Use and Outcomes of Peripheral Vasopressors in Early Sepsis-Induced Hypotension Across Michigan Hospitals: A Retrospective Cohort Study

BACKGROUND

Vasopressors traditionally are administered via central access, but newer data suggest that peripheral administration may be safe and may avoid delays and complications associated with central line placement.

RESEARCH QUESTION

How commonly are vasopressors initiated through peripheral IV lines in routine practice? Is vasopressor initiation route associated with in-hospital mortality?

STUDY DESIGN AND METHODS

This retrospective cohort study included adults hospitalized with sepsis (November 2020-September 2022) at 29 hospitals in the Michigan Hospital Medicine Safety Consortium, a Collaborative Quality Initiative sponsored by Blue Cross Blue Shield of Michigan. We assessed route of early vasopressor initiation, factors and outcomes associated with peripheral initiation, and timing of central line placement.

RESULTS

Five hundred ninety-four patients received vasopressors within 6 h of hospital arrival and were included in this study. Peripheral vasopressor initiation was common (400/594 [67.3%]). Patients with peripheral vs central initiation were similar; BMI was the only patient factor associated independently with initiation route (adjusted OR [aOR] of peripheral initiation [per 1-kg/m2 increase], 0.98; 95% CI, 0.97-1.00; P = .015). The specific hospital showed a large impact on initiation route (median OR, 2.19; 95% CI, 1.31-3.07). Compared with central initiation, peripheral initiation was faster (median, 2.5 h vs 2.7 h from hospital arrival; P = .002), but was associated with less initial norepinephrine use (84.3% vs 96.8%; P = .001). We found no independent association between initiation route and in-hospital mortality (32.3% vs 42.2%; aOR, 0.66; 95% CI, 0.39-1.12). No tissue injury from peripheral vasopressors was documented. Of patients with peripheral initiation, 135 of 400 patients (33.8%) never received a central line.

INTERPRETATION

Peripheral vasopressor initiation was common across Michigan hospitals and had practical benefits, including expedited vasopressor administration and avoidance of central line placement in one-third of patients. However, the findings of wide practice variation that was not explained by patient case mix and lower use of first-line norepinephrine with peripheral administration suggest that additional standardization may be needed.

Can subclavian/infraclavicular axillary vein collapsibility index predict spinal anesthesia-induced hypotension in cesarean-section operations?

OBJECTIVE

Spinal anesthesia-induced hypotension (SAIH) is relatively common in pregnant women and has serious maternal and fetal side effects. In patients who are hypovolemic during spinal anesthesia, there may be a significant decrease in blood pressure caused by the decrease in preload. Subclavian vein sonography is a useful method for evaluating preoperative intravascular volume status. This study aimed to evaluate the efficacy of the pre-operative subclavian vein or infraclavicular axillary vein (SCV-AV) collapsibility index for predicting SAIH in cesarean-section (C-section).

PATIENTS AND METHODS

In this prospective observational study, 82 women undergoing elective C-sections were recruited. Sonographic evaluation of SCV-AV was assessed before spinal anesthesia. After spinal anesthesia, changes in blood pressure were noted. The main outcome was the association between the SCV-AV measurements (diameter and collapsibility index) and SAIH.

RESULTS

Hypotension developed in 53 (64%) patients after spinal anesthesia. The collapsibility index of the SCV-AV during spontaneous breathing and deep inspirium was not a significant predictor of a decrease in mean blood pressure (MBP) after spinal anesthesia (p<0.979, p<0.380).

CONCLUSIONS

It was found that the SCV-AV collapsibility index is not a predictor of SAIH in pregnant women undergoing elective C-sections.

Sevoflurane-induced hypotension causes cognitive dysfunction and hippocampal inflammation in mice

Sevoflurane commonly adopted for anesthetic in clinical practice, however, its influences on cerebral blood flow and cognitive function remain controversial. Herein, the sevoflurane-induced hypotension on arterial blood pressure, cerebral blood flow, cognitive function, and hippocampal inflammation was investigated in mice. A significant decrease in arterial blood pressure and cerebral blood flow was indicated by the sevoflurane anesthesia treatment. Moreover, sevoflurane-induced hypotension was associated with the impaired cognitive function and the increased levels of NLRP3 inflammasome activation and oxidative stress in hippocampus. These findings suggest that sevoflurane-induced hypotension may lead to the cognitive dysfunction and hippocampal inflammation.

Controlled hypotension during neuraxial anesthesia is not associated with increased odds of in-hospital common severe medical complications in patients undergoing elective primary total hip arthroplasty - A retrospective case control study

Introduction

The use of controlled hypotension during neuraxial anesthesia for joint arthroplasty is controversial. We conducted a large institutional database analysis to assess common in-hospital complications and mortality of patients undergoing primary total hip arthroplasty (THA) under controlled hypotension and neuraxial anesthesia.

Methods

We conducted a large retrospective case control study of 11,292 patients who underwent primary THA using neuraxial anesthesia between March 2016 and May 2019 in a single institution devoted to musculoskeletal care. The degree and duration of various mean arterial pressure (MAP) thresholds were analyzed for adjusted odds ratios with composite common severe complications (in-hospital myocardial infarction, stroke, and/or acute kidney injury) as the primary outcome.

Results

Sixty-eight patients developed common severe complications (0.60%). Patients with complications were older (median age 75.6 vs 64.0 years) and had a higher American Society of Anesthesiologists (ASA) classification (45.6% vs 17.6% ASA III). The duration of hypotension at various MAP thresholds (45 to 70 mm Hg) was not associated with increasing odds of common severe medical complications.

Conclusions

Controlled hypotension (ranging from 45 to 70 mmHg) for a moderate duration during neuraxial anesthesia was not associated with increased odds of common severe complications (myocardial infarction, stroke, and/or acute kidney injury) among patients receiving neuraxial anesthesia for elective THA.

