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Biomedical subjects

R L Carpenter

Publications and source records attributed to R L Carpenter.

At least 55 records · Page 3Linked to original sources
PubMed1993

A randomized, double-blind evaluation of ketorolac tromethamine for postoperative analgesia in ambulatory surgery patients.

BACKGROUND: Given the trend toward early discharge of patients after surgery and the inherent adverse effects of opioid analgesics, we compared a new nonsteroidal antiinflammatory drug, ketorolac tromethamine, given intravenously (iv) and then orally, with two commonly prescribed opioid analgesics in ambulatory patients for up to 1 week after surgery. METHODS: In this study incorporating a double-blind, multi-dose design, 221 patients who had moderate or severe pain after surgery were randomized to one of three treatment groups: group K30 received 30 mg iv ketorolac twice, then 10 mg iv every 30 min as required to control pain, up to six doses, followed by 10 mg oral ketorolac every 4-6 h; group F50 received 50 micrograms iv fentanyl at the same time intervals as in group K30, followed by 60 mg codeine plus 600 mg acetaminophen (C+A) orally every 4-6 h; and group F10 received the same combination as did group F50, but only 10 micrograms fentanyl per dose. RESULTS: Compared with 50 micrograms fentanyl iv, 30 mg iv ketorolac provided delayed but otherwise equivalent analgesic effects and was associated with similar side effects. Compared with C+A, 10 mg oral ketorolac was associated with a lower incidence of nausea and somnolence and earlier return of bowel function but not better pain relief, drug tolerability, quality of life, or psychologic well-being. CONCLUSIONS: Ketorolac, when used in an iv and then oral sequence, is a safe and effective analgesic in the ambulatory surgery setting. It has a slower onset than fentanyl, but causes fewer side effects than C+A.

Administration, Oral↗
PubMed1993

Prolonged intrathecal fentanyl analgesia via 32-gauge catheters after thoracotomy.

We hypothesized that intrathecal fentanyl infusion would provide excellent analgesia, require lower doses than necessary for the epidural or intravenous route of administration, and reduce the incidence and/or severity of side effects. Accordingly, we studied 12 patients during 48 h after thoracotomy (three pneumonectomies, six lobectomies, and three multiple resections of metastases or pleural surgery). The mean dose of fentanyl infused intrathecally was 0.81 +/- 0.26 microgram.kg-1 x h-1, and plasma fentanyl concentrations ranged between 0.49 +/- 0.19 and 0.72 +/- 0.34 ng/ml. Four patients needed a supplementary bolus of intrathecal fentanyl. Pain scores decreased below 30/100 within 1 h when measured at rest but required 24 h to decrease to the same level during coughing. Pulmonary function tests returned to approximately 50% of preoperative values within 1 h of fentanyl infusion. Mean respiratory rates averaged 19 +/- 4, and no episode of apnea was detected. Pruritus, nausea, and headache occurred, respectively, in four, one, and zero patients. Excessive pressure in the infusion system occurred frequently, limiting fentanyl infusion in two patients. All catheters were removed intact; however, one broke outside of the patient's back. This study demonstrates that intrathecal fentanyl infusion can safely provide rapid and intense analgesia but that current 32-gauge intrathecal catheters are not well suited for prolonged postoperative use.

Adult↗
PubMed1992

Lidocaine 0.5% spinal anaesthesia: a hypobaric solution for short-stay perirectal surgery.

