1 Trauma Center

PROBLEM

Nurses are crucial members of the team caring for the acutely injured trauma patient. Until recently, nurses and physicians gained an understanding of leadership and supportive roles separately. With the advent of a multidisciplinary team approach to trauma care, formal team training and simulation has transpired.

METHODS

Since 2007, our Level I trauma system has integrated TeamSTEPPS (Team Strategies & Tools to Enhance Performance & Patient Safety; Agency for Healthcare Research and Quality, Rockville, MD) into our clinical care, joint training of nurses and physicians, using simulations with participation of all health care providers. With the increased expectations of a well-orchestrated team and larger number of emergency nurses, our program created the Trauma Nurse Academy. This academy provides a core of experienced nurses with an advanced level of training while decreasing the variability of personnel in the trauma bay. Components of the academy include multidisciplinary didactic education, the Essentials of TeamSTEPPS, and interactive trauma bay learning, to include both equipment and drug use. Once completed, academy graduates participate in the orientation and training of General Surgery and Emergency Medicine residents' trauma bay experience and injury prevention activities.

RESULTS

Internal and published data have demonstrated growing evidence linking trauma teamwork training to knowledge and self-confidence in clinical judgment to team performance, patient outcomes, and quality of care.

IMPLICATIONS FOR PRACTICE

Although trauma resuscitations are stressful, high risk, dynamic, and a prime environment for error, new methods of teamwork training and collaboration among trauma team members have become essential.

Pretrauma Functional Independence Measure Score Predicts Survival in Geriatric Trauma

The Functional Independence Measure (FIM) is used by rehabilitation professionals to access disability. The FIM score combines both motor and cognitive parameters to assess a patient's level of required assistance in performing activities of daily living (ADL). The geriatric trauma patient is becoming an increasingly important cohort for trauma services. FIM has been shown to predict discharge outcomes and those at high risk for falls. We hypothesized pretrauma FIM scores may predict survival in the geriatric trauma population. This was a retrospective study of patients 65 years and older that were admitted to our Level I trauma center from July 1, 2006 to July 1, 2012. A total 941 patients underwent stepwise regression to identify those factors predicting survival. Age, Injury Severity Score, revised trauma score, body mass index, and pretrauma FIM scores (12-point scale) were studied. The primary outcome was survival. Statistical significance reached at P value <0.05. Multiple logistic regression analysis was then performed. A total of 1315 patients were identified and complete data were available on 941 patients. Mean age was 78 (SD ± 8.2), mean Injury Severity Score was 13(SD ± 8.7), and mean body mass index was 26. Overall mortality was 11 per cent. The odds ratio of survival was 3.532 (95% confidence interval = 2.191–5.718) times greater for every 1-point increase in the preadmission FIM expression score. Glasgow Coma Scale, revised trauma score, gender, and pretrauma FIM expression scores were predictive of survival in the geriatric trauma patient. Pretrauma FIM expression can be used to predict survival in the elderly trauma victim. Further study is needed to establish the role of FIM as part of trauma scoring systems.

Feeding the Open Abdomen

BACKGROUND

The purpose of this study was to determine if early enteral nutrition improves outcome for trauma patients with an open abdomen (OA).

METHODS

Retrospective review was used to identify 78 patients who required an OA for >or=4 hospital days, survived, and had available nutrition data. Demographic data and nutrition data comprising enteral nutrition initiation day and daily % target goal were collected. Patients were divided into 2 groups: early enteral feeding (EEN), initiated <or=4 days within celiotomy; and late enteral feeding (LEN; >4 days). Outcomes included infectious complications, early closure of the abdominal cavity (<8 days from original celiotomy), and fistula formation.

RESULTS

Fifty-three of 78 (68%) patients were men, with a mean age of 35 years; 74% had blunt trauma. Forty-three of 78 (55%) patients had EEN, whereas 35 of 78 (45%) had LEN. There was no difference with respect to demographics, injury severity, or infectious complication rates. Thirty-two of 43 (74%) patients with EEN had early closure of the abdominal cavity, whereas 17 of 35 (49%) patients with late feeding had early closure (p = .02). Four of 43 (9%) patients with EEN demonstrated fistula formation, whereas 9 of 35 (26%) patients with late feeding formed fistulae (p = .05). The EEN group had lower hospital charges (p = .04) by more than $50,000.

CONCLUSIONS

EEN in the OA was associated with (1) earlier primary abdominal closure, (2) lower fistula rate, (3) lower hospital charges.

The Impact of a Normoglycemic Management Protocol on Clinical Outcomes in the Trauma Intensive Care Unit

BACKGROUND

The purpose of this study was to determine if protocol-driven normoglycemic management in trauma patients affected glucose control, ventilator-associated pneumonia, surgical-site infection, and inpatient mortality.

METHODS

A prospective, consecutive-series, historically controlled study design evaluated protocol-driven normoglycemic management among trauma patients at Vanderbilt University Medical Center. Those mechanically ventilated > or =24 hours and > or =15 years of age were included. A glycemic-control protocol required insulin infusion therapy for glucose >110 mg/dL. Control patients included those who met criteria, were admitted the year preceding protocol implementation, and had hyperglycemia treated at the physician's discretion.

