High-dose thiopentone for open-chamber cardiac surgery: a retrospective review.

PURPOSE: High-dose thiopentone has been reported to reduce the incidence of neurological dysfunction after open-chamber cardiac surgery. However, this technique delays tracheal extubation and increases requirements for inotropic support after cardiopulmonary bypass. As a quality assurance measure to determine the safety of high-dose thiopentone, we reviewed the records of all patients undergoing elective, open-chamber surgery at our institution between 1st March, 1987 and 31st Dec, 1989. METHODS: The charts of 236 patients were reviewed retrospectively, and 227 met our inclusion criteria. The perioperative characteristics of patients anaesthetized with thiopentone (Group T, n = 80) were compared with those of patients anaesthetized with opioids (Group O, n = 147). RESULTS: Anaesthetic technique was chosen by the attending anaesthetist. in Group T (n = 80) thiopentone 38.1 +/- 11.8 mg.kg-1 was infused to produce electroencephalographic burst-suppression during bypass. Moderate hypothermia and arterial line filtration were used during bypass. The groups did not differ with respect to demographics, type of surgery, or conduct of bypass. There were no strokes in Group T and 4 in Group O (P = NS). The time to extubation was prolonged in Group T compared with Group O (39 +/- 51 vs 27 +/- 24 h, P = 0.014), as was the duration of stay in intensive care (66 +/- 56 vs 51 +/- 29 h, P = 0.010). Thiopentone did not increase the need for inotropic or mechanical support after bypass. In-hospital mortality was lower in Group T than in Group O (1.2% vs 9.5%, P = 0.034). CONCLUSION: High-dose thiopentone delays extubation after open-chamber procedures. However, the technique appears safe, and further prospective investigation is justifiable.

Comparison of sedative recovery time after midazolam versus diazepam administration.

OBJECTIVE: To compare the sedative recovery rate pharmacology of intravenous midazolam vs. diazepam when used for short-term sedation. DATA SOURCES: English-language articles were identified through a search of the MEDLINE and InPharma databases. Bibliographies of retrieved articles were examined for relevant articles. STUDY SELECTION: Twenty-eight studies were identified based on a priori inclusion criteria. Eight trials had enough information to combine results for sedative recovery rate. DATA EXTRACTION: The difference in mean time to sedative recovery, weighted by sample size, was determined. DATA SYNTHESIS: Of the 28 trials, eight reported a significantly faster sedation recovery rate from diazepam vs. midazolam, whereas 19 trials reported no difference in sedative recovery time, and a single trial reported that midazolam offered significantly faster recovery from sedation than diazepam. A commonly defined time to sedative recovery event was available for only eight trials. The median dosing ratio for these eight trials was 2.1:1 for diazepam over midazolam. The weighted mean time difference was 4 mins 16 secs in favor of diazepam as the agent from which patients recover more quickly. CONCLUSIONS: These results firmly underscore the understanding that elimination half-lives of benzodiazepines do not necessarily correspond with their sedative pharmacodynamic effects, and we conclude that there are no clinically important sedative recovery rate differences between midazolam and diazepam, while midazolam is a more expensive agent.

Lack of in vitro inactivation of tobramycin by imipenem/cilastatin.

OBJECTIVE: Inactivation of aminoglycosides by beta-lactam antimicrobials both in vitro and in vivo has been documented. Such an interaction has not previously been documented between carbapenems and aminoglycosides. Examination of serum concentrations of tobramycin in a patient receiving both agents suggested that this interaction might exist. The purpose of this study was to look at this question in an in vitro model. METHODS: Low concentrations of tobramycin (10 micrograms/mL) were incubated with imipenem/cilastatin (concentrations of 10, 20, and 40 micrograms/mL) in human serum at 37 degrees C. Aliquots of these solutions were withdrawn at 0, 6, 24, 72, and 120 hours and assayed for tobramycin concentrations using a fluorescence polarization immunoassay. Aliquots of tobramycin 10 micrograms/mL and carbenicillin 200 micrograms/mL were analyzed in the same manner, as a positive control. High concentrations of tobramycin (800 micrograms/mL) and imipenem (5000 micrograms/mL)/cilastatin were incubated together at 21 degrees C and sampled at 0, 6, 24, and 72 hours for tobramycin concentrations. RESULTS: The degradation rates for low-concentration tobramycin and the various concentrations of imipenem/cilastatin were not statistically different from those of the controlled incubations. In contrast, carbenicillin significantly enhanced the degradation rate of tobramycin at this concentration (half-life 72 hours and a 34 percent loss at 24 hours, p = 0.0028). Higher in vitro concentrations of imipenem (5000 micrograms/mL)/cilastatin and tobramycin (800 micrograms/mL) resulted in significant, but moderate degradation over controlled incubations (half-life 80 hours and 10 percent loss at 12 hours, p = 0.0031). CONCLUSIONS: These results suggest that inactivation of tobramycin is not a problem at common clinically achievable imipenem serum concentrations in patients.

