Biomedical subjects
Publications and source records attributed to D C Adams.
Anesthetic considerations for thoracic and thoracoscopic neurosurgical procedures are considered, emphasizing the need to provide anesthetic stability during prolonged periods of one-lung ventilation, while optimizing conditions for intraoperative monitoring of spinal cord integrity.
OBJECTIVES: Atrial fibrillation remains a significant source of morbidity after coronary artery bypass grafting (CABG). Whether cardiopulmonary bypass (CPB) temperature influences the occurrence of postoperative atrial fibrillation in CABG patients has not been specifically examined. In the present study, we reviewed postoperative data from patients who were prospectively randomized to mild or moderate hypothermic CPB for elective CABG to determine the incidence of postoperative atrial fibrillation. DESIGN: Randomized, single center, observational study. SETTING: Tertiary university medical center. PATIENTS: Adults undergoing elective CABG surgery. INTERVENTIONS: Enrolled patients were prospectively randomized to mild (34 degrees C [93.2 degrees F]) or moderate (28 degrees C [82.4 degrees F]) hypothermic CPB. MEASUREMENTS AND MAIN RESULTS: The incidence of postoperative atrial fibrillation was determined by review of ICU and hospital records. There was a significantly higher incidence of atrial fibrillation in the moderate compared with the mild hypothermic CPB group. Patients who had postoperative atrial fibrillation were significantly older than those without atrial fibrillation. Furthermore, a significant increase in the relative risk of developing postoperative atrial fibrillation was found for both age and CPB temperature. CONCLUSIONS: Our results indicate that the temperature of systemic cooling during CPB is an important factor in the development of atrial fibrillation after CABG surgery. In addition, this study confirms that increasing age is a significant determinant of postoperative atrial fibrillation.
OBJECTIVE: Although fixed dosage of heparin is frequently used during vascular surgery, there are very few studies that document the appropriateness of this type of dosing. We have undertaken a prospective study to determine the physiological response to a fixed dose of heparin, using a conventional measure of anticoagulation, and have correlated this measure with complications. METHODS: We studied 140 consecutive patients undergoing elective carotid endarterectomy. Serial activated clotting times (ACT values) were obtained in duplicate before administration of heparin, 15 minutes after application of a carotid artery cross-clamp, and 1 hour after administration of 5000 U of heparin by intravenous bolus. Postoperatively, patients were assessed for new neurological deficits (transient ischemic attack and stroke) and neck hematomas. A battery of neuropsychometric tests was performed in 49 patients at baseline and on the day after carotid endarterectomy to identify subtle new neurological deficits. RESULTS: ACT values were found to be highly reproducible, with less than a 1.5% difference between duplicate baseline samples. Although all patients received 5000 U of heparin, the dose received per kilogram of body weight varied considerably (44-116 U/kg), as did ACT values at both 15 minutes (178-423 s) and 1 hour (173-390 s). Nevertheless, there was a significant correlation between heparin dose per kilogram and ACT values at 15 minutes (r = 0.45) and at 1 hour (r = 0.38) postinfusion, as well as ACT ratios (final ACT/initial ACT) at 15 minutes (r = 0.43) and at 1 hour (r = 0.34) after heparin bolus. Eight patients (5.7%) developed postoperative wound hematomas, one of which (0.7%) required reoperation. No patient had a stroke, but one patient had a transient ischemic attack, and 19 (39%) of 49 patients demonstrated significant early postoperative neuropsychometric deficits. Although the incidence of neck hematoma was not influenced by the heparin dose (P = 0.23), the ACT value at 15 minutes (P = 0.71) or 1 hour (P = 0.61), or the ACT ratio (P = 0.68), the only severe hematoma requiring reoperation occurred when the maximal ACT value was more than 400 seconds. Although performance on neuropsychometric tests did not appear to be statistically influenced by heparin dosing, the ACT value, or the degree of ACT elevation, there was a trend for deficits to be associated with lower heparin doses. CONCLUSION: Fixed heparin dosing achieves safe and efficacious anticoagulation in the great majority of patients having carotid endarterectomy, with 5000 U expected to result in 15-minute and 1-hour ACT values of 175 to 425 seconds and 170 to 390 seconds, respectively. Although weight-based heparin dosing may reduce the incidence of subtle complications (hematoma formation or decline on neuropsychometric tests) and may result in more predictable 15-minute and 1-hour ACT values (85 U/kg; 225-375 and 200-340 s, respectively), no statistically compelling clinical advantage could be demonstrated. Therefore, either weight-based or fixed dosing is acceptable, with both obviating the need for routine pre-clamp ACT confirmation, thereby saving operative time and expense.