RESULTS

Eight hundred eighteen patients met study criteria; 383 were managed without protocol; 435 underwent protocol. The protocol group had lower glucose levels 7 of 14 days measured. After admission, both groups had mean daily glucose levels <150 mg/dL. No difference in pneumonia (31.6% vs 34.5%; p = .413), surgical infection (5.0% vs 5.7%; p = .645) or mortality (12.3% vs 13.1%; p = .722) occurred between groups. If one episode of blood glucose level was > or =150 mg/dL (n = 638; 78.0%), outcomes were worse: higher daily glucose levels for 14 days after admission (p < .001), pneumonia rates (35.9% vs 23.3%; p = .002), and mortality (14.6% vs 6.1%; p = .002). One or more days of glucose > or =150 mg/dL had a 2- to 3-fold increase in the odds of death. Protocol use in these patients was not associated with outcome improvement.

CONCLUSIONS

Protocol-driven management decreased glucose levels 7 of 14 days after admission without outcome change. One or more glucose levels > or =150 mg/dL were associated with worse outcome.

Provider Bias Impacts Tidal Volume Selection and Ventilator Days in Trauma Patients

BACKGROUND

The ARDSnet (Acute Respiratory Distress Syndrome Clinical Network) study demonstrated that low tidal volume (Vt) reduces mortality from ARDS. It is unknown whether low Vt is beneficial in at-risk trauma patients. We hypothesized that Vt selection would be low in accordance with ARDSnet criteria and that subsequent outcomes would be improved.

STUDY DESIGN

A 1-year retrospective observational study was conducted on all trauma patients aged 15 years and older and on mechanical ventilation for 48 hours or longer, excluding those with cardiopulmonary disease. Using maximum Vt, we identified low and high Vt groups (≤8 mL/predicted body weight (PBW) and >8 mL/PBW). Data collected included demographic characteristics, lengths of stay, ventilator and ICU days, ARDS, and other complications.

RESULTS

A total of 364 patients were identified and organized into low Vt (n = 181) and high Vt (n = 183) groups. There was no difference between groups in age, Injury Severity Score, Glasgow Coma Scale, or mechanism of injury. The rate of ARDS was the same in each group. Patients with a high Vt had lower PBW (63.1 ± 8.8 vs 71.7 ± 6.9; p < 0.001), higher BMI(29.7 ± 6.9 kg/m(2) vs 26.6 ± 6.5 kg/m(2); p < 0.001), and were more likely to be female. Height was inversely correlated with Vt (r(2) = -0.579; p < 0.001). The high Vt group experienced longer ICU stays (9.9 ± 8.8 days vs 8.1 ± 7.9 days; p = 0.045) and more ventilator days (8.55 ± 10.5 days vs 6.14 ± 7.4 days; p = 0.015).

CONCLUSIONS

Trauma patients receiving high Vt were shorter, had higher BMI, and were more likely to be female. The consequences included longer ICU stays and more ventilator days. Formal calculation of PBW and subsequent Vt is advocated.

Dynamic multiplanar real time ultrasound guided infraclavicular subclavian vein catheterization

Ultrasound guided vascular access has been well-characterized as a safe and effective technique for internal jugular and femoral vein catheterization. However, there is limited experience with the use of ultrasound to access the infraclavicular subclavian vein. Multiple ultrasound techniques do exist to identify the subclavian vein, but real time access is limited by vessel identification in a single planar view. To overcome this limitation, a novel technique of ultrasound guided infraclavicular subclavian vein catheterization using a real time multiplanar approach has been developed. The initial experience with this approach is described. A single surgeon used combined oblique, transverse, and longitudinal views along with Doppler color flow images to both define the infraclavicular anatomy and to obtain subclavian vein access in 42 adult patients (20 M/22 F and 22 L/20 R) with a mean body mass index of 29.2 (range = 18.9-55.4). Chest x-ray was obtained to confirm position and to rule out pneumothorax. Subclavian vein cannulation was achieved in 100 per cent of patients; subsequent catheterization was successful in 92.9 per cent. The number of attempts required for cannulation averaged 1.3 (range = 1-5), and decreased after a five patient learning curve. No patient developed a pneumothorax, hematoma, or cannula malposition. Ultrasound guided multiplanar infraclavicular subclavian vein access appears to be a safe and effective adjunct for central line placement.

Dynamic Multiplanar Real Time Ultrasound Guided Infraclavicular Subclavian Vein Catheterization

Ultrasound guided vascular access has been well-characterized as a safe and effective technique for internal jugular and femoral vein catheterization. However, there is limited experience with the use of ultrasound to access the infraclavicular subclavian vein. Multiple ultrasound techniques do exist to identify the subclavian vein, but real time access is limited by vessel identification in a single planar view. To overcome this limitation, a novel technique of ultrasound guided infraclavicular subclavian vein catheterization using a real time multiplanar approach has been developed. The initial experience with this approach is described. A single surgeon used combined oblique, transverse, and longitudinal views along with Doppler color flow images to both define the infraclavicular anatomy and to obtain subclavian vein access in 42 adult patients (20 M/22 F and 22 L/20 R) with a mean body mass index of 29.2 (range = 18.9–55.4). Chest x-ray was obtained to confirm position and to rule out pneumothorax. Subclavian vein cannulation was achieved in 100 per cent of patients; subsequent catheterization was successful in 92.9 per cent. The number of attempts required for cannulation averaged 1.3 (range = 1–5), and decreased after a five patient learning curve. No patient developed a pneumothorax, hematoma, or cannula malposition. Ultrasound guided multiplanar infraclavicular subclavian vein access appears to be a safe and effective adjunct for central line placement.

Utilization and determinants of palliative care in the trauma intensive care unit: results of a national survey

BACKGROUND

There is a paucity of data evaluating utilization of palliative care in trauma intensive care units.

AIM

We sought to determine current indications and determinants of palliative care consultation in the trauma intensive care units.