The efficacy of subarachnoid injection of 8 ml lidocaine 0.5% was assessed in ten outpatients having perirectal surgery in the jackknife position. This solution is hypobaric, with a baricity 0.9985 +/- 0.0003 (mean +/- SD). Injections were made with the patient in the surgical position (with the upper torso at a 15 degrees downward inclination). Sensory level was tested by pinprick. Times to two-segment regression, to complete resolution of sensory analgesia, to urination, and to discharge from the recovery room were recorded. All injections produced effective anaesthesia for surgery. Lidocaine 0.5% behaves clinically as a hypobaric solution. Dermatomal levels remained low (T11 to L5) while the patients were in the surgical position (head down), but rose two to six dermatomes if the patient's head was elevated after surgery. Time to two-segment regression was 97 +/- 36 min, time until regression to S1 was 116 +/- 22 min, time to complete resolution of sensory blockade was 151 +/- 23 min, time to urination was 197 +/- 64 min, and time to discharge from the recovery room was 205 +/- 45 min. Lidocaine 0.5% provides effective spinal anaesthesia of short duration appropriate for outpatient surgical procedures. Dermatomal sensory spread of anaesthesia, and our measurements of specific gravity, indicate that this solution is hypobaric. It appears that changes in position can alter the spread of analgesia for at least one hour after injection and, thus, we caution against elevating the patient's head in the immediate postoperative period.

Adult↗
PubMed1992

Incidence and risk factors for side effects of spinal anesthesia.

We prospectively studied 952 patients to identify the incidence of hypotension (systolic blood pressure less than 90 mmHg), bradycardia (heart rate less than 50 beats/min), nausea, vomiting, and dysrhythmia during spinal anesthesia. Historical, clinical, and physiologic data were correlated with the incidence of these side effects by univariate and multivariate analysis. Hypotension developed in 314 patients (33%), bradycardia in 125 (13%), nausea in 175 (18%), vomiting in 65 (7%), and dysrhythmia in 20 (2%). Variables conferring increased odds of developing hypotension include peak block height greater than or equal to T5 (odds ratio 3.8, P less than 0.001), age greater than or equal to 40 yr (2.5, P less than 0.001), baseline systolic blood pressure less than 120 mmHg (2.4, P less than 0.001), combination of spinal and general anesthesia (1.9, P = 0.01), spinal puncture at or above the L2-L3 interspace (1.8, P less than 0.001), and addition of phenylephrine to the local anesthetic (1.6, P = 0.02). Variables conferring increased odds of developing bradycardia include a baseline heart rate less than 60 beats/min (odds ratio 4.9, P less than 0.001), ASA physical status classification of 1 versus 3 or 4 (3.5, P less than 0.001), current therapy with beta-adrenergic blocking drugs (2.9, P less than 0.001), and peak block height greater than or equal to T5 (1.7, P = 0.02). Variables conferring increased odds of developing nausea or vomiting include addition of phenylephrine or epinephrine to the local anesthetic (3.0-6.3, P less than or equal to 0.003), peak block height greater than or equal to T5 (odds ratio 3.9, P less than 0.001), use of procaine (2.6-4.4, P less than or equal to 0.003), baseline heart rate greater than or equal to 60 beats/min (2.3, P = 0.03), history of carsickness (2.0, P = 0.01), and development of hypotension during spinal anesthesia (1.7, P = 0.009). Our results indicate that the incidence of side effects during spinal anesthesia may be reduced by 1) minimizing peak block height; 2) using plain solutions of local anesthetics; 3) performing the spinal puncture at or below the L3-L4 interspace; and 4) avoiding the use of procaine in the subarachnoid space.

Adult↗
PubMed1992

A randomized comparison of intravenous versus lumbar and thoracic epidural fentanyl for analgesia after thoracotomy.