The objective of this study was to determine whether a combination of Cu, Co, Mn, and Zn in an organic or inorganic form fed at higher than nutrient recommendations for 2-yr-old cows from calving to breeding would affect pregnancy rate, calving date, calf performance, and cow liver and serum mineral concentrations. Crossbred 2-yr-old cows were used after calving in 1994 (n = 127) and 1995 (n = 109). Cows were blocked by calving date to one of three treatments: 1) no supplemental minerals (CTL), 2) organic minerals (ORG), or 3) inorganic minerals (ING). Minerals were fed for the same daily intake for both organic and inorganic treatments: Cu (125 mg), Co (25 mg), Mn (200 mg), and Zn (360 mg). Cows were individually fed a mineral-protein supplement with grass hay from calving (February-March) to before breeding (May 15). Hay intakes were calculated using chromium oxide boluses to determine fecal output. Fecal excretion of minerals was calculated following trace element analysis of feces. Liver biopsies were obtained before calving, after calving (start of supplementation), at the end of supplementation, and in midsummer. Over 2 yr, more cows did not become pregnant (P < .01) in ORG (11/78) and ING (11/78) treatments than in CTL (0/80) treatments. A treatment x year interaction was found for day of conception. Cows in the ORG group conceived later (P < .01) than cows in the ING or CTL groups in 1994. In 1995, there was no difference (P > .10) in day of conception among groups. Liver Zn and Mn concentrations were not different (P > .10) and Cu concentrations increased (P < .01) for the ORG and ING groups. Cows in the ORG and ING groups had higher (P < .01) concentrations of Cu, Mn, and Zn in the feces than the CTL cows. Trace elements in the feces did not differ for ORG and ING groups. Results indicate that combinations of Cu, Co, Mn, and Zn fed at higher levels than are required reduced reproductive performance.
Advances in anesthetic and surgical management, such as induced deep hypothermic circulatory arrest and application of temporary clips, have improved outcome for patients with basilar artery aneurysms. Nonetheless, these techniques are associated with significant risks. The authors report a case in which three transient periods of cardiac asystole were induced during basilar artery aneurysm surgery. Adenosine-induced asystole facilitated the safe clipping of the aneurysm by producing consistent periods of profound hypotension and collapse of the aneurysm without the need for temporary clipping. This technique provided unencumbered identification of perforating arteries, precise definition of the local anatomy, and an ideal environment for the safe placement of the aneurysm clip.
BACKGROUND: Many anesthetic drugs have been shown to disrupt conscious recall (explicit memory) in volunteers. However, unconscious processing (implicit memory) of intraoperative auditory material may occur during general anesthesia and may provide an opportunity for intraoperative therapeutic intervention. In this study, we examined patients undergoing elective cardiac surgery for evidence of intraoperative implicit and explicit memory. METHODS AND RESULTS: Twenty-five subjects provided written informed consent and underwent general anesthesia and cardiopulmonary bypass for cardiac surgery. During the operation, patients were randomized to receive 1 of 2 different audiotapes of associated word pairs. Postoperatively, a blinded observer conducted a standardized interview to determine the extent of intraoperative implicit and explicit memory. With the use of free association, significant intraoperative implicit memory was found. In contrast, no patient had spontaneous or directed recall of intraoperative events, and we did not find evidence of intraoperative explicit memory with a recognition task. CONCLUSIONS: Patients undergoing general anesthesia for cardiac surgery were reliably able to reinforce associations between word pairs solely on the basis of their intraoperative presentation. This provides further evidence that patients are capable of processing intraoperative auditory information.