Comparison of the effect of propofol and desflurane on S-100β and GFAP levels during controlled hypotension for functional endoscopic sinus surgery: A randomized controlled trial

BACKGROUND

Although surgical field visualization is important in functional endoscopic sinus surgery (FESS), the complications associated with controlled hypotension for surgery should be considered. Intraoperative hypotension is associated with postoperative stroke, leading to subsequent hypoxia with potential neurologic injury. We investigated the effect of propofol and desflurane anesthesia on S-100β and glial fibrillary acidic protein (GFAP) levels which are early biomarkers for cerebral ischemic change during controlled hypotension for FESS.

METHODS

For controlled hypotension during FESS, anesthesia was maintained with propofol/remifentanil in propofol group (n = 30) and with desflurane/remifentanil in desflurane group (n = 30). For S-100β and GFAP assay, blood samples were taken at base, 20 and 60 minutes after achieving the target range of mean arterial pressure, and at 60 minutes after surgery.

RESULTS

The base levels of S-100β were 98.04 ± 78.57 and 112.61 ± 66.38 pg/mL in the propofol and desflurane groups, respectively. The base levels of GFAP were 0.997 ± 0.486 and 0.898 ± 0.472 ng/mL in the propofol and desflurane groups, respectively. The S-100β and GFAP levels were significantly increased in the study period compared to the base levels in both groups (P ≤ .001). There was no significant difference at each time point between the 2 groups.

CONCLUSION

On comparing the effects of propofol and desflurane anesthesia for controlled hypotension on the levels of S-100β and GFAP, we noted that there was no significant difference in S-100β and GFAP levels between the 2 study groups.

CLINICAL TRIAL REGISTRATION

Available at: http://cris.nih.go.kr, KCT0002698.

Controlled hypotension during middle ear surgery: hemodynamic effects of remifentanil vs nitroglycerin

INTRODUCTION

Controlled hypotension is a well-known technique used by anesthesiologists to limit intraoperative bleeding in patients undergoing middle ear surgery and improve visibility of the surgical field. Nitroglycerin and remifentanil are among the drugs used to induce controlled hypotension.The aim of our study was to compare the hemodynamic effects of remifentanil and nitroglycerin in this patient population.

METHODS

All consecutive patients who underwent middle ear surgery between January and December 2016, at the University Hospital Vittorio Emanuele in Catania were included in a retrospective study. Patients who were given nitroglycerin to induce controlled hypotension were compared to those given remifentanil. The following parameters were measured systolic and diastolic blood pressure, heart rate, peripheral (capillary) oxygen saturation, and fraction of expired carbon dioxide. A mean arterial pressure of 50-70 mmHg was considered optimal.

RESULTS

Thirty patients who underwent stapedioplasty and tympanoplasty, 25 men and 5 women,with a mean age of 43 years (range 32-58 years) were included in the study. Fifteen patients had received nitroglycerin (group A) and 15 patients remifentanil (group B). The target blood pressure was reached in all patients and no significant difference was found between the groups with regard to the level of systolic and diastolic blood pressure, heart rate, peripheral (capillary) oxygen saturation, and fraction of expired carbon dioxide. However the heart rate of 2 younger patients in group A rose to > 100 bpm after the administration of nitroglycerin.

CONCLUSION

Both remifentanil and nitroglycerin are effective in inducing controlled hypotension. In younger patients administration of nitroglycerin is associated with an increase in heart rate.

KEY WORDS

Controlled hypotension, Middle ear surgery, Nitroglycerin, Remifentanil.

Hypotensive epidural anaesthesia in patients with preoperative renal dysfunction undergoing total hip replacement

BACKGROUND

Hypotensive anaesthesia does not impair renal function after surgery in normal patients but there are no reports of hypotensive anaesthesia in patients with chronic renal dysfunction (CRD).

METHODS

From a database of 1893 consecutive patients undergoing total hip replacement (THR) under hypotensive epidural anaesthesia (HEA) from 1999 to 2004, 54 patients were identified with CRD (preoperative serum creatinine > or =124 micromol litre(-1)). Fifty matched pairs were identified for patients with normal renal function who have hypertension (n=50) or no hypertension (n=50). Changes in serum creatinine and blood urea nitrogen (BUN) were recorded daily for 3 days. Acute renal failure was defined as an increase in serum creatinine of 44 micromol litre(-1).

RESULTS

The mean duration of hypotension (MAP<55 mm Hg) was 94 min (range 35-305 min). The mean age was 71 yr. All patients with a creatinine level of 124 micromol litre(-1) had a creatinine clearance of <40 ml min(-1) 1.73 m(-2) (range: 13-56). Patients with CRD received more crystalloid during surgery (1755 ml) than the other two groups (1435 ml) (P<0.001). Otherwise, all three groups were similar. No patients developed evidence of acute renal dysfunction immediately after or by 24 h after surgery. Three patients with CRD had an increase in creatinine of >44 micromol litre(-1) at 48 and 72 h after surgery in the setting of volume depletion (acute blood loss in two patients and early ileus in one). Renal function subsequently improved.

CONCLUSION

HEA, per se, when carefully managed does not appear to predispose patients with CRD to acute renal failure after THR.

Moderne Anästhesieverfahren in der endonasalen Nasennebenhöhlenchirurgie

BACKGROUND

Optimal vision is essential for successful endonasal sinus surgery. Beside topical vasoconstriction general anaesthesia can contribute to reduce intraoperative bleeding.

METHODS AND RESULTS

For many years deliberate hypotension was used to prevent intraoperative bleeding. The intentional reduction of systolic blood pressure to 50-60 mm Hg was achieved by the use of Sodium Nitroprusside alone or in combination with other vasoactive agents. However, intraoperative bleeding is not affected by this technique unless the systolic blood pressure falls below 60 mm Hg which can cause serious side effects for the patient. Recently, there is growing evidence that not only systolic blood pressure but also a low heart rate (< 60 beats per minute) can minimize surgical bleeding. With the introduction of total intravenous anaesthesia (TIVA) by the use of Propofol and Remifentanyl an anaesthetic technique has been established which fulfils the haemodynamic requirements in endonasal sinus surgery in many regards. The inhibiting effects on the cardiovascular system of these drugs alone can lead to a reduced bleeding. TIVA allows the reduction of the systolic blood pressure to 60 mm Hg as well as the heart rate below 60 beats per minute. If necessary it can be supported by vasoactive agents of which betablockers have a theoretical advantage.

