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Biomedical subjects

M A Schepens

Publications and source records attributed to M A Schepens.

At least 37 records · Page 2Linked to original sources
PubMed1999

Antegrade selective cerebral perfusion in operations on the proximal thoracic aorta.

BACKGROUND: To determine the factors that influence hospital death and neurologic complications after surgery on the thoracic aorta using circulatory arrest and antegrade selective cerebral perfusion. METHODS: From May 1989 through April 1997, 106 patients underwent surgery on the thoracic aorta using circulatory arrest and antegrade selective cerebral perfusion. Mean age was 64.0 +/- 11.5 years. Unilateral antegrade cerebral perfusion was used in 37 patients (35%), bihemispheric antegrade cerebral perfusion in 69 patients (65%). Mean antegrade cerebral perfusion time was 50.5 +/- 20.5 minutes. Indication for surgery was atherosclerotic aneurysm in 60 (56.5%) patients, postdissection aneurysm in 26 (24.4%), acute type A dissection in 16 (15.1%), other in 4 (4.0%). RESULTS: Hospital mortality was 8.5% (n = 9; 70% CL: 5.8%-11.2%). Independent predictors of hospital mortality were rethoracotomy (odds ratio 5.7, p = 0.02), postoperative temporary (odds ratio 17.3, p = 0.02) or permanent (odds ratio 7.5, p = 0.03) neurologic dysfunction, postoperative dialysis (odds ratio 9.9, p = 0.008). Bilateral antegrade selective cerebral perfusion had a favorable impact on hospital mortality (odds ratio 0.08, p = 0.007). Temporary neurologic dysfunction occurred in 3.8% of patients (n = 4; 70% CL: 2.0%-5.6%); preoperative hemodynamic instability (odds ratio 14.8, p = 0.05) and perioperative technical problems (odds ratio 22.2, p = 0.033) were independent determinants of temporary neurologic dysfunction. Permanent central neurologic damage occurred in 5.4% of patients (n = 6; 70% CL: 3.2%-7.6%). Preoperative hemodynamic instability (odds ratio 18.9, p = 0.009) and approach through a left thoracotomy (odds ratio 9.4, p = 0.031) were significant predictors of permanent neurologic damage. CONCLUSIONS: Hospital mortality is affected significantly by the choice of technique used for antegrade cerebral perfusion. The incidence of both temporary and permanent postoperative central neurologic damage is influenced by preoperative hemodynamic instability. Duration of cerebral perfusion had no influence on the postoperative neurologic outcome.

Acute Disease↗
PubMed1999

Aortic root replacement with the pulmonary autograft: an invariably competent aortic valve?

BACKGROUND: Pulmonary autograft aortic root replacement was used in adults. Risk factors for aortic regurgitation (AR), and for pulmonary allograft valve stenosis are identified. METHODS: From February 1991 through April 1998, 80 adults (mean age 34.4 years) underwent pulmonary autograft aortic root replacement. Primary diagnosis was AR in 43 (53.7%) patients, aortic stenosis in 13 (16.3%) and mixed disease in 24 (30%) patients. A root reinforcement ring was used in 32 (40%) patients. RESULTS: There was no hospital mortality. Estimated patient survival is 100% at 7 years. A total of 3 patients underwent reoperation: 2 on the autograft for severe AR, 1 for pulmonary allograft stenosis. Freedom from reoperation on the autograft is 96.7 +/- 2.4% at 7 years. Multivariate analysis indicated bicuspid aortic valve disease as an incremental risk factor for AR at discharge (p = 0.036, odds 3.5). Univariate analysis identified operation for pure AR as risk factor for AR during follow-up (p = 0.041). Mild AR or more increased from 2.5% at discharge to 11.3% during follow-up (p = 0.008). Progression of AR was limited by the use of a reinforcement root ring (p = 0.031). Freedom from mild AR or more in patients with and without a reinforcement root ring was 100% and 72.9 +/- 9.3% respectively, at 5 years (p = 0.119). Pulmonary allograft stenosis occurred in 15 (22.5%) patients. Multivariate analysis revealed that large sized pulmonary allografts were less prone to stenosis (p = 0.048, odds 0.13). CONCLUSIONS: Pulmonary autograft root replacement can be performed with few complications. During follow-up, a significant increase in mild AR or more is observed. The use of a reinforcement root ring is effective in preventing progression of AR.

