Effect of mechanical ventilation on microvascular perfusion in critical care patients

PURPOSE

Microvascular perfusion, pivotal for adequate tissue oxygenation is potentially linked to outcome in critical care therapy. Mechanical ventilation (MV) and positive end-expiratory pressure (PEEP) as standard concepts of respiratory management are known to have deleterious effects on regional organ perfusion especially in the splanchnic area. As these effects have been attributed to different physiologic mechanisms, the purpose of this study was to investigate the effect of positive pressure ventilation on extra-abdominal tissue perfusion in non-surgical intensive care patients.

METHODS

Sublingual microcirculation was evaluated in 46 severely ill patients (group 1: n=26 requiring MV and PEEP; group 2: n=20 spontaneous breathing) admitted to the intensive care unit using sidestream darkfield intravitalmicroscopy. According to current guidelines, sublingual vessels were categorized by means of size and flow in semi-quantitative categories determining microvascular flow index (MFI). Total microvascular flow index (TMFI) was calculated for each patient as mean value of flow in all vessel categories.

RESULTS

No significant difference was observed between both groups in microvascular flow index in each vessel category and in total microvascular flow index. Patients requiring mechanical ventilation presented with more comorbidities and higher acuity of illness scores resulting in a higher ICU mortality, which however was not accompanied by microcirculatory differences at the time of measurement.

CONCLUSION

Mechanical ventilation and PEEP have no general deleterious effects on microvascular perfusion of the sublingual mucosa. However, further clinical studies are required to investigate potential effects of higher levels of ventilation pressure or PEEP on microvascular perfusion.

Microcirculation in cardiogenic shock: from scientific bystander to therapy target

Despite diagnostic and therapeutic improvements, mortality rates in patients with cardiogenic shock remain relatively high. Several studies showed that cardiogenic shock is associated with alterations in the microvascular circulation. These alterations may be reversed by extracorporeal support devices. A study by Munsterman and colleagues adds to the body of evidence showing that in patients deemed ready for discontinuing intra-aortic balloon pump (IABP) support, microcirculatory flow in small vessels increases after ceasing IABP therapy. This study not only highlights the need for optimal timing of weaning from IABP support but also supports recent findings that global hemodynamics do not necessarily result in changes of microvascular perfusion. All modalities of modern treatment in cardiogenic shock need to be evaluated for their effect on the microcirculation. Microcirculatory evaluations should be part of randomized controlled trial protocols. More effort is needed to improve outcomes and understand the microcirculation as a therapy target and not as a silent bystander.

The Occlutech Figulla PFO and ASD occluder: a new nitinol wire mesh device for closure of atrial septal defects

BACKGROUND

We investigated the safety, feasibility and efficacy of the Occlutech devices for patent foramen ovale (PFO) and atrial septal defect (ASD) closure in a prospective trial.

METHODS

The retention discs of the PFO device (23 x 25 mm, 27 x 30 mm) are connected by a 3 mm waist in the center with only one right atrial side central pin. The left atrial disc is produced either with a single or double flat layer, which allows a significant reduction of meshwork material. The ASD occluder (6-40 mm, 3 mm increments) has only one central pin on the right atrial side. Indications for closure included cryptogenic stroke with evidence of a PFO on transesophageal echocardiography (TEE) or an ASD II. The devices were implanted in 29 patients with PFO and in 12 patients with ASD II (fluoroscopy and TEE). An echocardiographic follow-up examination was performed after 1, 2 and 6 months.

RESULTS

The devices were successfully implanted in all 41 patients. There were no periprocedural complications. One patient with ASD II died of recurrent myocardial infarction without evidence of cardioembolic origin. TEE studies showed a residual shunt in 11.2% after 60 days in patients with PFO and a left-to-right shunt in 9.1% of the remaining patients with ASD II. After 180 days only 1 patient with PFO had a right-to-left shunt (3.7%). A residual shunt in the patients with ASD was not observed.

CONCLUSIONS

The novel Occlutech devices appear to be safe, feasible and effective for PFO and ASD closure, with a significant reduction of the meshwork and absence of left atrial central pin.

