Basil C. Leiman

The Effects of Oral Transmucosal Fentanyl Citrate Premedication on Preoperative Behavioral Responses and Gastric Volume and Acidity in Children

The authors compared the safety, efficacy, and effects on gastric volume and pH of oral transmucosal fentanyl citrate (OTFC) premedication and of placebo lollipop and no premedication in 55 children undergoing elective operations. The patients were randomly assigned to receive no premedication (group A, N = 18); OTFC containing 15–20 μg/kg of fentanyl citrate (group B, N = 18); or a placebo lollipop (group C, N = 19). Activity (sedation) and anxiety scores, vital signs (including systolic and diastolic arterial blood pressures, heart and respiratory rates), and pulse oximetry determined oxygen saturation were measured before and at 10-min intervals after premedication until the patients were taken to the operating room. Gastric contents were aspirated via an orogastric tube and analyzed for volume and pH after induction of anesthesia. Quality of induction and recovery were evaluated using scoring schedules; recovery times were measured and side effects recorded. OTFC was readily accepted and provided levels of sedation and anxiolysis significantly greater after 10 min than after no premedication or the placebo lollipop. Arterial blood pressures, heart rate, and oxygen saturations were not different among the three groups. In patients given OTFC, respiratory rates were significantly lower after 10 min than they were in patients having no premedication. When compared to patients having no premedication, patients having OTFC had slightly increased gastric volumes (14.6 ± 10 vs 7.6 ± 5.3 mL, mean ± SD). Patients having a placebo lollipop had similar gastric volumes (15.6 ± 13.5 mL) as those having OTFC. The three groups had similar gastric pHs (1.69 ± 0.31, 1.92 ± 0.53 and 1.72 ± 0.28, mean ± SD, groups A, B, and C, respectively). Induction and recovery evaluations and recovery times were also similar in the three groups. OTFC was associated with a 50% incidence of mild, nondisturbing, preoperative facial pruritus and a higher overall incidence of postoperative nausea (44%) than was premedication with the placebo lollipop (16%) or no premedication (0%). The results demonstrate that OTFC is readily accepted, safe, and more effective than no premedication or premedication with a placebo lollipop, and does not affect gastric pH but does increase gastric volume.

Anaesthesia for the achondroplastic dwarf

Abstract MissingOver the past three years, 36 anaesthetics were administered to 27 patients with achondroplastic dwarfism. Twenty-four patients underwent craniectomy for foramen magnum stenosis. Sixteen of the operations were undertaken in the sitting position with nine incidents of venous air embolism (VAE), all of which occurred in patients under 12 years of age.Six major complications occurred: two C-1 level spinal cord infarctions, two brachial plexus palsies, one severe macroglossia, and one accidental extubation.Intravenous access in the small child with achondroplastic dwarfism is made difficult because of the excess, lax skin and subcutaneous tissue.Airway management and laryngoscopy were not difficult and we found that endotracheal tube size was best predicted by the patients weight and not age.Blood loss was 38±9 mg·kg−1 in the prone position (n = 8) and 18±4 mg·kg−1 in the sitting position (n = 16), and was related to the surgical procedure rather than to dwarfism.Our data indicate that complications are more likely to occur in the sitting position, and that these complications are of a serious nature, and every precaution should be taken to avoid their occurrence.RésuméAu cours de trois dernières années, 36 anesthésies ont été administrées à 27 patients atteint nanisme achondro-plasique. Vingt quatre patients ont subi une crdniectomie pour sténose du foramen occipital. Seize de ces opérations ont été accomplies dans une position assise avec neuf incidents d’embolies gazeuse, tous survenant chez des patients dgés de moins de 12 ans.Six complications majeures sont survenues: deux infarcisment de la moelle épinière au niveau de C-1, deux plexus brachial, une macroglossie sévère, et une extuba-tion accidentelle.L’accès intraveineux du patient avec un nanisme achondroplasique est difficile é cause de I’excès de peau et de tissus sous-cutané.La conduite de maintien des voies aériennes et la laryngoscopie riétaient pas difficile et on a trouvé que la grosseur du tube endotrachéal est mieux prédite par le poids du patient plûtot que son ôge. Les pertes sanguines ont été de 38 ± 9ml.kg-1 en position couchie (n = 8) et 18 ±4 ml.kg-1 en position assise (n = 16), et était en relation avec la position chirurgicale plutôt qu’au nanisme. Nos données indiquent que les complications surviennent plus fréquemment en position assise celles ci sont dangeureuses et toutes les précautions doivent étre prises afin d’éviter leur survenue.

