Intra-ocular pressure levels during extracorporeal circulation in man

Intra-ocular pressure during cardiopulmonary bypass--a comparison of crystalloid and colloid priming solutions

Raised intra-ocular pressure secondary to alterations in plasma oncotic pressure has been implicated in the development of optic neuropathy after cardiopulmonary bypass. Patients presenting for open heart surgery received either crystalloid (n = 9) or colloid (n = 10) priming solutions for cardiopulmonary bypass. No differences in intra-ocular pressure or plasma oncotic pressure occurred between the groups before the onset of cardiopulmonary bypass. Five minutes after the start of bypass the median intra-ocular pressure increased to 31 mmHg in the crystalloid group compared with 13 mmHg in the colloid group (p < 0.05). At the same time plasma oncotic pressure decreased from approximately 20 mmHg in both groups to 10.6 mmHg with crystalloid and 15.7 mmHg with colloid primed cardiopulmonary bypass solutions (p < 0.05). Over the following hour of cardiopulmonary bypass, intra-ocular pressure and plasma oncotic pressure tended to return towards their pre-cardiopulmonary bypass values. Changes in plasma oncotic pressure, through fluid shifts, may have contributed towards this unexpected increase in intra-ocular pressure with crystalloid primed cardiopulmonary bypass.

Intraocular pressure after cardiopulmonary bypass surgery

The ocular effects of cardiopulmonary bypass surgery were prospectively studied in 46 patients. We examined preoperative and post-operative visual acuity, intraocular pressure, body weight, fluids infused during surgery, hematocrit, and cardiopulmonary bypass time. On the first postoperative day mean intraocular pressure increased 2.1 mm Hg (P = .003) from baseline preoperative levels. Over the first postoperative day intraocular pressure increased in 29 (63%) of the patients. Three patients (7%) had a greater than 10 mm Hg rise. The mean intraocular pressure returned to baseline by the third postoperative day. Patient weight increased from preoperative levels an average of 9.3 lbs (P less than .0001) on day 1 and 6.5 lbs on day 3. Mean hematocrit decreased 11.3% (P less than .0001) on day 1 from baseline and remained at that level through day 3. None of the patients complained of visual dysfunction during the course of this study and none showed more than a two-line decrease in near visual acuity. The increase in intraocular pressure did not correlate with the postoperative weight gain or hemodilution. However, the medications necessary after cardiac surgery may be a significant confounding variable. This study demonstrates that one cause of ocular problems from cardiopulmonary bypass surgery may be related to the dynamics of intraocular pressure.

Intraocular pressure during cardiopulmonary bypass

Intraocular pressure was measured in 24 patients undergoing elective cardiopulmonary bypass surgery. There was a rapid rise when the bypass circulation began, and this was maintained for about 30 minutes. A simultaneous drop in arterial perfusion pressure and packed cell volume occurred. We suggest that marked haemodilution is responsible for this effect, through increased ocular blood flow and low colloidal osmotic pressure. The possible aetiological significance in relation to ischaemic optic neuropathy complicating cardiopulmonary bypass is discussed.