Anesthesia and analgesia
-
Previous studies of gastric contents in children presenting for surgery specifically excluded those with gastrointestinal disorders. Because these children often need sedation or anesthesia for procedures such as upper endoscopy, it is important to determine the gastric fluid volume and pH in this group to better characterize their risk of aspiration. We therefore analyzed the gastric fluid volume and pH of children with a variety of gastrointestinal symptoms presenting for upper endoscopy. After obtaining institutional review board approval, the stomach contents of 248 children (aged 2 mo to 18 yr) presenting for upper endoscopy were prospectively measured under direct endoscopic vision. Children were fasted for both solids and liquids for at least 6 h (<6 mo) or 8 h (>6 mo). Gastric fluid pH was measured using pH paper. Children received either deep sedation or general anesthesia and were grouped according to their presenting diagnosis. Results were analyzed by using analysis of variance, Kruskal-Wallis, and correlation (P value < 0.05). The mean gastric fluid volume was 0.35 +/- 0.45 mL/kg (range 0-3.14 mL/kg), and the mean gastric fluid pH was 1.37 +/- 1.6 (range 1-7). Of the children, 33% had gastric fluid volumes >0.4 mL/kg, 87% had gastric fluid pH <2.5, and 30% had gastric fluid volume >0.4 mL/kg and pH <2.5. Children with the presenting complaint of abdominal pain had the largest gastric fluid volumes. These data are not appreciably different from historical controls (healthy children fasted for an equivalent period of time who did not have gastrointestinal symptoms). ⋯ When fasted for at least 6-8 h, children with a history of gastrointestinal symptoms presenting for upper endoscopy did not have gastric contents with increased volume and acidity compared with previously published groups of children without gastric symptoms who were fasted the same length of time. These results do not support the argument that children with gastrointestinal symptoms pose an increased anesthetic risk for aspiration.
-
Anesthesia and analgesia · Oct 1998
Comparative StudyA comparison of three modes of ventilation with the use of an adult circle system in an infant lung model.
We examined the efficiency of an adult circle system with adult bellows to deliver minute ventilation (VE) to an infant test lung model. A Narkomed 2B system (North American Drager, Telford, PA) using three modes of ventilator setup were used: A = time-cycled, volume-controlled using bellows excursion to control delivered volume; B = time-cycled, pressure-controlled using inspiratory pressure limit adjustment to control delivered volume; C = time-cycled, pressure-controlled using the inspiratory flow adjustment to control delivered volume. VE was measured with two compliances (normal and low) and four endotracheal tube (ETT) sizes (2.5-, 3.0-, 3.5-, and 4.0-mm inner diameter). VE was measured at peak inspiratory pressures (PIP) of 20, 30, 40 or 50 cm H2O while respiratory rate (RR) was held constant at 20 breaths/min. VE was measured as RR was set at 20, 30, 40, or 50 breaths/min while target PIP was held constant at 20 cm H2O. Data were analyzed using the multiple regression technique. With the low compliance model, VE was nearly identical regardless of the ventilator setup. With the normal compliance model, minor differences in VE were observed, especially at the highest RR and PIP. VE was dependent on RR, PIP, and lung compliance. Overall, the ventilator setup resulted in minor changes in VE. Very high PIPs were required to deliver VE to the low compliance model. ETT size did not affect VE when lung compliance was low; however, smaller ETT size was a factor when test lung compliance was normal, decreasing delivered VE at higher PIP and RR. We conclude that with a Narkomed 2B adult circle system VE is dependent on PIP, RR, and lung compliance, but not on mode of ventilator setup. ⋯ The results of this laboratory investigation indicate that when an adult circle system is used during infant anesthesia, the ventilation delivered depends primarily on the respiratory rate, peak inspiratory pressure, and the compliance of the lung being ventilated, rather than on the specific mode of ventilator setup.
-
Anesthesia and analgesia · Oct 1998
The effects of the lateral position on cardiopulmonary function during laparoscopic urological surgery.
Laparoscopic urological surgery is usually performed transperitoneally with retroperitoneal insufflation of carbon dioxide (CO2) in the lateral position. We studied whether a difference in the side of lateral position affected hemodynamic and pulmonary functions during pneumoperitoneum. Fifteen patients (eight in the right and seven in the left lateral position) undergoing elective laparoscopic urological surgery were studied under general anesthesia. Hemodynamic variables and blood gas data were recorded. Before insufflation, mean arterial pressure (MAP), mean pulmonary arterial pressure (MPAP), central venous pressure (CVP), and pulmonary capillary wedge pressure (PCWP) in the right lateral position were higher than those in the left lateral position. Pneumoperitoneum increased MAP, MPAP, CVP, PCWP, and cardiac index but decreased systemic vascular resistance in the right lateral position. Similar changes occurred during pneumoperitoneum in the left lateral position, but the changes were less than those in the right lateral position. The respiratory index (PaO2/PAO2), intrapulmonary shunt, and SpO2 did not change during pneumoperitoneum in either lateral position. Changing the side of the lateral position affected hemodynamic function but did not affect pulmonary oxygenation during pneumoperitoneum. ⋯ The right and left lateral positions produced different hemodynamic changes during laparoscopic urological surgery. The increases in preload and cardiac index and the decrease in systemic vascular resistance were greater in the right than in the left lateral position. Respiratory changes were not affected differently between the right and left lateral positions.
