Baroreflex function in a patient with Bartter's syndrome

There is little information regarding circulatory responses in Bartter's syndrome, with the exception of marked resistance to vasopressors. We investigated baroreflex function in a 40-year-old woman with this syndrome. The patient showed oscillation of heart rate even with a small increase in blood pressure after administration of vasopressor agents. Variations in heart rate and blood pressure were exaggerated during halothane, nitrous oxide and oxygen anaesthesia. Although the mechanism of the unstable baroreflex in this syndrome remains to be proved, the instability may be attributable to many factors such as prostaglandins, hypovolemia, hypokalemia, halothane, nitrous oxide and positive pressure ventilation.

Circulatory responses to baroreflexes, Valsalva maneuver, coughing, swallowing, and nasal stimulation during acute cardiac sympathectomy by epidural blockade in awake humans

Reflex circulatory responses are chiefly governed by the integrated functions of both sympathetic and parasympathetic nervous systems at any moment. To examine how sympathetic denervation of the important effector organ, the heart, modifies such reflex responses, the authors compared circulatory responses to arterial baroreflexes, the Valsalva maneuver (VM), coughing (C), swallowing (S), and nasal stimulation (NS) before and after cervical epidural blockade using 10 ml of 1.5% lidocaine in awake, healthy humans. The cervico-thoracic sympathetic denervation (sensory block of C4-T7) caused a slight suppression of the baroreflex sensitivity assessed by increases in RR intervals to increased systolic blood pressure with a pressor test (phenylephrine) in all eight subjects studied; the mean slopes of the regression lines were 29.1 +/- 9.8 ms X mmHg-1 before the blockade and 17.2 +/- 6.3 ms X mmHg-1 after the blockade (P less than 0.05). However, the baroreflex sensitivity to a depressor test (nitroglycerin) remained unchanged following the blockade. Furthermore, the responses in heart rate and blood pressure to VM (Phases II and IV) and the responses in heart rate to C, S, and NS were partially suppressed after the blockade (P less than 0.05). Despite these suppressions, the overall responses to VM, C, S, and NS remained unchanged after the blockade. No predominant parasympathetic responses such as profound hypotension and bradycardia were observed during any maneuver after the blockade.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiovascular effects of ketamine in humans with cervical or lumbar epidural blockade

To examine the effect of sympathectomy induced by epidural blockade on the cardiovascular effects of ketamine anesthesia, the authors compared the changes in arterial blood pressure (AP) and heart rate (HR) following intravenous administration of ketamine in patients who had cervical epidural anesthesia (n = 18), lumbar epidural anesthesia (n = 16), or light general anesthesia alone (n = 16). Ketamine, 2 mg/kg, iv, produced statistically significant increases in both AP and HR in all patients studied. However, the per cent increases in systolic AP in the cervical group were statistically less than those in the lumbar epidural group and control groups (P less than 0.05), which did not significantly differ from each other. The changes in HR following ketamine in the cervical group were significantly less than those in the other two groups (at 3-10 min following ketamine) (P less than 0.05). These results indicate that the cardiovascular stimulatory effects of ketamine are suppressed partially by a high level of epidural anesthesia but not by a low level of epidural blockade. Since patients with cervical epidural anesthesia had an analgesic level extending between C4 and Th8, the above attenuative effects of epidural blockade may be considered to be attributable to cardiac sympathectomy induced by a high level of epidural anesthesia.

The effects of subarachnoid lidocaine and phenylephrine on spinal cord and cerebral blood flow in dogs

To investigate the central nervous system circulation during spinal anesthesia, local spinal cord blood flow (SCBF) and cerebral blood flow (CBF) were measured simultaneously by the hydrogen clearance technique following subarachnoid lidocaine, phenylephrine, or a combination of both. The mean control values of SCBF and CBF were 22.4 +/- 7.9 ml X 100 g-1 X min-1 and 53.1 +/- 12.0 ml X 100 g-1 X min-1, respectively, in dogs lightly anesthetized with halothane. The subarachnoid administration of lidocaine solutions (1, 2, 3, and 5%), 1 ml, failed to produce statistically significant changes in SCBF (P greater than 0.05). Whereas, when phenylephrine (0.1, 0.2, 0.3, and 0.5%), 1 ml, was injected into the spinal subarachnoid space, SCBF decreased significantly with concentrations greater than 0.2% (P less than 0.05). When a mixture of lidocaine (24 mg) and phenylephrine (1 mg) was administered into the subarachnoid space, SCBF decreased significantly and returned to control within 60-90 min. CBF did not change significantly with any of the injections, remaining within less than +/- 12% of control. Dextrose solutions in water (5 and 7.5%), which were used for dilution of the drugs, did not affect either SCBF or CBF. These results indicate that local spinal cord blood flow can be affected significantly during spinal anesthesia when phenylephrine is added to the local anesthetic solution. However, the circulatory effects of drugs injected into the spinal subarachnoid space appear to be restricted to the local spinal cord per se and do not involve other parts of the CNS.

[Mechanism of morphine-induced suppression of central nervous system blood flow]

Narcotic agonists such as morphine are well known to decrease cerebral blood flow and metabolism. To investigate a possible mechanism for this action of narcotics, cerebral blood flow (CBF) and spinal cord blood flow (SCBF) were simultaneously measured by the hydrogen clearance technique following intravenous or subarachnoid administration of morphine and subsequent naloxone in lightly anesthetized dogs. The effects of new opiate agonist + antagonists, cyclazocine and buprenorphine, alone or in a combination with naloxone on those CNS blood flow were also investigated. Morphine, 1 mg/kg iv, produced significant decreases in both CBF and SCBF (p less than 0.01), which were reversed by naloxone, 40 micrograms/kg. Naloxone per se did not produce any change in both. Cyclazocine, 50 micrograms/kg iv, also produced significant decreases in both CBF and SCBF (p less than 0.05), but the decreased CBF was not reversed by naloxone. Buprenorphine, 30 micrograms/kg, showed variable changes in both CBF and SCBF, resulted insignificant reduction. However, spinal subarachnoid administration of morphine, 0.2 mg, with which profound analgesia can be obtained in human adults, did not cause any changes in SCBF as well as CBF. These results suggest that narcotic analgesics affect SCBF similar to CBF and morphine decreases CNS blood flow via the activation of supraspinal opiate receptors.