CONCLUSION

For general anaesthesia in endonasal sinus surgery Sodium Nitroprusside is no longer recommended. Instead a TIVA using Propofol and Remifentanil should be used.

Hypotension as an isolated factor may not be sufficient to provoke hearing impairment

OBJECTIVE

We investigated the possible role of hypotension and related autonomic phenomena in the pathogenic mechanism of sudden sensorineural hearing loss.

METHODS

Forty-nine patients belonging to the ASA I-II classes of anaesthesiological risk and submitted to a non-otological surgical procedure were examined. Each operation was performed under general anaesthesia by controlled hypotension technique. Hearing function of the patients was evaluated before and after surgery by means of a pure tone audiometry recorded by the same clinician with the same instrument.

RESULTS

No cases of bilateral hearing worsening were recorded after surgery.

CONCLUSIONS

An induced and controlled steady hypotension under general anaesthesia did not affect the hearing function of any of the patients. It may be supposed, therefore, that an adverse effect on the cochlear oxygenation is more likely to be caused by the sympathetic changes induced by a consistent decrease of blood pressure rather than to hypotension itself.

Hypotension-induced loss of intraoperative monitoring data during surgical correction of scheuermann kyphosis: a case report

STUDY DESIGN

Presentation of a case report of Scheuermann kyphosis surgical correction.

OBJECTIVE

To describe a scenario where both neurogenic mixed evoked potentials and somatosensory-evoked potentials were lost due solely to hypotension before any correction of a kyphotic spinal deformity was performed.

SUMMARY OF BACKGROUND DATA

Multimodality intraoperative neurophysiologic monitoring of the spinal cord has become widely utilized during surgical correction of scoliotic and kyphotic deformities. Most spinal surgeries also benefit from a state of hypotension to minimize blood loss, but unchecked and persistent hypotension may lead to inadequate perfusion to the spinal cord, resulting in spinal cord dysfunction noted by diminution of neuromonitoring data.

METHODS

An 18-year-old boy with a 95 degrees Scheuermann kyphosis underwent a posterior spinal fusion for correction of his deformity. Intraoperative neurophysiologic monitoring consisting of neurogenic mixed evoked potentials and somatosensory-evoked potentials were performed throughout surgery.

RESULTS

After placement of segmental pedicle screw fixation points and multiple osteotomies, before any instrumented correction of the deformity, all lower extremity neuromonitoring data were acutely lost. The surgeon was immediately warned of the data loss, with the mean arterial pressure noted to be 50 mm Hg. The mean arterial pressure was raised with the use of epinephrine bolus and dopamine infusion. Subsequently, all lower extremity neuromonitoring data returned. A Stagnara wake-up test was performed, which the patient passed, and the surgical correction was performed with his pressure maintained on a dopamine infusion. He awakened without neurologic deficits and had an uneventful recovery.

CONCLUSIONS

Although a state of mild hypotension may be beneficial to limit blood loss during spinal deformity corrective surgery, acute and/or prolonged hypotension may jeopardize spinal cord vascularity and should be avoided especially during surgical treatment of high-risk deformities such as kyphosis. Early warning by multimodality physiologic neuromonitoring appears to be a useful method to alert surgeons of the potentially devastating problem of hypotension-induced spinal cord dysfunction and allows immediate corrective actions.

Strategies for Managing Decreased Motor Evoked Potential Signals While Distracting the Spine During Correction of Scoliosis

Surgical correction of kyphoscoliosis may result in spinal cord injury and neurologic deficits. Monitoring somatosensory evoked potentials (SSEPs) and transcranial motor evoked potentials (MEPs) intraoperatively may allow for early detection and reversal of spinal cord injury. Controlled hypotension and isovolemic hemodilution are often used during these cases to reduce blood loss and transfusion. However, these physiologic parameters may affect the quality of SSEP and MEP signals. Acute reduction or loss of MEP or SSEP signals during spinal distraction presents a crisis for the operative team: should distraction be immediately relieved? The authors describe three patients who showed a decrease in evoked potential signals under hypotensive, hemodiluted conditions at the stage of spinal distraction. Each case illustrates a different strategy for successful management of these patients.

[Controlled hypotension in transthoracic esophageal resection]

PURPOSE

This study was performed in order to evaluate effectiveness of controlled hypotension decreasing blood lose in transthoracic esophageal resection.

PATIENTS AND METHODS

Thirty-six patients were enrolled in this randomized study. The patients were divided in to two groups. We used controlled hypotension induced by thoracic epidural anaesthesia for the group T (n=18/50%). For the group K (n=18/50%) we used only endotracheal anesthesia. The median arterial pressure was about 50 mmHg in group T and 80-110 mmHg in group K. We investigated intra-operative and post-operative blood loss, the average operating time, opioid and inhaled anesthetic use and stay in intensive care unite.

RESULTS

The intra-operative blood loss was less for 45.7% in group T than in group K but post-operative blood loss was the same in groups. The mean operation time was 14.2% shorter in group T. We used 80% less fentanyl and 43% less inhaled anesthetics in group T. The stay in intensive care unit was 2.6 days in group T and 3.9 in group K. There were no significant complications caused by controlled hypotension.

CONCLUSION

We conclude that controlled hypotension is an effective method to decrease blood loos and blood transfusions. It creates better conditions for surgery and reduces operation time. There were no serious cardiac, neurological and renal intra-operative and post-operative complications resulting from the use of controlled hypotension.