Administration of large doses of fentanyl is a popular method to provide postoperative analgesia after thoracotomy. It is however unclear whether epidural lumbar (L) or epidural thoracic (T) administration of fentanyl confers any major advantage over intravenous (iv) infusion. Using a randomized prospective study design, we compared the potential benefits of L, T, and iv fentanyl administration after thoracotomy in 50 patients. Epidural catheters were not injected during surgery. Postoperatively a fentanyl infusion (5 micrograms/ml) was started at 1 microgram.kg-1.h-1 after a bolus of 1 microgram/kg and adjusted to maintain a score < or = 30/100 at rest using a visual analog scale (VAS) for pain. Data were prospectively collected before surgery, at fixed intervals during the 48 h of fentanyl infusions, and the day of discharge. There was no difference between the groups in overall quality of analgesia at rest and after coughing, quantity of fentanyl delivered (L = 1.15 +/- 0.38, T = 1.22 +/- 0.23, iv = 1.27 +/- 0.3 micrograms.kg-1.h-1), incidence of pruritus needing treatment (L = 2, T = 1, iv = 0 patients), need to decrease fentanyl infusion rate because of side effects (L = 2, T = 2, iv = 4 patients), importance of pulmonary infiltrates, or arterial blood gas values. One patient (L group) needed naloxone (0.04 mg iv). Intravenous patients were more frequently nauseated (P = .009) and needed boluses of fentanyl more often (L = 3 +/- 9, iv = 6 +/- 12, T = 4 +/- 8; P = .04).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

A prospective evaluation of the failure rate of spinal anaesthesia for transurethral prostatic resection.

The rate of failed spinal anaesthesia, defined as the need for unplanned general anaesthesia, was evaluated in a prospective study involving 137 patients undergoing transurethral resection of the prostate (TURP). The incidence of sensations at the operative site which did not require general anaesthesia was also evaluated. Attention to details was emphasized in the technique. Patients randomly received either hyperbaric Niphanoid tetracaine (n = 74; 6 or 10 mg) or hyperbaric bupivacaine (n = 61; 6 mg), with or without adrenaline. General anaesthesia was necessary in one patient (0.72%). Twelve additional patients reported sensations at the operative site which were rapidly relieved by light intravenous supplementation with low doses of fentanyl and/or thiopentone. The patients reporting sensations did not differ in demographic characteristics, spinal technique, local anaesthetic, or degree of sensory or motor blockade. Addition of adrenaline to the 6-mg doses of both tetracaine and bupivacaine decreased the incidence of sensations at the operative site.

Aged↗
PubMed1991

Vasoconstrictors in facial plastic surgery.

The effectiveness of local anesthetics is improved by the addition of a vasoconstrictor with an increased duration of action and the ability to decrease both systemic toxic reactions and local bleeding. Epinephrine, the standard drug for vasoconstriction, has some limitations due to potential cardiac and local toxic effects. Using an animal model, we compared the effects of various concentrations of epinephrine and two other vasoconstrictors, phenylephrine hydrochloride and felypressin, on local blood flow. We also examined the local effects of bupivacaine hydrochloride and ropivacaine hydrochloride, a new local anesthetic. We found that felypressin was as effective a vasoconstrictor as epinephrine, with fewer potential toxic reactions. Phenylephrine (Neo-Synephrine), on the other hand, was less effective, with a shorter duration of action. As expected, bupivacaine produced vasodilation, while ropivacaine was found to have vasoconstrictive properties.

Amides↗
PubMed1991

Age affects the pharmacokinetics of inhaled anesthetics in humans.

To define the effect of aging on the pharmacokinetics of volatile anesthetics, we determined the end-tidal and mixed expired anesthetic concentrations of isoflurane, enflurane, halothane, and methoxyflurane during 30 min of simultaneous administration and for 5-12 days of elimination in seven healthy young patients (31 +/- 1.8 yr [mean +/- SEM]) and in 11 healthy aged patients (73.2 +/- 3.1 yr [mean +/- SEM]). A five-compartment mammillary function was fit to the end-tidal and mixed expired anesthetic elimination data simultaneously using ordinary least-squares analysis. We assumed the compartments to represent the following tissue groups: lungs and pulmonary capillary blood (V1), vessel-rich tissues (i.e., liver, heart, kidneys, and brain) muscle, an unidentified fourth compartment, perhaps fat adjacent to well-perfused tissues, and fat tissues. The tissue volumes and perfusions estimated for these compartments approximated values from the literature. In general, the volume of the fourth and fifth compartments increased with age, and perfusion to the second and fifth compartments decreased with age. Aging delayed anesthetic elimination and increased the apparent volume of distribution at steady state. These observations are compatible with decreased tissue perfusion and an increase in the ratio of fat/lean body weight in the elderly. Our mammillary analysis described the behavior of less soluble anesthetics such as isoflurane well, but that of highly soluble anesthetics such as methoxyflurane less well.

