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Biomedical subjects

A S Wheeler

Publications and source records attributed to A S Wheeler.

At least 19 recordsLinked to original sources
PubMed1986

Effects of preoperative medications on gastric pH, volume, and flora.

Aspiration of acid gastric juice poses a potential threat during operations. Many anesthesiologists use a variety of agents aimed at decreasing gastric volume and/or acidity. The effect of three agents on gastric volume, pH, and flora, and the effect of cefazolin on gastric flora in morbidly obese patients were studied. Cefazolin did not sterilize the gastric lumen. Almost one-half of patients not treated with an H2 blocker had a pH below 2.5 and a gastric volume of 20 ml or more. Five had both a low pH and significant volume and, thus, the potential for lethal aspiration. Two doses of cimetidine, 300 mgm orally, or of ranitidine, 150 orally, the evening before and the morning of operation decreased gastric volume and raised pH reliably to a level that should be protective from fatal aspiration. However, gastric cultures after these drugs were positive 86% of the time with a larger variety of organisms than in the untreated stomachs. Metoclopramide failed to decrease gastric volume or raise pH. Transoperative cefazolin was used in all patients. Clinical infection was not a problem.

Anti-Bacterial Agents↗
PubMed1984

Anesthesia for obstetric emergencies.

Anesthesia in an emergency presents an additional risk to the mother and may have some possibly harmful effects on the stressed fetus. The risk to the mother can be reduced by using regional anesthesia, whenever reasonable, and by taking measures to minimize the risk of aspiration of vomitus. The stressed fetus can be assisted, if not by a rapid delivery, by giving the mother oxygen to oxygenate the fetus and possibly by improving intervillous perfusion with a regional anesthetic.

Anesthesia, Obstetrical↗
PubMed1982

Sodium citrate premedication in elective caesarean section patients.

The pH and volume of gastric contents from thirty-three patients undergoing elective caesarean section with thiopentone, nitrous oxide, succinylcholine anaesthesia were examined. Twenty patients received Gelusil 30 ml by mouth and thirteen patients received 30 ml of a 0.15 molar solution of sodium citrate. Following tracheal intubation, gastric fluid was sampled through an 18 French Salem sump tube place orally. Mean pH following Gelusil was 4.54 +/- 2.45 (SD) and 2.29 +/- 1.77 following sodium citrate. This difference was statistically different (P less than 0.05). There was no difference in gastric volume between the two groups. Thirty five per cent of patients receiving Gelusil had a pH less than 2.5. This low pH was more likely to occur with prolonged intervals between drug administration and sampling. Significantly more patients receiving sodium citrate had a low pH (85 per cent) and this low pH was not related to the duration of interval between administration and sampling. This study demonstrates that 30 ml of 0.15 molar sodium citrate is not a satisfactory alternative to 30 ml of Gelusil for increasing gastric pH in the paturient when given sixty minutes before operation.

Adult↗
PubMed1982

Antacid anticholinergic regimens in patients undergoing elective caesarean section.

The pH and volume of gastric contents were examined in 60 patients undergoing elective Caesarean Section under thiopentone, nitrous oxide-oxygen, succinylcholine anaesthesia. All patients received Gelusil 30 ml per os preoperatively, while 20 were given atropine 7 microgram X kg-1 and another 20 glycopyrrolate 4 microgram X kg-1 intramuscularly along with Gelusil. Following tracheal intubation, gastric fluid was sampled through an orally placed 18 French Salem Sump tube. After Gelusil alone, the mean gastric fluid pH was 4.54 +/- 2.45 (SD) while it was significantly higher following the combined use of antacid and atropine (6.78 +/- 1.20) or antacid and glycopyrrolate (6.42 +/- 1.72), (P less than 0.01). Differences in gastric fluid volume between the groups were insignificant. All three regimens produced a gastric pH greater than 2.5 when given less than 75 minutes before sampling. When the premedication to sampling interval exceeded 75 minutes the addition of atropine or glycopyrrolate decreased the incidence of gastric pH less than 2.5 from 47 per cent in patients given Gelusil alone to 6 per cent and 14 per cent, respectively. In comparison to Gelusil alone, this difference was significant with atropine (P less than 0.05) but not with glycopyrrolate. Atropine and glycopyrrolate respectively produced 6 per cent and 7 per cent incidences of pH lower than 2.5 combined with gastric volume greater than 25 ml, which were significantly lower than was observed with Gelusil alone (P less than 0.05). This study demonstrates that the addition of atropine or glycopyrrolate to Gelusil premedication provides additional protection against the consequences of aspiration, especially when the premedication to anaesthetic induction period is prolonged.

Adult↗
PubMed1982

Anesthesia for pregnancy-induced hypertension.

Women with severe pregnancy-induced hypertension are often critically ill; their fetuses are usually compromised. An ideal anesthetic method does not exist for the parturient with severe hypertension, hypovolemia, and organ failure. Optimal anesthetic results depend upon thorough preanesthetic evaluation and best medical control of pathophysiology, regardless of the technique employed for vaginal or cesarean delivery. The anesthesia team must be consulted early, communicate freely and effectively with other perinatal team members, and have extensive knowledge of the pathophysiology involved. Time must be allowed for preparation of necessary monitoring and anesthetic facilities. In patients under good medical control, judiciously administered continuous epidural block is the better approach for labor, vaginal delivery, or cesarean section.

