Intraocular pressure during neurosurgical procedures in context of head position and loss of cerebrospinal fluid

Abstract

OBJECTIVE Perioperative visual loss (POVL) is a rare but serious complication in surgical disciplines, especially in spine surgery. The exact pathophysiology of POVL remains unclear, but elevated intraocular pressure (IOP) is known to be part of it. As POVL is rarely described in patients undergoing intracranial or intradural surgery, the aim of this study was to investigate the course of IOP during neurosurgical procedures with opening of the dura mater and loss of CSF. METHODS In this prospective, controlled trial, 64 patients fell into one of 4 groups of 16 patients each. Group A included patients undergoing spine surgery in the prone position, group B patients had intracranial procedures in the prone position, and group C patients were treated for intracranial pathologies in a modified lateral position with the head rotated. In groups A-C, the dura was opened during surgery. Group D patients underwent spine surgeries in the prone position with an intact dura. IOP was measured continuously pre-, peri-, and postoperatively. RESULTS In all groups, IOP decreased after induction of anesthesia and increased time dependently after final positioning for the operation. The maximum IOP in group A prior to opening of the dura was 28.6 ± 6.2 mm Hg and decreased to 23.44 ± 4.9 mm Hg directly after dura opening (p < 0.0007). This effect lasted for 30 minutes (23.5 ± 5.6 mm Hg, p = 0.0028); after 60 minutes IOP slowly increased again (24.5 ± 6.3 mm Hg, p = 0.15). In group B, the last measured IOP before CSF loss was 28.1 ± 5.0 mm Hg and decreased to 23.5 ± 6.1 mm Hg (p = 0.0039) after dura opening. A significant IOP decrease in group B lasted at 30 minutes (23.6 ± 6.0 mm Hg, p = 0.0039) and 60 minutes (23.7 ± 6.0 mm Hg, p = 0.0189). In group C, only the lower eye showed a decrease in IOP up to 60 minutes after loss of CSF (opening of dura, p = 0.0007; 30 minutes, p = 0.0477; 60 minutes, p = 0.0243). In group D (control group), IOP remained stable throughout the operation after the patient was prone. CONCLUSIONS This study is the first to demonstrate that opening of the dura with loss of CSF during neurosurgical procedures results in a decrease in IOP. This might explain why POVL predominantly occurs in spinal but rarely in intracranial procedures, offers new insight to the pathophysiology of POVL, and provides the basis for further research and treatment of POVL. German Clinical Trials Register (DRKS) no.: DRKS00007590 (drks.de).

The Effects of Acute Intracranial Pressure Changes on the Episcleral Venous Pressure, Retinal Vein Diameter and Intraocular Pressure in a Pig Model

“…[30][31][32]35,36,42 In a recent study of 64 subjects undergoing neurosurgical procedures, researchers found that intraoperative opening of dura mater with CSF loss was associated with a significant decrease of IOP lasting 60 minutes, which was independent of head positioning, procedure type, blood loss or blood pressure measurements. 43 The association between ICP and IOP has also been shown in animal models. In a primate animal model where ICP was manipulated using a sub-cranial balloon, the IOP increased in seven of eight animals within minutes of ICP increase.…”

Systematic Review and Meta-Analysis of Prone Position on Intraocular Pressure in Adults Undergoing Surgery

“…In total, 135 records were identified for possible inclusion, and of these, 9 studies were included in the systematic review and meta-analysis. Four studies had multiple participant groups, [67][68][69][70] resulting in a total of 14 participant groups and 229 participants for analysis. Table 1 contains a summary of the studies included in this review and meta-analysis.…”

“…The greatest number of studies were published in 2018 (studies [s] ¼ 2) with the greatest number of participants also occurring in 2018 (n ¼ 88). [67][68][69] Participant and Surgery Characteristics Participant and surgery characteristics are shown in Table 2. The mean (SD) age of the participants was 53.2 (8.1) years and ranged from 43.3 to 69 years.…”

“…As shown in Table 2, the mean (SD) duration of surgery was 156.0 (24.2) minutes with a range of 120 to 181 minutes. Several researchers reported the duration of prone position as a significant contributing factor between increasing IOP and prone position 1,29,67,74 ; however, 2 researchers reported the relationship between duration of the position and increased IOP was not significant. 68,69 The mean (SD) estimated blood loss was 330.1 (222.1) mL with a range of 120 to 615 mL.…”

Extendable mirrors to improve anesthesia provider comfort for eye and positioning checks in prone patients: A pilot study

“…Though the pathogenesis of POVL from retinal artery occlusion is most likely multifactorial, external ocular compression adds to the already elevated intraocular pressure from prone positioning, which further reduces perfusion pressure thereby leading to retinal ischemia. 9 Because ocular perfusion pressure depends on the gradient between mean arterial pressure and intraorbital pressure, both hypotension and elevated intraocular pressure may lead to POVL. If intraorbital pressure surpasses central retinal artery pressure, central retinal artery occlusion ensues.…”