Multi-center sestamibi parathyroid imaging study in Hawaii.

Technetium-99m (99mTc) sestamibi (MIBI) was first used as a parathyroid imaging agent in Hawaii in 1991. The purpose of this study was to determine the sensitivity and positive predictive value of the MIBI scan in detecting abnormal parathyroid glands. A retrospective, multi-center study from 1992-1994 involving 33 patients in four hospitals showed the overall sensitivity of the MIBI scan for detecting hyperparathyroid disease was 90%. The positive predictive value was 93%. It was more sensitive in detecting adenomas (95%) than hyperplasia (45%). In conclusion, the MIBI scan can be helpful in detecting abnormal parathyroid glands and may be most useful prior to reoperations for persistent and recurrent hyperparathyroidism.

Epidural anesthesia for obstetrics after spinal surgery.

The experience of 18 patients with previous spinal surgery who requested epidural anesthesia for obstetric pain was reviewed. Three received epidural anesthetics in two separate pregnancies, producing a total of 21 attempts at epidural anesthesia. All were initiated during labor and three were later extended for Cesarean delivery. Continuous lumbar epidural anesthesia was successfully established in 20 of 21 attempts. Ten were performed easily on the first attempt. There were excessive local anesthetic requirements and/or a patchy block for the remaining 11 attempts. The only complication that could be attributed to the attempts at epidural anesthesia was temporary low back pain in two patients with multiple attempts. No complications were noted on long-term follow-up. Our data, therefore, suggest that epidural anesthesia is safe and generally effective in obstetric patients with previous spinal surgery.

Oxygen transport and oxygen consumption in critically ill patients.

We performed a prospective study in 28 critically ill patients to document variations in oxygen consumption and oxygen transport that occur spontaneously, without any experimental interventions designed to change DO2. Each study consisted of from three to five sets of measurements, including thermal dilution cardiac output and blood gases. The interval between any two measurements ranged from 20 to 60 minutes. It was concluded that changes in VO2 and DO2 can occur spontaneously in patients with normal lactates, even when there are no experimental interventions. These spontaneous changes in VO2 and DO2 make it extremely difficult to interpret studies that demonstrate that VO2 is transport-limited. The changes in DO2 can likely be explained by changes in oxygen demand.

Epidural anaesthesia and thrombocytopenia.

A case is presented of a mother with unanticipated profound thrombocytopenia who received a continuous epidural anaesthetic for labour. No neurological sequelae or excessive bleeding occurred. It is clear, after a review of the literature, that more information is needed to define the lower limits of platelet count at which it is safe to proceed with epidural anaesthesia.

The epidural test dose in obstetrics: is it necessary?

One must distinguish between what is medically safe and what is legally safe. The authors have the impression that in order to be "legally safe" one must perform a test dose. This is despite the fact that it has not been conclusively shown that the use of test doses improve the safety margin of epidural anaesthesia, when administered by a competent person, with the proper resuscitative equipment immediately available. Until a controlled study is performed, test doses should be done for continuous epidural anaesthesia with the understanding that they are neither 100 per cent sensitive nor specific in preventing complications. It is however one more manoeuvre that may be useful in recognizing some of the patients with accidental subarachnoid placement of epidural catheters. The literature suggests that lidocaine 1.5 per cent in dextrose 7.5 per cent should be the test dose of choice in obstetric epidural anaesthesia in an amount known to produce spinal anaesthesia (30-50 mg). The use of epinephrine in test doses in unpremedicated healthy women in active labour is neither sensitive nor specific in signalling intravascular injection, and it may also be detrimental to fetal wellbeing. Epinephrine 15 micrograms as a test dose for intravenous injection appears to create more problems than it solves.

A comparison of two types of epidural catheters.

The purpose of this study was to compare two epidural catheters--the Portex epidural catheter and Vas-Cath catheter. One hundred and fifty patients in labour who received epidural anaesthesia were selected and either one or the other catheter was used, based on random assignment. Ease of insertion, maintenance and removal of the catheter were assessed, as was the incidence of blood return and paraesthesiae during epidural catheter insertion. There were no significant differences between the catheters as far as insertion, maintenance and removal were concerned. However, the incidence of paresthesiae was 44 per cent with the Portex and 24 per cent with Vas-Cath catheters (p less than 0.008). The incidence of blood vessel trauma was 12 per cent with the Portex and 6.7 per cent with the Vas-Cath catheter (p = NS). Choice of epidural catheter is a factor to be considered in minimizing the incidence of blood vessel trauma or paresthesiae.

A comparison of nalbuphine and meperidine in treatment of postoperative pain.

