Synthetic erythrocytes.

Synthetic erythrocytes (SEs) are made by incorporation of stroma-free hemoglobin (SFH) or lipid-heme into liposomes. They form spontaneously at the interface between the phospholipid material and aqueous solution. SEs are spheroid vesicles with diameters between 0.01 and 4 microns, capable of carrying and delivering oxygen in a manner similar to red blood cells (RBCs). Oxygen-dissociation curve is virtually identical to that of RBCs, with P50 = 28 torr, and adjustable by the addition of 2,3-DPG or inositol hexaphosphate. Liposome/heme containing lipid-heme, a synthetic O2-carrying substance, is capable of carrying as much O2 as RBCs. Liposome-encapsulated SFHs have smaller O2-carrying capacity, but can be made to equal that of RBCs. Viscosity of SE suspensions is somewhat higher than blood's viscosity, but has otherwise similar rheologic properties. A large number of in vivo experiments with laboratory animals prove the ability of SEs to maintain life after virtually complete removal of blood. Cardiorespiratory functions remain near-normal, blood chemistry exhibits reversible mild changes, and vital organs do not show significant abnormalities. Blood coagulation is not affected. Hemoglobin does not appear in urine and plasma, indicating mechanical stability in circulation and absence of diffusion through the membrane. SEs do not cause significant acute toxicity. The absence of blood groups makes them a universal blood donor. However, massive doses suppress the reticuloendothelial system (RES). The animals undergoing total exchange transfusions may die of septic shock, apparently caused by nonsterile infusate in combination with strong suppression of the RES. Longevity of SEs in circulation is proportional to the dose. At doses corresponding to more than 90% exchange transfusions, half-life is longer than 24 h. Since all materials used in preparation of SEs are naturally occurring in blood, SEs are easily metabolized and eliminated without allergic reactions. The absence of membrane proteins and chemical stability of SFH and phospholipids promises long shelf-life. SE suspensions are difficult to sterilize, particularly against the viruses that may be present in SFH. However, the use of sterile procedures during manufacturing, and extraction of hemoglobin from animals bred under strict infection control may eliminate that problem.

Bronchospasm during cardiopulmonary bypass. Etiology and management.

Severe bronchospasm occurring after extracorporeal circulation is an unusual event. We report three such cases. Possible etiologies include activation of complement anaphylatoxins during cardiopulmonary bypass, cardiac asthma, cold urticaria syndrome, exacerbation of preoperative bronchospastic disease, allergic reactions, drug-induced histamine release and beta-adrenergic blockade induced bronchospasm. The management and treatment of patients with this complication is reviewed.

Differential effects of advanced age on neurologic and cardiac risks of coronary artery operations.

Two thousand patients undergoing coronary artery bypass grafting with cardiopulmonary bypass were prospectively studied to compare the influence of age on the incidence of neurologic, cardiac, and other complications. Postoperative neurologic events were found in 56 (2.8%) patients, with an incidence in patients > or = 75 years (8.9%) more than twice that of patients 65 to 74 (3.6%) and nine times larger than in patients < 65 (0.9%). Cardiac complications did not differ between age groups except for low cardiac output state, which occurred 1.7 times more frequently in patients > or = 75 years compared with those < 65. Patients with postoperative neurologic events had a ninefold increase in mortality--35.7% versus 4.0%. Logistic regression analysis demonstrate the most important predictors of a postoperative neurologic event to be age, preoperative neurologic abnormality, recent myocardial infarction, and duration of cardiopulmonary bypass. The risk of neurologic complications increases disproportionately to the risk of cardiac complications in the elderly undergoing coronary artery bypass grafting with cardiopulmonary bypass. Despite neurologic improvement (32 of 56 patients), a postoperative neurologic event was second only to low cardiac output state as the postoperative complication most highly associated with in-hospital death. These results are important for decisions regarding selection of candidates for coronary artery bypass grafting and for prediction of surgical outcome.

Morbidity and duration of ICU stay after cardiac surgery. A model for preoperative risk assessment.