Adolescent↗
PubMed1999

Reoperations on the ascending aorta and aortic root: pitfalls and results in 134 patients.

BACKGROUND: This analysis was performed to evaluate the results of reoperations on the ascending aorta and aortic root. METHODS: All reoperations (n = 134) on the aortic root and ascending aorta performed between February 1981 and April 1998 were retrospectively analyzed. Indications for reintervention were a true or false aneurysm (35%), acute dissection (3.0%), aortic valve stenosis and/or insufficiency (23.1%), prosthetic valve endocarditis (32.8%), and combinations (4.5%). The principal reoperations performed were aortic root replacement (composite graft, freestyle, aortic allograft, or pulmonary autograft) in 116 patients, ascending aortic replacement in 10 patients, and closure of a false aneurysm in 5 patients. Results were analyzed using univariate statistical methods. RESULTS: Hospital mortality was 6.6% (8 patients). Univariate predictors of hospital death were preoperative functional class III or IV (p = 0.02), an interval of less than 6 months between the primary and actual operation (p = 0.02), preoperative creatinine level of more than 200 micromol/L (p = 0.001), acute aortic dissection (p = 0.001), intraoperative technical problems (p = 0.001), and postoperative dialysis (p = 0.001). Freedom from repetitive reoperation was 99% at 1 year and 98% at 5 and 10 years. CONCLUSIONS: Reoperations on the aortic root and ascending aorta can be performed with an early mortality which is very acceptable.

Adult↗
PubMed1999

The relationship between evoked potentials and measurements of S-100 protein in cerebrospinal fluid during and after thoracoabdominal aortic aneurysm surgery.

OBJECTIVE: This study was performed to correlate the changes in concentration of S-100 protein in the cerebrospinal fluid (CSF) during and after thoracoabdominal aortic aneurysm (TAAA) surgery with the results of somatosensory and motor evoked potential monitoring. METHODS: The study was designed as a prospective study at St Antonius Hospital in Nieuwegein, The Netherlands. The participants were 19 patients who were undergoing elective TAAA surgery. CSF samples for analysis of S-100 protein were drawn after the induction of anesthesia, during the cross-clamp period of the critical aortic segment, after 5 minutes of reperfusion of this segment, during the closure of the skin, and 24 hours after the closure of the skin. In all the patients, continuous intraoperative recording of myogenic motor potentials evoked by transcranial electrical stimulation (tcMEP) and somatosensory potentials evoked by stimulation of the posterior tibial nerve took place to monitor the integrity of the spinal cord. The operative technique consisted of staged or sequential clamping to maximize the beneficial effect of the distal perfusion by the left heart bypass, continuous CSF drainage to keep the CSF pressure below 10 mm Hg, and moderate hypothermia (32 degrees C rectal temperature). We correlated the measured concentrations of S-100 protein in CSF with the results of evoked potential monitoring during surgery and the number of intercostals reimplanted and oversewn. RESULTS: In all the patients, the concentration of S-100 protein was increased in CSF. The highest concentration of S-100 protein was found in the CSF sample taken 5 minutes after reperfusion of the critical aortic segment. There was a good (negative) correlation between the changes in S-100 protein in CSF and the changes in motor evoked potential monitoring during the cross-clamp period. The best (negative) correlation was detected between the S-100 protein elevation in the CSF sample drawn 5 minutes after reperfusion and the tcMEP amplitude reduction during clamping (r = -0.73; P =.007). No relation was found between the S-100 protein dynamics in CSF and somatosensory evoked potential monitoring. A positive (r = 0.58; P =.05) correlation was found between the change in tcMEP amplitude during clamping and the number of reattached intercostals. A moderate to good (r = -0.5 to -0.7; P <.05) correlation between the number of reattached intercostals and the changes in S-100 protein concentration in CSF during TAAA surgery was found. Our data show that transient elevations in S-100 protein after cross clamping are larger in those patients with marked decrease in tcMEP from baseline during the cross-clamp period. CONCLUSION: A correlation is shown between an increasing concentration of S-100 protein in CSF and a reduction in tcMEP amplitude during cross clamping of the aorta. The S-100 protein in CSF seems to be a marker of potential clinical value in the evaluation of the effects of procedures to detect and reduce spinal cord ischemia.