Effect of intra-aortic balloon pump support on microcirculation during high-risk percutaneous intervention

Background: Intra-aortic balloon counter-pulsation (IABP) is recommended for hemodynamic support in cardiogenic shock. In addition, it can be applied during high-risk percutaneous interventions (PCI). While IABP support improves microflow in cardiogenic shock, its effect in hemodynamically stable patients is still unclear. We, therefore, sought to evaluate the effect of IABP treatment on microflow in hemodynamically stable patients undergoing elective high-risk PCI. Methods: In six patients with >" xbd="892" xhg="869" ybd="1310" yhg="1284"/>50% left main stenosis, microflow was evaluated according to current guidelines, using side-stream dark-field microscopy, visualizing microcirculatory vessels without using fluorescent dyes. Microflow was analyzed separately for each vessel category (diameter: 10-25µm and 26-50µm), using a semiquantitative system (0= no flow; 1= intermittent flow; 2= sluggish flow; 3= continuous flow) by a trained investigator. Steady state recordings and additional recordings twenty seconds after discontinuation of the electively implanted IABP were acquired. Results: Microflow in vessel categories 10-25µm and 26-50µm increased in this group of hemodynamically stable patients on use of IABP. Microflow decreased from 2.73±0.39 (p=0.052; 26-50µm: 2.88±0.20, p=0.008) to 2.22±0.23 (2.18±0.45) after stopping the IABP and increased to 2.90±0.14 (p=0.009; 2.85±0.28, p=0.009) after restart of the IABP. Conclusions: Circulatory support with IABP increases microcirculatory flow in the smallest vessels of the sublingual mucosa. Our data support the hypothesis that intra-aortic balloon counter-pulsation increases coronary and microvascular perfusion, thus, improving microcirculation even in hemodynamically stable patients. The use of IABP may increase safety of complex PCI and decrease the risk of deleterious complications.

In Vivo Evaluation of Tissue Microflow under Combined Therapy with Extracorporeal Life Support and Intra-aortic Balloon Counterpulsation

Treatment with, percutaneous extracorporeal mechanical assist devices provides the ultimate therapeutic option to improve the macrocirculation in patients suffering from refractory cardiac arrest, severe cardiogenic shock or during high-risk interventions. However, the flow in the smallest vessels in these critical periods is poorly understood but prognostically of high importance. Using sidestream darkfield intravitalmicroscopy, we visualised the sublingual microflow in a patient suffering from severe cardiogenic shock supported by extracorporeal membrane oxygenation and intra-aortic balloon pump. Our results show that intra-aortic balloon counterpulsation applied in addition to extracorporeal membrane oxygenation further improves the microflow. This in vivo finding supports pilot studies favouring the application of devices supporting cardiac output (extracorporeal membrane oxygenation) together with devices aimed at pulsatility (intra-aortic balloon pump).

Postocardiotomy failure after Ross operation: implantation of intravascular flow pump through pulmonary autograft

We report a case of a patient with severe aortic stenosis, who underwent replacement of the aortic valve as a Ross procedure. Postoperatively the patient suffered postcardiotomy failure. Despite prolonged reperfusion and other methods of circulatory support, the patient could not be weaned from cardiopulmonary bypass (CPB). Therefore, an Impella intravascular flow pump was implanted, which is technically easy and has good weaning attributes. For implantation, a vascular prosthesis was sewn to the ascending aorta and the microaxial flow pump was placed under echocardiographic guidance across the pulmonary autograft into the left ventricle. With this support, the patient could be weaned from CPB. The report evaluates the Impella microaxial hemopump as a device that is technically easy to implant with no injury to the pulmonary autograft in patients after Ross operation. Surgeons should consider the device as a short-term support in borderline indications.

Anatomy of Spinal Cord Blood Supply in the Pig

BACKGROUND

In a species as popular in research as the pig, little information is available concerning the blood supply and vascular anatomy of the spinal cord and comparability to humans.

METHODS

To visualize vessels contributing to the blood supply of the spinal cord, x-ray digital subtraction angiography and vascular casting by injection of a polymerizing solution of methylmethacrylate were used.

RESULTS

The pig has larger internal thoracic arteries and subscapular arteries than the human, providing extensive collateral flow to the lower body, which offers blood supply to the spinal cord through the collaterals. The pig has a fine-caliber vessel plexus providing blood to the neck area, from which flow will reach both the spinal cord and the base of the brain. The segmental thoracic and lumbar arteries are relatively small in pigs, and they almost all originate as a single branch from the aorta and divide after 3 to 4 mm. The segmental vessels show a clear diminution after 2 to 3 cm at the level of the vertebral bodies. Pigs show major differences in the anatomy of the aortic bifurcation compared with humans. The median sacral artery in pigs is a large-caliber vessel, of a size almost comparable to the common iliac artery, with an isolated single dorsal branch leading to the spinal cord.

