Subjective assessment of left ventricular preload using transesophageal echocardiography: corresponding pulmonary artery occlusion pressures.

OBJECTIVE: To record pulmonary artery occlusion pressures (PAOPs) in patients whose left ventricular preload reserve was subjectively determined using transesophageal echocardiography (TEE). DESIGN: Prospective, blinded, nonrandomized. SETTING: University hospital. PARTICIPANTS: Twenty-three patients with well-preserved left ventricular function during nonemergent cardiac surgery. INTERVENTIONS: After separation from cardiopulmonary bypass, patients received repeated boluses of fluid volume through the aortic inflow cannula while being monitored with TEE. The endpoint for this fluid administration was a plateau in left ventricular fractional area change and end-diastolic area. This point at which additional fluid failed to cause noticeable increases in left ventricular end-diastolic area and fractional area change was defined as the preload reserve volume. After reaching the preload reserve volume, the PAOP was measured, as were the systolic blood pressure, left ventricular fractional area change, and end-diastolic area. MEASUREMENTS AND MAIN RESULTS: The mean PAOP for all patients at the time of achieving preload reserve volume was 18.6 +/- 2.9 mmHg. In 8 patients, the PAOP corresponding to preload reserve volume was elevated (20 to 25 mmHg). The remaining 15 patients had PAOPs ranging from 13 to 19 mmHg. When these 2 groups were compared with respect to left ventricular end-diastolic area, fractional area change, and systolic blood pressure, there were no significant differences between groups. The left ventricular wall thickness was significantly greater, however, in the group with elevated PAOP (1.37 +/- 0.04 cm) when compared with the group with normal ventricular filling pressures (1.05 +/- 0.15 cm) (p = 0.001). CONCLUSIONS: In patients with well-preserved left ventricular function and normal wall thickness, preload reserve volumes subjectively determined by TEE corresponded to a range of filling pressures historically targeted to maximize cardiac performance (13 to 19 mmHg). In a subset of patients with increased wall thickness, however, subjective determination of preload reserve was associated with filling pressures that were higher than traditionally considered optimal (20 to 25 mmHg). Similarities in left ventricular fractional area change and end-diastolic area between these 2 groups suggest that patients with elevated filling pressures had decreased ventricular compliance and were managed correctly with higher than usual PAOPs.

The effect of distance from injection site to the brainstem using spinal sufentanil.

BACKGROUND AND OBJECTIVES: Intrathecal (IT) sufentanil is commonly used in parturients to provide rapid onset of labor analgesia without motor block. This practice, although widely used, has been associated with severe respiratory depression in some patients. The mechanism of this respiratory depression is unclear, however, rapid cephalad movement and interaction with parenteral opioids are 2 frequently cited explanations for this complication. Because this complication has occurred only in women with heights between 150 and 157 cm, we elected to study the effect of the distance from injection site to the cisterna magna (CM) on peak brainstem cerebrospinal fluid (CSF) concentrations. METHODS: Ten adult ewes were injected with IT sufentanil (0.3 microg/kg) at a mean distance of either 71 cm (65 to 78 cm) from the brainstem (pelvic group) or 37 cm (34 to 42 cm) from the brainstem (thoracic group). CSF was then sampled at 5-minute intervals from the CM. RESULTS: Measurable CM concentrations of sufentanil were noted in the brainstem at 20 and 25 minutes, respectively, for the thoracic and the pelvic groups. Peak sufentanil concentrations from the thoracic group were nearly 10-fold higher (0.553 +/- 0.43 ng/mL) compared with the pelvic group (0.064 +/- 0.002 ng/mL) when measured in the CM (P =.023). CONCLUSIONS: Our results suggest that sufentanil migrates relatively large distances in the IT space. Injection site (distance from the brainstem) appears to be a prominent factor in determining brainstem concentrations and subsequent respiratory depression after spinal administration. Reg Anesth Pain Med 2001;26:306-309.

