Richard J. Palahniuk

Anesthesia for cesarean section: effects on neonates

The effects of general and regional anesthesia on neonates after cesarean section have been studied mainly on elective cases. In this paper we studied infants delivered by elective and nonelective cesarean section at the Winnipeg Womens Hospital from 1975 to 1983 (n = 3940) to determine the effect of anesthetic technique on neonatal outcomes. A trained anesthesia nurse interviewed all parturients and reviewed their antepartum, labor and delivery, and anesthesia records. Assessments of neonatal outcomes were based on 1− and 5-minute Apgar scores, need for positive pressure oxygen by mask or intubation, and neonatal deaths (within 30 days). These outcomes were determined in three subgroups of neonates delivered by cesarean section: those delivered by elective section, those delivered by urgent cesarean section for dystocia or failure of labor to progress, and those delivered by section because of fetal distress. Overall, 12.5% of the infants had 1-minute Apgar scores of 4 or less, and 1.4% had 5-minute Apgar scores of 4 or less. Neonates born to mothers given general anesthesia had worse outcomes than those born to mothers given regional anesthesia. Among neonates delivered after elective section, general anesthesia was associated with a higher incidence of low Apgar scores at 1 minute. In neonates delivered by nonelective section, general anesthesia was associated with higher rates of low Apgar scores at 1 and 5 minutes as well as greater requirements for intubation and artificial ventilation. There were no differences seen in neonatal death rates with general and regional anesthesia in the three groups. Using a multivariate analysis to control for differences among neonates with regard to maternal age, parity, presence of antepartum disease, labor complications, presence of fetal distress, gestational age, multiple birth, use of narcotics or sedatives during labor, elective versus nonelective section, and year of birth, the risk of poor neonatal outcome remained greater after general anesthesia than after regional anesthesia. We conclude that infants delivered by cesarean section under general anesthesia are more likely to be depressed and more likely to require active resuscitation than those delivered by cesarean section with regional anesthesia. However, with appropriate neonatal care, the choice of anesthetic technique does not appear to affect neonatal survival in the short term.

Effectiveness of preoperative sedation with rectal midazolam, ketamine, or their combination in young children

To determine which of three types of rectal sedation was most effective preoperatively in facilitating parental separation and intravenous cannulation in young children, 100 children 3.0 +/- 1.7 (mean +/- SD) yr of age were randomly assigned to four equal groups. One group (M-K-A) received rectal midazolam (0.5 mg/kg), ketamine (3 mg/kg), and atropine (0.02 mg/kg). The other sedation groups received the same doses of midazolam and atropine (M-A) or ketamine and atropine (K-A) alone, and the control group (A) received only rectal atropine. Most children in either the M-K-A (100%) or M-A (92%) groups separated easily from their parents without struggling or crying, significantly more than in the K-A (60%) or A (64%) groups. However, more children in the M-K-A group (44%) were asleep during separation than in the M-A group (8%; P < 0.05). Only 20% of the children in the M-A or M-K-A groups cried during intravenous catheter placement, significantly less than in the K-A (56%) or A (92%) groups. Intravenous catheter placement was also successful significantly more often in the M-A (80%) and M-K-A (84%) groups than in the K-A (48%) or A (40%) groups. Complications were similar among the groups, but there was evidence that midazolam prolonged recovery time in some patients. Rectal midazolam with or without ketamine is a useful technique when intravenous catheter placement before induction of anesthesia is desired.

High levels of carbon monoxide are produced by electro-cautery of tissue during laparoscopic cholecystectomy.

&NA; Pyrolysis of tissue in a hypoxic environment can produce carbon monoxide. The atmosphere of the peritoneal cavity is rendered hypoxic during laparoscopic cholecystectomy by insufflation with 100% carbon dioxide. To determine whether carbon monoxide is produced by electrocautery of tissue during laparoscopic cholecystectomy, nine patients undergoing this procedure had the insufflation gas after use of electrocautery analyzed for carbon monoxide. Blood was analyzed for carboxyhemoglobin in these same patients to determine whether carbon monoxide was being absorbed in dangerous amounts. Carbon monoxide was present in the peritoneal cavity 5 min after use of electrocautery was initiated at a median concentration of 345 ppm (range 25‐1600 ppm), and at the end of surgery at a concentration of 475 ppm (range 100‐1900 ppm). This was well in excess of the 35 ppm upper limit for a 1‐h exposure set by the Environmental Protection Agency. The carboxyhemoglobin concentrations (mean ± SD) were the same at the beginning (1.3% ± 0.7%), end (1.2% ± 0.7%), and the day after surgery (1.1% ± 0.6%). Although there was no evidence of significant absorption of carbon monoxide in these patients, care should be taken to scavenge the gases produced by cautery of tissues to avoid operating room contamination during laparoscopic surgery. (Anesth Analg 1993;77:338‐41)