CONCLUSIONS

Documenting the anatomic differences in spinal cord blood supply between pigs and humans will aid in the planning of future experimental studies and in determining the clinical relevance of such studies.

Myocardial Failure Caused by Traumatic Dissection of Left Coronary System?Ventricular Recovery with Temporary Circulatory Support

We report a case of a patient suffering from massive myocardial infarction after traumatic dissection of the left coronary system. The dissection involved the left coronary artery including peripheral segments of the coronary circulation. The patient was revascularized; however, she could not be weaned from cardiopulmonary bypass thereafter. An Impella microaxial hemopump was implanted and the patient's left ventricular function markedly improved during the following days. Eight days later hemodynamics had stabilized far enough to explant the device, after explantation the patient remained hemodynamically stable and free of inotropic support. The report intends to emphasize the potential of the myocardium to recover even after extensive infarction under temporary ventricular support and takes the Impella microaxial hemopump into consideration as a device that is technically easy to implant with no injury to the ventricle and thus associated with good properties for weaning. Surgeons should consider the device as short-term support in borderline indications.

The Jena universal perfusion system: a universal cardiopulmonary bypass circuit for cardiac surgery

Cardiopulmonary bypass (CPB) is a standard technique in cardiac surgery, which itself contributes to postoperative morbidity. Neurologic sequelae after CPB is caused by air embolism or systemic inflammatory response due to artificial surface and is closely related to the characteristics of the extracorporeal circuit. Minimized systems without a venous reservoir take these factors into account. They require a differentiated volume management to avoid excessive negative pressure in the venous line, which may lead to spontaneous formation of microbubbles and are said to cause air embolism. Perfusion technology also offers systems with closed soft-bag and open hard-shell reservoirs, that require individual setups with little flexibility. We developed an all-purpose perfusion system for application as cardiopulmonary bypass. The central part is a compound reservoir, consisting of a lower hard shell and an upper self-expanding shell, which is capable of actively increasing volume. It allows application of the circuit as closed or open system. Crossclamping the inflow turns the system into a minimized circuit, in which the reservoir compensates volume when backflow is low and safeguards against excessive subzero pressure. The system has been applied in pilot experiments. In cardiac surgery today patients present at higher ages and with complex comorbidities. Not all of them are suitable candidates for off-pump procedures and might profit from perfusion technology with reduced adverse effects. The Jena Universal Perfusion System (JUPS) may be applied as a minimized system with the option to compensate low venous backflow and allows flexible extension to a closed or open circuit anytime during the procedure.

Does malperfusion syndrome affect early and mid-term outcome in patients suffering from acute type A aortic dissection?

It is well known that malperfusion syndrome (MPS) increases early mortality of patients suffering from acute type A aortic dissection (AADA). The aim of the present study was to analyze the outcome of patients who survived after surgical treatment of AADA with or without MPS. Data of 227 consecutive patients, who underwent surgery for AADA, were analyzed. The impact of MPS on in-hospital data and outcome was analyzed. Quality of life (QoL), using the short form 36 health survey questionnaire (SF-36), and late mortality were analyzed. Seventy-five patients (33%) with AADA had preoperative MPS. In 31 patients (41.3%), central nervous system (CNS) was involved and in 33 patients (44%) MPS of the extremities was present. Coronary malperfusion was found in 9 patients, renal in 8 patients and visceral malperfusion in 5 patients. Mean age in the group with MPS was 61.9+/-9.1 compared to 61.6+/-12.7 years without MPS (P=ns). In-hospital mortality was 18.7% in patients with MPS, compared to 9.9% without MPS (P<0.05). Follow-up revealed a significant poorer outcome in patients with MPS, with a 3-year-survival of 73.3% in patients with MPS and 86.2% without MPS (P<0.05). Average SF-36 values were lower in patients with MPS (78.3+/-12.8 vs. 87.8+/-11.9; P=ns), which is mainly due to patients with CNS-MPS, who showed an average SF-36 of 65.8+/-17.9 (P<0.05). AADA associated to MPS carries a higher early- and mid-term mortality. Postoperative mid-term QoL, however, except in patients with CNS-MPS and persistent neurological deficits, is fairly good and similar to patients who underwent successful surgery for AADA without MPS.

