J.Kenneth Davison

Clinical experience with epidural cooling for spinal cord protection during thoracic and thoracoabdominal aneurysm repair

PURPOSE This report summarizes our experience with epidural cooling (EC) to achieve regional spinal cord hypothermia and thereby decrease the risk of spinal cord ischemic injury during the course of descending thoracic aneurysm (TA) and thoracoabdominal aneurysm (TAA) repair. METHODS During the interval July 1993 to Dec. 1995, 70 patients underwent TA (n = 9, 13%) or TAA (n = 61) (type I, 24 [34%], type II, 11 [15%], type III, 26 [37%]) repair using the EC technique. The latter was accomplished by continuous infusion of normal saline (4 degrees C) into a T11-12 epidural catheter; an intrathecal catheter was placed at the L3-4 level for monitoring of cerebrospinal fluid temperature (CSFT) and pressure (CSFP). All operations (one exception, atriofemoral bypass) were performed with the clamp-and-sew technique, and 50% of patients had preservation of intercostal vessels at proximal or distal anastomoses (30%) or by separate inclusion button (20%). Neurologic outcome was compared with a published predictive model for the incidence of neurologic deficits after TAA repair and with a matched (Type IV excluded) consecutive, control group (n = 55) who underwent TAA repair in the period 1990 to 1993 before use of EC. RESULTS EC was successful in all patients, with a 1442 +/- 718 ml mean (range, 200 to 3500 ml) volume of infusate; CSFT was reduced to a mean of 24 degrees +/- 3 degrees C during aortic cross-clamping with maintenance of core temperature of 34 degrees +/- 0.8 +/- C. Mean CSFP increased from baseline values of 13 +/- 8 mm Hg to 31 +/- 6 mm Hg during cross-clamp. Seven patients (10%) died within 60 days of surgery, but all survived long enough for evaluation of neurologic deficits. The EC group and control group were well-matched with respect to mean age, incidence of acute presentations/aortic dissection/aneurysm rupture, TAA type distribution, and aortic cross-clamp times. Two lower extremity neurologic deficits (2.9%) were observed in the EC patients and 13 (23%) in the control group (p < 0.0001). Observed and predicted deficits in the EC patients were 2.9% and 20.0% (p = 0.001), and for the control group 23% and 17.8% (p = 0.48). In considering EC and control patients (n = 115), variables associated with postoperative neurologic deficit were prolonged (> 60 min) visceral aortic cross-clamp time (relative risk, 4.4; 95% CI, 1.2 to 16.5; p = 0.02) and lack of epidural cooling (relative risk, 9.8; 95% CI, 2 to 48; p = 0.005). CONCLUSION EC is a safe and effective technique to increase the ischemic tolerance of the spinal cord during TA or TAA repair. When used in conjunction with a clamp-and-sew technique and a strategy of selective intercostal reanastomosis, EC has significantly reduced the incidence of neurologic deficits after TAA repair.

Transperitoneal versus retroperitoneal approach for aortic reconstruction: A randomized prospective study*

A prospective, randomized study was conducted to compare the retroperitoneal versus transperitoneal approach for elective aortic reconstruction. One hundred thirteen patients (transperitoneal = 59, retroperitoneal = 54) were randomized between March 1987 and October 1988. In addition, to assess the changing course of patients undergoing aortic reconstruction similar data were gathered retrospectively on a group of 56 patients undergoing aortic reconstruction by the same surgeons performed via a transperitoneal approach in 1984 to 1985. Randomized patients were identical in age, male to female ratio, smoking history, incidence and severity of cardiopulmonary disease, indication for operation, and use of epidural anesthetics. Details of operation including operative and aortic cross-clamp times, crystalloid and transfusion requirements, degree of hypothermia on arrival at the intensive care unit, and perioperative fluid and blood requirements did not differ significantly for patients undergoing transperitoneal versus retroperitoneal reconstruction. Respiratory morbidity, as assessed by percent of patients requiring postoperative ventilation, deterioration in pulmonary function tests, and the incidence of respiratory complications, was identical in randomized patients. Other aspects of postoperative recovery including recovery of gastrointestinal function, the requirement for narcotics, metabolic parameters of operative stress, the incidence of major and minor complications, and the duration of hospital stay were similar for randomized patients undergoing transperitoneal and retroperitoneal reconstruction. When compared to retrospectively reviewed patients having aortic reconstruction, randomized patients undergoing transperitoneal and retroperitoneal operations had highly significant (p less than 0.001) reductions in postoperative ventilation, transfusion requirements, and length of hospital stay. Such trends were all independent of transperitoneal versus retroperitoneal approach.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal failure after thoracoabdominal aortic surgery