Although risk factors for mortality after cardiac surgery have been identified, there is no widely applicable method for readily determining risk of postoperative morbidity based on preoperative severity of illness. The goal of this study was to develop a model for stratifying the risk of serious morbidity after adult cardiac surgery using readily available and objective clinical data. After univariate analysis of risk factors in 3,156 operations, 11 variables were identified as important predictors by logistic regression (LR) analysis and used to construct an additive model to calculate the probability of serious morbidity. Reliable correlation was found between a simplified additive model for clinical use and the LR model. The clinical and logistic models were then tested prospectively in 394 patients and demonstrated a pattern of increasing morbidity with ascending scores similar to that predicted by the reference group. Increasing clinical risk score was also associated with a greater frequency of individual complications as well as prolongation of ICU stay. This study demonstrates that it is feasible to design a simple method to stratify the risk of serious morbidity after adult cardiac surgery. With further prospective multicenter refinement and testing, such a model is likely to be useful for adjusting severity of illness when reporting outcome statistics as well as planning resource utilization.

Minimal positive end-expiratory pressure (PEEP) may be "best PEEP".

In the absence of clinical trials, positive end-expired pressure (PEEP) has been accepted as efficacious for treatment of postoperative decreases in arterial oxygen tension (PaO2) from a variety of causes including adult respiratory distress syndrome (ARDS). PEEP is thought to increase PaO2 by alveolar recruitment, which in turn, has been hypothesized to play a decisive role in pulmonary recovery. One hundred and eighteen patients were followed prospectively, and after development of decreased PaO2, randomized to receive recruitive PEEP (determined by blood gas criteria) or supportive PEEP (the minimal PEEP required to maintain PaO2 above 60 mm Hg on .5 inspired O2 fraction (FIO2). No prognostic factors were significantly different between the two groups. Recruitive PEEP application in 22 patients yielded a significantly increased incidence of hypotension (55 percent), pneumothorax (20 percent), and death during treatment (27 percent) when compared to the 28 supportive PEEP patients who had no hypotension or pneumothorax and only one death during treatment (4 percent). After PEEP treatment, deaths in each group were similar (19 percent and 15 percent, respectively). We find no evidence that PEEP treatment promotes beneficial outcomes and conclude that recruitment attempts may be harmful.

Continuous epidural infusion for analgesia after major abdominal operations: a randomized, prospective, double-blind study.

We performed a prospective, randomized, double-blind study of continuous epidural analgesia for 72 hours after major abdominal procedures. Patients were randomly assigned to one of five treatment groups: epidural morphine, epidural bupivacaine, a combination of morphine and bupivacaine, epidural saline solution, and no epidural catheter. All patients received supplemental morphine sulfate or meperidine hydrochloride, intramuscularly or intravenously, as needed. Epidural infusion was begun at 2 to 4 ml/hr, depending on age and height, with two increments of 1 ml/hr allowed if pain relief was insufficient. All pain management decisions were made by nurses, who also monitored epidural function. Performance was measured four ways: pain as measured at regular intervals in the 72-hour period with a visual analog, pain as measured after 72 hours with the McGill Pain Questionnaire, amount of supplemental narcotics needed, and recovery of respiratory function and ambulation as percent of preoperative levels. The group that received the combination of morphine and bupivacaine did best on all measures; in most instances the difference between the results seen with the combination regimen and those seen with saline solution or no catheter were significant at the 0.05 level. With the exception of pruritus, complications were evenly distributed among all treatment groups, including noncatheterized controls. We conclude that epidural analgesia with the combination of morphine and bupivacaine is safe, is easily managed, and gives pain relief superior to that provided by traditional, systemic administration of narcotics.

Postthoracotomy pain management using continuous epidural analgesia in 1,324 patients.

Continuous epidural analgesia consisting of an opioid with or without a local anesthetic agent is a commonly employed technique for pain relief after thoracotomy. In this study, we prospectively evaluated the use of continuous epidural analgesia in 1,324 patients undergoing elective thoracotomy between 1987 and 1993. Epidural pain management was continued for 1 to 3 postoperative days. Patients experienced excellent pain relief, with mean visual analog pain scores of 2.4, 1.7, and 1.4 on postoperative days 1, 2, and 3, respectively. Side effects occurred most frequently in the first 24 hours postoperatively; the incidence of pruritus was 14.1%; nausea, 11.2%; hypotension, 4.3%; sedation, 3.3%; and numbness, 1.1%. Respiratory depression (< 8 breaths per minute) occurred in 1 patient who received 16 mg of supplemental morphine sulfate over a 2-hour period. The incidence of inadequate analgesia (a visual analog pain score of 7 or more persisting for 1 to 2 hours after an epidurally administered bolus) was 3.8%. The results from this study support the use of standard protocols for dosing guidelines, the treatment of inadequate analgesia, and the management of side effects. Daily evaluation by a team member of the postoperative analgesia services section of the Department of Anesthesiology enhances patient care and minimizes adverse effects.

