Lars Irestedt

Severe Neurological Complications after Central Neuraxial Blockades in Sweden 1990–1999

Background:Central neuraxial blockades find widespread applications. Severe complications are believed to be extremely rare, but the incidence is probably underestimated. Methods:A retrospective study of severe neurologic complications after central neuraxial blockades in Sweden 1990–1999 was performed. Information was obtained from a postal survey and administrative files in the health care system. During the study period approximately 1,260,000 spinal blockades and 450,000 epidural blockades were administered, including 200,000 epidural blockades for pain relief in labor. Results:The 127 complications found included spinal hematoma (33), cauda equina syndrome (32), meningitis (29), epidural abscess (13), and miscellaneous (20). Permanent neurologic damage was observed in 85 patients. Incidence of complications after spinal blockade was within 1:20–30,000 in all patient groups. Incidence after obstetric epidural blockade was 1:25,000; in the remaining patients it was 1:3600 (P < 0.0001). Spinal hematoma after obstetric epidural blockade carried the incidence 1:200,000, significantly lower than the incidence 1:3,600 females subject to knee arthroplasty (P < 0.0001). Conclusions:More complications than expected were found, probably as a result of the comprehensive study design. Half of the complications were retrieved exclusively from administrative files. Complications occur significantly more often after epidural blockade than after spinal blockade, and the complications are different. Obstetric patients carry significantly lower incidence of complications. Osteoporosis is proposed as a previously neglected risk factor. Close surveillance after central neuraxial blockade is mandatory for safe practice.

Fetal and maternal plasma catecholamine levels at elective cesarean section under general or epidural anesthesia versus vaginal delivery

Fetal and maternal plasma levels of catecholamines were measured at birth in 40 women with normal term pregnancies who underwent elective cesarean section. Twenty women were operated on under general anesthesia, and 20 under epidural anesthesia. For comparison, the same measurements were also made in 10 women who underwent vaginal delivery without signs of intrapartum fetal distress. Maternal venous levels of catecholamines were elevated in all three groups as compared to values in the resting adult. The highest levels were found in the vaginal delivery group (norepinephrine and epinephrine, 3.9 +/- 2.1 and 1.1 +/- 1.0 nmoles/L, respectively), and the lowest in the epidural cesarean section group. Fetal outcomes were similar in all three groups, as judged by Apgar scores and by measurements of umbilical arterial blood gases. In spite of that, neonates delivered vaginally showed a markedly higher sympathoadrenal activation (norepinephrine and epinephrine, 31.8 +/- 24.1 and 5.1 +/- 7.6 nmoles/L, respectively) than those born by elective cesarean section. In the latter group, however, it was found that the type of maternal anesthesia influenced fetal sympathoadrenal activation, since neonatal levels of catecholamines were higher in the epidural section group (norepinephrine and epinephrine, 9.5 +/- 6.4 and 4.0 +/- 4.5 nmoles/L, respectively) than in the general anesthesia group (norepinephrine and epinephrine, 3.2 +/- 2.7 and 1.0 +/- 1.4 nmoles/L, respectively). These results may have a certain clinical relevance since fetal sympathoadrenal activation is thought to promote extrauterine adaptation.

Controlled Hypotension with Adenosine in Cerebral Aneurysm Surgery

The cardiovascular effects of adenosine-induced controlled hypotension were studied in 10 patients undergoing cerebral aneurysm surgery. Adenosine and its metabolites were measured in arterial plasma using high-pressure liquid chromatography. Whole body and cerebral arteriovenous oxygen content differences (AVDO2), arterial lactate levels, and arteriojugular lactate differences were determined. In order to reduce the dose requirement of adenosine, the patients were pretreated with the adenosine uptake inhibitor, dipyridamole (0.3–0.4 mg · kg-1). During the infusion of adenosine (0.14 ± 0.04 mg · kg-1 · min-1) the mean arterial blood pressure decreased by 43%, from 82 to 46 mmHg, during a mean hypotensive period of 32 min, without signs of tachyphylaxis. The arterial adenosine level increased from 0.15 ± 0.02 to 2.45 ± 0.65 μM (P < 0.01). Hypotension was caused by a profound decrease in peripheral vascular resistance (61 ± 3%, P < 0.01), which was accompanied by an increase in cardiac output (44 ± 9%, P < 0.01). Heart rate increased moderately by 16 ± 5% (P < 0.01). Pulmonary vascular resistance and central venous pressures were unaffected. Arterial lactate and PaO2 were unchanged, while whole body oxygen consumption was decreased by 13 ± 4% (P < 0.05). The AVDO2 across the brain was decreased by 37 ± 5% (P < 0.05) without signs of lactate formation. The authors conclude that adenosine rapidly induces a stable and easily controlled hypotension in humans by dilation of arterial resistance vasculature.