PURPOSE Renal failure remains a common and morbid complication after complex aortic surgery. This study was performed to identify perioperative factors that contribute to postoperative renal failure. METHODS The perioperative outcomes of 183 patients who underwent thoracoabdominal aortic surgery with supraceliac clamping were reviewed. During the interval from Jan. 1987 to Nov. 1996, thoracoabdominal aneurysm repair was performed in 154 patients (type I, 49 patients [27%]; type II, 21 patients [11.5%]; type III, 55 patients [30%]; type IV, 29 patients [16%]), suprarenal abdominal aortic aneurysm repair in 17 patients (9%), and visceral/renal revascularization procedures in 12 patients (6.5%). Intraoperative management included thoracoabdominal aortic exposure and clamp-and-sew technique with renal artery cold perfusion whenever the renal arteries were accessible (79% of cases). RESULTS Relevant clinical features included preoperative hypertension (85%), diabetes mellitus (8%), single functioning kidney (10%), recent intravenous contrast injection (34%), renal insufficiency (creatinine level greater than 1.5 mg/dl; 24%), and emergent operation (19%). Acute renal failure, defined as both a doubling of serum creatinine level and an absolute value greater than 3.0 mg/dl, occurred in 21 patients (11.5%), of whom five required hemodialysis (2.7%). Variables associated with this complication included a preoperative creatinine level greater than 1.5 mg/dl (p = 0.004) and a total cross-clamp time greater than 100 minutes (p = 0.035). The operative mortality risk (within 30 days; 8%) was significantly increased with renal failure (odds ratio, 9.2; 95% confidence interval, 2.6 to 33; p < 0.005). CONCLUSIONS Renal failure, although uncommon in contemporary practice, greatly increases the risk of early death after thoracoabdominal aortic surgery. The overall incidence of renal failure and dialysis requirement in the present series compare favorably with those reported using other operative techniques, specifically partial left heart bypass and distal aortic perfusion. These data suggest that patients who have preoperative renal insufficiency are prone to postoperative renal failure. Furthermore, regional hypothermic perfusion and minimal clamp times are important elements in the prevention of renal failure after thoracoabdominal aortic surgery.

Epidural cooling for regional spinal cord hypothermia during thoracoabdominal aneurysm repair

PURPOSE We investigated the feasibility of achieving regional hypothermia of the spinal cord with an infusion of iced (4 degrees C) saline solution administered into an epidural catheter while monitoring cerebral spinal fluid (CSF) temperature in eight patients undergoing thoracic or thoracoabdominal aneurysm resection. METHODS As part of the anesthetic management, an epidural catheter was placed at T11-12, and a subarachnoid thermistor catheter was placed at L3-4. Approximately 30 minutes before aortic cross-clamping, iced (4 degrees C) saline solution was infused into the epidural catheter until CSF temperature decreased to approximately 25 degrees C. The infusion was then adjusted to maintain this temperature until the aorta was unclamped. The subarachnoid catheter was also used to measure CSF pressure and provide for CSF drainage. Surgery was performed in all patients with a clamp-and-sew technique with selective intercostal vessel reattachment. RESULTS Infusion of a mean volume of 489 ml (range 80 to 1700 ml) of iced saline solution into the epidural space before aortic cross-clamping led to a decrease in mean CSF temperature to 26.9 degrees C (range 25 degrees to 28.8 degrees C) in 15 to 90 minutes. During cross-clamping and aortic replacement the mean CSF temperature was maintained between 25.2 degrees to 27.6 degrees C and, with discontinuation of the infusion, returned to within 1 degrees C of body core temperature by the end of the procedure. Body core temperature was not significantly affected by the epidural infusion. Mean CSF pressure increased during the epidural infusion but could be reduced by removing saline solution from the epidural space. No postoperative neurologic deficits were observed. CONCLUSION Epidural cooling appears to be a satisfactory method of achieving regional spinal cord hypothermia in patients requiring resection of thoracic or thoracoabdominal aortic aneurysms.