Cancer pain relief using chronic morphine infusion. Early experience with a programmable implanted drug pump.

Fourteen patients were implanted with drug pumps to provide chronic epidural or intrathecal morphine to relieve pain due to cancer. A new programmable pump was used in seven of the patients and a constant infusion device was used in the other seven patients. Results, judged by subjective pain reports (on a 0 to 10 scale), decrease in oral narcotics, and change in activity level, were excellent in eight patients, good in five patients, and poor in one patient. The programmable device has the obvious advantage of being able to vary dose according to patient need and requires less frequent refilling. Four programmable pump failures occurred, two requiring replacement.

Cardiorespiratory effects of venous air embolism in dogs receiving a perfluorocarbon emulsion.

The cardiorespiratory effects of a nonlethal venous air embolism were studied in dogs in the presence of a perfluorocarbon emulsion (PFE). Prior to embolization, five dogs received 20 cc/kg of hydroxyethyl starch (6% HES) and five received PFE oxypherol (20% FC-43). Determinations of mean systemic arterial pressure (MAP), pulmonary artery pressure (PAP), left ventricular pressure (LVP), first and second derivatives of LVP with respect to time (dP/dt and Vmax), cardiac index (CI), stroke index, left and right ventricular stroke work index (LVSWI and RVSWI), PaCO2, PaO2, and venous admixture (Qs/Qt) were made before and then 1, 5, 10, and 30 minutes after placement of the venous air emboli (0.75 cc/kg/min for 5 minutes). After emboli were introduced, PaO2, MAP, LVSWI, dP/dt, Vmax, and CI decreased; the average decrease during the first 5 minutes was significantly less in the PFE group. Following introduction of venous air emboli, PAP, PaCO2, RVSWI, and Qs/Qt increased less in the PFE group than in the HES group, with statistical significance achieved at various times during the first 10 minutes after embolism. All parameters returned toward baseline values by 30 minutes in both groups. This study indicates that FC-43, when administered before venous air embolism, helps to attenuate some of the detrimental cardiorespiratory effects of the embolism.

Long-term testing of an intracranial pressure monitoring device.

OBJECT: Long-term monitoring of intracranial pressure (ICP) is limited by the lack of an implantable sensor with low drift. The goal of this study was to demonstrate that a new capacitive transducer system will produce accurate and stable ICP records over extended periods. METHODS: Intracranial pressure sensors were implanted into the frontal white matter of four dogs. In addition, a fluid-filled catheter was placed in the cisterna magna (CM) to measure cerebrospinal fluid (CSF) pressure. The animals were tested using standard physiological maneuvers such as jugular vein compression, head elevation, and CSF withdrawal from and saline injection into the CM to verify that the ICP sensor precisely matched CSF pressure changes. The mean ICP pressure and CM pressure were compared for months to demonstrate that the transducer system produced minimal drift over time. The change in the ICP sensor record closely duplicated that of the CSF waveform in the CM in response to well-known physiological stimuli. More important, mean ICP pressure remained within 3 mm Hg of CM pressure for months, with a mean difference of less than 0.3 mm Hg. Histological examination of the dog brains revealed only minimal tissue reaction to the presence of the sensor. CONCLUSIONS: The authors demonstrate a new implantable solid-state sensor that reliably measures ICP for months, with minimal drift. The clinical application of this sensor and its telemetry is for long-term monitoring of patients with head injury, mass lesions, and hydrocephalus.

Comparison of epidural butamben to celiac plexus neurolytic block for the treatment of the pain of pancreatic cancer.