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BACKGROUND AND PURPOSE: One hundred twelve patients undergoing elective carotid endarterectomy for symptomatic and asymptomatic carotid artery stenosis were enrolled in a prospective study to evaluate the incidence of change in postoperative cerebral function. METHODS: Patients were evaluated preoperatively and postoperatively before hospital discharge and at follow-up 1 and 5 months later with a battery of neuropsychometric tests. The results were analyzed by both event-rate and group-rate analyses. For event-rate analysis, change was defined as either a decline or improvement in postoperative neuropsychometric performance by 25% or more compared with a preoperative baseline. RESULTS: Approximately 80% of patients showed decline in one or more test scores, and 60% had one or more improved test scores at the first follow-up examination. The percentage of declined test scores decreased and the percentage of improved test scores increased with subsequent follow-up examinations. Group-rate analysis was similar for group performance on individual tests. However, a decline in performance was seen most commonly on verbal memory tests, and improved performance was seen most commonly on executive and motor tests. CONCLUSIONS: Neuropsychometric evaluation of patients undergoing carotid endarterectomy for significant carotid artery stenosis demonstrates both declines and improvements in neuropsychometric performance. The test changes that showed decreased performance may be associated with ischemia from global hypoperfusion or embolic phenomena, and the improvement seen may be related to increased cerebral blood flow from removal of stenosis.
OBJECTIVE: Ninety-nine patients undergoing elective coronary artery bypass grafting were enrolled in a prospective, randomized study to evaluate the incidence of cerebral dysfunction after "mild" or "moderate" hypothermia during cardiopulmonary bypass. METHODS: Patients were evaluated before and after operation before hospital discharge and in some cases at follow-up at least 6 weeks later with a complete neurologic examination (85 patients) and a battery of standard neuropsychometric tests (86 patients). RESULTS: Postoperative changes detected by neurologic examination consisted of the appearance of new primitive reflexes in both groups. No statistically significant differences in incidence were found. The neuropsychometric performances of the two groups were statistically similar by either event-rate or group-rate analysis. CONCLUSIONS: There is no detectable difference in postoperative cerebral dysfunction in patients undergoing coronary artery bypass grafting who are supported by cardiopulmonary bypass with either mild or moderate hypothermia.
OBJECTIVE: To determine the sympathetic response during cardiopulmonary bypass at mild (34 degrees C) and moderate (28 degrees C) hypothermia. DESIGN: A randomized study. SETTING: Tertiary university hospital. PATIENTS: Adults undergoing elective coronary artery bypass graft surgery. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Plasma norepinephrine, epinephrine, and neuropeptide Y concentrations were measured. Moderate, but not mild, hypothermic cardiopulmonary bypass evoked a significant sympathetic response with increases in plasma norepinephrine and neuropeptide Y concentrations. A significantly higher incidence of postoperative atrial fibrillation was also observed in the moderate hypothermic compared with the mild hypothermic group. CONCLUSIONS: Our results indicate that the degree of hypothermia significantly influences the sympathetic response during cardiopulmonary bypass. The higher incidence of postoperative atrial fibrillation in the moderate hypothermic group suggests that the enhanced sympathetic response might be one contributing factor in the development of atrial fibrillation.