Adenosine concentration in umbilical cord blood of newborn infants after vaginal delivery and cesarean section

ABSTRACT: Umbilical blood was collected immediately at birth (<30 s) in full-term infants after vaginal deliveries (n = 33) and elective cesarean sections (n = 11). Blood gases, plasma adenosine, hypoxanthine, and catecholamine concentrations were determined. In vaginally born infants the median arterial adenosine concentration was found to be 0.46 μM (range 0.13-2.06) and the venous 0.48 μM (0.09-1.62). These levels were significantly higher (p < 0.01) than in infants delivered by elective cesarean section; 0.16 μM (0.04-0.42) in the artery and 0.17 μM (0.02-0.56) in the vein. Vaginally born infants showed about a 4-fold higher level of umbilical arterial catecholamines than infants born by elective cesarean section. There was a strong inverse correlation between arterial hypoxanthine concentration and pH (r =-0.81, p < 0.01). It is suggested that increased adenosine release at vaginal delivery modulates the stress response elicited by the strong catecholamine surge and may furthermore exert protective effects in perinatal asphyxia.

Central and Splanchnic Hemo dynamics in the Dog during Controlled Hypotension with Adenosine

Central and splanchnic hemodynamic effects during controlled hypotension induced by the administration of the endogenous vasodilator adenosine were studied in ten artificially ventilated dogs under neurolept anesthesia. Adenosine was administered as a continuous infusion in the aorta (n = 3), in the inferior vena cava (n = 3), and after pretreatment with dipyridamole (which inhibits the cellular uptake of adenosine) (n = 4) in a dose sufficient to maintain a mean arterial blood pressure (MABP) level of approximately 50 mmHg. Observations were made before and after 20 min of controlled hypotension. Basal arterial plasma levels of adenosine were in the 10−7 M range (&OV0398; = 0.4 μM). The hemodynamic response was similar in all three settings. Adenosine caused a profound decrease in systemic vascular resistance (SVR) (52%, P < 0.01) and preportal vascular resistance (PPR) (64%, P < 0.01), while hepatic arterial vascular resistance (HAR) increased by 49% (P < 0.05). Cardiac output increased (22%, P < 0.05) through increase of stroke volume (77%, P < 0.01), while heart rate decreased (28%, P < 0.01). Whole-body oxygen uptake decreased (14%, P < 0.01). Portal venous blood flow increased by 28% (P < 0.05), whereas hepatic arterial blood flow decreased by 70% (P < 0.01). In the preportal tissues, oxygen uptake decreased by 21% (P < 0.01). In contrast, hepatic oxygen consumption increased (53%, P < 0.05). Adenosine-induced hypotension was not associated with changes in plasma renin activity or the plasma concentration of norepinephrine. It is concluded that adenosine causes a rapidly induced and easily maintained hypotension and may be a potentially useful agent for controlled hypotension in patients.

Causes and Consequences of Maternal and Fetal Sympathoadrenal Activation During Parturition

Abstract. The sympathoadrenal system is activated in both the mother and fetus during parturition. The fetal plasma catecholamines may reach extremely high levels during deliveries complicated by asphyxia.

Emergency and critical care services in Tanzania: a survey of ten hospitals

BackgroundWhile there is a need for good quality care for patients with serious reversible disease in all countries in the world, Emergency and Critical Care tends to be one of the weakest parts of health systems in low-income countries. We assessed the structure and availability of resources for Emergency and Critical Care in Tanzania in order to identify the priorities for improving care in this neglected specialty.MethodsTen hospitals in four regions of Tanzania were assessed using a structured data collection tool. Quality was evaluated with standards developed from the literature and expert opinion.ResultsImportant deficits were identified in infrastructure, routines and training. Only 30% of the hospitals had an emergency room for adult and paediatric patients. None of the seven district and regional hospitals had a triage area or intensive care unit for adults. Only 40% of the hospitals had formal systems for adult triage and in less than one third were critically ill patients seen by clinicians more than once daily. In 80% of the hospitals there were no staff trained in adult triage or critical care. In contrast, a majority of equipment and drugs necessary for emergency and critical care were available in the hospitals (median 90% and 100% respectively. The referral/private hospitals tended to have a greater overall availability of resources (median 89.7%) than district/regional hospitals (median 70.6).ConclusionsMany of the structures necessary for Emergency and Critical Care are lacking in hospitals in Tanzania. Particular weaknesses are infrastructure, routines and training, whereas the availability of drugs and equipment is generally good. Policies to improve hospital systems for the care of emergency and critically ill patients should be prioritised.