The effect of heated wire circuits on humidification of inspired gases

We performed this study to determine the effect of heated wire circuits on humidity delivered by several humidifiers commonly used during anesthesia. Humidifier bases from three manufacturers with several humidifying chambers for each base were tested using both heated and unheated circuits. Delivered humidity and circuit temperature were measured at the distal end of the circuit. Each chamber was tested under both continuous flow (CF) and intermittent flow (IF) conditions. IF was provided by a Servo 900 B ventilator. Adjustments of flow and volume were made for pediatric chambers. At 90 L/m CF, humidifier performance was unsatisfactory with both heated and unheated circuits. At 15 and 45 L/m CF, both distal circuit temperature (EXIT) and humidity were within acceptable limits; unheated circuits delivered more humidity than heated circuits (P < 0.05). Relative humidity was lower at 45 L/m CF than at 15 L/m (P < 0.05). During IF while all chambers provided satisfactory humidity, humidity was greater when unheated circuits were used. We conclude that when heated circuits are used, humidifying systems may fail to deliver 100% humidity to patients.

Attempted organophosphate suicide : a unique cause of prolonged paralysis during electroconvulsive therapy

P lasma cholinesterase is synthesized in the liver, circulates in the plasma, and facilitates the metabolism of intermediate ester products formed during fatty acid metabolism (1). Because plasma cholinesterase is also vital in terminating the action of some drugs used during anesthesia (e.g., succinylcholine, mivacurium, chloroprocaine), its normal concentration and activity are of concern to the anesthesiologist. Organophosphate insecticides can produce irreversible inhibition of the activity of circulating plasma cholinesterase and result in prolonged respiratory paralysis after a normal tracheal intubating dose of succinylcholine (2). We were surprised recently by prolonged apnea in a young woman receiving anesthesia for electroconvulsive therapy (ECT) who, it was discovered later, had ingested an unknown quantity of DiazinonTM (Ortho Pharmaceuticals, Raritan, NJ) 20 days earlier.

Anesthetic Management of Infants Receiving an Adult Kidney Transplant

Renal transplantation in infants has been associated with a high incidence of acute tubular necrosis and of renal artery thrombosis. Since 1978, 24 infants who received an adult kidney transplant at the University of Minnesota have had aggressive administration of intravenous colloids to increase the central venous pressure to 16-20 mm Hg before renal reperfusion. Acute tubular necrosis developed in only two infants, and there were no cases of renal artery thrombosis. Chest radiographic evidence of pulmonary edema was present in the recovery room in seven patients (29%) and within the first four postoperative days in five patients (21%). Yet, only two infants (8.3%) required postoperative mechanical ventilation beyond 24 h to manage fluid overload. With aggressive intravenous colloid administration, infants in renal failure can receive an adult kidney transplant with a low incidence of active tubular necrosis or renal artery thrombosis, but pulmonary edema may develop requiring ventilatory support.

Maternal Halothane Anesthesia Reduces Cerebral Blood Flow in the Acidotic Sheep Fetus

Cerebrovascular autoregulation is lost during fetal asphyxia as cerebral vessels undergo compensatory vasodilation. In such a situation, maternal anesthetics, which decrease fetal arterial blood pressure and cardiac output, may further aggravate cerebral hypoxia. To examine this possibility, we prepared six pregnant ewes in such a manner as to be able to measure fetal regional cerebral blood flow in uteri during acidosis produced by partial umbilical cord compression both before and after 15 minutes of halothane anesthesia given to the mother.Umbilical cord compression in the absence of anesthesia caused fetal metabolic and respiratory acidosis as evidenced by a decrease in arterial pH from 7.34 to 7.05; fetal arterial oxygen saturation simultaneously decreased from 29 to 17%. Halothane anesthesia administered to the mother of the acidotic fetus caused further aggravation of fetal acidosis (arterial pH 6.85) and oxygen desideration (10%) and the fetus became markedly hypotensive.Blood flow to four cerebral areas increased 27 to 69% above control levels in the fetus during acidosis in the absence of maternal anesthesia but decreased to levels 30 to 42% below acidosis values when maternal anesthesia was combined with fetal acidosis. These data suggest that potent cardiovascular depressant anesthetics administered to the mother in the presence of fetal acidosis could decrease fetal cerebral oxygen delivery by interfering with fetal cardiovascular compensation during acidosis and reducing fetal cerebral blood flow.

Anesthetic management of a patient with severe cold agglutinin hemolytic anemia utilizing forced air warming

old agglutinins are autoantibodies, usually of the IgM type, that cause red blood cell aggluC tination at reduced temperatures. Cold agglutinins of low titer are usually of no clinical significance. However, in patients with cold hemagglutinin disease, agglutination, and subsequent hemolysis can occur within the normal temperature range (1,2). The morbidity and mortality from anesthetizing and performing surgery on patients with cold hemagglutinin disease are unknown in as much as it is a rare disorder and highly variable in terms of severity (3). However, cases of severe intravascular hemolysis from both intentional and unintentional perioperative hypothermia have been reported in patients with this disorder (4,5). In this report we describe the use of I) preoperative plasmapheresis and 2) intraoperative forced air convective warming to minimize hemolysis in a patient with severe cold agglutinin hemolytic anemia undergoing a splenectomy and cholecystectomy.