Coagulation changes during thoracoabdominal aneurysm repair

PURPOSE The cause of coagulopathic hemorrhage during thoracoabdominal aneurysm (TAA) repair has not been well defined in human studies. We investigated changes in the coagulation system associated with supraceliac versus infrarenal cross-clamping to address this critical issue. METHODS Blood levels of fibrinogen, the prothrombin fragment F1.2, D-dimer, and factors II, V, VII, VIII, IX, X, XI, and XII were analyzed in 19 patients with TAAs and four patients with abdominal aortic aneurysms (AAAs) at: (A) induction; (B) 30 minutes into supraceliac (TAA) or infrarenal (AAA) clamping; (C) 30 minutes after release of supraceliac or infrarenal clamps; and (D) immediately after surgery. Preoperative and intraoperative variables, including but not limited to aneurysm type, pathologic findings, comorbid conditions, clamp times, volume and timing of blood products, and clinical outcome, were prospectively recorded. Significance was determined by analysis of variance, Students t test, and univariate linear regression. RESULTS Levels of fibrinogen and factors II, V, VIII, VIII, IX, X, XI, and XII decreased (p < 0.05) at time B versus time A and returned to near baseline by time D. D-dimer and F1.2 increased starting at time B and reached significance (p < 0.05) by time D. Data points were compared for the TAA and AAA groups. Although AAA groups demonstrated a trend to factor activity reduction and increased fibrinolysis, the effect was much less pronounced than in TAA and did not approach significance. No correlation of coagulation change with clamping time was present; however, visceral clamping times were all less than 65 minutes (mean, 44 minutes). Blood and factor replacement was initiated after time B. Univariate regression analysis of factor level versus total blood replacement demonstrated a significant (p < 0.04) correlation between the reduction in the levels of factors II, V, VII, VIII, X, and XII, and the increase in the level of D-dimer at time B and subsequent total blood replacement. CONCLUSIONS Thoracoabdominal aneurysm repair is associated with a reduction in clotting factor activity and an increase in fibrinolytic function, which occurs after placement of the supraceliac clamp. Explanations include visceral ischemia or a greater and longer ischemic tissue burden as the likely cause of coagulation alterations. Total blood replacement during TAA procedures was correlated to the degree of factor reduction and fibrinolysis at the time of visceral cross-clamping. An aggressive approach to early blood component replacement and to coagulation monitoring could lessen blood loss during TAA repair and avoid potentially disastrous bleeding complications.

Mesenteric shunting decreases visceral ischemia during thoracoabdominal aneurysm repair

PURPOSE A technique to decrease visceral ischemic time during thoracoabdominal aneurysm (TAA) repair is reported. METHODS A 10 mm Dacron side-arm graft is attached to the aortic prosthesis and positioned immediately distal to the planned proximal thoracic aortic anastomosis. On completion of the anastomosis, a 16 to 22 Fr perfusion catheter is attached to the side-arm graft and inserted into the orifice of the celiac axis or superior mesenteric artery. The cross-clamp is then placed on the aortic graft distal to the mesenteric side-arm graft. Pulsatile arterial perfusion is thus established to the visceral circulation while intercostal anastomoses or reconstruction of celiac, superior mesenteric, and right renal arteries is performed. Visceral ischemic time and the rise in end-tidal Pco2 after reconstruction of the visceral vessels in patients with mesenteric shunting was compared with a control group matched for aneurysm extent and treated immediately before use of the mesenteric shunt technique. RESULTS Between July and Oct, 1996, the technique was applied in 15 patients undergoing type I, II, or III TAA repair with a clamp and sew technique. The mean decrease in systolic arterial pressure was 12.5 +/- 8.5 mm Hg, with a concomitant rise in end-tidal Pco2 (mean, 6.9 +/- 5.8 mm Hg), after perfusion was established through the mesenteric shunt. Mean time to establishment of visceral perfusion through the shunt was 25.5 +/- 4.4 minutes; the resultant decrement in visceral ischemic time averaged 31.3 minutes (i.e., until celiac, superior mesenteric, and right renal arteries were reconstructed). Compared with controls, patients with shunts had a significantly decreased (6.9 +/- 5.8 versus 21.6 +/- 8.4 mm Hg; p = 0.0003) rise in end-tidal CO2 on completion of visceral vessel reconstruction. CONCLUSIONS In-line mesenteric shunting is a simple method to decrease visceral ischemia during TAA repair, and it is adaptable to clamp and sew or partial bypass and distal perfusion operative techniques.

Spinal cord complications after thoracic aortic surgery: Long-term survival and functional status varies with deficit severity

