Changes in optic nerve sheath diameter during laparoscopic procedures in trendelenburg position-A prospective observational study

INTRODUCTION

Laparoscopic surgeries are increasingly performed today for their perceived benefits including less trauma, reduced risk of bleeding, less pain, faster recovery, and shorter hospital stay, and favourable cosmetic outcomes As a consequence, laparoscopic surgeries have become a valid and reliable alternative to open surgery in last few decades. In order to improve the visualization of the surgical field, CO2 pneumoperitoneum (PP) and a concomitant steep head-down position Trendelenburg. (TP) are often applied to patients undergoing laparoscopic urology and gynaecology procedures. However, concomitant use of PP and TP leads to an increase in intraabdominal pressure which may further provoke many systemic physiological alterations including a decrease in venous return and increase in cerebral blood flow, intracranial pressure (ICP) and intraocular pressure. Pneumoperitoneum elevates ICP because of the increased abdominal pressure and ICP increases even further in the Trendelenburg position.

Halverson et al determined that elevation in ICP is most likely owing to impaired cerebrospinal fluid drainage at the lumbar venous plexus. Rosenthal et al. later described a two-staged mechanism of ICP elevation in laparoscopic surgery. They proposed that an increase in intraabdominal pressure due to PP compresses inferior vena cava and impairs venous drainage from the lumbar plexus. According to the authors, in addition to the compression on inferior vena cava, the increase in intraabdominal pressure elevates the diaphragm and consequently leads to an increase in intrathoracic pressure which further impairs right atrial and ventricular filling and impairs the drainage of superior vena cava. The increase in central venous pressure and the resultant decrease in drainage from lumbar plexus and central nervous system are likely to contribute to the elevation of ICP occurring during laparoscopic surgery.

NEED FOR THE STUDY

Raised intracranial pressure arising following pneumoperitoneum and Trendelenburg position is a concern and may be harmful for patients with unrecognized intracranial mass lesions. Direct ICP measurement using a small pressure-sensitive probe inserted through the skull is the gold standard for monitoring ICP. For routine surgeries, the risks of such an invasive test outweighs the benefits. Measurement of the ONSD is now emerging as a useful non-invasive surrogate marker to monitor raised ICP. This study will evaluate the effect of pneumoperitoneum and head low position on ICP by measuring the ONSD.

AIM OF THE STUDY:

To assess the effect of pneumoperitoneum and trendelenburg position on optic nerve sheath diameter in laparoscopic surgeries.

OBJECTIVES OF THE STUDY:

PRIMARY

1. To measure the changes in optic nerve sheath diameter in patients undergoing laparoscopic surgeries in trendelenburg position.

SECONDARY

1. To correlate changes in optic nerve sheath diameter with angulation of table in trendelenburg position

2.To correlate ONSD changes with duration of pneumoperitoneum and trendelenburg position.

MATERIALS AND METHODS

INCLUSION CRITERIA

1. Both males and females

2. Age 18 years and <-60 years

3. ASA I and II patients

4. Scheduled for elective emergency laparoscopic surgeries in Trendelenburg position.

EXCLUSION CRITERIA

1. Patients with previous history of ocular disease, ocular surgery, glaucoma

2. Patients with previous history of neurologic disease transient ischemic attack or cerebrovascular disease in past 3 months

3. Patients with any intracranial pathology

SOURCE OF DATA

Place of study - St John’s Medical College and Hospital, Bengaluru

Study period -24 months

METHODS

STUDY DESIGN: An observational prospective cohort study

METHODOLOGY

After obtaining IEC approval, patients who meet the inclusion criteria and consenting for the study will be enrolled. Once inside the operating room, standard monitors- electrocardiogram, pulse oximetry and non-invasive arterial pressure will be connected and baseline vitals will be recorded. Premedication will be done with glycopyrrolate, Ondansetron and midazolam Fentanyl 2 mcg per kg will be administered and 3 minutes later the first measurement of ONSD will be taken. Patient will then be induced with propofol followed by atracurium to  facilitate orotracheal intubation. Pressure control ventilation will be used and ventilator parameters will be adjusted to maintain normocapnea (35-40) Pneumoperitoneum with CO2 will be established by the surgeon within the acceptable pressure limits. Trendelenburg position will be provided when requested by the surgeon to facilitate surgical exposure and table angulation will be measured with the help of an application known as ANGLE METER. Anaesthesia will be maintained with air/oxygen/gas mixture (0.8-1 MAC of isoflurane). Morphine and paracetamol will be used for analgesia. Second measurement of optic nerve sheath diamete