Neurological complications following central neuraxial blockades in obstetrics.

Purpose of review The last few decades have seen an increased use of central neuraxial blockades in obstetric patients. Central blockades provide excellent labour analgesia and safe anaesthesia for caesarean section associated with low incidence of severe complications. Therefore, an increasing number of blockades are also performed in women affected by significant disease. The risks and benefits of central blockades, however, might differ in these patients. This review addresses the risks of neurological complications following central neuraxial blockades in healthy parturients as well as in women affected by significant haemostatic and neurological disease. Recent findings The low risk of complications following central neuraxial blockades applies primarily to women in developed countries. Infectious complications and in particular meningitis still occur, and more frequently so in developing countries. Judicious application of central blockades in women affected by neurological and haemostatic disorders may enhance patient satisfaction without increasing the risk for complications. Summary Estimation of the incidence of neurological complications following central neuraxial blockades to women affected by significant disease on the basis of case reports and small series of patients is impossible. Prospective registration of high-risk patients may increase our knowledge. Application of central neuraxial blockade must follow individual evaluation.

Cerebral blood flow and metabolism during adenosine–induced hypotension in patients undergoing cerebral aneurysm surgery

The effects of adenosine–induced hypotension on cerebral blood flow (CBF), cerebral metabolic rate of oxygen (CMRo2), and cerebral lactate production, together with systemic haemodynamics, were studied in 10 patients undergoing cerebral aneurysm surgery in neurolept anaesthesia with controlled hyperventilation. CBF changes were determined in six of the patients with a retrograde thermodilution technique in the jugular vein. Hypotension was induced with a continuous infusion of adenosine in the superior vena cava. The dose range was 0.06–0.35 mg/kg/min, and this caused a 42% reduction in mean arterial blood pressure (MABP) from 79 × 4 to 46 × 1 raraHg (10.5 × 0.5 to 6.1 × 0.1 kPa) through a profound reduction in systemic vascular resistance (SVR), which amounted to 61%. No significant change occurred in CBF. Whole body AV–difference of oxygen was decreased by 37%, and cerebral AV–difference by 28%, corresponding to reductions in whole body oxygen uptake and CMR02 of 16 and 17%, respectively. Cerebral AV–difference of lactate did not change. In the posthypotensive period MABP was increased by 10%, together with a minor increase in CBF (15%). It is concluded, that adenosine–induced hypotension at MABP levels between 40–50 mmHg (5.3–6.7 kPa) does not affect cerebral oxygenation unfavourably, and may even offer a protective effect by reducing cerebral oxygen demand. The slight CBF increase in the posthypotensive period was probably secondary to an increase in MABP together with a blunted autoregulation, but in no case was this effect considered to be harmful for the patient.

Renin Release during Controlled Hypotension with Sodium Nitroprusside, Nitroglycerin and Adenosine: A Comparative Study in the Dog

The haemodynamic effects of i. v. infusions of sodium nitroprusside (SNP), nitroglycerin (TNG), and adenosine were studied in dogs in parallel with quantitative determinations of plasma renin activity (PRA) by radioimmunoassay. The drugs were given for controlled hypotension, and the mean arterial blood pressure (MABP) was decreased to approximately 50 mmHg (6.7 kPa). Arterial blood samples for PRA were collected at 10‐min intervals. During the last interval the dogs were subjected to haemorrhagic shock. SNP‐induced hypotension could be maintained only with a stepwise increase in infusion rate, from 11.8 to 16.0 μg ⋅ kg‐1 ⋅ min‐1 (P<0.05). TNG could not produce the desired blood pressure level, but gradually increasing doses induced a gradually decreasing MABP (80‐60 mmHg) (10.7–8.0 kPa). During adenosine‐induced hypotension, a perfectly stable blood pressure level was maintained without dose adjustments. Both SNP and TNG induced blood pressure‐dependent increases in PRA, while no changes in PRA were seen during adenosine‐induced hypotension. Nor could haemorrhagic shock, which induced further increases in PRA during SNP‐ and TNG‐induced hypotension, alter PRA during adenosine infusions. We conclude that adenosine differs markedly from conventional hypotensive drugs such as SNP and TNG with respect to stability of action and dose requirements, and that this stability is related to an inhibited increase in renin release.