Baroreflex control of heart rate during cardiac sympathectomy by epidural anesthesia in lightly anesthetized humans

To evaluate the effects of acute sympathetic denervation on the baroreflex control of heart rate, baroreflex sensitivities were compared in lightly anesthetized humans who had either cervical (N = 20) or lumbar epidural anesthesia (N = 18), or neither (N = 18). Levels of anesthesia during cervical block using 10 ml of 2% mepivacaine without epinephrine were C3-T7 and T7-S1 during lumbar epidural block. Baroreflex sensitivity was assessed with a pressor test using phenylephrine infusion to increase systolic blood pressure by 60 mm Hg within 2 min. There were no statistically significant differences in the baroreflex sensitivities in the absence of epidural block and during lumbar epidural block, the slopes of the regression line (in msec of RR interval change per mm Hg increase in systolic blood pressure, i.e., msec/mm Hg) relating systolic pressure and the succeeding pulse interval being 3.8 +/- 1.4 (mean +/- SD) and 3.7 +/- 1.7, respectively. The mean slope during cervical block, 1.1 +/- 1.2 msec/mm Hg, was significantly different from the slopes observed in the absence of epidural block and during lumbar epidural block (P less than 0.01). The results suggest that cardiac sympathectomy induced by epidural anesthesia can suppress partially baroreceptor function by interrupting sympathetic efferent fibers innervating the heart during high levels of epidural anesthesia, but that lumbar sympathectomy during epidural anesthesia is unlikely to affect baroreceptor activity.

Effects of intravenous or subarachnoid morphine on cerebral and spinal cord hemodynamics and antagonism with naloxone in dogs

In order to elucidate the possible mechanism(s) by which opiates may affect cerebral and spinal circulation, and cerebral metabolism, cerebral blood flow (CBF) and spinal cord blood flow (SCBF) were measured simultaneously following intravenous or subarachnoid administration of morphine in dogs lightly anesthetized with halothane. The mean values of CBF and SCBF, using hydrogen clearance methods, were 52.3 +/- 14.7 ml . 100 g-1 . min-1 (mean +/- 1 SD) and 22.3 +/- 9.0 ml . 100 g-1 . min-1, respectively. Morphine hydrochloride, 1 mg/kg, when given intravenously, reduced both CBF and SCBF to approximately 73% of the control values (P less than 0.01). These changes were accompanied by decreases in the cerebral metabolic rates for oxygen (CMRO2) and glucose (CMRglucose). The circulatory effects and, in part, the metabolic effects, were reversed by naloxone 40 microgram/kg iv. Prior administration of naloxone blocked the morphine effects on CBF and SCBF and suppressed the effects on CMRO2 and CMRglucose. The decreases in blood pressure (MAP) and heart rate (HR) were similar following morphine iv with or without prior administration of naloxone. However, when 0.2 mg morphine was injected into the spinal subarachnoid space, the above variables remained unaffected. Neither naloxone alone, nor its subsequent intravenous administration following spinal morphine, affected cerebral and spinal circulatory or cerebral metabolic indices. These results indicate that intravenous morphine affects both cerebral and spinal cord blood flow via the opiate receptors at supraspinal sites of action.

Plasma concentrations of lidocaine associated with cervical, thoracic, and lumbar epidural anesthesia

We measured arterial plasma concentrations of lidocaine by enzyme immunoassay when 10 ml of 2% lidocaine without epinephrine was injected into the cervical, thoracic, or lumbar epidural spaces in 30 patients. There was no difference in the time courses of plasma levels of lidocaine. Peak concentrations were achieved 10 min after injection and were similar regardless of the site of injection. These results indicate the absence of significant differences in the rate of vascular absorption of lidocaine from different parts of the epidural space.

Postcardiopulmonary resuscitation pulmonary edema

Although severe pulmonary edema is encountered occasionally in patients needing CPR, there has been no definitive description on the mortality and morbidity of pulmonary edema after CPR. The author experienced severe pulmonary edema after standard CPR in 20 of 71 patients who suffered sudden, unexpected cardiac arrest and regained heart function by CPR. The varied onset of pulmonary edema, which may have developed when massive pink frothy secretions exited from the endotracheal tube, ranged from a few minutes to 45 min after the re-establishment of heart beat. These 20 patients showed a significantly higher P(A-a)O2, insignificant lower plasma protein concentrations, and high plasma osmolarities as compared with those who did not develop pulmonary edema. Only 2 patients with pulmonary edema survived. During CPR, many factors could cause pulmonary edema, including external cardiac massage (ECM), administration or release of catecholamines, hypoxia, acidosis, overhydration, etc. This study indicates that patients who need CPR have a high likelihood of developing pulmonary edema.

Hemifacial spasm: a new technique of facial nerve blockade

A new technique of facial nerve blockade using a special needle and a nerve stimulator was introduced. The results in patients suffering from hemifacial spasm are reported. This technique reduced the difficulties in identifying the facial nerve and decreased the suffering associated with the conventional way of creating these blocks. The technique described may also allow titration of neurolytic agent which may produce complete relief from spasm with much less likelihood of facial paralysis after the nerve blockade.