A study was conducted over 3 yr to evaluate effects of sire birth weight EPD, calf birth weight and shape, and heifer pelvic area and weight, individually and in combination, on dystocia and subsequent rebreeding of 2-yr-old heifers. Heifers (n = 550), MARC II yearlings, were assigned for breeding to one of four Angus sires with birth weight EPD of -.95, -82, +2.9, and +2.7 kg. At calving, heifers were assisted as needed. A gauge attached to the cal puller recorded applied traction pressure. Analysis of traction pressure detected only slightly larger amounts of variation (2 to 3%) affecting dystocia than the standard five-point scoring system. Dam weight did not affect calving difficulty score (CDS), except dam birth weights were heavier (P < .05) for CDS 5 (Caesarean section) than CDS 1 (unassisted). Dams requiring Caesarean section had smaller pelvic areas (P < .05), with no other differences among CDS. The CDS increased as calf birth weight and cal external measurements increased. Low EPD sires produced calves with smaller (P < .05) birth weights and smaller calf head and food circumferences and caused less dystocia than high EPD sires. The CDS did not affect subsequent pregnancy rates but did affect conception date of the second calf. Calves delivered by Caesarean section were lighter (P < .05) at weaning than other calves but had similar slaughter weights. As mean winter temperature increased (6.1 degrees C) from yr 1 to 3, calf birth weight decreased (4.6 kg) and calving difficulty decreased 23%. Results indicate sire birth weight EPD, calf birth weight and shape, dam pelvic area, and climate affected CDS, and CDS affected subsequent conception date.
Cerebral injury remains a significant complication of cardiac surgery. This complication is evaluated by clinical means that include a neurologic examination. In this report, the most important components of this type of evaluation are described. The neurologic complications of cardiac surgery can be determined by comparing structured preoperative and postoperative clinical evaluations. The neurologic examination must include a mental state examination, examination of cranial nerves, motor, sensory, and cerebellar systems, examination of gait and station, and deep tendon and primitive reflexes. The purpose of this report is to discuss the relevance of the neurologic examination in the assessment of cerebral injury after cardiac surgery, review the components of a structured neurologic examination, and explore the role of "quantitative" stroke scales as a research tool.
Previous studies have demonstrated the feasibility of continuously monitoring jugular venous oxygen saturation (SjO2) with a fiberoptic catheter during hypothermic cardiopulmonary bypass (CPB). In the present study, with patients maintained at either moderate (28 degrees C) or mild (32-34 degrees C) hypothermia during CPB, SjO2 values obtained from a fiberoptic catheter were compared to intermittent samples analyzed by a co-oximeter. Twenty patients scheduled for elective coronary artery or valvular surgery had a 5.5 Fr Opticath catheter inserted into the left internal jugular bulb after induction of general anesthesia. The catheter was calibrated in vitro and in vivo according to the manufacturer's specifications. Catheter and co-oximetry SjO2 values obtained at four time points--1) pre-CPB, 2) target CPB temperature, 3) mid-rewarming, and 4) post-CPB--were compared using linear regression, Bland-Altman analysis, and Shrout-Fleiss interclass correlation coefficient analysis. These statistical methods revealed poor correlation between the catheter and co-oximetry SjO2 values: r = 0.44 by linear regression and 0.32 by interclass correlation coefficient analysis, and was unacceptably discrepant by Bland-Altman analysis. Oxyhemoglobin saturation values obtained continuously from a jugular venous bulb fiberoptic catheter during CPB may not accurately reflect true oxyhemoglobin saturation, and caution is warranted when interpreting SjO2 values obtained from a fiberoptic catheter during CPB.
BACKGROUND: Although low-flow cardiopulmonary bypass (CPB) has become a preferred technique for the surgical repair of complex cardiac lesions in children, the relative hypotension and decrease in cerebral blood flow (CBF) associated with low flow may contribute to the occurrence of postoperative neurologic injury. Therefore, it was determined whether phenylephrine administered to increase arterial blood pressure during low-flow CPB increases CBF. METHODS: Cardiopulmonary bypass was initiated in seven baboons during fentanyl, midazolam, and isoflurane anesthesia. Animals were cooled at a pump flow rate of 2.5 l.min-1.m-2 until esophageal temperature decreased to 20 degrees C. Cardiopulmonary bypass flow was then reduced to 0.5 l.min-1.m-2 (low flow). During low-flow CPB, arterial partial pressure of carbon dioxide (Pco2) and blood pressure were varied in random sequence to three conditions: (1) Pco2 30-39 mmHg (uncorrected for temperature), control blood pressure; (2) Pco2 50-60 mmHg, control blood pressure; and (3) Pco2 30-39 mmHg, blood pressure raised to twice control by phenylephrine infusion. Thereafter, CPB flow was increased to 2.5 l.min-1.m-2, and baboons were rewarmed to normal temperature. Cerebral blood flow was measured by washout of intraarterial 133Xe before and during CPB. RESULTS: Phenylephrine administered to increase mean blood pressure from 23 +/- 3 to 46 +/- 3 mmHg during low-flow CPB increased CBF from 14 +/- 3 to 31 +/- 9 ml.min-1.100 g-1, P < 0.05. Changes in arterial Pco2 alone during low flow bypass produced no changes in CBF. CONCLUSIONS: Although low-flow CPB resulted in a marked decrease in CBF compared with prebypass and full-flow bypass, phenylephrine administered to double arterial pressure during low-flow bypass produced a proportional increase in CBF.
