Horizontal flow and capillarity-driven redistribution in porous media.

A recent macroscopic mixture theory for two-phase immiscible displacement in porous media has introduced percolating and nonpercolating phases. Quasi-analytic solutions are computed and compared to the traditional theory. The solutions illustrate physical insights and effects due to spatiotemporal changes of nonpercolating phases, and they highlight the differences from traditional theory. Two initial and boundary value problems are solved in one spatial dimension. In the first problem a fluid is displaced by another fluid in a horizontal homogeneous porous medium. The displacing fluid is injected with a flow rate that keeps the saturation constant at the injection point. In the second problem a horizontal homogeneous porous medium is considered which is divided into two subdomains with different but constant initial saturations. Capillary forces lead to a redistribution of the fluids. Errors in the literature are reported and corrected.

[Cesarean section with continuous spinal anesthesia in a cardiopulmonary high-risk patient]. / Sectio caesarea in Katheter-Spinalanästhesie bei einer kardiopulmonalen Hochrisikopatientin.

UNLABELLED: As a consequence of the progress in (perinatal) medicine the number of pregnant women with severe cardiopulmonal risk, who need caesarean delivery, is rising. The anaesthetic care of these patients requires optimal preparation and--as a prerequisite--constant intraoperative vital functions (heart rate, blood pressure, oxygen saturation). Typical risks like airway-problems, hypoxia, hyper- and hypotension and tachycardia must be strictly avoided. We report a case of successful caesarean delivery in a patient with severe coronary heart disease, using spinal catheter technique. CASE REPORT: The patient was a 36-year-old woman with a symptomatic coronary heart disease. Risk factors were hypercholesterinaemia, obesity (105 kg/168 cm), COPD consecutive to excessive nicotine abuse and hypertonia. Emergency admissions in the 12th and 14th gestation week led to the necessity of PTCA in the 15th and 19th gestation week in spite of pregnancy: coronary stenoses of 90% and 70% were dilated. Caesarean section was scheduled for 38 weeks' gestation, however due to the high risk involved we decided to use a continuous spinal technique. There were no problems with introducing the catheter (28 gauge, L3-4 interspace). Under careful titration a total of 2.2 ml plain bupivacaine 0.5% (spinal catheter) and 0.5 mg alfentanil (intravenously) were administered. This produced anaesthesia up to T8 without any respiratory or cardiovascular embarrassment. A healthy male infant (Apgar score 9/10/10) was delivered. Postoperative analgesia was provided by intrathecal injections of bupivacaine and intravenous injections of piritramide. There were no intraoperative or postoperative problems. DISCUSSION: By means of continuous spinal anaesthesia for caesarean section it is possible to avoid typical complications of general anaesthesia (hypoxia, airway management, aspiration, tachycardia), of single-shot spinal anaesthesia (hypotension, low or high block) and of epidural anaesthesia (high dose of local anaesthetics, danger of accidental intrathecal or intravenous injection). The possibility of postoperative analgesia is advantageous. Technical difficulties, postspinal headache and the high costs of the sets may be disadvantageous. CONCLUSION: This case demonstrates, that the use of a continuous spinal catheter technique for caesarean section anaesthesia is an alternative method, which should be considered especially in high risk patients, when meticulous care for constant vital functions is requested urgently.