Avascular necrosis of the femoral head after surgery for lumbar spinal stenosis

STUDY DESIGN

Case report.

OBJECTIVE

To report a previously undescribed complication of lumbar spinal surgery under prolonged hypotensive anesthesia.

BACKGROUND DATA

Avascular necrosis of bone most commonly affects the femoral head. The etiology of the condition is understood in only 75% of cases. There have been no prior reports of this condition following lumbar spine surgery carried out under hypotensive anesthetic.

METHODS

Notes review, clinical examination, plain radiographs, and magnetic resonance imaging diagnosed three patients who developed avascular necrosis of the femoral heads (five joints in total) after surgery for lumbar spinal stenosis. All three were treated with total hip replacement (five joints), and the diagnosis of avascular necrosis was confirmed in two by histopathological examination.

RESULTS

All three patients have recovered full mobility following hip replacement surgery. None had any residual symptoms of lumbar spinal stenosis or hip disease, and none of them had shown any clinical evidence of avascular necrosis in any other bone.

CONCLUSIONS

The development of avascular necrosis of the femoral heads following surgery for spinal stenosis may be due to hypotensive anesthesia, prone positioning on a Montreal mattress, or a combination of the two. Careful intraoperative positioning may reduce the risk of this occurring after spinal surgery. However, close postoperative surveillance and a high index of suspicion of worsening hip pathology in patients who appear to mobilize poorly after lumbar spinal surgery may be the only method of early detection and treatment for this condition.

The influence of hyperoxic ventilation during sodium nitroprusside-induced hypotension on skeletal muscle tissue oxygen tension

BACKGROUND

Increasing inspired oxygen concentrations might provide a simple and effective intervention to increase oxygen tension in tissues during controlled hypotension. To test this hypothesis, the influence of hyperoxic ventilation (100% O2) on skeletal muscle oxygen partial pressure (Ptio2) in patients receiving sodium nitroprusside-induced controlled hypotension was studied.

METHODS

Forty-two patients undergoing radical prostatectomy were prospectively studied and randomly divided into three groups as follows: (1) Controlled hypotension induced by sodium nitroprusside (mean arterial blood pressure, 50 mmHg) and hyperoxic ventilation (CH-100%; n = 14); (2) controlled hypotension and ventilation with 50% O2 in nitrous oxide (CH-50%; n = 14); and (3) standard normotensive anesthesia with 50% O2 in nitrous oxide (control; n = 14). Ptio2 values were measured continuously in all patients using implantable polarographic microprobes. Arterial blood gases and lactate concentrations were analyzed in 30-min intervals.

RESULTS

Surgical blood loss and transfusion requirements were significantly reduced in both groups receiving hypotensive anesthesia. During surgery, arterial partial pressure of oxy-gen and arterial oxygen content were significantly higher in patients of the CH-100% group. Baseline values of Ptio2 were comparable between the groups (CH-50%: 25.0 +/- 0.7 mmHg; CH-100%: 25.2 +/- 0.2 mmHg; control: 24.5 +/- 0.2 mmHg). After a transient increase in Ptio2 in the CH-100% group during normotension, Ptio2 values returned to baseline and remained unchanged in the control group. Ptio2 decreased significantly during the hypotensive period in the CH-50% group. The lowest mean Ptio2 values were 15.0 +/- 4.1 mmHg in the CH-50% group, 24.2 +/- 4.9 mmHg in the CH-100% group, and 23.5 +/- 3.8 mmHg in the control group. There were no significant changes in lactate plasma concentrations in any group throughout the study period.

CONCLUSIONS

Hyperoxic ventilation improved skeletal muscle tissue oxygenation during sodium nitroprusside-induced hypotension. This improved local tissue oxygenation seems to be most likely due to an increase in convective oxygen transport and the attenuation of hyperoxemia-induced arteriolar vasoconstriction by sodium nitroprusside.

Profound hypotension: ethical considerations

The use of profound induced hypotension to provide better operating conditions for surgery is long established. However, it is a controversial technique and it may be argued that it is inappropriate in modern anaesthetic practice. A currently used technique is reviewed against the benchmark of a lawsuit concerning profound hypotension.

Adverse effects of limited hypotensive anesthesia on the outcome of patients with subarachnoid hemorrhage

OBJECT

This study was aimed at clarifying the effect of intraoperative hypotensive anesthesia on the outcome of early surgery in patients with subarachnoid hemorrhage (SAH) caused by saccular cerebral aneurysms. Other factors were also screened for possible effects on the outcome.

METHODS

Hospital charts in 84 consecutive patients with SAH who underwent aneurysm clipping by Day 4 were examined. Possible factors affecting the outcome were analyzed using multiple logistic regression with the dichotomous Glasgow Outcome Scale score as the outcome variable. The relationship between the intraoperative hypotension and the occurrence and severity of vasospasm was studied using both single- and multivariate analyses.

CONCLUSIONS

Intraoperative hypotension had a significantly adverse effect on the outcome of SAH. Hypotension was also related to more frequent and severe manifestations of vasospasm. A long-lasting effect of brain retraction is possibly the cause of this phenomenon. The data contained in this study preclude the use of intraoperative hypotension even in a limited form.

Heart rate and blood pressure power spectral analysis during calcium channel blocker induced hypotension

PURPOSE

To observe heart rate (HRV) and blood pressure variability (BPV) as indices of neurocirculatory responses to induced hypotension with diltiazem and/or nicardipine for hip surgery.

METHODS

Thirty-six ASA I-II patients received diltiazem (group D, n = 12), nicardipine (group N, n = 12) or combination of diltiazem/nicardipine (group DN, n = 12). The intensity of HRV and BPV, was determined by spectral analysis of HRV and BPV before anesthesia (T0), just before induced hypotension (T1), and at 10 and 30 min after the start of induced hypotension (T2 and T3, respectively). The logarithmic HRV and BPV were integrated: sympathetic and parasympathetic mediated low frequency area (0.06-0.1 Hz, LF), parasympathetic related high frequency area (0.15-0.4 Hz, HF) and total frequency area (0.01-0.4 Hz). Blood loss was assessed by weighing gauzes and measuring suction.