Optimal temperature for selective cerebral perfusion

OBJECTIVE

Although combinations of hypothermic circulatory arrest and antegrade selective cerebral perfusion are used for cerebral protection during arch surgery, there is no consensus regarding the optimal temperature during selective cerebral perfusion. This study explored the effect of different temperatures during selective cerebral perfusion on cerebral metabolism and neurologic outcome.

METHODS

In this blinded study, 40 pigs (19-21 kg) were randomized into 4 groups after 30 minutes of hypothermic circulatory arrest at 20 degrees C. During a 60-minute interval of selective cerebral perfusion, with flow regulated to maintain a perfusion pressure of 50 mm Hg, pigs were perfused at 10 degrees C, 15 degrees C, 20 degrees C, and 25 degrees C. Fluorescent microspheres enabled calculation of cerebral blood flow during perfusion and recovery. Hemodynamics, intracranial pressure, cerebrovascular resistance, and oxygen consumption were also monitored. Behavioral scores were obtained for 7 days after surgery.

RESULTS

Cerebral blood flow decreased significantly ( P < .002) during cooling in all groups: it was significantly higher throughout selective cerebral perfusion in the 20 degrees C to 25 degrees C versus the 10 degrees C to 15 degrees C group ( P = .0001) and remained higher during recovery ( P = .0001). Oxygen consumption decreased significantly with cooling ( P = .0001), remained low during perfusion, and rebounded with rewarming but was significantly lower at 10 degrees C to 15 degrees C than at 20 degrees C to 25 degrees C throughout selective cerebral perfusion ( P = .003) and after CPB was discontinued ( P = .001). Postoperative behavioral scores were significantly better after selective cerebral perfusion at 10 degrees C to 15 degrees C than at 20 degrees C to 25 degrees C ( P = .001).

CONCLUSIONS

This study suggests that selective cerebral perfusion at 10 degrees C to 15 degrees C provides better cerebral protection than selective cerebral perfusion at 20 degrees C to 25 degrees C, even though oxygen consumption remains low for hours after selective cerebral perfusion at 10 degrees C to 15 degrees C. Prompt return of metabolism to baseline levels after hypothermic circulatory arrest/selective cerebral perfusion does not necessarily predict superior behavioral outcome.

Axillary artery cannulation: routine use in ascending aorta and aortic arch replacement

BACKGROUND

Ideal perfusion during ascending aorta-arch surgery should allow easy implementation of antegrade cerebral perfusion while avoiding atheroembolization or false lumen perfusion in dissections. We report favorable experience with direct axillary artery cannulation.

METHODS

Between 1999 and 2003, 284 patients with a mean age of 62.2 years (25 to 85), underwent axillary artery cannulation using a right angle wire-reinforced catheter. During this interval, attempted axillary cannulation was abandoned in only 14 patients because of inadequate backflow or other complications. Eighty-five patients were female. Severe aortic arteriosclerosis or degeneration was present in 209, aortic dissection in 63, and Marfan disease or aortitis in 12. The Bentall procedure was done in 144 patients, arch replacement in 86, the Yacoub procedure in 18, thoracoabdominal aneurysm repair in 16, and coronary artery bypass grafting in 20. Reoperations were at 30.2%.

RESULTS

Adverse outcome (hospital death or permanent stroke) occurred in 6.6% (n = 19). Thirteen patients (4.6%) died before hospital discharge, and 13 patients (4.6%; 9 of whom died) suffered permanent stroke. Transient neurologic dysfunction occurred in 9.2% (n = 26). Mean duration of hypothermic circulatory arrest, used in 246 patients, was 26 +/-7 minutes. Mean duration of antegrade cerebral perfusion, used in 139 patients, was 47 +/- 23 minutes. In 93%, the right axillary artery was cannulated. Complications included 2 cases (0.7%) of brachial plexus injury (one transient), and 3 (1%) of localized dissection.

