Measuring Cerebrospinal Fluid (CSF) Glucose Levels in Patients Under Going an Elective Cesarean Section With Spinal Anesthesia

Detailed Description Spinal anesthesia consists of putting drugs into the cerebrospinal fluid (CSF), the fluid that surrounds the spinal cord. This allows the subject to be awake but "numb" from the chest down during your operation. Spinal anesthesia is done by inserting a small needle (spinal needle) in the subject's back into the space (subarachnoid space) containing the CSF. Once the spinal needle is in the subarachnoid space a small amount of fluid (CSF) is seen coming out of the spinal needle, confirming that the needle is in the right space. The anesthesiologist then injects local anesthetic into the CSF to freeze or numb the area for your surgery and some pain medication, such as morphine, to relieve pain after the operation.

CSF contains glucose (sugar) and the presence of glucose in the fluid that comes out of a spinal needle will confirm that the fluid is CSF. If spinal anesthesia is used for cesarean section following failed epidural anesthesia (may happen in women who had an epidural for labor pain relief who then need a cesarean section) it may be difficult to tell whether the fluid that comes out of the spinal needle is CSF or local anesthetic used for the epidural. In other words, the needle may be in the epidural space instead of the subarachnoid space and so the spinal anesthetic would not work. A simple bedside test to confirm that the fluid is CSF could potentially prevent this situation. Local anesthetic does not contain glucose so testing the fluid for glucose could help determine if the needle is in the proper space for spinal anesthesia.

The study will determine the normal levels of CSF glucose using three different glucose meters (Nova Stat Strip, Abbott Precision Xtra and Roche Accucheck Inform 2 which are bedside devices that measure glucose). A glucose meter is used by people with diabetes to check their blood sugar levels using a drop of their blood. The results of this study will hopefully provide the basis for a further study that would look at whether it is possible to distinguish CSF from epidural fluid when spinal anesthesia is done following a failed epidural anesthetic. This could help prevent failures of spinal anesthesia in that situation.

This is a prospective, observational study.

The Cesarean Section and spinal anesthesia will continue as per usual practice at BCWH. Consenting subjects will receive the same drugs and all aspects of the anesthetic care will be the same except for two differences. The first, is that the anesthesiologist will collect a very small amount of CSF (0.5 mL which is 1/10 of a teaspoon) to measure the amount of glucose. This testing will be done in the operating room with the three glucose meters (Nova Stat Strip, Abbott Precision Xtra and Roche Accucheck Inform 2) and in the laboratory (using one of the two machines: 1)Vitros 9 or 2)Vitros 5,1 FS). Secondly, blood sugar level will be tested by taking up to three drops of blood from a pinprick in the subject's toe to compare with the CSF glucose level.

Inclusion criteria

• Healthy women (American Society of Anesthesiologists (ASA) 1 or 2 classification) with a singleton pregnancy who are undergoing Cesarean section under spinal anesthesia.
• Age 19 years or older
• Understand written and oral English

Exclusion criteria

• Women who are having an emergency Cesarean section
• Women who are having epidural, combined spinal epidural or general anesthesia
• Women who have a contraindication to spinal anesthesia
• Women who are less than 19 years of age
• Women with an abnormality of glucose metabolism such as diabetes mellitus, gestational diabetes
• Women receiving dextrose intravenously prior to their surgery
• Women in whom technical problems are anticipated during insertion of the spinal (such as scoliosis) ot who may have a hematological abnormality o If there is technical difficulty during insertion of the spinal there is an increased chance of trauma, resulting in blood entering the CSF (bloody tap). This could potentially be a source of glucose. Women with a hematological abnormality are at increased of bleeding which may increase the chance of blood in the CSF.