RESULTS

Group DN had less blood loss (466 +/- 46 ml, mean +/- SEM) than group D (733 +/- 100 ml, P < 0.05). Diltiazem (11.4 +/- 0.9 microg x kg(-1) x min(-1)), and combination of diltiazem (0.25 +/- 0.01 mg x kg(-1)) and nicardipine (5.9 +/- 0.9 microg x kg(-1) x min(-1)) decreased LF-HRV at T2 and T3 (P < 0.05 vs T0 and T1), while nicardipine (8.1 +/- 0.8 microg x kg(-1) x min(-1)) showed increase in LF-HRV at T2 (P < 0.05 vs T1). HF-HRV unchanged through hypotension except for a decrease in group N at T3 (P < 0.05 vs T1). There were no increases in HF-BPV, and LF-BPV, except for a diltiazem induced decrease in LF-BPV at T3 (P < 0.05 vs T0 and T1).

CONCLUSION

Group D and group DN can be used for deliberate hypotension without an increase in sympathetically mediated LF-HRV.

Unexplained visual loss after lumbar spinal fusion

Two cases of visual loss after spinal fusion surgery are described. In both cases, surgery was lengthy, the patient's head was placed in a dependent position, and hemodilution and deliberate hypotension were combined. One patient was achondroplastic, the other obese. Possible risk factors associated with ischemic optic neuropathy after anesthesia and surgery are discussed.

[Effect of controlled hypotension on cerebral oxygen delivery]

The margin of safety for controlled hypotension is still unclear especially in the central nervous system (CNS) which is one of the most sensitive organs to hypoxia and ischemia. Recently, cerebral optical spectroscopy in the infrared light range was developed as a useful tool which makes it possible to monitor cerebral oxygenation (rSO2) non-invasively and continuously during anesthesia. Resulting rSO2 mainly reflects oxygen extracts by cerebral tissue and then indicates cerebral oxygen delivery. We examined the limitation of controlled hypotension in the brain in 12 patients by monitoring rSO2 during anesthesia. rSO2 under room air breathing (control value as normal physiological condition) was 67 +/- 3% (mean +/- SEM). It significantly increased by 5.6 +/- 0.8% under 100% oxygen breathing, but decreased near to the control value under sevoflurane anesthesia (FIO2 1.0). During moderate controlled hypotension (70% of normal blood pressure) by prostaglandin E1 under sevoflurane anesthesia (FIO2 1.0). rSO2 remained at control value, indicating that cerebral oxygen delivery was still sufficiently maintained. However rSO2 decreased significantly by 9.0 +/- 1.1% in same controlled hypotension condition under FIO2 0.4. This decrease in rSO2 could be potentially harmful for CNS although any post-operative neurological disorder was not observed in our cases. We conclude that cerebral oxygen delivery may be insufficient even in the moderate controlled hypotension, and thus higher FIO2 is recommended in such procedures.

Combined effects of prolonged prostaglandin E1-induced hypotension and haemodilution on human hepatic function

Combined effects of prolonged prostaglandin E1 (PGE1)-induced hypotension and haemodilution on hepatic function were studied in 30 patients undergoing hip surgery. The patients were randomly allocated to one of three groups; those in group A (n = 10) were subjected to controlled hypotension alone, those in group B (n = 10) to haemodilution alone and those in group C (n = 10) to both controlled hypotension and haemodilution. Haemodilution in groups B and C was produced by withdrawing approximately 1000 mL of blood and replacing it with the same amount of dextran solution, and final haematocrit values were 21 or 22%. Controlled hypotension in groups A and C was induced with PGE1 to maintain mean arterial blood pressure at 55 mmHg for 180 min. Measurements included arterial ketone body ratio (AKBR, aceto-acetate/3-hydroxybutyrate) and clinical hepatic function parameters. AKBR and biological hepatic function tests showed no change throughout the time course in groups A and B. In group C, AKBR showed a significant decrease at 120 min (-40%) and at 180 min (-49%) after the start of hypotension and at 60 min (-32%) after recovery of normotension, and SGOT, SGPT, LDH and total bilirubin showed significant increases after operation. The results suggest that a prolonged combination of more than 120 min of PGE1-induced hypotension and moderate haemodilution would cause impairment of hepatic function.

Effect of permissive hypotension in continuous uncontrolled intra-abdominal hemorrhage

OBJECTIVE

To determine the effects of aggressive fluid administration vs permissive hypotension on survival, blood loss, and hemodynamics in a model of uncontrolled hemorrhage in which bleeding has been shown to be continuous.

METHODS

In this porcine model, 10 animals were bled through a flow-monitored shunt placed between the femoral artery and the peritoneal cavity. The animals received either no fluid (n = 5) or 80 mL/kg lactated Ringer's solution (n = 5) during a resuscitation phase between 10 and 20 minutes postinjury, followed by a 40-minute evaluation phase. Arterial pressures, cardiac output (CO), and hemorrhage rate were measured. Survival and blood loss were calculated outcome measures.

RESULTS

The difference in survival between the animals left hypotensive (40%) and those receiving normotensive resuscitation (20%) was not significant (p = 0.49). In the animals receiving fluid resuscitation, mean arterial pressure (MAP) and CO increased during the resuscitative phase, but all the animals suffered the same pattern of hemodynamic deterioration in the evaluation phase. Rate of hemorrhage during the resuscitative phase was 20 +/- 5 mL/min in the animals not receiving fluid and 56 +/- 9 mL/min in the animals receiving fluids. Total blood loss was subsequently 20 mL/kg greater in the animals receiving fluids than in the animals without fluid resuscitation.

