The timing of intravenous crystalloid administration and incidence of cardiovascular side effects during spinal anesthesia: the results from a randomized controlled trial

Comparative Dose–Response Study on the Infusion of Norepinephrine Combined with Crystalloid Coload versus Colloid Coload for Preventing Hypotension During Spinal Anesthesia for Cesarean Delivery

Background

Although the optimal infusion dose of norepinephrine combined with crystalloid coload for preventing spinal anesthesia-induced hypotension (SAIH) for cesarean delivery has been established, the infusion regimen of norepinephrine combined with colloid coload has not been fully quantified. The objective of this study was to compare and determine the median effective dose (ED₅₀) and 90% effective dose (ED₉₀) of norepinephrine infusion combined with crystalloid coload versus colloid coload for preventing SAIH during cesarean delivery.

Methods

Two hundred parturients were randomly assigned to receive norepinephrine infusion at 0.02, 0.04, 0.06, 0.08, or 0.10 µg/kg/min in combination with 10 mL/kg crystalloid coload or colloid coload to prevent SAIH. The study period was defined as the interval from the commencement of intrathecal injection to delivery of the neonate. The primary outcome was non-occurrence of hypotension, defined as systolic blood pressure (SBP) less than 80% of the baseline before delivery. The ED₅₀ and ED₉₀ of norepinephrine infusion dose were determined using probit regression analysis. By calculating the 95% confidence intervals (CIs) of relative median potency to determine whether the prophylactic infusion of norepinephrine requirement was different between the two groups.

Results

The derived ED₅₀ and ED₉₀ of norepinephrine infusion combined with crystalloid coload were 0.030 (95% CIs 0.020 to 0.038) and 0.097 (95% CIs 0.072 to 0.157) µg/kg/min, respectively. The ED₅₀ and ED₉₀ of norepinephrine infusion combined with colloid coload were 0.021 (95% CIs 0.013 to 0.029) and 0.070 (95% CIs 0.053 to 0.107) µg/kg/min, respectively. The estimate of relative median potency for norepinephrine between the two groups was 1.37 (95% CIs 0.94 to 2.23).

Conclusion

Under the conditions of this study, 10 mL/kg colloid coload reduced the dose of prophylactic norepinephrine infusion by approximately 30% in parturients during spinal anesthesia for cesarean delivery compared with the crystalloid coload.

Correlation between Weight of the Baby and the Level of Sensory Blockade in Spinal Anaesthesia for Caesarean Section: An Observational Study

Background

The spread of local anaesthetics during spinal anaesthesia is affected by various factors and can be unpredictable especially in parturients undergoing caesarean section. Factors like abdominal girth, symphysis fundal height etc have to studied to know their impact on level of sensory blockade. We hypothesized a study to find any correlation between weight of the baby and the level of sensory blockade.

Methods

46 parturients posted for elective caesarean section belonging to American Society of Anaesthesiologists (ASA) physical status 1 and 2 were included in the study. Maternal height and weight were noted down before entering operation theatre. All patients were instituted subarachnoid block with 2 cc of 0.5% of hyperbaric bupivacaine in sitting position. Level of sensory blockade was assessed with pin prick along midline of the patient every min till 5^th minute and 5 minutes till 15^th minute. The birth weight of baby was recorded soon after delivery.

Results

The weight of the baby and height of the mother were correlated with the sensory blockade of T4. The number of babies weighing more than 3.5 kgs were 3 in our study out of which 2 babies were associated with maximum sensory blockade at 15^th minute. It amounts to 66.7% when compared with 14.7% in babies weighing 2.5 to 3.5 kgs which is suggestive of significance ('P' value of 0.093).

Conclusion

There is no statistically significant correlation between weight of the baby and the level of sensory blockade.

[Recent standards in management of obstetric anesthesia]

The following article contains information not only for the clinical working anaesthesiologist, but also for other specialists involved in obstetric affairs. Besides a synopsis of a German translation of the current "Practice Guidelines for Obstetric Anaesthesia 2016" [1], written by the American Society of Anesthesiologists, the authors provide personal information regarding major topics of obstetric anaesthesia including pre-anaesthesia patient evaluation, equipment and staff at the delivery room, use of general anaesthesia, peridural analgesia, spinal anaesthesia, combined spinal-epidural anaesthesia, single shot spinal anaesthesia, and programmed intermittent epidural bolus.