The analgesic efficacy and side effect profile of nalbuphine 20 mg IV and of nalbuphine 40 mg IV were compared to those of meperidine 75 mg IM in the immediate postoperative period. Pain intensity, pain relief, additional analgesic requirements and the overall acceptability of the treatment were recorded for 150 patients. No significant differences were found between the groups for any of the efficacy variables. Peak analgesic effects occurred at 15 minutes in both nalbuphine groups and at 30 minutes in the meperidine group. The mean time to additional analgesic medication was approximately 207 minutes in each group. The incidence of nausea and vomiting with meperidine was 22 per cent (95 per cent confidence interval 10 to 34 per cent) and with nalbuphine 20 mg the incidence was two per cent (95%CI -2 to 6 per cent). This difference was significant (p less than 0.01). The difference between nalbuphine 40 mg (10 per cent, 95%CI 1 to 19 per cent) and meperidine, was not considered statistically significant (p = 0.17). The analgesic efficacy of nalbuphine 20 mg was indistinguishable from that of nalbuphine 40 mg and from that of meperidine 75 mg. The significantly lower incidence of nausea and vomiting with nalbuphine is a major advantage for a recovery room analgesic.

Nalbuphine: a supplement to isoflurane and enflurane anaesthesia.

A retrospective study was carried out to review the intra-operative use of nalbuphine at the average dose of 1.5 mg/kg as a supplement to isoflurane and enflurane in balanced anaesthesia in 108 surgical patients. Intra-operative cardiovascular stability and the quality of emergence were examined. The amount of halogenated anaesthetic used was compared to the theoretical amount that would have been needed in the absence of nalbuphine. In 90% to 95% of patients, blood pressures remained within 20% of baseline for the duration of anaesthesia. At emergence, 80% of patients had no pain. Nalbuphine appeared to reduce halogenated anaesthetic requirements by approximately 50%. These promising results for the intraoperative use of nalbuphine need to be confirmed by controlled prospective studies.

Clarification of the effects of changes in P50 on oxygen transport.

In summary, a shift to the right in the O2-Hb curve in patients with anemia and decreased cardiac output and normal PaO2 will increase PvO2. This shift is mediated through increases in red cell 2,3-DPG. The stimulus for the increase in 2,3-DPG is most likely due to the decrease in SvO2. In hypoxemia caused by a decreased PAO2 (altitude), an increase in P50 may have no effect on PvO2 and in fact if the PaO2 is low enough, a left shift may increase the PvO2. Animals and man most successful at adapting to high altitudes reflect this fundamental physiological effect and have a left-shifted curve. This decrease in P50 is probably related to an intrinsic property of the hemoglobin and not to changes in 2,3-DPG. In hypoxemia caused by shunt, an increase in P50 increase the PvO2 regardless of the PaO2. Patients with congenital cyanotic heart disease have an increased P50 mediated through an increase in 2,3-DPG.

Continuous monitoring of mixed venous oxygen saturation in hemodynamically unstable patients.

A balloon-tipped catheter has recently become available which, when placed in the pulmonary artery, in addition to enabling the usual measurements of pulmonary arterial pressure, pulmonary capillary wedge pressure, and cardiac output by thermodilution, measures mixed venous oxygen saturation (SvO2) by spectrophotometry. Unlike the measurement of cardiac output by thermodilution, which is done intermittently, the continuous measurement of SvO2 is an effective method of monitoring hemodynamically unstable patients, since changes in cardiac output will immediately become apparent via a corresponding change in SvO2. This is of particular benefit in patients in whom knowledge of the immediate effects of therapy is important. It is also of value in assessing the time of onset of action and duration of action when a cardioactive drug is given to increase cardiac output. We suggest that monitoring SvO2 will provide an earlier indication of the effect of both diagnostic and therapeutic interventions and, therefore, will improve our management in such patients.

Epidural morphine for analgesia after caesarean section.

A randomized double blind placebo controlled study of the efficacy, duration and safety of epidural morphine for the management of pain after Cesarean section is reported. Three similar groups of patients received either 0, 4 mg or 8 mg of morphine sulphate in 10 ml of normal saline through an epidural catheter at the completion of the operation. Compared to the saline controls, both the 4 mg and 8 mg epidural morphine groups had significant pain relief as judged by an analogue pain scale (p less than 0.001), the time to the first administration of narcotic analgesics (p less than 0.001) and the amount of supplemental analgesic required in the first 36 hours after operation (p less than 0.001). The side effects occurred in a dose-dependent fashion. Two patients who received epidural morphine 8 mg plus additional narcotic or antihistamine had reduced respiratory rates but were easily rousable. Our experience suggests that the epidural administration of morphine 4 mg may be a safe and reliable method of obtaining prolonged analgesia following Caesarean section.