OBJECTIVE: Hypothermia has been demonstrated to protect the brain from ischemic or traumatic injury. Previous efforts to induce cerebral hypothermia have relied on techniques requiring total body cooling that have resulted in serious cardiovascular derangements. A technique to selectively cool the brain, without systemic hypothermia, may have applications for the treatment of neurological disease. METHODS: After induction of general anesthesia in 12 baboons, the right common carotid artery and ipsilateral femoral artery were each occlusively cannulated and joined to a centrifugal pump. In a closed-circuit system, blood was continually withdrawn from the femoral artery, cooled by water bath, and infused through the common carotid artery with its external branches occluded. Pump flow was varied so that right carotid pressure approximated systemic blood pressure. In six animals, perfusate was cooled to decrease right cerebral temperature to < 19 degrees C for 30 minutes. In six animals, right cerebral temperature was decreased to < 25 degrees C for 3 hours. In those six animals, 133Xe was injected into the right carotid artery before, during, and after hypothermia. Peak radioactivity and washout curves were recorded from bilateral cranial detectors. Systemic warming was accomplished by convective air and warm water blankets. Esophageal, rectal, and bilateral cerebral temperatures were continuously recorded. RESULTS: In animals cooled to < 19 degrees C, right cerebral temperature decreased from 34 degrees C to 18.5 +/- 1.1 degrees C (mean +/- standard deviation), P < 0.01, in 26 +/- 13 minutes. Simultaneously, left cerebral temperature decreased to 20.7 +/- 1.6 degrees C. During 30 minutes of stable cerebral hypothermia, esophageal temperature decreased from 35.1 +/- 2.3 degrees C to 34.2 +/- 2.2 degrees C, P < 0.05. In animals cooled to < 25 degrees C, right cerebral temperature decreased from 34 degrees C to 24.5 +/- 0.6 degrees C in 12.0 +/- 6.0 minutes, P < 0.01. Simultaneously, left cerebral temperature decreased to 26.3 +/- 4.8 degrees C. After 3 hours of stable cerebral hypothermia, esophageal temperature was 34.4 +/- 0.5 degrees C, P < 0.05. Right hemispheric cerebral blood flow decreased during hypothermia (26 +/- 16 ml/min/100 g) compared to values before and after hypothermia (63 +/- 29 and 51 +/- 34 ml/min/100 g, respectively; P < 0.05). Furthermore, hypothermic perfusion resulted in a proportionally increased radioactivity peak detected in the left cerebral hemisphere after right carotid artery injection of 133Xe (0.8 +/- 0.2:1, left:right) compared to normothermia before and after hypothermia (0.3 +/- 2 and 0.3 +/- 1, respectively; P < 0.05). Normal heart rhythm, systemic arterial blood pressure, and arterial blood gas values were preserved during hypothermia in all animals. CONCLUSION: Bilateral cerebral deep or moderate hypothermia can be induced by selective perfusion of a single internal carotid artery, with minimal systemic cooling and without cardiovascular instability. This global brain hypothermia results from profoundly altered collateral cerebral circulation during artificial hypothermic perfusion. This technique may have clinical applications for neurosurgery, stroke, or traumatic brain injury.