CONCLUSIONS

In this model of continuous uncontrolled hemorrhage, the difference in survival between the animals left hypotensive and the animals receiving fluid resuscitation was not statistically significant. Increases in MAP and CO with fluid resuscitation were transient and were offset by larger volumes of blood loss. In contrast to the aortotomy model (where thrombosis is likely and hypotensive resuscitation has proven beneficial), this model suggests that in continuous bleeding avoiding fluid resuscitation has a much smaller effect on outcome. Much of the benefit from hypotensive resuscitation may depend on having an injury that can stop bleeding.

[Loss of brain stem auditory evoked potential waves I and II during controlled hypotension]

For surgical removal of a malignant choroid melanoma, it is necessary to reduce systolic blood pressure to around 50-60 mmHg in order to prevent choroidal haemorrhages. However, blood pressure reduction is associated with the risk of cerebral ischaemia. We report a patient with a malignant choroid melanoma in whom waves I and II of the brainstem auditory evoked potentials (BAEP) disappeared during surgery under controlled arterial hypotension and hypothermia (31.1 degrees C). The waves could be recorded again immediately after the mean arterial pressure was increased from 48 to 77 mmHg. The oesophageal temperature had dropped by 0.3 degrees C at this time. The 2-channel electroencephalogram (EEG) showed no irregularities during this time period. A bilateral, reversible, apparently blood-pressure-dependent loss of waves I and II during arterial hypotension despite a normal EEG has to our knowledge not been previously described in the literature. The isolated loss of waves I and II with maintenance of waves III, IV, and V is unusual. The literature contains reports of acoustic neurinoma patients in whom only wave V could be recorded. This is regarded as an indication of continued impulse conduction despite the loss of waves I to IV. Others have observed a patient with temporary and reversible loss of BAEP wave I due to vasospasm of the internal auditory artery that apparently occurred during or shortly after manipulation of the internal auditory meatus. Assuming anatomic peculiarities in the blood supply to the generators of the BAEP waves, a stenosis of the basilar artery could be considered as the cause of the bilateral reversible loss of waves I and II. Another potential source could be induced hypothermia, but this does not seem very likely because the patient's temperature was 0.3 degrees C lower at the return of the waves than at their loss.

[Does controlled hypotension with nitroprusside affect platelet function?]

Induced hypotension is an accepted technique to reduce intraoperative blood loss and thereby ensures satisfactory operating conditions, especially in microscopic interventions. Sodium nitroprusside (NP), which is often used for induced hypotension, was reported to inhibit platelet aggregation in vitro. Impairment of platelet function implies a higher bleeding risk, which would make the use of NP for induced hypotension questionable. METHODS. With the approval of the local ethics committee, 30 patients scheduled for nasal septum operations were included in this randomised study. For induction of anaesthesia 2 mg vecuronium, 0.1 mg fentanyl, 0.2 mg/kg etomidate, and 1 mg/kg succinylcholine were used. After tracheal intubation the patients inhaled 1.0-1.5 vol.% isoflurane in a gas mixture containing 66% nitrous oxide in oxygen. Fifteen patients received an i.v. infusion of NP for 60 min. The concentrations chosen produced a decrease of mean arterial blood pressure to 50 mm Hg. Blood samples were taken before induction of anaesthesia; after induction of anaesthesia but before beginning of the operation; and 60 min after the beginning of the operation. This time-point coincided with the end of NP administration in the study group. The last blood sample was drawn the morning after the operation. Platelet function was determined in platelet-rich plasma by a turbidometric method after adding 22 mumol/l epinephrine to induce aggregation. The spontaneous aggregation was measured in whole blood using impedance aggregometry. Data within one group were analysed using analysis of variance. Student's t-test for unpaired values served to compare data between the two groups. RESULTS. Biometric data in the two groups were comparable. The blood loss in the control group [265 (190-410) ml] significantly exceeded (P < 0.05) that in the hypotensive group [125 (75-210) ml]. No significant changes in platelet function were found throughout the study period in the patients treated with NP. In the control patients the epinephrine-induced aggregation increased significantly from 53.1 +/- 5.3% before anaesthesia to 72.1 +/- 3.3% the morning after the intervention. The spontaneous aggregation showed a significant increase from 0.718 +/- 0.338 Ohm/h before anaesthesia to 2.164 +/- 0.442 Ohm/h 60 min after the beginning of the operation. The value on the 1st postoperative day (2.266 +/- 0.448 Ohm/h) was also significantly higher than the basal value. CONCLUSIONS. In contradiction to in vitro studies using high concentrations of NP, we could not find a decrease in platelet aggregation due to hypotensive anaesthesia with this drug in vivo. In the control group a significant increase in platelet aggregation was observed, which was probably counteracted in the hypotensive patients by the interaction of NP with cyclic guanosine monophosphate (c-GMP). NP augments the intracellular concentration of c-GMP, which is known to decrease platelet aggregation.

Induced hypotension in a smoker

An episode of hypoxia following the use of propranolol and sodium nitroprusside to induce hypotension in a 50-year-old male patient undergoing craniotomy for frontal meningioma is described. The importance of proper preoperative screening of lung function and intraoperative monitoring of blood gases is highlighted.

[Hypotension controlled with ATP in orthopedic surgery: incidence of atrio-ventricular conduction disorders]

Adenosine triphosphate (ATP) has been effectively used for induced hypotension in man. Atrio-Ventricular (A-V) conduction disturbances have been observed after adenosine bolus injection and during continuous ATP i.v. infusion. The present perspective investigation was designed to determine the incidence of A-V conduction disturbances during ATP-induced hypotension. Thirty-five normotensive healthy patients (ASA I-II) with no preoperative therapy were subjected to the same anesthetic technique for orthopedic surgery. Premedication consisted of diazepam and atropine. Anesthesia was induced with thiopental and fentanyl followed by atracurium for intubation. The maintenance anesthesia consisted of isoflurane (1.5% inspired)-N2O (60%) in oxygen and incremental doses of fentanyl; the lungs were mechanically ventilated. Dipyridamole (0.15 mg kg-1) was given 15 min prior to ATP-infusion. ATP was administered by an infusion pump at a dosage of 0.025-0.05 mg kg-1 min-1. The ECG was recorded with a Mingograph 34 tape-recorder using 3 pregelled electrodes positioned to give an effective V6 lead pattern. MAP was reduced by 25% and HR increased by 6%. The mean duration of ATP-induced hypotension was 75 min +/- 50 and the mean dose of ATP infused was 200 mg +/- 161. Six patients (17%) showed A-V conduction disturbances. There was a I A-V Block (AVB) in 2 cases, a II AVB in 2 cases and a III AVB in 2 cases. In every case the arrhythmia disappeared spontaneously or after ATP-infusion suspension.(ABSTRACT TRUNCATED AT 250 WORDS)