OBJECTIVE Paraplegia after thoracoabdominal aneurysm (TAA) repair has been associated with poor survival. Little information exists concerning the spectrum of severity that characterizes spinal cord ischemic (SCI) complications. This study stratified SCI by deficit severity to determine its impact on late survival and functional outcomes. METHODS A review of our prospectively maintained thoracic aortic database was performed from May 1987 through December 2005 to identify patients who experienced SCI of any extent after TAA repair. During this period, 576 patients underwent descending thoracic aortic repair (93 open, 105 endovascular [TEVAR]) or open TAA repair (279 extent I to III; 99 extent IV). To stratify severity of SCI, we created a spinal cord ischemia deficit (SCID) scale, which is defined as: I, flaccid paralysis; II, average neurologic muscle grade indicating <50% function; and III, average neurologic muscle grade indicating >50% function. Long-term outcomes were evaluated in relation to these groups by actuarial methods. RESULTS During the study period, 64 (11.1%) patients developed SCI of any severity (7 of 105 [6.6%] TEVAR, 57 of 471 [12%] open). These were stratified by SCID level: I, 24 (37.5%); II, 31 (48.4%); and III, 9 (14.1%). SCI was immediate in 33 (54.1%) and delayed in 28 (45.9%). Most SCI (6 of 7) associated with TEVAR was delayed. The 30-day mortality was significantly higher in the SCI group than the overall patient cohort (15 of 64 [23.4%] vs 41 of 512 [8%], P < .001) and varied by SCID level: I, 11 of 24 (45.8%); II, 4 of 31 (12.9%); and III, 0 of 9 (0%; P = .001). The 5-year actuarial survival for all SCI was lower than for non-SCI patients (25% +/- 6% vs 51% +/- 3%, P < .001) and varied linearly with SCID level but was similar between SCID II/III and the non-SCI patients (41% +/- 10% vs 51% +/- 3%, P = .281). No SCID I patients were alive at 5 years. No patients with SCID I recovered the ability to walk, but eight of 11 (73%) with SCID II and the nine (100%) with SCID III could ambulate with or without assistance at last follow-up. CONCLUSION Survival and functional outcomes correlate with SCI severity. Patients with SCID I have a poor long-term outlook. Survival of SCID II/III patients is similar to non-SCI patients; most recover the ability to ambulate.

Neuraxial morphine may trigger transient motor dysfunction after a noninjurious interval of spinal cord ischemia : a clinical and experimental study

Background A patient underwent repair of a thoracoabdominal aortic aneurysm. Epidural morphine, 4 mg, was given for pain relief. After anesthesia, the patient displayed lower extremity paraparesis. This effect was reversed by naloxone. The authors sought to confirm these observations using a rat spinal ischemia model to define the effects of intrathecal morphine administered at various times after reflow on behavior and spinal histopathology. Methods Spinal cord ischemia was induced for 6 min using an intraaortic balloon. Morphine or saline, 30 &mgr;g, was injected intrathecally at 0.5, 2, or 24 h after reflow. In a separate group, spinal cord temperature was decreased to 27°C before ischemia. After ischemia, recovery of motor function was assessed periodically using the motor deficit index (0 = complete recovery; 6 = complete paraplegia). Results After ischemia, all rats showed near-complete recovery of function by 4–6 h. Intrathecal injection of morphine at 0.5 or 2 h of reflow (but not at 24 h) but not saline caused a development of hind limb dysfunction and lasted for 4.5 h (motor deficit index score = 4–6). This effect was reversed by intrathecal naloxone (30 &mgr;g). Intrathecal morphine administered after hypothermic ischemia was without effect. Histopathological analysis in animals that received intrathecal morphine at 0.5 or 2 h after ischemia (but not at 24 h) revealed dark-staining &agr; motoneurons and interneurons. Intrathecal saline or spinal hypothermia plus morphine was without effect. Conclusions These data indicate that during the immediate reflow following a noninjurious interval of spinal ischemia, intrathecal morphine potentiates motor dysfunction. Reversal by naloxone suggests that this effect results from an opioid receptor–mediated potentiation of a transient block of inhibitory neurons initiated by spinal ischemia.

Intraoperative autotransfusion in major vascular surgery

The use of intraoperative autotransfusion provides a safe and cost-effective means of salvaging operative blood loss and reducing or eliminating the use of stored homologous bank blood with its inherent difficulties and risks. The risk of disease transmission or various reactions is minimized. Autotransfusion provides a readily available, more physiologic, and at times life-saving source of blood for patients with rare blood types or patients in whom time does not permit adequate cross-matching. This technique is acceptable to most sects of Jehovahs Witnesses, who normally refuse homologous blood. Our experience during the past six years with autotransfusion in major vascular surgery reveals a mean slavage equivalent to five units of blood loss, and avoidance of using any bank blood in almost half of elective patients. No significant problems occurred due to hemolysis, coagulation abnormalities, or particulate/air emboli, nor any morbidity or mortality specifically related to autotransfusion. We conclude that wider and more frequent use of autotransfusion technics is appropriate.

Regional hypothermia with epidural cooling for prevention of spinal cord ischemic complications after thoracoabdominal aortic surgery

Multiple operative adjuncts have been developed and clinically applied to reduce the incidence of spinal cord ischemic complications (SCI) after thoracoabdominal aneurysm (TAA) repair. Hypothermia is known to reduce oxygen requirements in central nervous tissue and has been successfully applied in the arena of central cardioaortic surgery. Based on our experimental and clinical results, we have employed regional hypothermia by epidural cooling to ameliorate SCI during TAA repair in over 300 patients. This review describes the results obtained in our experience using an approach to TAA repair whereupon the spinal cord is protected during surgery by regional hypothermia via epidural cooling.