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Biomedical subjects

W Camann

Publications and source records attributed to W Camann.

29 records · Page 2Linked to original sources
PubMed1995

Clinical effects and maternal and fetal plasma concentrations of epidural ropivacaine versus bupivacaine for cesarean section.

BACKGROUND: Ropivacaine is a new amide local anesthetic structurally similar to bupivacaine and mepivacaine. Previous studies showed that ropivacaine has a similar clinical effect as bupivacaine with regard to sensory anesthesia and slightly less motor blockade than bupivacaine. Ropivacaine appears to be less cardiotoxic and arrhythmogenic than bupivacaine. The clinical and pharmacokinetic effects of 0.5% ropivacaine (5 mg/ml) versus 0.5% bupivacaine (5 mg/ml) when used epidurally for elective cesarean section were investigated. METHODS: Using a randomized, double-blind study design, 60 ASA physical status 1 or 2 term parturients presenting for elective cesarean section received either 0.5% bupivacaine (150 mg) or 0.5% ropivacaine (150 mg) epidurally in appropriate fractionated doses over a 10-min period. Onset, duration, and regression of sensory and motor blockade were noted until complete resolution was observed. Quality of intraoperative anesthesia and abdominal wall muscle relaxation were noted. Maternal plasma concentrations of local anesthetic were determined before anesthetic administration and 5, 10, 20, 30, and 60 min and 2, 3, 6, 8, 12, and 24 h after drug injection in 20 subjects. Umbilical cord blood was obtained at time of delivery for acid-base values and determination of the free and total plasma concentration of local anesthetic. Neonates also were examined for neurobehavioral assessments by Scanlon's and Neurologic and Adaptive Capacity Scores at 2 and 24 h after delivery. RESULTS: All patients received satisfactory anesthesia for operation. The onset, duration, and regression of sensory blockade were similar for both groups. Onset of degree 1 and 2 motor blockade was faster, and duration of degree 1 motor block was longer in the group receiving bupivacaine. Hemodynamic sequelae were similar between groups. All neonates had 5-min Apgar scores of 7 or greater and normal acid-base values and neurobehavioral assessments. Pharmacokinetic analysis showed that the Cmax was similar for both drugs (1.3 +/- 0.09 for ropivacaine and 1.1 +/- 0.09 micrograms/ml for bupivacaine). The T1/2 of the terminal decline in plasma concentration was shorter for ropivacaine versus bupivacaine (5.2 +/- 0.60 versus 10.9 +/- 1.08 h, respectively; P < 0.01). The free (i.e., unbound) concentrations of ropivacaine were approximately twice those of bupivacaine in both maternal and neonatal blood at the time of delivery. The ratio of umbilical vein to maternal vein concentration of unbound drug was 0.72 for ropivacaine and 0.69 for bupivacaine. CONCLUSIONS: Ropivacaine, 0.5%, epidurally provided satisfactory and similar sensory anesthesia compared to 0.5% bupivacaine for elective cesarean section. The Cmax was similar for both drugs, although the terminal half-life of ropivacaine was significantly shorter, and the blood concentrations of free ropivacaine were significantly greater than that for bupivacaine. These values were less than concentrations shown to be toxic in animals.

Adolescent↗
PubMed1994

Combined spinal-epidural analgesia in advanced labour.

The combined spinal-epidural technique is a modification of epidural analgesia which combines the rapid onset of spinal analgesia with the flexibility of an epidural catheter. We sought to evaluate the effectiveness of an intrathecal opioid--low-dose local anaesthetic combination for parturients in advanced labour, a setting where satisfactory epidural analgesia is often difficult to achieve. The technique was evaluated in an open-label, non-randomized trial using parturients in advanced, active labour for the provision of pain relief during the late first stage and second stage of labour. Thirty-eight term parturients in active, advanced labour received a spinal injection of bupivacaine 2.5 mg and sufentanil, 10 micrograms, via a 25- or 27-gauge Whitacre needle placed into the subarachnoid space through a 17- or 18-gauge Weiss epidural needle which had been placed into the epidural space. This was followed by placement of an epidural catheter for supplemental analgesia if required. Onset of analgesia was noted by asking patients if their contractions were comfortable. Motor blockade was assessed using the Bromage criteria. Patients were asked if they experienced either pruritus or nausea on a four-point scale (none, mild, moderate, severe). The mean cervical dilatation at placement of the spinal medication was 6.1 +/- 2.2 cm. Thirty-two patients had spontaneous vaginal delivery, two were delivered by outlet forceps, and four by Caesarean section. Onset of analgesia was rapid (< five minutes) in all cases. Twenty-three patients (60%) delivered vaginally with no additional anaesthetic. The remaining 15 had supplemental local anaesthetic given via the epidural catheter, a mean of 123 +/- 33 min after the original spinal dose.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Continuous arterial and venous blood gas monitoring during cardiopulmonary bypass.