Congenital tracheal bronchus: the inability to isolate the right lung with a univent bronchial blocker tube.

Tracheal bronchus is a congenital anomaly in which the right upper lobe bronchus originates from the lateral tracheal wall. This anatomic variant is reported in approximately 1 of 250 patients at bronchoscopy. Although it is usually of little clinical significance, this atypical origin of the right upper lobe bronchus may complicate one-lung ventilation during thoracic surgery.

Rapid onset of ulnar nerve dysfunction during transient occlusion of the brachial artery.

UNLABELLED: Perioperative ulnar neuropathy is a complication that occurs even in patients who seem to be appropriately padded and positioned. The disproportionately high incidence of postoperative ulnar nerve injury compared with the median and radial nerves has largely been attributed to its vulnerability to compression or stretch at the cubital tunnel. Some clinical and laboratory evidence suggests that compromise of perfusion to the upper extremity may also play a role in this complication. To determine whether the ulnar nerve is more sensitive to ischemia of the upper extremity, we studied 10 men during general anesthesia. Somatosensory evoked potentials of the radial, median, and ulnar nerves were simultaneously recorded during general anesthesia with the brachial artery occluded proximal to the cubital fossa. All three nerves showed rapid changes in signal amplitude in response to occlusion of the brachial artery, but the amplitude of the ulnar nerve was affected earlier and to a greater degree. Compared with the median nerve, the change in ulnar nerve signal amplitude during ischemia was significantly greater after 4 min (P = 0.002). This trend persisted at 6 and 8 min (P = 0.008). At 4, 6, and 8 min of ischemia, the ulnar nerve likewise showed a greater decrease in amplitude compared with the radial nerve, with corresponding P values of 0.015, 0.008, and 0.008. We conclude that the ulnar nerve is more sensitive to ischemia of the upper extremity compared with the radial and median nerves. In addition to its increased vulnerability at the elbow, compromise of arterial flow may contribute to some cases of postoperative ulnar neuropathy. IMPLICATIONS: Postoperative ulnar neuropathy is thought to result from compression or stretch of the ulnar nerve at the elbow. However, patients may sustain this complication despite careful padding and positioning. This study suggests that the ulnar nerve may also be unusually sensitive to decreases in blood supply to the arm. Care should not only to properly position and pad the elbows, but also to ensure adequate perfusion of the upper extremities.

The effect of prior dural puncture on cerebrospinal fluid sufentanil concentrations in sheep after the administration of epidural sufentanil.

UNLABELLED: Sufentanil is a highly lipid soluble opioid that provides potent analgesia when administered in the subarachnoid space. Unfortunately, the penetration of sufentanil into the cerebrospinal fluid (CSF) after epidural administration is poor, and limits its effectiveness for epidural analgesia. Dural puncture may enhance the movement of epidural sufentanil into the subarachnoid space and increase its effectiveness. To determine whether the administration of epidural sufentanil adjacent to a dural puncture results in significantly greater CSF concentrations, 18 adult ewes were studied. Animals in the control group had an epidural catheter placed at the superior border of the pelvis without dural puncture. Animals in the study group had an epidural catheter placed, followed by a dural puncture performed using an 18-gauge Touhy needle. The dural puncture was performed one interspace cephalad to the epidural catheter. One hour after dural puncture, each animal received a loading dose of 0.35 microg/kg of sufentanil (5 microg/mL) through the epidural catheter, followed by an infusion of epidural sufentanil 0.15 microg x kg(-1) x h(-1) for a period of 4 h. After 4 h, CSF was sampled from a site one interspace caudad to the epidural catheter as well as at the cisterna magna. The mean CSF concentration of sufentanil at the level of the pelvis for animals with a dural puncture was 12.1 +/- 3.0 ng/mL compared with 1.8 ng/mL in controls with intact dura. Sufentanil concentrations at the cisterna magna were below the level of detection (0.08 ng/mL) for all animals in both groups. We conclude that an 18-gauge dural puncture significantly increases movement of sufentanil from the epidural to the intrathecal space. This increase in sufentanil concentration at the level of the pelvis was not associated with detectable levels of sufentanil at the brainstem. IMPLICATIONS: This study addresses the effect of dural puncture on spinal fluid concentrations of sufentanil after epidural administration. A sheep model was used to measure drug concentrations in the spinal fluid at the levels of the pelvis and brainstem after epidural administration. Dural puncture significantly enhanced movement of sufentanil into the spinal fluid at the level of the pelvis, but brainstem concentrations were below the level of detection. Analgesic concentrations of spinal sufentanil in the clinical setting, as well as brainstem concentrations associated with respiratory depression, have yet to be defined.