DESIGN

Using a cross-sectional assessment, we surveyed trauma surgeons to understand indications, benefits, and barriers trauma surgeons perceive when consulting palliative care.

SETTING/PARTICIPANTS

A total of 1232 surveys were emailed to all members of the Eastern Association for the Surgery of Trauma.

RESULTS

A total of 362 providers responded (29% response rate). Majority of respondents were male (n = 287, 80.2%) and practiced in Level 1 (n = 278, 77.7%) trauma centers. Most common indicators for referral to palliative care were expected survival 1 week to 1 month, multisystem organ dysfunction >3 weeks, minimal neurologic responsiveness >1 week, and referral to hospice. In post hoc analysis, there was a significant difference in frequency of utilization of palliative care when respondents had access to board-certified palliative care physicians (χ(2) = 56.4, p < 0.001). Although half of the respondents (n = 199, 55.6%) reported palliative care consults beneficial all or most of the time, nearly still half (n = 174, 48.6%) felt palliative care was underutilized. Most frequent barriers to consultation included resistance from families (n = 144, 40.2%), concerns that physicians were "giving up" (n = 109, 30.4%), and miscommunication of prognosis (n = 98, 27.4%) or diagnosis (n = 58, 16.2%) by the palliative care physician.

CONCLUSION

Although a plurality of trauma surgeons reported palliative care beneficial, those surveyed indicate that palliative care is underutilized. Barriers identified provide important opportunities to further appropriate utilization of palliative care services.

Subcutaneous versus intravenous insulin therapy for glucose control in non-diabetic trauma patients. A randomized controlled trial

WHAT IS KNOWN AND OBJECTIVE

Hyperglycaemia in trauma patients admitted to the intensive care unit (ICU) is associated with increased morbidity and mortality. Our pilot study is a prospective randomized controlled trial comparing the impact of two glucose control regimens on outcomes in non-diabetic trauma patients admitted with hyperglycaemia to the ICU.

METHODS

Trauma patients with blood glucose levels (BGLs) ≥7·8 mm within the first 48 h of the hospital admission were randomized to receive intermittent SQ or continuous IV insulin to maintain BGLs between 4·4 and 6·1 mm. We excluded diabetics on the basis of history, or a glycosylated haemoglobin ≥6% on admission. We compared the effect of SQ vs. IV insulin therapy on the ICU length of stay (ILOS).

RESULTS AND DISCUSSION

A total of 58 patients were included in the study. The SQ and IV groups were comparable in terms of age, gender, injury severity, revised trauma, Glasgow coma scores and type of trauma (blunt vs. penetrating). There was no significant difference between the two treatment groups in the ILOS (3 vs. 2 days, P = 0·084), hospital length of stay (8 vs. 6, P = 0·09), ventilator support days (6 vs. 3, P = 0·98), requirement for blood transfusion (P = 0·66), rates of infections (P = 0·70), acute kidney injury (P = 0·99) and mortality (P = 0·61).

WHAT IS NEW AND CONCLUSION

There was no difference between SQ and IV insulin therapy in the ILOS in non-diabetic trauma patients.

Nutrition and the open abdomen

Adequate nutrition support is critical in the management of patients with an open abdomen. Despite the literature supporting its use in trauma patients, provider concerns and clinical controversies remain regarding the early administration and long-term sequelae of enteral nutrition (EN) therapy in these patients. The purpose of this article is to review the clinical concepts behind the use of the open abdomen, as well as examine the altered nutrition requirements associated with the maintenance of a temporary laparostomy. The rationale for early EN is described, as well as the pros and cons surrounding the use of supplemental parenteral nutrition in those patients unable to meet nutrition goals enterally in a reasonable time frame. Finally, an open abdomen nutrition support algorithm is provided as part of the critical care plan in these patients who represent the sickest of surgical patients.

Obesity and pulmonary complications in critically injured adults

BACKGROUND

Pulmonary complications following injury significantly contribute to subsequent mortality. Obese patients have preexisting risk factors for pulmonary complications, and are at risk for these complications following elective surgery. Whether or not obesity contributes to pulmonary complications after critical injury is poorly understood.

METHODS

A secondary analysis of a prospective cohort study of critically injured adults requiring at least 48 h of intensive care was performed. Patients were classified into the following body mass index groups: < or = 18.5 kg/m2 (underweight); 18.5 to 24.9 kg/m2 (normal); 25 to 29.9 kg/m2 (overweight); 30.0 to 39.9 kg/m2 (obese); and > or = 40.0 kg/m2 (severely obese). Outcomes included the rates of ARDS and pneumonia, the placement of a tracheostomy tube, and in-hospital mortality rate.

RESULTS

A total of 1,291 patients were available for analysis, and 30% of these patients were classified as either obese or severely obese. The age-, gender-, and severity-adjusted rate of ARDS was lower in severely obese patients (odds ratio, 0.36; 95% confidence interval [CI], 0.13 to 0.99) compared to normal weight patients. The rates of pneumonia (37%), tracheostomy (10%), and in-hospital mortality (11%) did not differ among the groups. Despite no difference in pulmonary complications, the severely obese group had an ICU length of stay that was 4.8 days (95% CI, 1.8 to 7.7 days) longer than the normal weight group.

CONCLUSION

Obesity does not appear to be an independent risk factor for increased pulmonary complications after critical injury, but severely obese patients are likely to require longer ICU stays.

The early work-up for isolated ligamentous injury of the cervical spine: does computed tomography scan have a role?

BACKGROUND

Helical computed tomography (HCT) scan is the preferred modality for diagnosing fractures of the cervical spine in blunt trauma. We hypothesize that HCT can be used as a screening tool for isolated ligamentous injury (LI) in blunt trauma.

