鈴木 万三

BACKGROUND: Maternal hypotension is a common hemodynamic consequence of spinal anesthesia during cesarean delivery, but low-dose spinal anesthesia (<9 mg bupivacaine) ensures stable hemodynamics and reduces motor block. The purpose of this retrospective observational study was to examine the effects of baricity of intrathecal administration of diluted bupivacaine in combined spinal-epidural anesthesia (CSEA) for cesarean delivery on maternal hypotension and motor block after surgery. METHODS: The anesthesia and nursing records of 35 patients who had given birth by cesarean delivery under CSEA with intrathecal administration of plain or hyperbaric bupivacaine diluted in cerebrospinal fluid were reviewed. All patients were assigned to who received hyperbaric bupivacaine (hyperbaric group) or plain bupivacaine (plain group). Definition of feasibility of cesarean delivery by diluted low dose bupivacaine was set as no requirement of epidural administration of levobupivacaine during surgery. The incidences of hypotension (nadir blood pressure less than 80% of preanesthetic value) and motor block were reviewed. RESULTS: In 24 of the patients (68%), no additional epidural anesthesia was needed during surgery. One patient (3%) required additional epidural anesthesia before delivery. Feasibility of cesarean delivery was not different between hyperbaric group and plain group (p>0.99). Eighteen of the patients (51%) did not require vasopressors, while 17 (49%) developed hypotension. There was no difference in incidence of maternal hypotension between hyperbaric and plain group. Only 6 patients (17%) required more than 3 times of administration of vasopressors among all patients. Modified Bromage scale scores were recorded in 28 of the patients (80%); scores of 0 (no motor block) were recorded in seven of them, and 1 in eight of them. CONCLUSION: Low-dose either plain or hyperbaric bupivacaine diluted in cerebrospinal fluid to approximately twice the volume may provide sufficient analgesia, fast motor recovery. Incidence of maternal hypotension was similar in hyperbaric and plain group.

The Sensmart Model X-100 (Nonin Medical Inc, Plymouth, MN, USA) is a relatively new device that possesses two sets of emitters and detectors and uses near infrared spectroscopy (NIRS) to measure regional cerebral oxygen saturation (rSO2). The value of rSO2 obtained by other NIRS devices is affected by physiological and anatomical variables such as hemoglobin concentration, area of cerebrospinal fluid (CSF) layer and skull thickness. The effects of these variables have not yet been determined in measurement of rSO2 by Sensmart Model X-100. We examined the effects of area of CSF, hemoglobin concentration, and skull thickness on the values of rSO2 measured by Sensmart Model X-100 and tissue oxygen index (TOI) measured by NIRO-200NX (Hamamatsu Photonix, Hamamatsu, Japan). Forty neurosurgical, cardiac and vascular surgical patients who underwent preoperative computed tomographic (CT) scan of the brain were enrolled in this study. Regional cerebral oxygen saturation (rSO2) at the forehead was measured sequentially by NIRO-200NX and by Sensmart Model X-100. Simultaneously, mean arterial pressure, hemoglobin concentration, and partial pressure of carbon dioxide in arterial blood (PaCO2) were measured. To evaluate the effects of anatomical factors on rSO2, we measured skull thickness and area of CSF layer using CT images of the brain. Multiple regression analysis was used to examine the relationships between the rSO2 values and anatomical and physiological factors. The area of the CSF layer and hemoglobin concentration had significant associations with rSO2 measured by the Sensmart Model X-100, whereas none of the studied variables was significantly associated with TOI. The measurement of rSO2 by Sensmart Model X-100 is not affected by the skull thickness of patients. Area of the CSF layer and hemoglobin concentration may be the main biases in measurement of rSO2 by Sensmart Model X-100.

Among patients who develop anaphylaxis during anesthesia, anaphylaxis caused by a neuromuscular blocking agent has the highest incidence. In patients who developed IgE-mediated anaphylaxis, and cross-reactivity among NMBAs is a concern in subsequent anesthetic procedures. We present a patient who developed rocuronium-induced anaphylaxis in whom the skin prick test (SPT) and intradermal test (IDT) could identify a safe drug to use in the subsequent anesthetic procedure. A 32-year-old female developed anaphylactic shock at the induction of general anesthesia. She recovered by administration of hydrocortisone and epinephrine. Skin tests including the SPT followed by the IDT revealed rocuronium as the drug that caused anaphylaxis and vecuronium as a safe drug to use for the subsequent general anesthesia. She safely underwent surgery with general anesthesia using vecuronium one month after the skin testing. There are not many reports on the effectiveness of the SPT followed by IDT in identifying the causative drug as well as a safe drug to use in the subsequent anesthetic procedure following anaphylaxis during anesthesia. The usefulness of the SPT should be re-evaluated.