Effect of the Trendelenburg Position on the Distribution of Arterial Air Emboli in Dogs

We examined the effects of buoyancy on the distribution of arterial gas bubbles using in vitro and in vivo techniques in dogs. A simulated carotid artery preparation was used to determine the effects of bubble size and vessel angle on the velocity and direction of bubble movement in flowing blood. Because buoyancy tends to float bubbles away from dependent areas, bubble velocity would be expected to decrease as the vessel angle increased. We found that larger bubbles increased in velocity in the same direction as the blood flow at 0-, 10-, and 30-degree vessel angles and decreased when the vessel was positioned at 90 degrees. Smaller bubbles did not change velocity from 0 to 30 degrees and increased in velocity in the same direction as blood flow at 90 degrees. In 10 anesthetized dogs, we studied the effects of 0-, 10-, 15-, and 30-degree Trendelenburgs position on carotid artery distribution of gas bubbles injected into the left ventricle or ascending aorta. Regardless of the degree of the Trendelenburg position, the bubbles passed into the carotid artery simultaneously with passage into the abdominal aorta. We conclude that the forces of buoyancy do not overcome the force of arterial blood flow and that the Trendelenburg position does not prevent arterial bubbles from reaching the brain.

Mechanisms of succinylcholine-induced arrhythmias in hypoxic or hypoxic: hypercarbic dogs

To evaluate the effects of succinylcholine on cardiac arrhythmias and serum levels of potassium and catecholamincs, dogs with hypoxia alone and with hypoxia and hypercarbia were studied during anesthesia with halothane or enflurane. After the injection of succinylcholine (0.3 mg/kg), cardiac arrhythmias occurred in all halothane:hypoxia dogs and in 70% of dogs given halothane during hypoxia:hypercarbia. No dogs given enflurane anesthesia developed arrhythmias. Serum potassium levels increased significantly 3 and 5 min after succinylcholine in all groups. Serum epinephrine levels increased in the halothane-hypoxia:hypercarbia and enflurane:hypoxia groups and, after the injection of succinylcholine, epinephrine levels increased further in dogs in the halothanexontrol, halothane:hypoxia, halothane-hypoxia:hypercarbia, enflurane:hypoxia, and enflurane-hypoxia:hypercarbia groups. Norepinephrine levels increased with enflurane-hypoxia:hypercarbia and after the succinylcholine in the halothane:hypoxia, halothane-hypoxia:hypercarbia, and enflurane-hypoxia:hypercarbia groups. The results suggest that succinylcholine induces arrhythmias by sympathetic stimulation and that halothane sensitizes the myocardium to arrhythmias at the same levels of serum catecholamines and potassium in the presence of hypoxia or hypoxia:hypercarbia more than does enflurane.

Arterial air embolism of venous origin in dogs: effect of nitrous oxide in combination with halothane and pentobarbitone

The effects of using nitrous oxide (N2O) with halothane or pentobarbitone anaesthesia on the filtration of venous air emboli (VAE) by the pulmonary circulation were studied in dogs. Dogs anaesthetized with either pentobarbitone, pentobarbitonelN2O, halothane, or halothanelN2O were embolized with venous air into the right atrium at 0.25 to 0.35 ml-kg-1 min-1 for 30 min. The animals were in a supine, head down position. A Doppler ultrasonic probe located over the suprarenal aorta detected arterial bubbles that escaped filtration by the lungs. No bubbles were detected at 0.25 ml.kg-1min-1,but at 0.30ml.kg-1.min-1 the incidence was 11 per cent (pentobarbitone), 0 per cent (pentobarbitonelN2O), 33 per cent (halothane), and 63 per cent (halothanelN2O) and at 0.35 ml-kg-1.min-1, 44 per cent (pentobarbitone), 14 per cent (pentobarbitonelN2O), and 56 per cent (halothane). Half of the dogs receiving VAE with halothanelN2O at 0.30 ml.kg-1.min-1 died within the first 10 min of the air infusion. Thus, no animals were studied at the next higher dose (0.35 ml-kg-1.min-1). The results suggest that the occurrence of VAE with nitrous oxide anaesthesia may result in greater haemodynamic consequence and increased likelihood for spillover of the venous bubbles into the arteries if used with halothane as compared to pentobarbitone.RésuméOn a étudié, chez les chiens, les effets qu’avait le protoxyde ďazote (N2O), utilisé lors ďune anesthésie à ľhalothane ou au pentobarbital, sur la filtration ďembolie gazeuse (EGV) par la circulation pulmonaire. On a causé des embolies gazeuses veineuses dans ľoreillette allant de 0.25 à 0.35 ml.kg-1.min-1 pendant 30 minutes, chez des chiens anesthésiés au pentobarbital, au pentobarbitallN2O, à ľhalothane, ouàľhalothanelN2O. Les animaux étaient en position de Trendelenburg en décubitus dorsal. Une sonde ultrason Doppler, localisée au-dessus de ľaorte suprarenale, détectait les bulles ďair artérielles qui échappaient à la filtration pulmonaire. On a décelé aucune bulles ďair à 0.25 ml.kg-1.min-1, mais à 0.30 ml.kg-1.min-1 ľincidence était de 11 pour cent (pentobarbital), 0 pour cent (pentobarbitallN2O), 33 pour cent (halothane), et 63 pour cent (halothanelN2O) et à 0.35 ml.kg-1.min-1, elle était 44 pour cent (pentobarbital), 14 pour cent (pentobarbitalN2O), et de 56 pour cent (halothane). La moitié des chiens recevant des EGV avec de ľhalothanelN2O àO.30 ml.kg-1 sont morts dans les dix minutes après ľinfusion de ľair. Nous n’avons donc pas étudié ďanimaux à la dose élevée qui suivait (0.35 ml.kg-1). Les résultats laissent entendre qu’il est possible que la conséquence hémodynamique soit plus importante et que la possibilité ďécoulement de bulles ďair veineuses dans les artères soit augmentée dans ľapparition de EGV avec protoxyde ďazote, si ce dernier est utilisé avec une anesthésie à ľhalothane en comparaison à une anesthésie au pentobarbital.