METHODS

A prospective, consecutive series study design was used to include patients that could not have their cervical spine cleared clinically. All patients underwent HCT (occiput-T1) and plain radiographs (PR) with five views of the cervical spine. Patients with clinical or radiographic abnormalities without fracture underwent cervical magnetic resonance imaging (MRI). Demographic and outcome data were collected. The attending radiologist's interpretation was used for clinical management. Three neuroradiologists in a blinded fashion re-reviewed the studies (HCT, PR, and MRI) of the MRI subgroup.

RESULTS

One thousand five hundred seventy-seven patients met the study criteria. Two hundred seventy-eight had 416 cervical spine fractures. PR failed to identify 299 of 416 (72%) cervical spine fractures in 208 of 278 (74.8%) patients. Of the 1,299 (82%) patients who had no fracture, 85 (6.5%) required an MRI. The mean time from admission to MRI was 3 days for the LI subgroup. Of these, 21 of 85 (25%) had LI by MRI. Seven of 21 (33.3%) patients had an abnormal HCT versus 3 of 21 (14.3%) patients who had an abnormal PR. Four of 85 (4.7%) patients had spinal cord injury without radiographic abnormality. One (1.2%) patient required surgical stabilization of LI, as seen on all studies performed (PR, HCT, and MRI). Sensitivities for PR and HCT for LI were 16% and 32%, respectively. Negative predictive values for PR and HCT for LI were 74% and 78%, respectively. Measurements of interrater reliability for MRI, HCT, and PR had kappa values of 0.60, 0.14, and 0.41, respectively.

CONCLUSION

HCT is the most sensitive, specific, and cost-effective modality for screening the cervical spine bony injuries, but it is not an effective modality for screening for cervical LI. MRI is clearly superior to HCT for LI. The indications for MRI include abnormalities on HCT, neurologic deficits, cervical pain or tenderness on examination, or the inability to clear the cervical spine in the obtunded patient. With the current state of the art technology, we have redefined the definition of spinal cord injury without radiographic abnormality to include spinal cord injuries without boney injuries or LI.

Postoperative rhabdomyolysis with bariatric surgery

Rhabdomyolysis has been reported in all postoperative patients including those in prone, supine, lithotomy and lateral decubitus positions. Only a few reports suggest that bariatric surgical patients are at risk for rhabdomyolysis. We describe a male (BMI 69 kg/m2) who underwent an uneventful open Roux-en-Y gastric bypass for weight reduction lasting 5 hours. Postoperatively the patient suffered oliguria. Evaluation included subjective pain in both hips, a normal temperature and physical examination, creatinine increase to 3.5 mg/dl, CPK levels as high as 41,000 IU/L, and urinalysis showing a large amount of occult blood with 5-7 RBCs/HPF. Intravenous hydration with 0.9% normal saline, bicarbonate, and mannitol demonstrated initial success, but the patient eventually developed renal failure, respiratory distress, and tachycardia leading to cardiac arrest. Prior to his death, intraoperative evaluation demonstrated intact anastomoses. Obese patients undergoing bariatric surgery should be considered at risk for rhabdomyolysis, especially in view of prolonged surgeries, difficult physical examination, low volume status, and larger or immobile patients.

Insulin-like growth factor-I inhibits endogenous acetylcholine release from the rat hippocampal formation: possible involvement of GABA in mediating the effects

Evidence suggests that insulin-like growth factor-I (IGF-I) plays an important role during brain development and in the maintenance of normal as well as activity-dependent functioning of the adult brain. Apart from its trophic effects, IGF-I has also been implicated in the regulation of brain neurotransmitter release thus indicating a neuromodulatory role for this growth factor in the central nervous system. Using in vitro slice preparations, we have earlier reported that IGF-I potently inhibits K(+)-evoked endogenous acetylcholine (ACh) release from the adult rat hippocampus and cortex but not from the striatum. The effects of IGF-I on hippocampal ACh release was sensitive to the Na(+) channel blocker tetrodotoxin, suggesting that IGF-I might act indirectly via the release of other transmitters/modulators. In the present study, we have characterized the possible involvement of GABA in IGF-I-mediated inhibition of ACh release and measured the effects of this growth factor on choline acetyltransferase (ChAT) activity and high-affinity choline uptake in the hippocampus of the adult rat brain. Prototypical agonists of GABA(A) and GABA(B) receptors (i.e. 10 microM muscimol and 10 microM baclofen) inhibited, whereas the antagonists of the respective receptors (i.e. 10 microM bicuculline and 10 microM phaclofen) potentiated K(+)-evoked ACh release from rat hippocampal slices. IGF-I (10 nM) inhibited K(+)- as well as veratridine-evoked ACh release from rat hippocampal slices and the effect is possibly mediated via the activation of a typical IGF-I receptor and the subsequent phosphorylation of the insulin receptor substrate-1 (IRS-1). The inhibitory effects of IGF-I on hippocampal ACh release were not additive to those of either muscimol or baclofen, but were attenuated by GABA antagonists, bicuculline and phaclofen. Additionally, in contrast to ACh release, IGF-I did not alter either the activity of the enzyme ChAT or the uptake of choline in the hippocampus. These results, taken together, indicate that IGF-I, under acute conditions, can decrease hippocampal ACh release by acting on the typical IGF-I/IRS receptor complex while having no direct effect on ChAT activity or the uptake of choline. Furthermore, the evidence that effects of IGF-I could be modulated, at least in part, by GABA antagonists suggest that the release of GABA and the activation of its receptors may possibly be involved in mediating the inhibitory effects of IGF-I on hippocampal ACh release.