Combined effects of compression and hypotension on nerve root function. A clinical case

Previous animal experiments suggest that mild compression may increase susceptibility of nerve roots to the effects of hypotension. The authors report the case of a patient with an unstable L2 burst fracture whose motor skills and senses were intact. During fracture reduction and spinal distraction, sensory-evoked potentials were recorded from the epidural space after right and left femoral and tibial nerve stimulation. Induced hypotension was used during the surgery. All responses were normal at the outset of the surgery. With hypotension, a marked drop in the amplitude of the right femoral evoked potential amplitude occurred; left femoral and both tibial responses remained unchanged. Evoked potential changes were reversible with reversal of hypotension. Postoperatively, the patient was neurologically intact. Further analysis revealed a significant correlation between the right femoral evoked potential amplitude and systolic blood pressure (r = 0.63, P < 0.005), whereas amplitudes of the other responses were not significantly correlated with systolic blood pressure. This report provides clinical evidence to support the hypothesis that hypotension and local compression exert additive adverse effects on nerve root function.

Change in cerebral blood flow velocity pattern during induced hypotension: a non-invasive indicator of increased intracranial pressure?

A neurologically intact patient underwent spinal instrumentation under hypotensive anaesthesia 10 days after a mild closed head injury. Transcranial Doppler monitoring of the right middle cerebral artery revealed an abnormal flow pattern, suggesting increased intracranial pressure, impaired autoregulation, or both. Patients with a mild head injury may have altered intracranial haemodynamics and the time course of recovery from these changes is unknown.

Isoflurane prevents EEG depression during trimetaphan-induced hypotension in man

We have studied the EEG analysed with the cerebral function analysing monitor (CFAM) during trimetaphan (TMP)-induced hypotension to a mean arterial pressure (MAP) of 40 mm Hg in 20 normocapnic patients anaesthetized with either 1% end-tidal isoflurane or 0.5% halothane. During the acute reduction in MAP, the average reduction in mean EEG amplitude with halothane was 14%, two patients showing short periods of EEG suppression; the decline in EEG amplitude correlated with declining MAP in four patients. In contrast, the average reduction in mean EEG amplitude with isoflurane was only 0.3% and there were neither periods of suppression nor any correlation between EEG amplitude and MAP. No significant changes in EEG frequency occurred in either group. Isoflurane prevented EEG amplitude depression during TMP-induced hypotension.

Intra-operative monitoring by means of somatosensory evoked potentials during cerebral aneurysms surgery

During cerebral aneurysms surgery, brain tissue may suffer for global or local ischemia due to deliberate hypotension and surgical manoeuvres. Somatosensory evoked potentials (SEPs) can detect functional derangements consequent to hypoxia, before a permanent brain damage is produced. Forty two patients, undergoing cerebral aneurysms surgery for treatment of SAH, were evaluated intraoperatively with SEP recordings. It has been stressed that no permanent neurological damage is to be expected if the absolute value of Central Conduction Time (CCT) does not exceed 9.5 ms for 10 min at least and the cortical waves are visible throughout the whole procedure. SEP changes are strictly related with MAP decrease and surgical handlings.

[Changes in renal function induced by anesthesia]

The rate of urine formation and its composition are influenced by the different drugs used during surgery. Anaesthetics act on renal function, not only directly, but also by producing changes in cardiovascular function and in neuroendocrine activity. Many factors may be incriminated: lowered blood pressure and cardiac output, increased sympathetic outflow (renal nerve stimulation and increased plasma catecholamines), increased release of renin, angiotensin and vasopressin. The effects of anaesthetics on the kidney go beyond a simple change in basal haemodynamics and include, for some drugs, an alteration in the ability for the kidney to autoregulate its blood flow and glomerular filtration rate. Studies on toad bladders showed a decrease in transport of water, sodium and organic anions. But, in fact, renal effects of anaesthetics in man and animals depend on the species, the anaesthetic and the method used to study the effect. Most barbiturates and inhalational anaesthetics tend to decrease renal blood flow (RBF) and glomerular filtration rate (GFR). These trends are gradually reversed during recovery. The effects of ketamine and diazepam are not clearly defined. Morphine and fentanyl decrease urine flow and GFR, whilst RBF increases or decreases, depending on whether a direct or indirect measurement technique was used. Muscle relaxants have little effect on renal function. Spinal and epidural anaesthesia only slightly decrease GFR and RBF in proportion to the decrease in mean arterial pressure. Obviously, the preexisting intravascular volume and the quantity of intravenous fluids given strongly influence the renal response to spinal and epidural anaesthesia. Some studies have shown that urine flow rate, creatinine clearance, urinary sodium excretion and RBF are reduced during mechanical ventilation with positive end-expiratory pressure. Surgery itself influences renal function by inducing alterations in prerenal haemodynamics. Operative stress leads to an increase in circulating catecholamines and angiotensin. Significant fluid shifts, excessive blood loss and redistribution of a third space may lead to a prerenal oliguric state, increasing secretion of vasopressin. Acute renal failure (ARF) is a frequently lethal complication of critical surgical illness, due to a variety of factors which interfere with glomerular filtration and tubular reabsorption, such as renal hypoperfusion or nephrotoxic insults. In fact, the initiating aggression ultimately culminates in the development of one or more of the maintenance factors (decreased tubular function, tubular obstruction, decreased GFR and RBF) that reduce urine flow and osmolar excretion. Good management during the perioperative period tends to minimize the risk of developing ARF.

