Suzanne Huffnagle

Complications of labor analgesia : epidural versus combined spinal epidural techniques

Both epidural and combined spinal epidural (CSE) analgesia can provide maternal pain relief during labor. Currently, there are few data comparing the risks and complications of these two techniques. We recorded the incidence and severity of anesthetic-related complications in 1022 laboring parturients. Ninety-eight women opted for either no or parenteral analgesia, 388 chose epidural, and 536 requested CSE analgesia. Women choosing CSE analgesia most often received an intrathecal injection of sufentanil 10 micrograms at the time of epidural catheter insertion. The epidural catheters were then dosed as needed as the intrathecal analgesia waned. Women who received CSE analgesia were more likely to itch (41.4% vs 1.3%) or complain of nausea (2.4% vs 1.0%) or vomiting (3.2% vs 1.0%) than those receiving solely epidural analgesia. Patients who requested only epidural analgesia were more likely to suffer an unintended dural puncture (4.2% vs 1.7%). Fewer than 10% developed hypotension with either technique. The risk of headache was the same with both anesthetics (4%-10%) and did not differ from the incidence of headache in women not receiving neuraxial analgesia (10%-14%). Six patients required epidural blood patch for moderate to severe postural headache. Four of these women suffered a dural puncture with the 18-gauge Hustead epidural needle. The other two women had reportedly uncomplicated epidural and CSE analgesia. These data suggest either neuraxial analgesic technique can safely relieve the pain of labor. CSE analgesia is a safe alternative to epidural analgesia for labor and delivery.

Intrathecal Sufentanil Dose Response in Nulliparous Patients

Background Intrathecal sufentanil provides effective analgesia during the first stage of labor. A range of doses has been reported to provide adequate pain relief. This study determined the dose of intrathecal sufentanil that produced acceptable pain relief in 50% of nulliparous patients (ED50) who requested labor analgesia. Methods With institutional review board approval, 50 nulliparous patients requesting spinal opioid labor analgesia were enrolled into this prospective, randomized, double‐blinded study. Each patient was in spontaneous labor at <5 cm cervical dilation. Patients received one of the following doses of intrathecal sufentanil: 1, 2, 3, 5, or 10 [micro sign]g in 3 ml preservative‐free saline (n = 10 for each dose). Pain, pain relief, hemodynamic, respiratory, and side effect data were collected at times 0, 2, 5, 10, 15, 20, 25, and 30 min. Probit analysis of the number of patients in each group who requested additional pain medicine at 30 min was used to determine the ED50. Results The groups were demographically similar. The ED50 of intrathecal sufentanil was 1.8 [micro sign]g (SE, 0.6 [micro sign]g; 95% CI, 2.96 to 0.54 [micro sign]g). The incidence of side effects was similar among the groups. Conclusions This is the first study to determine the ED50 of intrathecal sufentanil in spontaneously laboring nulliparous patients. As dose‐response curves are determined for other labor analgesics, future studies can compare equianalgesic doses or dose combinations.

The dermatomal spread of epidural bupivacaine with and without prior intrathecal sufentanil.

Clinicians often use a technique combining intrathecal sufentanil and epidural bupivacaine to provide labor analgesia.This study determines the effect of 27- or 24-gauge dural puncture and intrathecal sufentanil 10 micro gram on the dermatomal spread of epidural bupivacaine. Healthy laboring women received no dural puncture (n = 77) (no puncture group [NPG]) or dural puncture with a 27-gauge Whitacre needle (n = 33) or a 24-gauge Sprotte needle (n = 37) and intrathecal sufentanil 10 micro gram (dural puncture group [DPG]) before epidural injection of 13 mL bupivacaine 0.25%. More dermatomes were anesthetized in the DPG, 16.6 +/- 7.5 vs 13.6 +/- 6.6 in the NPG (P < 0.02). More patients in the DPG had sensory blockade T-4 or higher (17 of 70 DPG patients vs 8 of 77 NPG patients; P < 0.05). No patient in either group showed clinical evidence of respiratory compromise. In conclusion, epidural bupivacaine anesthetized more dermatomes when administered 104 +/- 42 min after dural puncture and intrathecal sufentanil 10 micro gram than when given without prior dural puncture and intrathecal injection. (Anesth Analg 1996;83:526-9)

Comparative accuracies of a finger blood pressure monitor and an oscillometric blood pressure monitor.