Prevention of hypotension induced by combined spinal epidural anesthesia using continuous infusion of vasopressin: A randomized trial

Background:

Central neuraxial blockade (CNB) is an established technique of providing anesthesia for surgeries of the lower limb and abdomen. Hypotension is the most common side effect of CNB. It was hypothesized that by supplementing the initial burst of vasopressin following hypovolemia, hypotension following combined spinal epidural anesthesia (CSEA) could be avoided.

Materials and Methods:

A total of 122 patients undergoing lower limb and abdomen surgeries were included in the study, with 61 patients randomized into two groups - I and II. Patients in Group I received infusion of normal saline as soon as CSEA was applied. When systolic blood pressure (SBP) decreased to <90 mmHg, they received a 6 mg bolus of mephentermine to counteract hypotension. Patients in Group II received a continuous infusion of vasopressin as soon as CSEA was applied. If despite maximum dose of vasopressin, SBP dropped to < 90 mmHg, then intravenous mephentermine was administered to counteract hypotension. Hemodynamic parameters and side effects were noted.

Results:

Level of block attained in both groups was comparable in terms of dermatomal height. The mean SBP and mean arterial pressure values of Group I were significantly lower than in Group II in the initial 14 min. Diastolic BP was also significantly lower in Group I. Heart rate was found to be lower in Group II, especially after 30 min (P < 0.05).

Conclusion:

Maintaining plasma levels of the physiological burst of vasopressin helps to avoid hypotension following neuraxial blockade. Continuous infusion of vasopressin at 1–3 U/h can prevent hypotension following neuraxial blockade.

Co-loading or pre-loading for prevention of hypotension after spinal anaesthesia! a therapeutic dilemma

Neuraxial blockade such as spinal anaesthesia can cause severe hypotension due to pharmacological sympathectomy resulting in potential deleterious consequences for the patient. Prevention of this spinal anaesthesia induced hypotension is of utmost importance especially in pregnant population as the life of mother as well as fetus is at risk. Several techniques and methodologies have been adopted for the prevention of this neuraxial hypotension with varying degree of success. The administration of intravenous fluids to optimize the blood volume during sympathectomy has been the most popular and widely used as the first line of therapy among these techniques. The intravenous fluids can be used both before and during the administration of spinal anaesthesia, the techniques appropriately named as pre-loading and co-loading respectively. Numerous research studies and available literary evidence suggests that both of these techniques can be equally effective in prevention of hypotension. The use of colloids has been observed to be more effective for pre-loading due to their longer half-life in the intravascular compartment. However, it has also been suggested that no technique is efficient in preventing the hypotension alone and has to be coupled with judicious use of vasopressors.

Prevention of altered hemodynamics after spinal anesthesia: A comparison of volume preloading with tetrastarch, succinylated gelatin and ringer lactate solution for the patients undergoing lower segment caesarean section

Background:

Spinal anesthesia has replaced general anesthesia in obstetric practice. Hemodynamic instability is a common, but preventable complication of spinal anesthesia. Preloading the circulation with intravenous fluids is considered a safe and effective method of preventing hypotension following spinal anesthesia. We had conducted a study to compare the hemodynamic stability after volume preloading with either Ringer's lactate (RL) or tetrastarch hydroxyethyl starch (HES) or succinylated gelatin (SG) in the patients undergoing cesarean section under spinal anesthesia.

Materials and Methods:

It was a prospective, double-blinded and randomized controlled study. Ninety six ASA-I healthy, nonlaboring parturients were randomly divided in 3 groups HES, SG, RL (n = 32 each) and received 10 ml/kg HES 130/0.4; 10 ml/kg SG (4% modified fluid gelatin) and 20 ml/kg RL respectively prior to SA scheduled for cesarean section. Heart rate, blood pressure (BP), oxygen saturation was measured.

Results:

The fall in systolic blood pressure (SBP) (<100 mm Hg) noted among 5 (15.63%), 12 (37.5%) and 14 (43.75%) parturients in groups HES, SG, RL respectively. Vasopressor (phenylephrine) was used to treat hypotension when SBP <90 mm Hg. Both the results and APGAR scores were comparable in all the groups. Lower preloading volume and less intra-operative vasopressor requirement was noted in HES group for maintaining BP though it has no clinical significance.