CONCLUSIONS

Our results suggest that axillary artery cannulation, successful in 95% of patients, may be the optimal technique for reducing perfusion-related morbidity and adverse outcome in operations for acute dissection, atherosclerotic, and degenerative aneurysmal disease. It deserves serious consideration in all patients older than 65 requiring cardiopulmonary bypass.

Mild hypothermia protects the spinal cord from ischemic injury in a chronic porcine model☆

OBJECTIVES

During thoracoabdominal aortic aneurysm repair, prolonged compromise of spinal cord blood supply can result in irreversible spinal cord injury. This study investigated the impact of mild hypothermia during aortic cross-clamping on postoperative paraplegia in a chronic porcine model.

METHODS

The thoracic aorta was exposed and cross-clamped in 30 juvenile pigs (20-22 kg) for different intervals at normothermia (36.5 degrees C), and during mild hypothermia (32.0 degrees C). Three pigs were evaluated at each time and temperature. Myogenic motor-evoked potentials (MEPs) were monitored, and postoperative recovery evaluated using a modified Tarlov score.

RESULTS

There were no significant hemodynamic or metabolic differences between individual animals, and the groups had equivalent arterial pressures (mean 64.3+/-3.6 mmHg). Time to recovery of MEPs correlated with severity of injury; all animals with irreversible MEP loss suffered postoperative paraplegia. At normothermia, animals with 20 min of aortic cross-clamping emerged with normal motor function, but those cross-clamped for 30 min suffered paraplegia. With mild hypothermia, animals tolerated 50 min of aortic cross-clamping without evidence of neurologic injury, but were all paraplegic after 70 min of ischemia. Animals appeared to recover normal motor function after 60 min of aortic cross-clamping at hypothermia initially, but exhibited delayed-onset paraplegia 36 h postoperatively.

CONCLUSIONS

Our observations indicate that mild hypothermia dramatically increases the tolerance of the spinal cord to ischemia in the pig, and therefore suggests that cooling to 32.0 degrees C should be encouraged during surgery which may compromise spinal cord blood supply. An ischemic insult of borderline severity may result in delayed paraplegia.

Technical advances in total aortic arch replacement

BACKGROUND

We compared the effects of using hypothermic circulatory arrest (HCA) alone, HCA combined with selective cerebral perfusion (SCP), and use of SCP with a trifurcated graft (T) on outcome after aortic arch repair.

METHODS

One hundred fifty patients, median age 66 years (range, 27 to 85), underwent total arch replacement between 1988 and 2002; 75 were female. We retrospectively compared the results of three patient groups roughly comparable with regard to preoperative risk factors: 45 patients using HCA beginning in 1988; 67 patients using HCA/SCP beginning in 1994; and 38 patients utilizing a trifurcated arch graft in conjunction with SCP through the axillary artery (HCA/SCP/T) since 2000. The groups were well matched with regard to median age (66, 68, and 66 years), urgency (emergent 11%, 13%, 5%; urgent 24%, 9%, 18%; and elective 64%, 78%, 76%), and several other known risk factors (p = not significant).

RESULTS

An adverse outcome-hospital death or permanent stroke-occurred in 14%: in 16% with HCA, in 16% with HCA/SCP, and in 8% with HCA/SCP/T. Transient neurologic dysfunction among patients surviving without stroke was lower with HCA/SCP/T (11%) than with HCA (33%) or HCA/SCP (17%). Mean duration of HCA was 52 +/- 16 minutes with HCA alone versus 45 +/- 10 minutes with HCA/SCP and 31 +/- 7 minutes with HCA/SCP/T (p < 0.0001 for groups HCA and HCA/SCP combined versus HCA/SCP/T). Mean duration of SCP was 57 +/- 25 minutes with HCA/SCP versus 62 +/- 24 minutes with HCA/SCP/T (p = not significant). Comparison of the groups of patients who had comparable preoperative risk factors for adverse outcome showed a trend toward lower adverse outcome and transient neurologic dysfunction rates using HCA/SCP/T; a significant reduction in respiratory (p < 0.001), infectious (p = 0.015) and cardiac (p = 0.005) complications in HCA/SCP/T compared with the earlier groups; and significantly shorter durations of intensive care (p < 0.0001) and hospitalization (p = 0.004).