Adipose Tissue↗
PubMed1990

Comparison of 0.5% ropivacaine and 0.5% bupivacaine for epidural anesthesia in patients undergoing lower-extremity surgery.

Ropivacaine is an amide local anesthetic structurally related to, but appearing less cardiotoxic, than bupivacaine. The authors' investigation was designed in a randomized, double-blind fashion to compare the clinical effectiveness of ropivacaine and bupivacaine in patients undergoing lower-extremity surgery. Forty-five patients were randomized to receive 20 ml of 0.5% ropivacaine or bupivacaine. Intermittent sensory (pinprick) and motor (Bromage score) measurements were made while the block was in effect, and changes in heart rate, blood pressure and amounts of additional analgesics, sedatives and other medications were also recorded. Presence of tourniquet pain and the quality of anesthesia were also assessed. One patient was excluded from analysis; thus, 22 patients each received ropivacaine or bupivacaine. No differences were found in patient or perioperative characteristics between the groups. The quality and extent of sensory and motor blockade between groups were comparable, although bupivacaine was slightly longer acting. Cardiovascular changes, incidence of tourniquet pain, and the amounts of supplemental medications necessary were also similar between groups. The authors found 0.5% ropivacaine and bupivacaine to be clinically similar in both sensory- and motor-blocking characteristics, with the exception that bupivacaine produced a blockade of slightly longer duration. Because ropivacaine is reported to be less cardiotoxic than bupivacaine in animal studies, the similarity of clinical epidural anesthesia may make ropivacaine the preferred agent.

Adolescent↗
PubMed1990

A comparison of conductivity-based hematocrit determinations with conventional laboratory methods in autologous blood transfusions.

An investigation was made of the accuracy of a portable hematocrit measurement device (Stat-Crit) on the infusate of an autologous blood transfusion system. Baseline hematocrit values were determined by three methods on in vivo blood samples of surgical patients immediately after the start of surgery, and again on the first product of the autologous blood retrieval system. At baseline, there were no significant differences in the values determined by the Stat-Crit (33.4% +/- 6.2%, mean +/- SD) and those determined by the microcentrifuge technique (33.8% +/- 4.7%) or by the Coulter method (33.5% +/- 4.5%) (P = 0.9). In contrast, hematocrit values determined on infusate samples by the Stat-Crit (36.6% +/- 4.8%) were significantly lower than those determined by the microcentrifuge technique (51.2% +/- 5.9%) or by the Coulter method (51.6% +/- 5.8%) (P = 0.0001). This study confirms close agreement of hematocrit values derived by the conductivity of whole blood in normal samples with those determined by conventional laboratory techniques, but indicates that this method will report falsely low readings in situations where plasma has been replaced by crystalloid, as in patients who have received large transfusions of processed autologous blood.

Blood Transfusion, Autologous↗
PubMed1990

Test doses: optimal epinephrine content with and without acute beta-adrenergic blockade.

The authors studied the optimal epinephrine content of an epidural test dose, and determined criteria to identify intravascular injections in subjects with or without beta-adrenergic blockade. Nine healthy nonpregnant subjects 25-36 years of age were given intravenous infusions of saline or esmolol in random order. During each infusion, they received a series of five injections (3 ml each) of either saline, 1% lidocaine or 1% lidocaine containing 5, 10, or 15 micrograms of epinephrine. Thirty minutes after completing these two infusions, propranolol was administered as a bolus injection, and the series of five injections repeated. All injections were double blind and randomized. During saline infusion, all injections containing epinephrine significantly increased heart rate (HR) by an average of 31-38 beats/min when compared with that following plain lidocaine (P less than 0.05), and increased systolic blood pressure by an average of 17-26 mmHg (P less than 0.05 for the 15-micrograms dose only). During esmolol infusion, epinephrine injections increased HR by an average of 23-31 beats/min (P less than 0.05), and increased systolic blood pressure by an average of 18-30 mmHg (P less than 0.05 for 10 and 15 micrograms). After propranolol injection, epinephrine injections caused a decrease in HR by an average of 21-28 beats/min (P less than 0.05), whereas systolic blood pressure increased by an average of 22-35 mmHg (P less than 0.05 for 10 and 15 micrograms only). Without beta-adrenergic blockade, an increase in HR greater than or equal to 20 beats/min was 100% sensitive and specific for intravascular injection of 10 or 15 micrograms of epinephrine.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1989