Adult↗
PubMed1999

Twenty-four year experience with reoperations after ascending aortic or aortic root replacement.

OBJECTIVE: A retrospective analysis of early and late outcome for late (>4 weeks) reoperations on the ascending aorta or aortic root. MATERIALS AND METHODS: During a 24-year interval, starting in 1974, 834 patients underwent replacement of the ascending aorta (39.2%) or aortic root (60.8%). During the same period, 56 patients with a mean age of 51.1 +/- 14.4 years underwent reoperation after ascending aortic or aortic root replacement. Predominant indications for reoperation were false aneurysm in 25 (44.6%) patients and true aneurysm in 18 (32.1%) patients. Most frequent surgical procedures were redo aortic root replacement in 30 (53.6%) patients and closure of a false aneurysm in 14 (25.0%) patients. Median interval between the operations was 51 months. Eighteen (32.2%) patients underwent concomitant partial or total aortic arch replacement. RESULTS: Hospital mortality was 5.4% (n = 3; 70% CL: 2.4-8.4%). Cause of death was low cardiac output in two patients and rupture of the aorta at the distal suture line in one patient. Univariate analysis identified two or more previous operations (P = 0.038) and the interval between initial operation and reoperation for complication of less than 8 months (P = 0.005) as risk factors for hospital death. Multivariate analysis indicated operation for active endocarditis or vascular graft infection as an independent risk factor for hospital death (P = 0.038, odds 14.6). Follow-up was complete, median 3.1 years. Nine (16.9%; 70% CL: 11.7-22.1%) patients died during that period. Estimated survival at 1, 5 and 10 years was 91.2, 84.0 and 76.4%. One patient underwent another reoperation. Estimated event-free survival at 1, 5 and 10 year is 84.3, 72.2 and 65.6%. CONCLUSION: False aneurysm formation and progression of aneurysmatic disease are the predominant causes for late reoperations after aortic root or ascending aortic replacement. Reoperations can be performed with low hospital mortality and good late results.

Adult↗
PubMed1999

The influence of nitrous oxide to supplement fentanyl/low-dose propofol anesthesia on transcranial myogenic motor-evoked potentials during thoracic aortic surgery.

OBJECTIVE: Intraoperative monitoring of myogenic motor evoked potentials to transcranial electrical stimulation (tc MEPs) is a new method to assess the integrity of the motor pathways. The authors studied the effects of 50% nitrous oxide (N2O) and a low-dose propofol infusion on tc MEPs paired electrical stimulation during fentanyl anesthesia with partial neuromuscular blockade. DESIGN: Cross-over study. SETTING: St Antonius Hospital, Nieuwegein, The Netherlands. PARTICIPANTS: Ten patients scheduled to undergo surgery on the thoracoabdominal aorta were studied; 6 women aged 54 to 69 years and 4 men aged 68 to 77 years. INTERVENTIONS: After achieving a stable anesthetic state and before surgery, tc MEPs were recorded during four 15-minute periods: (I) air/oxygen (O2; F(I)O2 = 50%); propofol target blood concentration, 0.5 microg/mL; (II) N2O/O2 (F(I)O2 = 50%); propofol target blood concentration, 0.5 microg/mL; (III) N2O/O2 (F(I)O2 = 50%; propofol target blood concentration, 1.0 microg/mL; and (IV) air/O2 (F(I)O2 = 50%); propofol target blood concentration, 1.0 microg/mL. MEASUREMENTS AND MAIN RESULTS: Tc MEPs were recorded from the right extensor digitorum communis muscle and the right tibialis anterior muscle. The right thenar muscle was used for recording the level of relaxation; the T1 response was maintained at 40% to 70% of the control compound muscle action potential. There was no significant difference in onset latency among the four phases. The addition of N2O and doubling the target propofol infusion to 1.0 microg/mL resulted in a 40% to 50% reduction of tc MEP amplitude recorded in the extensor digitorum communis muscle and tibialis anterior muscle (p < 0.01). During each phase, tc MEPs could be elicited and interpreted, except in one patient, in whom no tc MEPs could be elicited in the leg because of technical problems. CONCLUSION: The data indicate that tc MEP monitoring is feasible during low-dose propofol, fentanyl/50% N2O in 02 anesthesia and partial neuromuscular blockade.