Conclusion:

RL which is cheap, physiological and widely available crystalloid can preload effectively and maintain hemodynamic stability well in cesarean section and any remnant hypotension can easily be manageable with vasopressor.

Subarachnoid block for caesarean section in severe preeclampsia

Pregnancy-induced hypertension constitutes a major cause of morbidity and mortality in developing nations and it complicates about 6–8% of pregnancies. Severe preeclampsia poses a dilemma for the anesthesiologist especially in emergency situations where caesarean deliveries are planned for uninvestigated or partially investigated parturients. This article is aimed to review the literature with regards to the type of anesthesia for such situations. A thorough search of literature was conducted on PubMed, EMBASE, and Google to retrieve the articles. Studies on parturients with severe preeclampsia, undergoing caesarean section, were included in this article. There is growing evidence to support the use of subarachnoid block in such situations when the platelet counts are >80,000 mm^-3. Better hemodynamic stability with the use of low-dose local anesthetic along with additives and better neonatal outcomes has been found with the use of subarachnoid block when compared to general anesthesia.

The kinetics of Ringer's solution in young and elderly patients during induction of general anesthesia with propofol and epidural anesthesia with ropivacaine

BACKGROUND

Different fluid regimens are often adopted for elderly patients, but it is not known whether they handle infused fluids differently during the induction of anesthesia than young patients.

METHODS

Mean arterial pressure (MAP), plasma dilution (based on hemoglobin) and volume kinetics were assessed during an intravenous (i.v.) infusion of 1000 ml of lactated Ringer's solution over exactly 60 min in 29 patients given general anesthesia with propofol (15 < 65 years of age, and 14 > 65 years old) and in 16 patients receiving lumbar epidural anesthesia with titrated doses of ropivacaine (7 patients < 65 years of age and 9 > 65 years old).

RESULTS

General anesthesia caused a greater decrease in MAP than epidural anesthesia (mean 15% vs. 9%; P < 0.001) and was followed by a more pronounced plasma dilution (30% vs. 18%; P < 0.001); the maximum values reaching 50%. The fluid-induced hemodilution increased after the onset of anesthesia. The distribution rate constant (k(t)), which governs the preference for infused fluid to retain the plasma, was significantly reduced, with the lowest values being reached during general anesthesia (P < 0.002). However, only the reduction of MAP, and not the patient's age group or the type of anesthesia per se, had a statistically significant influence on k(t) after the induction.

CONCLUSION

Induction of anesthesia greatly increases fluid-induced hemodilution, the magnitude of which can be expressed as an acute reduction of the distribution rate constant for infused fluid. The post-induction value of this parameter was closely associated with MAP but not with the patient's age.

Bolus injection of Ringer's solution and dextran 1 kDa during induction of spinal anesthesia

BACKGROUND

Arterial hypotension following induction of spinal anesthesia is difficult to prevent with infusion fluids. In a randomized, unblinded and controlled study we evaluated whether a rapid fluid administration planned according to volume kinetic analysis is followed by a more stable blood pressure.

METHODS

Spinal anesthesia was induced in 75 surgical patients, using one of three different fluid regimens: intravenous 'bolus injection' of 5 ml kg(-1) of Ringer's acetate over 3 min, 2 ml kg(-1) of low-molecular weight (1 kDa) dextran over 3 min, or a constant-rate infusion of 15 ml kg(-1) of Ringer's acetate over 40 min (controls). The kinetics of the fluid was studied in five patients in each group and also in eight volunteers.

RESULTS

The decrease in mean arterial pressure averaged 28%, 27% and 26%, respectively, and was fully developed 16 min after the induction. The height of the block, but not the fluid programme, correlated with the hypotension. Nausea or near-fainting associated with marked hypotension or bradycardia was recorded in none, five (20%) and two (8%) of the patients, respectively. Both bolus injections were followed by translocation of fluid from the peripheral tissues to the bloodstream, which maintained the plasma dilution at about 10% for at least 30 min until surgery began.

CONCLUSION

A brisk infusion of Ringer's solution or dextran 1 kDa over 3 min was followed by the same decrease in arterial pressure as a longer and 3-5-times larger infusion of Ringer's solution over 40 min during induction of spinal anesthesia.