Acid-Base Imbalance, Cerebrospinal Fluid, Pregnancy, Respiratory Alkalosis
Conditions
Brief summary
The third trimester of pregnancy is typically characterized by the development of a marked respiratory alkalosis. The possible role of pregnancy-induced variations of cerebrospinal fluid (CSF) acid-base characteristics on the development of hypocapnic alkalosis is still unknown. Aim of this study is to characterize, according to Stewart's approach, the acid-base equilibrium of CSF and arterial plasma of pregnant women and compare the results with data obtained from fertile, non-pregnant women.
Detailed description
The reduction in plasma PCO2 correlates with gestational age and was shown to be associated to plasma progesterone concentrations. We hypothesize that pregnancy-related haemodilution, inducing a reduction in CSF Strong Ion Difference (SID), might have a role in the development of pregnancy-related hypocapnic alkalosis. Samples of CSF and arterial plasma of pregnant women with gestational age \> 35 weeks undergoing spinal anesthesia for elective caesarean section will be analyzed for blood gases, pH, electrolytes, osmolality, albumin and haemoglobin concentration. In addition plasma copeptin levels will be analyzed. The same measurements will be performed in fertile, non-pregnant women undergoing spinal anesthesia for elective surgery.
Interventions
DIAGNOSTIC_TESTAcid - Base characterization
Samples of cerebrospinal fluid and arterial blood will be collected anaerobically to measure acid-base variables, electrolytes, albumin, progesterone and copeptin levels
Sponsors
University of Milan
Fondazione IRCCS Ca' Granda, Ospedale Maggiore Policlinico
Study design
Observational model
CASE_CONTROL
Time perspective
PROSPECTIVE
Eligibility
Sex/Gender
FEMALE
Age
18 Years to No maximum
Healthy volunteers
No
Inclusion criteria
* Pregnancy with gestational age \> 35 weeks * Scheduled elective cesarean section under spinal anesthesia
Exclusion criteria
* known respiratory or neurologic disease * multiple pregnancies
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Strong Ion Difference | 1 day | Strong Ion Difference (expressed in milliequivalents per Liter \[mEq/L\]) of cerebrospinal fluid and arterial plasma |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Sum of albumin (expressed in mmol/L) and Phosphates (expressed in mmol/L) | 1 day | The total amount of weak non carbonic acids, i.e. the sum of albumin and phosphates (both expressed in mmol/L) of cerebrospinal fluid and arterial plasma |
| Difference between cerebrospinal fluid and arterial plasma Strong Ion Difference (Delta SID) | 1 day | The difference between plasma and cerebrospinal fluid SID (expressed in mEq/L) will be calculated as marker of electrolyte inbalance between these two extracellular fluid compartments. Delta SID = SIDcsf - SIDplasma |
| Difference between cerebrospinal fluid and arterial plasma partial pressure of CO2 (Delta PCO2) | 1 day | The difference between cerebrospinal fluid and arterial plasma PCO2 (expressed in mmHg) will be calculated as a marker of acid-base equilibrium between these two extracellular fluid compartments. Delta PCO2 = SIDplasma - SIDcsf |
| Progesterone levels | 1 day | Plasma and CSF Progesterone levels (expressed in ng/mL) will be measured |
| Copeptin levels | 1 day | Plasma copeptin levels (expressed in pmol/L) will be measured as a marker of antidiuretic hormone activity |
| Partial pressure of carbon dioxide (PCO2) | 1 day | PCO2 (expressed in millimeters of Mercury \[mmHg\]) of cerebrospinal fluid and arterial plasma |
Other
| Measure | Time frame | Description |
|---|---|---|
| Plasma progesterone PCO2 correlation | 1 day | Correlation between plasma progesterone concentration and plasma PCO2 |
| CSF progesterone PCO2 correlation | 1 day | Correlation between CSF progesterone concentration and CSF PCO2 |
| Osmolality PCO2 correlation | 1 day | Correlation between CSF osmolality and PCO2 |
| SID PCO2 correlation | 1 day | Correlation between CSF SID and PCO2 |
Countries
Italy
Contacts
Primary ContactThomas Langer, MD
Outcome results
None listed