Canadian Journal of Anaesthesia

To test the hypothesis that a physiological compensatory mechanism maintains respiratory gas exchange during normovolaemic haemodilution. Pulmonary gas exchange capacity was evaluated in seven healthy subjects by measuring the lung diffusion of carbon monoxide (DLCO). During the measurement, various breath-holding times, inspiratory volumes, and sitting or supine positions, were randomly selected in an attempt to alter pulmonary capillary perfusion. KCO was calculated as the percentage of theoretical values of the ratio of DLCO by alveolar volume and normalized by sex, age, and height. Normovolaemic haemodilution (NH) was performed by bleeding an average blood volume of 1 L with simultaneous Dextran 60 replacement to obtain an haematocrit below 35%. After NH, haemoblogin concentration [Hb] decreased from 14.94 ± 0.96 to 12.5 ± 0.98 g · dl−1 (P < 0.001). KCO decreased (P < 0.02) but remained closely correlated to [Hb] at every lung volume (< 0.02). Breathholding time and body position had no effect. Moderate NH impairs pulmonary gas exchange capacity in awake, resting healthy subjects. There is no evidence of any compensatory mechanism since the KCO vs [Hb] relationship is unchanged.

Paraplegia is an uncommon yet devastating complication following thoracotomy, usually caused by compression or ischemia of the spinal cord. Ischemia without compression may be a result of global ischemia, vascular injury and other causes. Epidural anesthesia has been implicated as a major cause. This report highlights the fact that perioperative cord ischemia and paraplegia may be unrelated to epidural intervention. A 71-yr-old woman was admitted for a left upper lobectomy for resection of a non-small cell carcinoma of the lung. The patient refused epidural catheter placement and underwent a left T5–6 thoracotomy under general anesthesia. During surgery, she was hemodynamically stable and good oxygen saturation was maintained. Several hours following surgery the patient complained of loss of sensation in her legs. Neurological examination disclosed a complete motor and sensory block at the T5–6 level. Magnetic resonance imaging (MRI) revealed spinal cord ischemia. The patient receivediv steroid treatment, but remained paraplegic. Five months following the surgery there was only partial improvement in her motor symptoms. A follow-up MRI study was consistent with a diagnosis of spinal cord ischemia. In this case of paraplegia following thoracic surgery for lung resection, epidural anesthesia/analgesia was not used. The MRI demonstrated evidence of spinal cord ischemia, and no evidence of cord compression. This case highlights that etiologies other than epidural intervention, such as injury to the spinal segmental arteries during thoracotomy, should be considered as potential causes of cord ischemia and resultant paraplegia in this surgical population.