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Biomedical subjects

D D Hood

Publications and source records attributed to D D Hood.

28 records · Page 2Linked to original sources
PubMed1995

Computer-controlled epidural infusion to targeted cerebrospinal fluid concentrations in humans. Clonidine.

BACKGROUND: Pharmacokinetically designed infusions have been demonstrated to achieve rapidly and maintain desired concentrations of drug in plasma after intravenous administration. In this study we tested whether a similar approach, targeting concentrations in cerebrospinal fluid (CSF), could be used with epidural administration of the alpha 2-adrenergic analgesic clonidine. METHODS: After institutional review board approval and informed consent had been obtained, seven healthy volunteers received a clonidine infusion through a lower lumbar epidural catheter. Infusion of clonidine (10 micrograms/ml) was controlled by the STANPUMP program for sequential 75-min periods to targeted CSF clonidine concentrations of 25, 50, 75, and 150 ng/ml. Before reprogramming to the next higher targeted concentration, mean arterial blood pressure and heart rate were measured; blood was obtained for clonidine and catecholamine assays; and visual analog score for sedation and pain to immersion of foot and hand in ice water were obtained. CSF was collected during infusion with an indwelling lumbar intrathecal catheter and was analyzed for clonidine, catecholamines, and acetylcholine. RESULTS: CSF clonidine concentrations rapidly increased and were maintained at steady values with the stepped infusion, although observed concentrations were consistently greater than targeted. The relation between CSF clonidine concentration and analgesia in the foot was similar to that previously observed after epidural bolus administration. Clonidine also was associated with concentration-dependent sedation; decreased mean arterial blood pressure, heart rate, and CSF norepinephrine concentration; and increased CSF acetylcholine concentration. CONCLUSIONS: This study suggests that pharmacokinetically designed infusions of drugs in the epidural space in humans can maintain steady concentrations of drug in CSF. In addition to providing a useful tool for investigation of mechanisms of action and drug interactions, this technique may improve analgesia and diminish side effects from epidurally administered analgesics.

Adult↗
PubMed1994

An isobolographic study of epidural clonidine and fentanyl after cesarean section.

Although the epidural administration of clonidine and fentanyl provides pain relief after surgery, the interaction between the two drugs has not been examined formally. This study used an isobolographic method to determine whether epidurally administered fentanyl and clonidine interact in an additive or synergistic manner. Ninety women with moderate to severe pain after elective cesarean section under epidural anesthesia were studied. Using a randomized, double-blind protocol, we assigned each patient to receive a single epidural injection of one of three doses of fentanyl, clonidine, or a fixed ratio combination. Pain relief, blood pressure (BP), heart rate (HR), and sedation were measured 15 min after injection. Each drug alone and in combination produced analgesia, as measured by pain relief scores, and reduced need for intravenous morphine. Although the effective dose producing analgesia in 50% of patients (ED50) for the mixture was only 52% of that predicted by an additive interaction, this did not differ significantly from additivity, likely due to large variability. Clonidine, alone or in combination with fentanyl, produced a minor reduction in BP, but did not affect HR or cause more sedation than fentanyl. Unlike studies in rodents, this clinical study did not demonstrate synergy between fentanyl and clonidine. This could reflect a true species difference or differences in methodologies used. Nonetheless, a reduced dose of fentanyl and clonidine can be combined for excellent analgesia.

Adult↗
PubMed1993

Anesthetic and obstetric outcome in morbidly obese parturients.