Action Potentials↗
PubMed1999

Within patient variability of lower extremity muscle responses to transcranial electrical stimulation with pulse trains in aortic surgery.

Intraoperative recording of myogenic motor responses evoked by transcranial electrical stimulation is a method of controlling the integrity of the motor pathways during clamping of the aorta. It is important to know the within patient variability of the transcranial motor evoked potential (tcMEP), before changes within the variability range are interpreted as abnormal during the period of aortic cross clamping. Lower limb muscle responses were obtained in 11 patients, following transcranial electrical stimulation with pulse trains, of 4, 6 and 8 pulses. Under the conditions of partial neuromuscular blockade and a stable low dose propofol/fentanyl/nitrous oxide anaesthetic state, this study shows that multipulse transcranial electrical stimulation reliably produces muscle responses of the lower limb in all patients tested with a coefficient of variation (CV) of around 20%. Eight pulses in the stimulation train produce neurophysiological facilitation that exceeds a 4 pulse train in terms of area under the curve (AUC) and response duration. The use of multipulse stimulation rather than double or single pulse stimulation is recommended in order to increase the clinical efficacy of tcMEP monitoring in aortic surgery.

Adult↗
PubMed1999

Effect of nitrous oxide on myogenic motor potentials evoked by a six pulse train of transcranial electrical stimuli: a possible monitor for aortic surgery.

Intraoperative recording of myogenic motor potentials evoked by transcranial electrical stimulation (tcMEP) is a method of monitoring the integrity of the vulnerable motor pathways during thoracoabdominal aortic aneurysm (TAAA) surgery. Deflation of the left lung during TAAA surgery may result in impairment of arterial oxygenation. Ventilation with nitrous oxide may cause further desaturation. We studied the effects of 20%, 40% and 60% nitrous oxide in oxygen on within-patient variability and magnitude of tcMEP in response to six pulse transcranial electrical stimulation during fentanyl-low-dose propofol anaesthesia with partial neuromuscular block. Ten patients (two females; aged 63-74 yr) were studied. After achieving a stable anaesthetic state and before surgery, 10 tcMEP were recorded from the right tibialis anterior muscle during addition of 20%, 40% and 60% nitrous oxide in oxygen in random order. When ventilation with 40% or 60% nitrous oxide in oxygen was performed, there was 50-70% depression of tcMEP amplitude (P < 0.05) and 40-60% reduction in tcMEP area under the curve (P < 0.05) compared with 20% nitrous oxide in oxygen. There was no significant difference in the coefficients of variation for tcMEP between the three nitrous oxide anaesthetic regimens. Our results suggest that increasing doses of nitrous oxide reduce the MEP waveform to six pulse transcranial electrical stimulation, but even with 60% nitrous oxide in oxygen, the tcMEP were recordable and as reproducible as with 20% and 40% nitrous oxide regimens. The method is sufficiently robust for use in aortic surgery.

Aged↗
PubMed1999

Within-patient variability of myogenic motor-evoked potentials to multipulse transcranial electrical stimulation during two levels of partial neuromuscular blockade in aortic surgery.