Hemodynamic and temperature changes after aortocoronary bypass grafting.

Perioperative hemodynamic and temperature changes were reviewed in 58 patients who underwent aortocoronary bypass grafting. Core temperature showed an immediate decline postoperatively, secondary to core temperature cooling during bypass. Subsequent rewarming occurred over the next 8 to 12 hours, with the temperature often increasing above normal. The reason for this pyrexial response is discussed. The cardiac index was depressed immediately postoperatively, again with substantial recovery within 8 hours. This improvement over time occurred not only because of recovery of intrinsic function but also because of reduction in myocardial work due to falling systemic vascular resistance. The latter was high immediately postoperatively and then consistently fell during the rewarming phase. During the first 8 hours postoperatively there were significant changes in temperature and cardiac and systemic vascular resistance indices. The hemodynamic data correlated strongly with changes in temperature. Falling systemic vascular resistance required the institution of alpha-agonist therapy in 25% of patients.

Long-term multi-dimensional outcome following isolated traumatic brain injuries and traumatic brain injuries associated with multiple trauma.

We retrospectively investigated long-term, multi-dimensional quality-of-life outcomes in 68 male patients who suffered pure head injuries and 63 male head-injured patients with associated multiple trauma. Results indicated that patients sustaining associated multiple trauma were significantly younger and more deeply comatose on admission. Trends were found to suggest that patients sustaining associated multiple trauma also remain in coma longer, and experience more difficulties in social interaction and overall psychosocial functioning, but less difficulties in mobility compared with pure-head-injured patients. These findings should be taken into account in the evaluation of results of treatment as well as in the planning and allocation of resources for head-injured patients.

Early metabolic and neurologic predictors of long-term quality of life after closed head injury.

Research has begun to identify early markers that predict survival after traumatic brain injury. In this study, trauma and biochemical indicators of severity were used to predict quality of life in 61 adults with traumatic brain injury and no damage to other organ systems. Severity markers available within 24 hours of injury were predictive of later psychosocial, behavioural and social role functioning. Multiple regression analyses demonstrated that the Glasgow Coma Scale, plasma glucose levels, leukocyte cell count and serum potassium concentration accounted for 12% to 66% of variance in certain measures of later quality of life. The importance of health-care resource allocation and psychosocial and behavioural intervention to the outcome after moderate traumatic brain injury is discussed.

Early determinants of outcome in blunt injury.

A critical set of 135 patients and a validation set of 202 patients who sustained blunt injury were examined for indices of outcome based on blood chemistry and the Glasgow coma scale. In both sets the nonsurvivors had significantly lower scores on the coma scale, higher levels of plasma glucose and increased leukocyte counts. Hypokalemia was also noted and a trend towards lower serum levels with increasing injury severity. Logistic discriminant analysis demonstrated that the most important variables were the coma scale score (as a continuous variable from 3 to 14) and the plasma glucose level (as a dichotomized variable with normal being defined as less than 10 mmol/L [i.e., the renal threshold] and abnormal as being above this level). A coma scale score cut-off at 10 with an abnormal plasma glucose level, and a cut-off at 8 with a normal plasma glucose level produced a maximum correct classification rate (into survivals and deaths) of 87%. Lower scores were associated with an increasing probability of death. Serum potassium levels and the leukocyte count did not contribute significantly to the discriminant function, although both were related to outcome. The reasons for the detected abnormalities are discussed. Metabolic markers, such as plasma glucose and serum potassium, in association with the coma scale score are simple and early determinants of outcome in blunt injury and may be useful indices of injury severity.

Cholecystectomy with and without drainage.

The authors studied the effect of intraoperative drainage, presence of postoperative pyrexia, influence of appendectomy, chest complications and wound infection in 200 patients who had undergone routine uncomplicated cholecystectomy. One hundred patients in whom no drain was inserted were matched with 100 patients whose cholecystectomies, performed during the same period, included placement of a drain. There were 10 males and 90 females in each group; the mean age was 40.5 years in the undrained group and 40.4 years in the drained group. There was a significantly (P less than 0.05) higher frequency of chest complications, longer hospital stay and pronounced postoperative pyrexia (P less than 0.003) in the group with drainage. The rate of wound infection was substantially increased in both groups by adding appendectomy to the procedure, particularly if drains were not used. It is evident that the routine placement of a drain in an uncomplicated cholecystectomy is unnecessary and may even be harmful.