Novel application of acetazolamide to reduce cerebrospinal fluid production in patients undergoing thoracoabdominal aortic surgery.

OBJECTIVES: Paraplegia is a rare but devastating complication, which may follow thoracoabdominal aortic surgery. Many adjuncts have been developed to reduce this risk including cerebrospinal fluid (CSF) drainage. Acetazolamide (carbonic anhydrase inhibitor) is a drug used to counteract mountain sickness and one of its effects is to reduce CSF production. Here, we report its first postoperative application in thoracoabdominal surgery with the aim of reducing cerebrospinal cord perfusion pressure and reducing risk of paraplegia. METHODS: We retrospectively reviewed 6 patients who have been treated with this drug between 2011 and 2012 who were undergoing thoracoabdominal aortic surgery. Our indications were decided to include: (i) patients in whom a spinal drain could not be positioned; (ii) patients with blood-stained CSF; (iii) patients in whom the volume of CSF drained was outside guidelines; (iv) patients in whom CSF pressure was elevated; (v) patients with excessive vasopressor usage and (vi) patients with postoperative neurological dysfunction as measured by motor-evoked potentials or clinical examination. All were given 500 mg intravenous acetazolamide, not more than eight hourly, for a duration dependent on response. RESULTS: In the 6 patients, 2 received a single dose of the drug and responded by an immediate drop in intracranial pressure (ICP) pressure. Of the 4 who received multiple doses of the drug, 1 had an immediate decline in ICP after each of the first six doses, while 3 had no discernable response. CONCLUSIONS: This is the first report of the efficacy of acetazolamide in reducing CSF production and lowering ICP during thoracoabdominal aortic surgery. We believe that its use will be beneficial in the 6 patient groups described. Our experience suggests there are 'responders' and 'non-responders', the characteristics of whom are yet to be defined. Its efficacy in reducing not just CSF volume and ICP but also clinically relevant morbidity such as paraplegia, is the subject of a planned randomized controlled trial. This report serves to raise awareness of the possible efficacy of this drug when normal management strategies are limited or exhausted.

Recommendations for haemodynamic and neurological monitoring in repair of acute type a aortic dissection.

During treatment of acute type A aortic dissection there is potential for both pre- and intra-operative malperfusion. There are a number of monitoring strategies that may allow for earlier detection of potentially catastrophic malperfusion (particularly cerebral malperfusion) phenomena available for the anaesthetist and surgeon. This review article sets out to discuss the benefits of the current standard monitoring techniques available as well as desirable/experimental techniques which may serve as adjuncts in the monitoring of these complex patients.

Cerebral perfusion.

Aortic arch surgery necessitates interrupted brain perfusion and carries a risk of brain injury. Various brain protective techniques have been advocated to reduce risk including hypothermic arrest and retrograde or selective antegrade perfusion. Knowledge of the pathophysiologic consequences of deep hypothermia, may aid the surgeon in deciding when to initiate circulatory arrest and for how long. Retrograde cerebral perfusion use was advocated to prolong safe arrest durations but may not improve outcomes. Selective antegrade cerebral perfusion appears to have become the preferred method of brain protection. However, the delivery conditions and optimal perfusate constitution require further study.

Nonneurologic morbidity and profound hypothermia in aortic surgery.

BACKGROUND: Use of profoundly hypothermic cardiopulmonary bypass may increase the risk of postoperative bleeding and lung and renal dysfunction. The aim of this study was to analyze postoperative blood loss and indices of pulmonary and renal dysfunction in patients undergoing proximal aortic surgery with and without the use of profound hypothermia to determine risk factors for nonneurologic morbidity. METHODS: Risk factors for blood loss, transfusion requirement, and pulmonary and renal dysfunction were studied in 116 patients undergoing thoracic aortic surgery with profoundly or moderately hypothermic cardiopulmonary bypass. RESULTS: Overall mortality was 8.6%. Mean (+/- standard deviation) cardiopulmonary bypass times were 191 +/- 53 minutes (profoundly hypothermic group) and 131 +/- 48 minutes (moderately hypothermic group; p < 0.0001). The incidence of blood loss more than 1 L or resternotomy for bleeding was 25% (29 patients). Fifteen patients (12.9%) experienced postoperative pulmonary dysfunction, and 25 patients (21.6%) had postoperative renal dysfunction. Forty-one patients (35.3%) had a prolonged intensive therapy unit length of stay. Multivariate analysis demonstrated that prolonged cardiopulmonary bypass time was the only predictor of postoperative hemorrhage and resternotomy for bleeding (p = 0.03). Increased intensive therapy unit length of stay was predicted by total arch replacement (p = 0.01) and low 6-hour ratio of partial pressure of arterial oxygen to inspired fraction of oxygen (p = 0.05). Increased preoperative creatinine (p = 0.002) and emergency status (p = 0.015) predicted postoperative renal dysfunction. Low 6-hour ratio of partial pressure of arterial oxygen to inspired fraction of oxygen was predicted by increased preoperative creatinine (p = 0.03) and prolonged cardiopulmonary bypass time (p = 0.03). CONCLUSIONS: Profound hypothermia may cause a coagulopathy, but procedure extent is the primary determinant of postoperative bleeding. Profoundly hypothermic cardiopulmonary bypass does not appear to be a risk factor for renal or early pulmonary dysfunction or intensive therapy unit length of stay.