CONCLUSIONS

Our results suggest that HCA/SCP is superior to HCA alone for preventing cerebral injury during operations on the aortic arch. By further reducing embolic risk as well as duration of HCA, HCA/SCP/T with axillary artery cannulation may be the optimal technique for averting adverse outcomes, reducing complications, and shortening hospital stay after aortic arch repair.

Cerebral physiology and outcome after hypothermic circulatory arrest followed by selective cerebral perfusion

BACKGROUND

This study explored the impact of an interval of hypothermic circulatory arrest (HCA) preceding selective cerebral perfusion (SCP) on cerebral physiology and outcome. This protocol allows use of SCP during aortic surgery without the threat of embolization inherent in balloon catheterization of often severely atherosclerotic cerebral vessels.

METHODS

In this blinded study, 30 pigs (20 to 22 kg) were randomized after cooling to 20 degrees C. Pigs in the HCA-CPB group (n = 10) underwent 30 minutes of HCA followed by 60 minutes of total body perfusion (CPB); HCA-SCP pigs (n = 10) underwent 30 minutes of HCA followed by 60 minutes of SCP, and SCP pigs (n = 10) had 90 minutes of SCP without prior HCA. Fluorescent microspheres enabled calculation of cerebral blood flow during perfusion and recovery. Hemodynamics, intracranial pressure, cerebrovascular resistance, and cerebral oxygen consumption were also monitored. Daily behavioral scores were obtained for 7 days postoperatively.

RESULTS

In all groups, cerebral oxygen consumption fell significantly with cooling (p < 0.0001), remained low during perfusion, and rebounded promptly with rewarming; cerebral oxygen consumption was significantly (p = 0.027) greater during SCP than during HCA-CPB. Cerebral blood flow was significantly higher throughout SCP in the HCA-SCP group (p < 0.0001) than with CPB. Cerebrovascular resistance during SCP and HCA-SCP was significantly lower (p = 0.036) than during CPB. Behavioral scores were significantly better with SCP than with HCA-CPB throughout recovery, but did not differ between SCP and HCA-SCP.

CONCLUSIONS

This study suggests that a short period of HCA preceding SCP provides global cerebral protection comparable to continuous SCP, implying that in clinical practice, a short period of HCA to reduce risk of embolization will not compromise the superior cerebral protection provided by SCP.

Importance of extrasegmental vessels for spinal cord blood supply in a chronic porcine model

OBJECTIVE

Our purpose was to investigate the interaction of the important components of spinal cord blood supply in the pig model to enable its use for future studies of spinal cord protection.

METHODS

Twenty-five juvenile pigs (20-22 kg) underwent serial intercostal (IC) or lumbar artery (LA) ligation until disappearance of motor evoked potentials (MEPs). Pigs underwent sequential craniocaudal IC/LA ligation alone (n=5); following clamping of both subclavian arteries (n=4), or clamping of the median sacral artery (MSA, n=4). Animals also underwent serial caudocranial clamping of LA/IC alone (n=4); preceded by clamping of the subclavian arteries (n=4), or of the MSA (n=4). Results were verified by Tarlov's scores and perioperative angiography.

RESULTS

All animals with MEP loss suffered postoperative paraplegia. Groups were equivalent with regard to stable arterial pressures (64.6+/-3.1 degrees C) throughout the experiment, temperature (36+/-1.1 degrees C) and other physiological parameters. Mean number of clamped IC/LA before MEP loss for cranio-caudal clamping direction was 12.8+/-0.8 for segmental arteries isolated, 9+/-0.8 if both subclavian arteries were ligated previously and only 4.3+/-0.5 IC if the median sacral artery was clamped before. Mean number of clamped LA for caudo-cranial clamping direction was 5.8+/-0.9 for segmental lumbar arteries, 5.5+/-0.6 LA if both subclavian arteries were ligated previously and 3.5+/-0.6 if the median sacral artery was clamped before.

CONCLUSION

This study confirms the importance of lumbar and MSA arteries to cord viability. It documents the interaction of the subclavian and MSA (roughly equivalent to the hypogastric arteries in humans) with segmental vessels in providing spinal cord blood supply. It also provides the physiologic basis for use of the pig model for studies of spinal cord protection in aortic surgery.

Importance of extrasegmental vessels for spinal cord blood supply in a chronic porcine model

IObjective: Our purpose was to investigate the interaction of the important components of spinal cord blood supply in the pig model to enable its use for future studies of spinal cord protection.