Prophylactic positive end-expiratory pressure and reduction of postoperative blood loss in open-heart surgery

BACKGROUND

Various strategies have been introduced to minimize transfusion requirements in cardiac surgery. One strategy is the use of positive end-expiratory pressure (PEEP) postoperatively. Currently, PEEP is used in many centers to control increased mediastinal chest-tube drainage. The purpose of this study was to determine whether the prophylactic application of a PEEP of 10 cm H2O compared with a PEEP of 5 cm H2O in the immediate postoperative period reduces mediastinal chest-tube output without causing clinically significant hemodynamic compromise.

METHODS

We prospectively studied 84 elective coronary artery bypass grafted patients and randomized treatment groups to a PEEP of 5 or 10 cm H2O. Forty-four patients were assigned a PEEP of 5 cm H2O and 40 patients received a PEEP of 10 cm H2O.

RESULTS

Preoperative, intraoperative, and postoperative demographics were similar between groups. There was no statistically significant difference between the 5 cm H2O PEEP group and the 10 cm H2O PEEP group with regard to chest-tube output at 6 hours, at 24 hours, or in total output. There was no statistical difference in hemoglobin levels immediately postoperatively, at 8 hours, or at 36 hours.

CONCLUSIONS

This study demonstrates that the use of postoperative PEEP levels of 10 cm H2O, although safe, does not reduce chest-tube output or transfusion requirements.

Is helical computed tomography effective for diagnosis of blunt aortic injury?

Computed tomography has had a questionable role in diagnosing blunt aortic injury (BAI). The objective of this study was to determine the effectiveness of helical computed tomography of the thorax (HCTT) for detection of BAI. Trauma Registry data and medical records were reviewed for 2,854 patients admitted over a 32-month period. A total of 243 patients were identified at risk for BAI. Patients were evaluated for BAI because of chest radiograph, physical examination, or clinical suspicion. Eleven of 2,834 patients sustained BAI. Of 243 patients who sustained blunt torso trauma, 232 patients underwent HCTT. Eleven underwent aortography without HCTT. Sixteen patients had an abnormal HCTT, revealing 9 patients with BAI. No delayed BAI were encountered. HCTT effectively screens for BAI. Aortography can be more specifically applied as a diagnostic study when preceded by HCTT. HCTT should not be used as solitary study for BAI as some injuries identified by HCTT do not represent BAI.

Prolonged morphine treatment targets delta opioid receptors to neuronal plasma membranes and enhances delta-mediated antinociception

Opioid receptors are known to undergo complex regulatory changes in response to ligand exposure. In the present study, we examined the effect of morphine on the in vitro and in vivo density and trafficking of delta opioid receptors (deltaORs). Prolonged exposure (48 hr) of cortical neurons in culture to morphine (10 microm) resulted in a robust increase in the internalization of Fluo-deltorphin, a highly selective fluorescent deltaOR agonist. This effect was mu-mediated because it was entirely blocked by the selective mu opioid receptor antagonist d-Phe-Cys-Tyr-d-Trp-Orn-Thr-Pen-Thr-NH(2) and was reproduced using the selective mu agonist fentanyl citrate. Immunogold electron microscopy revealed a marked increase in the cell surface density of deltaORs in neurons exposed to morphine, indicating that the increase in Fluo-deltorphin internalization was caused by increased receptor availability. Prolonged morphine exposure had no effect on deltaOR protein levels, as assessed by immunocytochemistry and Western blotting, suggesting that the increase in bioavailable deltaORs was caused by recruitment of reserve receptors from intracellular stores and not from receptor neosynthesis. Complementary in vivo studies demonstrated that chronic treatment of adult rats with morphine (5-15 mg/kg, s.c., every 12 hr) similarly augmented targeting of deltaORs to neuronal plasma membranes in the dorsal horn of the spinal cord. Furthermore, this treatment markedly potentiated intrathecal d-[Ala(2)]deltorphin II-induced antinociception. Taken together, these results demonstrate that prolonged stimulation of neurons with morphine markedly increases recruitment of intracellular deltaORs to the cell surface, both in vitro and in vivo. We propose that this type of receptor subtype cross-mobilization may widen the transduction repertoire of G-protein-coupled receptors and offer new therapeutic strategies.

Nitric Oxide Synthase as a Marker in Colorectal Carcinoma

Elevated inducible nitric oxide synthase (iNOS) activity has been found in 60 per cent of colon adenomas and 20 to 50 per cent of adenocarcinomas. We postulated that high levels of iNOS may increase the invasive and metastatic potential of colon carcinoma and could be indicative of survival potential. Data were reviewed for 52 patients with colorectal carcinoma diagnosed in 1991 and 1992. Specimens were stained for iNOS and catalogued as low-activity staining (LAS) or high-activity staining (HAS) on the basis of visual evaluation by three pathologists. Thirty patients were LAS and 22 HAS. Age, sex, preoperative carcinoembryonic antigen, tumor and nodal status, and American Joint Committee on Cancer staging were not different between groups. Forty-six per cent of the HAS group remained alive after 5 years versus 71 per cent in the LAS group. Survival was significantly lower and metastatic status significantly higher in the HAS group. Results indicated that iNOS activity may be a prognostic indicator of long-term survival potential after treatment for colon cancer. In addition results suggested that metastasis was greater in colon carcinoma specimens that maintain an activated iNOS and that these cells clinically react more aggressively. Conclusions are tempered by the fact that results were based on a limited sample size.