OBJECTIVE: To compare pain relief in metastatic pancreatic cancer patients between neurolytic celiac plexus block (NCPB) and epidural 5% butamben suspension (EBS), a material-based delivery system of a local anesthetic that produces a long-lasting differential nerve block. DESIGN: Open-label patient-selected parallel groups. SETTING: Urban tertiary care medical center. PATIENTS: Twenty-four adult patients with metastatic pancreatic cancer experiencing pain uncontrolled by systemic opioids who were referred to a multidisciplinary pain clinic for interventional therapy. INTERVENTIONS: Antecrural NCPB-block with ethanol and epidural 5% butamben suspension injections. MEASURES: Subjective global pain relief assessments on a 0-100% scale were made weekly for 4 weeks and then monthly. Change in opioid use postintervention. RESULTS: Eight patients had a single NCPB and three patients had two NCPB. Four of the former and two of the latter had successful pain relief defined to be a more than 75% reduction in pain when compared with pretreatment maintained for more than 4 weeks or until death (if less than 4 weeks). Thirteen patients received EBS in divided doses. Eleven patients received a cumulative EBS dose of 5 grams, one patient received a cumulative EBS dose of 2.5 grams, and one patient received a cumulative EBS dose of 8.75 grams. Nine of the eleven patients and each of the other two patients had successful pain relief. The overall incidence (85% EBS vs. 55% NCPB), the duration of successful pain relief, and the percent reduction in opioid use did not differ between the two groups. There were no serious complications. CONCLUSION: EBS appears to be a safe and effective alternative to NCPB in the treatment of pancreatic cancer pain.

Vasopressor challenges during chronic MAOI or TCA treatment in anesthetized dogs.

Ten male mongrel dogs were treated in Phase I with tranylcypromine, 6 mg/kg IM b.i.d., for 21 days. Dogs were anesthetized at weekly intervals before, during, and up to four weeks after drug treatment with a combination of amylbarbital, 25 mg/kg, 1% enflurane in 70:30 N2O:O2 and fentanyl, 500 mcg. Bolus IV injections of norepinephrine, 0.1-0.6 mcg/kg, and ephedrine, 0.03-0.12 mg/kg were given while continuously recording arterial blood pressure, lead II of the ECG, heart rate, and rectal temperature. Awakening times were noted. In Phase II, the dogs were given imipramine, 25 mg/kg IM b.i.d., for 21 days. During Phase III, 14 days of tranylcypromine, 7 days of tranylcypromine plus imipramine, and 7 days of imipramine were administered. Anesthetic techniques were repeated in phases II and III. The fourth phase consisted of tranylcypromine injections, 6 mg IM b.i.d., and anesthesia with amylbarbital, 25 mg/kg, 2.5% enflurane in 70:30 N2O:O2. Vasopressor challenges were repeated during each phase of the study. Following induction of anesthesia and prior to fentanyl challenge, baseline blood pressures and heart rates did not differ from control in Phase I, II, and III of this study. Responses to norepinephrine during all of the tranylcypromine phases were not significantly different from control but ephedrine responses were prolonged, peaking by the second week of treatment. During Phase II, dysrhythmias occurred following norepinephrine and ephedrine with one lethality following norepinephrine, 0.2 mcg/kg. Responses to norepinephrine and awakening times were significantly greater during Phase II compared to Phase I. In Phase III, during the first week of combined therapy the responses to norepinephrine were significantly greater than any other week of this phase. During Phase IV, resting blood pressure and the ephedrine responses were significantly increased during tranylcypromine when the anesthesia regimen did not include fentanyl. These results suggest that during initial treatment with tranylcypromine or imipramine, cardiovascular responses to vasopressor challenges were predicted by the pharmacology of the antidepressant. During tranylcypromine phases, we did not observe exaggerated cardiovascular effects during anesthesia and vasopressor challenges as had been previously reported.

Nerve blocks with 5% butamben suspension for the treatment of chronic pain syndromes.

BACKGROUND AND OBJECTIVES: Butamben is a non-water-soluble local anesthetic that can be prepared as an aqueous suspension for nerve blocks. This report describes the use of 5% butamben suspension for the treatment of chronic pain of cancer and noncancer origin. METHODS: The clinical courses of 75 consecutive patients were analyzed following 5% butamben nerve blocks (35 epidural blocks only, 33 peripheral nerve blocks only, and 7 had both epidural and peripheral nerve blocks). Epidural blocks were performed as a series of four with additional blocks offered if needed. Peripheral nerve blocks were done as a single block with repeat injections if needed. Injection volumes varied between 15 and 25 mL for epidural injections and 5 and 20 mL for peripheral nerve blocks. Successful therapy was defined as a -75% reduction in subjective pain assessments for -4 weeks or until death. Daily opioid requirements were also recorded. RESULTS: Fifty-four of the 75 patients (72%) were successfully treated. This included 48 of 67 cancer patients (71.6%) and 6 of 8 noncancer patients (75%). Median duration of pain relief was 12 weeks (range, 1-96) in the cancer patients and 10 weeks (range, 6-166) in the noncancer patients. Mean reduction in opioid requirements in successfully treated cancer patients was 74+/-5%. Pain on epidural injection occurred in half of the patients and was the most prevalent complication of treatment. Five patients had signs of intravascular injection. There were no serious long-term sequelae. CONCLUSIONS: When used as described in this report, 5% butamben suspension appears to be effective for treatment of chronic pain of both cancer and noncancer origin and has a low incidence of adverse sequelae.