A new monitoring technique, based on optical fluorescence chemistry, allows continuous monitoring of all blood gas variables during cardiopulmonary bypass. To evaluate the clinical performance of this monitor, we drew 220 arterial and 216 venous blood samples from 15 patients, and simultaneous blood gas values displayed by the monitor were compared with standard laboratory measurements. The continuous monitor predicted laboratory values with varying degrees of accuracy. (R2 values by linear regression: arterial oxygen tension 0.86, venous oxygen tension 0.36, arterial carbon dioxide tension 0.58, venous carbon dioxide tension 0.72, arterial pH 0.53, venous pH 0.58; pH 0.53, venous pH 0.58; p less than 0.0001). Monitor values of arterial oxygen tension overestimated laboratory values (bias = + 43.5 mm Hg), but the laboratory reference method likely underestimated true arterial oxygen tension in the high range achieved on bypass. Monitoring of venous oxygen tension was imprecise (precision = +/- 6.51 mmHg), regardless of whether stable conditions existed during the sampling period. Monitoring of carbon dioxide tension and pH showed small bias (carbon dioxide tension within 2 mm Hg, pH within 0.03) and good precision (carbon dioxide tension within 3 mm Hg, pH within 0.03). With the development of unstable conditions on bypass, monitor arterial oxygen tension values showed a changing relationship to corresponding laboratory values. In conclusion, arterial and venous carbon dioxide tension and pH monitoring provide acceptably accurate alternatives to laboratory measurement of these variables during cardiopulmonary bypass. Arterial oxygen tension monitoring accurately indicates changes in oxygen tension in the arterial oxygen tension range typically produced during extracorporeal circulation. Oxygen tension monitoring in the venous oxygen tension range is too imprecise for clinical decision-making purposes.

Aged↗
PubMedDate not supplied

Intrathecal sufentanil and epidural bupivacaine for labor analgesia: dose-response of individual agents and in combination.

BACKGROUNDS AND OBJECTIVES: Combinations of local anesthetics and opioids are frequently used during spinal and epidural analgesia for the relief of labor pain. This combination allows for a dose-sparing effect which may reduce potential side effects or toxicity. The precise nature of the interaction between opioids and local anesthetics in the clinical setting, i.e., additivity versus synergism, has not been established. This trial was designed to utilize a validated technique of analysis of drug interactions, isobolography, to investigate this interaction. METHODS: One hundred healthy laboring patients at term receiving a combined spinal and epidural technique were divided into nine groups as follows: intrathecal sufentanil 2, 5, or 10 microg (2 mL volume) and epidural saline (10 mL); epidural bupivacaine 5, 12.5, or 25 mg and intrathecal saline (2 mL volume); or combination of l, 2.5, and 5 microg intrathecal sufentanil plus 2.5, 6.25, or 12.5 mg epidural bupivacaine, using similar volumes, respectively. All drugs were administered in a randomized, double-blind fashion. Pain relief scores were assessed 20 minutes after drug injection, and isobolographic analysis was utilized to determine the nature of the interaction. RESULTS: The ED50 of intrathecal sufentanil alone was 2.3 microg (95% CI 1.7-3.2), and the ED50 for epidural bupivacaine was 24 mg (95% CI 12-50). The combined sufentanil and bupivacaine fractional dose ED50 (in fractions of the single-dose ED50 values) was found to be approximately one-third and one-tenth of the single drug fractional dose, respectively: sufentanil 0.85 microg (0.36) and bupivacaine 2.2 mg (0.09). The duration of analgesia was nearly equivalent in all sufentanil-alone groups (83, 102, and 99 minutes); a dose-response effect was more apparent in the bupivacaine group (35, 42, and 74 minutes; P = .006) and the combination group (60, 79, 101 minutes; P = .028). Isobolography showed the combination dose to lie well within the area of synergism; however, the 95% confidence limits cross the line of additivity thus a pure additive interaction cannot be excluded. CONCLUSIONS: Markedly reduced doses of these drugs in combination can be used to provide adequate analgesia during labor compared with either single drug alone.

Adult↗