Talc deposition and effects after 20 days of repeated inhalation exposure of rats and mice to talc.

The relationship between the inhalation exposure concentration of talc and the resulting lung burdens and histologic lesions was studied using groups of 20 F344/Crl rats and 20 B6C3F mice (10 male and 10 female) exposed to one of three concentrations of asbestos-free talc for 6 hr/day, 5 days/week for 4 weeks. Controls were exposed to filtered air using the same schedule. The pulmonary retention of talc and the development of pulmonary pathology were evaluated. The mass median aerodynamic diameter (MMAD) of the talc aerosol was 3.0 microns with a geometric standard deviation (sigma g) of 1.9. The mean exposure concentrations for rats were 0, 2.3, 4.3, and 17 mg talc/m3. Lung burdens in rats averaged 0, 0.07, 0.17, and 0.72 mg talc/g lung after the 20-day inhalation exposure; thus, the amount retained in the lung per unit of exposure concentration increased with increasing concentration. Mean exposure concentrations for the mice were 0, 2.2, 5.7, and 20.4 mg of talc/m3, which resulted in lung burdens of 0, 0.10, 0.29, and 1.0 mg talc/g lung; thus, the relationship between exposure concentration and the amount retained in the lung was approximately constant. Lung burdens from this study were used to project lung burdens that would result from longer exposures of rodents and man. No clinical signs were observed in the rats or mice prior to sacrifice 24 hr after the last exposure day. Histologic alterations in lung tissue consisted of only a modest, diffuse increase of talc-containing, free macrophages within alveolar spaces in both rat and mouse groups exposed to the highest level of talc for 20 days. A model simulating chronic talc inhalation exposure of rats and mice predicted lung burdens of 2-3 mg talc/g lung (wet wt) if animals were exposed to 17 mg talc/m3 for 2 years, and deposition and clearance of talc were unchanged by continued exposure. A potential limitation in this modeling is that if clearance of talc is delayed by continued exposure, the accumulated talc lung burdens would be higher than those projected by the simulation model. Humans exposed to aerosols of respirable talc are projected to accumulate much higher lung burdens than would occur in rodents exposed to the same aerosol, because humans have a higher estimated deposition fraction and slower estimated clearance of the deposited talc dust. Equilibrium lung burdens of greater than or equal to 2 mg talc/g lung were predicted for human exposures at or near the TLV for talc.

Aerosols↗
PubMed1989

Effect of midazolam and diazepam premedication on central nervous system and cardiovascular toxicity of bupivacaine in pigs.

To determine the effect of benzodiazepine premedication on central nervous system and cardiovascular effects of bupivacaine, the authors administered toxic doses of bupivacaine to awake spontaneously breathing pigs after intravenous premedication with midazolam (0.06 mg/kg), diazepam (0.15 mg/kg), or saline. Five minutes after administration of one of these solutions, they began an infusion of bupivacaine at 2 mg.kg-1.min-1. The bupivacaine infusion was continued until cardiovascular collapse. They then attempted to resuscitate the animals via open chest cardiac massage and a standard resuscitation protocol. Premedication with midazolam or diazepam significantly delayed the onset of ventricular dysrhythmias (P less than 0.05), decreased the incidence of seizures (P less than 0.05), and prevented the increase in blood pressure and heart rate following bupivacaine infusion (P less than 0.05). Benzodiazepine premedication did not affect the dose of bupivacaine or the blood concentration required to produce cardiovascular collapse. The ability to resuscitate animals premedicated with midazolam did not differ from control; however, significantly fewer animals premedicated with diazepam were resuscitated (P less than 0.05). A clinically relevant observation was that almost all animals premedicated with a benzodiazepine progressed directly to cardiovascular collapse without first manifesting seizures.