We reviewed the results of motor evoked potential (MEP) and somatosensory evoked potential (SEP) monitoring during 116 operations on the spine or spinal cord. We monitored MEPs by electrically stimulating the spinal cord and recording compound muscle action potentials from lower extremity muscles and monitored SEPs by stimulating posterior tibial or peroneal nerves and recording both cortical and subcortical evoked potentials. We maintained anesthesia with an N2O/O2/opioid technique supplemented with a halogenated inhalational agent and maintained partial neuromuscular blockade using a vecuronium infusion. Both MEPs and SEPs could be recorded in 99 cases (85%). Neither MEPs nor SEPs were recorded in eight patients, all of whom had preexisting severe myelopathies. Only SEPs could be recorded in two patients, and only MEPs were obtained in seven cases. Deterioration of evoked potentials occurred during nine operations (8%). In eight cases, both SEPs and MEPs deteriorated; in one case, only MEPs deteriorated. In four cases, the changes in the monitored signals led to major alterations in the surgery. We believe that optimal monitoring during spinal surgery requires recording both SEPs and MEPs. This provides independent verification of spinal cord integrity using two parallel but independent systems, and also allows detection of the occasional insults that selectively affect either motor or sensory systems.
A study was conducted to evaluate the effect of sire growth potential, steer age, and cow size on intake, growth, and production efficiency in grazing cattle. Data were collected on 24 cow-calf pairs during each of four summers (1989 to 1992) and on 12, 7-mo-old and 12 yearling steers during three summers (1990 to 1992). Suckling calves and older steers were sired by either high-(Charolais with high EPD for yearling weight) or moderate-growth-potential (Line 1 Hereford with average yearling weight ratios) bulls. Cow size was defined by principal component scores developed from cow weights, condition scores, and hip heights. Forage, but not milk, OM intake by suckling calves was influenced (P < .05) by sire growth potential. Yearling high-growth-potential steers tended to consume more OM than yearling moderate growth potential steers (P < .10) when expressed as kilograms/day but not when expressed as grams/kilogram BW (P > .10). Seven-month-old steers ate less (P < .01) forage (4.3 kg/d) than yearlings (5.6 kg/d) when expressed as kilograms/day but more (P < .01) when expressed as grams/kilogram BW (7-mo-old, 15.9 vs yearling, 14.4 g/kg BW). Cow OM intake was affected by cow size and milk production but not calf growth potential. Milk production but not cow size was a significant covariate for cow efficiency (grams of calf BW gain/kilogram of forage OM intake by cow-calf pair). Calf sire growth potential did not affect cow efficiency. We conclude that growth potential of sire for suckling calves and steers and cow size for cows affected intake of rangeland forage in summer but did not affect efficiency of production from Northern Great Plains rangelands.
Two grazing trials were conducted to determine the ruminally degradable protein requirement of gestating beef cows in the last half of pregnancy grazing winter native Sandhills range. In Trial 1, 80 crossbred cows (522 +/- 9 kg) were assigned randomly to one of the following ruminally degradable protein (RDP) treatments: 50%, 75%, 100%, or 125% of the estimated supplemental requirement. In Trial 2, 80 crossbred cows (529 +/- 8 kg) were assigned to 29%, 65%, 100%, or 139% of the estimated supplemental RDP requirement. In Trial 1, daily gain and condition score (CS) were not different (P > .15) among treatments. In Trial 2, gain responded quadratically, being higher (P = .14) for the 65% level than for the 29%, 100%, and 139% levels (.18, .05, .06, and .01 kg/d, respectively). Condition score was maintained at 65% and lost at 29%, 100%, and 139% (cubic effect, P = .06; 0, -.2, -.4, -.3, respectively). In both experiments, forage intake did not differ among treatments although OM digestibility increased linearly (P = .08) in Trial 1 with increasing level of RDP but not in Trial 2. Diet samples were collected in both experiments to estimate total nutrient intake. Forage RDP intake was 322 g/d in Trial 1 and 279 g/d in Trial 2. We conclude that gestating beef cows grazing native winter Sandhills range need between 62 and 140 g/d of supplemental RDP to meet their daily requirement of 340 to 430 g/d or 7.1% of the digestible OM.