Adverse effects on the brain in connection with isoflurane-induced hypotensive anaesthesia

As a marker of brain cell injury, adenylate kinase (AK) was measured in cerebrospinal fluid (CSF) in 10 patients given anaesthesia with isoflurane-induced hypotension for corrective surgery of dentofacial deformities. Nine out of 10 patients displayed a marked increase in CSF-AK postoperatively compared with preoperative values. The postoperative mean value displayed a 400% increase compared to the corresponding preoperative value. This difference was statistically significant (P = 0.001). The rise in CSF-AK was most probably the result of an enhanced efflux of AK into CSF subsequent to a presumed hypoxic injury to brain cells.

Induction of equine postanesthetic myositis after halothane-induced hypotension

Wick catheters were used to measure intracompartmental pressures of the extensor carpi radialis muscles and long heads of the triceps brachii muscles of 7 horses maintained under halothane anesthesia during controlled ventilation. Horses were positioned in left lateral recumbency on a water bed for 4 hours. Using a crossover design, 6 of the 7 horses were subjected to normotensive and hypotensive anesthesia on separate occasions. Hypotension was achieved by increasing the inspired halothane concentration. Hematologic and biochemical measurements were determined at designated intervals before, during, and for 7 days after each anesthetic episode. Under hypotensive conditions, 2 horses developed severe generalized myositis and were euthanatized. Three of the 5 other horses developed swelling of the downside masseter muscle, 4 demonstrated mild extensor deficits of the downside forelimb, and 1 had a severe extensor deficit of the uppermost hind limb. As a group, the hypotensive horses had markedly increased activities of serum enzymes (creatine kinase, aspartate transaminase, and blood lactate) and abnormalities in calcium-phosphorus homeostasis. Lameness or enzyme alterations were not observed in normotensive horses. Although the intracompartmental pressure values were markedly increased in the muscle bellies of the compressed limbs of all horses, there was a statistically significant difference in intracompartmental pressures between the downside or compressed muscle compartments of the extensor carpi radialis of hypotensive and normotensive horses. High concentrations of halothane may predispose anesthetized horses to postanesthetic myositis, even when protective padding is used. Intracompartmental muscle pressure, as measured by the wick catheter, may not be a reliable predictor of equine postanesthetic lameness.

Hypotensive anesthesia and blood loss

Controlled hypotension reduces blood loss during defined major surgical procedures, which in turn will minimize transfusion needs and thereby the risks of transmission of infectious diseases. There is no evidence that hypotension below 8 kPa (60 mmHg) (MAP) is associated with better blood-sparing effects than a more moderate hypotension, but it will probably increase the risk of cardiovascular complications. Therefore, controlled hypotension, being a sophisticated technique, requires handling by an experienced anesthetist well aware of contraindications and the need for adequate monitoring for prevention of tissue ischemia. Large randomized and prospective studies are still warranted, especially for further evaluation of the risk-benefit with controlled hypotension.

The effect of trimethaphan-induced hypotension on canine spinal cord blood flow. Measurement at different cord levels using radiolabelled microspheres

Controlled hypotension which is used during scoliosis surgery to improve operating conditions and minimize transfusion requirements may decrease spinal cord blood flow (SCBF). Previous studies using hydrogen washout, an invasive technique, have shown that trimethaphan-induced hypotension is associated with a decrease in SCBF, whereas hypotension induced with sodium nitroprusside or nitroglycerin is not. To determine whether the decrease seen with trimethaphan represented a generalized rather than regional spinal cord phenomenon, SCBF was measured at three separate cord levels (T2-3, 7-8, L2-3) using a noninvasive radionuclide-labelled microsphere technique. When the mean arterial pressure was reduced by 50%, SCBF decreased 35 to 45% at all levels of the cord examined, and remained at this reduced level during the period of hypotension. The results confirm that trimethaphan-induced hypotension is associated with a significant reduction in SCBF and that this occurs throughout the spinal cord during the period of hypotension.

The stress response to induced hypotension for cerebral aneurysm surgery: a comparison of two hypotensive techniques

Plasma epinephrine (PE), plasma norepinephrine (PNE), plasma renin activity (PRA), mean arterial pressure (MAP) and heart rate (HR) were measured before, during and after induced hypotension in two groups of patients undergoing cerebral aneurysm surgery. In Group I isoflurane was used to maintain anaesthesia and induce hypotension. Mean PE fell significantly during hypotension and remained reduced after hypotension, mean PNE remained unchanged, while mean PRA rose slightly but not significantly during hypotension, falling again after hypotension. In Group II halothane was used to maintain anaesthesia and sodium nitroprusside to induce hypotension. During anaesthesia and surgical stimulation PNE and PRA were significantly greater compared to Group I. Mean PE, PNE and PRA all rose during hypotension and remained elevated after hypotension. The rise in PNE and PRA was statistically significant. After hypotension the MAP in Group II was significantly higher when compared to Group I. There was no significant change in HR during the study in either group. In conclusion, isoflurane-induced hypotension with isoflurane anaesthesia unlike sodium nitroprusside-induced hypotension with halothane anaesthesia attenuated the stress response.

The effect of induced hypotension and tissue trauma on renal function in scoliosis surgery

The surgical correction of scoliosis in adolescents involves considerable trauma to bone and muscle which, together with hypotensive anaesthesia, might be expected to compromise renal function. Our recent observation of acute renal failure in two such patients prompted a prospective study of renal function following 52 operations in 43 patients. Despite hypotension, blood loss, muscle damage and evidence of fat embolism, renal function was unaltered in all patients, and there was no impairment of spinal cord function. Careful attention was paid to the maintenance of circulating volume which is essential to protect renal perfusion.