METHODS

25 juvenile pigs (20-22 Kg) underwent serial intercostal (IC) or lumbar artery (LA) ligation until disappearance of motor evoked potentials (MEPs). Pigs underwent sequential craniocaudal (IC/LA ligation alone (n=5); following clamping of both subclavian arteries (n=4)m, or clamping of the median sacral artery (MSA, n=4); preceded by clamping of the subclavian arteries (n=4), or of the MSA (n=4). RESULTS were verified by Tarlov's scores and perioperative angiography.

RESULTS

All animals with MEP loss suffered postoperative paraplegia. Groups were equivalent with regard to stable arterial pressures throughout the experiment, temperature and other physiological parameters. Mean number of clamped IC/LA before MEP loss for cranio-caudal clamping direction was 12.8 +/-0.8 for segmental arteries isolated, 9 +/-0.8 if both subclavian arteries were ligated previously and only 4.3 +/- 0.5 IC if the median sacral artery was clamped before. Mean number of clamped LA for caudo-cranial clamping direction was 5.8 +/-0.9 for segmental lumbar arteries, 5.5 +/-0.6 LA if both subclavian arteries were ligated previously and 3.5 +/-0.6 if the median sacral artery was clamped before.

CONCLUSION

This study confirms the importance of lumbar and MSA arteries to cord viability. It documents the interaction of the subclavian and MSA (roughly equivalent to the hypogastric arteries in humans) with segmental vessels in providing spinal cord blood supply. It also provides the physiologic basis for use of the pig model for studies of spinal cord protection in aortic surgery.

[Clinical and angiographic appearance of traumatic peripheral arteriovenous fistula]

Issuing from 33 patients with traumatic peripheral arteriovenous fistulas on the basis of an impressive case is reported on pathophysiological changes and it is referred to a possibly early operative correction of these peripheral arteriovenous shunt connections.

[Digoxin and sinus node function in the sick-sinus syndrome (author's transl)]

In 12 patients with sinus node syndrome, the influence of Digoxin on the sinus-node function was examined. After having determined the sinus-node recovery time (SNRT), the calculated sinuatrial conduction time (SACT), and the mean cycle length, 1.2 mg Digoxin were applied intravenously; 45 minutes later the above mentioned determinations were repeated. Before applying Digoxin, the mean value of the SNRT was 1665.8 +/- 1381.5 ms, after Digoxin it was 1372.1 +/- 546.1 ms; there was no statistical significance. In regard of the SACT the values were 95.9 +/- 38.6 ms before and 125.0 +/- 31.9 ms after Digoxin (p less than 0.05). The mean cycle length remained almost unchanged (841 +/- 113.2 ms before and 847 +/- 138.4 ms after Digoxin, no significance). Thus it is to be regarded as the clinical therapeutic consequence that in these patients the glycoside application in absence of syncopes or equivalents can be administered in most of the cases without previous pacemaker-implantation. In special cases, however, mainly if there are signs of greater disturbances of the sinus node function and of the SACT, electrophysical functional-analytic examination previous to the Digoxin long-term therapy should be performed.

[Simultaneous occurrence of arteriosclerosis obliterans and venous diseases]

It is reported on the pathophysiological peculiarities which may appear in the coincidence of the two vascular diseases. As therapy the fibrinolysis with Awelysin should always be taken into consideration.

[Complications during long-term control of the pressure in the pulmonary artery]

It is reported on two rare complications occurring in the pulmonary catheterisation with long-term control of the pressure of the pulmonary artery. In case 1 in confluenting bronchopneumonias the formation of an abscess in the region of the point of the catheter developed, in which case by the infusion therapy with very peripheral position of the catheter local lesions are very probable. In case 2 the catheter via an atrial septum defect passed into a pulmonary vein in PCA-position. A haemorrhagic infarction of the lung developed. In the two cases after removal of the catheter and adequate therapy the pulmonary complications healed.

[Premonitory sign of myocardial rupture]

It is reported on 14 cases in which a rupture of the myocardium occurred following a myocardial infarction. The moment of the appearance as well as anamnestic and clinical peculiarities are examined. As the only usable symptom of the rupture the symptomatology of the electromechanic dissociation must be taken into consideration. Finally it is referred to the on principle possible operative consequences of the rupture of the myocardium (oversewing or infarctetomy).