Nitric oxide synthase as a marker in colorectal carcinoma

Elevated inducible nitric oxide synthase (iNOS) activity has been found in 60 per cent of colon adenomas and 20 to 50 per cent of adenocarcinomas. We postulated that high levels of iNOS may increase the invasive and metastatic potential of colon carcinoma and could be indicative of survival potential. Data were reviewed for 52 patients with colorectal carcinoma diagnosed in 1991 and 1992. Specimens were stained for iNOS and catalogued as low-activity staining (LAS) or high-activity staining (HAS) on the basis of visual evaluation by three pathologists. Thirty patients were LAS and 22 HAS. Age, sex, preoperative carcinoembryonic antigen, tumor and nodal status, and American Joint Committee on Cancer staging were not different between groups. Forty-six per cent of the HAS group remained alive after 5 years versus 71 per cent in the LAS group. Survival was significantly lower and metastatic status significantly higher in the HAS group. Results indicated that iNOS activity may be a prognostic indicator of long-term survival potential after treatment for colon cancer. In addition results suggested that metastasis was greater in colon carcinoma specimens that maintain an activated iNOS and that these cells clinically react more aggressively. Conclusions are tempered by the fact that results were based on a limited sample size.

Colonoscopy in octogenarians and older patients

INTRODUCTION

Colonoscopy in the elderly has been considered by many to be risky because of mechanical bowel preparation and dehydration, electrolyte disturbances, conscious sedation, and hypoxic complications. We hypothesized that colonoscopy in octogenarians and older patients is a safe procedure.

MATERIALS AND METHODS

A retrospective review of 803 patients who underwent colonoscopy from January 1997 to October 1997 was performed. The patients were grouped by age: group A (17-49 years) had 166 patients (20%); group B (50-79 years) had 534 patients (67%); and group C (80 years and older) had 103 patients (13%). Results were considered significant at p value less than 0.05 unless otherwise noted.

RESULTS

Blood in the stool (84%) and history of colonic vascular disease (5.8%) were the most common indication in group C (84%). Colonoscopy was used in group A (18%) more often than in the other groups to rule out inflammatory bowel disease. History of colon polyps was a more common indication in group B (20%) than in the other groups. Group A had a significantly higher incidence of normal examinations (84%) and diagnosis of inflammatory bowel disease (14%). Group B had a higher incidence of polyps than the other groups. Group C had the highest incidence of vascular disease (15%). Diverticular disease and carcinoma were more common in groups B (37%) and C (52%). The amount of sedation in the groups did not significantly differ. Completion of the colonoscopy to the cecum or anastomotic sites did not differ among the groups (p > 0.05), nor did complication rates among groups (p > 0.05).

CONCLUSIONS

Colonoscopy is safe in octogenarians and older patients. Age does not, by itself, confer an increased risk to the procedure.

Traumatic carotid artery dissection: a significant incidental finding

Blunt traumatic carotid artery dissection remains controversial in terms of diagnostic screening, reported incidence, and management. Treatment options include observation, anticoagulation and endovascular stenting, and aggressive surgical repair of the carotid artery injury. Blunt traumatic carotid artery dissections were reviewed through a retrospective study of trauma registry records. Seven patients were identified from 3342 patients over 3 years. Six patients were identified incidentally during magnetic resonance imaging (MRI) cervical spine/brain screening and one patient during angiographic evaluation for possible penetrating neck injury without MRI/magnetic resonance angiography (MRA). A total of 189 patients underwent MRI screening over this 3-year period, demonstrating a relative incidence of 3.7 per cent, contrasting with the reported incidence of 0.08 to 0.4 per cent for all trauma patients. All seven patients suffered severe head injuries (mean Glasgow Coma Score = 4.7) requiring mean intensive care unit and hospital stays of 15.6 and 23.7 days, respectively. None of the patients showed evidence of stroke with CT scanning on presentation. None of the patients demonstrated clinical focal neurologic signs or symptoms indicating carotid injury or stroke. Six patients survived their acute trauma and were discharged to rehabilitation after initiation of observation (one patient) or anticoagulation (five patients). All six patients showed neurological improvement without deterioration clinically or radiographically. In conclusion we propose early aggressive screening through MRI/MRA of severely injured patients to detect occult carotid artery dissections. Conservative medical treatment for this occult injury has been effective in this series of patients.

Traumatic Carotid Artery Dissection: A Significant Incidental Finding

Blunt traumatic carotid artery dissection remains controversial in terms of diagnostic screening, reported incidence, and management. Treatment options include observation, anticoagulation and endovascular stenting, and aggressive surgical repair of the carotid artery injury. Blunt traumatic carotid artery dissections were reviewed through a retrospective study of trauma registry records. Seven patients were identified from 3342 patients over 3 years. Six patients were identified incidentally during magnetic resonance imaging (MRI) cervical spine/brain screening and one patient during angiographic evaluation for possible penetrating neck injury without MRI/magnetic resonance angiography (MRA). A total of 189 patients underwent MRI screening over this 3-year period, demonstrating a relative incidence of 3.7 per cent, contrasting with the reported incidence of 0.08 to 0.4 per cent for all trauma patients. All seven patients suffered severe head injuries (mean Glasgow Coma Score = 4.7) requiring mean intensive care unit and hospital stays of 15.6 and 23.7 days, respectively. None of the patients showed evidence of stroke with CT scanning on presentation. None of the patients demonstrated clinical focal neurologic signs or symptoms indicating carotid injury or stroke. Six patients survived their acute trauma and were discharged to rehabilitation after initiation of observation (one patient) or anticoagulation (five patients). All six patients showed neurological improvement without deterioration clinically or radiographically. In conclusion we propose early aggressive screening through MRI/MRA of severely injured patients to detect occult carotid artery dissections. Conservative medical treatment for this occult injury has been effective in this series of patients.