Carbon Dioxide Detection and Esophageal Intubation

Dr. Sum Ping’s letter (Anesth Analg 1987;66:483) is extremely important in its implication, for in recent years the determination of end-tidal COX has come to be widely accepted as the best method for determining proper endotracheal tube placement. The widespread use of infrared capnography and mass spectrometry in the operating room rests on the assumption that CO,, while abundant in alveolar gas, is virtually absent in stomach gas. We as anesthesiologists must respond to his concern, for if his interpretation is correct, we have placed far too much weight on this single measurement. Dr. Sum Ping’s conclusions raise two questions. First, how does the gas in the stomach accumulate so much carbon dioxide? Dr. Sum Ping postulates, ”If enough alveolar gas is forced down the esophagus into the stomach during mask ventilation prior to intubation, the concentration of CO, in the latter may be similar to that in the alveoli.” This suggestion appears simplistic, in that any alveolar gas forced into the stomach during mask ventilation will be diluted first with fresh anesthetic gases and subsequently with native stomach gas. Therefore, stomach gas, PCO, should not approach alveolar levels. Second, we are puzzled by the waveforms submitted. As Dr. Sum Ping points out, the waveform of the first three breaths looks virtually normal before becoming flat very quickly. We agree, but assert that this graph simply does not represent a pattern of gas washout. In the first three breaths depicted in the waveforms, there was no change in end-tidal CO,, followed by a precipitous drop to zero in breaths four to six. This pattern is not consistent with conventional washout curves and indicates that for the first three breaths no washout occurred! What happened between breaths three and four to account for this dramatic change? Another explanation might be that the tube was initially properly placed in the trachea, but became dislodged between breaths three and four. Proper tube placement explains the measurement of consistent physiologic levels of CO, observed in the first three breaths. The rapid decrease in CO, in subsequent breaths followed displacement and resulted from dilution with gas from the mouth, pharynx, andlor esophagus. As Murray and Modell have previously pointed out, inadvertent movement of the tube tip from the larynx to the pharynx produced distinctly different waveforms (1). We suggest that our explanation provides a plausible interpretation of the facts as presented by Dr. Sum Ping and believe that the measurement of expired CO, remains the standard of reference in the determination of proper endotracheal tube placement.

A comparison of different methods of lubrication of glass syringes used to identify the epidural space

Measurement of loss of resistance in glass syringes is a method widely used to locate the epidural space in epidural anaesthesia. Static and dynamic forces were measured under four experimental conditions in new glass syringes: unpolished, dry; polished, dry; unpolished, saline lubricated; and polished, saline lubricated. The unpolished saline lubricated syringes had a mean (SD) static force of 53.18 (15.0) g and dynamic force of 40.88 (15.2) g. These values were significantly greater than for polished dry syringes where the values were 5.27 (2.1) g and 4.38 (0.94) g, respectively. The results show that the least amount of resistance to plunger movement is obtained by dry polishing glass syringes.

Removal of tracheal secretions in anesthetized dogs: balloon catheters versus suction

Artificial secretions were removed by suction (using 12− or 18-French suction catheters) or by means of a balloon-tipped catheter (6-French Fogarty® arterial embolectomy catheter) in 20 experiments performed on five dogs anesthetized with halothane. Each dog had 5 ml of mucin injected 10 cm down the endotracheal tube prior to a 30-sec period of intermittent positive pressure ventilation. After this procedure, the ventilator was disconnected and the secretions were removed by suction with the 12− or 18-French catheters or by the Fogarty catheter. Each dog had balloon removal performed twice and suction performed once with the 12-French and once with the 18-French catheter. The endotracheal tube was cleaned and a 15-min stabilization period was allowed between each experiment. Arterial blood pressure (MAP) and pulmonary artery pressure (PAP) did not change after either technique. There were no ECG changes, arrhythmias, or alterations in PaCO2. The PaO2 was significantly lower in the two suction catheter groups [520 ± 33 mm Hg (12 French) and 451 ± 31 mm Hg (18 French)] than in the balloon removal group (564 ± 10 mm Hg) (P < 0.05). The balloon technique removed more secretions (4.52 ± 0.06 ml) than did suction (12 French, 1.32 ± 0.17 ml; 18 French, 2.11 ± 0.44 ml). Balloon removal of tracheal secretions has two advantages over conventional suction techniques: it removes more secretions, and it has less detrimental effect on arterial oxygenation.