Animals↗
PubMed1989

Alveolar-to-arterial-to-venous anesthetic partial pressure differences in humans.

To determine the correlation between the partial pressures of anesthetics in venous and arterial blood (Pv and Pa), and to assess whether this correlation was better than that between the partial pressure of anesthetic in alveolar gas (PA) and Pa, isoflurane (n = 4) or halothane (n = 4) was administered to eight patients undergoing surgery, and Pv, PA, and Pa were measured. PA correlated with Pa better than did Pv (R = 0.960 vs. 0.878), and there was less variability in the data. Differences between Pv and Pa increased as the relative blood flow to the hand decreased [indicated by an increasing arterial-to-venous (a-v) O2 content difference]. The difference between PA and Pa was approximately 20% of the difference between inspired gas (PI) and Pa. The differences between PA and Pa appear to be due primarily to contamination of alveolar gas by physiologic dead space gas.

Adult↗
PubMed1989

Epinephrine increases the effectiveness of tetracaine spinal anesthesia.

The effect of epinephrine on the need for supplementation of spinal anesthesia produced with hyperbaric tetracaine was assessed in 60 patients undergoing transurethral resection of the prostate. Patients were randomly assigned to receive either 6 mg tetracaine alone (n = 20), 6 mg tetracaine with 0.2 mg epinephrine (n = 20), 10 mg tetracaine alone (n = 10), or 10 mg tetracaine with 0.2 mg epinephrine (n = 10). Observers were blinded to the presence or absence of epinephrine. Sensory level of anesthesia was assessed by pin prick, and surgery did not start until the level reached T10. Anesthesia was considered successful if the patient had no pain at the operative site. The success rate of low-dose tetracaine (6 mg) with epinephrine was 95% compared with 65% in patients receiving low-dose tetracaine alone (P = 0.04). All patients receiving 10 mg had successful anesthesia. Compared with patients receiving 6 mg tetracaine, those given 10 mg had higher dermatomal levels of anesthesia (P = 0.0001) and a higher incidence of nausea (P = 0.04). Thus, epinephrine can increase the effectiveness of low-dose tetracaine.

Aged↗
PubMed1989

Effect of ropivacaine on cutaneous capillary blood flow in pigs.

The effect of subcutaneous infiltration of ropivacaine and bupivacaine on local cutaneous blood flow was assessed by the laser Doppler method. One milliliter of each of ten test solutions (ropivacaine 0.25% and 0.75%, bupivacaine 0.25% and 0.75%, and saline, each with and without added epinephrine 5 micrograms/ml) was injected subcutaneously at separate sites on the side of each pig (n = 6). Skin blood flow was measured by laser Doppler at all sites before and 5, 10, 15, and 30 min after injection. Subcutaneous injection of ropivacaine 0.25% or 0.75% decreased cutaneous blood flow by a maximum of 52% +/- 11% and 54% +/- 14% (mean +/- SE), respectively. In contrast, bupivacaine 0.25% or 0.75% increased flow by 90% +/- 32% and 82% +/- 48%, and injection of saline increased blood flow by 32% +/- 17%. Cutaneous blood flow after the injection of ropivacaine was significantly lower than after injection of bupivacaine or saline, and was also lower than at the uninjected control site (P = 0.0009). All of the solutions with epinephrine decreased blood flow to a similar extent (48-73%, P = 0.3). The ability of ropivacaine to produce cutaneous vasoconstriction offers several advantages over the other local anesthetics presently available for infiltration anesthesia.

Amides↗