Transesophageal echocardiography: an objective tool in defining maximum ventricular response to intravenous fluid therapy.

Ventricular preload is an important determinant of cardiac function, which is indirectly measured in the clinical setting by the pulmonary capillary wedge pressure (PCWP). Transesophageal echocardiography (TEE) is rapidly gaining acceptance as a monitor of cardiac function. Although it provides high-resolution images of cardiac structures, clinical assessment of ventricular preload using TEE has been subjective, since quantitative measurements have been difficult to perform in a timely fashion. Automated border detection (ABD) is a new technology used in conjunction with TEE that allows quantitative real-time, two-dimensional measurement of cavity areas. To determine whether enddiastolic area (EDA) measured by ABD can be used to determine an appropriate end point for intravenous fluid administration, nine mongrel dogs were studied. Anesthetized animals were hemorrhaged to achieve a central venous pressure of 0-5 mm Hg. Each animal was then given intravenous fluid (autologous blood followed by hetastarch) until a peak in thermodilution cardiac output (CO) was achieved. Measures of PCWP, EDA, CO, and left ventricular stroke work (LVSW) were obtained after each fluid bolus. Bivariate plots displaying administered volume versus CO, LVSW, and EDA revealed parallel curves for each of these variables with peaks evident at cumulative volumes of 50-55 mL/kg. Multiple regression with mixed model analysis of covariance was performed to determine the significance of EDA in relation to changes in CO and LVSW. Analysis was likewise performed comparing the relationship between PCWP and changes in CO or LVSW. A significant relationship was demonstrated when comparing EDA to changes in CO and LVSW (P = 0.03 and P < 0.0001, respectively). Similar analysis comparing PCWP to changes in CO and LVSW failed to demonstrate a significant relationship (P = 0.54 and P = 0.36, respectively). These data suggest that changes in EDA measured using TEE with ABD are related to trends in cardiac function and can suggest an appropriate end point for intravenous fluid administration as defined by maximum CO and LVSW. PCWP did not demonstrate a significant relationship to changes in CO and LVSW.

The effect of prior dural puncture on cisternal cerebrospinal fluid morphine concentrations in sheep after administration of lumbar epidural morphine.

Combined spinal epidural anesthesia has become increasingly popular as a method of providing rapid onset of analgesia or surgical block with access for further administration of analgesics or anesthetics. No in vivo studies have evaluated the relationship between dural puncture and drug transfer from the epidural space to the cerebrospinal fluid (CSF). To determine whether morphine administered in the epidural space adjacent to a dural puncture results in increased CSF concentrations at the cisterna magna (CM), 12 adult ewes were studied. Each animal was assigned to one of three groups. Animals in Group 1 served as a control and received no dural puncture. Animals in Group 2 received a dural puncture with a 25-gauge (G) Whitacre needle, while Group 3 animals received a dural puncture with an 18-G Tuohy needle. One hour after dural puncture, each animal was given epidural morphine, 0.2 mg/kg. Six hours after the administration of epidural morphine, CSF from the CM was sampled and analyzed by gas chromatography-mass spectrometry for morphine concentration. The mean morphine concentration at the CM for Group 1 (control) was 22 +/- 12 ng/mL, whereas animals with 25-G and 18-G dural punctures had concentrations of 154 +/- 32 ng/mL and 405 +/- 53 ng/mL, respectively (P = 0.0005). These data demonstrate that a significant increase in CSF morphine concentration at the brainstem will occur when lumbar epidural morphine is administered adjacent to a dural puncture. Furthermore, the increase in CSF morphine concentration is positively correlated with the size of the needle producing the dural puncture. These findings highlight the potential for delayed respiratory depression when epidural opiate administration follows a dural puncture.