Is dantrolene safe to administer in sepsis? The effect of dantrolene after endotoxin administration in dogs and rats

Hyperthermia from septic shock may be indistinguishable from malignant hyperthermia. Dantrolene may be given in septicemia if the diagnosis is unclear. To determine if dantrolene is safe to use in sepsis, two studies were performed. In study 1, 18 anesthetized dogs in which profound septic shock was induced with 5 mg/kg of intravenous Escherichia coli endotoxin were randomized to receive (30 min later) intravenous injections of 10 mg/kg of dantrolene solution, the diluent of dantrolene, or maintenance intravenous fluids alone. The use of dantrolene solution and the diluent of dantrolene resulted in similar but transient statistically significant increases in the cardiac filling pressures and cardiac outputs and decreases in the vascular resistances compared with the control dogs. In a second study, 185 rats were randomized into five equal groups. Groups 1, 2, and 3 received 15 mg/kg of intraperitoneal Escherichia coli endotoxin followed 30 min later by 10 mg/kg of dantrolene solution, the diluent of dantrolene, or normal saline. Groups 4 and 5 received normal saline followed by dantrolene or normal saline. The survival of groups 1, 2, and 3 was less at 24 h (P < 0.0001) than that of either control group, but was not significantly different from one another. The results suggest dantrolene can be administered safely under clinical conditions where the cause of hyperthermia and shock cannot clearly be ascribed to malignant hyperthermia or septicemia.

Evaluation of the Augustine Guide™ for difficult tracheal intubation

Successful tracheal intubation with Augustine Guide ™ (Augustine Medical, Inc., Eden Prairie, MN) in patients with normal airways has recently been described. There are no studies describing Augustine Guide (AG) use in patients with difficult airways. Accordingly, we studied AG intubation in a population of patients with expected difficult airways due to cervical spine pathology, limited mouth opening, obesity, facial trauma or deformity due to previous operation or radiation and in patients with unexpectedly difficult airways. A total of 44 patients were studied. The AG was used as a primary intubating tool in patients with known difficult airways (n = 36) and as a secondary intubating tool in patients with unexpected inability to intubate using conventional direct laryngoscopy (n = 8). Airway difficulty was predicted by history and physical examination. Intubations were performed under general anaesthesia in 40 of the 44 patients studied. In four patients with predictably difficult airways, topical anaesthesia and sedation were used. Backup methods to achieve intubation were available. Thirty-two of the 36 with known or suspected difficult airways were classified as Mallampati Class III or IV. In the remaining eight patients the preoperative examination suggested an easy airway; however, after induction of general anaesthesia, their laryngeal inlet could not be seen using direct laryngoscopy. Using the AG, all were intubated successfully (36/44 at the first attempt, in 8/44 repositioning of the AG to allow successful laryngeal entry of the stylet was necessary). There were no failures or complications secondary to AG use. This study shows that the AG is a useful device for oral tracheal intubation in patients with known or unexpectedly difficult airways.RésuméLa réussite de l’intubation trachéale avec le dispositif d’Augustine (Augustine Guide™, Augustine Medical Inc. MN) chez des patients aux voies aériennes normales a été récemment rapportée. Il n’existe toutefois pas d’étude décrivant l’utilisation du guide d’Augustine (GA) chez des patients dont l’accès aux voies aériennes est difficile. Dans ce but, les auteurs ont évalué l’intubation avec le GA chez des patients dont les voies aériennes étaient présumées difficiles d’accès à cause de pathologies de la colonne cervicale, de limitations à l’ouverture de la bouche, d’obésité, de traumatismes faciaux ou de difformités dues à des interventions antérieures ou aux radiations ainsi que chez des patients non susceptibles de causer de difficultés. L’étude incluait 44 patients. Le GA a été utilisé comme instrument d’intubation principal chez 36 patients connus pour accès difficiles et comme instrument secondaire chez huit patients avec des difficultés imprévisibles d’accès sous laryngoscopie conventionnelle directe. Les difficultés d’accès aux voies aériennes ont été prédites par l’histoire et l’examen physique. Pour quatre patients chez qui des difficultés étaient prévues, l’anesthésie topique et la sédation ont été utilisées. Des méthodes de rechange étaient prévues en cas de besoin. Trente-deux des 36 patients pour lesquels l’accès difficile était connu ou suspecté étaient classifiés HI ou IV sur l’échelle de Mallampati. Chez les huit autres, l’examen préopératoire suggérait un accès facile; cependant, après l’induction de l’anesthésie générale, l’ouverture glottique n’a pu être visualisée sous laryngoscopie directe. Avec la GA, tous ont été intubés avec succès 06/44 au premier essai; chez 8/44, le GA a dû être replacé pour permettre l’introduction du mandrin dans le larynx). Il n’y a pas eu d’échecs ni de complications. Cette étude montre que le GA constitue un dispositif efficace pour l’intubation orotrachéale chez des patients dont l’accès difficile aux voies aériennes est auparavant connu ou inattendu.