A noninvasive blood pressure monitor (Finapres) that uses the methodology of Peňaz to continuously display the arterial waveform from the finger has been introduced recently. The Finapres monitor overestimated systolic pressure by 5.8±11.9 mm Hg, while the Dinamap monitor underestimated systolic pressure by −6.9±9.2 mm Hg (P=0.003). Dinamap mean and diastolic pressure biases were less than 2 mm Hg, while the Finapres biases for these variables were significantly greater (7.7±10.0 and 8.2±9.8 mm Hg, respectively). There was no difference in systolic or mean pressure precision between the two devices (approximately 10 mm Hg), but the diastolic precision of the Dinamap unit was superior to that of the Finapres. While in most patients the Finapres monitor provided continuous blood pressure data equivalent to the data from the radial artery, marked bias (>15 mm Hg) was exhibited in 2 patients for all three pressure variables. Despite this bias, blood pressure changes were tracked closely in these 2 patients. We conclude that, in its current form, the Finapres monitor cannot be relied upon independently to accurately measure blood pressure in patients undergoing general anesthesia. Since the Dinamap monitor measures mean pressure reliably and accurately, we suggest that mean blood pressure values between the Finapres and Dinamap monitors be compared to guide one in interpreting Finapres data.

The Influence of Epidural Needle Bevel Orientation on Spread of Sensory Blockade in the Laboring Parturient

Both asymmetrical sensory blockade and dural puncture are undesirable outcomes of epidural analgesia.Identifying the epidural space with the needle bevel oriented parallel to the longitudinal axis of the patients back limits the risk of headache in the event of dural puncture. However, rotating the bevel to direct a catheter cephalad may risk dural puncture. We prospectively studied the effects of needle rotation on the success of labor epidural analgesia and on the incidence of dural puncture. One hundred sixty ASA physical status I or II laboring parturients were randomly assigned to one of four groups. The epidural space was identified with the bevel of an 18-gauge Hustead needle directed to the patients left. It was then rotated as follows: Group 0 = no rotation, final bevel orientation left (n = 39); Group 90 = rotation 90[degree sign] clockwise, bevel cephalad (n = 43); Group 180 = rotation 180[degree sign] clockwise, bevel right (n = 36); Group 270 = rotation 270[degree sign] clockwise, bevel caudad (n = 42). A single-orifice catheter was inserted 3 cm, and analgesia was induced in a standardized fashion. Dural puncture was evenly distributed among the groups (4.4%). There were more dermatomal segments blocked, fewer one-sided blocks, and more patients comfortable at 30 min with the needle bevel directed cephalad. Using a catheter inserted through a needle oriented in the cephalad direction increases the success of epidural analgesia. Implications: This prospective study shows that an epidural catheter inserted through a needle oriented in the cephalad direction increases the success of labor analgesia in the parturient. Carefully rotating the needle cephalad does not increase the risk of dural puncture, intravascular catheters, or failed blocks. (Anesth Analg 1998;87:326-30)

Sufentanil Disposition: Is It Affected by Erythromycin Administration?

Background:Because oral erythromycin administration has been associated with reduced elimination of alfentanil, suspicion has been raised about related opioids with similar metabolic pathways. A controlled crossover study of sufentanil pharmacokinetics was undertaken to resolve this issue. Methods:Six subjects had measurements of plasma concentrations for 9 h after intravenous administration of sufentanil (3 μgAg). Each subject was studied following no erythromycin (control) and after 1− and 7-day courses of erythromycin base. Results:Plasma concentrations during the 9 h of measurement were similar before and after erythromycin. Terminal half-life and clearance and distribution volume did not change significantly among treatment groups. Values measured after 7 days of erythromycin were similar to controls. Conclusions:Prior administration of erythromycin docs not alter pharmacokinetics of sufentanil in the 9 h following sufentanil administration. Thus, there are no apparent clinical consequences of prior or concomitant erythromycin administration in patients receiving sufentanil for procedures of 9 h or less.

A comparison of labetalol and nitroprusside for inducing hypotension during major surgery.

The hemodynamic and intrapulmonary shunt effects of intravenous labetalol and nitroprusside were compared during induced hypotension for major spinal surgery. A randomized, double-blind protocol was used in which 20 patients, ASA physical status I or II, received either nitroprusside infusion (n = 10) or labetalol bolus injections of 10 mg every 10 min (n = 10) until mean arterial blood pressure was reduced to 55--60 mm Hg. Pulmonary artery pressures were measured and mixed venous samples obtained via a pulmonary artery catheter. Nitroprusside increased heart rate significantly more than labetalol during the period of hypotension. When compared with prehypotension baseline values, nitroprusside increased heart rate significantly with a concomitant significant decrease in systemic vascular resistance. Cardiac output increased significantly 60 min after hypotension was achieved in patients treated with nitroprusside. Systemic vascular resistance decreased significantly below baseline levels in patients treated with labetalol but without changes in cardiac output, heart rate, or mean pulmonary artery pressure. There was a 122% increase in intrapulmonary shunt with nitroprusside administration, compared with an 11% increase with labetalol. Labetalol was effective for inducing hypotension and was not associated with an increase in heart rate, intrapulmonary shunt, or cardiac output as seen with nitroprusside.