Effect of intrathecal sufentanil on isoflurane requirements during lower abdominal surgery.

STUDY OBJECTIVE: To determine the effect of intrathecal sufentanil on volatile anesthetic requirements during lower abdominal surgery. DESIGN: Randomized, double-blind study. SETTING: Military tertiary care hospital. PATIENTS: 15 female patients, ASA status I and II, undergoing elective lower abdominal surgery. INTERVENTIONS: After induction of anesthesia, each patient had a lumbar puncture performed with a 24-gauge Sprotte needle through a Tuohy needle positioned in the epidural space to receive either intrathecal sufentanil 10 micrograms or intrathecal normal saline (control). An epidural catheter was then placed for use in postoperative analgesia. Anesthesia was maintained in all patients with isoflurane, air, and oxygen. Gas flows were constant and the isoflurane concentration was adjusted at 5-minute intervals to maintain systolic blood pressure within 20% of preoperative baseline. MEASUREMENTS AND MAIN RESULTS: The mean end-tidal isoflurane concentration during the first hour of surgery was significantly lower in the sufentanil group (0.74 +/- 0.02%) compared with the control group (1.05 +/- 0.03%) (p = 0.006), an overall reduction of 28% in the isoflurane requirement. CONCLUSION: Prior administration of intrathecal sufentanil significantly decreases the isoflurane requirement in surgical patients, in addition to its previously demonstrated rapid onset and receptor efficacy.

Early extubation after cardiac surgery using combined intrathecal sufentanil and morphine.

The records of 10 patients who had well-preserved respiratory and ventricular function and had received 50 micrograms of sufentanil and 0.5 mg of morphine intrathecally before induction of anesthesia for cardiopulmonary bypass surgery were reviewed. Anesthesia was maintained with isoflurane and no patient received intravenous narcotics intraoperatively. Postoperative analgesic requirements were low, with 7 of 10 patients requiring no supplemental analgesic during the first 12 hours. Early extubation (within 8 hours of arrival in the intensive care unit) was possible in 8 patients; two patients remained intubated for reasons unrelated to the anesthetic technique. No patient required naloxone, reintubation, or treatment for respiratory depression. Combined intrathecal sufentanil and morphine provided conditions that allowed successful early extubation in 8 of 10 of these selected cardiac surgery patients.

A comparison of patient controlled epidural analgesia with sufentanil by the lumbar versus thoracic route after thoracotomy.

To compare the efficacy of patient-controlled lumbar and thoracic epidural sufentanil, 22 patients scheduled for elective thoracotomy were assigned randomly to receive sufentanil via either a lumbar or a thoracic epidural catheter. For 24 h postoperatively, the patients received analgesia only by patient-controlled epidural sufentanil. There were no significant differences in the visual analog scale (VAS) for pain between the two groups at 8 and 24 h postoperatively. Nausea and pruritus were minimum, requiring treatment less than once per 24-h period in either group. The forced vital capacity (FVC) measured at 24 h (as a percentage of baseline FVC) showed no significant difference between the lumbar and thoracic groups (44.7 +/- 3.8 and 41.7 +/- 5.5; P = 0.68). The total sufentanil used by the lumbar and thoracic groups was not significantly different (196 +/- 25.2 micrograms and 157 +/- 28.6 micrograms; P = 0.32). We conclude that there is no clinical advantage of thoracic over lumbar epidural sufentanil in the thoracotomy patient with respect to quality of analgesia, amount of sufentanil used, severity of side effects, or postoperative pulmonary function.