Enzyme activity and protein of multiple forms of choline acetyltransferase: effects of calyculin A and okadaic acid

Choline acetyltransferase (ChAT) appears to exist in multiple forms, three of which can be isolated biochemically as cytosolic (cChAT), ionically-membrane bound (ibChAT) and non-ionic membranous (mChAT). In this study, we first examined whether the quantitative distribution of enzyme protein and enzyme activity was the same. Enzyme activity and ChAT protein distributed similarly: the majority of ChAT activity and protein were found in cChAT followed by mChAT and least activity and amount were in ibChAT. Our second objective was to investigate the effects of calyculin A or okadaic acid on the subcellular distribution of ChAT activity and amount from rat hippocampal formation. Calyculin A and okadaic acid decreased significantly (p < 0.01) cytosolic and membranous ChAT activity; ionically-bound ChAT was not significantly (p > 0.67) different from control. Removal of calyculin A or okadaic acid restored cytosolic ChAT activity (p > 0.9 as compared to control), but not membranous enzyme activity (p < 0.05 as compared to control). The immunoreactive cytosolic ChAT was reduced significantly (p < 0.01) by calyculin A and okadaic acid. Enzyme amount of membranous ChAT was decreased significantly by calyculin A (p < 0.01) and okadaic acid (p < 0.001). Enzyme amount of ionically-bound ChAT was not changed (p > 0.99) by either of these two phosphatase inhibitors. This investigation demonstrates that alterations in ChAT activity of each subfraction parallel changes in enzyme amounts in the same fractions.

Effects of calyculin A and okadaic acid on acetylcholine release and subcellular distribution in rat hippocampal formation

The mechanisms regulating the compartmentation of acetylcholine (ACh) and the relationship between transmitter release and ACh stores are not fully understood. In the present experiments, we investigated whether the inhibitors of serine/threonine phosphatases 1 and 2A, calyculin A and okadaic acid, alter subcellular distribution and the release of ACh in rat hippocampal slices. Calyculin A and okadaic acid significantly (p < 0.05) depleted the occluded ACh of the vesicular P3 fraction, but cytoplasmic ACh contained in the S3 fraction was not significantly affected. The P3 fraction is known to be heterogeneous; calyculin A and okadaic acid reduced significantly (p < 0.05) the amount of ACh recovered with a monodispersed fraction (D) of synaptic vesicles, but the other nerve terminal bound pools (E-F and G-H) were not so affected. K+-evoked ACh release decreased significantly (p < 0.01) in the presence of calyculin A and okadaic acid, suggesting that fraction D's vesicular store of ACh contributes to transmitter release. The loss of ACh from synaptic vesicle fractions prepared from tissue exposed to phosphatase inhibitors appeared not to result from a reduced ability to take up ACh. Thus, when tissue was allowed to synthesize [3H]ACh from [3H]choline, the ratio of [3H]ACh in the S3 to P3 fractions was not much changed by exposure of tissue to calyculin A or okadaic acid; furthermore, the specific activity of ACh recovered from the D fraction was not reduced disproportionately to that of cytosolic ACh. The changes are considered to reflect reduced synthesis of ACh by tissue treated with the phosphatase inhibitors, rather than an effect on vesicle uptake mechanisms. Thus, exposure of tissue to calyculin A or okadaic acid appears to produce selective depletion of tissue ACh content in a subpopulation of synaptic vesicles, suggesting that phosphatases play a role in ACh compartmentation.

Synaptic inhibitory effects of edrophonium on sympathetic ganglionic transmission

PURPOSE

To evaluate the effect of edrophonium on synaptic transmission in the superior cervical ganglion.

METHODS

In anaesthetized rats the effect of edrophonium on synaptic transmission was studied in vitro by testing whether it blocks the compound action potential recorded from postganglionic fibres evoked by stimulation of preganglionic axons. The superior cervical ganglion was excised and the cervical sympathetic trunk and internal carotid nerve were used for stimulating and recording, respectively. Drugs superfused included edrophonium (0.1-500 microM), neostigmine (0.1-10 microM), and muscarinic M1 and M2 antagonists pirenzepine and AFDX-116 (200 nM-10 microM), respectively. To evaluate a presynaptic action, the effect of edrophonium on basal and high-K+ (35 mM) evoked release of [3H]ACh from the superior cervical ganglion was studied in vitro. To evaluate a postsynaptic action, edrophonium's effect on postganglionic nerve discharge in response to arterial injection of ACh (100 micrograms) into the superior cervical ganglion was determined in vivo.

RESULTS

Edrophonium (10-500 microM) decreased the compound action potential amplitude (ED50 163.5 microM). A decrease was not produced by neostigmine, nor was it reversed by pirenzepine or AFDX-116. Edrophonium blocked postganglionic cell firing in response to exogenously administered ACh. Although edrophonium did not affect basal or high-K+ evoked ACh release, when the evoked increase was calculated as a multiple of the basal release, it caused approximately a 30% (P < 0.005) reduction.

CONCLUSIONS

Edrophonium blocks ganglionic cholinergic transmission postsynaptically and, possibly, presynaptically. The mechanism(s) by which this occurs does not appear to involve inhibition of cholinesterase, or activation of M1 or M2 receptor subtypes.