Anesthesia, Obstetrical↗
PubMed1981

Single dose carbenicillin versus T-tube drainage in patients undergoing vaginal hysterectomy.

In this study, a prospective, randomized, non-blinded report, single dose carbenicillin prophylaxis preoperatively is compared with T-tube suction drainage postoperatively in 50 patients undergoing vaginal hysterectomy. A higher incidence of febrile morbidity, fever index units, cellulitis of the vaginal cuff and prolonged hospitalization postoperatively was experienced by the group patients with T-tube suction drainage, P less than 0.05. Our satisfactory results with single dose carbenicillin prophylaxis preoperatively are similar to those of previous studies using more extended antibiotic prophylaxis perioperatively.

Adult↗
PubMed1980

Vascular and uterine responses to dobutamine and dopamine in the gravid ewe.

Dopamine, a naturally occurring catecholamine precursor of norepinephrine, has been used in the treatment of cardiogenic shock. Following intravenous administation it increases cardiac output, blood pressure, and renal blood flow. Dobutamine is a directly acting inotropic agent which increases myocardial contractility without significantly changing blood pressure. This study was devised to compare the effects of these two drugs on uterine blood flow (UBF), uterine tonus (UT), mean arterial blood pressure (MAP), and heart rate (HR). Chronically instrumented pregnant ewes near term were infused with differet concentrations of dopamine and dobutamine while HR, MAP, UT and UBF were recorded continuously. Dopamine produced a decrease in UBF and an increase in MAP and UT while the HR response was variable. Dobutamine administration resulted in a marked increase in HR and a decrease in UBF, while MAP and UT remained essentially unchanged. Uterine vascular resistance increased with both drugs during high-dosage administration, but the rise was more pronounced following dopamine infusion. Since dobutamine exhibits less alpha-adrenergic activity than dopamine this drug would seem to be preferred when an inotropic agent is required for treatment of the pregnant patient.

Animals↗
PubMed1980

Effects of nitroglycerin and nitroprusside on the uterine vasculature of gravid ewes.

The effects of nitroglycerin (TNG) and sodium nitroprusside (SNP) on mean aortic pressure (MAP), uterine blood flow (UBF), uterine vascular conductance (UVC), and pulse rate (PR) were compared when the two agents were infused to prevent and treat hypertension induced by norepinephrine (NE) in gravid ewes. When infused alone, TNG, 19 microgram/kg/min, decreased MAP 19 per cent and increased PR 33 per cent from control values (P less than 0.05), but did not significantly change UBF or UVC. In comparison, SNP, 3 microgram/kg/min, decreased MAP 20 per cent and increased PR 43 per cent (P less than 0.05), and did not significantly change UBF or UVC. When given alone, four successive 2-min infusions of NE produced dose-related increase in MAP and decreases in UBF, UVC, and PR; values were significantly different from control with the two higher doses of NE. Although MAP, UBF, and UVC were still significantly changed from control levels when NE was given in the presence of the above infusions of TNG or SNP, MAP was lower and UBF and UVC were higher compared with when NE was given alone (P less than 0.05). When given to control hypertension induced by a continuous infusion of NE, TNG or SNP produced uterine vasodilatation and significantly increased UBF. Nitroglycerin and SNP were equally effective in counteracting the maternal hypertension and antagonizing the uterine vascular effect of NE. It is concluded that TNG and SNP counteract uterine vasoconstriction resulting from alpha-adrenergic stimulation and do not produce a shunt of blood flow away from the uterine vasculature when used to control hypertension in gravid ewes.

Animals↗
PubMed1980

Chloroprocaine vs. bupivacaine for lumbar epidural analgesia for elective cesarean section.

The incidence and degree of hypotension, time to establish surgical analgesia, and several other maternal and fetal variables were studied when 2-chloroprocaine, 3 per cent, and bupivacaine, 0.5 per cent, were used for epidural analgesia in 30 women undergoing elective cesarean section. Surgical analgesia occurred 8 min sooner (P less than 0.001) with chloroprocaine (14 +/- 1 min) than with bupivacaine (22 +/- 2 min). Blood pressure values were significantly lower with chloroprocaine than with bupivacaine during the 18--to-32 min interval after local anesthetic injection, while pulse rates were higher (P less than 0.05) at 18, 20, and 22 min. Hypotension necessitating treatment with ephedrine occurred in 33 per cent of chloroprocaine-treated subjects, compared with 13 per cent of those receiving bupivacaine. Newborn outcome was excellent in both groups, as reflected by umbilical vessel blood-gas values, times to sustained respiration, and 5-min Apgar scores. The authors conclude that chloroprocaine disturbs maternal cardiovascular status more than does bupivacaine when used for cesarean section epidural analgesia. However, chloroprocaine can be employed safely in normal pregnancies if maternal hypotension is corrected rapidly.

Analgesia↗