UNLABELLED: Intraoperative recording of myogenic motor responses evoked by transcranial electrical stimulation (tcMEPs) is a method of assessing the integrity of the motor pathways during aortic surgery. To identify conditions for optimal spinal cord monitoring, we investigated the effects of manipulating the level of neuromuscular blockade (T1 response of the train-of-four (TOF) stimulation 5%-15% versus T1 response 45%-55% of baseline), as well as the number of transcranial pulses (two versus six stimuli) on the within-patient variability and amplitude of tcMEPs. Ten patients (30-76 yr) scheduled to undergo surgery on the thoracic and thoracoabdominal aorta were studied. After achieving a stable anesthetic state and before surgery, 10 tcMEPs were recorded from the right extensor digitorum communis muscle and the right tibialis anterior muscle in response to two-pulse and six-pulse transcranial electrical stimulation with an interstimulus interval of 2 ms during two levels of neuromuscular blockade. The right thenar eminence was used for recording the level of relaxation. The tcMEP amplitude using the six-pulse paradigm was larger (P < 0.01; leg and arm) compared with the amplitude evoked by two-pulse stimulation during both levels of relaxation. The within-patient variability, expressed as median coefficient of variation, was less when six-pulse stimulation was used. At a T1 response of 45%-55% of baseline, larger, less variable tcMEPs were recorded than at a T1 response of 5%-15%. Our results suggest that the best quality of tcMEP signals (tibialis anterior muscle) is obtained when the six-pulse paradigm is used with a stable level of muscle relaxation (the first twitch of the TOF-thenar eminence-at 45%-55% of baseline). IMPLICATIONS: This study shows that six-pulse (rather than two-pulse) transcranial electrical stimulation during a stable anesthetic state and a stable neuromuscular blockade aimed at 45%-55% (rather than 5%-15%) of baseline provides reliable and recordable muscle responses sufficiently robust for spinal cord monitoring in aortic surgery.

Anesthesia, General↗
PubMed1998

Normal serum concentrations of S-100 protein and changes in cerebrospinal fluid concentrations of S-100 protein during and after thoracoabdominal aortic aneurysm surgery: Is S-100 protein a biochemical marker of clinical value in detecting spinal cord ischemia?

PURPOSE: This study was performed to determine the concentration of S-100 protein in serum and in the cerebrospinal fluid (CSF) during and 24 hours after thoracoabdominal aortic aneurysm repair. METHODS: This prospective study was performed at St. Antonius Hospital in Nieuwegein, The Netherlands. Eight patients who underwent elective thoracoabdominal aortic surgery participated in the study. Arterial blood and CSF samples for analysis of S-100 protein were drawn after induction of anesthesia, during the cross-clamp period of the critical segment, after 5 minutes of reperfusion, during the closure of the skin, and 24 hours after closure of the skin. RESULTS: No increase in S-100 protein concentration could be detected in serum (< 0.2 microg/L). The S-100 protein concentration in CSF increased during the procedure in all patients (4.2 +/- 3.1 microg/L). However, in one patient, who became paraplegic, the S-100 protein concentration in CSF increased even further after 24 hours (10 microg/L). CONCLUSIONS: The preliminary results suggest that S-100 protein in CSF may be a marker of clinical value in evaluating the effects of measures to detect and reduce spinal cord ischemia.

Aortic Aneurysm, Abdominal↗
PubMed1998

Extended vertical transatrial septal approach for the removal of left atrial myxoma.

OBJECTIVE: Optimal exposure greatly facilitates left atrial myxomectomy and is mandatory for safe and efficacious tumour removal. The purpose of this study was to evaluate one institutions experience, with an alternative to the classical approach, for the removal of left atrial myxoma. METHODS: In an eight-year period, eight patients underwent surgical removal of left atrial myxoma at our institution using the extended vertical transatrial septal approach, slightly modified compared to the original method of Guiraudon and associates, as the septum was initially incised superiorly instead of through the fossa ovalis. RESULTS: One patient with poor left ventricular function died shortly after the surgical procedure because of low cardiac output. Postoperative course of the other patients was uneventful. No rethoracotomy for bleeding was carried out and no permanent arrhythmias were seen. There was one late death at 4.5 months after operation, for which no clear reason was found. Mean follow-up was 55 months (range 1 to 79 months) and revealed six asymptomatic healthy patients. CONCLUSIONS: We feel that the extended vertical transatrial septal approach provides good exposure of left atrial tumours and facilitates complete surgical removal without inherent complications such as tumour cell dissemination or fragmentation.

Aged↗
PubMed1997

Acute aortic dissection complicating pregnancy.