Translational inhibition in vitro of human papillomavirus type 16 L2 mRNA mediated through interaction with heterogenous ribonucleoprotein K and poly(rC)-binding proteins 1 and 2

Human papillomavirus (HPV) type 16 belongs to the group of "high risk" HPV types that are frequently detected in anogenital cancers. The expression of HPV-16 late genes encoding the virus capsid proteins L1 and L2 is restricted to terminally differentiated epithelial cells in the superficial layers of the squamous epithelium. We have previously identified negative elements in the 3' end of L2 RNA that act in cis to reduce mRNA utilization without substantially affecting mRNA levels. The experiments reported here demonstrate the interaction of cellular proteins with an inhibitory sequence present in the coding region of the L2 mRNA. Using RNA gel shift assays and UV cross-linking, we have detected three cellular proteins interacting specifically with the sense strand of the L2 mRNA, two of which were identified as heterogeneous ribonucleoprotein K (hnRNP K) and the poly(rC) binding- protein (PCBP). Recombinant hnRNP K, PCBP-1, and PCBP-2 that were over expressed in bacteria and partially purified bound to the HPV-16 L2 mRNA in a sequence-specific manner. Interestingly, PCBP-1, PCBP-2, and hnRNP K specifically and efficiently inhibited translation of the HPV-16 L2 mRNA in vitro. Therefore, these proteins may play an important role in the regulation of HPV-16 late gene expression and virus production in vivo.

Amyloid beta-peptide inhibits high-affinity choline uptake and acetylcholine release in rat hippocampal slices

The characteristic pathological features of the postmortem brain of Alzheimer's disease (AD) patients include, among other features, the presence of neuritic plaques composed of amyloid beta-peptide (A beta) and the loss of basal forebrain cholinergic neurons, which innervate the hippocampus and the cortex. Studies of the pathological changes that characterize AD and several other lines of evidence indicate that A beta accumulation in vivo may initiate and/or contribute to the process of neurodegeneration and thereby the development of AD. However, the mechanisms by which A beta peptide influences/causes degeneration of the basal forebrain cholinergic neurons and/or the cognitive impairment characteristic of AD remain obscure. Using in vitro slice preparations, we have recently reported that A beta-related peptides, under acute conditions, potently inhibit K+-evoked endogenous acetylcholine (ACh) release from hippocampus and cortex but not from striatum. In the present study, we have further characterized A beta-mediated inhibition of ACh release and also measured the effects of these peptides on choline acetyltransferase (ChAT) activity and high-affinity choline uptake (HACU) in hippocampal, cortical, and striatal regions of the rat brain. A beta(1-40) (10(-8) M) potently inhibited veratridine-evoked endogenous ACh release from rat hippocampal slices and also decreased the K+-evoked release potentiated by the nitric oxide-generating agent, sodium nitroprusside (SNP). It is interesting that the endogenous cyclic GMP level induced by SNP was found to be unaltered in the presence of A beta(1-40). The activity of the enzyme ChAT was not altered by A beta peptides in hippocampus, cortex, or striatum. HACU was reduced significantly by various A beta peptides (10(-14) to 10(-6) M) in hippocampal and cortical synaptosomes. However, the uptake of choline by striatal synaptosomes was altered only at high concentration of A beta (10(-6) M). Taken together, these results indicate that A beta peptides, under acute conditions, can decrease endogenous ACh release and the uptake of choline but exhibit no effect on ChAT activity. In addition, the evidence that A beta peptides target primarily the hippocampus and cortex provides a potential mechanistic framework suggesting that the preferential vulnerability of basal forebrain cholinergic neurons and their projections in AD could relate, at least in part, to their sensitivity to A beta peptides.

Bradycardia produced by pyridostigmine and physostigmine

PURPOSE

The bradycardia produced by pyridostigmine and physostigmine in an animal model of acute cardiac denervation was examined according to its relation to cholinesterase inhibition and sensitivity to block by cholinergic receptor antagonists.

METHODS

Cats were anaesthetised, vagotomised and propranolol-treated. Heart rate was continuously recorded. Erythrocyte cholinesterase activity of arterial blood was measured using a radiometric technique. Nicotinic and muscarinic M1 receptors were blocked with hexamethonium and pirenzepine, respectively. M2 receptors were blocked with gallamine, pancuronium and AFDX-116.

RESULTS

With pyridostigmine and physostigmine the dose-response relationship for the decrease in heart rate (ED50 1.05 +/- 0.25 and 0.198 +/- 0.03 mg.kg-1, respectively) was shifted to the right of that for the inhibition of cholinesterase activity (ED50 0.094 +/- 0.03 and 0.032 +/- 0.01 mg.kg-1, respectively). The decrease in cholinesterase activity reached a plateau at a cumulative dose of 0.56 +/- 0.08 and 0.32 +/- 0.08 mg.kg-1, respectively. In contrast, there did not appear to be a plateau in the bradycardic effect. The bradycardia produced by pyridostigmine and physostigmine was blocked by hexamethonium (ED50 10 +/- 1.3 and 15.3 +/- 2.4 mg.kg-1, respectively), pirenzepine (ED50 68 +/- 16 and 138 +/- 32 micrograms.kg-1, respectively), gallamine (56 +/- 11 and 67 +/- 17 micrograms.kg-1, respectively), pancuronium (32 +/- 10 and 30 +/- 4 micrograms.kg-1, respectively), and AFDX-116 (31 +/- 4 and 28 +/- 4 micrograms.kg-1, respectively).

CONCLUSION

The bradycardia produced by reversible anticholinesterase drugs containing a carbamyl group is not clearly related to the degree of cholinesterase activity, and has a low sensitivity to nicotinic and muscarinic M1 and a high sensitivity to muscarinic M2 receptor antagonists.