The effect of pancuronium on myocardial contraction and catecholamine metabolism.

The effects of pancuronium bromide infusion on the uptake and release of [14C] noradrenaline (14C-NA) by the isolated, perfused rat heart and on the chronotropic and inotropic activity of the isolated heart were evaluated. Hearts were removed from animals under light ether anaesthesia, transferred to a modified Langendorff perfusing apparatus and perfused with Krebs-Ringer bicarbonate solution at a rate of 5 ml min-1. The effect of pancuronium on the uptake of noradrenaline was determined by perfusing hearts for 5 min with perfusate containing various concentrations of pancuronium and 200 ng ml-1 of 14C-NA. After 5 min pancuronium-treated hearts contained less 14C-NA. The degree of reduced uptake increased with increasing concentrations of pancuronium. In addition, the combination of pancuronium perfusion and electrical stimulation (15 mA for 10 ms at 4 Hz) blocked the 50 min uptake of 14C-NA by the heart to a greater degree than either factor separately. The release of noradrenaline was determined after perfusing hearts with 14C-NA followed by perfusion with solution containing pancuronium but no 14C-NA for 1 h. Pancuronium infusion did not significantly alter the release of 14C-NA from the heart after 1 h of perfusion. The infusion of pancuronium caused a reduction in both the rate and strength of myocardial contraction of the isolated heart which was reversed by perfusion with perfusate free of pancuronium. Following perfusion with pancurnium the rate and strength of contraction of the heart was seen to "rebound" above pre-pancuronium values for a short period. The rebound of myocardial rate and contraction may have been due to the presence of myocardial noradrenaline previously blocked from reuptake by pancuronium since hearts removed from reserpinized animals did not demonstrate "rebound."

High frequency ventilation through a small catheter for laser surgery of laryngotracheal and bronchial disorders.

One-lung and two-lung high frequency ventilation (HFV) through a 2-mm internal diameter catheter was evaluated in 22 patients during endoscopic laser excision of stenotic lesions of larynx, trachea, and bronchi. High frequency ventilation at 80 to 250 breaths per minute using air during two-lung HFV and using air-oxygen at an inspired oxygen concentration of 25% during one-lung HFV maintained adequate alveolar ventilation and oxygenation in all patients. The use of HFV through a catheter allowed continuous control of ventilation and provided maximal surgical exposure for endoscopic laser surgery. The continuous outflow of HFV gases through the endoscope also prevented lung contamination with blood and debris. The potential of HFV polyvinylchloride catheter ignition by laser was also evaluated in the laboratory during continuous flow of air-oxygen and oxygen-nitrous oxide. The laser ignited polyvinylchloride tubes in all the mixtures of oxygen and nitrous oxide within 3 to 7 seconds. Oxygen at 30% mixed with nitrogen 70% was safe and all such tubes were not ignited by the laser. The ability of HFV to provide adequate oxygenation during endoscopic laser surgery using air-oxygen at an FiO2 below 30% also avoids the hazard of catheter and airway fire.

Measurements of viscosity of synthetic erythrocyte suspensions.

Measurements were made of the viscosity of suspensions of synthetic erythrocytes composed of hemoglobin solutions encapsulated in liposomes, as a function of shear rate, temperature, suspension concentration, lipid membrane composition, and the viscosity of the suspending medium. It was found that the viscous behavior of the synthetic erythrocyte suspensions was non-Newtonian and nearly the same as that of suspensions of natural erythrocytes prepared similarly, with the major difference being that synthetic erythrocyte suspensions are somewhat more viscous. Suspensions of Fluosol FC-43 prepared similarly were found to be essentially Newtonian fluids, and substantially different and more viscous than either erythrocyte suspension. The higher viscosity of synthetic erythrocyte suspensions probably accounts for the ability of these suspensions to maintain normal systemic vascular resistance in transfusion experiments, in spite of the fact that synthetic erythrocytes are smaller than natural erythrocytes.