-
Anesthesia and analgesia · Oct 1998
A survey on the intended purposes and perceived utility of preoperative cardiology consultations.
Cardiology consultations are often requested by surgeons and anesthesiologists for patients with cardiovascular disease. There can be confusion, however, regarding both the reasons for a consultation and their effect on patient management. This study was designed to determine the attitudes of physicians toward preoperative cardiology consultations and to assess the effect of such consultations on perioperative management. A multiple-choice survey regarding the purposes and utility of cardiology consultations was sent to randomly selected New York metropolitan area anesthesiologists, surgeons, and cardiologists. In addition, the charts of 55 consecutive patients aged >50 yr who received preoperative cardiology consultations were examined to determine the stated purpose of the consult, recommendations made, and concordance by surgeons and anesthesiologists with cardiologists' recommendations. Of the 400 surveys sent to each specialty, 192 were returned from anesthesiologists, 113 were returned from surgeons, and 129 were returned from cardiologists. There was substantial disagreement on the importance and purposes of a cardiology consult: intraoperative monitoring, "clearing the patient for surgery," and advising as to the safest type of anesthesia were regarded as important by most cardiologists and surgeons but as unimportant by anesthesiologists (all P < 0.05). Most surgeons (80.2%) felt obligated to follow a cardiologist's recommendations, whereas few anesthesiologists (16.6%) felt so obligated (P < 0.05). The most commonly stated purpose of the 55 cardiology consultations examined was "preoperative evaluation." Only 5 of these (9%) were obtained for patients in whom there was a new finding. Of the cardiology consultations, 40% contained no recommendations other than "proceed with case," "cleared for surgery," or "continue current medications." Recommendations regarding intraoperative monitoring or cardiac medications were largely ignored. ⋯ We conclude that there seems to be considerable disagreement among anesthesiologists, cardiologists, and surgeons as to the purposes and utility of cardiology consultations. A review of 55 consecutive cardiology consultations suggests that most of them give little advice that truly affects management.
-
Anesthesia and analgesia · Oct 1998
Uncompensated blood loss is not tolerated during acute normovolemic hemodilution in anesthetized pigs.
Clinically, hemodilution to a hematocrit of 9% has been studied, but the effects of hypovolemia during this degree of hemodilution have not been elucidated. We studied the response to blood loss during extreme hemodilution and evaluated indicators of hypovolemia. Systemic and myocardial hemodynamics, oxygen transport, and blood lactate concentrations were measured in 12 anesthetized pigs exposed to a graded blood loss of 10, 20, 30, and 40 mL/kg. Six animals were hemodiluted (hematocrit 10.8% +/- 1.4%, mean +/- SD), and six animals served as controls (hematocrit 34.6% +/- 1.5%). Hemodilution decreased systemic oxygen delivery to 9.5 +/- 0.6 mL x kg(-1) x min(-1) (controls 21.7 +/- 3.9 mL x kg(-1) x min(-1)) (P < 0.01) despite a 31% increase in cardiac output. Systemic oxygen uptake was unchanged. Arterial lactate increased to 3.3 +/- 1.1 mM/L (controls 1.6 +/- 0.6 mM/L) (P < 0.05), and mixed venous oxygen saturation (SvO2) decreased to 38.2% + 4.8% (controls 68.6% +/- 2.9%) (P < 0.01). At a blood loss of 10 mL/kg, cardiac output continued to be greater in the hemodiluted animals (P < 0.01). Arterial blood pressure decreased to 61 +/- 8 mmHg (controls 84 +/- 18 mm Hg) (P < 0.05), whereas heart rate was unchanged. Systemic oxygen delivery decreased to 8.8 +/- 1.2 mL x kg(-1) x min(-1) (controls 14.1 +/- 2.5 mL x kg(-1) x min(-1)) (P < 0.01). Systemic oxygen uptake was maintained by a further increase in oxygen extraction, and SvO2 decreased to 29.7% +/- 7.3%, compared with 55.3% +/- 9.0% in controls (P < 0.01). Arterial lactate increased to 4.9 +/- 1.4 mM/L (controls 1.8 +/- 0.8 mM/L) (P < 0.01). Myocardial oxygen delivery and lactate uptake were unchanged. When the blood loss equaled 30 mL/kg, myocardial lactate production occurred, and two hemodiluted animals died of circulatory failure. Central venous and capillary wedge pressures changed minimally during the blood loss and did not differ between groups. We conclude that a decrease in arterial blood pressure and SvO2 were early signs of hypovolemia during hemodilution, whereas central venous pressure and pulmonary capillary wedge pressure were insensitive indicators. ⋯ Anesthetized pigs with extremely low hemoglobin levels (one third of normal) showed poor tolerance to blood loss >10 mL/kg. A decreasing arterial blood pressure, a decreasing oxygen saturation in the venous blood, and an increase in arterial blood lactate concentration were useful indicators of blood loss.