BACKGROUND: Acute aortic dissection occurring during pregnancy represents a lethal risk to both the mother and fetus. Our purpose was to study the prevalence, treatments, and outcome of this rare problem and to suggest therapeutic guidelines. METHODS: During the past 12 years, 6 pregnant women were admitted with an acute aortic dissection. Four had a type A and 2 had a type B dissection (Stanford classification). RESULTS: Two of the 4 patients with a type A dissection underwent a combined emergency operation consisting of first cesarean section and then ascending aortic repair. Cesarean section was carried out 5 days after the emergency procedure on the aorta in the third patient, and 16 weeks later in the fourth patient. All 4 fetuses were delivered alive. One fetus died 6 days later, but the other 3 are alive and well at long-term follow-up. Of the 2 patients with a type B dissection, 1 was operated on for celiac ischemia; the other was treated medically. In both cases the fetus died in utero. There were no maternal deaths in either group. CONCLUSIONS: Cesarean section with concomitant aortic repair is recommended for pregnant women with a type A dissection, depending on the gestational age. The maternal hemodynamic status will determine the sequence of the two procedures. Medical treatment is advised for patients with a type B dissection, but surgical repair is indicated if complications such as bleeding or malperfusion of major side branches occur.

Acute Disease↗
PubMed1997

Spontaneous resolution late after aortic dissection.

A 50-year-old man was operated on for acute type I (DeBakey classification) aortic dissection. The supracoronary ascending aorta was replaced with an interposition graft. Postoperative computed tomography and angiography clearly revealed a double-barrelled aortic arch, left common carotid artery and descending thoracoabdominal aorta with contrast filling of both true and false lumen starting from the distal anastomosis. The same finding was noted at 1 year follow-up with severe compression of the true lumen by the false lumen. At this time, anticoagulation therapy was stopped. One year later, computed tomography showed spontaneous resolution of the dissection in the aortic arch, left common carotid artery and descending aorta over its full length. This was confirmed by angiography. This case reports illustrates that spontaneous resolution of a dissected descending aorta can occur late after surgery from type 1 dissection, but it remains very rare.

Aortic Dissection↗
PubMed1996

Survival and aortic events after graft replacement for thoracoabdominal aortic aneurysm.

Graft replacement remains the procedure of choice for patients with thoracoabdominal aortic aneurysm. Since there is little information regarding the long-term survival following these major vascular operations which may carry a risk of various late complications, a retrospective analysis of 10 years follow-up was undertaken. The results of 172 consecutive operations for thoracoabdominal aortic aneurysm were analysed retrospectively. Hospital mortality rate was 10.5%. Temporary postoperative haemodialysis was necessary in 10.4% of cases and paraplegia occurred in 8.2%. The mean (s.e.) overall cumulative 2-, 5- and 10-year observed survival rate was 76(3.4), 53(4.5) and 19(7)%, respectively while expected survival of a background population at 2, 5 and 10 years was 94%, 85% and 71%, respectively. Reoperation for an early (< 7 days) or late (> 7 days) aortic event was necessary in 31 patients. If performed electively, the hospital mortality rate for late aortic reoperation was only 7% but an emergency reoperation, hospital mortality rate was 100%.

Aged↗
PubMed1996

Upper and lower extremity somatosensory evoked potential recording during surgery for aneurysms of the descending thoracic aorta.

Since tibial nerve somatosensory evoked potentials (SEPs) recording is influenced by hemodynamic changes and anesthetics, alterations cannot always be attributed to spinal cord ischemia, so causing false positive results. Additional recording of median nerve SEPs facilitates interpretation. From January 1988 to July 1993, 60 consecutive patients (44 men, 16 women, mean age 66 years, ranging from 26 to 83 years) underwent surgery for an aneurysm of the descending thoracic aorta using a non-heparinized left heart bypass (Biomedicus pump). In 40 patients recording of the tibial and median nerve SEPs was performed intraoperatively by stimulating both nerves alternately. In 32 patients (80%) both recordings were uneventful. In three patients (7.5%) the tibial nerve SEP temporarily disappeared due to peripheral ischemia on termination of the bypass for the creation of an open distal anastomosis. In three patients (7.5%) near loss of both tibial and median SEP recordings was caused by low blood pressure and/or anesthetics. In two patients (5%) isolated loss of the tibial nerve SEP was due to ischemia in the spinal pathway of the tibial nerve. The tibial nerve SEP signal returned to normal: in one patient after reperfusion of intercostal arteries localized within the aneurysm, in the other patient after drainage of cerebrospinal fluid (CSF). Continuous recording of both tibial and median nerve SEPs gives consistent information on spinal cord ischemia, reducing the false positive rate of the lower extremity SEP to 7.5%.

Adult↗