High-cost, high-tech medicine: are we getting our money's worth?

Increasingly stringent fiscal restraints on the spending for health care, driven by the scarcity of health resources, has introduced a need to apply cost containment measures to nearly all aspects of medical care. Intelligent cost containment measures must include application of disciplined logic to the decision making process of when to use high-tech, high-cost interventions. Such decision making depends upon knowledge of the basic concepts of economic and cost-benefit analyses, outcome (benefit) studies, and some principles of decision-threshold analysis. These basic principles are reviewed, and the potential impact of application of strategies for cost containment in the operating room and the intensive care unit is discussed.

Isotonic hyponatremia following transurethral prostate resection.

The proper treatment of hyponatremia during transurethral resection of the prostate continues to be controversial. Two cases of isotonic hyponatremia are reported here, and the literature regarding the incidence and treatment of hyponatremia during transurethral resection of the prostate is reviewed. In each case, the patient developed neurologic changes during complicated transurethral prostate resection. Despite the rapid decrease in the serum sodium concentration, serum osmolality remained normal due to the resorption of the bladder irrigant glycine. Therefore, etiologies other than cerebral edema are postulated as the cause of the neurologic manifestations. Also, the role of the osmolar gap in directing appropriate therapy is emphasized in an effort to avoid unnecessary use of hypertonic saline. Finally, an appropriate differential diagnosis of the neurologic changes seen during the transurethral resection of the prostate syndrome is discussed.

A single bolus dose of esmolol in the prevention of intubation-induced tachycardia and hypertension in an ambulatory surgery unit.

The efficacy of a single bolus dose of esmolol in the prevention of intubation-induced tachycardia and hypertension was studied in a double-blind manner. Thirty patients from the Ambulatory Surgery Unit at Rush-Presbyterian-St. Luke's Medical Center were prospectively randomized to receive a placebo, 100 mg of esmolol, or 200 mg of esmolol immediately prior to induction (2.5 to 3.0 minutes before intubation). The groups were similar in demographic characteristics and with regard to preoperative blood pressure (BP) and heart rate (HR). Anesthetic management was standardized for all patients. Esmolol 100 mg (1.4 +/- 0.3 mg/kg) and 200 mg (2.6 +/- 0.7 mg/kg) significantly (p less than 0.05) blunted the maximum increases in HR and BP following intubation. The average maximum HR increase in the placebo group was 40% as opposed to 16% in the esmolol 100 mg group and 14% in the esmolol 200 mg group. Both esmolol groups blunted the tachycardic response over a 4-minute postintubation time period. The average maximum BP increase was 47% in the placebo group versus 22% and 19% in the esmolol 100 mg and esmolol 200 mg groups, respectively. There were no significant differences between the two esmolol groups. This study demonstrates the efficacy of a single bolus dose of esmolol in blunting the tachycardic and hypertensive responses to laryngoscopy and intubation in an ambulatory surgery setting.

Does the design of the Sprotte spinal needle reduce the force needed to deform the tip?

STUDY OBJECTIVE: To determine whether the window design of pencil-point spinal needles leads to deformation under lateral or axial loading conditions. DESIGN: Independent-measure, multigroup study of the force required to deform needles. SETTING: Independent testing laboratory. MEASUREMENTS AND MAIN RESULTS: The force necessary to bend 22- and 24-gauge Sprotte, 22- and 25-gauge Whitacre, and 22- and 25-gauge Quincke needles was measured using an Instron gauge (Instron Corp., Canton, MA) after microscopic verification of needle uniformity. Effects of lateral and axial forces were evaluated in separate experiments. The force needed to bend the Sprotte needles was less than that needed for the Whitacre and Quincke needles of similar size when lateral or axial pressure was applied. Microscopic inspection of the needles showed a marked variability in the window area placement in a single lot of Sprotte needles. Examination of the needle tips demonstrated that the Sprotte needles were most likely to bend at the needle window, while the Quincke and Whitacre needles deformed at the point of clamping. CONCLUSIONS: The Sprotte needles have an inherent design weakness to lateral and axial pressure, which may result in a greater number of needle tip deformations upon needle insertion. The nature of this deformation may result in difficulty in needle withdrawal and possibly fracture of the needle tip.