BACKGROUND: Large studies reporting anesthetic outcome for morbidly obese parturients are lacking. This study compares the anesthetic and obstetric outcome in morbidly obese parturients and matched control parturients. METHODS: Anesthesia records were prospectively collected for all patients delivering between September 1978 and November 1989 whose weight exceeded 136.4 kg (300 pounds) at the time of delivery. A retrospective control patient group was collected by matching the first patient weighing less than 136.4 kg, delivered in the same month by the same obstertrician, to the corresponding morbidly obese parturient. Anesthetic and obstetric outcome variables were extracted from medical records and analyzed. RESULTS: Sixty-two percent of 117 morbidly obese women underwent cesarean section, while only 24% of control patients delivered abdominally (P < 0.05). Forty-eight percent of all laboring morbidly obese parturients required emergency cesarean section, compared with 9% of control laboring parturients (P < 0.05). Epidural anesthesia was used successfully for labor and cesarean delivery in 74 of 79 morbidly obese women and 66 of 67 control patients. When compared with control patients, initial epidural anesthesia failure was significantly more likely in morbidly obese women, requiring epidural catheter replacement. Difficult tracheal intubation occurred in 6 of 17 morbidly obese women, compared with 0 of 8 control women (P = 0.06). Morbidly obese women had increased incidences of antepartum medical disease, prolonged cesarean section operation times, serious postoperative complications, and increased hospital stays. CONCLUSIONS: The high incidences of antepartum medical disease and emergency cesarean section complicate anesthetic care in the morbidly obese parturients. Epidural anesthesia is feasible; however, the high initial failure rate necessitates early catheter placement, critical block assessment and catheter replacement when indicated, and provision for alternative airway management.

Adult↗
PubMed1990

Fetal heart rate variability after epidural fentanyl during labor.

The effects of epidural fentanyl on fetal heart rate (FHR) were examined in 39 parturients, 19 given 75 micrograms epidural fentanyl and 20 given normal saline in 5-mL volumes administered randomly after establishment of adequate epidural lidocaine analgesia. Fetal heart rate was measured 15 min before and 15 min after lidocaine epidural analgesia, and for 60 min at 5-min intervals after administration of epidural fentanyl/placebo. A perinatologist blinded to the injected epidural solution analyzed FHR tracings. Epidural injections of fentanyl and saline, when given during established epidural lidocaine analgesia, were associated with equal reductions in FHR variability and the frequency of FHR accelerations (P less than 0.003). Neonatal outcome was also similar in both groups. The clinical significance, if any, of these moderate reductions in FHR during epidural lidocaine analgesia is unclear.

Adult↗
PubMed1990

Elective repeat cesarean section. Effect of anesthesia type on blood loss.

Halothane depresses uterine contractility and may increase cesarean blood loss during the use of general anesthesia. We retrospectively compared the medical records of 399 elective repeat cesarean section patients. We excluded medical and obstetric conditions that may predispose such patients to increased blood loss. Subsequent detailed record analysis included 84 patients receiving epidural anesthesia, 23 receiving halothane-supplemented nitrous oxide for general anesthesia and 14 receiving unsupplemented nitrous oxide for general anesthesia. No patient received a blood transfusion. The incidence of low postoperative hematocrits (less than 32%) following surgery was similar with all the anesthetic methods. Low-dose halothane supplementation of general anesthesia for elective cesarean section did not increase blood loss.

Adult↗
PubMed1988

Anesthesia for cesarean section: minimizing risk and complications.

Managing cesarean section anesthesia is challenging and fraught with hazards. Each anesthetic option has different maternal and fetal risks. Emphasis on regional anesthesia when possible and utilization of state-of-the-art monitoring such as pulse oximetry and end-tidal capnography will improve the anesthetic outcome.

Anesthesia, Epidural↗
PubMed1986

Maternal and fetal effects of epinephrine in gravid ewes.

Intravenous cannulation by an epidural catheter may complicate epidural anesthesia. Local anesthetic solutions containing epinephrine produce tachycardia and hypertension when given intravenously and may identify intravenous placement. The authors studied the maternal and fetal effects of intravenous epinephrine-containing solutions in ten chronically instrumented gravid ewes. While continuously monitoring maternal and fetal effects, epinephrine 5, 10, or 20 micrograms iv bolus was injected. Solutions of bupivacaine 5 mg and bupivacaine 5 mg combined with epinephrine 10 micrograms given iv were also examined. All epinephrine-containing solutions produced a significant increase (P less than 0.001) in maternal mean arterial pressure, which returned to baseline after 1 min. Maternal heart rates decreased transiently and returned to baseline after 1 min. All epinephrine-containing solutions decreased uterine blood flow (UBF) (P less than 0.001), and, for doses of 10 to 20 micrograms, this decrease lasted more than 3 min. Fetal heart rate and mean arterial blood pressure did not change following any test solution, nor did maternal or fetal arterial blood gas values. The authors conclude that small intravenous boluses of epinephrine decreased UBF in these animals.

Anesthesia, Epidural↗