Intrathecal hyperbaric bupivacaine dose response in postpartum tubal ligation patients

Background and Objectives Because of its short duration, hyperbaric lidocaine has been a popular intrathecal drug to provide anesthesia for postpartum tubal ligation (PPTL). However, reports of transient symptoms associated with its use have prompted the search for alternative intrathecal local anesthetics for short procedures. Hyperbaric bupivacaine is rarely associated with transient neurologic symptoms, and we designed this study to determine the optimal dose of bupivacaine for PPTL that assures adequate sensory block and allows the patient the shortest recovery time. Methods Forty American Society of Anesthesiologists (ASA) I-II patients undergoing spinal anesthesia for PPTL were randomly assigned to receive 5.0, 7.5, 10.0, or 12.5 mg hyperbaric bupivacaine in the right lateral position. Results Despite sensory block above T-8 in all groups, 4 of the 5 patients in the 5-mg group developed blocks insufficiently dense for surgery and required general anesthesia. Failed spinals occurred evenly in the remaining groups. Motor regression was significantly more rapid with decreasing doses of bupivacaine. Time in the postanesthesia care unit (PACU) was shorter in the 7.5-mg group. Conclusions Hyperbaric bupivacaine 7.5 mg injected in the lateral position provides adequate surgical anesthesia for PPTL with a minimal duration of motor block and recovery time.

Multiport epidural catheters: does the air test work?

Background Multiport epidural catheters are popular; however, the reliability of the air test has not been evaluated with this catheter design. The authors determined the effectiveness of aspirating for blood and the air test in detecting intravascular multiorifice epidural catheters. Methods Three hundred women in labor underwent placement of a blunt-tip, three-hole, 20-gauge, lumbar epidural catheter. If there were no signs of spinal anesthesia, 3 ml lidocaine or bupivacaine was injected and the patient was observed for signs of spinal anesthesia. If there were no signs of spinal anesthesia, the authors injected 1 ml air through the epidural catheter while listening to the maternal precordium using a Doppler fetal heart rate monitor. Catheters through which blood was aspirated were air-tested and replaced. Patients with air–test-positive, blood–aspiration-negative catheters received 100 mg lidocaine through the catheter and were questioned about toxicity symptoms. The authors injected bupivacaine–fentanyl through aspiration-negative,air–test-negative catheters and recorded the sensory analgesic level 20 min later. Results The authors aspirated cerebrospinal fluid through one catheter and documented intravascular placement in 11 catheters. Results of the air test and blood aspiration were positive for eight catheters. Blood could not be aspirated from one air–test-positive catheter; perioral numbness developed in the patient after lidocaine injection. Blood was freely aspirated from two air–test-negative catheters. In the remaining 288 catheters, bupivacaine–fentanyl injection produced epidural analgesia in 279 patients and no effect in 9 patients. Conclusions The authors obtained false-negative results with both catheter aspiration and the air test. Fractionating the local anesthetic dose is important when using multiorifice epidural catheters.

Does the use of methylmethacrylate cement in total shoulder replacement induce hemodynamic or pulmonary instability

STUDY OBJECTIVE To investigate whether the use of methylmethacrylate cement causes hemodynamic or pulmonary instability during total shoulder replacement surgery. DESIGN Prospective, nonrandomized study. SETTING Operating room. PATIENTS 9 ASA physical status I and II patients. INTERVENTIONS A 20-gauge radial artery catheter was placed in the wrist opposite the surgical site. Sedation with midazolam was provided, and a pulmonary artery catheter was placed through an 8.5-Fr introducer into the patients right internal jugular vein. MEASUREMENTS AND MAIN RESULTS Before induction of anesthesia, systolic, diastolic, and mean arterial blood pressures; heart rate; central venous pressure; systolic, diastolic, and mean pulmonary artery pressures; pulmonary capillary wedge pressure; and thermodilution cardiac output measurements were obtained. Arterial and mixed venous blood gas samples also were collected and analyzed for calculation of Qs/Qt. These hemodynamic and pulmonary parameters were measured again just before cementing of each prosthesis with methylmethacrylate cement and at 1, 5, 10, and 20 minutes after cementing. There were no statistically significant changes in any of the measured hemodynamic parameters at any time. There was no statistically significant difference in the calculated intrapulmonary shunt fraction. CONCLUSION In this study population, the use of methylmethacrylate for total shoulder replacement was not associated with adverse hemodynamic events or increased intrapulmonary shunting.